Abstract:

Multiple sets of marine mud and shale in the Lower Paleozoic Cambrian were widely developed in the southern part of
Sichuan basin. As a set of good hydrocarbon source rock in Sichuan basin, the Longmaxi Formation has the potential to produce good quality shale gas. Based on the drilling data, core samples, outcrop data and geochemical experimental analyses of core samples of ChangNing and Weiyuan region, we have researched lower Silurian Longmaxi organic matter characteristics and their impacts on the enrichment regularity of shale gas. The results showed that the main types of organic matter are type I and II1 in the study region. Organic carbon content is very high (average TOC=2.52%), and the thermal evolution level is high (Ro=2.1%~3.5%). The organic matter has strong influence on the enrichment of shale gas. Kerogen type determines the methane adsorption capacity, the organic carbon content, and thermal evolution level determines the amount of product and the content of gas in the shale. Also, the high TOC and Ro can promote organic micro pore growth to increase more favorable space for the enriched shale gas. On the whole the Longmaxi Formation has a superior organic matter characteristics that strongly influence shale gas enrichment.

Key words: Longmaxi formation；shale gas；enrichment regularity；organic matter characteristics；gas content