Reservoir Characteristics and Main Controlling Factors of Maokou Formation in Central Sichuan Basin

Maokou Formation in central Sichuan has thin reservoir, low porosity and low permeability, strong heterogeneity, and unclear understanding of reservoir distribution law and controlling factors, which makes it difficult to determine the scope of favorable development area. Based on the comprehensive analysis of core description, rock chemical analysis, thin section identification, drilling and logging, logging and seismic data, it is found that the reservoir rocks of Maokou Formation are mainly dolomite, callitic dolomite and dolomitic limestone. With the increase of dolomite content, the reservoir physical property becomes better. The reservoir space is mainly dominated by dissolution pore, intergranular pore and intergranular dissolution pore. The average porosity is 4.3% and the average permeability is 4.71 mD. The reservoir of Maokou Formation in central Sichuan is mainly the residual fine-medium crystalline dolomite and calcareous dolomite formed by karstification and dolomitization of sedimentary grain beach in the high part of ancient landform. The reservoir space and permeability of the reservoir are greatly improved by the karst and cloudification of the high part of the ancient landform. Based on the single well logging interpretation reservoir, combined with sedimentary facies, karst paleogeomorphology distribution map and trace integral seismic data volume, the reservoir distribution is predicted. It is clear that the average reservoir thickness of the well is 7 m, and the thickness area is southward along the MX145-MX39 well. The average thickness of single well high quality reservoir is 2.7 m, the average thickness of MX145-TS4 well area is more than 6 m, and the remaining blocks are generally less than 3 m.