湘鄂西地区下寒武统牛蹄塘组页岩气聚集条件及含气性影响因素

Conditions of Shale Gas Accumulation and Gas-bearing Factors of Lower Cambrian Niutitang Formation in Western Hu'nan and Hubei

以钻井、野外露头测量、实验测试数据为资料依据,通过对湘鄂西地区下寒武统牛蹄塘组页岩有机碳含量、热演化程度、矿物含量、储集特征等的分析,认为牛蹄塘组页岩全区分布,富有机质页岩发育于牛蹄塘组中下部,分布稳定,厚度介于40~150m之间;有机碳含量高,介于2.0%~14.64%之间;热演化程度高,主体大于2.0%以上,综合评价页岩品质好。等温吸附实验表明,牛蹄塘组页岩具有较强的天然气吸附能力。现场解吸实验表明,牛蹄塘组含气量整体偏低且氮气含量高。多期构造运动的改造和大型通天断层的发育是影响牛蹄塘组页岩含气性的主要因素,过高的热演化程度对含气性亦有一定影响。

Based on the comprehensive evaluation of drilling, field outcrops and experimental test data, the shale inLower Cambrian Niutitang Formation in western Hu1 nan and Hubei is of good quality. The organic-rich shale in the middle and lower parts of Niutitang Formation has a large thickness（40-150m）, high organic carbon content （2.0%？ 14.64%）,and high degree of thermal evolution（R.mainly more than 2.0%）. Isothermal adsorption experiments show that Niutitang shale has a strong natural gas adsorption capacity. Field desorption experiments show that the overall gas content in Niutitang Formation is low but the nitrogen content is high. According to the comprehensive analysis,the multiple phases of tectonic movement and large-scale faults are the main factors affecting the gas-bearing capacity of Niutitang shale,while the excessive thermal evolution is a secondary factor.