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Permeability and elastic properties assessment of alumina nanofiber (ANF) cementitious composites under simulated wellbore cyclic pressure
Abstract
Highly dispersed Alumina Nanofibers (ANF’s) were utilized in oil well cement class ‘‘H” to investigate effects of ANF’s on the cement’s mechanical and microstructural properties under simulated wellbore conditions. Cement composites consisted of a reference (Ref) sample containing no ANF’s and three additional formulations with 0.1%, 0.2%, and 0.3% ANF’s by weight of cement (BWOC) incorporated in cement formulations with various common additives. The provided producing liquid dispersion methodology was assessed using a Transmission Electron Microscope (TEM) with each composite formulation undergoing permeability and elastic property testing under simulated cyclic confining wellbore pressures. The compressive strength was also measured along with a microstructural assessment. The microstructural assessment consisted of measuring the formation of hydration products using an X-ray diffractogram (XRD) and thermogravimetric analyzer (TGA). The results indicate that 0.1% of ANF provides the greatest increase in mechanical properties and possesses the lowest permeability through all pressure cycles.
Additionally, the amount of Calcium Silicate Hydrate (C-S-H) and Degree of Hydration (DOH) was maximized for 0.1% ANF compared to other composite formulations.
... Traditionally, oil-well cement (OWC) is used to repair wellbore integrity issues and leakage pathways developed during well completion and post-completion operations [3][4][5][6], and cement pastes. In wellbore construction operations for waste-disposal wells, oil and gas wells, geothermal wells, and CO 2 injection wells, the OWC method has been utilized over the past decades in protecting the casings from corrosion and providing mechanical support, hydraulic seal, and adequate zonal isolation for the wellborecasing or inter-casing annular spaces [1,7]. In a wellbore environment, the existence of delamination [8,9], micro-and macro-fractures [10][11][12], and permitted flow pathways [13] can substantially compromise the wellbore integrity. ...
... The results showed that there were no discernable direct size or shape effects (for the range of specimen sizes tested) on the reliability or validity of the UCS measurements. Another study investigated the effects of highly dispersed alumina nanofibers (ANF) in class ''H" oilwell cement systems on the cement paste's mechanical and microstructural properties under simulated wellbore conditions [7]. The results showed that 0.1 % of the ANF's yielded the highest increase in mechanical properties with the lowest permeability. ...
Compromised integrity of cementitious materials can lead to potential geo-hazards such as detrimental fluid flow to the wellbore (borehole), potential leakage of underground stored fluids, contamination of water aquifers, and other issues that could impact environmental sustainability during underground construction operations. The mechanical integrity of wellbore cementitious materials is critical to prevent wellbore failure and leakages, and thus, it is imperative to understand and predict the integrity of oilwell cement (OWC) and microbial-induced calcite precipitation (MICP) to maintain wellbore integrity and ensure zonal isolation at depth. Here, we investigated the mechanical integrity of two cementitious materials (MICP and OWC), and assessed their potential for plugging leakages around the wellbore. Further, we applied Machine Learning (ML) models to upscale and predict near-wellbore mechanical integrity at macro-scale by adopting two ML algorithms, Artificial Neural Network (ANN) and Random Forest (RF), using 100 datasets (containing 100 observations). Fractured portions of rock specimens were treated with MICP and OWC, respectively, and their resultant mechanical integrity (unconfined compressive strength, UCS; fracture toughness, Ks) were evaluated using experimental mechanical tests and ML models. The experimental results showed that although OWC (average UCS = 97 MPa, Ks = 4.3 MPa·√m) has higher mechanical integrity over MICP (average UCS = 86 MPa, Ks = 3.6 MPa·√m), the MICP showed an edge over OWC in sealing microfractures and micro-leakage pathways. Also, the OWC can provide a greater near-wellbore seal than MICP for casing-cement or cement-formation delamination with relatively greater mechanical integrity. The results show that the degree of correlation between the mechanical integrity obtained from lab tests and the ML predictions is high. The best ML algorithm to predict the macro-scale mechanical integrity of a MICP-cemented specimen is the RF model (R2 for UCS = 0.9738 and Ks = 0.9988; MAE for UCS = 1.04 MPa and Ks = 0.02 MPa·√m). Similarly, for OWC-cemented specimen, the best ML algorithm to predict their macro-scale mechanical integrity is the RF model (R2 for UCS = 0.9984 and Ks = 0.9996; MAE for UCS = 0.5 MPa and Ks = 0.01 MPa·√m). This study provides insights into the potential of MICP and OWC as near-wellbore cementitious materials and the applicability of ML model for evaluating and predicting the mechanical integrity of cementitious materials used in near-wellbore to achieve efficient geo-hazard mitigation and environmental protection in engineering and underground operations.
... Fibrous additives of various kinds and sizes have been shown to enhance the fracture toughness and crack growth resistance of cementitious materials (Banthia and Nandakumar, 2003;Metaxas et al., 2011) by bonding to and bridging the gaps between cement crystals formed during hydration. Cementitious materials containing optimal amounts of well bonded fiber can also exhibit improved tensile strength (McElroy et al., 2019(McElroy et al., , 2021, better flexural strength (Yoo et al., 2013(Yoo et al., , 2014, and enhanced elastic behavior (McElroy et al., 2020). The PPF cement used in this study contains polypropylene microfibers with surface deposited nano silica particles for improved bond to cement. ...
... To enhance the mechanical properties of the expansive cement, Alumina nanofibers (ANF) were added to the cement formulation. ANF has been shown to improve tensile strength, compressive strength, and elastic behavior of cement (McElroy et al., 2019(McElroy et al., , 2020. The ANF used in this study was supplied as a 1402 kg/m 3 pre-dispersed solution of 10% by weight aluminum oxide nano fibers. ...
Well drilling, completions, stimulation, and enhanced oil recovery operations induce downhole conditions that may negatively impact the integrity of the annular seal and consequently hinder zonal isolation. Thus, the ability to accurately quantify the evolution of the annular seal in response to the prevailing downhole environment is critical for the optimal design of the annular barrier for the life of a well. Thanks to increased accessibility and recent advancements in computing power and techniques, X-ray computed tomography has gained popularity as a non-destructive analysis method in materials science and geomechanics due to its ability to reveal details about the interior volume of objects in real-time without physical disassembly.
Therefore, in this study, a novel apparatus is presented for the construction of a lab-scale wellbore, with the purpose of simulating downhole processes while simultaneously monitoring wellbore elements of interest in real-time via x-ray computed tomography. The benefits of this novel setup for wellbore integrity are demonstrated via applications to two test cases: the mechanical evolution of annular cement under stresses induced by cyclic water injection as a function of the mechanical properties of the cased and cemented wellbore system; the evaluation of nano magnesium oxide performance as an additive for autogenous shrinkage mitigation in annular cement.
The results of the studies presented illustrate the benefits of combining x-ray computed tomography with lab-scale wellbore process simulations. The results of the cyclic water injection study suggest that residual strain in the cement is the major factor in annular seal degradation under cyclic downhole pressure fluctuations. Nano magnesium oxide is also shown to be very effective in preventing autogenous shrinkage of Class H cement. However, more study is required to characterize its effectiveness in a wider range of cement formulations. Finally, suggestions are offered on how to improve the experimental procedure presented while future potential applications of the apparatus are discussed.
... The study reported a significant impact of ANF on compressive strength, while other properties (i.e., rheological properties and thickening time) had a lesser impact. Additionally, the investigation by McElroy et al. (2020) reported the effects of ANF's on cement mechanical and microstructural properties. Morphological characterisation of ANF showed that efficient dispersion is required for the optimum result because the inefficient dispersion may lead to nanofibre agglomeration. ...
... Similarly, nano-alumina fibers are also cost-effective as compared to CNT. The cost of ANF is US$1.17/g, which is considerably lower than other NMs such as CNT, which can cost upwards of US$750/g (McElroy et al., 2020). ...
Well construction operation is a crucial process that relies on the success of cementing job. Cementing failure could lead to catastrophic aftermaths and huge capital loss to the exploration and production (E&P) companies. In recent years, nanotechnology application in the petroleum industry has increased due to favorable results and compatibility with different E&P activities. Particularly for well-cementing operations, nanomaterials have been evaluated to understand the mechanism, performance, and economic viability. In this review, a brief introduction of nanotechnology, including the preparation and properties of nanomaterials is illustrated. Applications of nanoparticles in the oil and gas industry are also depicted to highlight the potential uses of nanomaterials in cementing. The effects of nanomaterials on different cement properties like density, viscosity, fluid loss, thickening time, and mechanical properties are discussed. The mechanisms of alteration of cement properties upon the addition of nanomaterials are depicted. Nanomaterials such as SiO2, MgO, TiO2, Fe2O3, Al2O3, and graphene-oxide have been used as potential cement additives for the improvement of cement properties. This review also sheds light on critical facts like optimal concentration and size of nanomaterials; inclusion of binary and ternary system-nanomaterials in cementing. Furthermore, it discusses the recent advancements, prospects, challenges, and economic viability of nanomaterials in well cementing. However, a lack of scientific rigour in the application of these nanomaterials has been observed. It is expected that the current review will help the newcomers in this research field to gain a quick idea about the development of the field and its way forward.
... van der Waals forces) and a very high surface area-to-volume ratio, nanoparticles tend to agglomerate in the solution. Nanoparticle agglomeration essentially leads to irregularities in the microstructure of the cement during the hydration process, unreacted pockets creating weak zones throughout the cement, and a reduction in cement mechanical properties (Jafariesfad et al., 2017b;Wang, 2017;McElroy et al., 2019McElroy et al., , 2020. Thus, the efficacy of the pre-dispersed nanoparticle solutions was assessed by transmission electron microscope (TEM) images. ...
This study demonstrates the use of Artificial Neural Network (ANN) modeling techniques to estimate the Unconfined Compressive Strength (UCS) of lightweight oil and gas well cement. At varied simulated wellbore temperatures, 172 cement samples were reinforced with variable doses of strength-enhancing ceramic cenospheres. An Isothermal water bath was used to cure the cement samples for 24 hours and the samples were crushed using a compressive load frame. Multiple samples comprising the same properties were crushed to confirm the consistency of the dataset. The model was trained with 70% of the data set, validated with 15%, and tested with the remaining 15%. The proposed ANN model has four layers: a three-neuron input layer, twenty-five neurons in the first hidden layer, five neurons in the second hidden layer, and a single-neuron output layer. The two hidden layer ANN architecture was determined to be the optimum configuration to prevent overfitting the data. After many rounds of hyperparameter tuning, optimum performance was achieved, and the model parameters were retained and utilized. With a Root Mean Squared Error (RMSE) score of 144 psi, coefficient of determination (R2) exceeding 0.9 and accuracy of approximately 90%, the ANN produced a highly accurate model and signified a good model fit when evaluated on the test set. Similarly strong results were observed on the validation set indicating that the model generalized well to unseen data. These results demonstrate that the ANN approach is adept at producing high fidelity models for UCS prediction of lightweight cement for use in Oil and Gas well cementing operations. This paper discusses a new UCS prediction method as an alternative to rigorous experimental testing for lightweight cement systems where achieving optimum strength is highly important for the proper zonal isolation of the wellbore.
1. INTRODUCTION
Global energy demand has been and is projected to increase steadily in the coming decades. To match this demand, the oil and gas industry continuously expands its capabilities by operating in extreme and challenging environments (Canbaz, et al., 2021). Since many of the easy-to-reach reservoirs are maturing, it is not uncommon to drill multi-mile wells, both vertically and horizontally, to maximize reservoir contact (Anya, 2018). Many of these new wells are drilled into high-pressure and high-temperature zones (Arbad & Teodoriu, 2020), which require differing cement properties from those traditionally used.
... In the present study, BFO NPs proved an efficient strength enhancer for oilwell cement slurry at low concentrations. Previously, nanosilica (Ershadi et al. 2011;Khalil et al. 2020;Bayanak et al. 2020), nano-TiO 2 (Maagi et al. 2019), alumina nanofibers (McElroy et al. 2020), and nano-Fe 2 O 3 Mohammed 2015a, 2017) have all been shown to enhance the compressive strength similarly. Hence, it can be used as an additive in the cement slurry to improve the compressive strength of the cement matrix. ...
Oilwell cement ensures wellbore stability and isolates zones while bearing casing load and formation pressure. Its properties, crucial in extreme downhole conditions, include compressive strength, fluid loss resistance, and durability. In the present work, bismuth ferrite nanoparticles (BFO NPs) were synthesized using the sol-gel method and used as an additive in oilwell cement. The synthesized BFO NPs were characterized using Fourier transform infrared (FTIR), X-ray diffraction (XRD), field-emission scanning electron microscope (FESEM), and dynamic light scattering (DLS) techniques to analyze the functional groups, crystalline structure, morphological features, and hydrodynamic size distribution. Tests at 70°C and 2,000 psi revealed that 1% by weight of cement (BWOC) BFO NPs increased compressive strength by ~136% and reduced fluid loss to ~64% compared with base cement. It can be conjectured that the exposed facets of BFO NPs containing oxygen act as nucleating sites that promote the ordering of the silicate tetrahedra, thereby increasing the strength and crystallinity and reducing the water loss. The experimental results confirm that the BFO NPs can improve the properties of oilwell cement slurry at high-pressure, high-temperature (HPHT) conditions. This research underscores the potential of BFO NPs as sustainable additives for optimizing oilwell cement performance under challenging HPHT conditions, paving the way for advancements in sustainable construction practices.
... δ-alumina nanofibers (ANFs) are a relatively new reinforcement nanomaterial functionalized by aluminum, zirconium, nickel, and copper oxides [39]. In various industries, ANFs have drawn particular attention as a low-cost 1-D nanofiber with high strength, stability at 1100 °C, low thermal conductivity, and corrosion resistance [38]. ...
There is general agreement that burning fossil fuels and growing atmospheric greenhouse gas emissions ramp up global warming. Renewable energy is a realistic alternative to meet the world’s energy needs while minimizing emissions associated with fossil fuels. The emergence of hydrogen as a dependable source of clean energy over the globe may be aided by underground hydrogen storage in depleted hydrocarbon reservoirs. Establishing the practicality of underground hydrogen storage in the subsurface depends on well integrity. Cement slurries containing nanoparticles have proved helpful in downhole conditions where neat cement slurries lead to complications. In this study, the stability, rheological, and mechanical properties along with the permeability of highly dispersed alumina nanofibers (ANF) (1-D) are compared to nanoalumina particles (0-D) to evaluate how the change in the structure of the nanomaterials affects the various properties of class H cement. The rheology, stability, and compressive strength tests of the cement reinforced with nanomaterials were conducted after hydrogen exposure for 8 min at 0.68 MPa. The results demonstrate that nanoalumina particles were more effective than ANF in increasing the compressive and tensile strength of the cement after 24 h of curing at 65.5 °C and 27.57 MPa. However, there was no significant change in the rheology, stability, permeability, modulus of elasticity, Poisson’s ratio, and thickening time of the cement slurries. The main objective of this study is to determine the usefulness of including nanomaterials in cementing operations as a wellbore integrity perspective in future geological storage applications.
... To investigate the entire microstructure of concrete, electrochemical impedance spectroscopy could be used [22,23] Zirconium oxide nanofibers are a relatively new and promising material for use in enhancing the mechanical and durability properties of concrete. Research has shown that the addition of zirconium oxide nanofibers to concrete can significantly improve the compressive and flexural strength of the material [24,25]. The nanofibers have a high aspect ratio, which means they are extremely thin and have a large surface area. ...
In this study, zirconium oxide nanofiber with a mean diameter of 100 nm was added to concrete at various concentrations as a cement replacement. Various tests, including compressive strength, splitting tensile strength, flexural strength, and electrical resistance tests, as well as a rapid chloride penetration test, were performed on specimens containing zirconium oxide nanofibers for the concrete assessment, and the results were compared to those obtained from control specimens that did not contain nanofibers. The results showed that adding zirconium oxide nanofibers at 135 gr/m³ of concrete yielded a 28-day compressive strength equal to 44.62 MPa, which exhibits a 20.40% increase in strength with respect to the specimen that lacked nanofibers. The flexural strength and splitting tensile strength tests at 28 days of age and in the presence of 135 gr/m³ mentioned nanofibers were increased by 22.28 and 33.47%, respectively, in comparison to the control specimens. Moreover, revealed that at 28 days of age, in the specimens containing 270 gr/m³ zirconium oxide nanofibers, the migration coefficient of chloride ion was reduced by 29.86%, and its electrical resistance was increased by 68.33%. These findings highlight the potential of nanofibers as a promising solution for enhancing the strength and performance of concrete structures.
... This behavior is applied to the prevention of early cracking in cementitious materials (Polat et al., 2015) and could be useful for microannulus prevention in cemented wellbores. In general, cementitious materials containing fibrous additives have demonstrated improvements in fracture toughness and crack growth resistance (Banthia and Nandakumar, 2003;Metaxas et al., 2011), while optimal concentrations of certain fibrous additives in cements, including ANF, have also been shown to improve tensile strength (McElroy et al., 2019(McElroy et al., , 2021, improve flexural strength (Yoo et al., 2013(Yoo et al., , 2014, and enhance elastic behavior (McElroy et al., 2020). The ANF used in this study was supplied as a 1402 kg/m 3 pre-dispersed solution of 10% by weight aluminum oxide nano fibers. ...
Cyclic bottomhole pressure fluctuation is very prevalent in modern well construction and enhanced petroleum recovery applications and poses a great challenge to annular seal integrity and successful zonal isolation, even in cases where the cement seal exhibits excellent initial quality. Thus, annular sealants must be designed to mitigate or minimize the deleterious effects of cyclic pressure fluctuations on the annular seal. Optimal cement designs for this purpose require a proper understanding of damage modes and mechanisms associated with a cyclic pressure regime, as well as the impact of the cement mechanical integrity evolution on the leakage of the cemented annulus. Using four cement formulations with distinct mechanical and microstructural properties, we investigated the mechanical integrity evolution and leakage characteristics of cemented pipe specimens subjected to confinement pressure fluctuations. Via microscopic inspection of the cement/pipe interface after pressure cycling and permeability measurements during pressure cycling, we attempted to correlate cement properties with leakage and suggest a recommendation for optimal cement design and successful zonal isolation in wellbores subjected to cyclic pressure. Test data indicate that under high enough pressure variation, interfacial cracking at the cement pipe interface is unavoidable and the cement seal's ability to maintain zonal isolation will be dependent on the microstructural morphology and microscale mechanical resilience of the cement formulation. Stiffer conventional cements also appear to have a higher chance of leakage through non-interfacial fractures than their more flexible counterparts. Latex cements show great promise for effective zonal isolation under cyclic bottomhole pressure conditions and should be studied in more detail.
... The impact of CO 2 and N 2 on various oil industry branches has been studied extensively. (Elturki, M. et al., 2020a;Fakher, S. et al., 2019a;Fakher, S. et al., 2019b;McElroy et al., 2020;Fakher, S. et al., 2019c;Fakher, S. et al., 2019d;Fakher, S. et al., 2019e;Elturki, M. et al., 2020b;Fakher, S. et al., 2019f). ...
Production from unconventional reservoirs using hydraulic fractured wells has recently gained much attention due to its ability to increase recovery to high percentages. The placement of proppant in fractures plays a significant role in conductivity of fractures and well productivity. Here, we aimed to elucidate some basic concepts of the technique using FracPro simulator. FracPro and hydraulic fracturing consist of many design parameters that effect the results of the stimulation process. Of the many parameters that exist, three were focused on in this paper: proppant transport, the use of carbon dioxide (CO2) foam fracturing fluid, and the use of low specific weight versus higher specific weight. FracPro was also used to simulate the results of using a low specific gravity value of 1.9, a medium value of 2.7, and a high value of 3.5. The concentration of CO2 was also varied in each condition; concentrations of 30, 50, and 70% were used. After running investigating these scenarios, some unexpected results were obtained. Notably, a lower specific gravity should produce a longer effective proppant length; however, our data indicates shows the opposite.
... Positive results obtained from the study cited above have led to have a deeper understanding on the role of each single nano-constituent, the present investigation focusing on alumina nano-fibres as a quite new product in the field of concrete and advanced cement based materials technology. Alumina nano-fibres, when added at less than 1% by weight of cement, have been shown to have beneficial effects on the compressive strength [25][26][27][28], when employed, e.g. in HPFRCC type mixes, with either polyethylene or poly-vinyl-alcohol fibre reinforcement, they also guaranteed enhanced flexural strength and deformation capacity. Use into oil well slurries has been also documented, where, besides moderate improvement also in splitting tensile strength, the stability of the rheological performance upon their incorporation was also studied. ...
The effects of alumina nano-fibres are investigated in this paper on the mechanical performance of Ultra High Performance Fibre Reinforced Cementitious Concrete and their efficacy in enhancing the durability of the cementitious composite when exposed to extremely aggressive conditions, with main reference to the stimulated autogenous crack sealing and self-healing capacity. A tailored characterization of the flexural and tensile behaviour of the composite has been first of all performed, also with the purpose of validating an experimental and analytical approach for the identification of the tensile stress vs. strain/crack opening constitutive relationship, which makes use of a purposely conceived indirect tensile test methodology, called Double Edge Wedge Splitting test. Secondly the crack sealing and self-healing capacity have been investigated, considering the recovery of both mechanical flexural performance and durability properties (water permeability) and cross analysing the results for a thorough validation. Microstructural investigations have complemented the aforementioned experimental programme to confirm the efficacy of alumina nano-fibres in enhancing the durability performance of the investigated composites. Superior performance of the mix with alumina nano-fibres with respect to parent companion ones has been highlighted and explained through both a nano-scale reinforcing effects which helps in controlling the cracking process since its very onset as well as through their hydrophilic nature which is likely to foster cement and binder hydration reactions, which can usefully stimulate crack sealing and performance healing recovery at both the macroscopic and mesoscopic fibre-matrix interface) level.
... van der Waals forces) and a very high surface area-to-volume ratio, nanoparticles tend to agglomerate in the solution. Nanoparticle agglomeration essentially leads to irregularities in the microstructure of the cement during the hydration process, unreacted pockets creating weak zones throughout the cement, and a reduction in cement mechanical properties (Jafariesfad et al., 2017b;Wang, 2017;McElroy et al., 2019McElroy et al., , 2020. Thus, the efficacy of the pre-dispersed nanoparticle solutions was assessed by transmission electron microscope (TEM) images. ...
The prediction of unconfined compressive strength (UCS) of oil well cement class “H” based on the artificial neural network (ANN) modeling approach is presented in this study. 195 cement samples were embedded with varying dosages of strength enhancing pre-dispersed nanoparticles consisting of nanosilica (nano-SiO2), nanoalumina (nano-Al2O3), and nanotitanium dioxide (nano-TiO2) at various simulated wellbore temperatures. The efficacy of the pre-dispersed nanoparticle solutions was analyzed by transmission electron microscope (TEM) images. Nano-SiO2 and nano-Al2O3 displayed excellent dispersibility throughout the solution. However, nano-TiO2 readily agglomerates which, at high concentrations, is detrimental to the UCS of cement. 70% of the data set was used to train the ANN model, 15% was used for validation, and 15% was used to test the model. The model consisted of one input layer with five nodes, one hidden layer with 12 nodes, and one output layer with one node. 12 nodes in the hidden layer resulted in the lowest mean squared error (MSE). The model parameters were saved and used after seven epochs during training, at which point the validation error began to increase leading to overfitting. The statistical performance measures consisting of MSE, the square root of the coefficient of determination (R), and the mean absolute percentage error (MAPE) showed values close to zero, one, and less than five percent, respectively. The statistical performance measures of the ANN model displayed superior results when compared to the measures obtained by the multi-linear (MLR) and random forest (RF) regression algorithms. The developed ANN model displays high predictive accuracy and can replace, or be used in combination with, destructive UCS tests which can save the petroleum industry time, resources, and capital.
... If the size of an object is about 10 nm, the amount of material required for effective reinforcement is fractions of a percent [2]. Alumina nanofibershas a number of advantages that provide a high potential for use as nano-reinforcement for building materials [3]. First of all, this is the low cost of the material, small diameter (about 10 nm) and high aspect ratio (1000 and more). ...
The article discusses the possibility of using alumina nanofibers to reinforcement cement mortar. Nanofiber is a twisted conglomerate, and its ultrasonic treatment in the water allows obtaining a stable dispersion. The research has been carried out on the effect of nanofibers on the viscosity of cement paste, as well as on the reinforcement of cement mortar. At concentrations less than 0,2%, there is no significant effect of nanofibers on the viscosity of the system. The studies were carried out on standard Portland cement at a water-cement ratio of 0.27. Reinforcement of cement mortar with aluminum oxide, with a concentration of 0 to 0.1%, does not give a significant change in the microstructure of the material. It was shown in the work that the use of nanofibers makes it possible to increase the strength of the system by 20% in compression and by 45% in bending.
... The use of alumina nanofibers is quite a novelty in the field of concrete and cement-based materials technology. In most of the few related studies [29][30][31][32], their beneficial effect, when added at less than 1% by weight of cement, have been shown on the compressive strength and other specific mechanical properties of a variety of cementitious materials. These range from HPFRCCs, in which case also a good interaction with the employed polyethylene or poly-vinyl-alcohol fibre reinforcement was measured through enhanced flexural deformation capacity, to oil well slurries, for which, besides moderate improvement also in splitting tensile strength, stability of the rheological performance upon their incorporation was also studied. ...
More than one century after its massive introduction in the building industry, concrete is still the most popular building material. Nevertheless, several critical infrastructures show severe signs of distress. This fact fostered, in recent years, the need of rethinking the design process of concrete structures, in view of reducing maintenance costs and extending their service life. This work has been performed in the framework of the H2020 project ReSHEALience (GA760824). The main idea behind the project is that the long-term behaviour of structures under extremely aggressive exposure conditions can highly benefit from the use of high performance materials, in the framework of durability-based design approaches. The project will tailor the composition of Ultra High Durability Concrete (UHDC), by upgrading the High-Performance Cementitious Composite/High-Performance Fibre Reinforced Cementitious Composite (HPCC/HPFRCC) concept through the incorporation of tailored nanoscale constituents focusing, among the others, on stimulating the autogenous self-healing capacity. This work shows the effectiveness of the aforementioned concept achieved through the incorporation in a reference HPFRCC of three types of nano-constituents: alumina nanofibers (0.25% by weight of cement), cellulose nanocrystals (0.15% by weight of cement) and cellulose nano-fibrils (0.15% by weight of cement). The influence of the nano-constituents has been analysed in terms of mechanical properties, such as flexural and compressive strength and on shrinkage and durability properties, analysed by means of sorptivity tests on un-cracked, cracked and self-healed specimens with reference to selected aggressive exposure scenarios representative of intended engineering applications of the investigated materials.
... In another study, Mahmoud and Elkatatny 43 found that the carbonation resistance of class G with the addition of NC can also be enhanced. McElroy et al. 44 investigated the use of alumina nanofibers (ANFs) in class H cement. They have found significant improvement in the mechanical properties of class H cement by the addition of ANF. ...
The mechanical properties of oil well cement slurry are usually measured to evaluate the durability, sustainability, and long-lasting behavior of a cement sheath under wellbore conditions. High-pressure and high-temperature (HPHT) conditions affect the mechanical properties of cement slurry such as its strength, elasticity, and curing time. In this study, an organically modified montmorillonite nanoclay (NC) and silica flour (SF) materials are used to enhance the strength of the class G cement. Four different cement slurries with the addition of different concentrations of NC (1% and 2%) and SF (20%) in a class G cement were tested under temperatures ranging between 70 and 100 °C and pressure ranging between 1000 and 3000 psia. The slurries were prepared by maintaining a water to cement ratio of 0.44. All the slurries were cured for 24 h before any test was conducted. Extensive laboratory experiments were carried out to measure the compressive and tensile strength of cement slurries cured at HPHT conditions. Compressive strength was measured using unconfined compressive strength (UCS) tests, scratch tests, and ultrasonic cement analyzer (UCA). Tensile strength was measured using breakdown pressure tests and Brazilian disc test analysis. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and petrophysical analysis were also carried out to evaluate the performance of new cement additives at HPHT conditions. Results showed that the addition of organically modified NC and SF significantly increased the compressive and tensile strength of the class G cement slurry cured at HPHT conditions.
The need for cementation constructions and material usage has increased tremendously. However, finding the optimum mix and designing the required construction is challenging. Hence, the present research work has planned to design a novel fruit fly-based mix selection (FFbMS) for designing the carbon nanotube (CNT). Here, the mixes that have been considered to design the single-walled CNT are polyvinyl alcohol (PVA) microfibre, carbon nanofibre (CNF) and cement paste (CP). Initially, the mixes are selected based on the ASTM C 305 standard, and the casting process has been performed. Then, several optimization iterations were executed to find the optimal state by valuing the mechanical properties in each iteration. Moreover, based on the gained compressive rate, tensile strength and crack rate, the optimal value has been set, and the mix range has been noted. The temperature range for testing Thermal characteristics varied from 100 to 1000 °C. The gained maximum compressive strength by a novel FFbMS is 24 GPA, and the flexural strength is 6.9 MPa at 600 °C and 4.8 at 1000 °C, which is quite better than the conventional mixes. Finally, the performance score has been measured in five ways: CP, CP + CNF, CP + PVA, CP + CNF + PVA and optimal CP + CNF + PVA. Here, the optimal CP + CNF + PVA have recorded the finest performance outcome. The gained maximum compressive strength by a novel FFbMS is 24 GPA, and the flexural strength is 6.9 MPa at 600 °C and 4.8 at 1000 °C, which is quite better than the conventional mixes.
In this paper, alumina nanofibers (ANFs) are studied as an additive in the reinforcement of the mechanical properties for oil well cement composite. To simulate the subsurface conditions during cementing operations of steam injection wells, the cement composite pastes were firstly cured at 50 °C (standard curing condition), and thereafter were cured at 300 °C/13 MPa (ordinary condition during steam injection operation). Four proportion of ANFs (from 0.1 to 0.4 % by wt. of cement) were added into the oil well cement composite. Their effects on the rheological property, the compressive and tensile strength were studied. Moreover, stress–strain behavior is analyzed. The mineralogical and microstructural characterization of the ANFs-affected pastes after the curing regime were tracked by X-ray diffractometer, thermogravimetric analysis, mercury intrusion porosimetry, scanning electron microscopy with energy dispersive X-ray spectroscopy. The results show that there is an optimal addition for ANFs and that more is not necessarily better when considering the reinforcement of the cement composite. Adding 0.3 % ANFs can improve the compressive and tensile strength by maximum increase of 9.18 % and 28.85 %, respectively. On the other hand, the incorporation of ANFs into the cement matrix resulted in the pore-size refinement, more formation of hydration gels but less formation of xonotlite. Two parameters, R100 and C-S-H gel/xonotlite ratio were defined by MIP and DTA results respectively. A great relationship was correlated between the R100, C-S-H gel/xonotlite ratio and mechanical strength, which can describe the relationship between hydration products, pore structure and mechanical strength quantitatively.
The cement sheath is paramount for wellbore integrity which provides zonal isolation (i.e. severance of fluids including gas, water, and oil), protection against corrosive fluids, and mechanical support. Failure of the cement sheath can result in damaging environmental impacts, lost revenue from production, and hazardous rig operations. The purpose of this study is to develop a novel fiber hybridized cement class "H" mixture, embedded with alumina nanofibers (ANF's) and sol-gel treated micro-synthetic polypropylene (PP) fibers. This study involves curing the cement samples at 170°F with 3,000 psi for 24 hours and measuring the unconfined compressive strength (UCS) and dynamic modulus of elasticity (MOE) shortly after samples are demolded. The optimum concentrations of fibers consisted of 0.15% ANF's by weight of cement (BWOC) and 0.09% PP fibers (BWOC). Due to the lack of PP fibers to resist cracks before they appear, there was minimum contribution towards obtaining ultimate UCS. ANF's were primarily responsible for reaching UCS due to their increased strength properties on the nanoscale level. However, PP fibers and ANF's simultaneously contributed towards enhancing the MOE on the nano and microscale levels. Cement samples remained in the elastic regions as the flexibility of both fibers were simultaneously utilized. Quadratic models were effectively derived using the response surface methodology (RSM) approach. The p-value of the models were less than 0.05, according to the analysis of variance (ANOVA) table, which indicated statistical significance. The lack of fit was not significant, and the model can be used to effectively navigate the design space according to the regression model summary. Essentially, the multi-variable and multi-objective optimization analysis was effective in predicting the UCS and MOE with only a 2% variation from the experimental values.
Over the past decades, the oil-well cement (OWC) has been used in sealing the wellbore-casing or inter-casing annular spaces. The Microbial-induced precipitation (MIP), on the other hand, is an emerging biomineralization cement system that can be utilized in energy, construction, mining, and other industries. However, understanding the mechanical integrity and peak strength of these cement systems are important for improving their applicability at varying in-situ-pressure and temperature conditions. Here, we experimentally investigated the mechanical integrity of the microbial-induced precipitation and the oil-well cement and their applicability to plugging of leakage pathways. We utilized 2 core samples from a sedimentary sequence with artificially induced fractures along the longitudinal axis of the cores, and treated the induced-fractures in these cores with the cementations from the MIP and OWC, respectively. We compared the mechanical properties of the cement seals in these cores to assess their mechanical integrities and applications. Our results show that the OWC is more efficient than MIP in sealing in-situ macro-fractures and provided a relatively greater mechanical integrity for the wellbore-casing or inter-casing annular spaces. In addition, although OWC has higher mechanical integrity over MIP, the MIP has an edge in its application for sealing of microfractures and mini-aperture of casing-cement or cement-formation delamination. We envisage that our study will advance the understanding of these methods and their applications for the enhancement of wellbore integrity for drilling operations, enhanced geothermal systems (EGS), geologic CO2 storage (GCS), and mining operations.
In this study, silica (SiO2) nanoparticles were deposited on the surfaces of micro-synthetic polypropylene (PP) fibers through the sol-gel process and combined with Alumina Nanofibers (ANF’s) to enhance the cement composite mechanical properties. Cement samples were cured at 82.2°C with 20.68 MPa for 24 hours to emulate wellbore conditions. Mechanical properties were experimentally tested and modeled through the design of experiments (DOE). Treated PP fibers did not contribute to the ultimate strength mainly due to their inability to resist stresses before cracks appear. Ultimate modulus of elasticity (MOE) and Poisson’s Ratio were synergistically improved on the nano and microscale levels. This is due to cement samples remaining in the elastic region and the flexibilities of the fibers. 0.15% ANF and 0.09% PP fibers by weight of cement (BWOC) were considered the optimum values after performing the multi-objective optimization analysis. Derived models were statistically significant and useful for predictions.
The reduction in the ease with which oil and gas reservoirs are discovered is a factor propelling the oil and gas technologies to depths that involve very complex and complicated methods of execution and environments. The increasing frequency of deviated, horizontal and multilateral wells, among others, are the evidence of the growing need to be able to efficiently explore more potentially resourceful areas. However, the ability to delve into mentioned prospects does not come posing no difficulty. These more complicated environments and techniques increase the risks already associated with conventional procedures. Therefore, the opportunity to mitigate these risks while meeting the demands and providing equal or even more satisfying results would be a huge step forward. That is where the application of nanotechnology comes in. This stems from the capability of nanomaterials to possess enhanced properties for accomplishing specific tasks as compared to their bulk counterparts, leading to breakthroughs in the evolution of the oil and gas industry.
This paper discusses how nanotechnology can be economically used in the oil and gas industry to solve challenges being faced at the various phases in the drilling operation. Also, currently, the selection of cost-efficient methods would be prudent in overcoming the challenges in the field otherwise, the production of oil and gas will be of no use if net returns are not positive. The applications of nanotechnology in these operations are so delicate that, an insufficient addition would render the nanoparticles unable to properly effect the desired changes and an extreme addition would lead to further complications in drilling operations. Many of the review articles available in the literature focus on the usage of nanoparticles in one aspect of the drilling operation, e.g. drilling fluid, while this article focuses on the usage and benefits of nanoparticles in the different aspects of the drilling industry. That is the motive behind the need for a further extensive review of more papers and how they can and should be applied in the drilling industry. Furthermore, more attention needs to be directed towards financial investigation, execution at repository circumstances, cross-connecting and congregation properties, wettability modifications and properties between the surfaces involved. This paper focuses on the various ways in which nanotechnology can help improve various drilling aspects as compared to the conventional methods of accomplishing the same goal.
High-temperature conditions drastically compromise the physical properties of cement, especially, its strengths. In this work, the influence of adding nanoclay (NC) particles to Saudi class G oil well cement (OWC) strength retrogression resistance under high-temperature condition (300 °C) is evaluated. Six cement slurries with different concentrations of silica flour (SF) and NC were prepared and tested under conditions of 38 °C and 300 °C for different time periods (7 and 28 days) of curing. The changes in the cement matrix compressive and tensile strengths, permeability, loss in the absorbed water, and the cement slurry rheology were evaluated as a function of NC content and temperature, the changes in the structure of the cement surfaces were investigated through the optical microscope. The results revealed that the use of NC (up to 3% by weight of cement (BWOC)) can prevent the OWC deterioration under extremely high-temperature conditions. Incorporating more than 3% of NC severely damaged the cement matrix microstructure due to the agglomeration of the nanoparticles. Incorporation of NC particles increased all the cement slurry rheological properties.
This study investigated the hydration characteristics and strength development of calcium sulfoaluminate-belite (CSAB) cements incorporating calcium carbonate (CC) powders with various particle size distributions and different gypsum amounts. In general, the CSAB hydration was accelerated by the CC powder, but the acceleration and resulting strength improvement were more effective with finer CC powder. Regardless of the fineness of the CC powder, it took part in the hydration of CSAB cement, forming hemicarboaluminate and monocarboaluminate phases. These hydration and nucleation effects compensated for the strength reduction from decreased cementing components (i.e., dilution effect) when finer CC powders were used, while they did not overcome the strength reduction when coarser CC powder was used. On the other hand, increasing the amount of gypsum for a given CC content improved the strength. The strength of CSAB cement had a clear inverse relationship with its total pore volume measured by mercury intrusion porosimetry (MIP). Thermodynamic modeling for CSAB cement hydration showed that the use of CC powder increased total volume of solid phases up to 6 wt % at a given amount of gypsum.
The influence of nanocellulose on oil well cement (OWC) properties is not known in detail, despite recent advances in nanocellulose technology and its related composite materials. The effect of cellulose nanofibers (CNFs) on flow, hydration, morphology, and strength of OWC was investigated using a range of spectroscopic methods coupled with rheological modelling and strength analysis. The Vom-Berg model showed the best fitting result of the rheology data. The addition of CNFs increased the yield stress of OWC slurry and degree of hydration value of hydrated CNF-OWC composites. The flexural strength of hydrated OWC samples was increased by 20.7% at the CNF/OWC ratio of 0.04 wt%. Excessive addition of CNFs into OWC matrix had a detrimental effect on the mechanical properties of hydrated CNF-OWC composites. This phenomenon was attributed to the aggregation of CNFs as observed through coupled morphological and elemental analysis. This study demonstrates a sustainable reinforcing nano-material for use in cement-based formulations.
Abstract Additives play significant role in oil and gas well cementing operations. There are varieties of cement additives that have been developed to allow the use of Portland cement in many different oil and gas well operations. In an attempt to formulate the appropriate cement slurry for any cementing job, the right additive must selected and the right quantity must be added. Additives have different functions and are broadly classified as accelerator, retarders, extenders, fluid loss agents, dispersants and many more. Each of the broad classification has different categories of additives that have been developed to perform almost the same function during cement slurry design. However, there some additives under each major type that are commonly used in cement slurry design for oil and gas well cementing operations. This paper reviews the broad classification of oil well additives giving emphasis to the commonly used additives during oil and gas well cementing operations.
The exceptional mechanical properties of carbon nanotube (CNT) such as high strength, elastic modulus and aspect ratio. reflect its potential to be used as reinforcements in cementitious materials. Nanotubes can be distributed on much finer scale and can act as bridge across void spaces and cracks. This in turn improves the overall mechanical properties of the composite. However, there are certain issues that need to be considered while producing CNT cement composites. With this end in view, an attempt has been made to summarize the effect of different parameters on properties of CNT-reinforced cementitious composites through interpretation of results obtained from a comprehensive study. Different sizes and dosage rates of MWNT were used to conduct parametric study. In addition, untreated and surface-treated commercially available MWNTs were used to make composites. Sonication was done for dispersion of nanotubes within cement matrix. An appropriate mixing technique was suggested after conducting a parametric study by varying the amplitude and time of sonication. In some cases, polycarboxylate-based superplasticizer was used as surfactant to disperse MWNTs in aqueous medium. It was observed that surface treatment of nanotubes and utilization of superplasticizer as surfactant enhance their solubility within water. It was also found that proper dispersion and dosage rates of MWNT have significant effect on composite behavior. A suitable mix proportion in terms of MWNT dosage rate, MWNT size and plasticizer proportion has been found. Moreover, it was suggested that flow values of composite paste is a good indicator of stability of the mix.
Since 1900's, well cementing is one of the most substantial method in casing application of oil, gas and geothermal. The American Petroleum Institute (API) identifies well cements in 8 classes with respect to pressure, temperature and the depth of the well. G class cement is the most commonly used cement type for well casing purpose due to its sulphate resistance ability. High sulphate-resistant (HSR) G class cements are often used in well cementing industry. API Standards mainly focus on uniaxial compressive strength (UCS) value of cements cured for 8 and 24 hours. There is no any available research on the long term (14 days) properties of G class cement in the literature. This study presents the comparison of UCS and Elastic modulus (E) growth of 3 different G class cements (2 domestic, 1 foreign products) over 14 days curing time. During the laboratory studies, samples prepared in the laboratory conditions with different curing times (2, 7 and 14 days) are tested based on ASTM standards. It is concluded that the increase in the curing time improves the UCS and E of cements 2-3 times. Logarithmic relationships exist between curing time and UCS, E. Moreover, mechanical properties of these products show significant differences between each other. The UCS and E values of G class cement produced in Turkey have values incontrovertibly lower than that of an equivalent foreign product. ÖZET 1900'lü yıllardan beri kuyu çimentolaması petrol, doğalgaz ve jeotermal kuyuların muhafazalanmasında kullanılan önemli bir yöntemdir. Amerikan Petrol enstitüsü (API) kuyu çimentolarını kullanılabildikleri basınç, sıcaklık ve kuyu derinliklerini esas alarak 8 farklı sınıfa ayırmıştır. G sınıfı çimento yüksek sülfat direnci nedeniyle bu çimentolar arasında kuyu muhafazası amacıyla yaygın olarak kullanılan bir çimento türüdür. API standartlarında bu çimentolar için genel olarak 8 ve 24 saatlik kür sürelerine bağlı tek eksenli basma dayanımı (TEBD) ve Elastik Modül (E) değerleri üzerinde durulmuştur. Literatürde bu çimentoların uzun vadede (14 gün) ulaştıkları TEBD değerleri bulunmamaktadır. Bu çalışmada 3 farklı firmanın ürettiği (2 yerli 1 yabancı) G sınıfı çimentoların kür süresine bağlı olarak TEBD ve E değerlerindeki artışlar sunulmuştur. Laboratuvar çalışmalarında, numuneler belirli standartlar ölçüsünde hazırlanıp farklı kür süreleri (2, 7 ve 14 gün) için deformabilite testine tabii tutulmuştur. Sonuç olarak çimentoların kür süresindeki artışın TEBD ve E değerlerini 2-3 kat arttırdığı görülmüş ve bu ilişki logaritmik eşitliklerle açıklanmıştır. Ayrıca tüm deney koşulları sabit tutulmasına karşın test edilen 3 ürünün mekanik özellikleri arasında önemli farklar gözlemlenmiştir. Yerli ürünlerin TEBD ve E değerleri eşdeğer yabancı ürüne göre yadsınamayacak şekilde düşüktür bulunmuştur. Anahtar Kelimeler: G sınıfı çimento, kür süresi, tek eksenli basma dayanımı, elastik modül, yüksek sülfat direnci, çimento mekanik özellik, kuyu muhafazalama.
Transmitting a longitudinal wave and a traverse wave into a composite material in a molten state has been studied in the online control of the composite material which cannot be evaluated by a conventional ultrasonic sensor as a final analysis, using the difference in the propagation characteristics of both modes. It is especially expected that measurement of the physical quantity which was not able to be conventionally measured can be performed by carrying out coincidence measurement of the ultrasonic wave in both modes. Therefore, in this research study, an ultrasonic probe, which can simultaneously transmit and receive a longitudinal wave and a traverse wave has been developed using an electromagnetic acoustic transducer (EMAT) because it has the advantage of measuring high temperature samples. In this study, two methods have been compared. The 1st method uses a traverse wave EMAT that travels in a vertical direction and a bar wave by which the low order mode is equivalent to longitudinal wave vibration. The other method is to carry out the mode conversion of the traverse wave by a traverse wave-EMAT. The longitudinal converted from the transverse wave are spread in the axis direction. As the experimental results of both optimizations of the drive conditions, it has been confirmed that the 2nd mode conversion method was promising. This paper reports about the trial process and the experimental results.
Data from around the world (Australia, Austria, Bahrain, Brazil, Canada, the Netherlands, Poland, the UK and the USA) show that more than four million onshore hydrocarbon wells have been drilled globally. Here we assess all the reliable datasets (25) on well barrier and integrity failure in the published literature and online. These datasets include production, injection, idle and abandoned wells, both onshore and offshore, exploiting both conventional and unconventional reservoirs. The datasets vary considerably in terms of the number of wells examined, their age and their designs. Therefore the percentage of wells that have had some form of well barrier or integrity failure is highly variable (1.9%–75%). Of the 8030 wells targeting the Marcellus shale inspected in Pennsylvania between 2005 and 2013, 6.3% of these have been reported to the authorities for infringements related to well barrier or integrity failure. In a separate study of 3533 Pennsylvanian wells monitored between 2008 and 2011, there were 85 examples of cement or casing failures, 4 blowouts and 2 examples of gas venting. In the UK, 2152 hydrocarbon wells were drilled onshore between 1902 and 2013 mainly targeting conventional reservoirs. UK regulations, like those of other jurisdictions, include reclamation of the well site after well abandonment. As such, there is no visible evidence of 65.2% of these well sites on the land surface today and monitoring is not carried out. The ownership of up to 53% of wells in the UK is unclear; we estimate that between 50 and 100 are orphaned. Of 143 active UK wells that were producing at the end of 2000, one has evidence of a well integrity failure.
The use of nanomaterials has become a popular way to improve the performance of cement-based composites. At the same time, ultra-high strength concrete is becoming more widely used. These materials provide superior durability to infrastructure elements, reducing the need for maintenance or early replacement. The performance boost is achieved by producing a denser microstructure and, in the case when nanofibers are used, may reduce the initiation of cracks. Aluminum oxide nanomaterials have the potential to provide a significant increase in compressive strength of cement-based materials. Here, the effect of incorporation of aluminum oxide nanofibers in oil well cement based mortars and composites is reported. The design of ultra-high strength concrete often requires a precisely tuned aggregate gradation, the use of specific cement types and high quantities of silica fume and superplasticizers along with high temperature and curing under elevated pressure. It was demonstrated that the use of small quantities of aluminum oxide nanofibers in an oil well cement based mortar could provide a compressive strength approaching 200 MPa. These levels were achieved at a considerably lower dosage of silica fume. It is envisioned that the high strength matrix is formed due to the reinforcing of calcium silicate hydrate layers which are formed around the nanofibers. This research demonstrated that due to a “shish kebab” effect the addition of well-dispersed aluminum oxide nanofibers at a very small dosage of 0.25% (by mass of cement) could provide up to 30% increase in compressive strength of cementitious systems, helping to meet the benchmarks for ultra-high strength cement-based composites.
The excessive changes of downhole pressure and temperature during injection/fracturing could initiate micro-annulus of cement sheath as the leakage pathway of underground fluid, which increases the risk of suspending production and environmental pollution. The investigations on accurate prediction, operational management and new technologies are significant to sustain well integrity and to enhance safety and efficiency in hydrocarbon and geothermal developments. In this work, a novel fully coupled thermal-stress model is proposed, which can predict the micro-annulus initiation and extension in the casing-cement-formation system. The interfaces of cement sheath with casing/formation are simulated using the contact interaction containing cohesive behavior and damage. The surface film condition is set on the internal wall of casing to simulate the heat transfer due to cold-water flow. This model is validated by the laboratory experiment and shows high accuracy. Results indicate that the maximum micro-annulus occurs during depressurization process after injection. It is newly found that the debonding could also emerge at the beginning of cold-water circulation in casing. The thermal effect, compared with pressure, is the dominated factor on micro-annulus initiation and size, while the pressure only causes a small plastic micro-annulus. For countermeasures, enhancing tensile strength is not an effective approach to prevent micro-annulus. By appropriately assigning the injection procedure, the micro-annulus can be eliminated in injection/fracturing operations. The findings can supply the technique support for well integrity assessment and management during hydraulic fracturing or high-pressure injection and production.
Cement sheaths are among the most important barrier elements in petroleum wells. However, the cement may lose its integrity due to repeated pressure variations in the wellbore, such as during pressure tests and fluid injections. Typical cement sheaths failure mechanisms are formation of radial cracks and microannuli, and such potential leak paths may lead to loss of zonal isolation and pressure build-up in the annulus. To prevent such barrier failures, it is important to study and understand cement sheath failure mechanisms.
This paper describes a series of experiments where we have used a tailor-built laboratory set-up to study cement sheath integrity during pressure cycling, where the set-up consists of down-scaled samples of rock, cement and casing. Cement integrity before and during casing pressurization is characterized by X-ray computed tomography (CT), which provides 3D visualization of radial cracks formed inside the cement and rock. We have studied how contextual well conditions, such as rock stiffness, casing stand-off and presence of mudfilm, influence cement sheath integrity.
The results confirm that the rock stiffness and casing stand-off determine how much casing pressure the cement can withstand before radial cracks are formed in the cement sheath, where the rock stiffness is significantly more important than casing stand-off. Furthermore, it is seen that the radial cracks in the cement sheath continue into the rock as well. However, when a thin mudfilm is present at the rock surface, the cracks stop at the cement-rock interface, and the cement sheath withstands less pressure before failure. The bonding towards the rock is thus of importance.
This paper reports a study to characterize the effect of cellulose nanocrystal (CNC) on the microstructure within hydrating oil well cement paste and correlate them to the mechanical performance at the macroscale. The changes in the pore structure and porosity of the hardened system was investigated using the gas sorption technique. The fresh oil well cement paste was subject to Dynamic Mechanical Analysis (DMA). The evolution in strength was measured over 8 weeks, under compression and tension. The results show that for pores less than 100 nm, the porosity was lower by 33% and the surface area is reduced by 66%, in the presence of CNC. These changes to the air-void network correspond to the evolution in compressive and tensile strength measured over the 56-day period. Of interest to oil well cements, is that adding CNC raised the compressive and tensile strength by 60% in the first 24 h.
Cement sheaths are designed to protect the integrity of oil and gas wells by mitigating movement of formation fluids and leaks. A failure of the cement sheath can result in the loss of zonal isolation, which can lead to sustained casing pressure. Gas migration through a cement sheath in the annulus is one of the main challenges that compromises zonal isolation. Failure in cement-casing bonding and micro annulus creation are other huge issues that compromises wellbore integrity. Even though some past studies have shown the application of nanomaterials, very few have conducted full scale tests measuring the compressive strength, thickening time and gas transition time of these materials.
In this study, nanosynthetic graphite with designed expansive properties has been introduced to fresh cement slurry. The expansive properties of nanosynthetic graphite were achieved by controlling the preparation conditions. The material was made from synthetic graphite and has a surface area ranging from 325-375 m2/gram. Several tests including compressive strength, rheology, and thickening time were performed. An addition of only 0.5% nanosynthetic graphite with appropriate reactivity was sufficient to maintain expansion in the cement system, leading to an early compressive strength development. It has excellent thermal and electrical conductivity and can be used to design a cement system with short and long-term integrity. Rheology and thickening time tests confirmed its pumpability. Controlling the concentration of the additive is a promising method that can be used to mitigate gas migration in gas bearing and shallow gas formations.
In this paper, carbon nanofibers (CNFs) with high aspect ratio were dispersed into epoxy matrix via mechanical stirring and ultrasonic treatment to fabricate self-sensing CNFs/epoxy composites. The mechanical, electrical and piezoresistive properties of the nanocomposites filled with different contents of CNFs were investigated. Based on the tunneling conduction and percolation conduction theories, the mechanisms of piezoresistive property of the nanocomposites were also explored. The experimental results show that adding CNFs can effectively enhance the compressive strengths and elastic moduli of the composites. The percolation threshold of the CNFs/epoxy composites is 0.186 vol% according to the modified General Effective Media Equation. Moreover, the stable and sensitive piezoresistive response of CNFs/epoxy composites was observed under monotonic and cyclic loadings. It can be demonstrated that adding CNFs into epoxy-based composites provides an innovative means of self-sensing, and the high sensitivity and stable piezoresistivity endow the CNFs/epoxy composites with considerable potentials as efficient compressive strain sensors for structural health monitoring of civil infrastructures.
The agglomeration state of SiO2, TiO2, Al2O3, Fe2O3, bentonite, and halloysite nanoparticles (NPs) in solutions, including simulated cement environments, and their agglomeration and reactivity within the cement paste were evaluated. In water, all NPs formed agglomerates, while sonication and addition of polycarboxylate-based, high range water reducer generally decreased the agglomerate size. Agglomeration of NPs was observed in the chemical environment of hydrating cement paste. The bridging role of Ca²⁺, charge balancing, screening by K⁺, and pH were identified as factors controlling agglomeration. TiO2, bentonite, and halloysite NPs enhanced the cement paste residual compressive strength after exposure to elevated temperature.
This chapter presents a survey of the research literature of cellulose nanomaterials (CNs) as additives to cementitious materials for property enhancement. These additives include cellulose fiber, microcrystalline cellulose (MCC), cellulose microfibrils (CMFs), cellulose nanofibrils (CNFs), cellulose nanocrystals (CNCs), and bacterial cellulose (BC). Emphasis was placed on how CNs interact with the cement particles, affecting the rheological properties of CN–cement mixtures, the hydration process, and the resulting mechanical properties. In addition, potential mechanisms responsible for the observed property modifications were introduced, providing insights into more efficient applications of CN in cementitious materials.
Well cementing is an important operation during drilling and completion of oil wells. The cement sheath must maintain well integrity behind the casing and provide long-term zonal isolation to ensure safety and prevent environmental problems. Despite recent technological advancement in smart polymeric materials, fibers and self-healing materials, it is still a big challenge to provide adequate long-term zonal isolation in severe oil well conditions. This review provides an overview of challenges faced in oil wells compromising the long-term ability of the cement sheath to provide zonal isolation. Factors controlling the long-term performance of cement sheath are discussed, in terms of shrinkage, tensile strength and flexibility. The use of nanomaterials as cement additive to fabricate flexible, high-tensile strength, and low-shrinkage cement system are reviewed. Introduction of nanomaterials into the cement system is a promising approach to design a sealant for the entire life of the well, thereby avoiding potential remedial costs and environmental impacts.
Annular sealants are used as static barriers to avoid fluid communication in-between zones and provide proper isolation of the different formations as well as support and protection to the casing. Therefore, the sealant can have a direct relationship to wellbore integrity. Data suggest more than 4 million hydrocarbon wells have been drilled globally; interestingly, some datasets indicate well integrity failure is highly variable (1.9 to 75%).
Historically, sealants have been characterized for short-term placement properties up to the point at which the sealant is pressure tested and a log is performed to establish if the annulus is properly sealed. However, as hydrocarbon resources are becoming gradually depleted in easy-to-recover environments, harsher conditions are more common. Additionally, stimulation and enhanced oil recovery (EOR) techniques involving high-pressure and high-temperature (HP/HT) cycles during the entire well life pose significant challenges to the sealant's integrity.
Sealant integrity issues can result in very high remediation costs, reduction of hydrocarbon production, and in some cases, loss of the well. All of these can lead to an increased cost per barrel of oil equivalent (BOE). During the last few decades, in view of the drastic changes in drilling conditions toward more challenging environments, the industry has opted for a sealant design approach, which considers all of the events that occur throughout the entire life of the well and their effects on integrity of the sealant and wellbore. This approach can be successful by employing analytical tools, which allow for synchronizing all of the different events and/or operations occurring during wellbore construction (from drilling to abandonment) with the different elements that encompass the wellbore architecture (geometry, formations, casing, and sealant). The use of these tools' forecasting capabilities can result in data-led decisions that allow operators to construct wellbores more efficiently and with more confidence, which should ultimately help reduce production costs.
This study focuses on illustrating an analytical tool for predicting the sealant's performance in both onshore and offshore cases throughout the life of the well and determining how this affects wellbore economics in the long term. Moreover, this paper discusses how sealants have evolved from conventional Portland cements to elastic-, foamed-, glass-bead-extended cements, and epoxy-resins based on wellbore integrity predictions performed by analytical tools. The impact of nanomaterials in converting cement/sealant systems into multifunctional and/or smart materials capable of self-sensing specific stimuli (i.e. stress, strain, etc.) is also shown.
In preparation for decommissioning work in the Southern North Sea sector, the permeability of historically used cement systems was investigated to help determine their effectiveness as well barriers. Because the placement of cement typically involves some degree of contamination with other wellbore fluids, determining the influence of seawater and water-based drilling fluid (WBM) contamination on the permeability of the set cement was of particular interest.
This study investigates the historically used API Class G cement at 16 lbm/gal and Class B cement at 15.8 lbm/gal using contemporary material samples.
Cores were prepared using neat cement, cement contaminated with up to 50 vol% seawater, and cement contaminated with up to 50 vol% WBM. The permeability to nitrogen flow of the set cores was measured using a Hassler sleeve.
To further investigate the structural changes causing the higher permeability observed in the contaminated samples, the structure of the cores was imaged using X-ray computer tomography (CT) scans.
All Class B mixtures within the investigated contamination range, all Class G mixtures with seawater contamination, and Class G mixtures up to 30 vol% WBM contamination produced set cores after curing.
The neat Class G cores showed approximately twice the permeability of the Class B cement cores, with the contaminated slurries of both cement types showing much higher permeability—approximately one to two orders of magnitude greater.
Further analysis using the CT scans revealed irregularities in the structure density in the contaminated samples, which might explain the increased permeability; however, further work is necessary to fully understand the mechanism causing this change. Understanding the potential effects of contamination on permeability and the structure could be useful for gaining insight into barrier performance of the cement sheath in circumstances where contamination is suspected.
Growing demand to drill high-pressure, high-temperature (HPHT) wells requires improved technology to overcome the HPHT challenges. Designing and testing for cost-effective cementing at simulated downhole conditions for HPHT gas and oil wells poses a challenge necessitating special consideration in the choice of cement slurry. A successful cementing job is dependent on how quickly and efficiently cement achieves its strength. Another critical aspect is to efficiently displace the mud out of the annulus by designing the cement slurry with desired rheology. Achieving desired mechanical and rheological properties of cement becomes harder and more complex at HPHT conditions.
A wide variety of admixtures are commonly mixed with the oilwell cement slurries to accommodate the extensive range of pressure and temperature and achieve enhanced mechanical and rheological properties. Carbon nanotubes are one of the most recent admixture options. This paper describes a study carried out to examine compressive strength and rheological properties (plastic viscosity, yield stress and gel strength) of oilwell cement slurries integrating chemical additives and multi-walled carbon nanotubes (MWCNT) at HPHT conditions.
The study determined that integrating MWCNT in oilwell cement led to substantial increase in the compressive strength values. The rheological properties of oilwell cement slurries are greatly reliant on temperature, water/cement ratio and the admixture used. The study indicated that using MWCNT in cement slurries improved the rheological properties of cement slurries and therefore their displacement efficiency in challenging conditions.
The mechanical and damping properties of CNT-reinforced cementitious composite structures were experimentally examined. In the experiments, an aromatic modified polyethylene glycol ether named TNWDIS and polyvinylpyrrolidone (PVP) were used to disperse CNTs, which were ultra-effective and compatible with cement hydrates. The growth of cement hydrates on the CNT surface was observed by Scanning Electron Microscopy (SEM) and identified by Energy Dispersive Spectrometry (EDS). X-Ray Powder Diffraction (XRD) analysis suggested that the mechanism by which the CNTs and cement hydrates were combined was a physical process. The compressive and flexural strengths of CNT/cement composites were improved by 17.3 and 16.3%, respectively, through the addition of 0.1 wt.% CNTs dispersed by PVP, while the addition of CNTs dispersed by TNWDIS led to a very limited improvement in strength. In addition, the loss factor of CNT/cement matrix was measured, and 0.1 wt.% CNTs dispersed by TNWDIS improved the loss factor by 25.9%, which is nearly twice greater than the improvement caused by 0.1 wt.% CNTs dispersed by PVP.
There have been numerous studies that have aimed at improving the low tensile strength, stiffness, and toughness of cementitious materials. This study aims to show that all of these characteristics can be greatly improved by the addition of ladder scale reinforcement at the nano and micro scale. Carbon nanofibers (CNFs) as well as polyvinyl alcohol (PVA) microfibers were used as reinforcement. The mechanical properties of the nanocomposites were investigated by fracture mechanics three-point bending test. The microstructure and the morphology of nanocomposite samples were studied using an ultra high resolution scanning electron microscope (SEM). The results clearly illustrate that the incorporation of nanofibers and microfibers greatly improves the flexural strength, Young's modulus, and toughness of the cement matrix.
The objective of this paper is to evaluate the dynamic moduli of atmospheric generated foamed cements at varying foam qualities routinely used for zonal isolation during well construction. Mechanical properties of the hardened foamed cement samples, such as Young's modulus (YM) and Poisson's ratio (PR) will be discussed, as well as permeability. All of these properties were obtained as a function of cyclic confining pressure ranging from 12 - 52 MPa (1,740 - 7,540-psi). The dynamic parameters were derived from ultrasonic velocity measurements, while permeability was measured using the transient method. Stepwise loading and unloading schedules were conducted to test the permeability and mechanical properties of the foamed cement at simulated wellbore conditions. Applied pressures varied between 6.5 MPa (943 psi) to 46.5 Ma (6,744 psi) in 4 MPa (580 psi) increments in two full up/down cycles. At every increment during these cycles, ultrasonic compressional (P), fast shear (SI), and slow shear (S2) wave velocities were measured, as well as the samples' response to the upstream sine pressure wave of approximately 0.5 MPa amplitude. From the sonic velocity data the dynamic moduli including YM and PR were calculated, while the sample's response to the pressure wave was used for permeability calculations. Observations of both neat and foamed samples reveal variations in YM as well as changes in the other properties and characteristics. Differences were observed between the foam qualities, depending on the parameter being assessed. This information should enable design contingencies and allow for more resilient designs of foamed cements when used during well construction. In addition, industry can use these results as a baseline for comparison with previous, current, or future work including recently acquired field-generated foamed cement samples (Kutchko et al., 2014). Copyright © (2015) by the Offshore Technology Conference All rights reserved.
While poor dispersion of carbon nanotubes (CNTs) is often blamed for degradation of properties of CNT reinforced polymers and their composites, the evidence that CNT agglomerates generate stress concentrations is based on common sense and, to a large extent, indirect. The present study investigates the effect of CNT agglomerates on the inter-fiber stresses in a unidirectional fiber reinforced composite using a numerical approach. The two-scale model recently developed by the authors allows simulating realistic CNT agglomeration scenarios. A parametric study is performed focusing on the size and density of CNT agglomerates as well as on the degree of agglomeration from perfectly dispersed to partially and fully agglomerated states. The study concludes that CNT agglomerates of a higher density and bigger size produce higher stress concentrations. They also give rise to higher stresses at the fiber/matrix interface. The least disturbance on the stress fields is introduced by homogeneously dispersed CNTs.
In this study the hydration of quaternary Portland cements containing blast-furnace slag, type V fly ash and limestone and the relationship between the types and contents of supplementary cementitious materials and the hydrate assemblage were investigated at ages of up to 182 days using X-ray diffraction and thermogravimetric analysis. In addition thermodynamic modeling was used to calculate the total volume of hydrates. Two blast-furnace slag contents of 20 and 30 wt.% were studied in blends containing fly ash and/or limestone at a cement replacement of 50 wt.%. In all cases the experiments showed the presence of C–S–H, portlandite and ettringite. In samples without limestone, monosulfate was formed; in the presence of limestone monocarbonate was present instead. The addition of 5 wt.% of limestone resulted in a higher compressive strength after 28 days than observed for cements with lower or higher limestone content. Overall the presence of fly ash exerts little influence on the hydrate assemblage. The strength development reveals that amounts of up to 30 wt.% fly ash can be used in quaternary cements without significant loss in compressive strength.
This paper discusses the tests conducted to determine the mechanical properties and the integrity of the cement sheath when subjected to cyclic loads. In addition, the effects of well operation on cement sheaths of different mechanical properties are analyzed, and the results are discussed. The results clearly demonstrate the importance of both laboratory measurements of cement-sheath mechanical properties and engineering analysis of the effect of well operations on the integrity of the cement sheath.
Lower-density cement systems are discussed in this paper, along with how the density was lowered by incorporating conventional additives such as
Pozzolanic beads (cenospheres) Hollow glass beads Gas bubbles Water-binding additives Silica fume Fly ash
Primary cementing compositions for oilwell applications are becoming increasingly complex and challenging because of the extreme well operating conditions encountered. The stresses exerted on the cement sheath during well operations could be severe enough to damage the cement sheath and negatively affect the safety and the economics of the well.
The results discussed in this paper should help operators design a cement sheath that can withstand the stresses from well operations, thus improving the safety and economics of the wells.
The permeability of Westerly granite was measured as a function of effective pressure to 4 kb. A transient method was used, in which the decay of a small incremental change of pressure was observed; decay characteristics, when combined with dimensions of the sample and compressibility and viscosity of the fluid (water or argon) yielded permeability, k. k of the granite ranged from 350 nd (nanodarcy = 10−17 cm2) at 100-bar pressure to 4 nd at 4000 bars. Based on linear decay characteristics, Darcy's law apparently held even at this lowest value. Both k and electrical resistivity, ρs, of Westerly granite vary markedly with pressure, and the two are closely related by k = Cρs−1.5±0.1, where C is a constant. With this relationship, an extrapolated value of k at 10-kb pressure would be about 0.5 nd. This value is roughly equivalent to flow rates involved in solute diffusion but is still a great deal more rapid than volume diffusion. Measured permeability and porosity enable hydraulic radius and, hence, the shape of pore spaces in the granite to be estimated. The shapes (flat slits at low pressure, equidimensional pores at high pressure) are consistent with those deduced from elastic characteristics of the rock. From the strong dependence of k on effective pressure, rocks subject to high pore pressure will probably be relatively permeable.
Data from six deep gas wells in Wyoming indicate that foamed cement outperforms conventional cement for zonal isolation. Two of the six wells were cemented across the production zones with conventional non-nitrified cements. These wells experienced outer-zone communication after the stimulation treatments. In the other four wells, the foamed-cement sheath provided zonal isolation even after the sheath was perforated and stimulation treatments were performed. The case histories described in this paper provide an opportunity to compare the performance of foamed cement to conventional cement on similar wells within a particular geographic area.
Large-scale laboratory testing has shown that foamed-cement is ductile and can deform as casing is pressurized, but will not crack like non-nitrified cement. These test results were confirmed by the results obtained in the six case-history wells. In the first two wells that were cemented, the operator used the conventional high-strength, non-nitrified cement across the formations. Tracer tags on the stimulation treatment showed that zonal isolation was not achieved and that the stimulation treatment communicated between the high- and low-pressure zones. The operator elected to use foamed cement for the last four wells to help obtain zonal isolation. In these wells, the stimulation treatment remained in the zone, little fracture growth occurred outside the target formation, and communication did not occur between the high- and low-pressure zones.
This paper provides details about the slurry design and job execution on the six case-history wells, and also presents the postjob analysis that verifies the conclusions.
Effect of 3.0-wt.% polyvinyl alcohol (PVA) was studied on the hydration of ordinary Portland cement in the presence and absence of 10% rice husk ash (RHA) by employing different techniques. The results have shown that PVA increases the strength and decreases the porosity. The increase in strength is due to the interaction of PVA with cement, forming some new compounds that fill the pores or improve the bond between the cement. The two cements behave in a similar way, and hence, replacement of cement by 10-wt.% RHA is beneficial.
Observation of the sudden appearance of annular pressure in wells exposed to high temperature changes or excessive internal casing pressure prompted a laboratory investigation to simulate conditions under which cement sheath failure could occur and thereby define the causes, characteristics, and limits of the problem. Cement sheath failure is manifested by interzonal problem. Cement sheath failure is manifested by interzonal annular-fluid movement and abnormally high annular pressure at some point behind the casing up to and at the surface. Cement sheath point behind the casing up to and at the surface. Cement sheath failure can be observed in any producing area where excessive flowing temperatures exist at the surface or where excessive internal casing test pressures are used. The detrimental effects of cement sheath failure are numerous and may include lost revenue from lost production, potentially hazardous rig operations (especially when annular isolation loss creates shallow-water sands supercharged with gas), and potentially hazardous producing operations. Exposure of steel casing to excessive temperature increases or internal test pressures causes diametrical and circumferential casing expansion. This circumferential force creates a shearing force at the cement/casing interface, causing failure at the cement/casing interface or radial fracturing of the cement sheath from the inner casing surface to the outer casing (or borehole) surface.
The investigation of cement integrity over life of well conditions continues to be a high priority within the well cementing industry. Increasing awareness of problems associated with cement sheath failure and subsequent loss of zonal isolation or sustained casing pressure have demanded that set cement material behavior and the coupled behavior of casing, cement and formation be more fully understood in order to make rational engineering decisions. Recent advances in wellbore stress modeling can now provide a probabilistic determination of the suitability of a particular cement design for the expected range of induced well stresses.
This paper describes the cement evaluation and wellbore-modeling methodologies specifically developed to predict the magnitude of tensile or compressive forces created by changing wellbore or reservoir conditions.
A method for testing formations of very low permeability is presented. The method is based on an analytical solution that describes the decay of a head change caused by pressurizing the volume of water stored in a shut-in well. Type curves prepared from this solution are matched with observed data to determine the hydraulic properties of the formation tested. The test is similar to the conventional slug test; however, its much shorter duration makes the testing of extremely tight formations feasible.
Volume changes can be calculated from the hydration stoichiometry of C3S if the composition of C-S-H is taken as C1.7SH4.0 with a density of 1.85 g/cm3. The results are in general agreement with the volume changes determined by Powers. However, the calculated evaporable water content is higher and the space-limiting water-cement ratio is calculated to be 0.42. The calculations can be applied also to the pozzolanic reaction and predict a marked increase in solid volume. In that case the composition of C-S-H is modified to C1.5SH3.8.
Laboratory investigations suggest that a precise relationship exists between Poisson's ratio, pore pressure and fluid type. Values of Poisson's ratio for dry samples are significantly smaller than those for fluid-saturated samples. The values are anomalously high for high pore pressure, with the possibility of differentiating between gas-saturated, brine-saturated and oil-saturated porous rocks.
The present study considers two overpressure models, based on oil/gas conversion and disequilibrium compaction, to obtain Poisson's ratio versus differential pressure (confining pressure minus pore pressure). The model results are in good agreement with experiments. Poisson's ratio is approximately constant at high differential pressures and increases (decreases) for saturated (dry) rocks at low differential pressures. Fluid type can be determined at all differential pressures from Poisson's ratio. The analysis is extended to the anisotropic case by computing the three Poisson's ratios of a transversely isotropic rock versus differential pressure. While one of them is practically independent of effective pressure, the others increase with increasing pore pressure. Experiments performed on cores under different pressure conditions, and calibration of the models with these data, provide a tool for inverting pore pressure from seismic data.
A broad experimental study has been performed to characterize the early hydration and setting of cement pastes prepared with Class H oil well cement at water-to-cement ratios (w/c) from 0.25 to 0.40, cured at temperatures from 10 to 60 °C, and mixed with chemical additives. Chemical shrinkage during hydration was measured by a newly developed system, degree of hydration was determined by thermogravimetric analysis, and setting time was tested by Vicat and ultrasonic velocity measurements. A Boundary Nucleation and Growth model provides a good fit to the chemical shrinkage data.Temperature increase and accelerator additions expedite the rate of cement hydration by causing more rapid nucleation of hydration products, leading to earlier setting; conversely, retarder and viscosity modifying agents delay cement nucleation, causing later setting times. Lower w/c paste needs less hydration product to form a percolating solid network (i.e., to reach the initial setting point). However, for the systems evaluated, at a given w/c, the degree of hydration at setting is a constant, regardless of the effects of ambient temperature or the presence of additives.
A semiempirical model is proposed to predict the evolution of chemical shrinkage and Ca(OH)2 content of cement paste at early age of hydration. The model is based on chemical equations and cement compound hydration rates. Chemical shrinkage and Ca(OH)2 amount are computed using the stoichiometric results of the hydration reactions considered in the model and the density of hydration products and reactants. The model validation is conducted by comparison between computed and experimental results achieved on ordinary cement pastes with different water-to-cement (w/c) ratios (0.25, 0.30, 0.35 and 0.40) cured at 10, 20, 30, 40 and 50 °C, respectively. Hydration degree and Ca(OH)2 content are determined using the thermogravimetric analysis (TGA) and chemical shrinkage evolution using a gravimetric method.The comparison reveals a good consistency between modelled and experimental data at early age of hydration.
Melamine and naphthalene-based superplasticizers have been used, over the past few decades, in order to improve the workability of concrete. Recently, more efficient copolymer formulations have been introduced for the same purpose. However, the influence of these chemical admixtures on the microstructure of the hardened concrete and, consequently, on its properties still needs to be extensively evaluated. Accordingly, the present work analyzes the hydration characteristics of cement pastes with naphthalene, melamine and copolymer-based superplasticizers, using the techniques of X-ray diffraction (XRD) and nuclear magnetic resonance (NMR), up to the age of 28 days. The results indicate a significant influence of the superplasticizer on the growth rates of the hydrates and on the state of polymerization of the silicates.
Hydration of portland cement pastes containing three types of mineral additive; fly ash, ground-granulated slag, and silica fume was investigated using differential thermal analysis, thermogravimetric analysis (DTA/TGA) and isothermal calorimetry. It was shown that the chemically bound water obtained using DTA/TGA was proportional to heat of hydration and could be used as a measure of hydration. The weight loss due to Ca(OH)2 decomposition of hydration products by DTA/TGA could be used to quantify the pozzolan reaction. A new method based on the composition of a hydrating cement was proposed and used to determine the degree of hydration of blended cements and the degree of pozzolan reaction. The results obtained suggested that the reactions of blended cements were slower than portland cement, and that silica fume reacted earlier than fly ash and slag.
This paper reviews the state of the field of nanotechnology in concrete. Definitions of nanotechnology, including nanoscience and nano-engineering in concrete, are provided. The impact of recent advances in instrumentation and computational materials science and their use in concrete research is discussed. Recent progress in nano-engineering and nanomodification of cement-based materials is presented.
We describe a quantitative mineralogical study of the hydrothermal reactions of an oil well cement with added silica and alumina, hydrated at temperatures from 200 to 350 °C. We compare the products with pure end member systems and find phase stability can be altered radically, even by small amounts of additive. The upper temperature limits of α-C2SH (< 250 °C), and 1.1 nm tobermorite C5S6H5 (< 300 °C) are increased. C8S5, reported in a cement-based system for the first time, is stable to 300 °C and is believed to prevent foshagite C4S3H formation below 350 °C. Hydrogarnet C3AS3−yH2y is the only aluminum bearing phase at < 300 °C but it coexists with C4A3H3 and bicchulite C8A4Si4H4 at higher temperatures. The presence of alumina increases the stability of 1.1 nm tobermorite greatly and also to a lesser degree of gyrolite.
New wellbore-integrity classification for gas migration problems and new cement formulations using Graphene Nano Platelets to prevent gas migration through cement
- Mohammed Mousa
- M Alkhamis
Mohammed Mousa M. Alkhamis, New wellbore-integrity classification for gas
migration problems and new cement formulations using Graphene Nano
Platelets to prevent gas migration through cement (2018). Masters Theses
7751. http://scholarsmine.mst.edu/masters_theses/7751.