昭通示范区五峰组-龙马溪组页岩气成藏类型与有利区分布

Shale gas accumulation types and favorable area distribution of Wufeng Formation-Longmaxi Formation in Zhaotong Demonstration Area

依据昭通示范区五峰组—龙马溪组页岩沉积背景与环境、构造改造历程、储层充填特征与记录等,结合页岩成烃演化史,明确页岩气有利区分布主要受沉积期岩相、改造期变形强度及保存期封闭性能3个因素控制,按照现今页岩气保存单元将示范区页岩气藏划分为背斜、向斜与斜坡3种类型。背斜型(太阳、海坝等)以富集原油裂解气为主,主控因素为后期改造强度与保存单元封闭性能,有利区以孤立、继承性背斜为主;向斜型(罗场—建武、罗布等)以富集干酪根热降解气为主,主控因素为沉积相带及保存单元封闭性能,有利区以继承性宽缓复向斜为主,多连片分布;斜坡型(罗场—建武复向斜南翼黄金坝—紫金坝及太阳—海坝背斜之间云山坝过渡区等)以富集混源气(原油裂解气与干酪根热降解气)为特征,有利区多沿背斜、向斜之间的翼部过渡区分布。

Based on the shale depositional background and environment,structural reformation process,reservoir filling characteristics and records of Wufeng Formation-Longmaxi Formation in Zhaotong Demonstration Area,combined with the analysis of shale hydrocarbon generation history,it is clear that the distribution of shale gas favorable area in the demonstration area is mainly controlled by three factors:sedimentary facies,deformation strength during the reformation period and sealing performance during the preservation period.According to the current shale gas preservation unit,shale gas reservoirs in the demonstration area are divided into three types:anticline,syncline and slope.The anticline type(Taiyang,Haiba,etc.)is mainly enriched in crude oil-cracked gas,and the main controlling factors are the strength of later transformation and the sealing performance of the preservation unit,and the favorable areas are mainly isolated and inherited anticlines.The syncline type(Luochang-Jianwu,Luobu,etc.)is mainly enriched with kerogen pyrolysis gas,and the main controlling factors are sedimentary facies and the sealing performance of preservation units,and the favorable areas are mainly wide and gentle inherited synclines,most of which are continuously distributed.The slope type(Huangjinba-Zijinba zone of the south wing of Luochang-Jianwu compound syncline and Yunshanba transition area between Taiyang and Haiba anticline,etc.)is characterized by enrichment of mixed source gas(crude oil-cracked gas and kerogen pyrolysis gas),and the favorable areas are mostly distributed along the wing transitional zone between anticline and syncline.