Mature field redevelopment involves the choice and implementation of different extraction techniques. This issue becomes more complex when the producing section is composed of isolated multilayer reservoirs with long and different production history which necessitates precise mangement of injection and production rates layer by layer and well by well. Geological discontinuities (Faults, pinch outs) also need to be taken into account when considering the injection of fluids in a multi-layered reservoir.

The present work, which involves a water flood, shows a method to define the contacted pore volume (CPV) evolution in time by dynamic simulation history matching, and thereby to determine the regions in each of the layers where changes in injection policy is justified. With the CPV defined at the end of the history match, the method allows an evaluation of the efficiency of the legacy secondary recovery scheme, and defines the corrective actions to improve it in each layer. This method is based on distribution of pore volume (PV) as function of water saturation i.e. PV(Sw) at each time before and after starting the injection in the reservoir. As a result, we can obtain the evolution of CPV since injection started, and then calculate the evolution of oil in place (OIP) in the CPV and compare this with total production of the layer considered, obtaining the efficiency of waterflooding layer by layer in different areas of the field. Extrapolating CPV(t) with the actual injection patterns allows an assement of CPV at the end of field concession, and gives us a base case forecast of future field behaviour.

As conclusions we observe that, this method is an easy and fast tool to determine the contacted pore volume evolution, and the efficiency of waterflooding. Further this method gives an estimation of Ultimate Contacted Pore Volume (UCPV) with the actual (or improved) injection configurations on a regional basis which allows further opportunity to be identified. The integration of this information with the actual field condition facilitates optimization of the water injection pattern and improves waterflooding productivity throughout the reservoir extension.

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