Oil & Gas Geology ›› 2021, Vol. 42 ›› Issue (3): 673-689.doi: 10.11743/ogg20210313

• Petroleum Geology • Previous Articles     Next Articles

Differential evolution and origin of high-quality reservoirs in the Lower Paleozoic carbonate buried hills in Dagang prospecting area, Huanghua Depression

Xin Cheng1,2(), Lihong Zhou3, Yingchang Cao1,4,*(), Fengming Jin3, Lixin Fu3, Hongjun Li3, Da Lou3, Guanghui Yuan1,4   

  1. 1. Key Laboratory of Deep Oil and Gas, China University of Petroleum (East China), Qingdao, Shandong 266580, China
    2. Tianjin Branch of CNOOC Ltd., Tianjin 300459, China
    3. Dagang Oilfield Branch, PetroChina, Tianjin 300280, China
    4. Laboratory for Marine Mineral Resources, Qingdao, Shandong 266071, China
  • Received:2019-03-04 Online:2021-06-28 Published:2021-06-23
  • Contact: Yingchang Cao E-mail:645719710@qq.com;cyc8391680@163.com

Abstract:

The exploration for carbonate reservoirs in buried hills has been hampered by a poor understanding of their distribution and genesis.With a combination of seismic profile interpretation, core and thin section observation, logging analysis as well as geochemical and burial history analysis, the types of the Lower Paleozoic buried hills, reservoir characteristics and genesis of high-quality reservoirs in Dagang prospecting area were studied from the perspective of evolutional difference.The buried-hills in the area can be classified into five categories: monadnock, intermittently eroded fault-block buriedhill, fault-block buried hill, compressional folded buried hill and gravitational sliding folded buried hill.The monadnock resulted from a late-stage meteoric water leaching is dominated by dissolution pores and cavities, followed by some fissures.The intermittently eroded fault-block, a result of middle-stage meteoric water leaching and deep burial dissolution, is full of dissolution pores and tectonic fissures.The last three buried hills that shunned the middle- or late-stage meteoric water leaching contain reservoirs linked to faulting and deep burial and formed either by fault-related shattering-deep burial dissolution or by fault connection-TSR related dissolution.The former forms mostly composite reservoirs with dissolution pores, cavities and fissures in areas close to basement faults and would gradually turn into tectonic fissure-dominated reservoirs as they migrate away from the basement faults.The latter forms reservoirs commonly seen in deep buried formations with very high temperatures (higher than 140 ℃).These reservoirs are mainly composed of fissures, followed by some dissolution pores and cavities.It is therefore suggested that high-quality reservoirs are most probably developed in areas with the Upper Paleozoic strata heavily eroded or basement faults well developed or with the Upper Paleozoic strata developed against a high temperature setting (higher than 140 ℃).

Key words: buried hill classification, reservoir characteristics, origin of high-quality reservoirs, carbonate rock, Lower Paleozoic, Dagang prospecting area, Huanghua Depression

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