储层弹性与物性参数地震叠前同步反演的确定性优化方法  

Prestack seismic joint inversion of reservoir elastic and petrophysical parameters using deterministic optimization method

作　　者：李志勇[1] 钱峰[1] 胡光岷[1] 贺振华[2] 

机构地区：[1]电子科技大学通信与信息工程学院,成都611731 [2]成都理工大学油气藏地质与开发工程国家重点实验室,成都610059

出　　处：《地球物理学报》2015年第5期1706-1716,共11页Chinese Journal of Geophysics

基　　金：国家自然科学基金青年基金项目(41104067);国家自然科学基金项目(40839905)资助

摘　　要：储层弹性与物性参数可直接应用于储层岩性预测和流体识别,是储层综合评价和油气藏精细描述的基本要素之一.现有的储层弹性与物性参数地震同步反演方法大都基于Gassmann方程,使用地震叠前数据,通过随机优化方法反演储层弹性与物性参数;或基于Wyllie方程,使用地震叠后数据,通过确定性优化方法反演储层弹性与物性参数.本文提出一种基于Gassmann方程、通过确定性优化方法开展储层弹性和物性参数地震叠前反演的方法,该方法利用Gassmann方程建立储层物性参数与叠前地震观测数据之间的联系,在贝叶斯反演框架下以储层弹性与物性参数的联合后验概率为目标函数,通过将目标函数的梯度用泰勒公式展开得到储层弹性与物性参数联合的方程组,其中储层弹性参数对物性参数的梯度用差分形式表示,最后通过共轭梯度算法迭代求解得到储层弹性与物性参数的最优解.理论试算与实际资料反演结果证明了方法的可行性.Elastic and petrophysical parameters of reservoir can be directly applied to lithology prediction and fluid identification,they are the basic elements in both comprehensive evaluation and fine characterization of hydrocarbon reservoir.Existing seismic joint inversion methods for estimating elastic and petrophysical parameters of reservoir are mainly based on either Gassmann equation,with which these parameters are inversed from prestack seismic data by stochastic optimization methods;or Wyllie equation,with which these parameters are inverted from poststack seismic data by deterministic optimization methods.The purpose of this work is todevelop a strategy for estimating elastic and petrophysical parameters of reservoir based on Gassmann equation with deterministic seismic prestack inversion.We use Gassmann equation to build up the relationship between prestack seismic data and petrophysical parameters.We treat the joint posterior probability of elastic and petrophysical parameters as the objective function under the Bayesian architecture,by expanding the the objective function with Taylor formula,the joint equations composed of physical and petrophysical parameters can thus be obtained,and the derivatives of the elastic parameters with respect to petrophysical parameters are obtained by differentiating.The conjugate gradient method is then used to find the optimal solutions of P-wave velocity,shear velocity,density,porosity,water saturation and clay content.We apply this inversion method to prestack seismic data set in Sulige gas field,which is one of the largest gas fields in central Ordos Basin in China.The main gas-producing interval is the H8 sandstone reservoir at the bottom of Lower Shihezi Formation,Lower Permian,Upper Paleozoic.Drilling results indicate that this region is a composite sandstone gas reservoir and its heterogeneous reservoirs are characterized by low permeability,low pressure and low abundance,which bring great challenge to the exploitation of this field.From the comparison of the inversion

关 键 词：储层弹性参数 储层物性参数 岩石物理方程 确定性反演 

分 类 号：P631[天文地球—地质矿产勘探]