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Harbour Energy began offshore exploration in the Andaman Sea in North Sumatra, Indonesia with the Timpan-1 well. During the planning phase, reservoir sections of the well were identified that contained circa 5-15% of CO2 levels as per the offset well data, which are corrosive environments and can cause cement sheath degradation. This paper presents the decision process used in selecting a suitable system for the CO2-rich environment and the first-time application of pumping novel self-healing and CO2-resistant cementing system with its capability to self-heal upon contact with CO2. Conventional Portland cement degrades in CO2-corrosive environments and combined with cement sheath damage by downhole stresses, long-term well integrity will be compromised. The auto repair capabilities provided by the novel cement system when in contact with CO2 leaking-fluids ensure long-term well integrity. Although self-healing-to-hydrocarbons cements have been widely used in the industry, use of this newly developed novel self-healing CO2-resistant cement was implemented for the first time in a primary casing job. To ensure blend consistency of the novel self-healing CO2-resistant cement, a number of quality control processes were developed with extensive laboratory testing and implemented for the complete blend lifecycle management. Implementation of this novel self-healing CO2-resistant cement in a deep-water primary casing job requires validation of crucial factors meet the requirements of achieving the long term well integrity. During the preparation phase, this cementing system was exposed to a high-CO2 corrosive environment over an extended period to analyze the robustness. The results showed superior properties compared with a conventional Portland system. The self-healing properties, analyzed with the use of an actual crack in the set cement and observed to the point where the crack closed, demonstrated continued cement integrity. Slurry stability tests produced excellent results. Blend flowability and robustness tests were performed at a regional laboratory using specialized equipment and determined the blend to be suitable for offshore operations. In implementation phase, by adhering to the project management process developed, the primary casing cement job was successfully performed without incident using conventional cementing equipment and practices. Good cement bond was obtained across the main zone, and the rig was able to continue its operations to perforate and well test the well. The 2001 Greenhouse Gas (GHG) Protocol's guidelines categorized business GHGs as scope 1 emissions, scope 2 emissions, and scope 3 emissions. The aim of this emission classification system was to help organizations measure and manage their carbon footprint (www.greenbusinessbureau.com 2022). Scope 1 emissions are GHGs released directly from a business. Scope 2 emissions are indirect GHGs released from the energy purchased by an organization. Scope 3 emissions are also indirect GHG emissions, accounting for upstream and downstream emissions from a product or service, and emissions across a business's supply chain. The novel self-healing CO2-resistant cement produces 63% less CO2 compared with a conventional Portland cement system. Implementing the novel slurry system will significantly reduce Scope 3 of CO2 emission that is embedded during the manufacturing of the materials used. In addition to that, due to its self-healing capability, the novel CO2-resistant cement will contribute on Scope 1 CO2 emission reduction by eliminating the need to perform remedial work in case of a well leak. The solution meets the long-term well integrity requirement and is in line with the global commitment to reduce the carbon emission footprint.
Harbour Energy began offshore exploration in the Andaman Sea in North Sumatra, Indonesia with the Timpan-1 well. During the planning phase, reservoir sections of the well were identified that contained circa 5-15% of CO2 levels as per the offset well data, which are corrosive environments and can cause cement sheath degradation. This paper presents the decision process used in selecting a suitable system for the CO2-rich environment and the first-time application of pumping novel self-healing and CO2-resistant cementing system with its capability to self-heal upon contact with CO2. Conventional Portland cement degrades in CO2-corrosive environments and combined with cement sheath damage by downhole stresses, long-term well integrity will be compromised. The auto repair capabilities provided by the novel cement system when in contact with CO2 leaking-fluids ensure long-term well integrity. Although self-healing-to-hydrocarbons cements have been widely used in the industry, use of this newly developed novel self-healing CO2-resistant cement was implemented for the first time in a primary casing job. To ensure blend consistency of the novel self-healing CO2-resistant cement, a number of quality control processes were developed with extensive laboratory testing and implemented for the complete blend lifecycle management. Implementation of this novel self-healing CO2-resistant cement in a deep-water primary casing job requires validation of crucial factors meet the requirements of achieving the long term well integrity. During the preparation phase, this cementing system was exposed to a high-CO2 corrosive environment over an extended period to analyze the robustness. The results showed superior properties compared with a conventional Portland system. The self-healing properties, analyzed with the use of an actual crack in the set cement and observed to the point where the crack closed, demonstrated continued cement integrity. Slurry stability tests produced excellent results. Blend flowability and robustness tests were performed at a regional laboratory using specialized equipment and determined the blend to be suitable for offshore operations. In implementation phase, by adhering to the project management process developed, the primary casing cement job was successfully performed without incident using conventional cementing equipment and practices. Good cement bond was obtained across the main zone, and the rig was able to continue its operations to perforate and well test the well. The 2001 Greenhouse Gas (GHG) Protocol's guidelines categorized business GHGs as scope 1 emissions, scope 2 emissions, and scope 3 emissions. The aim of this emission classification system was to help organizations measure and manage their carbon footprint (www.greenbusinessbureau.com 2022). Scope 1 emissions are GHGs released directly from a business. Scope 2 emissions are indirect GHGs released from the energy purchased by an organization. Scope 3 emissions are also indirect GHG emissions, accounting for upstream and downstream emissions from a product or service, and emissions across a business's supply chain. The novel self-healing CO2-resistant cement produces 63% less CO2 compared with a conventional Portland cement system. Implementing the novel slurry system will significantly reduce Scope 3 of CO2 emission that is embedded during the manufacturing of the materials used. In addition to that, due to its self-healing capability, the novel CO2-resistant cement will contribute on Scope 1 CO2 emission reduction by eliminating the need to perform remedial work in case of a well leak. The solution meets the long-term well integrity requirement and is in line with the global commitment to reduce the carbon emission footprint.
In CO2 storage sites, wells located within the predicted area of review, and that penetrate the confining zone, may become a leakage pathway out of the injection zone if not properly abandoned. Prior to injection, the abandonment focus is on existing (legacy) wells. After injection has concluded, the focus will expand to include storage development wells, e.g., injector and monitoring wells. Unlike oil and gas developments, where formation fluids are produced, Carbon Capture and Sequestration (CCS) projects inject CO2 into downhole formations, creating a plume that must be contained within the target reservoirs for periods of time that are longer than oil and gas wells’ life span. These differences make it necessary to develop CCS-specific well abandonment practices. The authors have analyzed industry-accepted well abandonment standards, abandonment recommendations and requirements from regulators for CCS projects, and several case studies and laboratory experiments on well integrity to develop an understanding of the challenges and probable solutions for CCS well abandonment. Then, a recommended practice for well abandonment in CO2 storage sites that addresses isolation of the confining and reservoir zones, the effects of a CO2-rich environment on well materials, and corrective action for legacy wells will be presented. Most of the existing regulations and standards on CCS establish expectations and objectives for well abandonment without providing detailed guidelines that can be consistently applied across projects. Without consistent rules for CCS well abandonment, project teams will conduct design or planning exercises that will have varying outcomes as they adapt conventional well abandonment guidelines to CO2 storage site requirements. This may result in under- or over-designing the well abandonment; which could translate into compromised well integrity, impact on project value; and an ever-changing technical standpoint. The aim of a recommended practice is to establish simple high-level principles with which to approach well abandonment in CO2 storage sites to facilitate the work of project teams and to have an acceptable level of consistency on abandonment plans. This paper will demonstrate a comprehensive abandonment strategy for CCS and legacy wells. The strategy addresses CCS-related containment concerns and local applicable abandonment regulations for all other sources of inflow not related to CCS. It discusses how the ability of a confining zone to stop the flux of CO2 through it, that depends on its permeability, thickness and capillary pressure; is relevant for establishing CCS abandonment principles.
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.
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