Earth Science Frontiers ›› 2022, Vol. 29 ›› Issue (6): 84-108.DOI: 10.13745/j.esf.sf.2022.8.13

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Hydrocarbon occurrence and accumulation processes in reformed basins—theories outline

LIU Chiyang1,2(), HUANG Lei1,2, ZHAO Junfeng1,2, WANG Jianqiang1,2, ZHANG Dongdong1,2, ZHAO Hongge1,2, SHAO Deyong1,2, LIU Weishuai1,2   

  1. 1. Institute of Petroliferous Basin, Northwest University, Xi'an 710069, China
    2. State Key Laboratory of Continental Dynamics, Northwest University, Xi'an 710069, China
  • Received:2022-07-07 Revised:2022-07-30 Online:2022-11-25 Published:2022-10-20

Abstract:

One of the distinguishing features of sedimentary basins in China is widespread, strong late-stage reformation. Late-stage basin reformation has a profound impact on the hydrocarbon occurrence conditions and accumulation processes, and poses significant challenges to geological research and oil and gas exploration. Reformed basins and the affected areas have become important targets for petroleum exploration and resource replacement in China. The five main types of late-stage reformation are uplift-denudation, subsidence-deep burial, thermal action, fluid activity, and tectonic deformation. In nature, complex reformation involving concurrent geological processes is more common. Reformed basins are structurally diverse, where petroleum occurrence and accumulation involve a combination of many reservoirs types. In this paper, the core theories of hydrocarbon occurrence and accumulation in reformed basins are outlined, which can be summarized into the ideas of ‘source control by prototype basin, reservoir control by diagenetic process, accumulation control by reformation, multi-source accumulation, dynamic accumulation-dispersion, and late positioning’. ‘Source control by prototype basin’ means the source rock of a reformed basin is formed in the hydrocarbon-rich sag of the prototype basin prior to reformation, and its current scale and property determines the hydrocarbon richness and hydrocarbon distribution in the basin. Two major diagenetic processes—original material deposition-burial and secondary reformation-remodeling—control the formation and preservation of various types of reservoirs—so is called ‘reservoir control by diagenetic process’. And ‘accumulation control by reformation’ refers to the regional late-reformation features and outcomes have direct control on the hydrocarbon occurrence, accumulation-positioning and distribution in the region. Multiple late-reformations can lead to multi-source reservoir developments, such as co-reservation and accumulation of hydrocarbons from source rocks with variable depth and maturity, mixed hydrocarbons from source rocks of different types and generations, as well as co-storage/co-existence of hydrocarbon and various non-hydrocarbon gases in the same basin. The basin has undergone multi-stage tectonic evolution and reformation, which inevitably lead to hydrocarbons multi-stage dynamic accumulation-dispersion and late-stage accumulation-positioning. Understanding the late-stage accumulation and positioning can help to understand the formation mechanisms of most hydrocarbon reservoirs of different eras.

Key words: reformed basin, hydrocarbon occurrence and accumulation, outline of theories, source control by prototype basin, reservoir control by diagenetic process, accumulation control by reformation, late positioning

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