In recent years, increased attention has been given to alternative barrier materials for oil and gas wells. Regulatory bodies across the globe are entertaining discussions on how alternative materials to cement, like that of epoxy resin, could (or should) be incorporated into well construction and late life abandonment as an opportunity to enhance barrier integrity.
ControlSEAL resin starts with a base epoxy resin, similar to those used in the oil and gas industry since the 1960’s. Then, performance enhancing additives and specialty activators are used to create a long-term barrier material for challenging well interventions, integrity recovery, and final well abandonment. Throughout the development of Wild Well’s ControlSEAL, engineers evaluated each critical property an epoxy resin needed to be a permanent barrier material for oil and gas application. Properties were identified and then properly optimized. The result is an enhanced epoxy resin design with several innovative patents that allow ControlSEAL to form a reliable long-term barrier under extreme well conditions.
Epoxy resins have been the most promising alternative barrier material with most regulatory bodies currently providing the necessary approval to use them as cement replacement for well abandonments. Epoxy resins start as liquids at surface and undergo a thermodynamically driven reaction in which long-chain hydrocarbon based epoxy polymers are tied together by a hardener component in a crosslinked network to form a single solid structure that can form a long-term barrier in oil and gas wells. This process is not different in nature to how most thermosetting plastics react in which epoxy resins are a specific category. However, it should be noted that the options are vast even for the specific category of epoxy resin and the type of base epoxy resin. Enhancement additives and activator component can have significant effects on each epoxy resin’s ability to be a long-term barrier. Barrier materials for oil and gas wells will experience extreme temperatures, high pressures, and corrosive fluids all while needing to withstand substantial differential pressures. These requirements make epoxy resins an obvious alternative to cement due to the reacted epoxy resin’s seemingly unlimited strength, resiliently, and intrinsic resistance to chemical attack. However, understanding the potential design variations and how they can significantly impact the epoxy resin’s performance as a barrier, several critical properties must be considered to create an epoxy resin that will successfully create a long term barrier.
As an epoxy resin, ControlSEAL was engineered with critical properties in mind to be optimized for downhole isolation. Shrinkage is just one example of a critical property that must be controlled in order for an epoxy resin to provide isolation. Laboratory analysis and large scale testing identified that the total shrinkage is a combination of both thermal contraction due to the exothermic resin reaction and chemical shrinkage due to the crosslinking process. In addition, to uncovering the two causes for shrinkage, it was found that debonding, the consequence of excess shrinkage, was mitigated with epoxy resins with high adhesion. This developed a complex relationship between adhesion, temperature increase from the exothermic reaction, chemical shrinkage, and bond, which must be controlled for ControlSEAL to provide isolation. To optimize this relationship, a test cell with temperature/pressure control was modified to specifically evaluate the presence and severity of shrinkage. Shrinkage was only measured following the initial moment of adhesion as shrinkage that occurs prior to adhesion could not contribute to debonding. Unsurprisingly at this point, designs with the fastest reaction rates experienced the highest critical volumetric shrinkage, hence increased vulnerability to debonding. A correlation can now exist as to not only the level of acceptable shrinkage needed to mitigate debonding, but a time threshold to which that shrinkage may occur.
ControlSEAL maintains long-term durability using nonshrinking, noncorrosive, and impermeable design. With all of the known benefits of epoxy resins, ControlSEAL has specifically been engineered for challenging well interventions, integrity recovery, and final well abandonment. It has the properties needed to create downhole barriers. The unique fluid and mechanical properties of ControlSEAL provide access, adhesion, and high differential barrier construction in the most difficult, hard to reach well treatments.
Read the article online at: https://www.oilfieldtechnology.com/product-news/25092019/controlseal-a-long-term-barrier-resin-sealant/