Earth Science Frontiers ›› 2009, Vol. 16 ›› Issue (6): 349-358.

• Article • Previous Articles     Next Articles

Differential hydrocarbon migration and entrapment in the karstified carbonate reservoir: A case study of Well TZ83 block of the central Tarim uplift zone.

XIANG Cai-Fu, WANG Jian-Zhong, LONG Xiong-Ai, JIANG Zhen-Hua, LIU Luo-Fu, LI Su-Mei   

  1. 1State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China
    2Basin and Reservoir Research Center, China University of Petroleum, Beijing 102249, China
  • Received:2009-04-02 Revised:2009-11-20 Online:2009-12-16 Published:2009-12-10

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Abstract:

 The mechanism of hydrocarbon migration and entrapment occurring in complex carbonate porefissurefracture reservoirs is a key problem for effective hydrocarbon exploration and development of the lower part of an overlapped basin. The production, gas/oil ratio and the composition of crude oils and natural gas in the TZ83 Well block are high at the intersection point of the NE and NWstrike fault and decrease gradually along the ridge of the structure. A basic model of the porefissurefracture system is built based on the achievements in the research on carbonate karstification. The processes of the hydrocarbon migration and entrapment in this system are analyzed, which indicates that an understanding of the complexity of differential hydrocarbon migration is a key to interpreting this phenomenon. Hydrocarbon must charge the nearest compartment until it can migrate further away to charge other compartments on its pathway in the complex porefissurefracture system. As a result, gas is enriched near the hydrocarbon injection point and drives away the oil which is enriched in compartments farther from the injection point; and the complex gasoilwater relationship is controlled by the lateral connected networks. Thus, we indicate that the fault intersection point is the injection point of the oil and gas and that the main pathway system is distributed along the ridge of the structure. The theory of differential hydrocarbon migration in the porefissurefracture system suggests that (1) in hydrocarbon exploration, the structure of the fissurefractures system should be described first, then the special distribution of gasoilwater is predicted according to the main charging point and the main pathway system; and that (2) the exploration should be confined to the hydrocarbon charging point and the main pathway systems. An exploration area should not be abandoned merely due to the failure in some wells.

Key words: differential hydrocarbon migration and entrapment; karstification; porefissurefracture reservoir; overlapped basin; central Tarim Uplift Zone