黔西北下寒武统牛蹄塘组页岩气成藏条件与有利勘探区预测

Gas Accumulation Conditions of Lower Cambrian Niutitang Shale and Prediction of Potential Zones in Northwestern Guizhou

以野外露头调查、老井复查和岩心样品测试等为基础,通过现场解吸实验和等温吸附模拟的含气性分析,认为黔西北下寒武统牛蹄塘组岩性主要为深水陆棚黑色碳质页岩和浅水陆棚粉砂质页岩,其中富有机质页岩段为牛蹄塘组底部的碳质页岩。页岩沉积厚度大(大于39m)、分布稳定。有机质类型主要为Ⅰ型干酪根,有机碳含量较高(富有机质页岩段平均大于5%),有机质热演化程度处于高—过成熟阶段;页岩储层中微裂缝、微孔隙发育,具较好的孔隙度(平均5.14%)和渗透率(0.011 4×10-3μm2),含气量大(平均1.3 m3/t),具有良好的气资源潜力。预测金沙—息烽以及仁怀两个地区为页岩气勘探有利区。

The Lower Cambrian Niutitang shale is wide and stably distributed in northwestern Guizhou. It consists of deep-water shelf carbonaceous shale and shallow-water shelf silty shale with large sedimentary thickness （﹥39m）, in which the black carbonaceous shale at the bottom of Niutitang Formation is organic-rich. Organic geochemical analysis shows that it is characterized by predominant Type-Ikerogen, high TOC values （TOC 〉5% in the organic-rich black shale） and high mature to overmature organic matter in thermal evolution. Microfractures and micropores are developed in the shale reservoirs, which are of relatively high porosity（mean 5.14%） and permeability（mean 0.0114×10-3μm2）. The high content of gas（1.3m3/t in average） means a good potential of shale gas resources. It is predicted that Jinsha-Xifeng and Renhuai areas are potential for shale gas prospecting.