纵波方位各向异性正演模拟及叠前裂缝检测应用研究——以鄂尔多斯盆地致密砂岩气区块为例

Research application of the P-wave anisotropy forward modeling and pre-stack fracture detection:take the tight sandstone gas block in Ordos basin as an example

裂缝作为油气的重要运移通道,同时可以显著改善致密储层的孔渗特性,因此预测裂缝的发育对于寻找天然气聚集的地质甜点及致密储层压裂施工改造的工程甜点具有非常关键的指导作用.基于叠前纵波地震资料的方位各向异性特性进行裂缝预测技术,由于受多种因素影响裂缝方位与纵波反射系数的关系异常复杂,因此需要通过岩石物理正演模拟实验以及成像测井资料来确定二者之间关系.在此基础上针对鄂尔多斯盆地X区块的致密砂岩储层,利用裂缝相对密度半定量化研究技术,成功预测了X区块的致密砂岩储层的裂缝发育的密度.通过电阻率成像测井、钻井岩心资料及后续压裂试采情况验证表明:高角度高导裂缝与叠前裂缝预测成果吻合度较高,预测精度能够满足勘探开发生产需求,证明该技术在X区块具有实际的应用价值.

Fracture is one important type of migration pathway for hydrocarbon, as well as a key factor which significantly improves the porosity-permeability property in tight reservoirs. Therefore the prediction of distribution of fracturing system takes a critical role in discovering geological dessert of gas accumulations and engineering dessert of fracturing in tight reservoirs. We use azimuthal anisotropy of prestack P-wave seismic data to predict the layout of fractures. Due to the complexity between azimuth of fractures and the P-wave reflection coefficient, we must determine the interactive relationship between them by petrophysical forward simulations and imaging logging data. Subsequently we apply the fracture-relative-density semi-quantitative calibration technology to the tight sandstone reservoir of X Block in Ordos basin, which, in turn, successfully aid us to predict the density of fractures in tight sandstone reservoirs. The FMI, coring data and the subsequent fracturing test results validate that the high-angle and high-conductive fractures are consistent with pre-stack prediction results whose forecasting precision meets all fundamental requirements from exploration and production of hydrocarbon. Our new technology is proved effective and it has the widespread commercial value and the prospects for development in X Block.