摘要
致密油储层体积压裂后储渗空间复杂,微纳米孔隙与多尺度裂缝并存,压裂-焖井-返排一体化开发微观渗流规律认识不清。为此,采用微焦点CT扫描和数字图像处理技术,构建致密油藏数字岩心模型,提出压裂-焖井-返排一体化开发微观渗流格子Boltzmann模拟方法,研究压裂驱动、焖井渗吸、返排开发3个阶段的油水渗流规律,阐明油水黏度比、岩石润湿性及毛细管数的影响。结果表明:压裂驱动阶段,压裂液优先沿裂缝运移,少量压裂液进入裂缝-孔隙接触区;焖井渗吸阶段,压裂液优先渗入小孔喉,置换采出的油滴通过大孔喉流入裂缝;返排开发阶段,裂缝-基质接触区的油滴优先被剥离,大量油滴难以被波及;毛细管数越大,油水黏度比越小,压裂增能效果越好,越利于动用基质原油,渗吸采收率越高;水湿程度越高,油滴拓扑连通性越强,越利于发生渗吸,压裂液返排难度越大。
The storage space of tight formation after volumetric fracturing is complex,characterized by the coexistence of micro-nano pores and multi-scale fractures,which hinders a clear understanding of pore-scale flow in the fracturing-shut in-flowback process of tight oil reservoirs.In this study,micro-focus CT imaging and digital image processing methods were used to build digital rock core models retrieved from raw CT images.Subsequently,a pore-scale modeling workflow was proposed based on a pseudo-potential lattice Boltzmann model to reveal the underlying mechanisms of fluid exchange during the integrated fracturing-shut in-flowback process,which can be used to investigate the oil-water exchange behaviors during the three stages of fracturing-driven,shut-in imbibition and flowback production.A systematic analysis of the influence of oil-water viscosity ratio,rock wetting angle and capillary number on the pore-scale oil-water exchange was conducted.The results show that,during the fracturing-driven stage,fracturing fluid primarily migrates along the fractures,with only a small amount entering the pore space nearby the fractures.In the shut-in imbibition stage,the fracturing fluid preferentially flows into small pore throats,displacing the recovered oil droplets through the large pore throats.In the flowback production stage,oil droplets occupied in the fracture-matrix contact areas can be preferentially stripped off,but there still exists a large amount of oil droplets that are difficult to be swept.Higher capillary number and lower oil-water viscosity ratio are beneficial for hydraulic fracturing in tight oil reservoirs,activating the mobilization of crude oil droplets trapped in the stimulated reservoir volume region and improving imbibition recovery.The higher the degree of water wetting,the smaller the Euler coefficient,and the better the connectivity of remaining oil,which is more conducive to spontaneous imbibition and difficult for fracturing fluid to flow back.
作者
王代刚
刘芳洲
贾宁洪
李国永
宋考平
胡哲
石宇哲
WANG Daigang;LIU Fangzhou;JIA Ninghong;LI Guoyong;SONG Kaoping;HU Zhe;SHI Yuzhe(State Key Laboratory of Petroleum Resources and Engineering,China University of Petroleum(Beijing),Beijing 102249,China;Research Institute of Petroleum Exploration and Development,PetroChina,Beijing 100083,China;Jidong Oilfield Company,PetroChina,Tangshan 063000,China)
出处
《中国石油大学学报(自然科学版)》
北大核心
2025年第1期101-111,共11页
Journal of China University of Petroleum(Edition of Natural Science)
基金
国家自然科学基金面上项目(52174043)
中国石油科技创新基金项目(2022DQ02-0208)
国家自然科学基金企业联合基金项目(U22B6005)。
