Hydrocarbon Expulsion Efficiency and its Influencing Factors of the 5th Member of the Xujiahe Source Rock in West Sichuan Basin, China

Hydrocarbon expulsion efficiency of source rocks is one of the significant contents of oil and gas resources assessment, original hydrocarbon generation potential recovery method on the basis of the organic carbon mass balance principle was effective and realizable. For the study area in WSBC, T3X5 was fairly good source rock, characterized by moderate burial depth, large thickness, high organic content, and moderate-high maturity, and had a great potential for gas generation. The results indicated that the T3X5 black mudstones had higher discharge efficiency which was 3.32% to 65.48%, reaching the peak of hydrocarbon expulsion. KP was influenced by shale content, and decreased in the order interbedded>sand-rich>mud-rich>thick pure mudstone lithology combination. Positive correlations were found between organic matter aboundance and KP, suggesting that the higher organic matter abundance, the higher hydrocarbon expulsion efficiency. Large quantities of hydrocarbons were discharged when entering the oil-generating window (RO 1.0%∼1.2%), and then expulsive hydrocarbon amount decreased with Ro rise, at last, Kp kept stable in the over mature stage. Besides, hydrocarbon expulsion was also controlled by the developed overpressure which was conducive to micro-cracks.