Since the early 1990’s scale inhibitor precipitation technology has been routinely used throughout the North Sea to provide improved placement and extended treatment lifetimes when compared to conventional aqueous-based scale inhibitor squeeze treatments. Controlled precipitation technology is based upon the deployment of a specially formulated scale inhibitor package containing an organic additive that breaks down thermally and acts as a pH modifier resulting in in-situ scale inhibitor precipitation. However, the reliance on thermal degradation of the organic additive to cause precipitation means that this technology is limited to use in wells at temperatures > 85°C.
This paper describes the development of a low temperature, scale inhibitor precipitation delivery system. The new system is based upon the use of novel enzyme technology to break down the pH modifier using a non-thermal mechanism, thus allowing product deployment at low temperatures previously unavailable to the thermal degradation systems. Laboratory studies have so far indicated that the enzyme is effective at inducing scale inhibitor precipitation at both 40°C and 80°C.
A description of the laboratory development and evaluation of the new enzyme precipitation technology including enzyme assay, full analysis of the precipitation mechanism and core flood studies to evaluate formation damage potential and retention and release characteristics will be presented.
This paper will also highlight how the use of the enzyme precipitation process can increase squeeze lifetimes when compared to traditional adsorption squeeze treatments at low temperatures.