Earth Science Frontiers ›› 2024, Vol. 31 ›› Issue (4): 219-236.DOI: 10.13745/j.esf.sf.2023.9.5

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Characteristics of deep karst fracture-cavity reservoir formation controlled by multi-phase faults matching in the northern Tarim Basin

LI Fenglei1,2,3(), LIN Chengyan1,2,3, REN Lihua1,2,3, ZHANG Guoyin1,2,3, GUAN Baozhu4   

  1. 1. National Key Laboratory of Deep Oil and Gas, China University of Petroleum (East China), Qingdao 266580, China
    2. Shandong Key Laboratory of Oil Reservoir Geology, Qingdao 266580, China
    3. School of Geosciences, China University of Petroleum (East China), Qingdao 266580, China
    4. Research Institute of Petroleum Exploration and Development,Tarim Oilfield Company, PetroChina, Korla 841000, China
  • Received:2023-05-26 Revised:2023-07-11 Online:2024-07-25 Published:2024-07-10

Abstract:

Investigating the correlation between multi-phase tectonic activity and deep reservoir formation is crucial for oil and gas exploration endeavors. Utilizing seismic data from the Halahatang, Jinyue, and Fuman oilfields, coupled with an analysis of field geological outcrop faults, various seismic fine interpretation methods were employed to delineate faults within the study area. Building upon an understanding of the Middle Cambrian Yuertusi source rock and the characteristics of the Caledonian, Hercynian, and Himalayan accumulation stages, faults controlling oil accumulation were classified into four stages: Early Caledonian, Middle and Late Caledonian, Late Hercynian, and Himalayan. Further analysis of the inheritance relationship, source characteristics, and adjustment effects of multi-stage fractures, along with an assessment of various types of karst fracture-cavity reservoir development, led to discussions on the variations in karst fracture-cavity reservoirs under the influence of strike-slip faults in the study area. Key findings include: (1) Identification of primary factors influencing oil and gas reservoirs, including intra-source faults from the early Caledonian normal fault system facilitating hydrocarbon expulsion from Cambrian source rocks, and outer source faults formed during the late Caledonian enabling communication with source rocks for oil and gas migration and accumulation. Four source rocks-linking models were established based on this understanding. (2) Recognition of three main hydrocarbon generation periods in the study area: late Caledonian, Hercynian, and Himalayan, with inherited development of northwest strike-slip fractures into the Permian during the Late Hercynian period, impacting Garridonian reservoirs, and destruction and adjustment of early oil and gas reservoirs by northeast strike-slip fault systems inherited to the Neogene during the Himalayan period. Three modes of oil and gas remigration were established. (3) Establishment of six types of strike-slip fault control grades based on fracture matching relationships, along with classification of Middle and Late Caledonian strike-slip fault zones in the study area. A mining status map revealed a high matching degree between differential reservoir-controlling faults and oil and gas production. (4) Joint control of reservoirs by strike-slip faults and karstification in the study area, with an established matching relationship between the multi-stage fault system and various types of karst fracture-cavity reservoirs. This understanding has been successfully applied to well location exploration in the study area, yielding favorable results and providing guidance for the exploration and development of karst fracture-cavity reservoirs controlled by strike-slip faults.

Key words: ultra-deep fault-controlled fracture-cavity reservoirs, Northern Tarim Basin, source rocks-linking fault, hydrocarbon adjustment, accumulation model

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