Oil & Gas Geology ›› 2013, Vol. 34 ›› Issue (5): 619-624.doi: 10.11743/ogg20130506

• Petroleum Geology • Previous Articles     Next Articles

Paleogeomorphology characteristics and oil accumulation patterns of Chang 1 oil reservoir in the Yanchang Formation,Ordos Basin: a case study of W area in the northern of Shaanxi

Zhang Fengqi1, Yan Xiaoyong2, Wu Fuli1, Li Zhao3, Wang Weixi3, Bai Erlin3   

  1. 1. School of Earth Sciences and Engineering, Xi'an Shiyou University Xi'an, Shaanxi 710065, China;
    2. School of Geosciences, China University of Petroleum, Beijing 102249, China;
    3. Shaanxi Yanchang Petroleum (Group)Co., LTD, Xi'an, Shaanxi 710075, China
  • Received:2013-03-25 Revised:2013-08-08 Online:2013-10-08 Published:2013-10-08

Abstract:

Revealing the accumulation patterns of Chang 1 oil reservoir of the Yangchang Formation in Ordos Basin is very significant for oil and gas exploration in this area.Based on stratigraphic division and correlation,the paleogeomorphology of Chang 1 oil reservoir is restored by using residual thickness methods combined with previous research of regional paleogeomorphology.On this basis,its relationship with the distribution of hydrocarbons is analyzed.The patterns of hydrocarbon accumulation of this formation in this region are summarized through a comprehensive analysis of various controlling factors on hydrocarbon accumulation such as structures,sedimentary facies,sandstone thickness,sealing conditions,and so on.Three geomorphic units are recognized in Chang 1 oil reservoir,namely erosion valley,erosion slope and erosion monadnock.The paleogeomorphology features in "one valley,two slopes and two monadnocks".The erosion monadnocks in relatively higher terrain,the ridges of nose-like uplift,channel sands with larger thickness and higher net-to-gross ratio all have significant controlling effects on distribution of hydrocarbons of this formation.Moreover,cyclical mudstone,tight sandstone,erosion unconformity surfaces and hydrodynamic force all have large contributions to the sealing of the Chang 1 oil reservoir.Structural-lithologic reservoir and lithologic reservoir are the primary reservoir types,while lithologic-hydrodynamic reservoir is the secondary reservoir type.The overlapping regions of the main factors,such as the higher paleogeomorphology and the favorable sedimentary facies zones with larger sandstone thickness are the key exploration targets of this formation in Ordos Basin.

Key words: paleogeomorphology, hydrocarbon enrichment, reservoir type, Chang 1 oil reservior, Ordos Basin

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