Research on well selection method for high-pressure water injection in fractured-vuggy carbonate reservoirs in Tahe oilfield

Carbonate fractured vuggy reservoir in Tahe oilfield belongs to fractured vuggy reservoir with strong heterogeneity. After a period of production, the elastic energy of the cave formation weakens caused insufficient liquid supply, It is faced with a series of problems in some single wells, such as low water injection efficiency, high water cut, short production period, and so on. The introduction of high-pressure water injection technology can greatly restore the productivity of single wells and improve reservoir recovery. It is one of the effective new technology to develop fractured vuggy carbonate reservoirs. At present, this technology is still in the initial stage, with no clear guide method that selecting wells for high-pressure water injection. Among them, the determination of the high-pressure water injection well selection method is particularly important for the development effect of a single well. Based on the analysis of the mechanism of high-pressure water injection and combined with the field data, this paper formulates the well selection method of high-pressure water injection from three aspects: Karst Characteristics, reservoir structure and reservoir parameters:(1)Karst geological data show the characteristics of oil-increasing substances such as many abnormal bodies around the well and wide lateral distribution; (2)The reservoir structure has multiple sets of connected karst caves with connectivity potential; (3)After the failure of conventional water injection, the fracture passage effect is poor and the energy of the remote well is insufficient. The independent high-pressure water injection development method can reduce the channel seepage resistance, expand the scope of the injected water, and realize increased production. Up to now, Tahe oilfield has used the method to implement high-pressure water injection 41 well, achieving an average single well cumulative incremental oil production of 3211 tons, with an effective rate of 85.4%, which has a satisfactory application value.