Pressure Buildup or Falloff Test Analysis for a Well in Commingled Reservoirs with Flow Rate Profile Logging

Abstract

Abstract Description of layered reservoirs is important from a reservoir evaluation and management standpoint because layering affects primary and secondary oil recovery and large variations in permeability-thickness product or skin in different layers have great influence on well performance and production. Commingled reservoirs, where each layer has the same initial pressure without crossflow and layers may have distinct values for thickness, permeability, porosity, fracture half length and skin factor, have been investigated by many authors. Most of research work in multilayered well test analysis focus on estimating individual layer permeabilities, skin factors, fracture half length and formation pressures from well test data. But previous research work indicated that conventional buildup and drawdown(or falloff and injection) testing for wells in commingled reservoirs is only used for determining average reservoir parameters and could not be used for determining individual layer parameters in the absence of the use of the entire history of wellbore pressure and layer production. This paper presents new testing and analysis techniques without using entire history of wellbore pressure and layer production to obtain individual layer permeabilities, skin factors, racture half length and formation pressures for a well in commingled reservoirs by using stabile flow rate data from flow profile tests acquired with production logging tools at the top of each layer before shutting-in the well and conventional pressure buildup or falloff data from the well. Before making any multilayer analysis, conventional well test analysis or type-curve analysis using log-log and derivative methods should be performed to estimate average permeability, ,fracture half length and skin factors of the total system. It can then be used as initial input values for simultaneous interpretation using an analytical model combined with nonlinear least squares estimation and type curves to estimate individual-layer permeabilities, skin factors, fracture half length and reservoir pressures. But If we use entire history of wellbore pressure and layer production, we can reduce the multiple solutions, to enhance the reliability of interpretation results.