Acta Petrolei Sinica ›› 2023, Vol. 44 ›› Issue (10): 1624-1636.DOI: 10.7623/syxb202310004

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Geochemical characteristics of source rocks and oil-source correlation in Kaiping sag, Pearl River Mouth Basin

Peng Guangrong1,2, Guo Jing3,4, Jiang Fujie3,4, Jiang Dapeng1,2, Wu Yuqi3,4, Chen Zhaoming1,2, Song Zezhang3,4, Gao Zhongliang1,2, Zhang Yuqi3,4   

  1. 1. Shenzhen Branch, CNOOC China Ltd., Guangdong Shenzhen 518054, China;
    2. CNOOC Deepwater Development Co., Ltd., Guangdong Shenzhen 518054, China;
    3. National Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum (Beijing), Beijing 102249, China;
    4. College of Geosciences, China University of Petroleum(Beijing), Beijing 102249, China
  • Received:2022-11-02 Revised:2023-04-14 Online:2023-10-25 Published:2023-11-03

珠江口盆地开平凹陷烃源岩地球化学特征与油源对比

彭光荣1,2, 郭婧3,4, 姜福杰3,4, 姜大朋1,2, 吴宇琦3,4, 陈兆明1,2, 宋泽章3,4, 高中亮1,2, 张宇琦3,4   

  1. 1. 中海石油(中国)有限公司深圳分公司 广东深圳 518054;
    2. 中海石油深海开发有限公司 广东深圳 518054;
    3. 中国石油大学(北京)油气资源与工程全国重点实验室 北京 102249;
    4. 中国石油大学(北京)地球科学学院 北京 102249
  • 通讯作者: 姜福杰,男,1979年12月生,2008年获中国石油大学(北京)博士学位,现为中国石油大学(北京)教授、博士生导师,主要从事油气成藏机理与分布规律的研究工作。Email:jiangfj@cup.edu.cn
  • 作者简介:彭光荣,男,1978年8月生,2005年获中国石油大学(北京)硕士学位,现为中海石油(中国)有限公司深圳分公司高级工程师,主要从事油气地质与油气勘探综合研究工作。Email:penggr@cnooc.com.cn
  • 基金资助:
    中国海洋石油集团有限公司"十四五"重大科技项目"南海北部深水区勘探关键技术"(KJGG2022-0103)资助。

Abstract: In Pearl River Mouth Basin, Kaiping sag is located in the deep-water continental slope area beyond the existing continental shelf slope break zone, where oil and gas resources are less explored. It is of great significance to carry out source rock evaluation and clarify its crude oil source for deepening the understandings of oil and gas accumulation in Kaiping sag and guiding the next step of oil and gas exploration. Based on the test data including TOC content, rock pyrolysis, source rock and crude oil biomarker characteristics, the paper systematically analyzes the geochemical characteristics of source rocks of Wenchang Formation and Enping Formation, and conducts the oil-source correlation. The results show that:(1) The argillaceous source rocks of the Lower and Upper Wenchang Formation and Lower Enping Formation tend to be thick in the core area of Kaiping sag and gradually thinned towards the peripheral slope zone, of which the medium to high organic matter abundance and Type Ⅱ1-Ⅱ2 kerogen demonstrate that they are in the mature stage as a whole. (2) The source rocks of Wenchang Formation has the low values of Pr/Ph, C19+20TT/C23TT and low to medium OL/C30H. C27-C28-C29 regular steranes on the gas chromatography-mass spectrum present "V" shape, and C30 4-methylsteranes have high abundance. The source rocks of Enping Formation have high values of Pr/Ph and C19+20TT/C23TT, as well as low values of OL/C30H and low C30 4-methylsterane content, and the distribution of C27-C28-C29 regular steranes shows an inverted "L" shaped pattern. (3) There are two types of crude oil produced from Kaiping sag. As for Type A oil, the Pr/Ph values are within the range of 1.13 and 1.82, the C19+20TT/C23TT values range from 0.32 to 0.89, the OL/C30H values are between 0.03 and 1.02, and the average relative content of C27 and C29 regular steranes is 26.20% and 46.44%, respectively. The C30 4-methylsteranes have high abundance. As for Type B oil, the Pr/Ph values are greater than 2.00, the C19+20TT/C23TT values are between 1.00 and 2.28, the OL/C30H values range from 0.04 to 0.13, and the average relative content of C27 and C29 regular steranes is 9.92% and 65.54%, respectively. The content of C30 4-methylsteranes is extremely low. (4) Oil-source correlation analysis shows that Type A oil is originated from the hybrid organic matters of Type Ⅱ and Ⅲ formed by plankton and terrestrial plants in lacustrine source rock of Wenchang Formation; Type B oil comes from the deltaic swamp mudstone of Enping Formation in the background of oxidation sedimentation, and the hydrocarbon generation parent material is dominated by Type Ⅲ organic matter formed by terrestrial higher plants. In conclusion, the research has clarified the sources of oil and gas in Kaiping sag, which is of theoretical guiding significance for future oil and gas exploration.

Key words: source rock, geochemical characteristics, oil-source correlation, Kaiping sag, Pearl River Mouth Basin

摘要: 珠江口盆地开平凹陷位于现今陆架坡折带以外的深水陆坡区,油气勘探程度较低。通过开展烃源岩评价、明确其原油来源,对深化开平凹陷油气成藏认识和指导下一步油气勘探具有重要意义。综合总有机碳含量、岩石热解及烃源岩和原油生物标志化合物特征等测试资料,系统分析文昌组和恩平组烃源岩的地球化学特征,进行油源对比。结果表明:①文昌组下段、上段和恩平组下段的泥质烃源岩均表现为"开平主洼中心厚、向周缘斜坡带依次减薄",有机质丰度中等—好,干酪根类型为Ⅱ1型、Ⅱ2型,整体处于成熟阶段。②文昌组烃源岩具有低Pr/Ph值、低C19+20TT/C23TT值、低—中等OL/C30H值,气相色谱-质谱图上C27-C28-C29规则甾烷呈"V"型,C30 4-甲基甾烷丰度高;恩平组烃源岩具有较高的Pr/Ph值和C19+20TT/C23TT值,较低的OL/C30H值、C30 4-甲基甾烷含量,C27-C28-C29规则甾烷分布呈反"L"型。③开平凹陷产出两类原油,A类原油的Pr/Ph值为1.13~1.82,C19+20TT/C23TT值为0.32~0.89,OL/C30H值为0.03~1.02,C27和C29规则甾烷平均相对含量分别为26.20%、46.44%,C30 4-甲基甾烷丰度高;B类原油Pr/Ph值大于2.00,C19+20TT/C23TT值为1.00~2.28,OL/C30H值为0.04~0.13,C27和C29规则甾烷平均相对含量分别为9.92%、65.54%,C30 4-甲基甾烷含量极低。④油源对比分析显示,A类原油来源于文昌组湖相烃源岩中浮游生物和陆源植物混合形成的Ⅱ型、Ⅲ型混合有机质;B类原油来源于氧化沉积背景的恩平组三角洲—沼泽相泥岩,生烃母质以陆源高等植物形成的Ⅲ型有机质为主。研究认识明确了开平凹陷油气来源,对未来油气勘探具有理论指导意义。

关键词: 烃源岩, 地球化学特征, 油源对比, 开平凹陷, 珠江口盆地

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