Scale Control and Inhibitor Evaluation of an Alkaline Surfactant Polymer Flood

Abstract

Abstract Scale control during Alkaline Surfactant Polymer flooding can be challenging1,2,3 The effective performance of scale inhibitors is a problem, given the high oversaturation expected due to mixing of injected alkali and formation water. Moreover, ASP creates a high pH condition in the reservoir and at production wells. Selecting an effective inhibitor and achieving a long return profile following scale inhibitor squeeze treatment under these conditions can be difficult. This paper describes the studies performed to address the scale management issues for a field where ASP flooding is planned. Scale prediction was carried out and a list of scale inhibitors was screened through performance testing. A number of ASP-specific factors were taken into account for the modeling and testing, including the injected and expected produced chemical concentration, salinity change and chemical compatibility. The results have shown that under these particular field conditions, a conventional penta-phosphonate can provide effective scale control in this field during ASP flooding. Initial core floods indicated that long squeeze life time can be achieved, but the application of the inhibitor in a typical acid form resulted in severe formation damage. A non-damaging formulation was designed by adjusting the inhibitor concentration and partially neutralizing the inhibitor package. The final testing results of the designed inhibitor package show that an effective scale inhibitor squeeze can be attained in the production wells during ASP flooding. More significantly the work demonstrated that the composition of the produced water (% of ASP injection water) producing from a particular zone has a dramatic impact on the potential squeeze lifetimes.