鄂尔多斯盆地姬源—陇东地区三叠系延长组长7段致密储层成岩作用

鄂尔多斯盆地姬源—陇东地区三叠系延长组长7段致密储层主要为发育在深湖亚相中的浊积岩，部分为三角洲前缘亚相中的水下分流河道砂体。前人对致密储层成岩作用的研究较少，需弄清成岩作用对致密储层孔隙发育的影响。通过铸体薄片与扫描电镜对大量钻井取心样品进行观察与分析，认为影响研究区长7段致密储层孔隙类型与规模的成岩作用主要包括压实压溶作用、胶结作用与溶解作用3种类型，压实作用是储层致密的主要因素，特别是发育在三角洲前缘分流间湾和浊积扇边缘的薄层砂体，在压力作用下更易受到泥岩排出孔隙水的影响，形成方解石胶结。伊利石胶结与方解石胶结进一步使得储层致密。少量的绿泥石薄膜成为残余粒间孔保留与包裹岩屑颗粒后期溶蚀的基础，溶蚀作用是研究区储层孔隙形成的主要作用。成岩作用的研究为储层物性的研究提供了进一步依据。

A study of tight reservoir diagenesis in the Chang 7 Member of Triassic Yanchang Formation, Jiyuan-Longdong area, Ordos Basin

Chang 7 Member is a tight reservoir in Triassic Yanchang Formation, Jiyuan-Longdong area, Ordos Basin. The tight reservoir is formed mainly in the deep lake sub-facies, and partly in the delta front sub-facies. The study of tight reservoir diagenesis has been very insufficient, and it is important to find out the effect of diagenesis on the development of reservoir pore. The samples collected from the core were observed and analyzed by casting lamella and scan electron microscope to reveal the influence of the main diagenetic activities such as compaction, cementation and dissolution on the pore type and pore size of the tight reservoir in the study area. Compaction is the main factor responsible for the formation of tight reservoir. The sand body in the bay of delta front distributary and the edge of turbidite fan is especially easier to form calcite cementation when the pore water is excluded from the mudstone under pressure. Illite cementation and calcite cementation makes the reservoir more dense. A small amount of chlorite films cementations form the residual intergranular pores and promote the mineral dissolution. Dissolution is the main function causing the reservoir pore formation in the study area. The diagenesis study constitutes the basis for the research on reservoir physical properties in the study area.