In the Tuoshi oilfield, located in the Cenozoic Jianghan Basin of southeastern China, there have been found hydrocarbon reservoirs hosted in lacustrine sandstones of the Eogene Xingouzui Formation. The main diagenetic...In the Tuoshi oilfield, located in the Cenozoic Jianghan Basin of southeastern China, there have been found hydrocarbon reservoirs hosted in lacustrine sandstones of the Eogene Xingouzui Formation. The main diagenetic features identified in these sandstones include the dissolution of detrital K\|feldspar and albite grains, the precipitation of quartz as overgrowths and/or cements, and the precipitation and/or transformation of clay minerals. These diagenetic features were interpreted to have occurred in early, intermediate and late stages, based on the burial depth. The kinetics of fluid\|mineral reactions and the concentrations of aqueous species at each stage of diagenesis were simulated numerically for these lacustrine sandstones, using a quasi\|stationary state approximation that incorporates simultaneous chemical reactions in a time\|space continuum. During the early diagenetic stage, pore fluid was weakly acidic, which resulted in dissolution of K\|feldspar and albite and, therefore, led to the release of K\++, Na\++, Al\+ 3+ and SiO\- 2(aq) into the diagenetic fluid. The increased K\++, Na\++, Al\+ 3+ and SiO\- 2(aq) concentrations in the diagenetic fluid caused the precipitation of quartz, kaolinite and illite. At the beginning of the intermediate diagenetic stage the concentration of H\++ was built up due to the decomposition of organic matter, which was responsible for further dissolution of K\|feldspar and albite and precipitation of quartz, kaolinite, and illite. During the late diagenetic stage, the pore fluid was weakly alkaline, K\|feldspar became stable and was precipitated with quartz and clay minerals. When the burial depth was greater than 3000 m, the pore fluids became supersaturated with respect to albite, but undersaturated with respect to quartz, resulting in the precipitation of albite and the dissolution of quartz. The diagenetic reactions forecasted in the numerical modeling closely matched the diagenetic features identified by petrographic examination, and therefore, can help us to gain a better understanding of the diagenetic processes and associated porosity evolution in sandstone reservoirs .展开更多
Stress sensitivity is a key factor affecting the productivity of single wells in low permeability gas reservoirs. A well test model for heterogeneous composite gas reservoirs under the influence of stress-sensitive ef...Stress sensitivity is a key factor affecting the productivity of single wells in low permeability gas reservoirs. A well test model for heterogeneous composite gas reservoirs under the influence of stress-sensitive effects was established. Based on the theoretical model, the well test was designed by gradually increasing the pressure difference. The relationship between abnormal high pressure and reservoir stress sensitivity was analyzed. Theoretical research shows that stress sensitivity will cause permeability damage during the production process, and the pressure drop test curve shows that the physical properties of the reservoir have gradually deteriorated. The pressure recovery test curve shows that the physical properties of the reservoir are getting better. Field practice shows that stress sensitivity is related to the formation of abnormally high pressure in the formation without considering the micro-cracks in the formation. Stress-sensitive reservoirs are generally unbalanced and compacted due to overpressure, for fluid expansion/conduction overpressure in Ledong Area. For these reservoirs, there is almost no stress sensitivity. The research results have significance for guiding the design and data interpretation of stress-sensitive reservoir.展开更多
Undoubtedly, plenty of hydrocarbon sources are located in carbonate rocks, particularly those which are naturally fractured that is still needed to study their characterization, because of their complex and unconventi...Undoubtedly, plenty of hydrocarbon sources are located in carbonate rocks, particularly those which are naturally fractured that is still needed to study their characterization, because of their complex and unconventional behavior. Therefore, applying any processes that cause Enhancing Oil Recovery (EOR) from Naturally Fractured Reservoirs (NFR) seems necessary and useful. However, selecting the best developed scenario is always challenging. Screening criteria would determine the possibility of implementing an EOR process. While, utilizing trade marketing simulators can solve this problem. Moreover, simulation can evaluate other parameters such as water cut and gas-oil ratio. In this research, an aquifer-supported Iranian NFR with two parts that are separated to each other with a shale layer is considered in order to select the best EOR scenario. The fluid model is created using PVTi software. Various production scenarios included natural depletion, water flooding, miscible carbon dioxide injection, water-alternating-gas (WAG) injection, simultaneous water- alternating-gas (SWAG) injection, hybrid injection, and gas recycling are simulated in ECLIPSE Compositional (E300) and their recovery factor recorded as the target parameter. The developed scenarios are designed in a way that gives the optimized results, i.e. higher recovery factor, less water cut as well as the less gas-oil ratio. As a result, SWAG shows better conditions and is recommended for the further studies of the reservoir management plan in the future. Also, the role of the aquifer in the SWAG scenario is positive by creating a natural WAG in addition to the SWAG. Additionally, the average reservoir pressure through fractures reduces less in the SWAG than the other Scenarios, the oil and gas production rate reduce less in the SWAG and SWAG/ miscible gas respectively than the other scenarios. The maximum and the minimum water cut are related to the water flooding and SWAG, respectively.Finally, the simulation approach of EOR screening in NFR is better than other approaches, from the perspective of economic issues as well as the simplicity of the methods.展开更多
塔河油田奥陶系油气藏储层非均质性极强,烃源岩长期生排烃、多期充注成藏及混合改造,导致油气性质变化大,给流体识别带来巨大挑战。通过模型正演,分析缝洞型储层厚度、孔隙度、含流体性质对AVO特征的影响,明确气藏、轻质油藏、重质油藏...塔河油田奥陶系油气藏储层非均质性极强,烃源岩长期生排烃、多期充注成藏及混合改造,导致油气性质变化大,给流体识别带来巨大挑战。通过模型正演,分析缝洞型储层厚度、孔隙度、含流体性质对AVO特征的影响,明确气藏、轻质油藏、重质油藏三种不同类型油气藏的AVO特征及敏感参数;在此基础上,开展叠前反演,获得地下不同流体纵波阻抗及纵横波速度比特征,然后基于实际测井数据,建立三种不同类型油气藏岩石物理量版,在岩石物理量版指导下,利用双参数进行流体概率分析,获得缝洞储层流体定量识别结果。对塔河A区(气藏)、B区(轻质油藏)和C区(重质油藏),各50 km 2三维地震资料开展基于叠前AVO反演的流体识别应用研究,将识别结果用于盲井检验,气藏识别符合率为80%,轻质油藏符合率为76%,重质油藏符合率为72%。研究结果为塔河碳酸盐岩储层流体识别提供了参考依据。展开更多
基金This project was funded by the National Natural science Foundation of China (GrantNo .4 91 330 80 ) and by the Trans centuryTraining Program me Foudation for the Talentssponsored by the State Education Commission of China
文摘In the Tuoshi oilfield, located in the Cenozoic Jianghan Basin of southeastern China, there have been found hydrocarbon reservoirs hosted in lacustrine sandstones of the Eogene Xingouzui Formation. The main diagenetic features identified in these sandstones include the dissolution of detrital K\|feldspar and albite grains, the precipitation of quartz as overgrowths and/or cements, and the precipitation and/or transformation of clay minerals. These diagenetic features were interpreted to have occurred in early, intermediate and late stages, based on the burial depth. The kinetics of fluid\|mineral reactions and the concentrations of aqueous species at each stage of diagenesis were simulated numerically for these lacustrine sandstones, using a quasi\|stationary state approximation that incorporates simultaneous chemical reactions in a time\|space continuum. During the early diagenetic stage, pore fluid was weakly acidic, which resulted in dissolution of K\|feldspar and albite and, therefore, led to the release of K\++, Na\++, Al\+ 3+ and SiO\- 2(aq) into the diagenetic fluid. The increased K\++, Na\++, Al\+ 3+ and SiO\- 2(aq) concentrations in the diagenetic fluid caused the precipitation of quartz, kaolinite and illite. At the beginning of the intermediate diagenetic stage the concentration of H\++ was built up due to the decomposition of organic matter, which was responsible for further dissolution of K\|feldspar and albite and precipitation of quartz, kaolinite, and illite. During the late diagenetic stage, the pore fluid was weakly alkaline, K\|feldspar became stable and was precipitated with quartz and clay minerals. When the burial depth was greater than 3000 m, the pore fluids became supersaturated with respect to albite, but undersaturated with respect to quartz, resulting in the precipitation of albite and the dissolution of quartz. The diagenetic reactions forecasted in the numerical modeling closely matched the diagenetic features identified by petrographic examination, and therefore, can help us to gain a better understanding of the diagenetic processes and associated porosity evolution in sandstone reservoirs .
文摘Stress sensitivity is a key factor affecting the productivity of single wells in low permeability gas reservoirs. A well test model for heterogeneous composite gas reservoirs under the influence of stress-sensitive effects was established. Based on the theoretical model, the well test was designed by gradually increasing the pressure difference. The relationship between abnormal high pressure and reservoir stress sensitivity was analyzed. Theoretical research shows that stress sensitivity will cause permeability damage during the production process, and the pressure drop test curve shows that the physical properties of the reservoir have gradually deteriorated. The pressure recovery test curve shows that the physical properties of the reservoir are getting better. Field practice shows that stress sensitivity is related to the formation of abnormally high pressure in the formation without considering the micro-cracks in the formation. Stress-sensitive reservoirs are generally unbalanced and compacted due to overpressure, for fluid expansion/conduction overpressure in Ledong Area. For these reservoirs, there is almost no stress sensitivity. The research results have significance for guiding the design and data interpretation of stress-sensitive reservoir.
文摘Undoubtedly, plenty of hydrocarbon sources are located in carbonate rocks, particularly those which are naturally fractured that is still needed to study their characterization, because of their complex and unconventional behavior. Therefore, applying any processes that cause Enhancing Oil Recovery (EOR) from Naturally Fractured Reservoirs (NFR) seems necessary and useful. However, selecting the best developed scenario is always challenging. Screening criteria would determine the possibility of implementing an EOR process. While, utilizing trade marketing simulators can solve this problem. Moreover, simulation can evaluate other parameters such as water cut and gas-oil ratio. In this research, an aquifer-supported Iranian NFR with two parts that are separated to each other with a shale layer is considered in order to select the best EOR scenario. The fluid model is created using PVTi software. Various production scenarios included natural depletion, water flooding, miscible carbon dioxide injection, water-alternating-gas (WAG) injection, simultaneous water- alternating-gas (SWAG) injection, hybrid injection, and gas recycling are simulated in ECLIPSE Compositional (E300) and their recovery factor recorded as the target parameter. The developed scenarios are designed in a way that gives the optimized results, i.e. higher recovery factor, less water cut as well as the less gas-oil ratio. As a result, SWAG shows better conditions and is recommended for the further studies of the reservoir management plan in the future. Also, the role of the aquifer in the SWAG scenario is positive by creating a natural WAG in addition to the SWAG. Additionally, the average reservoir pressure through fractures reduces less in the SWAG than the other Scenarios, the oil and gas production rate reduce less in the SWAG and SWAG/ miscible gas respectively than the other scenarios. The maximum and the minimum water cut are related to the water flooding and SWAG, respectively.Finally, the simulation approach of EOR screening in NFR is better than other approaches, from the perspective of economic issues as well as the simplicity of the methods.
文摘塔河油田奥陶系油气藏储层非均质性极强,烃源岩长期生排烃、多期充注成藏及混合改造,导致油气性质变化大,给流体识别带来巨大挑战。通过模型正演,分析缝洞型储层厚度、孔隙度、含流体性质对AVO特征的影响,明确气藏、轻质油藏、重质油藏三种不同类型油气藏的AVO特征及敏感参数;在此基础上,开展叠前反演,获得地下不同流体纵波阻抗及纵横波速度比特征,然后基于实际测井数据,建立三种不同类型油气藏岩石物理量版,在岩石物理量版指导下,利用双参数进行流体概率分析,获得缝洞储层流体定量识别结果。对塔河A区(气藏)、B区(轻质油藏)和C区(重质油藏),各50 km 2三维地震资料开展基于叠前AVO反演的流体识别应用研究,将识别结果用于盲井检验,气藏识别符合率为80%,轻质油藏符合率为76%,重质油藏符合率为72%。研究结果为塔河碳酸盐岩储层流体识别提供了参考依据。
