基于贝叶斯反演的HTI介质地应力预测方法的研究和应用

Research and application of in-situ stress prediction method for HTI medium based on Bayesian inversion

地应力作为指导储层水力压裂的关键参数,影响着储层裂缝的大小、方向以及形态.对储层进行水力压裂有利于油气的储藏和运移,对于提高油气产能具有重要意义.本文提出基于贝叶斯反演的HTI介质地应力预测方法.首先,考虑致密砂岩储层中存在的大量垂直裂缝,将其等效为HTI介质,以HTI介质各向异性理论和贝叶斯反演理论为基础,通过叠前方位地震数据获得地下介质的弹性参数和各向异性参数.其次,根据HTI介质主应力计算方程,利用反演得到的弹性参数和各向异性参数实现地应力预测.最后,根据储层水平应力差异比(DHSR,Differential Horizontal Stress Ratio)分布指示储层中易于压裂改造、且油气资源丰富的区域.模型数据测试验证了该反演算法具有可行性和一定的抗噪性,实际资料的应用结果表明,基于叠前方位地震数据反演得到的DHSR能够有效指示致密砂岩储层中易于压裂成网的区域,对致密砂岩油气藏开采效率的突破具有重要意义.

The prediction of in-situ stress is a critical parameter for guiding reservoir hydraulic fracturing,which influences the size,orientation,and morphology of reservoir fractures.Hydraulic fracturing of reservoirs is beneficial for the storage and transportation of oil and gas,and is of great significance for increasing oil and gas production.This paper proposes a method for predicting in-situ stress in HTI media based on Bayesian inversion.Firstly,considering the abundant vertical fractures in tight sandstone reservoirs,these are equivalent to HTI media.Based on the theory of HTI media anisotropy and Bayesian inversion,elastic parameters and anisotropy parameters of the underground media are obtained through pre-stack seismic data.Subsequently,the prediction of in-situ stress is achieved by utilizing the inverted elastic parameters and anisotropic parameters based on the principal stress calculation equation for HTI media.Finally,the Differential Horizontal Stress Ratio(DHSR)distribution is used to indicate areas in the reservoir that are easily amenable to fracturing and rich in oil and gas resources.Model data testing verifies the feasibility and noise resistance of the inversion algorithm,and application results from actual data demonstrate that the DHSR obtained from pre-stack seismic data inversion can effectively indicate areas in tight sandstone reservoirs that are easily fracturable,holding important implications for breakthroughs in the efficiency of tight sandstone oil and gas reservoir exploitation.