海陆过渡相页岩地球化学及生烃演化特征——以鄂尔多斯盆地东缘大宁—吉县地区下二叠统山西组为例

Geochemical and hydrocarbon generation evolution characteristics of marine-continental transitional facies shale: a case study of the Lower Permian Shanxi Formation in the Daning-Jixian area, eastern margin of Ordos Basin

张洋洋 李勇 张雪莹 罗力元 何清波 李树新 刘向君 李翔 李星涛 杨强 陈世加 路俊刚 张楠 刘喆 余锐阳 马海川

ZHANG Yangyang LI Yong ZHANG Xueying LUO Liyuan HE Qingbo LI Shuxin LIU Xiangjun LI Xiang LI Xingtao YANG Qiang CHEN Shijia LU Jungang ZHANG Nan LIU Zhe YU Ruiyang MA Haichuan

西南石油大学 油气藏地质及开发工程全国重点实验室, 成都 610500 天然气地质四川省重点实验室, 成都 610500 西南石油大学 地球科学与技术学院, 成都 610500 自然资源部 复杂构造区非常规天然气评价与开发重点实验室, 贵阳 550001 中国石油 西南油气田分公司 重庆气矿, 重庆 401120 贵州省油气勘查开发工程研究院, 贵阳 550001 中国石油 煤层气有限责任公司, 北京 100028 中国石油 西南油气田分公司 勘探开发研究院, 成都 610041

State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu, Sichuan 610500, China Sichuan Provincial Key Laboratory of Natural Gas Geology, Chengdu, Sichuan 610500, China School of Geoscience and Technology, Southwest Petroleum University, Chengdu, Sichuan 610500, China Key Laboratory of Unconventional Natural Gas Evaluation and Development in Complex Tectonic Areas, Ministry of Natural Resources, Guiyang, Guizhou 550001, China Chongqing Gas Mine, PetroChina Southwest Oil & Gasfield Company, Chongqing 401120, China Guizhou Institute of Petroleum Exploration and Development Engineering, Guiyang, Guizhou 550001, China PetroChina Coalbed Methane Company Limited, Beijing 100028, China Exploration and Development Research Institute, PetroChina Southwest Oil & Gasfield Company, Chengdu, Sichuan 610041, China

为明确海陆过渡相页岩地球化学和生烃演化特征，以鄂尔多斯盆地东缘大宁—吉县地区下二叠统山西组页岩为研究对象，通过总有机碳(TOC)、岩石热解、干酪根碳同位素、有机显微组分、古生物、镜质体反射率(Ro)、生烃热模拟等分析测试，开展了山西组页岩矿物组成、成烃母质、生烃潜力、生烃动力学过程和累计产气率计算模型等研究。研究结果表明：(1)大宁—吉县地区山西组页岩矿物组成以石英和黏土矿物为主，平均TOC含量为4.06%，有机显微组分以腐殖无定形体和镜质组为主，平均Ro为2.61%，整体上表现为高有机质丰度、腐殖型有机质、过成熟演化阶段的特征，具有较高的生气潜力。(2)封闭体系下，山西组页岩气态烃C1和C1-5最大产率分别为138.74和139.22 mg/g；半封闭体系下，山西组页岩气态烃C1和C1-5的最大产率分别为86.51和102.59 mg/g，远低于封闭条件下气态烃最大产率。(3)山西组页岩气态烃产物C1和C1-5的活化能均出现了两个明显的高峰，分别代表了干酪根降解和重烃二次裂解，C1活化能两个高峰分别为56 kcal/mol(26.53%)和61 kcal/mol(30.10%)，频率因子为2.0×1011 S-1，C1-5活化能两个高峰分别为56 kcal/mol(28.45%)和61 kcal/mol(19.18%)，频率因子为2.2×1011 S-1。(4)山西组海陆过渡相页岩累积产气率与Ro的变化趋势具有y=1/(1+e-x)的函数特征，并建立了两种体系下的累计产气率计算模型。研究成果为海陆过渡相页岩气资源量计算和有利区预测提供了重要的理论支持。

To clarify the geochemical and hydrocarbon evolution characteristics of marine-continental transitional facies shale, the shale in the Lower Permian Shanxi Formation of the Daning-Jixian area in the eastern margin of the Ordos Basin was taken as the research object. By analyzing and determining total organic carbon (TOC) content, rock pyrolysis, kerogen carbon isotopes, maceral composition, paleontology, vitrinite reflectance (Ro), and conducting hydrocarbon generation thermal simulations, the study investigated the mineral composition, hydrocarbon source, generation potential, generation kinetics, and cumulative gas production rate calculation models of the shale in the Shanxi Formation. The results showed that: (1) The mineral composition of the shale in the Shanxi Formation of the Daning-Jixian area was mainly composed of quartz and clay minerals, with an average TOC content of 4.06%. The organic macerals were mainly composed of humic amorphous bodies and vitrinites, with an average Ro value of 2.61%. Overall, the shale was characterized by high organic matter abundance, dominated by humic-type organic matter, and was at an overmature stage of evolution, demonstrating high gas generation potential. (2) In a closed system, the maximum yields of gaseous hydrocarbons C1 and C1-5 from the shale in the Shanxi Formation were 138.74 and 139.22 mg/g, respectively. In a semi-closed system, the maximum yields of C1 and C1-5 were 86.51 and 102.59 mg/g, respectively, which were significantly lower than the maximum yields under closed conditions. (3) The activation energy for the generation of gaseous hydrocarbon C1 and C1-5 from the shale in the Shanxi Formation exhibited two distinct peaks, representing kerogen degradation and secondary cracking of heavy hydrocarbons. For C1, the two peaks of activation energy were 56 kcal/mol (26.53%) and 61 kcal/mol (30.10%), with a frequency factor of 2.0×1011 S-1. For C1-5, the two peaks of activation energy were 56 kcal/mol (28.45%) and 61 kcal/mol (19.18%), with a frequency factor of 2.2×1011 S-1. (4) The variation trend between cumulative gas production rate and Ro for the marine-continental transitional facies shale in the Shanxi Formation followed the pattern of a logistic function described by y=1/(1+e-x). Cumulative gas production rate calculation models for both the closed and semi-closed systems were established. The research results provide important theoretical support for the calculation of shale gas resources in marine-continental transitional facies and offer insights into favorable zone prediction.

中国石油—西南石油大学创新联合体科技合作项目 2020CX030000;中国石油科技创新基金 2022DQ02-0105;自然资源部复杂构造区非常规天然气评价与开发重点实验室开放课题基金 NRNG-202401

https://doi.org/10.11781/sysydz2025040857