Polymer Solution Injection – Near Wellbore Dynamics and Displacement Efficiency, Pilot Test Results, Matzen Field, Austria

Abstract

AbstractA number of reservoirs in the Vienna Basin in Austria might benefit from polymer solution injection. In November 2011, a Polyacrylamide polymer injection pilot commenced for the 8th Torton Horizon reservoir to reduce the uncertainties related to this technology.To further improve the understanding of the polymer solution injection, laboratory experiments and numerical simulations were performed.The results of the injection test and laboratory experiments show that two phases can be distinguished: first, a phase of polymer solution injection below the Formation Parting Pressure (FPP) can be observed. This phase is characterised by high flow velocities in the near-wellbore area, resulting in severe degradation of the polymer, and a slower rise of the pressure than expected for undegraded polymers. In the second phase, the FPP is reached and fractures are generated. In this phase, the polymer solution exhibits shear-thinning behaviour in the fractures. Owing to significantly lower flow velocities in the formation, degradation of the polymers is limited. Phase one is usually short in comparison to phase two.To achieve sufficient polymer solution injection rates for an economic project without degrading the polyacrylamide polymer, inducing fractures by injection is required for the reservoirs in the Vienna Basin. Hence, screening of fields has to include geomechanical properties of the reservoir sands and surrounding shales. Also, the risk of fracturing outside of the formation has to be assessed. In addition, the values of the FPP of the reservoir sands and surrounding shales and the direction of induced fractures should be determined. Furthermore, the injection water quality in terms of fines and oil content has an impact on the fracture growth and should be evaluated.