Abstract
Alkaline surfactant polymer (ASP) floods often induce silicate scaling. Scaling of the production tubing, rod pumps and other surface equipment causes frequent workovers, resulting in increased costs and non-productive time. High treatment rates and short run times drove the re-evaluation of the problem in pursuit of more targeted products and applications. The formation of silicate scale is complicated by its dependence on multiple water chemistry-dependent factors which vary as the flood progresses (Gill 1998). These factors affect silicate scaling tendency, and consequently, severity of the problem. A range of silicate scale inhibitors has been developed to mitigate problems in oilfields afflicted with silicate scaling due to ASP flooding (Qing et al. 2002). A new test method using an optical scanning device was developed to better characterize inhibition and dispersant qualities of inhibitors on silicate scale in solution under static conditions. The advantage of this method is more comprehensive data generated by multiple-point measurements. Scaling reactions are more easily modified and differentiated. Water chemistries from several wells in an ASP-flooded field in Southern Alberta with known silicate scaling issues defined the tested synthetic brine. By allowing the mixed synthetic brine to react before adding inhibitor, the effect of delayed chemical injection may be studied. Performance of the tested inhibitor was significantly reduced by slight injection delay and may account for the discrepancy often seen between laboratory performance data and failures observed in the field. It is proposed that the performance of silicate scale inhibitors may be improved when applied by squeeze, where the inhibitor can inhibit silica polymerization within the formation and may provide substantial improvement over conventional continuous down-hole injection. Test work done to confirm the feasibility of the squeeze included fluid compatibility and core damage studies. These performance tests demonstrated the treating advantages of a scale inhibitor squeeze.
