川东红星地区吴家坪组与焦石坝地区龙马溪组页岩储层差异性分析及意义

Analysis and significance of shale reservoir differences between Wujiaping Formation in Hongxing area and Longmaxi Formation in Jiaoshiba area,eastern Sichuan Basin

四川盆地东部红星地区二叠系吴家坪组发育一套黑色富硅富碳页岩储层,目前已成为该地区页岩气领域重要的增储上产阵地。该套页岩储层与焦石坝地区龙马溪组含气页岩段下部①—③小层在沉积环境、页岩品质及含气性等方面具有较好的相似性,主要表现在二者均具备富碳、富硅、高含气的特点,但在后期开发过程中,吴家坪组页岩气层开发效果明显差于焦石坝地区龙马溪组页岩气层。为此,分析了2套页岩储层品质、含气性等方面差异性特征及其主要控制因素。吴家坪组页岩储层矿物组成具有硅质矿物含量低、碳酸盐矿物含量高的特征,有机碳含量高但成烃母质和有机质类型较差;孔隙结构表现为有机质孔隙和层理缝发育程度较低以及孔隙尺度偏小的特征,储层物性及含气性较焦石坝地区龙马溪组页岩储层略差。对比分析认为,沉积背景和沉积作用的差异导致2套页岩储层在岩矿、层理、成烃母质类型等原生品质上存在差异,这是2套储层在物性和含气性方面存在差异的物质基础;后续的构造保存条件等宏观地质条件的差异,导致2套储层在孔隙类型、孔隙尺度、孔隙度及含气性等方面存在较明显的差异。此外,探讨了2套储层差异性特征对其开发效果的影响,并针对2套页岩储层的差异性提出了相应的开发工程工艺技术对策。

In the Hongxing area of the eastern Sichuan Basin,the Permian Wujiaping Formation developed a set of black,silicon⁃rich,and carbon⁃rich shale reservoirs,which are currently pivotal for enhancing shale gas reserves and production in the region.These shale reservoirs show strong similarities with the lower sections(layers①to③)of the gas⁃bearing shale in the Longmaxi Formation of the Jiaoshiba area in terms of sedimentary environ⁃ment,shale quality,and gas content.Both formations are characterized by high carbon,silicon,and gas contents.However,in later stages of development,the shale gas reservoirs of the Wujiaping Formation were significantly less productive compared to those in the Longmaxi Formation in the Jiaoshiba area.To address this,the study analyzes the differences in reservoir quality and gas content between the two shale sets and their primary controlling factors.The results reveal that the shale reservoir in the Wujiaping Formation is characterized by a low silica mineral content and a high carbonate mineral content.Although it has a high organic carbon content,the kerogen types and organic matter are relatively poorer.The pore structure is marked by less developed organic matter pores and lamellar fractures,with smaller pore sizes.Overall,its reservoir physical properties and gas content are slightly inferior to those of the Longmaxi Formation shale in the Jiaoshiba area.Comparative analysis suggests that differ⁃ences in sedimentary backgrounds and processes lead to primary quality differences in mineral and lithological composition,lamellation,and kerogen types between the two shale reservoirs.These differences form the material basis for variations in physical properties and gas content.Furthermore,differences in subsequent structural preserva⁃tion conditions and other macro⁃geological factors lead to significant disparities between the two reservoirs in terms of pore types,sizes,porosity,and gas content.In addition,the study explores the impact of these distinctive characte⁃ristics on the development effectiveness of the two reservoirs and proposes corresponding engineering and techno⁃logical strategies tailored to the differences in the development of these reservoirs.