Carlos A. Grattoni

University of Leeds · School of Earth and Environment

Porosity and permeability measurements aid the characterisation of geothermal reservoirs as they improve understanding of the impact of rock–fluid interactions during the life cycle of wells. Core flooding experiments can help us comprehend the rock–brine electrochemical system as critical parameters like salinity, pH, temperature, or pressure chan...

The effects of pore shape and wettability on menisci in porous media can be clearly demonstrated using circular and square tubes containing oil (blue, top layer) and water (red, bottom layer). Two water wet tubes (A, C) and two oil-wet tubes (B, D) are needed. We used diameter 10 mm and length 100 mm tubes. The shape of the interface curvatures wit...

Evaporites are typically described as impermeable seals that create some of the world’s highest reservoir pressures beneath the salt seal. However, several laboratory studies demonstrate that evaporites can retain open pore spaces that hydraulically connect the sediments above and below them in sedimentary basins. During the Messinian Salinity Cris...

The paper presents new measurements on key petrophysical properties of fault rocks and shale top seals at subsurface conditions. In particular, results are presented from a new instrument that can make mercury injection capillary pressure measurements at reservoir conditions and accurately measure the threshold pressure. Absolute gas permeability f...

2018 Elsevier B.V. The authors regret that Fig 3 was incorrectly printed as a duplicate of Fig. 4. The correct Fig 3 with original caption is given here. The authors would like to apologise for any inconvenience caused. [figure-presented] Caption Fig. 3. Plot of H against ϕ i using Eq. (7), with ϕ o = 0.20. H = 0 when ϕ i = 0.20. When F = 0 there a...

Water production during gas and oil recovery is a major problem for the oil industry, as the average worldwide production is more than five barrels of water per barrel of oil. Among the many attempted remedies, water-based polymers and cross-linked gels are often injected into the reservoir to control excessive water production. Recently, oil-based...

Many petrophysical properties of tight rocks, such as permeability and electrical resistivity, are very stress sensitive. However, most mercury-injection measurements are made using an instrument that does not apply a confining pressure to the samples. Here we further explore the implications of the use and analysis of data from mercury-injection p...

It is common practice to create geologically realistic production simulation models of fault compartmentalized reservoirs. Data on fault rock properties are required, to calculate transmissibility multipliers that are incorporated into these models, to take into account the impact of fault rocks on fluid flow. Industry has generated large databases...

The purpose of this thesis was to study in detail the structural architecture and the properties of the Candigliano fault zone (Piobbico PU, Italy), and to calculate its permeability by using the classical statistical algorithms of Fault Seal Analysis (FSA) calibrated for siliciclastic sequences, adapted and applied for a single fault (F1) in carbo...

Many petrophysical properties (e.g. permeability, electrical resistivity etc.) of tight rocks are very stress sensitive. However, most mercury injection measurements are made using an instrument that does not apply a confining pressure to the samples. Here we further explore the implications of the use and analysis of data from mercury injection po...

Gas production from shale resource plays has transformed the USA energy market. Despite the knowledge gained from the analysis of large amounts of shale core, appraisal of shale gas resource plays requires a large number of wells to be drilled and tested. Ideally, core analysis results would provide an indication of both the gas filled porosity and...

Gas flow in shale is a very complex phenomenon, currently investigated using a variety of techniques including the analysis of transient experiments conducted on full core and crushed shale using a range of gases. A range of gas flow mechanisms may operate in shale including continuum flow, slippage, transitional flow and Knudsen diffusion. These p...

Deformation bands are the most common strain localization structures found in deformed granular porous rocks. Numerous documented studies on deformation bands in siliciclastics found that deformation bands create barriers to flow as a result of the following mechanisms: i) grain reorganisation, ii) cataclasis, and iii) dissolution and cementation....

Compactive faulting was systematically investigated on highly porous chalk containing deformation bands from Pegwell Bay. The pore grain radius, porosity, and Klinkenberg-corrected gas permeability were determined for both deformed and undeformed rock. CT-scans show a decrease in porosity by more than 10% in deformation bands compared to the associ...

Permeability characterisation of low permeability, clay-rich gas sandstones is part of production forecasting and reservoir management. We studied 63 samples from North West European Rotliegend sandstone reservoirs, where the pore sizes can range from nm to μm in order to estimate which pores control permeability to gas. Petrography indicates that...

Permeability characterisation of low permeability, clay-rich gas sandstones is part of production forecasting and reservoir management. The physically based Kozeny (1927) equation linking permeability with porosity and pore size is derived for a porous medium with a homogeneous pore size, whereas the pore sizes in tight sandstones can range from nm...

Gas flow in shale is a complex phenomenon and is currently being investigated using a variety of modelling and experimental approaches. A range of flow mechanisms need to be taken into account when describing gas flow in shale including continuum, slip, transitional flow and Knudsen diffusion. A finite volume method (FVM) is presented to mathematic...

Gas flow in shale is a complex phenomenon and is currently being investigated using a variety of modelling and experimental approaches. A range of flow mechanisms need to be taken into account when describing gas flow in shale including continuum, slip, transitional flow and Knudsen diffusion. A finite volume method (FVM) is presented to mathematic...

Gas flow in shale is a poorly understood and potentially complex phenomenon. It is currently being investigated using a variety of techniques including the analysis of transient experiments conducted on full core and crushed shale using a range of gases. A range of gas flow mechanisms may operate including continuum flow, slippage, transitional flo...

[1] Reservoir injectivity and storage capacity are the main constraints for geologic CO2 sequestration, subject to safety and economic considerations. Brine acidification following CO2 dissolution leads to fluid-rock interactions that alter porosity and permeability, thereby affecting reservoir storage capacity and injectivity. Thus, we determined...

Water soluble polymers are widely used in oil and gas reservoirs and usually injected into the reservoir rocks to alter their flow properties. The rheologies of the polymer solution and their adsorption or interaction with the porous system are crucial for the success of the injection. This work aims to investigate the formation of residual polymer...

Field development planning is critical in the development of successful EOR programmes. Various types of information are required from reservoirs regarding the interaction of the crude oil/brine/rock (COBR) system so as to optimize the EOR process. Core analysis studies are central to gathering the information needed for optimizing EOR. In this pap...

Tight gas-condensate reservoirs contain large reserves, but can be extremely costly to develop. Understanding the fundamental controls on the fluid flow behaviour of tight gas and gas-condensate reservoirs has the potential to result in more cost-effective reservoir development and help increase the world‘s producible reserves. The principal object...

Much published fault rock permeability data was measured using inappropriate laboratory conditions (low confining pressure and distilled water as the permeant). However, the results are reasonably consistent with theoretical predictions from simple clay-sand mixing models. This may suggest that the effects low confining pressures (increases permeab...

Fault rocks can function as barriers to subsurface fluid flow and affect the storage of CO2 in geological structures. Even though flow across faults often involves more than one fluid phase, it is typically modeled using only single-phase functions due to a lack of fault rock relative permeability data and complexities in incorporating two-phase fl...

It is well known that thermal enhanced oil recovery (EOR) improves recovery by lowering the oil viscosity and so is usually performed in heavy oil reservoirs. Wettability alteration may also occur during thermal EOR in which case it may also affect production rates in light oil reservoirs. The interaction between crude oil-brine on different rock s...

Nuclear magnetic resonance (NMR) is a useful tool in reservoir evaluation. The objective of this study is to predict petrophysical properties from NMR T-2 distributions. A series of laboratory experiments including core analysis, capillary pressure measurements, NMR T-2 measurements and image analysis were carried out on sixteen greensand samples f...

It is well known that thermal EOR improves recovery by lowering the oil viscosity and so is usually performed in heavy oil reservoirs. Wettability alteration may also occur during thermal EOR in which case it may also affect production rates in light oil reservoirs. The interaction between crude oil-brine on different rock surfaces as a function of...

Direct insight into the mechanisms of flow and displacements within small-scale (cm) systems having permeability heterogeneities that are not parallel to the flow direction (cross-bedding and fault zones) have been carried out. In our experiments, we have used visual models with unconsolidated glass bead packs having carefully controlled permeabili...

Unconventional reservoirs are becoming important resources for the future as a result of the drop in production from conventional reservoirs. Tight gas reservoirs are an example of unconventional reservoirs which have very low porosity and permeability, and often they typically have large lateral extent. We analyse several Mam Tor siltstone samples...

Nuclear magnetic resonance (NMR) is a useful tool in reservoir evaluation. The objective of this study is to predict petrophysical properties from NMR T2 distributions. A series of laboratory experiments including core analysis, capillary pressure measurements, NMR T2 measurements and image analysis were done on sixteen greensand samples from two f...

The physical effect of multiphase fluid distribution and flow at permeability boundaries has not been fully investigated, particularly at the pore scale (1–100μm), although such behaviour can significantly affect the overall scaled-up reservoir trapping capacity and production performance. In this article, microscale physical models have been used...

Gas condensate reservoirs are becoming increasingly important due to the growing world dependence on gas supply and the high value of condensate in the market place. The current understanding of fluid flow behaviour within tight rocks is limited due to the limited data available. Furthermore, the lack of accurate relative permeability data for tigh...

Gas reservoirs usually produce some associated water during gas production. Within the reservoir, mainly near the well bore, water evaporates as the reservoir pressure declines, and the partial water pressure increases. Water evaporation also occurs in gas reservoirs when dry gas is injected for pressure maintenance or CO 2 sequestration. Water vap...

This article uses compositional simulation to investigate the impact of different geometries and permeability contrasts within cross-bedded laminations on oil recovery from multicontact miscible gas injection. Each of the following was tested, keeping all other inputs unchanged: permeability contrast, laminae thickness, laminae angles, and exclusio...

Compositional simulation is usually used to predict the performance of multi-contact miscible (MCM) recovery schemes. One key assumption in most such simulations is that of instantaneous compositional equilibrium is achieved between phases in each grid block. This is despite the fact that most grid blocks are tens of metres long and at least a metr...

Steam injection is becoming increasingly used to enhance heavy oil production even in complex reservoirs such as fractured carbonates. However, injecting steam into fractures has the potential to change reservoir permeability because increasing the temperature causes the reservoir rock to expand potentially closing fractures and condensed water may...

It is becoming increasingly common practice to model the impact of faults on fluid flow within petroleum reservoirs by applying transmissibility multipliers, calculated from the single-phase permeability of fault rocks, to the grid-blocks adjacent to faults in production simulations. The multi-phase flow properties (e.g. relative permeability and c...

The recovery of oil by injection of miscible gas has been a subject of interest and research in petroleum engineering over the past 40 years. In a first contact miscible displacement, the injected fluid forms only single-phase mixtures with oil in place, so in theory, 100% recovery can be achieved. Unfortunately, many phenomena conspire to limit th...

The effect of heterogeneities on miscible and immiscible flood displacements in 2D bead packs in quadrant form, 2× 2 block heterogeneity, with either a permeability or a wettability contrast is the subject of this paper. The physical processes occurring during miscible and immiscible flow and displacement within permeability and wettability quadran...

Laboratory studies and a number of field pilots have demonstrated that CO2 injection into coal seams has the potential to enhance coalbed methane (CBM) recovery with the added advantage that most of the injected CO2 can be stored permanently in coal. The concept of storing CO2 in geologic formations as a safe and effective greenhouse gas mitigation...

For many years it has been common practice to adjust fault transmissibility multipliers within production simulation models to achieve a history match without any scientific justification. In effect, this often means that faults are made ‘scapegoats’ to compensate for inadequacies in reservoir characterisation. In recent years it has become increas...

We investigate oil recovery from multicontact miscible (MCM) gas injection into homogeneous and crossbedded porous media, using a combination of well-characterized laboratory experiments and detailed compositional flow simulation. All simulator input data, including most EOS parameters, were determined experimentally or from the literature produced...

The equilibrium physical property data (densities, viscosities, refractive index, interfacial tensions, and contact angles) for the liquid−liquid system isopropyl alcohol + cyclohexene + water have been determined at 294 K. The phase diagram and equilibrium tie lines were evaluated. The compositions of the coexistence curve were determined through...

Retrograde condensate reservoir behaviour is complex with much of the detailed mechanisms of the multiphase fluid transport and mass transfer between the phases within the porous matrix still speculative. Visual modelling of selected processes occurring at the pore level under known and controlled boundary conditions can give an insight to fluid di...

This paper considers the fundamentals of mechanical structures and fluid flow characteristics in lime-stabilised mineral–biomass mixtures for potential novel applications in low-value bulk industrial products or wastes. As contained organic matter is expected to be essentially stable indefinitely under anaerobic conditions, the composites represent...

A mathematical model is developed for the flow of water through a channel impregnated with a polymer gel. The model uses a Brinkman equation along with an experimentally-observed velocity-dependent permeability. Numerical and approximate analytical solutions are given. When combined with a mathematical analysis of oil flow through polymer gels, whi...

Faulted or fault zone rocks rocks often have a significant impact on fluid flow within petroleum reservoirs. Until recently, only their single-phase permeability values have been measured and the effects of their multi-phase flow properties on petroleum production have been neglected. Here we present results on the multi-phase flow properties of ca...

The changes in gas and oil relative permeabilities as miscibility is approached are of particular importance in multi-contact miscible displacements. These changes are a function of the detailed phase behaviour of the fluids and their physical properties as well as the properties of the porous medium itself.In this work, we investigate the behaviou...

Several research groups are currently investigating the determination of wettability using NMR relaxation times. Although correlations with traditional wettability indices have been presented with some success, further effort is needed to relate the wettability at pore-scale to a core-scale measurement of NMR response. For example, a qualitative me...

Nuclear magnetic resonance (NMR) (H1) transverse relaxation measurements were carried out on 37x70-mm cylindrical mineral/organic composites to determine and monitor the porosity evolution. Porosity is related, in principle, to the stability of such materials in geotechnical applications, for example, engineering foundations. The specimens represen...

Gravity-stable, miscible gas injection is a common oil recovery technique throughout the world. In homogeneous environments recovery efficiencies may be more than 90%. However the influence of heterogeneity on the sweep efficiency in these recovery schemes is not well understood. For example most clastic reservoirs contain ‘discontinuous’ shales th...

Many oil fields produce from fluvial sands where cross bedding lamination is one of the most common type of small-scale heterogeneity. To our knowledge, there are no published studies on the effects of cross-bedding laminations on multi-contact miscible (MCM) displacement processes and how they might alter the development of miscibility during oil...

Both vaporizing and condensing miscible gas floods are being conducted in a large number of reservoirs worldwide. The performance of these gas floods is usually determined via a combination of laboratory analysis and compositional simulation. However the ability of numerical simulation to correctly predict the progress of a multi-contact miscible d...

A surface profilometer was used to measure fracture profiles every 10 microns over the surfaces of a replica of a fracture in a red Permian sandstone, to within an accuracy of a few microns. These surface data were used as input to two finite element codes that solve the Navier-Stokes equations and the Reynolds equation, respectively. Numerical sim...

Water production from oil and gas reservoirs is increasing worldwide, as more reservoirs are becoming mature. In order to control water production, polymers and gels are often injected into the formation to reduce the water permeability. These systems are known as relative permeability modifiers. Although these methods sometimes lead to significant...

We have conducted high-resolution Navier-Stokes simulations and laboratory measurements of fluid flow in a natural sandstone fracture. First, epoxy casts were made of the two opposing fracture surfaces. The surface profiles of the two surfaces were then measured at a vertical resolution of ±2 μm, every 20 μm in the x and y-directions, over 2 cm × 2...

Miscible WAG injection has been implemented in a number of oil fields around the world and there are a number of numerical studies investigating the effect of rate, gravity, slug size and heterogeneity on WAG performance. However there are very few laboratory studies of WAG displacement efficiency reported in the literature. In this paper we report...

In the depressurisation of reservoirs already produced to waterflooded residual oil, solution gas is released when the reservoir pressure drops to below the bubble point. This gas becomes mobilised when the critical gas saturation has been reached. Additionally, the oil itself can become mobile from its residual state and can also be produced under...

Predicting reservoir wettability and its effect on fluid distribution and hydrocarbon recovery remains one of the major challenges in reservoir evaluation and engineering. Current laboratory based techniques require the use of rock–fluid systems that are representative of in situ reservoir wettability and preferably under reservoir conditions of pr...

Nuclear Magnetic Resonance (NMR) T 2 measurements can be used directly to estimate petrophysical properties of reservoir rocks such as porosity and irreducible water saturation. They are also sensitive to pore-size distribution enabling the estimation of permeability and potentially capillary pressure. Several methods have been proposed to derive s...

Gas flotation is widely used for oily wastewater cleanup. The crux for flotation is the adhesion of the gas bubble to the oil drop. A spreading stage of oil onto the gas is vital for efficient bubble–oil rise. Thus spreading and non-spreading oils will present different fluid configurations and stabilities for bubble rise and a positive oil on a wa...

An experimental and computational study has been conducted of fluid flow in a rough-walled rock fracture, with emphasis on deviations from Darcy's law in the regime of Reynolds numbers greater than unity. First, profiles of a fracture in a red Permian sandstone were measured with a profilometer, to within +/- 2 microns in elevation, at intervals of...

We use a combination of analytic, experimental and numerical techniques to quantify flow around discontinuous shales and the extent to which they cause oil to be bypassed. We begin by using analytic solutions and well-characterised bead-pack experiments to investigate flow around a single, isolated shale during miscible (M=1, M=10) and immiscible d...