Abstract: Tahe oilfield is the largest carbonate reservoir characterized by complex of karst fractures and cavities, with strong lateral and vertical heterogeneity. Most wells in it are not hydrodynamicly connected. The primary oil recovery of single well in a blocked reservoir is as low as 2.5%～5.5% with 30%～90% production declined rate and the maximum oil recovery is only around 12%. For this reason, cyclic water injection process in single well is applied to the reservoir development as a pilot test in Tahe oilfield. The numerical simulation study indicates that this process is feasible and extended to the whole field. In 110 wells, the water injection rate amounts to 132.18×10⁴t, the incremental oil production reaches 45.25×10⁴t, showing the daily increased single well production rate ranges from 13 t to 164 t and the cyclic incremental production rate ranges from 55 t to 3 076 t. As a typical example, the dead production well, Well X81, has reached an extra 12.67% oil recovery following the cyclic water injection.

Key words: Tahe oilfield, carbonate reservoir, cyclic water injection, recovery efficiency, operation process