煤系页岩气储层非均质性研究——以宁武盆地太原组和山西组为例

储层非均质性是影响煤系页岩气勘探开发的主要瓶颈之一。以宁武盆地太原组和山西组泥页岩为研究对象,通过钻孔资料、TOC、XRD、扫描电镜、压汞及低温液氮测试,划分泥页岩发育层段,分析煤系页岩TOC、矿物成分、孔隙度、孔容、比表面积参数宏观非均质性及孔隙结构非均质性,探讨宏观—微观非均质性影响因素。研究表明:太原组和山西组泥页岩平均厚度分别为32.77m和67.68m,可划分为5个层段和4种暗色泥页岩类型,黑色页岩具有TOC、孔隙度、水敏性中等,脆性高特点,是最利于开发的优质储层段;微孔主要受黏土矿物含量影响,呈现出正相关关系,在黏土矿物含量较低时,微孔与TOC呈现正相关;煤系泥页岩宏观非均质性主要受沉积和构造影响,微观非均质性受成岩演化影响。研究成果可为优选煤系页岩气优质储层段和压裂工艺提供可靠依据。

Heterogeneity of Shale Gas Reservoirs in Coal Measures: A Case Study of the Taiyuan and Shanxi Formations in the Ningwu Basin

Reservoir heterogeneity is one of the main bottlenecks that affects the exploration and development of shale gas in coal measures. By analyzing the compositional and reservoir characters of the shale samples of Taiyuan Formation (Fm.) and Shanxi Fm. in Ningwu basin, the intervals and types of shale are divided. The macro heterogeneity of TOC, mineral porosity, surface area, pore volume and the micro heterogeneity of pore structure are analyzed to reveal the influencing factors of the macro - micro heterogeneity. The result shows that: the average thickness of the shale in Taiyuan Fm. and Shanxi Fm. are 32.77 and 67.68 m respectively, and can be divided in 5 intervals and 4 types of shale. According to the property parameters, the black shale with medium TOC, porosity, water sensitivity and high brittleness is high-quality reservoir which is most conducive for exploitation. The micro pores are mainly affected by the clay mineral content, showing a positive correlation, and TOC content is positively correlated with the micropore volume when the clay content is low. The macro heterogeneity of coal measure shale is mainly controlled by sedimentary and tectonic factors, and the micro heterogeneity is influenced by the diagenesis and evolution. The research results can provide a reliable basis for the selection of high quality reservoir and fracturing process of shale gas in coal measures.