湘鄂西下志留统龙马溪组页岩含气性测井评价

Gas Content Logging Evaluation of Lower Silurian Longmaxi Shale in Western Hunan-Hubei

测井评价技术具有纵向上信息连续且分辨率高的优势,利用测井技术评价页岩含气性,能经济并有效地指导页岩气勘探。遴选了与湘鄂西龙马溪组页岩地质参数密切相关的测井曲线,应用合适的计算模型对有机地球化学、储层物性和含气性参数进行预测和评价。测井评价结果显示该地区龙马溪组页岩有机质丰度高,孔隙度较低,含气饱和度高,吸附气含量较游离气多,总含气量较高,平均为1.705 m3/t。通过对3段页岩气层的研究,认为含气量与TOC和孔隙度成正相关关系,且单位TOC的含气量和孔隙度在页岩底部会明显升高,为页岩底部储集空间大、封闭性强、天然气逸散能力弱所致,说明该地区龙马溪组页岩层底部具有较强的页岩气富集能力。

Logging evaluation technology shows a unique advantage in high resolution and continuous information in the longitudinal direction. Logging evaluation can be used to evaluate the shale gas content and then economically and effectively guide shale gas exploration. The logs closely related to the geology of Longmaxi shale in western Hunan- Hubei are taken and appropriate calculation models are used to forecast and evaluated organic geochemistry,reservoir properties and gas content parameters. Logging evaluation illustrates that Longmaxi shale is characterized by high organic matter abundance,relatively low porosity,high gas saturation,higher adsorbed- gas content than free- gas content and relatively high total gas content with 1. 705 m3/ t on average. Research of 3 shale reservoirs demonstrates that there is a positive correlation between shale gas content and TOC,porosity. The shale gas content per unit of TOC and porosity significantly increase in the shale bottom,which result from large reservoir space,strong confining capacity and weak gas effusion in the shale bottom. This also shows rather strong shale gas enriching capacity of Longmaxi shale bottom.