Abstract:In recent years, multiple high-yield economically viable gas flow wells have been drilled in the Qixia Maokou Formation in the Hechuan area, indicating its promising exploration. However, overall exploration in the area still at a low level, and the reservoir characteristics and genesis not been understood, leading to difficulties reservoir evaluation and prediction. Reservoir characteristics analysis was conducted by core samples, thin sections, imaging, and porosity-permeability data, samples were selected for tests of the SEM with Ar-ion Milling and industrial CT. Obtaining three aspects of understanding: The Qixia Formation-Maokou Formation dolomite in the Hechuan area of the Sichuan Basin is mainly developed in three types: crystalline dolomite, dolomite with lime and calcareous dolomite, of which crystalline dolomite is the most important reservoir lithology and the main reservoir space carrier. The dolomite reservoir of the Qixia Formation is dominated by intercrystal pores, which are relatively uniformly developed and have the overall characteristics of medium to high porosity and medium permeability. The dolomite of the Maokou Formation is mainly dominated by vugs and dissolution fractures, there is also a certain amount of heterogeneous distribution of intercrystal pores, with an overall medium-high porosity and medium-high permeability character. Reservoir microscopic characterisation based on industrial CT reveals that intercrystal pores are relatively homogeneous in the Qixia Formation dolomites, whereas the Maokou Formation dolomites are strongly heterogeneous, and both develop independently of fractures, reflecting that these pores are the inheritance of earlier pores; Reservoir microscopic characterisation based on SEM with Ar-ion Milling reveals that micro-pores associated with crystal defects exist in both the Qixia and Maokou Formations, it suggests that in addition to vugs, intercrystal pores and micro pores also significant contributions to the reservoir properties. The research results effectively guide the evaluation of dolomite reservoirs in the Qixia Maokou Formation in the Hechuan area.