鄂尔多斯盆地南部上古生界泥岩盖层封闭性能评价

Sealing capability assessment of mudstone caprock in the Upper Paleozoic,south Ordos Basin

根据钻井、测井、岩心分析、地层埋藏史、古地温等资料,研究了鄂尔多斯盆地南部上古生界泥岩的空间展布范围、成岩与封闭性演化模式及孔隙度、渗透率、突破压力分布特征。在此基础上,提出相应的评价标准和评价方法,并对其封闭性能进行综合评价。结果表明:鄂尔多斯盆地南部石千峰组泥岩Ⅰ类盖层发育,封闭性能最好,特别是在镇探1、黄深1井区,综合评价权值达到3.5;上石盒子组泥岩发育异常高压,Ⅳ类盖层分布广泛,物性封闭性能最差;下石盒子组泥岩在研究区的西部和南部为Ⅳ类盖层,北东方向发育Ⅰ类、Ⅱ类盖层;山西组达到晚成岩C阶段的泥岩为Ⅲ类、Ⅳ类盖层,晚成岩B阶段的泥岩发育Ⅰ类、Ⅱ类盖层。工业性气流井分布在盖层封闭性能好的区域内,封闭性能评价结果与勘探实践相匹配。

According to basin drilling data,logging,core analysis,burial history,paleotempreture,etc.,the spatial distribu-tion,diagenesis and sealing capability evolution mode,porosity,permeability and breakthrough pressures of mudstone inthe Upper Paleozoic of south Ordos Basin were studied. And based on that,corresponding evaluation standard and methodwere proposed to make a comprehensive assessment of the sealing capability of mudstone in the Upper Paleozoic. The ob-tained results show that：classⅠmudstone caprock in the Shiqianfeng Formation developed with the best sealing capabilityin the south Ordos Basin,especially in well areas of Zhentan1 and Huangshen1 where the comprehensive evolution weight-ed value reaches 3.5;abnormal high pressures develop in the Upper Shihezi Formation,where classⅣcaprock distributeswidely with the worst physical sealing capability. ClassⅣmudstone caprock is developed in the Lower Shihezi Formation inthe west and the south of the research area and classⅠand classⅡcaprock are in the northeast. For mudstone in the ShanxiFormation,those at the late diagenesis C stage is classⅢor classⅣcaprock and those at the late diagenesis B stage is classⅠor classⅡcaprock. Industrial gas flow wells distribute in areas with good caprock sealing capability. The comprehensiveevaluation results coincide with the exploration practice,which can provide references for gas exploration of the south area.