Use of Transient Tests to Monitor Progress of Flooding in IOR / EOR Operations

Abstract

Abstract Improved and enhanced oil recovery methods (IOR and EOR, respectively) are used to increase recovery from proven reserves mainly following waterflooding. Monitoring and managing the progress of flood in IOR /EOR operations is currently a challenge to the oil industry especially in situations with large well spacing and cost prohibitive measures like drilling observation wells (e.g., offshore and deep water applications). Falloff tests have been proven successful under waterflooding operations to determine the reservoir properties in various banks around the injection wells and the location of the flood fronts (Abbaszadeh and Kamal 1989, Yeh and Agarwal 1992, and Kamal 2009). In this paper we share new development that extends transient testing and analysis technology to IOR and EOR operations during polymer flooding. With the expanded use of Permanent Downhole Pressure Gauges (PDHG), the new developed technique can be used without additional operational cost or interruption of field operations. In this paper, the effects of polymer are described by shear rate dependent viscosity (non-Newtonian flow). We developed an analytical solution of wellbore pressure by combining the non-Newtonian fluids and the multi-composite reservoir models. The solution dose not only address the polymer region where the fluids follow either the power-law (Ostwald 1929) or the Meter model (Meter and Bird 1964), but also the Newtonian flow in the oil region with varying oil and polymer saturations in both regions. The developed solution was validated by analyzing synthetic data generated using a commercial numerical reservoir simulator. The solution provides a deeper understanding about the physics behind the transient pressure behaviors during polymer flooding, and can be applied to guide a better implementation of well tests. Interpretation method for falloff tests using the new solution and the conventional Bourdet derivative and Horner plots is presented indicating that existing commercial well testing software are sufficient to analyze data with the recent development. The new solution allows us to obtain the reservoir properties such as fluid mobilities in various banks and the location of the flood front. The developed solution was applied to field data. The pressure behavior expected from the new solution was observed in field data validating our developed technique and yielding the characterization of reservoir parameters in various banks. The novelty of this method of characterizing the dynamic properties of the various banks during injection of non-Newtonian fluids and the location of the flood fronts is that an analytical solution of pressure transient behavior in two phase flow of non-Newtonian fluids and Newtonian fluids was developed, validated and used to analyze field data. This is the first analytical solution developed for this type of problem.