Oil & Gas Geology ›› 2012, Vol. 33 ›› Issue (6): 845-852.doi: 10.11743/ogg20120604

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Hydrocarbon accumulation process of Chang-8 low-permeability lithological reservoirs in Zhenjing area,Ordos Basin

Li Weilian1,2, Liu Zhen1,2, Wang Wei1,2, Pan Gaofeng1,2, Zhao Shu3, Zhang Jian3   

  1. 1. College of Geosciences, China University of Petroleum, Beijing 102249, China;
    2. State Key Laboratory of Petroleum Resource and Prospecting, China University of Petroleum, Beijing 102249, China;
    3. Exploration and Development Research Institute, Huabei Branch Company of SINOPEC, Zhengzhou, Henan 450006, China
  • Received:2011-07-11 Revised:2012-10-20 Online:2012-12-28 Published:2013-01-10

Abstract:

In order to better understand the characteristics and main controlling factors of hydrocarbon accumulation in low-permeability lithological reservoirs of Member 8 of Yanchang Formation(Chang-8)in Zhenjing area,Ordos Basin,we performed dynamic analysis of the Chang-8 lithological reservoirs based on study of burial history,thermal history,hydrocarbon generation history and diagenetic process.The evolution features of various hydrocarbon accumulation factors were clarified such as porosity,timing of traps,formation pressure of source rocks and the window of hydrocarbon charging kinetics.Finally,a comprehensive analysis of the dynamic process of hydrocarbon accumulation was performed.The results indicate that porosity of Chang-8 reservoir was of 20% during hydrocarbon accumulation in the middle Early Cretaceous and lowered progressively to current 12% due to reservoir tightening of the later evolution stage.The lithological traps of the Chang-8 were formed at the Late Jurassic and kept on developing till now,thus they are characterized by early formation and long process of development.The formation pressure of Chang-7 source rocks was 22 MPa during the period of hydrocarbon accumulation.It increased up to 35 MPa with a pressure coefficient of 1.5 at the end of Early Cretaceous and later lower progressively to normal pressure in the Neogene.The charging pressure of oil was 15 MPa higher than the pressure of resistance,and the window of hydrocarbon accumulation lasted for a long time from the Early Cretaceous to the end of Neogene.The formation of the low-permeability lithological reservoirs in the Chang-8 is controlled by the favorable temporal and spatial matching of between the factors and process of hydrocarbon accumulation.Physical properties of sandstone and charging kinetics are the main factors controlling hydrocarbon accumulation.

Key words: hydrocarbon accumulation element, accumulation process, low-permeability sandstone, lithological reservoir, Yanchang Formation, Zhenjing area, Ordos Basin

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