Well-Integrity Assessment and Assurance: The Operational Approach for Three CO2-Storage Fields in Italy

Abstract

Summary In 2004 Eni Exploration and Production (E&P) launched the GreenHouse Gases (GHG) Project to develop technologies and select fields suitable for geological sequestration of carbon dioxide (CO2). For the well area, the project includes Well-integrity assessment: Verify and (if necessary) reinstate the structural integrity of the existing wells.Well-integrity assurance: Establish the technical requirements to ensure the integrity of new CO2-injection wells. Well-integrity assessment has been carried out by developing and implementing an operational methodology for three Italian fields: Cortemaggiore, Palino-Ascoli-Candela-Satriano (PACS), and Giaurone-Armatella-Gela. This methodology includes the comparison between the sustained casing pressures (SCPs) measured in the annuli and the relevant maximum allowable pressures (MAPs) to estimate how close each well is to losing its safety conditions. Then, the methodology foresees specific investigations for the critical wells to identify the magnitude and possible causes of the SCPs occurrence. Finally, it includes the preparation of suitable remedial and/or monitoring plans. Stress-analysis studies supported these activities by calculating the mechanical resistance, under the planned operational conditions, of production casings and tubings of the CO2-injection wells. As for well-integrity assurance, technical requirements for new CO2-injection wells have been established on the basis of the project for Well Cortemaggiore 157 Dir, constructed to carry out the pilot test for the injection of CO2 in a depleted level of the Cortemaggiore field. Specific studies have been carried out for the PACS and Giaurone-Armatella-Gela fields. The former is a gas field with high CO2 content—CO2 will be separated and reinjected. The latter is an oil field—CO2 injection will be used as an effective means for enhancing oil recovery. This paper describes the operational approach followed for these activities and describes the main requirements for the new CO2-injection well.