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

Abstract

Abstract In 2004 Eni E&P launched the "GHG (GreenHouse Gases) Project" to develop technologies and select fields suitable for geological sequestration of CO2. For the well area, such project has implied: 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, PACS (Palino-Ascoli-Candela-Satriano) and Giaurone-Armatella-Gela. Such methodology includes the comparison between the Sustained Casing Pressures (SCP's) measured in the annuli and the relevant Maximum Allowable Pressures (MAP's) to estimate how much each well is close to lose its safety conditions. Then, the methodology foresees specific investigations for the critical wells to identify the magnitude and possible causes of the SCP's occurrence. Finally, it includes the preparation of suitable remedial and/or monitoring plans. Stress Analysis studies supported the above activities by calculating the mechanical resistance, under the planned operational conditions, of production casings and tubings of the CO2 injection wells. As far as Well Integrity Assurance, technical requirements for new CO2 injection wells have been established based on the project for the 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 re-injected; 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 the above mentioned activities and the main requirements for the new CO2 injection well.