西昌盆地白果湾组泥页岩储层特征及主控因素

Properties and Main Influences of Mud Shale Reservoir in the Baiguowan Formation,Xichang Basin

海陆过渡相富有机质泥页岩已在国内多个区块取得重要突破,以西昌盆地上三叠统白果湾组富有机质泥页岩为研究对象,基于岩性特征,运用铸体薄片观察、厚度对比、有机地化、全岩X射线衍射、孔隙度、渗透率、扫描电镜、高压压汞、低温N2吸附等技术手段,综合分析西昌盆地上三叠统泥页岩储层特征及其主控因素。结果表明:西昌盆地上三叠统白果湾组富有机质泥页岩有机碳含量介于0.3%~2.21%,平均为1.02%,有机质类型为Ⅱ2型和Ⅲ型;有机质成熟度介于1.02%~3.87%。富有机质泥页岩的厚度介于30~110 m,脆性矿物含量较高,为11%~77%,平均为40.5%。孔隙度介于1.28%~9.02%,平均为4.03%,渗透率在(0.001 7~0.146)×10^(-3)μm^(2)之间,平均为0.03×10^(-3)μm^(2)。比表面积介于6.25~13.7 m^(2)/g,平均为10.17 m^(2)/g,平均孔径为6.66~9.79 nm。有机碳含量与孔隙度具正相关性,研究区内泥页岩有机质演化程度分布不均,孔隙度与有机质成熟度之间具有正相关性,脆性矿物含量与孔隙度之间具微弱的正相关性,黏土矿物含量与孔隙度之间具有微弱的负相关性。总体而言,西昌盆地上三叠统白果湾组富有机质泥页岩储层具有良好的页岩气基础地质条件,具有较大的勘探与开发潜力。

The exploitation in China of organic-rich shale containing marine-land transitional facies for gas produc⁃tion has advanced considerably.This study of the organic-rich shale in the Upper Triassic Baiguowan Formation,Xichang Basin,was based on its lithological properties.A synthetic analysis reservoir potential included casting thickness,thin section observation and comparison,organic geochemical considerations,whole-rock XRD,porosity and permeability,SEM,N2 adsorption at low temperature,and high-pressure Hg injection.The organic carbon con⁃tent is in the range 0.3%-2.21%(average 1.02%).The OM types are II2 and III,with maturity 1.02%-3.87%.The de⁃posit is 30-110 m thick.Brittle mineral content is 11%v77%(average 40.5%).Porosity is 1.28%-9.02%(average 4.03%);permeability is 0.0017×10^(-3)μm^(2) to 0.146×10^(-3)μm^(2)(average 0.03×10^(-3)μm^(2)),with specific surface area 6.25-13.7 m2/g(average 10.17 m2/g).The average pore size is 6.66-9.79 nm.There is a positive correlation between organic carbon content and porosity.The degree of OM evolution in the study area is not uniform,and the porosity is positively correlated with maturity.Brittle mineral content is weakly positively correlated with porosity,and clay miner⁃al content is weakly negatively correlated with porosity.In general,the study indicates that this organic-rich shale pos⁃sesses basic geological conditions suitable for shale gas,and has considerable exploration and development potential.