古生界干酪根热演化模拟实验  

Experimental study on thermal evolution of kerogen in Paleozoic

作　　者：康广星 徐学敏[1] 汪双清[1] 杨佳佳[1] 孙玮琳[1] 沈斌 秦婧[1] 芦苒[1] 张小涛 郭望[3] Kang Guang-xing;Xu Xue-min;Wang Shuang-qing;Yang Jia-jia;Sun Wei-lin;Shen Bin;Qin Jing;Lu Ran;Zhang Xiao-tao;Guo Wang(National Research Center for Geoanalysis,Beijing 100037,China;China University of Geosciences,Beijing 100083,China;Xi'an Center of Geological Survey China Geological Survey,Xi'an 710054,,China)

机构地区：[1]国家地质实验测试中心,北京100037 [2]中国地质大学,北京100083 [3]中国地质调查局西安地质调查中心,陕西西安710054

出　　处：《天然气地球科学》2019年第4期593-602,共10页Natural Gas Geoscience

基　　金：国家自然科学基金(编号:41702159;41602162);国家科技重大专项(编号:2016ZX05034-003);国家地质调查项目(编号:DD20160184;DD20160220)联合资助

摘　　要：我国南方下古生界页岩中有着丰富的页岩气资源,但因其时代老,成熟度高,且缺乏镜质体,其有机质热演化程度评价成为一个技术难题,对相关页岩气地质研究造成困扰。已有研究表明,干酪根H/C原子比和O/C原子比会随着有机质热演化程度的增加呈现规律性变化,但是对于缺乏镜质体的下古生界干酪根,以及高过成熟阶段干酪根却鲜有研究,其元素演化规律如何?其元素组成与镜质体反射率之间是否存在明确的定量关系?值得研究。为此,针对二叠系大隆组的泥岩和蓟县系洪水庄组页岩,在350～550℃温度范围内开展了系列干酪根热演化模拟实验,测定了各模拟实验温度下所得干酪根的镜质体反射率(R_O)和C、H、O元素组成,发现干酪根H/C原子比和O/C原子比与有机质成熟度之间具有高度的统计学相关关系。结果显示:①在开展烃源岩演化热模拟实验时,对于在泥盆纪以前沉积缺乏镜质体的烃源岩样品而言,利用与烃源岩样品镜质体反射率R_O值相近的煤样来标定样品热演化进程的方法是可行的;②在热演化进程中,干酪根的H/C、O/C原子比值均会随着有机质成熟度的增加发生规律性的变化,不同类型干酪根的H/C原子比值表现出沿相同路径不断降低的演化特征,而O/C原子比值表现出沿不同路径不断降低但最终趋同的演化特征;③实验中涉及的3种类型干酪根的H/C、O/C原子比(R_(H/C)和R_(O/C))与用镜质体反射率R_O(%)所表征的有机质热演化程度之间均体现同一规律,并存在良好的数学相关关系,可以表达为LgR_O=-0.133 1-1.190 5 LgR_(H/C)-0.054 4LgR_(O/C),适用于该实验中涉及的3种类型干酪根,适用RO值范围为0.6%～3.5%。Shale gas resources are abundant in the Lower Paleozoic shales in southern China, which are of very old age,high maturity and are lack of vitrinite,and thus lead to a technical problem for evaluating the thermal evolution degree of organic matter in them .Previous studies have shown that the H/C and O/C atomic ratios of kerogen decrease regularly with the increase of its maturity, but there is little research on high maturity stage kerogens,or kerogens lack of virinite, therefore, it remains unclear that how their element evolves and does the evolution of element composition quantitatively reflect to Ro value? These are worthy of study.For this purpose,a series of simulation experiments of thermal evolution of kerogen have been carried out at temperatures ranging from 350°C to 550°C with Paleozoic source rocks,and the Ro value and C,H,O composition of the kerogens were determined.The results show that:(1) to calibrate thermal evolution degree of kerogen of the Middle-Upper Proterozoic and Lower Paleozoic source rocks lack of vitrinite,coal with similar maturity to the source rock can be used by reacting together with the source rock throughout the thermal simulation experiment process,and it is efficient;(2) H/C and O/C atomic ratios of kerogen correlate highly to its maturity by exhibiting a consistent decrease of H/C atomic ratio with the increase of thermal maturity for all types of kerogens, whereas 0/C atomic ratio decreases separately along individual paths for types Ⅰ,Ⅱ and Ⅲ kerogens with the increase of thermal maturity that meets at last at a high maturity with RO value around 3. 5 %;( 3 ) there is a mathematical correlation betwe en H/C and O/C atomic ratios of kerogen (RH/C and RO/C ) and the thermal maturity of organic matter characterized by vitrinite reflectance (RO) can be expressed as LgRO= 0.133 1一1.190 5 LgRH/C-0.054 4 LgROC,which is suitable for all types of kerogens.

关 键 词：干酪根热演化 热模拟实验 H/C原子比 O/C原子比 干酪根成熟度 

分 类 号：TE122.113[石油与天然气工程—油气勘探]