龙门山前陆盆地南段上三叠统须家河组页岩地层较发育,勘探程度低且具备页岩气成藏的可能性。基于野外剖面实测及定点采样、岩石热解实验、有机碳测定、镜质体反射率测试与分析等方法,结合岩心资料,综合分析页岩有机地球化学特征。 结果表明:区内须家河组页岩有机碳质量分数主要为 1.0%~2.0%,总体上达到一般—较好的生气标准;干酪根类型以Ⅲ型为主,Ⅱ2 型次之;有机质成熟度主要为 0.8%~1.7%,部分高于 2.0%,整体处于成熟—高成熟演化阶段。 通过系统对比区内须家河组各段页岩有机地球化学特征与孔隙度、埋藏深度、有效厚度等地质参数,评价出区内须五段与须三段均为页岩气勘探与开发的有利层段。
With the possibility of shale gas accumulation, the shale of the Upper Triassic Xujiahe Formation is well developed in the southern Longmen Mountain for-land basin, but the degree of prospecting is low. Based on the field profile mea-surement and fixed-point sampling, rock pyrolysis experiment, TOC determination, the test of vitrinite reflectance (Ro) and core data, the organic geochemical characteristics of shale was analyzed. The results show that the TOC content of shale ranges from 1% to 2%, reaching fair-good according to gas generation standards. Kerogen is mainly Ⅲ type, secondly Ⅱ2 type. Being from 0.8% to 1.7% generally, some above 2.0%, the maturity of organic matter is at the mature to high mature stage of evolution. Through the analysis of the organic geochemical characteristics and geologic parameters (porosity, burial depth and effetive thickness) of the shale of Xujiahe Formation, it is considered that the fifth member and third member of Xujiahe Formation are favorable for shale gas exploration in the southern Longmen Mountain foreland basin.