Improved Oversight Increases Service Quality for Deepwater Cementing Operations
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The continual increase in exploration drilling in southern Africa has translated into a number of remote deepwater campaigns, the most recent ones being in Namibia. One particular three-well campaign was exceptionally challenging as there was no near offset-well data available. The challenges were especially acute in the riserless tophole section.The well designs called for top of cement (TOC) at seabed for the surface casing. This was of the utmost importance for adequate structural and axial support for the blowout preventers (BOP) and subsequent casing strings. The very low fracture gradient near the seabed was the main challenge as the formations would not support the hydrostatic pressure of the cement column. On the first well, total losses were encountered prior to and during the entire cementing operation. As a result, no cement returns were observed at seabed, contrary to what was expected from hydraulic simulations and volume calculations and required to meet the job objective.To achieve objectives required for the success of the subsequent two wells, all aspects of drilling and cementing operations were reviewed based on the findings of the first well. Mud weight and casing setting depth were critically challenged, with other parameters adjusted. Cement formulation and density were optimized to reduce hydrostatic and hydrodynamic pressures and to increase the chance of success. The cement slurry was changed to a bimodal lightweight system with better fluid-and set-cement properties. Lost circulation fiber technology was also incorporated in the spacer preflush and in the cement slurry to mitigate any losses during placement.Alignment of service company and operator objectives and optimization of drilling and cementing parameters were critical for the successful cementation of these challenging tophole sections. Continuous improvements resulted in the second well being effectively cemented to seabed, even though intermittent losses were observed. After further optimization, the third well was cemented to seabed with full returns. Reaching the target TOC eliminated the need for a top-up job, saving valuable rig-time.
The continual increase in exploration drilling in southern Africa has translated into a number of remote deepwater campaigns, the most recent ones being in Namibia. One particular three-well campaign was exceptionally challenging as there was no near offset-well data available. The challenges were especially acute in the riserless tophole section.The well designs called for top of cement (TOC) at seabed for the surface casing. This was of the utmost importance for adequate structural and axial support for the blowout preventers (BOP) and subsequent casing strings. The very low fracture gradient near the seabed was the main challenge as the formations would not support the hydrostatic pressure of the cement column. On the first well, total losses were encountered prior to and during the entire cementing operation. As a result, no cement returns were observed at seabed, contrary to what was expected from hydraulic simulations and volume calculations and required to meet the job objective.To achieve objectives required for the success of the subsequent two wells, all aspects of drilling and cementing operations were reviewed based on the findings of the first well. Mud weight and casing setting depth were critically challenged, with other parameters adjusted. Cement formulation and density were optimized to reduce hydrostatic and hydrodynamic pressures and to increase the chance of success. The cement slurry was changed to a bimodal lightweight system with better fluid-and set-cement properties. Lost circulation fiber technology was also incorporated in the spacer preflush and in the cement slurry to mitigate any losses during placement.Alignment of service company and operator objectives and optimization of drilling and cementing parameters were critical for the successful cementation of these challenging tophole sections. Continuous improvements resulted in the second well being effectively cemented to seabed, even though intermittent losses were observed. After further optimization, the third well was cemented to seabed with full returns. Reaching the target TOC eliminated the need for a top-up job, saving valuable rig-time.
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.
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.
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