鄂尔多斯盆地海陆过渡相富有机质泥页岩特征及页岩气意义

Characteristics of marine-continental transitional organic-rich shale in the Ordos Basin and its shale gas significance

以鄂尔多斯盆地石炭系—二叠系海陆过渡相富有机质泥页岩为研究对象,通过岩石热解分析、岩石抽提和族组分分析、有机元素分析以及煤岩光学分析等方法,对泥页岩中有机质丰度、类型、热成熟度、生烃潜力等地球化学特征参数进行测试;利用扫描电镜、X射线衍射、物性测试等手段,对泥页岩中矿物组成、孔渗特征等储层评价参数进行分析。研究结果表明:鄂尔多斯盆地海陆过渡相地层中泥页岩分布广泛,埋藏偏深,单层厚度较薄,但累计厚度大;泥页岩中有机碳(TOC)含量平均为2.5%,丰度较大;有机质母质中干酪根类型主要为Ⅲ型;镜质体反射率(Ro)平均为1.2%,热演化程度达到中-高成熟阶段;具有较大的生烃潜力(S1+S2);同时,石英、长石等脆性矿物含量较高;发育多种孔、缝类型;保存条件良好,为页岩气提供有利的成藏环境。

In this study,the C-P marine-continental transitional organic-rich shale in the Ordos Basin was investigated by means of rock pyrolysis analysis,rock extraction and group analysis,organic element analysis and coal optical analysis to test the geochemical parameters,such as organic matter type,abundance,maturity and hydrocarbon generation potential.Utilizing SEM,XRD and physical property measurement,the mineral composition and the characteristics of porosity and permeability have been analyzed.The results proved that the marine-continental transitional organic-rich shale in the Ordos Basin distributes widely and has the characteristics of diminutive individual thickness but huge cumulative thickness.The content of TOC is about2.5%,organic matter type is mainly Ⅲ,and ROis about 1.2%.Hydrocarbon potential（S1＋S2）is at the stage of massive gas generation.Percentage of quartz and feldspar is high,various porosity and crack type could be found,and preservation of shale reservoir is well.All of these conditions provide the favorable environment of shale gas formation.