临兴地区海陆过渡相页岩及页岩气地球化学特征  

Geochemical characteristics of marine-continental transitional facies shale and shale gas in Linxing area

作　　者：陈鑫 吴鹏[3] 高计县[3] 胡维强[1,2] 丁万贵 李洋冰 柳雪青 马立涛[1,2] 刘成 孔为 曹地[1,2] 陈建奇 李勇[4] CHEN Xin;WU Peng;GAO Jixian;HU Weiqiang;DING Wangui;LI Yangbing;LIU Xueqing;MA Litao;LIU Cheng;KONG Wei;CAO Di;CHEN Jianqi;LI Yong(CNOOC Energy Technology-Drilling&Production Co.,Tianjin 300452,China;CNOOC Energy Technology&Services Limited Key Laboratory for Exploration&Development of Unconventional Resources,Tianjin 300452,China;China United Coalbed Methane Corporation Ltd.,Beijing 100011,China;School of Geoscience and Surveying,China University of Mining and Technology(Beijing),Beijing 100083,China)

机构地区：[1]中海油能源发展股份有限公司工程技术分公司,天津300452 [2]中海油能源发展股份有限公司非常规勘探开发重点实验室,天津300452 [3]中联煤层气有限责任公司,北京100011 [4]中国矿业大学(北京)地球科学与测绘工程学院,北京100083

出　　处：《煤田地质与勘探》2021年第6期12-23,共12页Coal Geology & Exploration

基　　金：国家自然科学基金项目(42072194);国家科技重大专项项目(2016ZX05066)。

摘　　要：为揭示鄂尔多斯盆地东缘上古生界海陆过渡相页岩及页岩气地球化学特征,选取临兴地区页岩样,开展薄片鉴定、全岩和黏土含量、扫描电镜、有机碳、岩石热解、干酪根显微组分和干酪根碳同位素测试,分析页岩解吸气的气体组分和碳同位素组成。结果表明:临兴地区过渡相页岩矿物组分主要是石英和黏土矿物,含少量方解石、斜长石、钾长石、白云石和黄铁矿等。受矿物成因、沉积环境等多方面的影响,不同矿物组分与有机质赋存方式各异。石英与有机质存在2种赋存方式,黏土矿物存在3种赋存方式,黄铁矿存在4种赋存方式。有机质类型为Ⅱ_(2)–Ⅲ型,有机碳含量平均值大于2.0%,干酪根碳同位素介于–24.5‰~–23.2‰。镜质体反射率介于0.92%~1.30%,t_(max)值介于427~494℃,有机质热演化达到成熟阶段。页岩气中烃类气以甲烷为主,含有少量乙烷、丙烷,总体属于干气。甲烷碳同位素均值为–40.0‰,介于海相页岩气和陆相页岩气甲烷碳同位素之间;乙烷碳同位素值介于–26.8‰~–22.56‰,均大于–29‰,整体呈现出δ^(13)C_(1)<δ^(13)C_(2)<δ^(13)C_(3)正碳序列。研究认为,该区页岩具备大量生成页岩气的潜力,页岩气主要来源于上古生界偏腐殖型页岩,属于由干酪根裂解而生成的有机热成因煤成气。In order to reveal the geochemical characteristics of shale and shale gas on the east edge of Ordos Basin,thin section identification, full rock and clay content, scanning electron microscope, organic carbon, rock pyrolysis,kerogen macerals, and kerogen carbon isotopes were tested, and the gas component and carbon isotopes composition of shale were analyzed. The results show that the mineral component of the transitional facies shale in Linxing area is mainly quartz and clay minerals, containing a small amount of calcite, plagioclase, potassium feldspar,dolomite and pyrite. Affected by the mineral genesis and deposition environment, different mineral components and organic matter occur in different ways. There are two deposit patterns of quartz and organic matter, 3 patterns of clay minerals, and 4 patterns of pyrite. The organic matter type is Ⅱ_(2)-Ⅲ type, the average organic carbon content is greater than 2.0%, and the kerogen carbon isotopes are from –24.5‰ to –23.2‰. The vitrinite reflectivity is from 0.92% to 1.30%, t_(max) is 427~494℃, and the thermal evolution of organic matter reaches maturity. In shale gas, hydrocarbon gas is mainly methane, containing a small amount of ethane and propane, which is generally dry gas. The mean methane carbon isotope is –40.0‰, between marine shale gas and terrestrial shale gas, ethane carbon isotopes from –26.8‰ to –22.56‰, both more than –29 ‰, showing δ^(13)C_(1)<δ^(13)C_(2)<δ^(13)C_(3) positive carbon sequence. It is believed that the shale in the area has the potential to generate shale gas. The shale gas is mainly derived from humic shale in the upper Paleozoic boundary, which belongs to the organic thermal coal gas generated by the cracking of cheese root.

关 键 词：鄂尔多斯盆地东缘 海陆过渡相 页岩气 地球化学 成因类型 

分 类 号：TP028.8[自动化与计算机技术]