Research and development of water lock inhibiting measures is very crucial in verifying the link mechanism between the internal factors of water lock and its extent of damage.Based on conventional water-lock physics e...Research and development of water lock inhibiting measures is very crucial in verifying the link mechanism between the internal factors of water lock and its extent of damage.Based on conventional water-lock physics experiments,however,only the consequence of macro water lock damage can be investigated,while the microscopic mechanism cannot be studied.In this paper,3D digital cores of low-permeability sandstones were prepared by means of high-resolution micro-CT scan,and their equivalent pore network model was built as well.Virtual“imbibition”experiments controlled by capillary force were carried out by using pore-scale flow simulation.Then the link mechanism between the microscopic internal factors(e.g.wettability,water saturation and pore-throat structure parameters)and the water-lock damage degree was discussed.It is shown that the damage degree of water lock reduces gradually as the wettability transits from water wet to gas wet.Therefore,the water lock damage can be reduced effectively and gas-well productivity can be improved so long as the capillary environment is changed from strong water wettability to weak gas wettability.The more different the initial water saturation is from the irreducible water saturation,the more serious the water lock damage is.The damage degree of water lock is in a negative correlation with the coordinate number,but a positive correlation with the poreethroat ratio.Based on the existing research results,water lock tends to form in the formations composed of mediumsized throats.It is concluded that there is a critical throat radius,at which the water lock is the most serious.展开更多
Experimental results from the Daniudi gas field enhance our understanding of mechanisms behind CO_(2) injection for enhanced recovery from tight-sand gas reservoirs.The results reveal that the diffusion coefficients o...Experimental results from the Daniudi gas field enhance our understanding of mechanisms behind CO_(2) injection for enhanced recovery from tight-sand gas reservoirs.The results reveal that the diffusion coefficients of CO_(2) in tight reservoirs range from 10-8m2/s to 10-9m2/s,correlating negatively with pore pressure and positively with pore radius.In these reservoirs,CO_(2) manifests a significantly higher adsorption capability compared to CH4,suggesting a competitive adsorption advantage.Further,the amount of adsorbed gas correlates negatively with core permeability and positively with pore pressure.In the late-stage depletion-drive development of tight-sand gas reservoirs,CO_(2) injection alleviates water locking and enhances gas-water flow,facilitating the recovery of trapped gas.The long-core CO_(2) flooding experiment results in a 14.11%increase in gas recovery efficiency.The effectiveness of CO_(2) -enhanced gas recovery (EGR) is primarily related to reservoir properties.Higher average permeability correlates with more effective CO_(2) -EGR.Although the rate and mode of injection have limited impacts on ultimate recovery efficiency,they influence CO_(2) breakthrough time.Specifically,a higher injection rate leads to earlier breakthrough,and the breakthrough under pulsed CO_(2) injection occurs later than that under continuous injection.展开更多
By means of the pore-level simulation, the characteristics of gas-water flow and gas-water distribution during the alternative displacement of gas and water were observed directly from etched-glass micromodel. The res...By means of the pore-level simulation, the characteristics of gas-water flow and gas-water distribution during the alternative displacement of gas and water were observed directly from etched-glass micromodel. The results show that gas-water distribution styles are divided into continuous phase type and separate phase type. The water lock exists in pore and throat during the process of gas-water displacement, and it reduces the gas flow-rate and has some effects on the recovery efficiency during the operation of gas storage. According to the experimental results of aquifer gas storage in X area, the differences in available extent among reservoirs are significant, and the availability of pore space is 33% 45%.展开更多
基金Project supported by the National Natural Science Foundation of China for the Youth,“Study on the Effect of Shale Bedding Architecture on Features of Ultrasonic Wave and Its Application”(No.41502287)the S&T Program of Chongqing Land and Resources Bureau“Evaluation on Gas Saturation in Shale based on Digital Core Technology”(No.CQGT-KJ-2015018)Sinopec Key Geophysical Laboratory Open Fund Project“Apparent Characteristics of Shale Reservoir and Digital Rock Physics Laboratory Study”(No.33550006-15-FW2099-0015).
文摘Research and development of water lock inhibiting measures is very crucial in verifying the link mechanism between the internal factors of water lock and its extent of damage.Based on conventional water-lock physics experiments,however,only the consequence of macro water lock damage can be investigated,while the microscopic mechanism cannot be studied.In this paper,3D digital cores of low-permeability sandstones were prepared by means of high-resolution micro-CT scan,and their equivalent pore network model was built as well.Virtual“imbibition”experiments controlled by capillary force were carried out by using pore-scale flow simulation.Then the link mechanism between the microscopic internal factors(e.g.wettability,water saturation and pore-throat structure parameters)and the water-lock damage degree was discussed.It is shown that the damage degree of water lock reduces gradually as the wettability transits from water wet to gas wet.Therefore,the water lock damage can be reduced effectively and gas-well productivity can be improved so long as the capillary environment is changed from strong water wettability to weak gas wettability.The more different the initial water saturation is from the irreducible water saturation,the more serious the water lock damage is.The damage degree of water lock is in a negative correlation with the coordinate number,but a positive correlation with the poreethroat ratio.Based on the existing research results,water lock tends to form in the formations composed of mediumsized throats.It is concluded that there is a critical throat radius,at which the water lock is the most serious.
基金funded by Basic Research Project of SINOPEC (P22202)。
文摘Experimental results from the Daniudi gas field enhance our understanding of mechanisms behind CO_(2) injection for enhanced recovery from tight-sand gas reservoirs.The results reveal that the diffusion coefficients of CO_(2) in tight reservoirs range from 10-8m2/s to 10-9m2/s,correlating negatively with pore pressure and positively with pore radius.In these reservoirs,CO_(2) manifests a significantly higher adsorption capability compared to CH4,suggesting a competitive adsorption advantage.Further,the amount of adsorbed gas correlates negatively with core permeability and positively with pore pressure.In the late-stage depletion-drive development of tight-sand gas reservoirs,CO_(2) injection alleviates water locking and enhances gas-water flow,facilitating the recovery of trapped gas.The long-core CO_(2) flooding experiment results in a 14.11%increase in gas recovery efficiency.The effectiveness of CO_(2) -enhanced gas recovery (EGR) is primarily related to reservoir properties.Higher average permeability correlates with more effective CO_(2) -EGR.Although the rate and mode of injection have limited impacts on ultimate recovery efficiency,they influence CO_(2) breakthrough time.Specifically,a higher injection rate leads to earlier breakthrough,and the breakthrough under pulsed CO_(2) injection occurs later than that under continuous injection.
基金Project(2011ZX05013-002)supported by National Science and Technology Major Projects of China
文摘By means of the pore-level simulation, the characteristics of gas-water flow and gas-water distribution during the alternative displacement of gas and water were observed directly from etched-glass micromodel. The results show that gas-water distribution styles are divided into continuous phase type and separate phase type. The water lock exists in pore and throat during the process of gas-water displacement, and it reduces the gas flow-rate and has some effects on the recovery efficiency during the operation of gas storage. According to the experimental results of aquifer gas storage in X area, the differences in available extent among reservoirs are significant, and the availability of pore space is 33% 45%.
