五峰组—龙马溪组储层特征及甜点层段评价——以昭通页岩气示范区A井为例

以昭通页岩气示范区A井五峰组—龙马溪组一段页岩为主要研究对象,利用薄片、氩离子抛光-场发射电镜、核磁共振、液氮吸附、X衍射及地化分析等多种测试手段,从岩石学、有机地化、矿物组成、孔隙类型及结构、物性特征及含气性等方面,系统评价了五峰组—龙一段各小层储层特征,并优选了页岩地质与工程甜点层段。结果表明:五峰组—龙一段以硅质页岩为主,优质页岩主要形成于海侵期-海退早期的深水陆棚相贫氧-厌氧环境;有机质孔和黏土矿物层间粒内孔最为发育;五峰组—龙一段储层孔隙以中孔为主,微孔对比表面贡献最大,而中孔和微孔提供了主要的孔体积;龙一11—龙一21小层相对其他层段,具有相对高的TOC含量、孔隙度、含气量及压力系数,且各项指标具有向上减小或降低的趋势。同时,龙一11—龙一21小层具有高脆性指数、高杨氏模量、低泊松比的岩石力学特征;基于地质与工程综合评价,优选龙一11—龙一21小层即富碳高硅页岩段为纵向上甜点层段,为昭通页岩气示范区水平井的靶体层段。

Characteristic of the shale gas reservoirs and evaluation of sweet spotin Wufeng-Longmaxi Formation:A case from the A well in Zhaotong shale gas demonsration zone

The shale in Wufeng Formation and 1th member of the Longmaxi Formation of the Well A in Zhaotong shale gas demonstration zone is taken as the research object in this study.Using thin section,scanning electron microscope,field emission electron microscope,nuclear magnetic resonance,liquid nitrogen adsorption,X-ray diffraction,geochemical analysis and other testing methods,based on the petrology,organic geochemical and mineral composition,physical properties,pore types and structure characteristics and hydrocarbon content,the reservoir characteristics of Wufeng-1th member of the Longmaxi Formation were evaluated,and the longitudinal shale gas sweet spot of the geological and engineering was optimized.The results show that the Wufeng-1th member of the Longmaxi Formation is mainly composed of siliceous shale,and the shale was mainly formed in the early transgressive period-regressive deep-water shelf facies poor oxygen-anaerobic environment.Bore organic matter and clay minerals content interlayer intragranular were mostly developed.Wufeng-1th member of the Longmaxi Formation reservoir porosity is mainly composed of medium holes,while microporous accounts for the largest contribution to the surface,and the medium holes and microporous provides the main pore volume.Long11-Long21 sublayer relative to other sublayers has a relatively high TOC,porosity and gas content,and the indicators with upward trend to minimize or reduce.At the same time,the Long11-Long21 sublayers have the rock mechanics characteristics of high brittleness index,low young’s modulus and Poisson’s ratio.Based on the geological and engineering comprehensive evaluation,the Long11-Long21 sublayers namely carbon-rich high silicon shale section is a sweet spot in vertical section,and it’s also the horizontal well target segments in the Zhaotong shale gas demonstration zone.