泸州-渝西区块海相页岩可压性演化差异  

Evolution difference of fracability of marine shale gas reservoir in Luzhou and west Chongqing block,Sichuan Basin

作　　者：沈骋 谢军[2] 赵金洲[3] 范宇 宋毅 SHEN Cheng;XIE Jun;ZHAO Jinzhou;FAN Yu;SONG Yi(Shale Gas Research Institute,PetroChina Southwest Oil&Gas field Company,Chengdu,Sichuan 610051,China;PetroChina Southwest Oil&Gas field Company,Chengdu,Sichuan 610051,China;State Key Laboratory of Oil and Gas Reservoir Geology and Exploration,Southwest Petroleum University,Chengdu,Sichuan 610500,China)

机构地区：[1]中石油西南油气田分公司页岩气研究院,四川成都610051 [2]中石油西南油气田分公司,四川成都610051 [3]西南石油大学油气藏地质及开发工程国家重点实验室,四川成都610500

出　　处：《中国矿业大学学报》2020年第4期742-754,共13页Journal of China University of Mining & Technology

基　　金：国家科技重大专项(2016ZX05062);中国石油天然气股份有限公司重大科技专项(2016E-06)。

摘　　要：为加深现有可压性评价在机理上的认识,以川南泸州-渝西区块奥陶系五峰组、志留系龙马溪组海相页岩气储层为例,采用氩离子抛光扫描电镜、X射线衍射和元素俘获能谱测井等手段,获取区内储层基本地质特征.通过镜下观察、数理统计与计算,利用矿物组分、储集物性、主量元素和岩石力学参数等,总结了海相页岩可压性演化机制,认为海相页岩在沉积成岩过程中受到了海水环境、矿物演化和微观孔隙组构的综合影响,对储层的可压性产生不同程度的促进和制约作用.研究结果表明:局限环境易促进生物成因硅质矿物大量发育,降低层间叠置频率,成岩后经胶结、黏土转化作用,增大矿物粒径,缩小层间差异,降低天然弱面发育,并且大量发育的孔隙和有机质对力学性质会产生负面影响;连通环境易促进生物成因硅质、陆源碎屑硅质和碳酸盐矿物混合发育,纵向上岩性差异化高频叠置,天然弱面发育,成岩后易在压实、压溶作用下发生矿物粒径减小、孔隙规模降低的现象,促使储层维持较高的可压性.渝西区块龙一■、泸州区块龙一■是沉积于滞留与连通环境交替期的页岩,经成岩作用改造后同时具有沉积成岩促进作用的优势,可压性卓越,储集物性较好,是高弹性模量(>45 GPa)、低泊松比(<0.25),较好物性参数(孔隙度>5%、TOC>4%)的储层,是改造甜点.生产实践表明,泸州-渝西区块改造甜点自北向南呈现"早时"的空间过渡关系,对其实现高钻遇率有利于后续深层页岩气储层优钻优压和规模效益开发.To deepen the understanding of fracability evaluation mechanism, samples from Ordovician Wufeng formation and Silurian Longmaxi formation in Luzhou and west Chongqing block were used to study the geological features by methods of argon ion polishing scanning electron microscope, X-ray diffraction and elemental capture spectrum log. The fracability evolution mechanism of marine shale gas reservoir was summarized based on mineral components, reservoir properties, major elements, rock mechanical parameters, which are observed by using microscopic examination, mathematical statistics and calculation. It indicated that the fracability can be enhanced or confined in different degrees by sea environment, mineral forming and transforming, micro-pore structures in whole deposition and diagenesis processes. The results showed that the restricted environment can promote the development of bio-silicon and decrease the frequency of superposed layers, then increase the mineral size, decrease the diversity of lamination and the development of natural weak planes after diagenesis by cementation and clay transformation, and has a negative influence on the elastic mechanics properties because of the development of pore and organic matter. The connected environment can promote the development of mixed brittle minerals such as bio-silicon, terrestrial-silicon, carbonate, and increase the lamination diversity and natural weak planes, then decrease the mineral size and pores by compaction and pressure solution to maintain the higher fracability. The further research showed that Layer L1■ in west Chongqing block and Layer L1■in Luzhou block, which formed in the restrict-to-connect alternant period, have the advantages of all deposition and diagenesis. These layers, as the fracturing sweet spot, also have the best rock mechanical and the better reservoir properties such as high elastic modulus(>45 GPa),lower Possion’s ratio(<0.25), better porosity(>5%) and total organic content(>4%). The result of field practice showed that the fr

关 键 词：可压性演化 页岩气储层 沉积环境 脆性矿物 孔隙 泸州—渝西区块 

分 类 号：P618.12[天文地球—矿床学]