TTI 型页岩气储层脆性指数和裂缝参数分级反演方法  

Hierarchical inversion of brittleness indicator and fracture parameters for shale gas reservoirs with tilted transverse isotropy

作　　者：谭媛媛 张广智[1,2,3] 马正乾 郝洪鉴 韩钊 TAN Yuanyuan;ZHANG Guangzhi;MA Zhengqian;HAO Hongjian;HAN Zhao(National Key Laboratory of Deep Oil and Gas,China University of Petroleum(East China),Qingdao 266580,China;School of Geosciences,China University of Petroleum(East China),Qingdao 266580,China;CNPC Key Lab of Geophysical Exploration,Beijing 102249,China;Northwest Oilfield Branch of China Petroleum and Chemical Corporation,Urumqi 830011,China)

机构地区：[1]深层油气全国重点实验室(中国石油大学(华东)),山东青岛266580 [2]中国石油大学(华东)地球科学与技术学院,山东青岛266580 [3]CNPC物探重点实验室,北京102249 [4]中国石油化工股份有限公司西北油田分公司,新疆乌鲁木齐830011

出　　处：《石油物探》2025年第2期340-352,共13页Geophysical Prospecting For Petroleum

基　　金：国家自然科学基金项目(42074136,U23B6010);中国石油天然气股份有限公司项目“复杂气藏岩石物理机理及模型构建研究”(2022A-080)共同资助

摘　　要：含倾斜裂缝的地层在地下广泛分布,可等效为倾斜横向各向同性(TTI)介质。TTI型富有机质页岩气储层即使具有较高的脆性程度,但其杨氏模量可能依旧较低,从而降低了杨氏模量作为储层脆性指数的适用性。为此,将杨氏模量与拉梅第一常数的组合作为脆性指数,推导了由脆性指数、裂缝密度和倾角直接表达的TTI介质线性化纵波反射系数方程及其傅里叶级数形式,有效分离了裂缝信息和背景基质信息。然后,在贝叶斯反演框架下,结合离散傅里叶级数,提出了一种直接预测TTI型富有机质页岩气储层脆性特征和裂缝参数的分级地震反演方法,该方法分别利用地震数据的二阶分量和零阶分量直接预测裂缝参数和脆性指数,以解决裂缝参数和脆性指数对地震数据贡献度不同而导致的裂缝参数预测稳定性差的问题,同时避免了裂缝方位估计误差对裂缝密度和裂缝倾角预测精度的影响。模型测试和实际应用结果表明,该方法估计的裂缝参数和脆性指数合理地圈定了优质脆性储层,提高了裂缝参数的预测稳定性。Subsurface formations with aligned dipping fractures can be equivalent to the media with tilted transverse isotropy(TTI).For TTI-type organic-rich shale gas reservoirs,the Young's modulus is not a sensitive brittleness indicator as a low value may emerge at a high degree of brittleness.Therefore,a hierarchical seismic inversion method is proposed to directly predict the brittleness and fracture parameters of TTI-type organic-rich shale gas reservoirs.We derive a linearized P-wave reflection coefficient equation for TTI media in terms of a new brittleness indicator formulated as the function of the Young's modulus and Laméconstant(λ),fracture density and fracture dip.The reflection coefficient equation is rewritten in the form of the Fourier series to separate fracture information from background matrix information. Based on the Bayesian framework, the hierarchical inversion method is established to predict brittleness indicator and fracture parameters. The process is composed of three steps. Firstly,we utilize the discrete Fourier series to decouple the isotropic (zero-order) and anisotropic (second-order) components of azimuthal seismic data. Secondly,we invert fracture density and fracture dip from the second-order component of azimuthal data. Thirdly,the brittleness indicator can be estimated using the zero-order component. The model test and practical application indicate the robustness of the method and credible prediction of high-quality brittle reservoirs.

关 键 词：脆性指数 裂缝密度和倾角 TTI介质 纵波反射系数 傅里叶级数 

分 类 号：P631[天文地球—地质矿产勘探]