Earth Science Frontiers ›› 2023, Vol. 30 ›› Issue (6): 462-472.DOI: 10.13745/j.esf.sf.2023.2.71

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Enrichment model and exploration potential for unconventional oil and gas in troughs, Erlian Basin

XIANG Xin1(), HUANG Chuanyan2,*(), CAO Lanzhu1, CAO Qiang2, JIANG Tao1, ZHANG Yufei1, SONG Yu2, XU Jie3   

  1. 1. PetroChina Huabei Oilfield Company, Renqiu 062552, China
    2. School of Earth Resources, China University of Geosciences (Wuhan), Wuhan 430000, China
    3. Mud Logging Company,BHDC,CNPC, Renqiu 062552, China
  • Received:2022-06-19 Revised:2022-10-28 Online:2023-11-25 Published:2023-11-25

Abstract:

Oil and gas exploration nowadays is increasingly directed toward the center and deep layers of lake basins. In the Erlian Basin the remaining ~800 million tons of unconventional petroleum resources are mainly distributed in troughs of oil-rich depressions, with great shale oil potential. This paper seeks to summarize and improve the theoretical understanding of unconventional petroleum geology in oil-rich lake basins by studying the geological characteristics, accumulation and enrichment mechanism and accumulation model of unconventional oil and gas in the Erlian Basin. The accumulation of interbedded type shale oil in the basin occurs in multiple troughs-preferably at trough edges-via a two-stage process: “accumulation before tightening” (Tenger stage (120 Ma)) and “accumulation after tightening” (Saihan stage (105 Ma)). The degree of shale oil enrichment in high-charge dynamic enrichment areas is controlled by sandbody dimensions, while in low-charge areas it is controlled by “sweet-spot” reservoirs development status. And there are two enrichment mechanisms for interlayer type shale oil: “reservoir control” and “hydrocarbon generation control.” Based on these results a hydrocarbon accumulation model is constructed for the entire oil reservoir series in slope belts and troughs of the Erlian Basin, which is summarized as “conventional/unconventional oil coexistence, hydrocarbon orderly distribution, trough-wide accumulation and differential enrichment.” Results of this study boost our confidence in finding interbedded type shale oil at source-rock edges and interlayer type shale oil within source rocks in the interior of lake basins.

Key words: shale oil, enrichment model, trough, Erlian Basin, exploration potential

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