准噶尔盆地白家海地区西山窑组深部煤岩储层孔隙结构表征及发育主控因素

Pore structure characterization and main control factors of deep coal reservoir of Xishanyao Formation in Baijiahai area,Junggar Basin

深部煤岩储层孔隙结构特征对深层煤层气勘探开发十分重要,为了明确深部煤岩储层孔隙结构特征及发育主控因素,以准噶尔盆地白家海凸起及周缘侏罗系西山窑组煤层为研究对象,运用覆压孔渗、扫描电镜、高压压汞、低温液氮吸附、二氧化碳等温吸附等多种试验方法,对西山窑组煤岩储层特征进行研究。结果表明:西山窑组煤岩演化程度低,显微组分以镜质组和惰质组为主,具有低水分、特低灰和低挥发分的特点;西山窑组煤岩储层发育孔缝双重介质储集空间,储层物性好;西山窑组煤岩储层可以划分为3种类型,Ⅰ类储层储集性能好,但渗透性能差,Ⅱ类储层是研究区主要储层类型,进一步分为Ⅱ_(1)类和Ⅱ_(2)类,Ⅱ_(1)类储层具有中等储集性能和良好渗透性能,Ⅱ_(2)类储层与Ⅲ类储层均以微孔为主,物性较差;西山窑组煤层孔隙结构主要受灰分质量分数、镜质组体积分数、惰质组体积分数和埋深控制。

Understanding the pore structure characteristics of deep coal reservoir is crucial for exploring and developing deep coal bed methane.This study focuses on the coal seam of the Jurassic Xishanyao Formation in Baijiahai Bulge and its surrounding areas in the Junggar Basin,employing various experimental methods such as porosity and permeability under overburden pressure,scanning electron microscopy,high-pressure mercury injection,low-temperature liquid nitrogen adsorption,and carbon dioxide isothermal adsorption to analyze coal reservoir characteristics.The results indicate that the coal of Xishanyao Formation features low water content,ultra-low ash content,low volatile matter,and a low degree of evolution,predominantly comprising vitrinite and inertinite macerals.The coal reservoir of Xishanyao Formation exhibits a dual medium of pore-fracture reservoir space,demonstrating favorable reservoir properties.The coal reservoirs of Xishanyao Formation can be classified into three types.Types I has high porosity but poor permeability.Types II is the predominant reservoir type in the study area,which is further divided into Types Ⅱ_(1) and Types Ⅱ_(2).Types Ⅱ_(1) has medium porosity with good permeability.Types Ⅱ_(2) and Types III are characterized by micropores and poor reservoir properties.The pore structure of these coal reservoirs in Xishanyao Formation is primarily controlled by factors such as ash mass fraction,vitrinite volume fraction,inertinite volume fraction,and burial depth.