五宝场地区须家河组成藏主要控制因素

Main controlling factors of gas accumulation in Xujiahe Formation,Wubaochang area,Sichuan Basin

四川盆地陆相致密气的勘探开发主要集中在川中和川西地区,川东北地区陆相致密气藏的勘探工作起步较晚,勘探程度较低,2019年对Wbq15井上三叠统须家河组老井测试获气20.47×10^(4)m^(3)/d,从而揭开了川东北须家河组气藏的勘探序幕。通过近期的研究发现,五宝场地区须家河组主要沉积相为三角洲沉积,有利的沉积微相为水下分流河道和分流间湾沉积,砂体纵向叠置发育、横向变化较大,储层为特低孔、特低渗的致密砂岩,非均质性较强。受燕山—喜马拉雅期的构造挤压作用,区域内断裂、裂缝较发育,可以有效沟通烃源和改善储渗条件。勘探实践证实,须家河组气藏主要受岩性控制,整体含气性较好,是致密气的重点勘探领域,具备较大的勘探潜力。通过气藏成藏研究认为,五宝场地区须家河组气藏具有“双源供烃、两期成藏”模式,气藏成藏的主要控制因素有:(1)有利的沉积微相组合;(2)烃源断裂;(3)裂缝发育;(4)保存条件好。

In Sichuan Basin,the exploration and development for continental tight gas are concentrated in the central and western parts,whereas the exploration for the northeastern area started late and is at a relatively low level.In 2019,the tested gas yield of 20.47×10^(4)m^(3)/d was obtained from Well Wbq15 of the Upper Triassic Xujiahe Formation in the northeastern area,thus kicking off the gas reservoir exploration for the Formation.Recent research indicates that the main sedimentary facies of the Formation in Wubaochang area is delta deposit.The favorable sedimentary microfacies are underwater distributary channels and interdistributary bay deposits.The developed sand bodies are overlapped vertically and change greatly in horizontal direction.The reservoir is the tight sandstone with extremely low porosity and permeability,and strong heterogeneity.Due to the tectonic compression in the Yanshanian-Himalayan period,faults and fractures are well-developed in this area,which can effectively connect hydrocarbon sources and improve reservoir and permeability.Exploration practice shows that,controlled mainly by lithology,the reservoir has great potential for tight gas exploration with good gas content as a whole.The study of gas accumulation reveals that the reservoir has the mode of“double-source supply,two-stage accumulation”.The main factors controlling accumulation include:(1)favorable sedimentary microfacies assemblage,(2)hydrocarbon source faults,(3)developed fractures,and(4)good preservation conditions.