石油与天然气地质 ›› 2024, Vol. 45 ›› Issue (2): 393-405.doi: 10.11743/ogg20240207

• 油气地质 • 上一篇    下一篇

鄂尔多斯盆地中、东部奥陶系马家沟组成烃生物及烃源岩地球生物学评价

万俊雨1,2(), 朱建辉1,2, 姚素平3, 张毅1,2, 李春堂4, 张威4, 姜海健1,2, 王杰1,2   

  1. 1.中国石化 石油勘探开发研究院 无锡石油地质研究所，江苏 无锡 214126
    2.中国石化 油气成藏重点实验室，江苏 无锡 214126
    3.南京大学 地球科学与工程学院，江苏 南京 210023
    4.中国石化 华北油气分公司，河南 郑州 450006
  • 收稿日期:2023-12-27 修回日期:2024-02-01 出版日期:2024-04-30 发布日期:2024-04-30
  • 第一作者简介:万俊雨（1993—），男，博士、助理研究员，成烃生物和油气地质。E-mail： wanjy7971.syky@sinopec.com。
  • 基金项目:
    中石化集团公司重大项目(P23229);子课题(P23244)

Geobiological evaluation of hydrocarbon-generating organisms and source rocks in the Ordovician Majiagou Formation， east-central Ordos Basin

Junyu WAN1,2(), Jianhui ZHU1,2, Suping YAO3, Yi ZHANG1,2, Chuntang LI4, Wei ZHANG4, Haijian JIANG1,2, Jie WANG1,2   

  1. 1.Wuxi Institute of Petroleum Geology，Petroleum Exploration and Production Research Institute，SINOPEC，Wuxi，Jiangsu 214126，China
    2.Key Laboratory of Hydrocarbon Accumulation Mechanisms，SINOPEC，Wuxi，Jiangsu 214126，China
    3.School of Earth Sciences and Engineering，Nanjing University，Nanjing，Jiangsu 210023，China
    4.North China Petroleum Bureau，SINOPEC，Zhengzhou，Henan 450006，China
  • Received:2023-12-27 Revised:2024-02-01 Online:2024-04-30 Published:2024-04-30

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摘要：

近年来鄂尔多斯盆地中、东部奥陶系马家沟组盐下天然气勘探取得重大突破，但马家沟组碳酸盐岩-膏盐岩组合总有机碳含量（TOC）普遍较低，寻找优质烃源岩、研究其形成条是勘探急需解决的问题。用鄂尔多斯盆地中、东部马家沟组岩心样品，分析古生态、古环境及成烃生物，研究成烃生物的组合特征及其随古环境的变化。用生境型和生源Ba元素含量作为生物学评价指标，用元素含量比值V/（V+Ni）指标和蒸发盐矿物种类作为地质学评价指标，开展了烃源岩地球生物学分级评价。研究表明：①鄂尔多斯盆地马家沟组成烃生物为浮游藻类、底栖红藻、底栖褐藻和和底栖蓝藻4大类。②马家沟组沉积期具备较高生物生产力烃源岩发育的条件。高频的海平面变化和气候干、湿交替导致了水体盐度和氧化还原条件的频繁变化，因此有机质的保存条件是该地区烃源岩形成发育的关键因素。③有利烃源岩发育的地球生物相为耐盐菌藻膏云潟湖边缘相，其次为浮游藻浅潮下带泥云坪和膏泥潟湖相。④烃源岩地球生物学评价结果与残余有机碳丰度评价结果相比，烃源岩相对更好，好的烃源岩是暗色泥质纹层或条带的含膏泥质白云岩、含泥白云岩、石膏质泥岩和白云质泥岩。

关键词: 地球生物学, 成烃生物, 烃源岩, 马家沟组, 奥陶系, 鄂尔多斯盆地

Abstract:

Over recent years， breakthroughs have been achieved in the pre-salt natural gas exploration in the Ordovician Majiagou Formation， east-central Ordos Basin. Given the generally low total organic carbon （TOC） content in the carbonate-evaporite assemblages in the formation， there is an urgent need to seek high-quality source rocks and investigate their formation conditions. Using core samples from the Majiagou Formation in the east-central Ordos Basin， we analyze the formation’s paleoecology， paleoenvironment， and hydrocarbon-generating organisms， delving into the characteristics of hydrocarbon-generating organism assemblages and their changes with the paleoenvironment. Furthermore， we perform geobiological grading evaluation using habitat types and biogenic Ba as biological indices， alongside the V/（V+Ni） ratio and mineral types in evaporites as geological indices. Key findings are as follows： （1） The hydrocarbon-generating organisms in the Majiagou Formation encompass planktonic algae， benthic red algae， benthic brown algae， and benthic blue-green algae. （2） During the deposition of the Majiagou Formation， water bodies with high biological productivity created conditions for the formation of source rocks. Specifically， the high-frequency sea-level fluctuations and the alternating dry and wet climates induced frequent changes in the salinity and redox conditions of water bodies. Therefore， the favorable conditions for organic matter preservation serve as the key to the formation of source rocks in the study area. （3） Geobiological facies favorable to source rock formation primarily include the marginal facies of gypsum-dolomite lagoons with halophilic algae. The mud-dolomite flat facies and gypsum-mud lagoon facies found in the shallow subtidal zones of planktonic algae， are to follow. （4） Compared with the results of residual organic carbon abundance evaluation， those of source rock geobiology are more optimistic. The effective sources rocks mainly include are gypsiferous argillaceous dolomites， argillaceous dolomites， gypsum mudstones， and dolomitic mudstones， all present as dark shaly laminae or bands.

Key words: geobiology, hydrocarbon-generating organism, source rock, Majiagou Formation, Ordovician, Ordos Basin

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