贵州省黔北牛蹄塘组页岩微观孔隙研究

Study on the Microscopic Pore Structures of Shale in Niutitang Formation of North Guizhou

为了分析页岩微观孔隙发育及其控制因素,取牛蹄塘组页岩,通过扫描电镜、X射线衍射及等温液氮吸附实验手段,通过吸附滞回曲线、BET理论对孔隙形态分布进行研究,结果表明:矿物组成以石英、长石、黄铁矿等矿物为主,含量高达70%~91%,平均为82.8%,有利于后期的人工压裂和天然造缝;储层孔隙结构复杂,呈不规则球形、椭球形、月牙形等;通过实验牛蹄塘组页岩微孔比表面积所占比例较高,是比表面积主要贡献者,也是页岩甲烷吸附主要场所;在后期通过天然或人工预裂造缝,其渗透能力得到了明显的提高。

In order to analyze the microscopic development of shale and its control factors, the shale in Niutitang formation was taken as a rock specimen. Then, through the scanning electron microscope, X ray diffraction and liquid-nitrogen cryogenic adsorption, its microscopic pore structures were studied by adsorption-desorption curve and BET theory. The results indicated that the mineral mainly consisted of quartz, feldspar and pyrite. Its content was as high as 70%-91%, with the average of 82.8%, which was beneficial to the artificial fracturing and natural fracture. The reservoir pore structure was complex, presenting irregular spherical, ellipsoidal and crescent shape. Through the experiment, the microscopic specific surface area of shale in Niutitang formation had a high proportion, which was the main contributor to the specific surface area and was also the main place for methane adsorption in shale reservoirs. Through the artificial fracturing and natural fracture at the later stage, the infiltration capacity of shale had an obvious improvement.