阳春沟构造带页岩裂缝发育特征及对产能的影响

以渝东南地区阳春沟构造带上奥陶统五峰组-下志留统龙马溪组页岩为研究对象,通过岩心观察、成像测井解释(FMI)、薄片鉴定、氩离子抛光扫描电镜等手段,深入分析并探讨了页岩裂缝的发育特征及其对页岩气成藏和开发的影响.结果表明:阳春沟构造带五峰组-龙马溪组页岩发育大量裂缝,宏观裂缝以构造缝为主,包括高角度剪切缝、低角度滑脱缝,非构造缝主要为层理缝和层间缝;微裂缝主要为层间缝、粒间缝、粒内缝.天然裂缝的发育对页岩气成藏和开发有着重要的控制作用.首先影响页岩气的储集与保存.天然裂缝能够增加页岩的储集空间,但大型天然开启裂缝可能破坏上覆层的封闭性,造成天然气散失,不利于页岩气成藏.其次影响后期人工体积改造的效果.被方解石充填的裂缝网络有利于水力压裂;但大型天然开启裂缝的发育会导致钻井液大量漏失,同时也不利于后期压裂改造形成复杂缝网.

Development Characteristics of Shale Fractures and Their Influence on Production Capacity in Yangchungou Area

Based on core observation, FMI, thin section, and SEM observation of shale in the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation of the Yangchungou structural belt in southeastern Chongqing area, the development characteristics of shale fractures and their influence on shale gas reservoir formation and development were deeply analyzed and discussed. The results indicate that a large number of fractures are developed in the shale of Wufeng Formation -Longmaxi Formation. The macro fractures are dominated by structural fractures, including high dip-angle shearing fracture and low dip-angle slip fracture. The non-structural genesis fractures are mainly bedding and interlayer fractures. The micro fractures mainly include interlayer, inter-particle, and intra-particle fractures. The development of natural fractures has an important control effect on shale gas accumulation and development. First, it affects the storage and preservation of shale gas. The natural fractures can increase the storage space for shale gas. But the open fractures may destroy the sealing of the overlying layers, causing shale gas to escape, which is not conducive to shale gas accumulation. Secondly, it affects the later volume fracturing. The fracture network filled with calcite is conducive to hydraulic fracturing. In contrast, the open fractures not only can cause severe drilling mud leakage, but also deter the formation of complex fracture networks through fracturing.