Well barriers are an important factor during the life of a well. As cementing is involved in many of those well barriers, there is considerable focus in the oil field on the design, execution, and validation of the cement as a well barrier. It is important that the cement job design begins at the same time as the basic well design, especially in deepwater operations. Decisions made early in the well design can have a tremendous effect on the cement job execution. Early in the well design, the cement job objectives are set, and through simulations, the cement job placement, slurry design, and, in some cases, well design, are optimized to overcome any identified challenges and minimize risks during cement placement. Cement equipment is becoming increasingly more sophisticated and cement job designs more critical; additional attention needs to be placed on the cementing job preparation on location prior to the actual cement job. By using the latest advances in communications, it is easier for the offshore cementing specialists to stay in contact with the shore-based staff; not only with the design engineer, but also the maintenance manager or operation support staff. Improved monitoring and automation during the job execution enhances the process control. Advances in real-time capabilities enable the onshore experts to monitor the offshore operations and provide advice during the execution of the cement job itself. The final step of a cement job is the evaluation phase. A cement job evaluation is more than just a pressure leak-off test or running a cement evaluation log. The evaluation procedure of a cement job ties together all the parameters of the job, including the job objectives, drilling parameters, job execution, and post-job test results. Looking at one parameter only will often not provide a complete analysis and evaluation. Because cementing provides critically needed well barriers, it becomes a very important aspect in well integrity management during the life of the well.
The operator was drilling their first high-pressure high-temperature (HPHT) exploration well with narrow pressure window in a swamp area of East Kalimantan. The gas field was discovered in 1977 and production started in 1990. Since then, more than 1500 wells have been drilled in this area yielding a total gas production of 9.7 Tcf. Currently T field enters established mature field status which has quite marginal reserves. Therefore, further exploration is seen as one of the solutions to locate additional reserves to enhance overall gas production. The well was drilled directionally with no offset well nearby. While drilling the 6-in open hole section, an unexpected high-pressure zone was penetrated. The zone condition was made worse by lost circulation and a high gas reading. Two cement plugs were placed using a managed pressure cementing with pump and pull method. The first plug was set by applying surface back pressure (SBP) to maintain equivalent bottom hole pressure (BHP) between lowermost pore pressure (PP) and fracture gradient (FG) at the previous shoe. After pumping 1 m3 of cement into the annulus, pump and pull operations commenced. While performing post job circulation on the first plug, it was observed that the returned fluid density at surface was less than original mud weight, indicating the possibility of contaminant invasion from formation. After waiting for the cement to reach 500 psi compressive strength, pressure buildup was observed when annulus was shut-in, indicating an inadequate pressure seal across the cement plug Applying lessons learned from setting the first plug, new design considerations were implemented such as increasing cement volume in the annulus to 4 m3 prior to the pump and pull operation to minimize cement overlapping risk and applying SBP at BHP near FG. A contingency plan was in place to determine the appropriate SBP value to be applied whenever the pumping rate was changed. A second plug job was performed safely and flawlessly by achieving the top of cement as desired. A successful inflow test was performed with indication of no contaminant invasion nor pressure bypass around the cement plug. The rig was able to continue its next operation to sidetrack the well. This paper presents the design considerations, methodology applied, and lessons learned two managed pressure cement plugs using pump and pull method in a well bore with a narrow pore-frac window where the new techniques were implemented to enhance success of the plug job despite the complexity and risk inherent with an underbalanced operation.
Disclaimer: This paper includes forward-looking statements, Actual future conditions... The publication of the API Standard 65-2 "Isolating Potential Flow Zones During Well Construction" places strong emphasis on measuring the Critical Gel Strength Period (CGSP). The CGSP is the time period starting from when laboratory measurements indicate the slurry has developed Critical Static Gel Strength (CSGS), to when it has developed strength of 500 lbf/100ft2. As per the API standard, CGSP of 45 minutes or less has proven effective in isolating zones with severe flow potential therefore, the CGSP has been identified as a crucial parameter to qualify slurry systems for many oil and gas operators. The API 10B-6 "Recommended Practice on Determining the Static Gel Strength of Cement Formulations" indicates there are three measurement methods; continuous rotation, intermittent rotation, and ultrasonic-type static gel strength. This paper will review a comparative laboratory- based study between two measurement devices commonly used in the industry to measure the CGSP. One device uses the intermittent rotation, and the other uses the ultrasonic method. The slurry systems selected for the study covers a density range of 11.5 to 18 lbm/galUS within the temperature range of 27 to 121 deg C. The selected slurries comprise of Class G cement, silica flour with extenders or weighting agents paired with antifoam, fluid loss additives, dispersant and retarder to represent the typical slurry systems used in cementation of potential flow zones. Additionally, each slurry system is designed for two scenarios; one is to cover a short placement time(3 to 4 hours) and the other for a longer placement time (7 to 8 hours). While some of the slurry systems passed the CGSP criteria based on the ultrasonic method of measurement, they did not pass the criteria when measured by the intermittent rotation method. Possible reasons for this mismatch are further explained in this paper. Results of this study are applicable to all oil and gas service operators involved in cementation of potential flow zones. One would expect that both of these methods would predict the same slurry behavior in either passing or failing the CGSP criteria, however and on the contrary that was not observed on all of the slurry systems selected for this study.
The operational and technical complexity of cementing operations has increased with deepwater exploration entering frontier regions on a global scale. An efficient knowledge management system (KMS) plays a vital role in providing a flow of information, and it helps in applying the findings of one area and to another area. This paper elaborates how a major service company has increased the service quality of deepwater cementing operations by using a KMS.All the knowledge, information, and experience from a cementing operation can be uploaded by field personnel in the form of lessons learned best practices, case studies, and more. Each knowledge-content related to deepwater cementing is reviewed by a dedicated team of subject matter experts (SMEs). After the content is validated by the SME, it can be accessed by the employees in diverse locations to improve their local operations. The information is maintained in the system until it is obsolete, which allows effective knowledge sharing even after the experienced employees have moved on to other assignments or are geographically far from the operating location. Different engineers working around the clock update the KMS and provide support to the field and operational staff.A key advantage of the KMS is that it promotes continuous improvement and standardization of the deepwater operation methodologies, including processes, reports, documentation, and more. The KMS also provides interactive training material such as deepwater cementing manuals, descriptions of special cement systems, and guides for troubleshooting the cement unit. The software application that runs the KMS is intuitive, and easy to use. The paper uses case study to highlight how the KMS has helped in planning for the technical and operational complexity of deepwater cementing operations in different regions around the globe.
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.