淮南潘谢矿区石盒子组煤系页岩气储层孔隙结构特征及影响因素

Pore Structure Characteristics and Its Influencing Factors of Coal-bearing Shale Gas Reservoir of Shihezi Formation in Panxie Mining Area,Huainan

淮南潘谢矿区发育了丰富的煤系页岩储层。为探讨页岩储层孔隙结构对于页岩气富集和开采的影响,应用高压压汞、低温N 2和CO 2吸附实验结果,对淮南潘谢矿区石盒子组煤系页岩气储层的孔隙结构进行定量表征,并结合有机地球化学特征、矿物组成和成熟度探讨了其影响因素。结果表明:潘谢矿区石盒子组页岩孔隙度为1.21%~11.00%,平均3.58%;孔隙类型主要为平行板状孔、楔状半封闭孔及墨水瓶孔。潘谢矿区石盒子组页岩的总孔体积为12.77×10^-3~36.66×10^-3 cm^3/g,总比表面积为10.27~26.01 m^2/g,平均孔径为9.59 nm,介孔对孔隙结构的贡献最大,其次是微孔和宏孔。孔径为0.5~0.85、2.1~3.5、71~150 nm的孔隙对潘谢矿区石盒子组页岩孔体积起主导作用,孔径为0.4~0.85、2.5~5.0 nm的孔隙提供了主要的比表面积。总有机碳含量(TOC)、矿物组分和成熟度均会影响石盒子组页岩孔隙结构的发育。TOC的富集有利于拓展孔隙空间和孔隙结构的发育;黏土矿物含量的增加会抑制孔隙结构的发育,脆性矿物则相反;石盒子组页岩成熟度达成熟-高成熟,处于有机质第一次裂解后孔隙减小阶段。该研究成果为深入认识该区页岩气赋存富集提供基础资料。

There are abundant coal series shale reservoirs in Panxie mining area,Huainan.In order to explore the influence of pore structure of shale reservoir on shale gas enrichment and exploitation,the pore structure of coal bearing shale gas reservoir in Shihezi Formation of Panxie mining area in Huainan is quantitatively characterized by using high pressure mercury injection,N 2 and CO 2 adsorption at low temperature,and the influencing factors are discussed in combination with organic geochemical characteristics,mineral composition and maturity.The results show that the porosity of Shihezi Formation in Panxie mining area is 1.21%~11.00%in range,and the average is 3.58%.And the shale pore types of shale samples are mainly parallel plate-like pore,wedge-shaped semi-closed pore and ink-bottle pore.The total pore volume of the Shihezi Formation shale in Panxie mining area is 12.77×10^-3~36.66×10^-3cm^3/g,total specific surface area is 10.27~26.01 m^2/g in range,and average pore size is 9.59 nm.The mesopore contributes most to the pore structure,followed by the micropore and the macropore.These pores whose pore sizes are 0.5~0.85 nm,2.1~3.5 nm and 71~150 nm in range play a dominant role in the pore volume of Shihezi Formation shale in Panxie mining area,and pores with pore sizes of 0.4~0.85 nm and 2.5~5.0 nm in range account for the main specific surface area.The total organic carbon content(TOC),mineral composition and maturity of shale all have an important influence on the development of the pore structure of Shihezi Formation shale.The enrichment of TOC is conducive to the development of pore space and pore structure.The increase of clay mineral content can inhibit the development of pore structure,while brittle minerals are on the contrary.The maturity of Shihezi Formation shale reaches maturity-high maturity,which is in the stage of pore space reduction after the first cracking of organic matter.The research results provide basic data for further understanding the occurrence and enrichment of shale gas in this area.