Characteristics and Mechanism of Formation of Dolomite Reservoirs in the Eastern Margin of the Pre-Caspian Basin

Dolomitization is one of the important diagenetic processes for the Carboniferous carbonate rocks in the study area, and it is closely related to the formation of some carbonate reservoirs. By making full use of the images and data of relevant thin sections of rocks and cast thin sections, using the available geochemical analysis data and petrological characteristics with geochemical characteristics, this paper studies the dolomitization of the Carboniferous carbonate rocks, identifies the mineralogical characteristics, origins, and types of dolomite rocks, analyzes the geochemical characteristics of dolomite rocks, investigates the mechanism and mode of dolomitization, and analyzes the significance of dolomitization for the formation of reservoir spaces. The results of the study suggest that the study area involves multiple stages of dolomitization and multiple types of dolomite rocks, including syngenetic high-salinity powder crystalline-microcrystalline dolomite and microcrystalline-powder crystalline anhedral dirty dolomite, shallowly buried powder-fine crystalline euhedral dolomite formed during early diagenesis, moderately to deeply buried medium-coarse crystalline dolomite formed during the middle-late stages of diagenesis. Dolomitization of the Carboniferous rocks affects the distribution of reservoirs. All the types of dolomite rocks mentioned above feature high rates of conversion to reservoir rocks ranging from 67% to 81%.