Oil & Gas Geology ›› 2024, Vol. 45 ›› Issue (4): 1064-1078.doi: 10.11743/ogg20240412

• Petroleum Geology • Previous Articles     Next Articles

Characteristics of source rocks in the Cambrian Xiaoerbulake Formation in the northwestern Tarim Basin

Yongjin GAO1,2(), Chengming YIN1,2, Lihong LIU1,2(), Darong XU3, Youxing YANG1,2, Yuanyin ZHANG4, Zezhang SONG5, Mantong ZHEN6   

  1. 1.Key Laboratory of Unconventional Oil and Gas Resources,Oil and Gas Resources Survey,China Geological Survey,Beijing 100083,China
    2.National Key Laboratory for Multi-resource Collaborated Green Development of Continental Shale Oil,Oil and Gas Resources Survey,China Geological Survey,Beijing 100083,China
    3.Xinjiang Boyuan Petroleum and Natural Gas Development Co. ,Ltd. ,Xinjiang Akesu 843600,China
    4.Institute of Energy,Peking University,Beijing 100091,China
    5.College of Geosciences,China University of Petroleum (Beijing),Beijing 102249,China
    6.School of Earth Sciences and Resources,China University of Geosciences (Beijing),Beijing 100083,China
  • Received:2024-01-05 Revised:2024-07-22 Online:2024-09-05 Published:2024-09-05
  • Contact: Lihong LIU E-mail:gaoyongjin@mail.cgs.gov.cn;liulihong713@163.com

Abstract:

In recent years, a series of discoveries and breakthroughs in hydrocarbon exploration have been achieved in the Cambrian strata in the northwestern Tarim Basin (hereafter referred to as the study area). Therefore, investigating the characteristics of the Cambrian source rocks holds great significance for guiding subsequent hydrocarbon exploration efforts. Previous studies have generally suggested that the Cambrian marine source rocks in the Tarim Basin primarily occur in the Lower Cambrian Yuertusi Formation. To investigate the characteristics of source rocks in a new sequence in the Cambrian Xiaoerbulake Formation, we conduct petrologic and geochemical analyses of samples collected from four wells (i.e., wells BY1, KTJ1, KPN1, and XSC1) and three outcrops. The analytical results indicate that the source rocks in the formation in the study area consist predominantly of argillaceous limestones and mudstones. The test results of samples show that the lower member of the Cambrian Xiaoerbulake Formation exhibits average total organic carbon (TOC) contents of 1.55 %, 2.39 %, 0.45 %, 0.89 % (for the four wells), and 1.10 % (for the three outcrops), respectively, suggesting fair-to-good source rocks. The formation’s source rocks contain sapropelic parent materials, with bitumen reflectance values ranging between 2.23 % and 2.57 %, suggesting overmature organic matter and natural gas-prone source rocks. These source rocks vary in thickness from approximately 20 to 90 m, exhibiting higher quality in the middle to lower members than in the upper member. Drilling results and seismic profiles reveal that these source rocks principally occur in the intra-platform depression centered on wells BY1 and KTJ1, establishing this depression as the most favorable area for the occurrence of source rocks.

Key words: geochemical analysis, hydrocarbon-generating potential, source rock, Xiaoerbulake Formation, Keping fault uplift, Tarim Basin

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