Encapsulated Scale Inhibitor for Use in Fracturing Treatments

Abstract

Abstract This paper describes the development and testing of a solid, encapsulated scale inhibitor for use in fracturing treatments. Data from laboratory and field tests are reported. Laboratory testing with a continuous flow apparatus has yielded inhibitor release rates under dynamic conditions. The inhibitor was tested to determine the minimum inhibitor concentration required to inhibit the formation of CaCO3, CaSO4, and BaSO4 scales in brine. Laboratory data were used to determine the parameters of a mathematical model to predict the long-term release rate of the inhibitor. Data from a treated well are compared with predictions of the model. Release-rate testing in a continuous-flow apparatus shows that an encapsulated solid derivative of a phosphonate inhibitor has a sustained release profile. Temperature (100° to 225°F) and brine strength have a small effect on the release-rate profile. Coating the solid derivative makes it compatible with metal-crosslinked fracturing fluids. The coating has a short-term effect on the release-rate profile. The composition of the solid derivative has the greatest effect on its long-term release-rate profile. A comparison between the mathematical model proposed to describe the long-term release rate of the inhibitor and actual data collected from a treated well shows a large discrepancy, likely because most of the inhibitor is not in contact with the water being produced from this well.