FY 2024 Phase II Release I DE-FOA-0003184 CFDA: 81.049 C55-13 Advanced Subsurface Energy Technologies, Title: Nanomodified Polymers for the Long-Term Repair and Remediation of CO2 Wellbores

Wellbores that intersect CO2 storage formations represent a potential leakage pathway that can lead to subsurface migration of stored CO2 and/or subsequent venting of stored CO2 to the surface; consequently, repair and remediation of these wellbores is critical for ensuring the permanent storage of CO2 in geologic formations. Repair and remediation operations are particularly challenging for these wellbores because of the range of types and conditions of wells, the widely varying leakage pathways encountered, the harsh environmental conditions that degrade most conventional materials, and the need to be effective for a very long time. A system is being proposed to repair and remediate wellbores associated with CO2 storage facilities. The cornerstone of the proposed system is an extremely durable nano-modified polymer that will penetrate and seal very small but problematic leakage pathways as well as bond to and protect steel casing. In Phase I, the polymer formulation was modified to decrease its viscosity and extend its gel time to enable its utility for repair and remediation operations for wells associated with CO2 storage facilities. Using this polymer, a polymer-modified cement with superior durability, flexibility, and improved cracking strength was also developed to replace conventional oil-well cement in repair and remediation operations. In addition, the technical feasibility of an alternative delivery system for the polymer sealant using environmentally sensitive microcapsules was established in Phase I. This delivery system can be used to engineer effective repair and remediation applications. In Phase II, the nano-modified polymer and polymer-modified cement formulations will be refined to improve targeted properties and performance. These materials will be subjected to application-specific testing based on field experiences and accelerated longevity testing under extreme environmental conditions. We will also demonstrate the efficacy of the new materials with conventional field operations. The microcapsules will be optimized and their fabrication process will be scaled up to a commercial scale. The system will be available to be deployed in the increasing number of CO2 sequestration demonstration wells, pilot operations, and commercial projects throughout the US and the world. Many wells will be associated with these facilities as many potential locations have numerous wellbores from previous oil and gas production ľ so-called legacy wells. It is in the best interest of the public and owners/operators of these wells to use a repair and remediation system that has been developed specifically to meet the specific challenges of these wells.