陆相页岩碳酸盐矿物成因及其页岩气富集作用——以松辽盆地梨树断陷沙河子组页岩为例  

Genesis of carbonate minerals in continental shale and their roles in shale gas enrichment:A case study of the shale of Shahezi formation in Lishu fault depression,Songliao Basin,NE China

作　　者：白静 徐兴友[1,3] 张君峰 陈珊[1,3] 刘卫彬 刘畅 李耀华[1,3] BAI Jing;XU Xingyou;ZHANG Junfeng;CHEN Shan;LIU Weibin;LIU Chang;LI Yaohua(Oil and Gas Survey,China Geological Survey,Bejing 100083,China;PetroChina Research Institute of Petroleum Exploration and Development,Beijing 100083,China;Key Laboratory of Unconventional Oil and Gas,China Geological Survey,Beiing 100083,China)

机构地区：[1]中国地质调查局油气资源调查中心,北京100083 [2]中国石油勘探开发研究院,北京100083 [3]中国地质调查局非常规油气重点实验室,北京100083

出　　处：《中国矿业大学学报》2022年第4期742-756,共15页Journal of China University of Mining & Technology

基　　金：中国地质调查局地质调查项目(DD20190115)。

摘　　要：为了揭示陆相页岩中碳酸盐矿物对页岩气的富集作用及意义,本文以松辽盆地梨树断陷下白垩统沙河子组富含碳酸盐矿物的页岩为研究对象,通过高精度厘米级岩心观察、薄片鉴定、X射线衍射全岩矿物分析、XRF元素测试、扫描电镜等手段,分析了页岩中碳酸盐矿物的发育特征,探讨了碳酸盐矿物的形成环境及成因作用,认为碳酸盐矿物对陆相页岩气甜点分布具有重要的指示意义和控制作用.研究结果表明:梨树断陷下白垩统沙河子组发育一套富含碳酸盐矿物(质量分数平均值为15.0%,最高值为48.5%)、富有机质(TOC>2%)且高含气(单井页岩气产量达到7.6×10~4 m~3/d)的陆相页岩,页岩中碳酸盐矿物主要以纹层形式存在,可分为生物碎屑纹层、泥晶方解石纹层和亮晶方解石纹层3种类型.沙河子组富含碳酸盐矿物的页岩主要形成于半深湖—深湖相咸化分层还原的水体环境,不同类型的碳酸盐纹层形成作用具有差异.生物碎屑型碳酸盐是沉积湖底的生物壳体在成岩初期经方解石化作用形成的,纹层状生物碎屑型碳酸盐主要形成于深水稳定咸化还原的水体环境;泥晶方解石纹层是受藻类等生物光合作用诱导结晶形成,主要形成于封闭咸化高生产力强还原的环境,与有机质纹层形成季节性纹层特征;亮晶方解石纹层为原生方解石经有机酸溶蚀后重结晶而成.陆相页岩中碳酸盐富集指示利于原生有机质发育的沉积环境,即指示具有良好生气基础的优质页岩发育段;与方解石相关的溶蚀孔、微裂缝等储集空间发育,为页岩气富集提供了必要条件,碳酸盐矿物含量决定了页岩中孔隙的发育程度,碳酸盐矿物质量分数大于10%的页岩孔隙度一般大于4%.In order to reveal the important role of carbonate minerals on shale gas enrichment, taking the carbonate rich shale of Shahezi formation as the research object, by high-precision centimeter core observation, thin section identification, X-ray diffraction whole rock mineral analysis, XRF element test and scanning electron microscoe, this paper analyzed the developmental characteristics of carbonate minerals in shale, and discussed the genetic environment and genetic function of carbonate minerals. We find that carbonate minerals play an important role in controlling the distribution of continental shale gas. The results show that a set of shale rich in carbonate minerals(the average value of mass fraction is 15.0%, and the maximum value is 48.5%), organic matter(TOC>2%) and gas(shale gas production 7.6×10~4 m~3/d)is developed in Shahezi formation of Lower Cretaceous in Lishu fault depression, Songliao Basin. Carbonate minerals in the shale of Shahezi formation in Lishu fault depression mainly exist in laminated form, which can be divided into 3 types: bioclastic lamina, argillaceous calcite lamina and bright calcite lamina. Carbonate minerals in the shale of Shahezi formation are mainly formed in the salinization and layered reduction water. Different types of carbonate mineral laminar have diverse genesis. Bioclastic carbonate is mainly formed by the calcification of biological shells in the early diagenetic stage, and the bioclastic carbonate lamina formed in the deep water environment of salinization and reduction. Argillaceous calcite lamina is formed by crystallization induced by photosynthesis of algae and other organisms and forms seasonal lamina with organic matter lamina. Bright calcite laminae is the product of recrystallization of primary calcite after dissolution by organic acid. The enrichment of carbonate in continental shale indicates the sedimentary environment conducive to the development of primary organic matter, that is, the high-quality shale with a good gas generation foundation development

关 键 词：陆相页岩气 富集 碳酸盐矿物 成因类型 沙河子组 梨树断陷 松辽盆地 

分 类 号：TE121[石油与天然气工程—油气勘探]