A new approach to thief zone identification based on interference test

Thief zones are those laterally continuous stratigraphic units of relatively high permeability, which come into being in the reservoir after long-term waterflooding. Injected water circulates inefficiently in reservoirs with thief zones so that the development of these reservoirs is seriously weakened in high water cut stage. Viewed as a two-layer infinite homogeneous reservoir saturated by slightly compressible fluid, a well test interpretation model is presented. Then the pressure response at the observation well is obtained by superposition principle. Finally a new approach to identifying permeability and net thickness of thief zones is established based on semilog method. The methodology has been applied to Shengtuo Oilfield, which confirms that the proposed approach can be efficiently used to identify thief zones, providing parameters of thief zones for treatment project design.