Characteristics of Longwangmiao reservoirs in Penglai gas area and comparison with those in Moxi-Gaoshiti area, central Sichuan Basin

The Longwangmiao Formation in the Penglai gas area has encountered good carbonate reservoirs and good gas shows. It has become one of the key exploration areas of the Longwangmiao Formation after the Anyue gas field in the central Sichuan area. However, the unclear reservoir development law restricts exploration deployment. Based on the latest drilling and testing data, the reservoir characteristics and main controlling factors of Longwangmiao Formation in Penglai gas area are systematically analyzed. The study shows that the Longwangmiao Formation in Penglai gas area has a mixed sedimentary background of terrigenous debris and carbonate, and the reservoirs are mainly distributed in the upper part of the Longwangmiao Formation. The reservoir rock types are mainly (residual) granular dolomite and crystalline dolomite. The reservoir space types are mainly intergranular dissolved pores, intragranular dissolved pores, intercrystalline dissolved pores and microfractures. The reservoir is mainly composed of low porosity and low permeability reservoirs, and the reservoir thickness is mainly between 10-42 m.Reservoir development is controlled by sequence stratigraphy, lithology and diagenesis. The (residual) granular dolomite and crystalline dolomite in the middle and upper parts of the progradational parasequence set and parasequence are the main parts of reservoir development. Atmospheric freshwater dissolution, oil and gas dissolution and fracture are the core constructive diagenesis. Compared with the Moxi-Gaoshiti area in the main area of Anyue gas field, it is considered that the main controlling factors of the reservoir are similar, which are mainly controlled by granular dolomite, dissolution and fracturing. However, the Longwangmiao Formation reservoir in Penglai gas area has the characteristics of high ash content, high terrigenous clastic content and weak penecontemporaneous exposure. Looking for high-energy granular dolomite and fine-grained dolomite exposed in the penecontemporaneous period and dolomite modified by supergene karst are the key reservoir targets in Penglai gas area.