川南地区龙马溪组有机质特征及其对页岩气富集规律的影响研究

摘要

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.%四川盆地南部（简称“川南”）广泛发育多套下古生界海相泥页岩层系，其中龙马溪组为该区一套优良的烃源岩层，具备优越的页岩气形成条件。根据长宁和威远页岩气探区的钻井岩心、露头样品分析资料，对川南地区下志留统龙马溪组页岩有机质特征及其对页岩气富集规律的影响进行研究后表明，川南龙马溪组页岩的有机质类型为Ⅰ～Ⅱ1型，有机碳含量较高（平均为2.52%），热演化程度为2.0%～3.8%，达到了高-过成熟阶段；研究区的有机质特征对页岩气的富集具有重要的影响，干酪根的类型决定着甲烷吸附能力强弱，有机质丰度和有机演化程度决定了页岩的生气量和含气量，同时高TOC和Ro也能促进有机质微孔隙的发育，为页岩气的富集提供更多有利空间。因此，研究认为川南地区龙马溪组有机质特征较好，有利于页岩气的富集成藏。