Carbon Capture Storage (CCS) Drilling & Completion Well Integrity Lifecycle Challenges & Mitigations

Abstract

Abstract The growing global awareness of international climate change has compelled the global industry to take responsibility for reducing greenhouse gas emissions. As part of an Oil and Gas Operator's strategy to address this issue, a roadmap has been developed to capture and store carbon dioxide (CCS). This paper provides insights into CCS projects that employ a Storage Development Plan (SDP), which involves separation of CO2 from existing oil and gas producing fields with high CO2 content, and then reinjecting it into reservoirs with essential caprock geological seals for containment. Injector wells, either newly drilled or retro-fitted from existing fields, will be utilized to inject and store the produced CO2. Ensuring the integrity of all wells is crucial for preventing CO2 leakage and ensuring long-term containment sustainability along the wellpath, including both existing Plug and Abandonment (P&A) wells and active ones that intersect the chosen CO2 storage reservoir, as illustrated in Figure 1 The development wells within the identified depleted gas field have exceeded 30 years in age and were originally designed without considering the presence of high CO2 concentrations in the reservoir. The possibility of leakage along the wellbores due to accelerated corrosion, channeling, and cracks cannot be overlooked and necessitates thorough evaluation. A meticulous process has been implemented to assess the viability of converting existing producers into CO2 injectors. Discrepancies between the prescribed designs for gas production wells and CO2 injection wells dictate whether they can be repurposed for CO2 injection or need to be decommissioned. The determination of the optimal number of required CO2 injectors involves a screening process from fat to slim design approaches, utilizing corrosion-resistant alloy (CRA) materials and CO2-resistant cement to ensure lifecycle integrity. Maintaining an optimum angle between 40 to 60 degrees and sustaining the necessary injection pressure at the required rate for injecting supercritical CO2 over a 25-year period are critical considerations. Additionally, challenges during well execution, such as anti-collision risks and total loss scenarios while drilling in carbonate reservoirs, must be addressed. Completion design focuses on minimizing the number of completion components to reduce pressure differentials and potential leak paths from the tubing hanger down to the lower completion's end. Well design optimization from fat to slim has been conducted based on sensitivity analysis outputs from Software. Monitoring the well integrity lifecycle involves utilizing the latest-generation fiber optic technology for in-country value as well as acquiring seismic data for CO2 plume development.