Assessing the Reusability of Legacy Wells for Ccs Projects: A Screening Framework, its Application and the Impact
10 Pages Posted: 9 Nov 2022
Date Written: November 9, 2022
Abstract
Existing oil and gas wells have the potential to be re-used for geologic CO2 storage to reach climate goals in the reduction of CO2 emissions while potentially reducing costs associated with well construction for CCS. Currently there are no standard approaches or public tools available to aid in the evaluation of well re-use potential for CO2 storage.
The REX-CO2 (Re-using Existing wells for CO2 storage operations) project, funded by the ACT (Accelerating CCS Technologies) program, has the overall objective to provide decision makers with mechanisms and information to evaluate the re-use potential of existing oil and gas wells. The project has developed an assessment framework translated into a standalone well integrity screening tool based on state-of-the-art practices, standards, guidelines and international reference projects. The framework was supported by technical and regulatory requirements, and experimental well integrity research. The tool is designed to utilize available data on well construction, subsurface geology and well operational history to screen the reusability of the existing wells for CO2 storage operations. Each well is screened against five categories: risk of out of zone injection, well integrity primary barrier envelope, well integrity secondary barrier envelope, structural integrity, and material compatibility. For each of these pillars, decision trees have been developed that guide the user through the assessment process. The tool provides a thorough qualitative evaluation of the current reusability potential of the wells using a color-coding system and highlights the most important integrity issues, which can be used to design and select mitigation options. The tool has been applied to ten international case studies with dozens of wells, covering a wide range of well designs and subsurface settings, with the overall goal to test and demonstrate the evaluation process.
The tool allows a fast, consistent and complete screening of a large portfolio of wells, aiding the identification of promising candidates for potential re-use in a CO2 storage project. Ultimately, learnings from the framework development and case studies were used to develop recommendations for re-using existing wells for CO2 storage.
Keywords: Well integrity, Well re-use assessment, Reusing existing oil and gas wells, Well screening tool
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