鄂尔多斯盆地延安地区马五段上组合细粒白云岩储层特征及有利储层控制因素

针对鄂尔多斯盆地延安地区马五段上组合（马五4至马五1亚段） 细粒致密白云岩储层天然气勘探取得新突破，展开对 低孔低渗白云岩储层特征及孔隙的成因研究。通过岩心观察、薄片分析及阴极发光等测试，结合岩石物性分析，明确了细 粒白云岩储层的储渗特征、有利储层的演化过程及控制因素。结合地球化学及地球物理数据分析认为，研究区马五段上组 合储层岩性主要包括含膏模白云岩、细晶白云岩和岩溶角砾岩等，储集空间以膏模溶孔、晶间（溶） 孔、非选择性角砾间 溶蚀孔洞为主，局部裂缝发育，属低孔低渗孔隙型储集层；位于高古地势、经多期岩溶（准同生期、表生期和埋藏期岩 溶） 叠加改造的膏晶模云坪是研究区细粒白云岩有利储层的主要分布区。

Characteristics of Fine-Grained Dolostone Reservoirs and Controlling Factors of Favorable Reservoirs in the Upper Assemblage of Ma-5 Member in Yan’an Area of the Ordos Basin

A new natural gas exploration breakthrough has been gained in the fine-grained tight dolostone reservoirs of the Upper Assemblage of the Ma-5 Member in the Yan’an area of the Ordos Basin. This paper presents a detailed research on the characteristics of low-porosity and low-permeability dolostone reservoirs and the genesis of porosities. Through core observation, thin section analysis and cathodoluminescence testing, combined with rock physical property analysis, the porosity-permeability characteristics of the fine-grained dolostone reservoirs and the favorable reservoirs′ evolution process and controlling factors are clarified. Results show that the lithology of fine-grained dolostone reservoirs is mainly composed of gypsum pseudocrystal dolomite, fine-grained dolomite and karst breccia dolomite. The porosity types contain gypsum pseudocrystal dissolved pores, intercrystalline dissolved pores and non-selective breccia dissolved pores, with local fractures developing. Thus, it is a pore type reservoir with low porosity and permeability. The mould-pore-contained gypsodolomite flat, which is located at the high position and transformed by multi-stage karsts (penecontemporaneous, epigenetic and burial), is the main distribution area of favorable reservoirs of the fine-grained dolomite in the study area.