细粒沉积岩优质储集层发育主控因素分析: 以渤海湾盆地沾化凹陷为例^*

Reservoir characteristics and distribution of lacustrine fine-grained sedimentary rocks:a case study from Zhanhua sag,Bohai Bay Basin,China

摘要

为了深化对湖相细粒沉积岩储集层的认识,以渤海湾盆地济阳坳陷沾化凹陷渤南洼陷沙三下亚段(Es3L)为研究对象,利用岩心描述、薄片鉴定、扫描电镜观察、物性分析和测井曲线,揭示了储集层特征、分布规律及其主控因素。基于矿物组成、沉积构造和有机质含量,将渤南洼陷Es3L细粒沉积岩划分为6类岩相: 富有机质纹层状灰质细粒混积岩(LF1)、富有机质纹层状长英质细粒碳酸盐岩(LF2)、富有机质层状灰质细粒混积岩(LF3)、富有机质层状/块状长英质细粒碳酸盐岩(LF4)、富有机质层状含长英细粒碳酸盐岩(LF5)、含有机质块状含长英细粒碳酸盐岩(LF6)。储集层的主要储集空间为粒间孔、晶间孔、溶蚀孔和层间微裂缝,储集层孔隙度主要介于0.67%~5.56%之间(平均值为4.93%),渗透率主要介于(0.02~4.87)×10^-3 μm²之间(平均值为0.59×10^-3 μm²)。渤南洼陷Es3L细粒沉积岩储集层分布的主控因素包括岩相、沉积环境、成岩作用和有机质热演化。渤南洼陷Es3L的中下部的陆源输入水平低、水体盐度大、水体分层性强,主要发育岩相LF2和LF4,容易发育Ⅰ类和Ⅱ类优质储集层。渤南洼陷Es3L细粒沉积岩储集层处于中成岩A阶段,黏土矿物转化作用、溶蚀作用、重结晶和白云石化以及有机质热演化产生次生孔缝,改善了储集层物性。

Abstract

In order to deepen the understanding of lacustrine fine-grained sedimentary rock reservoirs,this paper takes the Lower Sub-member of Third Member of Shahejie Formation(Es3L)of Bonan subsag in Zhanhua sag,Jiyang depression,Bohai Bay Basin as the research object,and uses core description,thin section identification,scanning electron microscope observation,physical property analysis and logging curve to reveal the reservoir characteristics,main controlling factors and distribution patterns. Based on mineral composition,sedimentary structure and organic matter content,fine-grained sedimentary rocks in Es3L are divided into six lithofacies: organic-rich laminated gray fine-grained mixed rock(LF1),organic-rich laminated felsic fine-grained carbonate rock(LF2),organic-rich layered gray fine-grained mixed rock(LF3),organic-rich layered/massive felsic fine-grained carbonate rock(LF4),organic-rich layered felsic fine-grained carbonate rock(LF5),organic-rich massive felsic fine-grained carbonate rock(LF6). The main reservoir spaces of the reservoir are intergranular pores,intergranular pores,dissolution pores,and interlayer micro-fractures. The reservoir porosity mainly ranges from 0.67% to 5.56%,with an average of 4.93%. The permeability mainly ranges from 0.02×10^-3 μm² to 4.87×10^-3 μm²(average of 0.59×10^-3 μm²). The dominant control factors for the distribution of the Es3L fine-grained reservoir development include lithofacies,sedimentary environment,diagenesis and thermal evolution of organic matter. In the middle and lower part of the Lower Sub-member of Third Member of Shahejie Formation,the amount of terrestrial input is low,the water salinity is high,and the water stratification is strong. The main lithofacies area LF2 and LF4,which are prone to the development of Class I and Class II high-quality reservoirs. The fine-grained reservoirs in Es3L are in the intermediate diagenetic stage A. The transformation of clay minerals,dissolution,recrystallization and dolomitization,as well as the thermal evolution of organic matter produce secondary pores and fractures,which improve the physical properties of the reservoir.

关键词

渤南洼陷 / 沙三下亚段 / 湖相细粒沉积岩 / 优质储集层 / 主控因素 / 分布规律

Key words

Bonan subsag / the Lower Sub-member of Third Member of Shahejie Formation / lacustrine fine-grained sedimentary rocks / high quality reservoir / main controlling factors / regularity of distribution

基金资助

*国家自然科学基金项目(编号: 42272110)资助。