奥陶系盐下白云岩储层是鄂尔多斯盆地中东部天然气勘探的重要接替领域.基于钻井岩心、微观薄片、物性分析及地球化学特征等资料,应用微区多参数实验分析方法,对奥陶系盐下白云岩储层特征、成因与分布开展了系统研究.结果表明:①奥陶系盐下主要发育颗粒滩白云岩和微生物白云岩储层,其中颗粒滩白云岩储层岩性为砂屑白云岩、鲕粒白云岩和粉—细晶白云岩,储集空间由溶蚀孔洞、粒间孔、晶间(溶)孔和裂缝组成,平均孔隙度为6.04,;微生物白云岩储层岩性为凝块石白云岩,储集空间为溶蚀孔洞和微裂缝,平均孔隙度为5.64,.②奥陶系盐下白云岩储层孔隙来源于对颗粒滩和微生物丘中原生孔隙的继承,并经受了溶蚀作用、白云石化作用,以及膏盐矿物、石英、细—中晶白云石与方解石等充填作用的改造.③有利储层主要分布于中央古隆起、横山隆起及乌审旗坳陷中的低凸起带上.

The Ordovician pre-salt dolomite reservoir is an important replacement field for natural gas exploration in Ordos Basin. Based on drilling core, thin section, physical analysis, geochemical characteristics and other related information, the characteristics, genesis and distribution of the Ordovician pre-salt dolomite reservoir are systematically studied by using the method of multi-parameter analysis in micro-region. The results showed that: (1)The granular shoal dolomite reservoir and microbial dolomite reservoir are mainly developed in the Ordovician pre-salt. The reservoir lithology of granular shoal dolomite is arenaceous dolomite, oolitic dolomite and very fine-fine crystalline dolomite, the pore space is composed of dissolved pores, intergranular pores, intercrystal (dissolved) pores and fractures, and the average porosity is 6.04,. The lithology of microbial dolomite is thrombolite dolomite, the pore space is composed of dissolved pores, dissolved vugs and micro-fractures, and the average porosity is 5.64,. (2)The pores of the Ordovician pre-salt reservoir inherited the primary pores of granular shoal and microbial dolomite which suffering from the dissolution, dolomitization, the mineral filling of gypsum, salt, quartz, finely-medium crystalline dolomite and calcite. (3)It is predicted that the favorable reservoir is mainly distributed in the central paleo-uplift, the Hengshan uplift belt and the low uplift zone of Wushenqi depression.