基于HTI介质地震曲率属性的地应力估算方法及其在威远地区的应用

Using 3D seismic data to estimate stress based on seismic curvature attribute of HTI medium:application to the Weiyuan,southern Sichuan Basin,China

在非常规油气藏的开发和勘探阶段,为了形成有利于油气集聚和运移的裂缝,需要对储层进行水力压裂,而地应力是进行水力压裂的重要参数.目前,传统的三维地质力学建模方法是估算地应力的有效手段,其主要通过井间插值得到三维地应力结果.但是,在井稀疏的区域会产生较大误差.考虑到三维地震数据具有空间连续性的特点.本文提出了一种融入地震曲率属性的HTI介质组合弹簧模型,该模型突破了传统地质力学中水平构造应变为常数的假设.首先,通过叠前AVO反演和PNN神经网络预测得到杨氏模量和泊松比这两个力学参数;其次,对地震方位波阻抗进行椭圆拟合预测裂缝密度.之后,基于薄板理论,引入三维地震曲率属性来表征水平构造应变的影响.最后,利用融入地震曲率属性的HTI介质组合弹簧模型估算三维地应力场.将该方法应用于川南威远工区,结果表明,本文提出的新方法与传统地质力学的结果吻合较好,能够获得更高精度、更高分辨率的真三维地应力场,且能较好的反映出构造细节.验证了该方法的可行性和准确性.

During the development and exploration stage of unconventional oil and gas reservoirs,the reservoirs need to be hydraulically fractured to form fractures for gas and oil accumulation and migration.In-situ stress is an important parameter for hydraulic fracturing.At present,the traditional three-dimensional(3D)is an effective method to estimate the in-situ stress,which mainly obtains the 3D in-situ stress results through interpolation between wells.However,it can give misleading results in new fields with sparse well control.Taking advantage of the spatial coverage of 3D seismic data,we propose a curvature attribute integrated HTI(Horizontal Transverse Isotropic)MEM(Mechanical Earth Model).The method introduces curvature attributes to characterize 3D tectonic strain and overcomes the assumption that the traditional MEM tectonic strain is constant.Firstly,two important mechanical elastic parameters(Young's modulus and Poisson's ratio)are obtained through pre-stack seismic AVO(Amplitude Vary with Offset)inversion and PNN(Probabilistic Neural Networks)prediction.Secondly,an elliptical fitting is used to predict fracture density based on seismic azimuthal impedance.Thirdly,we introduce the curvature attribute based on the plate theory to characterize the geological structure influence.Finally,we use the curvature attribute integrated HTI MEM to estimate the 3D in-situ stress.Through the practical application of Weiyuan work area in southern Sichuan Basin,China.The results demonstrate that the proposed approach aligns well with traditional method,It can obtain the true 3D stress field with higher precision and resolution.Furthermore,the HTI MEM results highlight the fracture developed zones and reflect more details of the geological structure,indicating that the new method has good feasibility and accuracy.