The Experts below are selected from a list of 249 Experts worldwide ranked by ideXlab platform
Koorosh Asghari - One of the best experts on this subject based on the ideXlab platform.
-
Effect of operating pressure, matrix Permeability and connate water saturation on performance of CO2 huff-and-puff process in matrix-fracture experimental model
Fuel, 2010Co-Authors: Farshid Torabi, Koorosh AsghariAbstract:Abstract The main objective of study is to examine the performance and efficiency of CO2 huff-and-puff process for improving oil recovery and subsequent storage of CO2 in light-oil fractured porous media through designing and conducting targeted experiments. The experimental set-up consisted of a high-pressure stainless steel cell made specially to hold a cylindrical Core with spacing around it, simulating a matrix and its surrounding fracture environment. The matrix was saturated with normal decane, which was used as oil during the experiments. A total of six separate sets of huff-and-puff experiments, using CO2 as solvent, were conducted under operating pressures of 250, 500, 750, 1000, 1250, and 1500 psi. The temperature was kept constant (35 °C) during all tests. Each set of the huff-and-puff experiments was conducted by injecting CO2 in the fracture system surrounding the Core (injection step). Then, the system was shut-in for a period of 24 h to allow CO2 to diffuse from fracture into the oil in matrix (soaking period step). At the end of the soaking period, the pressure was released and the oil production was measured (production step). The above cycle was repeated until no more oil was produced. The results obtained show that when CO2 was injected at 1500 psi through a huff-and-puff process, it recovers more than 95% of oil from a fracture-matrix experimental model saturated with normal decane. Also indicates that at such a pressure, 45% of initial oil-in-place can be recovered during the first cycle. However, when CO2 was injected at pressures below CO2–nC10 minimum miscibility pressure (MMP), the maximum recovery factor achieved was less than 50%. Similarly, recovery factor of the first cycles performed at pressures below MMP were much lower (less than 30%) compare to those conducted at miscible condition. This indicates that miscible huff-and-puff process is a viable option for fractured porous media. As part of this study, effects of matrix Permeability, and connate water saturation on the performance of huff-and-puff process in fracture-matrix Core set-up at both immiscible and miscible conditions were studied. Results indicate that presence of connate water saturation is beneficial to immiscible CO2 huff-and-puff process while it has almost negligible effect on the performance of this process when performed at miscible conditions. In presence of connate water saturation more than 70% of oil-in-place was recovered at immiscible condition compare to a maximum of 45% recovered when matrix was 100% saturated with normal decane. Results of the tests performed in a Core with Permeability about 10 times higher than the original Core shows similar production trends. However, recovery factor in the high permeable Core was slightly less than twice of that in low permeable Core at immiscible condition. According to this study, effect of Core Permeability was less pronounced when CO2 was injected at miscible conditions.
-
effect of connate water saturation oil viscosity and matrix Permeability on rate of gravity drainage during immiscible and miscible displacement tests in matrix fracture experimental model
Journal of Canadian Petroleum Technology, 2009Co-Authors: Farshid Torabi, Koorosh AsghariAbstract:Miscible injection of carbon dioxide has seen a significant increase in interest for the purpose of enhanced oil recovery (EOR) in conventional oil reservoirs. However, naturally fractured reservoirs, which are among the largest oil reserves in the world, are considered poor candidates for this process because of presumed low-performance efficiency. This paper presents the results of an experimental study that explains the effect of connate water saturation, matrix Permeability and oil viscosity on the performance of gravity drainage from the matrix (into fracture) when it is surrounded by a CO 2 -filled fracture. Experiments were performed in an experimental model under different operating pressures to cover both immiscible and miscible conditions. Experiments were conducted using synthetic oil (nC 10 ) and light crude oil in two Berea Cores having large differences in Permeability. In addition, the effect of connate water saturation was studied by performing experiments in an initially brine-saturated Berea Core and comparing the results with those obtained when the Core was 100% saturated with oil. The experimental results showed that matrix Permeability had a significant effect on the rate of gravity drainage when CO 2 was injected under immiscible conditions. When experiments were performed at immiscible conditions, production rate by gravity drainage was nearly five times greater in the Berea Core with 1,000 md Permeability compared to the Core Permeability of 100 md. The production rates in the Cores investigated were similar at low pressures (below 3,400 kPa), but slightly higher for the higher-Permeability Core. As system pressure was increased beyond 3,400 kPa, the production rate from the higher-Permeability Core increased significantly, compared to the lower-Permeability case. Beyond miscibility conditions (~6,900 kPa), matrix Permeability was less significant, indicating the important role of capillary pressure in the gravity drainage mechanism. However, ultimate oil recovery was less sensitive to the matrix Permeability at pressures near or above minimum miscibility pressure. The observations were more interesting when experiments were performed in the presence of connate water saturation. The ultimate oil recovery from a Core saturated with oil in the presence of connate water saturation was less at immiscible conditions. However, at near-miscible and miscible conditions, the presence of connate water was beneficial to the gravity drainage mechanism in that it led to higher ultimate oil recovery. The effect of oil viscosity appeared to be important during the sustained miscibility of CO 2 and hydrocarbon phases. For the crude oil examined, the heavier components that remain in the oil phase after the vapourizing gas drive limited the length of the oil production period when compared with the nC 10 production. Miscible CO 2 injection in fractured reservoirs is a viable option for both oil recovery and storage purposes because as the residual oil saturation is reduced, additional pore volume (PV) becomes available to store CO 2 in its supercritical form. However, under immiscible conditions, when CO 2 is injected at pressures below the minimum miscibility pressure (MMP) and above the supercritical condition, it is not beneficial for improving oil recovery by gravity drainage. This was clearly seen when gravity drainage experiments using crude oil were performed and MMP was not achieved at the maximum possible operating pressures.
Farshid Torabi - One of the best experts on this subject based on the ideXlab platform.
-
Effect of operating pressure, matrix Permeability and connate water saturation on performance of CO2 huff-and-puff process in matrix-fracture experimental model
Fuel, 2010Co-Authors: Farshid Torabi, Koorosh AsghariAbstract:Abstract The main objective of study is to examine the performance and efficiency of CO2 huff-and-puff process for improving oil recovery and subsequent storage of CO2 in light-oil fractured porous media through designing and conducting targeted experiments. The experimental set-up consisted of a high-pressure stainless steel cell made specially to hold a cylindrical Core with spacing around it, simulating a matrix and its surrounding fracture environment. The matrix was saturated with normal decane, which was used as oil during the experiments. A total of six separate sets of huff-and-puff experiments, using CO2 as solvent, were conducted under operating pressures of 250, 500, 750, 1000, 1250, and 1500 psi. The temperature was kept constant (35 °C) during all tests. Each set of the huff-and-puff experiments was conducted by injecting CO2 in the fracture system surrounding the Core (injection step). Then, the system was shut-in for a period of 24 h to allow CO2 to diffuse from fracture into the oil in matrix (soaking period step). At the end of the soaking period, the pressure was released and the oil production was measured (production step). The above cycle was repeated until no more oil was produced. The results obtained show that when CO2 was injected at 1500 psi through a huff-and-puff process, it recovers more than 95% of oil from a fracture-matrix experimental model saturated with normal decane. Also indicates that at such a pressure, 45% of initial oil-in-place can be recovered during the first cycle. However, when CO2 was injected at pressures below CO2–nC10 minimum miscibility pressure (MMP), the maximum recovery factor achieved was less than 50%. Similarly, recovery factor of the first cycles performed at pressures below MMP were much lower (less than 30%) compare to those conducted at miscible condition. This indicates that miscible huff-and-puff process is a viable option for fractured porous media. As part of this study, effects of matrix Permeability, and connate water saturation on the performance of huff-and-puff process in fracture-matrix Core set-up at both immiscible and miscible conditions were studied. Results indicate that presence of connate water saturation is beneficial to immiscible CO2 huff-and-puff process while it has almost negligible effect on the performance of this process when performed at miscible conditions. In presence of connate water saturation more than 70% of oil-in-place was recovered at immiscible condition compare to a maximum of 45% recovered when matrix was 100% saturated with normal decane. Results of the tests performed in a Core with Permeability about 10 times higher than the original Core shows similar production trends. However, recovery factor in the high permeable Core was slightly less than twice of that in low permeable Core at immiscible condition. According to this study, effect of Core Permeability was less pronounced when CO2 was injected at miscible conditions.
-
effect of connate water saturation oil viscosity and matrix Permeability on rate of gravity drainage during immiscible and miscible displacement tests in matrix fracture experimental model
Journal of Canadian Petroleum Technology, 2009Co-Authors: Farshid Torabi, Koorosh AsghariAbstract:Miscible injection of carbon dioxide has seen a significant increase in interest for the purpose of enhanced oil recovery (EOR) in conventional oil reservoirs. However, naturally fractured reservoirs, which are among the largest oil reserves in the world, are considered poor candidates for this process because of presumed low-performance efficiency. This paper presents the results of an experimental study that explains the effect of connate water saturation, matrix Permeability and oil viscosity on the performance of gravity drainage from the matrix (into fracture) when it is surrounded by a CO 2 -filled fracture. Experiments were performed in an experimental model under different operating pressures to cover both immiscible and miscible conditions. Experiments were conducted using synthetic oil (nC 10 ) and light crude oil in two Berea Cores having large differences in Permeability. In addition, the effect of connate water saturation was studied by performing experiments in an initially brine-saturated Berea Core and comparing the results with those obtained when the Core was 100% saturated with oil. The experimental results showed that matrix Permeability had a significant effect on the rate of gravity drainage when CO 2 was injected under immiscible conditions. When experiments were performed at immiscible conditions, production rate by gravity drainage was nearly five times greater in the Berea Core with 1,000 md Permeability compared to the Core Permeability of 100 md. The production rates in the Cores investigated were similar at low pressures (below 3,400 kPa), but slightly higher for the higher-Permeability Core. As system pressure was increased beyond 3,400 kPa, the production rate from the higher-Permeability Core increased significantly, compared to the lower-Permeability case. Beyond miscibility conditions (~6,900 kPa), matrix Permeability was less significant, indicating the important role of capillary pressure in the gravity drainage mechanism. However, ultimate oil recovery was less sensitive to the matrix Permeability at pressures near or above minimum miscibility pressure. The observations were more interesting when experiments were performed in the presence of connate water saturation. The ultimate oil recovery from a Core saturated with oil in the presence of connate water saturation was less at immiscible conditions. However, at near-miscible and miscible conditions, the presence of connate water was beneficial to the gravity drainage mechanism in that it led to higher ultimate oil recovery. The effect of oil viscosity appeared to be important during the sustained miscibility of CO 2 and hydrocarbon phases. For the crude oil examined, the heavier components that remain in the oil phase after the vapourizing gas drive limited the length of the oil production period when compared with the nC 10 production. Miscible CO 2 injection in fractured reservoirs is a viable option for both oil recovery and storage purposes because as the residual oil saturation is reduced, additional pore volume (PV) becomes available to store CO 2 in its supercritical form. However, under immiscible conditions, when CO 2 is injected at pressures below the minimum miscibility pressure (MMP) and above the supercritical condition, it is not beneficial for improving oil recovery by gravity drainage. This was clearly seen when gravity drainage experiments using crude oil were performed and MMP was not achieved at the maximum possible operating pressures.
Cantarero Abad Irene - One of the best experts on this subject based on the ideXlab platform.
-
Deformation-fluid multiphase interaction within the fractures of the Barcelona Plain and the Vallès Basin: influence on fault rocks and diagenesis / Interacció multifàsica entre deformació i fluids a les fractures del Pla de Barcelona i de la Conca d
'Edicions de la Universitat de Barcelona', 2013Co-Authors: Cantarero Abad IreneAbstract:The faults limiting the Barcelona Plain and the Vallès Half-graben (Catalan Coastal Ranges, NE Spain) have allowed the study of a complex and multiphase tectonic/fluid history from the Hercynian to recent times. Furthermore, this study has allowed to define the factors that control the fluid regime and the fluid flow pathways through faults. A multidisciplinary methodology involving field and petrological observations and microstructural analyses combined with geochemical data has been used to characterize host rocks, fault rocks and fracture-related cements. Four tectonic events that encompass seven deformation phases have been established: Hercynian compression, Mesozoic extension (D1-D2), Paleogene compression (D3) and Neogene extension (D4-D7). Faults affect crystalline Hercynian basement, Triassic dolostones and Miocene detritic rocks. The fault rocks formed in the area include gouges, cataclasites, breccias and pseudotachylytes. Veins are formed by different mineral assemblages that involve calcite, quartz, laumontite, K-white mica, chlorite and iron oxides, depending on the PT conditions and thus, on the age. During the exhumation of the late-Hercynian granodiorite, after the Hercynian compression, M1 and M2 muscovite and microcline crystallized as result of deuteric alteration in joints, at temperatures between 330ºC and 370ºC. During the first Mesozoic rifting (Late Permian-Middle Jurassic), faults controlled the thickness and distribution of the Triassic sediments. Fracture-related dolomite cements precipitated from the Triassic seawater during increasing burial in a relatively closed hydrological regime. The second Mesozoic rifting (Late Jurassic-Late Cretaceous) is characterized by precipitation of M3 and M4 phengite together with chlorite and calcite C1 at temperatures between 190 and 310ºC. During the Paleogene compression, low-temperature meteoric fluids, favored by tectonic uplift, produced calcitization of the Triassic dolomite cements and dolostones. In the Vallès fault, by means of a shortcut, Mesozoic structures were uplifted and a gouge and subvertical stylolites were generated. During the Neogene syn-rift, hydrothermal fluids up to 190ºC ascended through the faults. In the Hospital fault these fluids upflowed within the relay area during fault growth by tip propagation due to a seismic pumping effect. The Neogene post-rift in the Barcelona Plain developed at shallow conditions under low-temperature meteoric regime. At the same period, the Vallès fault was dominated by hydrothermal conditions, which remain active until nowadays. Faults acted as conduits for hot fluids during both Mesozoic and Neogene extensional events. Topographically-driven meteoric fluids warmed at depth and suffered a strong interaction with the host rocks. During the Mesozoic, ascending warm fluids mixed with marine waters in both main faults whereas, during the Neogene, the ascending fluids mixed with marine waters in the Hospital fault and with meteoric waters in the Vallès fault. Pedogenic products precipitated along Neogene faults control cross-fault fluid flow by reducing fault Core Permeability. This work highlights the presence of fault reactivation from Hercynian to Recent times. Hercynian structures have demonstrated to play an important role on the localization of later structures. The main factors that control this process are: fault orientation, fabric softening, fluid pressure and cementation hardening.Las fallas que limitan el Llano de Barcelona y la Cuenca del Vallès permiten estudiar la relación entre tectónica y fluidos desde el Hercínico hasta la actualidad. Observaciones de micro- a meso-escala combinadas con análisis geoquímicos han servido para caracterizar las rocas encajantes, las rocas de falla y los cementos. Las fallas afectan a rocas cristalinas Hercínicas, dolomías Triásicas y rocas detríticas Miocenas y generan “gouges”, cataclasitas, brechas y pseudotaquilitas. Los principales cementos son de calcita, cuarzo, laumontita, mica blanca, clorita y óxidos de hierro, dependiendo de las condiciones P-T. Se han establecido cuatro eventos tectónicos que recogen siete fases deformativas: 1) Durante la exhumación de la granodiorita tardihercínica cristalizaron moscovitas M1-M2 en diaclasas debido a un proceso de alteración deutérica a temperaturas entre 330ºC y 370ºC. 2) Durante el primer rift mesozoico, las fallas controlaron el grosor y la distribución de los sedimentos triásicos. Cementos dolomíticos precipitaron en fracturas a partir de agua marina triásica durante un incremento del enterramiento en un sistema hidrológico cerrado. El segundo rift se caracterizó por la precipitación de mica M3- M4, clorita y calcita a temperaturas entre 190-310ºC. 3) Durante la compresión Paleógena, fluidos meteóricos de baja temperatura calcitizaron los cementos dolomíticos triásicos y las dolomías encajantes. En la falla del Vallès, un “shortcut” levantó las estructuras Mesozoicas y generó una “gouge” y estilolitos subverticales. 4) Durante el sinrift Neógeno, fluidos de hasta 190ºC ascendieron por las fallas. En la falla del Hospital, estos fluidos ascendieron en la zona de relevo durante la propagación de la falla gracias a un efecto de bombeo sísmico. El postrift Neógeno se desarrolló en condiciones someras bajo un régimen meteórico de baja temperatura en el Llano de Barcelona. En el mismo periodo, la falla del Vallès estuvo dominada por fluidos hidrotermales. Las principales estructuras que configuran las Cadenas Costero Catalanas han sido reactivadas desde el Hercínico hasta la actualidad. Las estructuras hercínicas jugaron un papel importante en la localización de estructuras posteriores. Los principales factores que controlaron las sucesivas reactivaciones fueron: la orientación de las fracturas, la fábrica mineral, la presión de fluidos y las cementaciones previas
-
Deformation-fluid multiphase interaction within the fractures of the Barcelona Plain and the Vallès Basin: influence on fault rocks and diagenesis / Interacció multifàsica entre deformació i fluids a les fractures del Pla de Barcelona i de la Conca d
'Edicions de la Universitat de Barcelona', 2013Co-Authors: Cantarero Abad IreneAbstract:[eng] The faults limiting the Barcelona Plain and the Vallès Half-graben (Catalan Coastal Ranges, NE Spain) have allowed the study of a complex and multiphase tectonic/fluid history from the Hercynian to recent times. Furthermore, this study has allowed to define the factors that control the fluid regime and the fluid flow pathways through faults. A multidisciplinary methodology involving field and petrological observations and microstructural analyses combined with geochemical data has been used to characterize host rocks, fault rocks and fracture-related cements. Four tectonic events that encompass seven deformation phases have been established: Hercynian compression, Mesozoic extension (D1-D2), Paleogene compression (D3) and Neogene extension (D4-D7). Faults affect crystalline Hercynian basement, Triassic dolostones and Miocene detritic rocks. The fault rocks formed in the area include gouges, cataclasites, breccias and pseudotachylytes. Veins are formed by different mineral assemblages that involve calcite, quartz, laumontite, K-white mica, chlorite and iron oxides, depending on the PT conditions and thus, on the age. During the exhumation of the late-Hercynian granodiorite, after the Hercynian compression, M1 and M2 muscovite and microcline crystallized as result of deuteric alteration in joints, at temperatures between 330ºC and 370ºC. During the first Mesozoic rifting (Late Permian-Middle Jurassic), faults controlled the thickness and distribution of the Triassic sediments. Fracture-related dolomite cements precipitated from the Triassic seawater during increasing burial in a relatively closed hydrological regime. The second Mesozoic rifting (Late Jurassic-Late Cretaceous) is characterized by precipitation of M3 and M4 phengite together with chlorite and calcite C1 at temperatures between 190 and 310ºC. During the Paleogene compression, low-temperature meteoric fluids, favored by tectonic uplift, produced calcitization of the Triassic dolomite cements and dolostones. In the Vallès fault, by means of a shortcut, Mesozoic structures were uplifted and a gouge and subvertical stylolites were generated. During the Neogene syn-rift, hydrothermal fluids up to 190ºC ascended through the faults. In the Hospital fault these fluids upflowed within the relay area during fault growth by tip propagation due to a seismic pumping effect. The Neogene post-rift in the Barcelona Plain developed at shallow conditions under low-temperature meteoric regime. At the same period, the Vallès fault was dominated by hydrothermal conditions, which remain active until nowadays. Faults acted as conduits for hot fluids during both Mesozoic and Neogene extensional events. Topographically-driven meteoric fluids warmed at depth and suffered a strong interaction with the host rocks. During the Mesozoic, ascending warm fluids mixed with marine waters in both main faults whereas, during the Neogene, the ascending fluids mixed with marine waters in the Hospital fault and with meteoric waters in the Vallès fault. Pedogenic products precipitated along Neogene faults control cross-fault fluid flow by reducing fault Core Permeability. This work highlights the presence of fault reactivation from Hercynian to Recent times. Hercynian structures have demonstrated to play an important role on the localization of later structures. The main factors that control this process are: fault orientation, fabric softening, fluid pressure and cementation hardening.[spa] Las fallas que limitan el Llano de Barcelona y la Cuenca del Vallès permiten estudiar la relación entre tectónica y fluidos desde el Hercínico hasta la actualidad. Observaciones de micro- a meso-escala combinadas con análisis geoquímicos han servido para caracterizar las rocas encajantes, las rocas de falla y los cementos. Las fallas afectan a rocas cristalinas Hercínicas, dolomías Triásicas y rocas detríticas Miocenas y generan “gouges”, cataclasitas, brechas y pseudotaquilitas. Los principales cementos son de calcita, cuarzo, laumontita, mica blanca, clorita y óxidos de hierro, dependiendo de las condiciones P-T. Se han establecido cuatro eventos tectónicos que recogen siete fases deformativas: 1) Durante la exhumación de la granodiorita tardihercínica cristalizaron moscovitas M1-M2 en diaclasas debido a un proceso de alteración deutérica a temperaturas entre 330ºC y 370ºC. 2) Durante el primer rift mesozoico, las fallas controlaron el grosor y la distribución de los sedimentos triásicos. Cementos dolomíticos precipitaron en fracturas a partir de agua marina triásica durante un incremento del enterramiento en un sistema hidrológico cerrado. El segundo rift se caracterizó por la precipitación de mica M3- M4, clorita y calcita a temperaturas entre 190-310ºC. 3) Durante la compresión Paleógena, fluidos meteóricos de baja temperatura calcitizaron los cementos dolomíticos triásicos y las dolomías encajantes. En la falla del Vallès, un “shortcut” levantó las estructuras Mesozoicas y generó una “gouge” y estilolitos subverticales. 4) Durante el sinrift Neógeno, fluidos de hasta 190ºC ascendieron por las fallas. En la falla del Hospital, estos fluidos ascendieron en la zona de relevo durante la propagación de la falla gracias a un efecto de bombeo sísmico. El postrift Neógeno se desarrolló en condiciones someras bajo un régimen meteórico de baja temperatura en el Llano de Barcelona. En el mismo periodo, la falla del Vallès estuvo dominada por fluidos hidrotermales. Las principales estructuras que configuran las Cadenas Costero Catalanas han sido reactivadas desde el Hercínico hasta la actualidad. Las estructuras hercínicas jugaron un papel importante en la localización de estructuras posteriores. Los principales factores que controlaron las sucesivas reactivaciones fueron: la orientación de las fracturas, la fábrica mineral, la presión de fluidos y las cementaciones previas
Jianhui Zeng - One of the best experts on this subject based on the ideXlab platform.
-
the experimental modeling of gas percolation mechanisms in a coal measure tight sandstone reservoir a case study on the coal measure tight sandstone gas in the upper triassic xujiahe formation sichuan basin china
Natural Gas Geoscience, 2016Co-Authors: Shizhen Tao, Jianhui Zeng, Xiaohui Gao, Xiangxiang Zhang, Chun Yang, Jingya Zhang, Yanjie GongAbstract:Abstract Tight sandstone gas from coal-measure source rock is widespread in China, and it is represented by the Xujiahe Formation of the Sichuan Basin and the Upper Paleozoic of the Ordos Basin. It is affected by planar evaporative hydrocarbon expulsion of coal-measure source rock and the gentle structural background; hydrodynamics and buoyancy play a limited role in the gas migration-accumulation in tight sandstone. Under the conditions of low Permeability and speed, non-Darcy flow is quite apparent, it gives rise to gas-water mixed gas zone. In the gas displacing water experiment, the shape of percolation flow curve is mainly influenced by Core Permeability. The lower the Permeability, the higher the starting pressure gradient as well as the more evident the non-Darcy phenomenon will be. In the gas displacing water experiment of tight sandstone, the maximum gas saturation of the Core is generally less than 50% (ranging from 30% to 40% and averaging at 38%); it is similar to the actual gas saturation of the gas zone in the subsurface Core. The gas saturation and Permeability of the Core have a logarithm correlation with a correlation coefficient of 0.8915. In the single-phase flow of tight sandstone gas, low-velocity non-Darcy percolation is apparent; the initial flow velocity (Vd) exists due to the slippage effect of gas flow. The shape of percolation flow curve of a single-phase gas is primarily controlled by Core Permeability and confining pressure; the lower the Permeability or the higher the confining pressure, the higher the starting pressure (0.02–0.08 MPa/cm), whereas, the higher the quasi-initial flow speed, the longer the nonlinear section and the more obvious the non-Darcy flow will be. The tight sandstone gas seepage mechanism study shows that the lower the reservoir Permeability, the higher the starting pressure and the slower the flow velocity will be, this results in the low efficiency of natural gas migration and accumulation as well as low gas saturation. The laboratory modeling on gas migration accumulation mechanism in coal-measure tight sandstone can provide a theoretic foundation to reveal the tight sandstone gas enrichment regularity, evaluation of prospecting area, and the study of development mechanism.
-
non darcy flow in oil accumulation oil displacing water and relative Permeability and oil saturation characteristics of low Permeability sandstones
Petroleum Science, 2010Co-Authors: Jianhui Zeng, Shiwei Cheng, Xu Kong, Hongyu WangAbstract:Hydrocarbon resources in low-Permeability sandstones are very abundant and are extensively distributed. Low-Permeability reservoirs show several unique characteristics, including lack of a definite trap boundary or caprock, limited buoyancy effect, complex oil-gas-water distribution, without obvious oil-gas-water interfaces, and relatively low oil (gas) saturation. Based on the simulation experiments of oil accumulation in low-Permeability sandstone (oil displacing water), we study the migration and accumulation characteristics of non-Darcy oil flow, and discuss the values and influencing factors of relative Permeability which is a key parameter characterizing oil migration and accumulation in low-Permeability sandstone. The results indicate that: 1) Oil migration (oil displacing water) in low-Permeability sandstone shows non-Darcy percolation characteristics, and there is a threshold pressure gradient during oil migration and accumulation, which has a good negative correlation with Permeability and apparent fluidity; 2) With decrease of Permeability and apparent fluidity and increase of fluid viscosity, the percolation curve is closer to the pressure gradient axis and the threshold pressure gradient increases. When the apparent fluidity is more than 1.0, the percolation curve shows modified Darcy flow characteristics, while when the apparent fluidity is less than 1.0, the percolation curve is a “concaveup” non-Darcy percolation curve; 3) Oil-water two-phase relative Permeability is affected by Core Permeability, fluid viscosity, apparent fluidity, and injection drive force; 4) The oil saturation of low-Permeability sandstone reservoirs is mostly within 35%–60%, and the oil saturation also has a good positive correlation with the Permeability and apparent fluidity.
Yanjie Gong - One of the best experts on this subject based on the ideXlab platform.
-
the experimental modeling of gas percolation mechanisms in a coal measure tight sandstone reservoir a case study on the coal measure tight sandstone gas in the upper triassic xujiahe formation sichuan basin china
Natural Gas Geoscience, 2016Co-Authors: Shizhen Tao, Jianhui Zeng, Xiaohui Gao, Xiangxiang Zhang, Chun Yang, Jingya Zhang, Yanjie GongAbstract:Abstract Tight sandstone gas from coal-measure source rock is widespread in China, and it is represented by the Xujiahe Formation of the Sichuan Basin and the Upper Paleozoic of the Ordos Basin. It is affected by planar evaporative hydrocarbon expulsion of coal-measure source rock and the gentle structural background; hydrodynamics and buoyancy play a limited role in the gas migration-accumulation in tight sandstone. Under the conditions of low Permeability and speed, non-Darcy flow is quite apparent, it gives rise to gas-water mixed gas zone. In the gas displacing water experiment, the shape of percolation flow curve is mainly influenced by Core Permeability. The lower the Permeability, the higher the starting pressure gradient as well as the more evident the non-Darcy phenomenon will be. In the gas displacing water experiment of tight sandstone, the maximum gas saturation of the Core is generally less than 50% (ranging from 30% to 40% and averaging at 38%); it is similar to the actual gas saturation of the gas zone in the subsurface Core. The gas saturation and Permeability of the Core have a logarithm correlation with a correlation coefficient of 0.8915. In the single-phase flow of tight sandstone gas, low-velocity non-Darcy percolation is apparent; the initial flow velocity (Vd) exists due to the slippage effect of gas flow. The shape of percolation flow curve of a single-phase gas is primarily controlled by Core Permeability and confining pressure; the lower the Permeability or the higher the confining pressure, the higher the starting pressure (0.02–0.08 MPa/cm), whereas, the higher the quasi-initial flow speed, the longer the nonlinear section and the more obvious the non-Darcy flow will be. The tight sandstone gas seepage mechanism study shows that the lower the reservoir Permeability, the higher the starting pressure and the slower the flow velocity will be, this results in the low efficiency of natural gas migration and accumulation as well as low gas saturation. The laboratory modeling on gas migration accumulation mechanism in coal-measure tight sandstone can provide a theoretic foundation to reveal the tight sandstone gas enrichment regularity, evaluation of prospecting area, and the study of development mechanism.