Oil & Gas Geology ›› 2018, Vol. 39 ›› Issue (2): 254-267.doi: 10.11743/ogg20180205

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The identification and characteristics of migration system induced by high pressure, and its hydrocarbon accumulation process in the Yingqiong Basin

Fan Caiwei   

  1. Zhanjiang Branch of CNOOC Ltd., Zhanjiang, Guangdong 524057, China
  • Received:2017-06-22 Revised:2018-01-21 Online:2018-04-28 Published:2018-05-16

Abstract: The Yingqiong Basin is a Cenozoic high-temperature and high-pressure basin with rapid subsidence,usually accompanied by the development of thermal fluid diapirs.This formed a unique hydrocarbon migration system,with the diapirs and fractures caused by the pressure release of deep strata functioning as the major transporting pathways of natural gas in the basin.The research distinguished 2 types of migration systems in the Yingqiong Basin:the high-pressure-diapir system and the fracture system,based on 3D seismic coherence analysis and curvature analysis along the formation.The spatial distribution characteristics of these two systems and their evolution processes have been investigated,and the relationship between the overpressured migration systems and the gas charging,dissipating and accumulating in the study area is analyzed by geochemical means such as natural gas isotopes and inclusions.The results indicate that,in spatial distribution,the two types of migration systems are characterized by stepwise development from deep to shallow:the former usually develops in the central depression zone of the Yinggehai Basin and the latter mainly distributes in the margin of thermal fluid diapirs and the high-pressure strata in the subsidence center proximity part of the steep slopes.According to the evolution history,the diaper migration system consists of five stages (types):pressurization,puncture,equilibrium,release and collapse,and at each stage the gas accumulation style features deep gas charging,shallow gas accumulating,simultaneous deep and shallow accumulating,flank accumulating,and accumulation destruction respectively.The fracture migration system originates from either high pressure or certain deformation processes,characterized with early gas accumulation in shallow strata and later gas accumulation in deep ones.

Key words: high temperature and high pressure, fracture, transmission system, diapir, Yingqiong Basin

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