基于残余岩溶指数的表生岩溶储层综合评价及有利区带预测——以南堡凹陷下古生界碳酸盐岩潜山为例

Comprehensive evaluation of supergene karst reservoir based on residual karst index and prediction of favorable zone:A case study on carbonate buried hill of the lower Paleozoic in Nanpu sag

南堡凹陷碳酸盐岩潜山顶面以下100 m范围内为表生岩溶储层发育区,钻井已证实其具有巨大的勘探潜力。综合利用地震、岩心、薄片、扫描电镜、测井、录井及试油等资料,首次引入残余岩溶指数作为评价研究区表生岩溶储层储集空间有效性的定量参数,结合成岩作用类型及程度、储集空间类型、物性特征和孔隙结构类型多项参数,更加全面、客观地将南堡凹陷下古生界碳酸盐岩潜山表生岩溶储层分为Ⅰ,Ⅱ和Ⅲ类,并对其进行综合评价。选取与残余岩溶指数相关性好,但彼此地震属性之间相关性差的平均波峰振幅、平均瞬时频率和振幅扭曲度3种地震属性,利用模糊C均值聚类法将残余岩溶指数平面成图,并与验证井的实际数据进行对比,发现其准确率大于70%。最终实现对南堡凹陷下古生界碳酸盐岩潜山表生岩溶储层有利区带预测,为下一步勘探部署指明方向。

The supergene karst reservoir,regarded as the research target by drilling,develops 100 m thick below the top of the carbonate buried hill in Nanpu sag. The residual karst index is firstly introduced as a quantitative parameters for evaluating the effectiveness of supergene karst reservoir space in the study area,taking advantage of seismic data,core,thin sections,electron microscope(SEM),well logging,mud logging and oil test data and combining with diagenesis types and degree,classification of reservoir space,physical characteristics and pore structure types. As a result,the supergene karst reservoirs of carbonate buried hill in Nanpu sag are divided into 3 types of I,II and III and evaluated comprehensively. Average amplitude,average instantaneous frequency and amplitude distorted degree,which are better correlated to residual karst index and independent to each other,are selected to be clustered and then mapped. At last,the supergene karst index contour map is drawn and then is verified with the actual drilling data. It is found that the accuracy rate is more than 70%.Finally,the favorable zone prediction of the carbonate supergene karst reservoir in Nanpu buried hill is realized,which indicates the direction for the next exploration and deployment.