速度-压力岩石物理模型及其在页岩孔隙压力预测中的应用  

Rock physics model for velocity–pressure relations and its application to shale pore pressure estimation

作　　者：郭静怡 李敏 庄明伟 孙跃峰 GUO Jingyi;LI Min;ZHUANG Mingwei;SUN Yuefeng(Department of Geology&Geophysics,Texas A&M University,College Station,77843,United States;Southwest Geophysical Research Institute,BGP,CNPC,Chengdu 610213,China;Institute of Electromagnetics and Acoustics,Xiamen University,Xiamen 361005,China)

机构地区：[1]德克萨斯A&M大学地质与地球物理系,大学城77843,美国 [2]中国石油集团东方地球物理勘探有限责任公司西南物探研究院,成都610213 [3]厦门大学电磁声学研究院,福建厦门361005

出　　处：《石油勘探与开发》2023年第2期360-372,共13页Petroleum Exploration and Development

基　　金：TAMU(M1803964)。

摘　　要：针对现有基于声波速度的经验公式进行地层压力预测时影响因素复杂的问题,应用弹性岩石物理模型来定量分析研究速度-压力关系的各种控制因素,提出孔构参数(γ)与压差之间的解析关系,并揭示压力对岩石体积模量和纵波速度等弹性性质的主控作用,进而准确预测孔隙压力。含气页岩中微裂缝及断裂发育时,异常高压下(高γ值)细小裂缝及扁平孔隙张开,岩石体积模量远低于其在静水压力下(低γ值)平均孔隙结构偏圆时的状态。结合岩心、测井及地震数据,利用此岩石物理压力关系刻画四川盆地丁山地区上奥陶统五峰组—下志留统龙马溪组页岩的孔隙压力三维空间分布变化,压力系数与含气量呈正相关,该预测结果与现场实测数据吻合较好。岩石物理压力关系的分析和方法的提出对非常规和常规油气田的勘探、生产和钻井安全都具有重要借鉴价值。Acoustic wave velocity has been commonly utilized to predict subsurface geopressure using empirical relations.Acoustic wave velocity is,however,affected by many factors.To estimate pore pressure accurately,we here propose to use elastic rock physics models to understand and analyze quantitatively the various contributions from these different factors affecting wave velocity.We report a closed-form relationship between the frame flexibility factor(γ)in a rock physics model and differential pressure,which presents the major control of pressure on elastic properties such as bulk modulus and compressional wave velocity.For a gas-bearing shale with abundant micro-cracks and fractures,its bulk modulus is much lower at abnormally high pore pressure(highγvalues)where thin cracks and flat pores are open than that at normal hydrostatic pressure(lowγvalues)where pores are more rounded in average.The developed relations between bulk modulus and differential pressure have been successfully applied to the Upper Ordovician Wufeng and Lower Silurian Longmaxi formations in the Dingshan area of the Sichuan Basin to map the three-dimensional spatial distribution of pore pressure in the shale,integrating core,log and seismic data.The estimated results agree well with field measurements.Pressure coefficient is positively correlated to gas content.The relations and methods reported here could be useful for hydrocarbon exploration,production,and drilling safety in both unconventional and conventional fields.

关 键 词：孔隙压力 压力系数 声波速度 体积模量 孔隙结构 页岩气 上奥陶统五峰组 下志留统龙马溪组 四川盆地 

分 类 号：TE122[石油与天然气工程—油气勘探]