Abstract
In recent years, the use of polymer resins in oil and gas well cementing operations has increased. Unlike cement, resins do not have wide spread, vast case histories spanning 100 years, which leads to questions about their lifespan. The degradation kinetics of a commercially available oilfield resin system was studied and modeled to predict resin system lifetime as a function of temperature. Chemical degradation was monitored above the glass transition temperature using isothermal thermogravimetric analysis (TGA). The rate of weight change as a function of temperature was used to determine the reaction rate constant at various temperatures. This information was used to determine the activation energy and pre-exponential constant. These important parameters were then used to model the degradation reaction using an Arrhenius equation to predict the material lifetime as a function of service temperature. For selected resin systems, the degradation kinetics data were also collected at elevated pressure. The rate of weight loss strongly increased with increasing temperature; however, in experiments where pressure was applied under isothermal conditions, this rate was observed to be reduced. The degradation process was observed to follow a first order rate law. Comparing calculated rate constants to experimentally obtained rate constants yielded good correlation. The formulation of the resin system as well as component selection was observed to have a significant effect on material lifetime at downhole temperatures. The glass transition temperature of the resin system was not determined to directly correlate with degradation kinetics, and in some cases, increasing the glass transition temperature was not determined to increase the lifetime of the resin system at the temperature range evaluated.
This work provides an experimental outline for the necessary data collection and evaluation techniques to predict the lifetime of various resin systems at downhole temperature conditions using classical chemical kinetic equations. This allows the service company and operator to determine under what conditions and applications usage of resin systems is appropriate.
