Dynamic imbibition,which is significantly affected by flow rate,plays an important role in the development of tight oil.This study investigated the impact of flow rate on dynamic imbibition in fractured tight sandston...Dynamic imbibition,which is significantly affected by flow rate,plays an important role in the development of tight oil.This study investigated the impact of flow rate on dynamic imbibition in fractured tight sandstone cores via online nuclear magnetic resonance core-flooding experiments.The oil expulsion efficiency and capillary number of multiscale pores were quantitatively analyzed to elucidate the influence of flow rate on the oil recovery during dynamic imbibition.The pores of the cores used were divided into micropores(0.01-1.00 μm in diameter),mesopores(1.00-30.00 μm in diameter),and macropores(30.00-400.00 μm in diameter) by matching the T_(2)spectrum and the mercury intrusion data.The volume proportion of micropores was 52.0%,and that of macropores was 19.0%.The total oil recovery of the core was found to reach 29.8% at the optimal flow rate of 0.1 mL/min.At the optimal flow rate,the oil recovery of micropores reached 50.4%,followed by that of macropores(28.6%),and that of mesopores was the lowest(15.8%).The oil expulsion efficiency,the capillary number,and the contribution to total oil recovery of micropores significantly increased with the decrease in flow rate,while those of macropores decreased.This was caused by the synergy of capillary force and displacement pressure.During dynamic imbibition at a low flow rate,the oil in micropores was effectively expelled driven by capillary force,and the effect of displacement pressure was weak,leading to large amounts of remaining oil trapped in macropores.On the contrary,when the flow rate was too high,large amounts of remaining oil would be trapped in micropores.Only at a moderate flow rate did the capillary force and displacement pressure both have significant effects on oil expulsion,and the oil in different sized pores was effectively expelled,thus generating a relatively high total oil recovery.展开更多
The oil-water imbibition equation in the nano-scale pores considering the dynamic contact angle effect, nanoconfinement effect, inertia effect, and inlet end effect was established, and the relation between the fricti...The oil-water imbibition equation in the nano-scale pores considering the dynamic contact angle effect, nanoconfinement effect, inertia effect, and inlet end effect was established, and the relation between the friction coefficient of solid-oil-water three-phase contact line and the fluid viscosity in the interface zone was derived. In combination with the capillary bundle model and the lognormal distribution theory, the imbibition model of tight core was obtained and key parameters affecting imbibition dynamics were analyzed. The study shows that in the process of nanopore imbibition, the dynamic contact angle effect has the most significant impact on the imbibition, followed by nanoconfinement effect(multilayer sticking effect and slippage effect), and the inertia effect and inlet end effect have the least impact;in the initial stage of imbibition, the effect of inertial force decreases, and the effect of contact line friction increases, so the dynamic contact angle gradually increases from the initial equilibrium contact angle to the maximum and then remains basically stable;in the later stage of imbibition,the effect of contact line friction decreases, and the contact angle gradually decreases from the maximum dynamic contact angle and approaches the initial equilibrium contact angle;as the pore radius decreases, the dynamic contact angle effect increases in the initial stage of imbibition and decreases in the later stage of imbibition;as the oil-water interfacial tension increases, the imbibition power increases, and the dynamic contact angle effect increases;there is a critical value for the influence of interfacial tension on the imbibition dynamics. In improving oil recovery by imbibition in tight oil reservoir, interfacial tension too low cannot achieve good imbibition effect, and the best interfacial tension needs to be obtained through optimization.展开更多
A physical simulation method with a combination of dynamic displacement and imbibition was established by integrating nuclear magnetic resonance(NMR)and CT scanning.The microscopic production mechanism of tight/shale ...A physical simulation method with a combination of dynamic displacement and imbibition was established by integrating nuclear magnetic resonance(NMR)and CT scanning.The microscopic production mechanism of tight/shale oil in pore throat by dynamic imbibition and the influencing factors on the development effect of dynamic imbibition were analyzed.The dynamic seepage process of fracking-soaking-backflow-production integration was simulated,which reveals the dynamic production characteristics at different development stages and their contribution to enhancing oil recovery(EOR).The seepage of tight/shale reservoirs can be divided into three stages:strong displacement and weak imbibition as oil produced rapidly by displacement from macropores and fractures,weak displacement and strong imbibition as oil produced slowly by reverse imbibition from small pores,and weak displacement and weak imbibition at dynamic equilibrium.The greater displacement pressure results in the higher displacement recovery and the lower imbibition recovery.However,if the displacement pressure is too high,the injected water is easy to break through the front and reduce the recovery degree.The higher the permeability,the greater the imbibition and displacement recovery,the shorter the time of imbibition balance,and the higher the final recovery.The fractures can effectively increase the imbibition contact area between matrix and water,reduce the oil-water seepage resistance,promote the oil-water displacement between matrix and fracture,and improve the oil displacement rate and recovery of the matrix.The soaking after fracturing is beneficial to the imbibition replacement and energy storage of the fluid;also,the effective use of the carrying of the backflow fluid and the displacement in the mining stage is the key to enhancing oil recovery.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.52104061)the National Key Research and Development Project(Grant No.2019YFA0708700)+2 种基金the project funded by the China Postdoctoral Science Foundation(Grant No.2020M682264)the Shandong Provincial Natural Science Foundation(Grant No.ZR2021QE075)the Fundamental Research Funds for the Central Universities(Grant No.20CX06090A)
文摘Dynamic imbibition,which is significantly affected by flow rate,plays an important role in the development of tight oil.This study investigated the impact of flow rate on dynamic imbibition in fractured tight sandstone cores via online nuclear magnetic resonance core-flooding experiments.The oil expulsion efficiency and capillary number of multiscale pores were quantitatively analyzed to elucidate the influence of flow rate on the oil recovery during dynamic imbibition.The pores of the cores used were divided into micropores(0.01-1.00 μm in diameter),mesopores(1.00-30.00 μm in diameter),and macropores(30.00-400.00 μm in diameter) by matching the T_(2)spectrum and the mercury intrusion data.The volume proportion of micropores was 52.0%,and that of macropores was 19.0%.The total oil recovery of the core was found to reach 29.8% at the optimal flow rate of 0.1 mL/min.At the optimal flow rate,the oil recovery of micropores reached 50.4%,followed by that of macropores(28.6%),and that of mesopores was the lowest(15.8%).The oil expulsion efficiency,the capillary number,and the contribution to total oil recovery of micropores significantly increased with the decrease in flow rate,while those of macropores decreased.This was caused by the synergy of capillary force and displacement pressure.During dynamic imbibition at a low flow rate,the oil in micropores was effectively expelled driven by capillary force,and the effect of displacement pressure was weak,leading to large amounts of remaining oil trapped in macropores.On the contrary,when the flow rate was too high,large amounts of remaining oil would be trapped in micropores.Only at a moderate flow rate did the capillary force and displacement pressure both have significant effects on oil expulsion,and the oil in different sized pores was effectively expelled,thus generating a relatively high total oil recovery.
基金Supported by National Natural Science Foundation of China (NO. 52174041)Beijing Natural Science Foundation (NO. 2184120)Science Foundation of China University of Petroleum,Beijing (No. 2462018YJRC033)。
文摘The oil-water imbibition equation in the nano-scale pores considering the dynamic contact angle effect, nanoconfinement effect, inertia effect, and inlet end effect was established, and the relation between the friction coefficient of solid-oil-water three-phase contact line and the fluid viscosity in the interface zone was derived. In combination with the capillary bundle model and the lognormal distribution theory, the imbibition model of tight core was obtained and key parameters affecting imbibition dynamics were analyzed. The study shows that in the process of nanopore imbibition, the dynamic contact angle effect has the most significant impact on the imbibition, followed by nanoconfinement effect(multilayer sticking effect and slippage effect), and the inertia effect and inlet end effect have the least impact;in the initial stage of imbibition, the effect of inertial force decreases, and the effect of contact line friction increases, so the dynamic contact angle gradually increases from the initial equilibrium contact angle to the maximum and then remains basically stable;in the later stage of imbibition,the effect of contact line friction decreases, and the contact angle gradually decreases from the maximum dynamic contact angle and approaches the initial equilibrium contact angle;as the pore radius decreases, the dynamic contact angle effect increases in the initial stage of imbibition and decreases in the later stage of imbibition;as the oil-water interfacial tension increases, the imbibition power increases, and the dynamic contact angle effect increases;there is a critical value for the influence of interfacial tension on the imbibition dynamics. In improving oil recovery by imbibition in tight oil reservoir, interfacial tension too low cannot achieve good imbibition effect, and the best interfacial tension needs to be obtained through optimization.
基金Supported by the PetroChina Science and Technology Major Project(2021-117)PetroChina CCUS Major Science and Technology Project(2021ZZ01-03)。
文摘A physical simulation method with a combination of dynamic displacement and imbibition was established by integrating nuclear magnetic resonance(NMR)and CT scanning.The microscopic production mechanism of tight/shale oil in pore throat by dynamic imbibition and the influencing factors on the development effect of dynamic imbibition were analyzed.The dynamic seepage process of fracking-soaking-backflow-production integration was simulated,which reveals the dynamic production characteristics at different development stages and their contribution to enhancing oil recovery(EOR).The seepage of tight/shale reservoirs can be divided into three stages:strong displacement and weak imbibition as oil produced rapidly by displacement from macropores and fractures,weak displacement and strong imbibition as oil produced slowly by reverse imbibition from small pores,and weak displacement and weak imbibition at dynamic equilibrium.The greater displacement pressure results in the higher displacement recovery and the lower imbibition recovery.However,if the displacement pressure is too high,the injected water is easy to break through the front and reduce the recovery degree.The higher the permeability,the greater the imbibition and displacement recovery,the shorter the time of imbibition balance,and the higher the final recovery.The fractures can effectively increase the imbibition contact area between matrix and water,reduce the oil-water seepage resistance,promote the oil-water displacement between matrix and fracture,and improve the oil displacement rate and recovery of the matrix.The soaking after fracturing is beneficial to the imbibition replacement and energy storage of the fluid;also,the effective use of the carrying of the backflow fluid and the displacement in the mining stage is the key to enhancing oil recovery.
