Oil & Gas Geology ›› 2022, Vol. 43 ›› Issue (5): 1059-1072.doi: 10.11743/ogg20220505

• Petroleum Geology • Previous Articles     Next Articles

Hydrocarbon accumulation pattern and exploration prospect of the structural traps in lower play of the western Central Depression in the Junggar Basin

Jianzhong Li1(), Xiaojun Wang2, Fan Yang1(), Yong Song3, Ablimiti3, Baoli Bian3, Hailei Liu3, Xueyong Wang3, Deyu Gong1   

  1. 1.Research Institute of Exploration and Development,PetroChina,Beijing 100083,China
    2.Xinjiang Oilfield Company,PetroChina,Karamay,Xinjiang 834000,China
    3.Research Institute of Exploration and Development,Xinjiang Oilfield Company,PetroChina,Karamay,Xinjiang 834000,China
  • Received:2021-08-02 Revised:2022-07-06 Online:2022-10-01 Published:2022-09-02
  • Contact: Fan Yang E-mail:lijizh@petrochina.com.cn;yf2010@petrochina.com.cn

Abstract:

The lower play of the western Central Depression in the Junggar Basin is of favorable conditions to generating large-scale oil/gas fields. Given its low exploration maturity, the zone is a key to strategic exploration. Hydrocarbon accumulation models are established and play fairways are selected by systematically studying the structures, source rocks and reservoirs and sorting out the play element combinations of the lower play. The study shows that there are three suites of source rocks developed in the zone: the Carboniferous, the Lower Permian Jiamuhe and Fengcheng Formations and the Middle Permian Xiawuerhe Formation. Among others, the Fengcheng Formation is of high-quality source rocks deposited in alkali lake environment with great hydrocarbon generation potential and is in direct contact with the structural trap of the lower play that reaches into the Mahu Sag, indicating a good source-reservoir configuration. Reservoirs of volcanic rock type, argillaceous dolomite type and clastic rock type are well developed in the lower play, and a favorable reservoir-caprock combination is formed under the shelter of regional dolomitic mudstone seal in the Fengcheng Formation. Overpressure is generally seen in the lower play, where gas condensates and natural gas dominate the hydrocarbon phase at a burial depth below 6 200 m, prone to be of high productivity. In terms of source-reservoir configuration, three hydrocarbon accumulation models are established, that is, of source-edge draping type, source-edge juxtaposition type and intra-source overlapping type. Among others, the structural traps of the last two types have large hydrocarbon supply window developed between target reservoir and source rocks, favorable for hydrocarbon accumulation. Five play fairways are selected and evaluated, namely, the northeast ring belt of Penyijingxi Sag, Mosuowan Uplift Mazhong structural belt, west ring belt of Shawan Sag, and Dabasong nose-like salient zone, for strategic breakthroughs in oil/gas exploration in the lower play.

Key words: hydrocarbon accumulation model, argillaceous dolomite, lower play, weathering volcanic crust, structural trap, Central Depression, Junggar Basin

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