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Venezuela’s largest heavy-oil deposits are found primarily in the Faja del Orinoco Belt. These deposits exhibit a low production rate under the cold flow method. The objective of this study is to model the impact of steam injection on the fluid dynamics, geomechanics, and seismic attributes for the Faja del Orinoco steam-assisted gravity drainage p...
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... the bottom line of the reservoir, the temperature dropped to 186.7 °C (31.4% lower than the maximum temperature). Figure 5 shows changes in the S o distribution from fluid substitution by steam injection at key time steps after 3600 days of injection. At the initial reservoir condition with a temperature of 20 °C, the S oi was 0.803, water saturation (S wi ) was 0.148 and S gi was Fig. 4 The 3D temperature profile (in °C) inside the steam chamber 0.049. ...
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The steam chamber rising process is an essential feature of steam-assisted gravity drainage. The development of a steam chamber and its production capabilities have been the focus of various studies. In this paper, a new analytical model is proposed that mimics the steam chamber development and predicts the oil production rate during the steam cham...
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... The propagation of fractures significantly increases the porosity and permeability in the wellbore area, which is beneficial to the heat transfer and water flow, aiming at a better circulation preheating effect in a shorter time and a lower economic cost [4][5][6]. At present, the studies on the coupled thermo-hydro-mechanical responses in oil sand reservoirs are mostly focused on the core-scale high-temperature high-pressure triaxial experiments (e.g., the Canadian oil sands and Venezuelan ultra-heavy oils) and engineeringscale numerically coupled thermo-geomechanical investigations [7][8][9][10][11][12]. However, there are a few studies on the laboratory experiments and numerical simulation for the Karamay oil sands in Xinjiang, China [13][14][15], which seriously hinder the understanding of reservoir geomechanics in the process of SAGD production. ...
Water injection in SAGD well pairs has rapidly developed to improve the circulation preheating efficiency and the steam chamber propagation speed. However, a key problem is to evaluate the coupled thermo-geomechanical effects of water injection under complex operations. In this paper, a coupled thermo-hydro-mechanical model considering skeleton shear dilation and phase change of bitumen was established. Major conclusions were drawn that there were large temperature changes only in two separate areas around wells. The pore pressures in the reservoir around wells and the base rock right below the production well increased significantly. The void ratio was improved in the reservoir around wells, especially in the inter-well region. The reservoir was lifted, and the largest uplift was right above the wells. This information can guide engineers in properly evaluating the field operations.
... Many current evaluations use indirect parameters such as stress relief, fracture evolution, and failure zones. Although these parameters provide insight into the performance of methane extraction, they can hardly address the evolution of permeability; thus difficulties arise when attempts are made to calculate seepage in mining activities [20][21][22][23]. In terms of gas flow and drainage simulation, the evolution of permeability and gas seepage during pressure relief mining is difficult to obtain by using theoretical predictions [10,[24][25][26][27]. ...
The stress-relief coal mine methane surface gas venthole is considered an effective method by which to realize coal mine methane exploitation and outburst prevention. Existing stress permeability models for caved zones, fractured zones, and bending subsidence zones were embedded into FLAC3D simulation software by using the FISH language. In cooperation with the in-situ data of a mine in a Huainan coalfield, the permeability distribution of pressure-relief surface gas drainage via different zones was simulated. The results indicated that the surface gas ventholes were effective for gas extraction from mining areas. By analyzing the distribution of permeability, three zones were identified: (1) the fully compacted zone, (2) the gradually compacted zone, and (3) the “O” type fractured zone. The seepage path of pressure-relief surface gas drainage was visualized. Most of the gas seeps into the adjacent rock mass at first and then is extracted through surface gas ventholes. Meanwhile, seepage of gas with different ventilation modes in longwall-panel, U-type, and Y-type was analyzed. Results shows that the Y-type ventilation mode is better than the U-type for gob gas control in the longwall panel. A comparison between the simulated model and the on-site recorded data is conducted, and results show that the model represents the site condition reasonably well. The simulation results provide theoretical guidance to engineering practice.
... Most of the evaluations depend on indirect indexes, e.g., failure zones, pressure relief zones, and fracture development. ese indexes cannot quantitatively describe permeability evolution and thus cannot guide subsequent seepage calculations and mining activities [25][26][27]. Both methods have advantages and disadvantages; thus, the integrated method has been widely employed to appraise the effect of pressure relief and permeability enhancement. ...
Coal 3 in group A is employed as a protective layer to release long-distance coal 4 in group B in Paner colliery (approximately 80 m vertical interval) as the mining depth extends downward, which is the first engineering test in the Huainan coal mining area. To evaluate the validity of the scheme, the permeability distribution, and evolution law, gas pressure distribution characteristics, swelling deformation, pressure relief range, and gas drainage volume of the protected coal seam are analyzed using a FLAC3D numerical simulation and field measurements. Therefore, different stress-permeability models are adopted for caved, fractured, and continuous deformation zones, and a double-yield model is applied in the goaf based on compaction theory to improve the accuracy of the numerical simulation. The results indicate that the extraction of coal 3 has a positive effect on permeability enhancement and pressure relief gas drainage. However, the dip angle of coal measurements causes asymmetric strata movement, which leads to the pressure relief and permeability enhancement area shifting to the downhill side, where the permeability enhancement effect of the downhill side is better than that of the uphill side. The permeability enhancement zone is an inverted trapezoid, but the effective pressure relief range is a positive trapezoid. The permeability of the protected coal seam in the pressure relief zone is significantly higher than that in the compressive failure zone. The permeability in the pressure relief zone will decrease again due to the recompaction of the coal seam with an advancement of the longwall face. Thus, pressure relief gas drainage is suggested during long-distance protective coal seam mining to eliminate gas hazards.
... An effective steam injection rate improves the heating effect of steam injection. An analysis of the effect of a steam chamber indicated that the cumulative steam injection-oil rate is approximately 2.7 optimum steam injection rate for 100 tons per day (Rabe et al., 2020). ...
Hot fluid injection, the preferred method used in the recovery of heavy oil and in various mechanisms such as steam drive, cyclic steam injection, steam stimulation, has become the industrial method for increasing recovery. These methods were used to promote heavy oil recovery by reducing the viscosity of asphalt and heavy oil and increasing the mobility of oil in reservoirs. The experimental test was carried out on a core sample obtained from the Ghareb Formation in the Wadi-Rajil area using cold water, hot water, and steam injection. The maximum recovery of oil in the sample using cold and hot water was 9.75% and 27.3 % respectively. On the other hand, the recovery of oil using steam injection was 42.5%. Thus, steam injection yielded more oil than cold and hot water injections in this experiment; the steam injection influx rate was approximately 15 mL/min. The total oil recovery of the sample using these three mechanisms was around 80%. The steam injection can, thus, be considered a promising thermal recovery method for asphalt and heavy oil in the Wadi-Rajil area.
... These properties include internal friction angle and cohesion. Rock mechanical laboratory testing on core samples are the most accurate methods for estimation of rock strength, but they never can lead to a continuous profile of rock strength (Rabe et., 2018(Rabe et., , 2020Chang et al., 2006) along wellbore and the tests were not executed on the study area. These parameters can be estimated using borehole as a continues source of rock strength to estimate internal friction and cohesion by using correlations of proposed in the literature based on acoustic data, that reflects the effect of lithology, porosity and fluid content. ...
The Amazon Fan provides a natural laboratory to study the generation of overpressure, due to rapid late Cenozoic burial that has resulted in gravitational collapse above shale detachments. Here we examine collapse systems for the first time using the techniques of petroleum systems analysis. We propose an integrated methodology based on numerical modeling constrained by the structural restoration of a seismic profile across the southwestern fan. The results provide information on the evolution of pore pressure and temperature and their implications for the operation of the detachment and overlying extensional and compressional faults during the deposition of up to 6 km of sediment over the last 8 Ma. The modelled thermal history implies that fluid release by smectite-to-illite transformation has taken place within the thickening sedimentary succession, but has not significantly contributed to pore pressures along the detachment. Modeling of hydrocarbon generation and migration from source rocks beneath the fan indicates gas accumulated in successions at depths of 10²–10³ m beneath the detachment without influencing pore pressures along it. In contrast, model results indicate that overpressures have varied in response to disequilibrium compaction. Fault activity within the collapse system took place during phases of higher sedimentation rates, and ceased from 5.5 to 3.7 Ma when sediment supply to the SE fan decreased. From 2 Ma, renewed sediment flux and shelf-slope progradation led to a basinward migration both of overpressure along the detachment and of fault activity above it. We conclude that gravity tectonics in the Amazon Fan over the last 8 Ma have been mainly controlled by overpressures due to disequilibrium compaction, with secondary contributions from clay mineral transformation. Present-day pressure conditions show that the southeastern Amazon Fan is not at equilibrium and gravity driven deformation could occur at any time.
This work interprets the pore pressure distribution and in-situ stress magnitudes in the ~ 10,600 feet thick Neogene succession of the West and South Al-Khilala gas fields, onshore Nile Delta. The Messinian incised valley-fill (IVF) fluvio-marine sediments host the principal gas-bearing zones having a 0.47 PSI/feet pore pressure gradient, as seen from the downhole measurements. Early Pliocene is marked by a dramatic regional sea-level rise which deposited thick marine shales unconformably above the Abu Madi IVF reservoir facies. A high sedimentation rate during Pliocene retained excess porosity and translated to a mild overpressure of around 0.55 PSI/feet in the Kafr El Sheikh Formation due to compaction disequilibrium. Vertical (Sv), minimum (Sh), and maximum (SH) horizontal stress gradients are estimated as 0.97–0.98; 0.64–0.76, and 0.86–1 PSI/feet, respectively. Interpreted stress magnitudes decipher a normal to strike-slip stress state in the studied fields. B-Quality wellbore breakouts with ~ 600 feet cumulative length infer NNE-SSW SH orientation, almost parallel to the motion direction of the African plate. Wellbore stability analysis indicated a minimum mud weight of 11.45 PPG needs to be maintained against the Pliocene shales which exhibited major wellbore instability issues in the exploratory drilling campaign. Based on the interpreted pore pressure, Sh, and collapse pressure gradients, a safe drilling mud window is proposed to ensure borehole stability.
Article highlights
Pliocene marine shales have mild overpressure resulting from disequilibrium compaction, while the Miocene Abu Madi reservoirs have 0.47 PSI/feet pore pressure gradient.
Normal to strike-slip stress state in inferred in the West and South Al-Khilala gas fields.
B-Quality wellbore breakouts infer NNE-SSW SH orientation.
Collapse pressure and safe mud weight window are inferred to ensure borehole stability in the Miocene shales.
The Amazon River culminates in one of the world’s largest deep-sea fans, a shelf-slope wedge that has prograded seaward since the late Miocene while undergoing gravitational collapse above shale detachments. In order to examine the overpressure mechanisms acting in the Amazon Fan and affecting its gravity tectonics, I developed an innovative approach based on the integration of modeling methods commonly used in the oil &gas industry, applied here for the first time to a collapsing passive margin depocenter. Two regional seismic sections were interpreted, depth-converted, structurally restored and then used for basin and geomechanical modelling to investigate overpressure mechanisms and deformation along the detachments and associated extensional and compressional faultsduring the deposition of up to 6-10 km of sediment over the last 8 Ma. The modeling results provide information on the evolution of pore pressure and temperature and their implications for the operation of the southeast and northwest structural compartments of the gravity tectonic system. It is found that themain control on gravity tectonics was sediment supply, which differed in magnitude and style between the SE and NW compartments. In both compartments, progradation of the Amazon Fan drove the basinward migration of the deformation front in response to a seaward migration of overpressure along the detachment. In the SE compartment, fault activity was observed only during periods of higher sedimentation, whereas in the NW compartment, continuous fault activity reflected constant high sediment input over the last 8Ma. Disequilibrium compaction (undercompaction) is argued to be the primary mechanism of overpressure in the Amazon Fan, however the secondary role of inflationary overpressures cannot be excluded. The temperature-dependent smectite-illite transition window was present within the fan, mainly above the detachment in the SE compartment, but at the level of the detachment on the inner and outer part of the NW compartment. Thermogenic gas generation (by primary and secondary cracking) did not affect the gravity system in the SE compartment, where most gas was expelled prior to the growth of the fan and thereafter trapped in shale-rich layers beneath the detachment, whereas in the NW compartment it has contributed to higher pore pressure on the detachment and some faults. Thus, temperature-driven fluid mechanics played a different role in terms of inflationary overpressure in the two structural compartments. These differences are in part due to differing different crustal types beneath the two compartments, which syn- to post-rift basin modeling shows produceddistinct thermalhistories,modulated by thermal blanketing during the growth of the Amazon fan. In particular, this led to lower heat flow in the NW compartment over the last 8 Ma, accounting for the greater depth of the smectite-illite transition window relative to the detachment and the later expulsion of thermogenic gases. The findings of this thesis thus provide new insights into the evolution of pore pressure during the growth and collapse of the Amazon Fan, and distinguish particularities of each structural compartment linked to its long-term history. The results also show that the integration of basin modeling methodologies provides an extremely useful tool to investigate the tectonic and sedimentary dynamics of Late Cenozoic depocentres,even when there is limited data. As a perspective of future work, dedicated studies of the crustal and thermal history of the Amazon margin might be done.
