地质统计反演在东濮凹陷白庙气田沙三段储层预测中的应用

Application of geostatistical inversion in reservoir prediction in the third member of Shahejie Formation,Baimiao Gas-field,Dongpu Depression

本文基于约束稀疏脉冲波阻抗反演进行地质统计反演,把标准化后的自然电位曲线作为输入参数,把稀疏脉冲反演得到的波阻抗数据体作为相关控制函数。首先,统计随机变量的直方图分布和变差函数,确定随机变量在不同方向上的变程;然后在每一地震道上,将随机提取的反射系数与求取的地震子波进行褶积,生成合成地震道,将合成地震道与原始地震道进行匹配,计算反演的剩余值,直到匹配程度满足精度要求为止;最后,选择合成地震记录最好的节点值作为反演结果,对下一个随机选取的节点进行反演,直到完成各个随机实现的全部反演,再对相关性大于90%的各个实现进行求均方根运算,并将获得的均方根数据体作为最终的反演结果。文中以白庙气田三维地震工区沙三段水下扇体为研究对象,在分析储层岩性、电性、物理特征的基础上,选取地震空变子波,建立低频模型,通过合理选取反演参数λ,把标准化后的自然电位曲线作为输入参数,利用约束稀疏脉冲反演和地质统计反演技术,得到的反演结果与实钻资料吻合率达到81.3%,取得了较好的效果。

In this paper based on constrained sparse spike inversion the geostatistical inversion was conducted with the normalized natural potential curve as input and the impedance data volume obtained from constrained sparse spike inversion as correlation control function.At first calculating random variable’s histogram distribution and variogram,determining random variable’s range in different directions,then in each seismic trace by convoluting extracted reflection coefficient with estimated seismic wavelet to obtain synthetic seismogram,by matching the synthetic seismogram with original seismic trace to calculate residual value for the inversion until matching degree meeting the accuracy requirement,at last by choosing the best node value for the synthetic seismogram as inversion result to conduct inversion for the next randomly selected node until finishing the whole inversion,after that conducting root mean square calculation for each realization whose correlativity is larger than 90% until completing whole inversion of the random process.In this paper the submarine fan in the third member of Shahejie Formation,Baimiao Gas-field was taken as study object,based on the analysis for reservoir’s lithology,electrical properties and physical characteristic,the seismic spatial-variable wavelet was chosen and the low frequency model was built up,by selecting reasonable inversion parameterλand taking normalized natural potential curve as input,the inversion was conducted by using constrained sparse spike inversion and geostatistical inversion,the matching rate between inversion result and the drilling result reaches 81.3%,therefore excellent application result was achieved in the paper.