The carbonate rocks of the Majiagou Formation contain extensive oil and gas resources. To determine the rock type, sedimentary characteristics and sedimentary environment of the Ma51+2 submember, its sedimentary microfacies are distinguished via core observation, thin section analysis, scanning electron microscopy and cathodoluminescence analysis. On the basis of the sedimentary microfacies division, the sedimentary microfacies sequence is analyzed, and a sedimentary model is established to study the reservoir. The results show the following: i) The Ma51+2 submember is believed to be a 4th-order sequence, which can be divided into several 5th-order sequences according to the suborder sea level change, consisting of micritic dolomite with gypsum crystalline casting pores, grain dolomite, micritic dolomite and microbial carbonate. ii) The Majiagou Formation is concluded to have been deposited in a restricted evaporite platform sedimentary environment, which can be divided into four subfacies, namely, grain shoal, microbial mound, platform flat and lagoon subfacies. Specifically, the grain shoal subfacies is primarily composed of intershoal sea, shoal flank and shoal body microfacies, with the microbial mound subfacies largely divided into mound base, mound body and mound cap microfacies. iii) According to the 5th-order sea level changes and lithological characteristics, four typical vertical sedimentary microfacies sequences can be identified, and all are shallowing-upward sedimentary sequences. iv) The pore types in the study area are mainly gypsum crystalline casting pores, intergranular pores, intergranular dissolved pores, and dissolved pores, followed by intercrystalline pores, intercrystalline dissolved pores and fractures. v) The development of grain dolomite and microbial carbonate is influenced by sea level change, sedimentary sequence and paleogeomorphology, with the favorable reservoirs mainly affected by the sedimentary microfacies, dolomitization and dissolution.

马家沟组的碳酸盐岩蕴藏着丰富的油气资源。为了确定Ma51 + 2子岩的岩石类型，沉积特征和沉积环境，通过岩心观察，薄层分析，扫描电子显微镜和阴极发光分析来区分其沉积微相。在沉积微相划分的基础上，分析了沉积微相序列，建立了沉积模型研究储层。结果表明：i）Ma51 + 2的亚成员被认为是4阶层序，根据亚层海平面变化可分为几个5阶层序，该层序由含石膏的结晶白云岩组成，并具有石膏结晶铸孔。 ，粒状白云岩，变质白云岩和微生物碳酸盐。ii）认为马家沟组沉积物是在受限的蒸发岩平台沉积环境中沉积的，该环境可以分为四个亚相，分别为：浅滩，微生物丘，平台平和泻湖亚相。具体说来，粮食浅滩亚相主要由浅滩海相，浅滩侧面和浅滩体微相组成，微生物丘亚相大致可分为丘基，丘体和body盖微相。iii）根据五阶海平面变化和岩性特征，可以识别出四个典型的垂直沉积微相序，均为浅向上沉积序。iv）研究区的孔类型主要为石膏结晶铸孔，粒间孔，粒间溶解孔和溶解孔，其次是晶间孔，晶间溶解孔和裂缝。v）白云岩和微生物碳酸盐的发育受海平面变化，沉积层序和古地貌的影响，其中有利的储层主要受沉积微相，白云石化和溶解作用的影响。