Assessing polyacrylamide solution chemical stability during a polymer flood in the Kalamkas field, Western Kazakhstan

Abstract

During a polymer flood, the field operator must be convinced that significant chemical investment is not compromised at the early stages of polymer injection. Further, dissolved oxygen in the viscous polymer solution must be controlled at a safe level, where viscosity loss will be insignificant. Under anaerobic conditions, the hydrolyzed polyacrylamide (HPAM) solution is stable even if iron ions are present in the process water. Thus, in the field operation, introduced oxygen and existing iron ions will cause an enormous viscosity decline. The geochemical calculation reveals that dissolved oxygen can rapidly deplete after entering Kalamkas formation. This paper confirms this prediction through a combination of laboratory measurements and field observations. This study is based on rheology measurements of polymer solutions and produced fluid from the offset production well associated with the Kalamkas oilfield in Western Kazakhstan. Comprehensive analysis confirms no viscosity loss at the surface facilities during polymer preparation and injection at a Polymer Slicing Unit and significant viscosity loss at an Eductor-type unit caused by oxygen introduced during polymer solution preparation. However, even introduced high dissolved oxygen levels that degrade polymer at the surface can be rapidly depleted during contact with the formation, thereby promoting polymer chemical stability in the reservoir.