The proven reserves of the Ordovician fracture-cave reservoir in Tahe Oilfield are nearly1.4 billion tons. At present,the oilfield has entered the middle-late stage of development. Problems such as high water cut,contradictory injectionproduction relationship,strong heterogeneity and low recovery factor appear. Therefore,the establishment of a fine reservoir geological model is urgent. According to the genesis,the karst reservoirs can be divided into three types,including weathering crust type,fault-controlled type,and underground river type. The development characteristics of karst reservoirs with three different genesis are analyzed in typical fracture-cave Units S74,S65,T7-615,respectively. Taking Unit S65 in which all three types are developed as an example,a discrete reservoir geological model is established for each type,and then a complete reservoir model is formed by combining pores,caves and fractures together. For the establishment of property parameter model,based on the numerous reservoir types identified from imaging well logging,and combining with the wave impedance of reservoir and porosity interpreted from well logging of single well,the relationship between the wave impedance and porosity of different types of fracture-cave reservoirs is quantitatively summarized,and the porosity data volume is obtained directly from the inversion of wave impedance data volume. The final reserves calculation result is consistent with the dynamic prediction results.
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YU Zhichao, WANG Zhizhang, WEI Hehua, XIAO Fengying, LI Yongqiang. Characterization of fracture-cave karst reservoirs with different genesis in Tahe Oilfield[J]. Petroleum Geology and Recovery Efficiency,2019,26(6):53~61