湖北荆门探区五峰组—龙马溪组深层页岩微观孔隙结构与分形特征  

Micro-pore structure and fractal characteristics of deep shale from Wufeng Formation to Longmaxi Formation in Jingmen exploration area,Hubei Province

作　　者：李小明[1] 王亚蓉 吝文[2] 马丽红[1] 刘德勋[2] 柳吉荣 张宇 LI Xiaoming;WANG Yarong;LIN Wen;MA Lihong;LIU Dexun;LIU Jirong;ZHANG Yu(College of Safety Engineering,North China Institute of Science and Technology,Beijing 101601,China;Department of Shale Gas,Research Institute of Petroleum Exploration and Development,PetroChina,Beijing 100083,China)

机构地区：[1]华北科技学院安全工程学院,北京101601 [2]中国石油勘探开发研究院页岩气研究所,北京100083

出　　处：《天然气地球科学》2022年第4期629-641,共13页Natural Gas Geoscience

基　　金：国家科技重大专项(编号:2017ZX05035);中国石油天然气有限公司重点项目(编号:2017B49,2019F-31);中央高校基本科研业务费项目(编号:3142014025)联合资助。

摘　　要：为探究湖北荆门探区页岩储层孔隙结构及分形特征,定量评价孔隙的非均质性和复杂程度,以YT3井五峰组—龙马溪组为研究对象,通过低压氮气吸附实验,并结合有机碳含量测试、X射线衍射分析等,分析了储层孔隙结构特征,基于低温氮吸附分形几何学方法建立了FHH分形模型,讨论了分形维数与页岩组成、孔隙结构、物性、含气性及埋深等参数的相关关系。结果表明:①龙马溪组下段和五峰组有机碳(TOC)含量明显高于龙马溪组上段,且随着埋藏深度的增加,显示出硅酸盐矿物逐渐增加,而黏土矿物减小的趋势;②页岩现场解吸含气量显示,有机质丰度较低的龙马溪组上段含气量较有机质丰度较高的龙马溪组下段和五峰组低,在页岩气组成上,龙马溪组上段以氮气为主,而五峰组和龙马溪组下段则以甲烷为主;③页岩低压氮气等温曲线与IUPAC分类的Ⅳ型接近,吸附回滞环近似H3、H4型,为平板状和狭缝型孔隙,孔隙主要为分布于50 nm以下微—中孔,龙马溪组下段和五峰组吸附体积明显大于龙马溪组上段,是由于高有机质丰度提供了大量的有机孔储集空间所致;④高有机质的龙马溪组下段和五峰组较低有机质的龙马溪组上段,其BET比表面积、BJH总孔体积显著增大,而平均孔径却明显减小;⑤页岩孔隙具有明显的分形特征,分形维数D2均大于D1,表明孔隙结构复杂程度大于孔隙表面,分形维数与有机碳(TOC)含量、BET比表面积、埋深呈显著的正相关关系,与石英含量、BJH总孔体积呈弱的正相关关系,与黏土矿物含量和平均孔径呈显著的负相关关系,而与孔隙度和渗透率基本无相关性。影响分形维数的因素很多,相关性分析揭示了有机碳和黏土矿物质量分数、比表面积、平均孔径及埋深为其主控因素。通过分形维数可定量评价孔隙结构的复杂程度和不均一性,为研究页岩孔隙结构的分布特�In order to explore the pore structure and fractal characteristics of shale reservoirs in the Jingmen exploration area and quantitatively evaluate the heterogeneity and complexity of pores,taking Wufeng-Longmaxi formations of Well YT3 as the research object,the pore structure characteristics of shale reservoir are analyzed by low-pressure nitrogen adsorption experiments,organic carbon content testing,X-ray diffraction analysis,etc.and the FHH fractal model is established based on the low temperature nitrogen adsorption fractal geometry method.The relationship between fractal dimension and shale composition,pore structure,physical property,gas-bearing property and burial depth is discussed.The results show that:(1)The organic carbon(TOC)content of the lower Longmaxi Formation and Wufeng Formation is significantly higher than that of the upper Longmaxi Formation.With the increase of burial depth,the silicate minerals increase gradually,while clay minerals decrease;(2)The on-site desorption gas content of shale shows that the gas content of the upper section of Longmaxi Formation with low organic matter abundance is lower than that of the lower section of Longmaxi Formation and Wufeng Formation.In terms of shale gas composition,the upper section of Longmaxi Formation is dominated by nitrogen,while the lower sections of Wufeng Formation and Longmaxi Formation are dominated by methane;(3)The isothermal curve of shale under low-pressure nitrogen is close to type IV classified by IUPAC,and the adsorption hysteresis loop is similar to types H3 and H4.It is flat and slit pores,and the pores are mainly micro medium pores distributed below 50 nm.The adsorption volume of the lower Longmaxi Formation and Wufeng Formation is significantly larger than that of the upper Longmaxi Formation,and the high abundance of organic matter provides a large amount of organic pore storage space;(4)The BET specific surface area and BJH total pore volume in the lower Longmaxi Formation and Wufeng Formation with high organic matter are signific

关 键 词：荆门探区 页岩储层 孔隙结构 氮气吸附法 分形特征 

分 类 号：TE122[石油与天然气工程—油气勘探]