Specialized Carbon Dioxide Self-Healing Cement System Engineered for Carbon Capture and Storage Well in Norwegian Continental Shelf

Abstract

Abstract In recent years, the energy sector has experienced a noticeable shift in focus away from traditional oil and gas activities, diversifying into activities related to sustainability. One such activity is carbon capture and storage (CCS). In this paper we explore such activities with specific focus on the installed primary well barrier element, i.e., the cement sheath, including application, and performance as such in a dynamically stressed carbon dioxide (CO2) environment. It is well known that under certain conditions, Portland cement can be adversely affected by CO2, although the impact on set cement will vary with conditions such as fluid salinity, temperature, pressure, and permeability of the set material. Based on several years of concept evolution, a specialized cement system has been developed that not only has intrinsic resistance to CO2 degradation but adds the functionality of self-healing. In this context, small microfractures or microannuli may be sealed over time when the cement system is exposed to CO2. This system was qualified following extensive CO2 exposure where the mechanical properties were assessed before and after testing. This step was added to ensure the set cement maintained integrity over time, including during pressure and temperature changes/cycles during CO2 injection. Following consultation and close collaboration with the operator, the design of the self-healing CO2 resistant cement system was accepted with optimal results, based on field conditions. The results of the final design will be presented in this paper, including those related to the iterations necessary to tailor the required mechanical properties to prevent failure caused by stress-related cracking. The self-healing action will also be presented. Upon implementation in the field, the specialized CO2 self-healing cement system was transported offshore and handled at the rig with no unforeseen challenges. This bolstered the practice of conducting a thorough prejob risk assessment. A detailed operational program was prepared, permitting the cement slurry to be mixed and placed without incident. From a post-job perspective, validation of the annular barrier is crucial, so wireline cement bond logging was conducted. The log outcome exceeded the minimum criteria for a barrier as dictated by the latest NORSOK D-010 (2021) requirements. We present the first-ever implementation of a newly developed self-healing CO2 resistant cement system in the Norwegian Continental Shelf (NCS). As the industry places more emphasis on constructing wells or repurposing existing wells, the availability and application of this type of technology becomes more important. The importance increases as the industry seeks to achieve global sustainability goals. Establishing long-term wellbore integrity and maintaining the stored CO2 in the formation for perpetuity is paramount in achieving these challenging objectives.