南方海相深层页岩气储集空间差异化发育及保持机理探讨

Differential development and maintenance mechanism of reservoir space for marine shale gas in South China’s deep strata

我国南方海相深层(主体埋深大于3500 m)页岩气具备良好的地质条件,资源潜力巨大,但由于埋深大,研究程度低,不同位置的水平井之间产能差异比较明显,勘探开发面临诸多挑战。在调研国内外深层页岩气现状及发展动态的基础上,重点梳理我国南方海相深层页岩气储集空间差异化发育、石英等刚性矿物抗压保孔和储层流体超压保孔等研究进展和存在问题。就川东南上奥陶统五峰组—下志留统龙马溪组深层页岩气而言,储集空间差异化发育及其是否有效保持是控制含气量、产能和单井EUR的主要原因之一,但差异化发育特征及保持机理并不明确,储层近深层原位条件下的差异化响应过程及机理仍需要深入研究;石英等刚性矿物在抗压保孔过程中具有重要的作用,但关于“石英抗压保孔”对不同储集空间类型的差异化作用仍不十分明确;“储层流体超压”作用对于深层页岩气储集空间保持具有重要的意义,但对“储层流体超压”究竟如何作用于深层页岩储集空间了解甚微。解决上述问题的关键在于研究典型富有机质页岩处于近深层原位状态下(多重应力加载和高温)不同类型储集空间类型差异化发育、响应及保持特征和作用机理。

The deep marine strata with burial depth greater than 3500 m in South China have good geological conditions and huge potential for shale gas resource.However,due to the burial depth and relative poor under⁃standing,the productive difference between horizontal wells in different positions is obvious,and exploration and development are still challenging.On the basis of investigating the current situation and development trends of global deep shale gas,this paper focuses on the differential development of reservoir of marine deep shale gas in South China,the pore preservation by pressure resistance of rigid minerals such as quartz,and the pore preserva⁃tion of reservoir fluid overpressure.The differential development of reservoir space and effectiveness is one of the main factors for the controlling of gas content,productivity and EUR per well of deep shale gas of the Wufeng-Longmaxi formations in the southeastern part of Sichuan Basin,but the characteristics of differential development and maintenance mechanism is unclear,and the differentiated response process under in⁃situ conditions of near⁃deep reservoirs and the mechanism still need to be studied.Although it is recognized that rigid minerals such as quartz play an important role for the pressure resistance and pore preservation,its varied effect on different types of storage spaces is still unclear.It has been shown that the effect of reservoir fluid overpressure is of great signifi⁃cance to the preservation of deep shale gas storage space,it is still limited understanding of how reservoir fluid overpressure affects deep shale reservoir space.The key factor to answer the problems above is to study the characteristics and mechanism of differential development,response and maintenance of different types of reservoir space in a typical organic⁃rich shale in a near⁃deep in⁃situ state with multiple stress loading and high temperature.