基于力学时变性的页岩油藏四维地应力演化规律研究  

Four-dimensional in-situ stress evolution law of shale reservoirs based on mechanical time-varying characteristics

作　　者：吕琦 吕晶 程紫燕 宋阳 侯健[2] LÜQi;LÜJing;CHENG Ziyan;SONG Yang;HOU Jian(Exploration and Development Research Institute,Shengli Oilfield Company,SINOPEC,Dongying City,Shandong Province,257015,China;School of Petroleum Engineering,China University of Petroleum(East China),Qingdao City,Shandong Province,266580,China)

机构地区：[1]中国石化胜利油田分公司勘探开发研究院,山东东营257015 [2]中国石油大学(华东)石油工程学院,山东青岛266580

出　　处：《油气地质与采收率》2024年第5期56-65,共10页Petroleum Geology and Recovery Efficiency

基　　金：中国石化股份公司课题“东营凹陷页岩油立体开发优化设计关键技术”(P23026)。

摘　　要：裂缝对页岩岩石力学性质影响突出,准确表征含裂缝页岩的岩石力学性质变化是实现页岩油藏压裂-投产过程中四维地应力场精准刻画的重要基础。已有四维地应力研究通常认为应力变化主要源于孔隙压力改变,未考虑岩石力学性质变化对四维地应力的影响。利用在线CT实验,明晰了孔隙压力与页岩孔缝体积的关系,依据应变能理论,推导了裂缝体积与页岩泊松比、弹性模量的理论关系,建立了孔隙压力与泊松比、弹性模量的时变理论模型。结果表明,层理缝开启是页岩岩石力学参数具有时变性的主要原因,孔隙压力越大,裂缝开启条数越多,裂缝空间呈指数型增长。随裂缝体积增加,页岩泊松比快速增加、杨氏模量快速减小,页岩强度大幅降低。以济阳坳陷页岩为例开展分析,裂缝体积占比提高至1%时,杨氏模量由37.5GPa下降至15.06GPa,泊松比由0.22上升至0.35。依托数值模拟方法对比分析岩石力学参数时变性对四维地应力演化的影响,考虑岩石力学时变性特征的四维地应力模拟能够更好地表征页岩压裂-投产过程中的应力大小演化与方向偏转的规律,与实际油藏压裂-投产过程中的四维地应力演化规律更加吻合,模拟结果更加可靠。研究成果能够为页岩油立体井组合理部署、优化设计、风险预警等提供理论支撑。The influence of fractures on the mechanical properties of shale rocks is prominent.Accurately characterizing the changes in the mechanical properties of fractured shale is an essential basis for precisely depicting the four-dimensional in-situ stress field during the fracturing and production process of shale reservoirs.Existing studies on four-dimensional in-situ stress often attri-bute stress changes primarily to alterations in pore pressures,neglecting the impact of changes in the mechanical properties of rocks on four-dimensional in-situ stress.The relationship between the pore pressure and the volume of shale pores and fractures was clari-fied by utilizing online CT experiments.Theoretical relationships among fracture volume,Poisson’s ratio,and elastic modulus of shale rocks were derived based on strain energy theory.Furthermore,a time-varying theoretical model was established with pore pressure,Poisson’s ratio,and elastic modulus as variables.The results indicate that the opening of bedding fractures is the primary cause of the time-varying nature of the mechanical parameters of shale rocks.The number of fractures opening increases,and the fracture space exhibits exponential growth as pore pressure increases.With the increase in fracture volume,the Poisson’s ratio of shale rocks rapidly increases,while the Young’s modulus rapidly decreases,leading to a significant reduction in shale strength.An analysis of the shale in Jiyang Depression reveals that Young’s modulus decreases from 37.5 GPa to 15.06 GPa,and the Poisson’s ratio increases from 0.22 to 0.35 when the proportion of fracture volume increases to 1%.The influence of the time-varying nature of mechanical parameters of rocks on the evolution of four-dimensional in-situ stress is comparatively analyzed through numerical simulation methods.The four-dimensional in-situ stress simulation,considering the time-varying characteristics of rock mechanics,can better characterize the law of stress evolution and direction deflection during shale fract

关 键 词：页岩油 四维地应力 岩石力学性质 时变性特征 四维地应力模拟 

分 类 号：TE321[石油与天然气工程—油气田开发工程]