Main Controlling Factors and Enrichment Patterns of Carbonate Gas Reservoirs in Leikoupo Formation, Longgang Area

The T2l43 formation of the Middle Triassic Leikoupo Formation in the Longgang area of the central Sichuan Basin has developed carbonate reservoirs, characterized by high cloudification and large single well thickness. Previous studies generally believed that the Leikoupo Formation developed lithological gas reservoirs, with the characteristic of “one well, one reservoir”. However, in the rolling exploration of the Longgang area, there have been consecutive failures. Only by clarifying the main controlling factors and enrichment rules of the gas reservoirs in this area can we break the stagnant exploration situation for many years. This paper starts with multiple factors such as logging, sedimentation, structure, and gas reservoirs to establish a systematic gas reservoir evaluation system. On the one hand, through sedimentary microfacies research, it is confirmed that the Leikoupo Formation mainly develops granular flats, cloud flats, gray flats, and various types of lagoon microfacies, among which granular flats sedimentation is the main reservoir in the area; On the other hand, through the implementation of structural traps, the study area is controlled by the Yilong-Yingshan structure and mainly develops long axis anticlinal traps with a northwest direction. The production wells are all located within the structural traps. The research results indicate that the Leikoupo Formation in Longgang area mainly develops structural gas reservoirs controlled by low amplitude traps, and the structural traps with a certain scale under the sedimentary background of granular shoals are gas accumulation areas.