基于OVT域偏移数据的云质岩储层预测技术及应用--以玛湖凹陷乌夏地区风三段为例

Dolomitic reservoir prediction technology based on OVT domain migration data and its application:A case study of Feng 3 member in Wuxia area,Mahu Sag

由于乌夏地区二叠系风城组风三段湖相云质岩“甜点”储层单层厚度小、横向变化快、与围岩的波阻抗差异较小等特点,使用常规三维资料预测“甜点”分布难度大。对高产井的云质岩“甜点”储层油气富集主控藏因素分析认为,“甜点”发育区主要受控于储层厚度大、脆性(裂缝)发育区及高压区的叠合部位。以油气主控因素为切入点,采用在地质目标驱动下基于炮检距-方位角叠加模板的道集动态分析与叠加的方法,形成不同方位角的叠前偏移地震数据用于预测云质岩储层厚度;基于弹性参数交会分析模板,利用杨氏模量(E)与泊松比(σ)的比值增大来预测斜坡区云质岩储层脆性发育区;从波动方程、胡克定律和弹性参数的定义出发推导出有效应力与纵、横波速度之间的关系,研发出了一种新的弹性参数杨氏模量(E)和体积模量(K)加权法,用于预测异常压力区,从而提高了“甜点”储层在平面上的预测精度。利用此项研究成果,部署钻探了3口探井均在风三段获得高产油流,预测石油地质储量亿吨级,并指出下一步斜坡区的勘探方向为FC1井西南方向云质岩“甜点”储层发育区。

The lacustrine dolomitic reservoir“sweet spots”of Feng 3 member of Permian Fengcheng Formation in Wuxia area have the characteristics of single thin layer,rapid lateral change and small impedance differences from surrounding rocks,so it is difficult to predict the“sweet spots”reservoir by using conventional 3D seismic data.Based on the analysis of main controlling factors of oil enrichment in the dolomitic reservoir“sweet spots”in high yield wells,it is found that the“sweet spots”are mostly in places where the reservoirs have large thickness,high brittleness(fractures)and high pressure.Based on the main controlling factors of oil accumulation,trace gather dynamic analysis and stacking method based on offset-azimuth stacking template under geologic target was worked out to get prestack seismic data of different azimuths to predict the thickness of dolomitic reservoir.On the basis of elastic parameter cross-plot analysis template,Young’s modulus(E)and Poisson’s ratio(σ)were used to predict the brittle part of dolomitic reservoir in the slope area.Based on wave equation,Hooke’s law and elastic parameter,the relationships of effective stress with P-wave and S-wave velocity were derived,and a for‐mation pressure prediction method combining Young’s modulus(E)and volume modulus(K)was developed to predict the area with abnormal pressure to enhance the prediction accuracy of“sweet spots”.After the application of this result,three wells have obtained high yield oil flows in Feng 3 member,and hundred million tons geologic oil reserves are evaluated.