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利用地化测试、扫描电镜和岩心观察等对凤冈地区牛蹄塘组页岩特征进行了研究,根据FC1井现场页岩气解吸数据,分析了页岩的含气性。结果表明:页岩有机碳含量在4%~28%,有机质热成熟度介于2.66%~2.95%,有机质类型为Ⅰ型,孔隙度和渗透率都较低;页岩内部以石英等脆性矿物为主,黏土矿物含量低,硅质是生物成因;通过扫描电镜发现页岩内部以有机质孔、粒间孔为主,发育有大量的铸模孔、溶蚀孔和微裂隙;岩心观察发现页岩的裂缝非常发育;FC1井现场解吸气含量在0.39~1.97 m3/t,总含气量在0.87~4.13 m~3/t,含气性较差;方解石破碎带含气性较好;强烈的构造运动产生的裂缝不利于页岩气的保存。
The characteristics of shale in Niutitang Formation in Fenggang area were studied by geochemical test, scanning electron microscopy and core observation. According to the on-site shale gas desorption data in FC1 well, the gas content of shale was analyzed. The results show that the shale has organic carbon content between 4% and 28%, organic matter thermal maturity between 2.66% and 2.95%, organic matter type Ⅰ and low porosity and permeability. In the shale, brittle minerals such as quartz , The content of clay minerals is low, and the silicagel is the biogenic cause. Through scanning electron microscopy, the organic matter pores and intergranular pores in the shale are found mainly by scanning electron microscopy. There are a large number of mold holes, dissolution pores and micro-cracks developed in the shale; The fractures are well developed. The desorbed gas content in the well of FC1 ranges from 0.39 to 1.97 m3 / t with a total gas content of 0.87 to 4.13 m 3 / t, with poor gas-bearing properties. The calcite fractured zone has good gas-bearing properties and a strong structure Cracks caused by the movement are not conducive to the preservation of shale gas.