HYDROCARBON ACCUMULATION CONDITIONS OF LONGWANGMIAO FORMATION IN THE FRONT AREA OF THE DABA MOUNTAIN

Significant natural gas has been discovered in the Longwangmiao Formation of the central Sichuan Basin. However, the Longwangmiao Formation in the front area of the Daba Mountain has remained an area lacking breakthrough. In this paper, we made a thorough review of the hydrocarbon accumulation conditions started from source rock, followed by sedimentary facies, reservoirs, structural conditions and other aspects, and discussed the hydrocarbon accumulation conditions of the Longwangmiao Formation in the front area of the Daba Mountain. Our results suggest that: (1) High-quality source rocks do occur in the Qiongzhusi Formation of Cambrian in this area and may provide good organic matters for hydrocarbon generation; (2) The main reservoir space of the Longwangmiao Formation in the study area are intergranular and intercrystalline dissolved pores with low porosity and low permeability. Reservoirs, however, may well developed in the Chengkou-Fengjie-Xingshan-Lichuan area where karstified carbonate beaches are well developed along the margin of platforms. (3) There are favorable assemblages of oil and gas accumulation conditions in the Cambrian of the region, which include the source rocks from Qiongzhusi Formation, reservoir of Longwangmiao Formation and a thick salt cover of Gaotai Formation. Trap forming time matches well with the timing of oil and gas migration, which is conducive to oil and gas accumulation. Based on the study of hydrocarbon accumulation conditions, it is believed that the Chengkou-Wushan area is the most favorable area for future oil and gas exploration.