南黄海横波测井曲线预测在叠前反演中的应用

APPLICATION OF S-WAVE WELL LONGING PREDICTED FOR PRESTACK INVERSION IN THE SOUTH YELLOW SEA BASIN

南黄海中—古生界发育大套碳酸盐岩和碎屑岩的互层沉积。为了满足油气地质勘探的需求,地球物理储层预测技术方法需要从叠后走向叠前阻抗反演,而横波速度是储层特征评价和流体识别的重要参数,因此,对该研究区进行横波测井曲线分析值得探索。基于实测的岩石物理弹性模量,通过Biot-Gassmann方程引进固结系数,将据此计算的纵波速度与实测的纵波速度进行对比,最终以其相对误差最小时的固结系数代入Biot-Gassmann方程求得横波速度,其预测结果符合地层速度的分布规律,并为叠前储层描述提供了可靠的基础资料。通过横波预测,石炭系灰岩段的纵波速度为5 500～6 500m/s,横波速度为3 000～3 200m/s,溶孔发育的白云质灰岩段纵横波速度比变化幅度大,碎屑岩孔隙发育地层横波速度变化幅度比纵波速度大。

The Meso-Palaeozoic is a mixed clastic-carbonate sequence of epicontinental sea in the South Yellow Sea basin.In recent years,oil and gas exploration has been accelerated there,in order to meet the needs of oil and gas supply.Geophysical methods for reservoir prediction need to be improved as well from post-stack impedance inversion to pre-stack impedance inversion,as the shear wave velocity is the most important parameter for reservoir evaluation and fluid identification.Therefore,the shear wave velocity well logging is very important to the study area.Based on the measured rock physics elastic modulus,introducing in the coefficient of consolidation through the Biot-Gassmann equation,picking out the coefficient of consolidation when the relative error is minimum between calculated Pwave velocity and measured P-wave velocity,and then substituting the coefficient of consolidation into the Biot-Gassmann equation,we finally get the S-wave velocity.The prediction results of this paper fit well with the velocity distribution law in the formation,which has provided the reliable basic data for prestack reservoir description.From the S-wave prediction,the P-wave velocity of carbonate rock varies from 5 500m/s to 6 500m/s and the S-wave velocity of carbonate rock from 3 000m/s to 3 200m/s,Vp/Vs ratio is dramatic in the pore developed dolomitic limestone,and the S-wave velocity change is large than the P-wave velocity in the pore developed clastic rock.