湘鄂西-渝东地区牛蹄塘组页岩气勘探前景评价

The Shale Gas Exploration Prospect Assess of the Niutitang Formation in Western Hubei and Hunan-Eastern Chongqing

综合利用沉积学、岩石学和地球化学分析手段,对湘鄂西-渝东地区下寒武统牛蹄塘组（与水井沱组对应）黑色页岩的页岩气形成物质基础（沉积相、岩性、有机质丰度及类型、成熟度等）、储集层特征（孔隙类型、X衍射特征）进行系统性研究后发现：①研究区牛蹄塘组以深水陆棚相沉积的黑色页岩、硅质页岩为主,厚度较大,分布广泛;②其w（TOC）平均值达1.84%,成熟度为2%-6%不等,达到成熟-过成熟阶段;③页岩孔隙类型以粒间孔、石英粒内溶孔、黄铁矿晶间孔为主,另有少量黏土矿物溶蚀孔洞;④页岩中石英质量分数为50%-80%不等,与美国Branett页岩具有较强的相似性,均呈两段式。对于页岩气勘探前景评价而言,除了优越的页岩气物质基础条件外,后期硅化程度、埋藏深度、后期构造改造强弱等因素同样起着举足轻重的作用。

Make full use of sedimentology,petrology and geochemistry analysis,systematic research were carried out on the material basis（sedimentary facies,lithology,organic matter abundance,type,maturity,et al）and reservoir characteristics（pore types,characteristics of X ray diffraction）of the shale gas within lower Cambrian Niutitang Formation in western Hubei and Hunan-eastern Chongqing.The results show that：①The Niutitang Formation was dominated by black shale and siliceous shale which indicate a deep-water shelf facies,and hydrocarbon source rocks are thick and cover a wide area;②The average TOC is 1.84%,Ro is generally 2%-6%,it′s a set of mature late-mature stage of hydrocarbon source rocks;③Reservoir pore in black shale includes intergranular pores,intragranular dissolved pore in quartz,pyrite intergranular pores,and a small amount of clay mineral dissolution pore;④Quartz content of shale is ranging from 50%to 80%,which is similar to Barnett shale in USA,and both are two-stage;For the assessment of shale gas exploration prospect,the degree of silicification and tectonic,burial depth also play an important role,except for good material basis.