HYDROCARBON CHARACTERISTICS OF PRIMARY AND SECONDARY GAS ACCUMULATION IN PINGLUOBA GAS FIELD IN WESTERN SICHUAN
川西平落坝气田原生与次生气藏烃类组成特征

Based on the system division of the primary and secondary gas accumulation, the paper depicts the different characteristics between primary and secondary gas accumulation of Pingluoba gas field in western Sichuan. Secondary gas accumulation can be divided into redistributed secondary gas accumulation, non\|redistributed secondary gas accumulation and mixed secondary gas accumulation, according to the relationship between gas accumulation and generating rock. Primary gas accumulation refers to these that lie above or under the generating rock and contact with or are near to it, or,lie inside the generating rock,The secondary gas in Pingluoba has high fixed hydrocarbon content and relative density, low methane content and little non\|hydrocarbon gas. The ratio of iso\|pentane to normal\|pentane of primary gas is similar to or a little higher than that of secondary gas,however, the ratio of iso\|butane to normal\|butane of secondary gas is higher than that of primary gas. In Jurassic in the region, the carbon\|isotope is heavier in primary gas than in secondary gas,at the same time, primary gas has more content of heavy residual hydrocarbon.