湘鄂西牛蹄塘组页岩全孔径表征

Whole-aperture characteristics of the Niutitang Formation shale in the Western Hunan-Hubei area

我国南方地区下寒武统牛蹄塘组页岩展布面积广、厚度大。为了探索上扬子板块页岩有利勘探方向,运用地球化学实验、X-射线衍射分析、扫描电镜、JMVision软件分析、高压压汞、低温CO2和N2吸附等实验方法对湘鄂西寒武系牛蹄塘组页岩特征与全孔径分布特征进行研究。研究结果表明,该地区页岩干酪根为I型,总有机碳含量在1.3%~5.0%,平均3.4%,成熟度在3.16%~3.62%,平均3.37%。页岩储层主要矿物组成为碎屑矿物、黏土矿物、碳酸盐岩和少量黄铁矿,主要类型为硅质页岩,钙质和泥质页岩较少。储层发育有机孔、粒间孔、粒内孔、晶间孔、溶蚀孔和裂缝等多种成因类型孔隙。牛蹄塘组页岩总的孔体积在0.006~0.012 cm3/g,总的孔比表面积在16~36 m2/g。贡献孔体积最多的是中孔,微孔次之,宏孔最少,微孔贡献了绝大多数的孔表面积,中孔贡献了少量,宏孔几乎不贡献。类比焦石坝地区页岩全孔径分布特征,结果显示牛蹄塘组页岩微孔发育较好,以吸附气为主,是湘鄂西地区页岩气有利的勘探方向。

In south our country,the lower Cambrian Niutitang group shale has wide distribution and large thickness.In order to explore shale gas exploration direction on the Upper Yangtze plate,using geochemical experiment,X-ray diffraction analysis,scanning electron microscopy( sem),JMVision software analysis,high-pressure mercury injection,low temperature CO2 and N2 adsorption experiment,we have researched characteristic and the pore size distribution of Cambrian Niutitang Formation shale in Western Hunan-Hubei region.The results show that shale kerogen is type I,the content of TOC is between 1.3% ~ 5.0%,average value is 3.4%,maturity is between3.16% ~ 3.62%,the average of 3.37% in this area.Main composition of shale reservoir are detrital mineral,clay mineral,carbonate mineral and small amounts of pyrite,the majority are siliceous shale,the minority are calcium and less clay shale.Reservoir develops multiple genetic types of microscopic pores,including organic pore,inter-granular pore,intra-granular pore,intra-crystalline pore,dissolution pore and fracture,etc.The total pore volume of the Cambrian shale is 0.006 ~ 0.012 cm3/g,total specific surface area is 16 ~ 36 m2/g in range.Main contribution to the pore volume is mesopore,micropore less,macropore at least,micro-pore contributed most of the specific surface area,mesopore contribution in small,macropore is almost no contribution.By analogy with pore diameter distribution of shale in Jiaoshiba area,the results show that the micropore development of the Niutitang Formation shale is better,the type of gas are mainly adsorbed gas,it's a favorable exploration direction for shale gas in the western region of Hunan-Hubei.