碳酸盐岩孔隙度预测新方法在珠江口盆地的应用

APPLICATION OF NEW METHOD TO PREDICTING CARBONATE POROSITY IN THE ZHUJIANGKOU BASIN

孔隙度是油气勘探中储层预测、储层描述、储量估算和油气藏综合研究的一个重要评价参数,它的准确求取是一项非常重要的关键性技术。碳酸盐岩非均质性强,横向变化大,其孔隙度预测一直是个难题。常规方法对孔隙度进行计算存在精度不高、物理意义不明确等问题,常常不能满足油气勘探开发需求。因此,通过对Gassmann方程合理简化并引入Eshelby—Walsh干燥岩石椭球包体近似公式,推导出包含岩石孔隙结构参数、饱和岩石压缩系数与岩石基质压缩系数3个参数的计算孔隙度新公式,然后通过测井交汇图技术和叠前弹性参数反演技术,将其转化为与碳酸盐岩孔隙结构和纵横波速度、密度有关的具体计算公式。同时考虑到不同相带对碳酸盐岩储层孔隙结构的影响,故分相带对新方法进行了应用。结果表明,基于碳酸盐岩孔隙结构的孔隙度预测方法的精度高于常规方法。

Porosity is critical to reservoir prediction,reservoir description,reservoir estimation and comprehensive reservoir study.It's also a critical technology to accurate estimation of oil reserve.Because of the strong heterogeneity of carbonate rock and strong lateral variation,the porosity prediction has remained a difficult problem for carbonate reservoir.Moreover,the accuracy of conventional method to calculate the porosity is not high enough and the physical meaning is always not so clear,it is hard to meet the needs of exploration and development.Therefore,through the reasonable simplification of the Gassmann equation and the introduction of Eshelby-Walsh dry rock ellipsoidal inclusions approximate formula,we derived a new formula to calculate the porosity.Three parameters,i.e.the pore structure parameters,saturated rock compressibility and rock matrix compressibility are included.Then through the intersection of logging technique charts and the inversion of pre-stack elastic parameters into the pore structure of carbonate and P-wave and S-wave velocity and density in the specific formula,considering the influence of carbonate rock pore structure with different phase,and the new method was applied.The results show that the porosity prediction method of carbonate rock pore structure has higher accuracy than the conventional method based on.