Oil & Gas Geology ›› 2013, Vol. 34 ›› Issue (2): 167-173.doi: 10.11743/ogg20130204

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Overpressure genesis and evolution of sandstone reservoirs in the 3rd and 4th members of Shahejie Formation,the Dongying Depression

Hao Xuefeng   

  1. Shengli Oilfield Company, SINOPEC, Dongying, Shandong 257015, China
  • Received:2012-11-12 Revised:2013-03-10 Online:2013-04-28 Published:2013-05-02

Abstract:

The sandstone reservoirs within the 3rd and 4th members of Shahejie Formation in Dongying Depression, the Bohai Bay Basin are moderately to strongly overpressured with the maximum pressure coefficient of 2.0 and the maximum excessive pressure of 40 MPa calculated based on the measured pressures.Analysis indicates that oil-bearing properties of the reservoirs correlate to the development degree of overpressure,and current reservoir overpressure is mainly caused by the overpressured fluids from source rocks.Integrated with basin modeling and fluid inclusions analysis,this paper reconstructed the geo-pressure evolutionary history of the sandstone reservoirs in the 3rd and 4th member of Shahejie Formation.The first stage reservoir overpressure was mainly caused by the rapid subsidence during the deposition of the 3rd member of Shahejie Formation to the end of Dongying Formation that blocked pore fluid discharging.The overpressure might be released to hydrostatic pressure along with the tectonic uplifting during the late Dongying Formation to early Guantao Formation.From the late Minghuazhen Formation to the present,the bulk of the source rock is still at peak oil generation and large amount of oil/gas-bearing overpressured fluid generated by the source rocks charge into the sandstone reservoirs,leading to the second stage overpressure.

Key words: basin modeling, fluid inclusion, overpressure genesis, reservoir overpressure, 3rd and 4th member of Shahejie Formation, Dongying Depression

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