湘西北下寒武统牛蹄塘组页岩含气性影响因素分析

湘西北地区下寒武统牛蹄塘组发育了一套富有机质泥页岩，其分布稳定且厚度较大，在桑植石门复向斜一带埋深大，保存较完整。牛蹄塘组页岩气富集甜点区的页岩气质量体积为 1.48～8.75 m³/t，具有很好的工业开发价值。 有机碳含量既决定了页岩气的资源潜力，同时也影响页岩气的吸附和存储能力。对牛蹄塘组页岩气的研究认为：储集空间主要可分为原生晶间或粒间微孔隙、有机质微孔隙、不稳定矿物溶蚀孔、构造裂缝和解理缝等 5 种成因类型；页岩气较易发生吸附和解吸作用，吸附态气所占较大比例；页岩气存储状态主要受有机碳含量和储集空间类型的综合影响；高过成熟富有机质页岩生成的天然气在较好的保存条件下仍然可以聚集并成藏；温压条件、埋藏深度和矿物组成等对页岩含气性的影响均相对较小。

Influencing factors of shale gas-bearing property of Lower Cambrian Niutitang Formation in northwestern Hunan

The Lower Cambrian Niutitang Formation in northwestern Hunan developed a set of organic-rich shale which is characterized by stable distribution and large size, with great burial depth and relatively complete conservation in synclinorium of Sangzhi-Shimen area. The gas content of the enriched shale gas area of Niutitang Formation is between 1.48 m³/t and 8.75 m³/t, so these areas have a good potential of industrial development. Organic carbon content determines the resources potential of shale gas, and meanwhile affects the adsorption and storing capacity. There are five genetic types reservoir space, including primary intercrystalline or intergranular micropores, organic material micropores, dissolved micropores of unstable mineral, structural fractures and cleavage fissures. The adsorption and resolution of shale gas is easy to happen. The storage state of shale gas is under the combined influence of organic material content and the type of reservoir space. The natural gas generated by high and over-matured organic-rich shale can accumulate and form reservoir under good preservation conditions. Temperature, pressure, burial depth and mineral composition have little effects on the gas-bearing property of Niutitang Formation.