近期,四川盆地中西部地区下二叠统栖霞组—茅口组的勘探取得持续突破,引起人们对白云岩储层的广泛关注.从储层形成的地质背景入手,以露头和岩心为切入点,结合实验分析,在储层成因与分布方面取得4项主要认识:①栖霞组和茅口组的白云岩储层均发育在高位域,台地边缘和台洼边缘是储层发育的主要沉积环境;②储层的主要岩性是晶粒白云岩(残余颗粒白云岩和中细晶白云岩),溶蚀孔洞、残余粒间孔、生物体腔孔和裂缝是主要储集空间,栖霞组和茅口组储层的平均孔隙度分别为3.87,、4.57,,均具良好的储集性能;③颗粒滩亚相、准同生溶蚀作用是储层形成的主控因素,其中颗粒滩是储层发育的物质基础和原生孔隙的载体,准同生溶蚀作用将原生孔隙扩溶成孔洞,是改善储集空间的关键;④剑阁—雅安台缘滩和盐亭—广安台洼边缘滩带是白云岩储层有利分布区,是天然气勘探的主攻方向.

Recently, continuous breakthrough have been made in the exploration of Qixia Formation and Maokou Formation in the western-central Sichuan Basin, which has attracted extensive attention to the dolomite reservoir. Based on the geological background of reservoir formation, taking outcrops and cores as the access point and combining with the experimental analysis, four significant conclusions on the genesis and distribution of reservoir are drawn: (1) Dolomite reservoirs in both Qixia Formation and Maokou Formation developed in the highstand systems tract. The platform margin facies and the syneclise margin facies are the main sedimentary environment of reservoir development.(2) Crystalline dolomite, including residual granular dolomite and medium to fine crystalline dolomite, is the main lithology of reservoir, and dissolution holes, residual intergranular pores, biological coelomic pores and fractures are the main reservoir space. Both the Qixia Formation with an average porosity of 3.87, and the Maokou Formation with an average porosity of 4.57, show good reservoir property. (3) Grain beach subfacies and penecontemporaneous dissolution are the two major controlling factors of reservoir formation. Grain beach is the material basis of reservoir development and the carrier of primary pore. Penecontemporaneous dissolution is the key to improve the reservoir space by enlarging primary pores into holes. (4) The marginal-platform shoals along Jian'ge-Ya'an and the marginal-syneclise shoals along Yanting-Guang'an are the favorable zones of dolomite reservoir development and the main target areas of gas exploration.