Offshore cementing poses many challenges across the world as drilling oper ations move towards deep-water and ultra -deep-water. As a new initiative of continuous improvement, a deep-water cementing peer review process was started early 2011. To this date, th is team has reviewed more than 12 00 deep-water cementing jobs in more than 30 countries worldwide.

Cementation of wells, especially in deepwater has attracted a great deal of attention after recent loss of well control events and subsequent changes in regulatory requirements with respect to achieving effective zonal isolation, preventing the release of wellbore fluids to the environment and avoiding the need for cement job remediation[1, 2]. Deepwater well construction presents unique challenges for proper cementation. These challenges are driven by the greater complexity of deepwater (DW) wells. There is; narrower pore pressure (PP) and fracture gradient (FG) margin, use of oil based mud (OBM) or synthetic based mud (SBM) drilling fluid that is incompatible with water based cement slurries, additional length for the cementing fluids to travel due to the sea water depth increasing the risk of intermixing between fluids, technology pushed to the limit, and the cost of drilling in deepwater that is much higher than conventional wells. Currently there are two main flow regimes used when planning for effective mud removal and cement placement: effective turbulent flow and effective laminar flow. Turbulent flow is generally considered the preferred method of efficiently removing fluids; however there are a number of requirements to be met in order for turbulent flow to be both safe and effective. Laminar flow is the most widely used due to the ease of placement design and the lower annular velocities required to achieve effective cement placement. Drilling fluids, weighted spacers and cement slurries can all be designed in effective laminar flow, since they exhibit a yield stress. Brines, water, and chemical washes are typically designed in effective turbulent flow. In this paper the authors will discuss the factors to be taken into account when designing cement jobs using fluids in turbulent flow and some of the overlooked benefits of using turbulent flow design for mud removal. Case histories from DW wells cemented in the Gulf of Mexico region and risk factors will be discussed. It will be demonstrated that when designed and executed properly, the use of turbulent flow mud removal with Newtonian fluids can be beneficial in DW cementing operations.

Deepwater cementing poses many challenges across the world as drilling operations move towards greater water depths. The Deepwater Cementing Review Team (SPE WVS 035), gathered to provide oversight to the deepwater cementing job programs within the corporation and to insure they meet the industry standards, has reviewed so far more than 1200 jobs spread over 30 countries worldwide. About 10% of the reviewed jobs are riser-less surface casing cement jobs. When present, shallow flow is one of the biggest risks in cementing surface casings. Not achieving zonal isolation can result in the loss of the well or expensive remedial work. Early identification of potential shallow flow is crucial as it gives time to optimize the cement job following industry best practices, such as API RP 65 and API ST 65 – Part 2. Three important factors for a successful cement job in case of shallow flow are proper centralization, good mud removal and slurry selection. If shallow flow is present, the surface casing must be properly centralized to achieve flow around the entire casing. Conventional cement systems are widely and successfully used for surface casings. However, if shallow flow is identified, more advanced cement systems, such as foam cement or optimized particle-size distribution cement, are used. Zonal isolation of shallow flow zones can be obtained through cementation when the engineering guidelines are followed and focus is placed on proper design and execution. A statistical analysis of the surface casing designs reviewed shows the risk of shallow gas and demonstrates that shallow flow can be prevented, after the flow potential is identified. The key is early identification of shallow flow and open discussion between the operator and the service company.

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The deepwater drilling industry continues to require increased oversight of cementing programs and cement operations. A deepwater cementing technical specialist team was created to provide reviews and oversight of deepwater cement programs worldwide. Deepwater cementing specialists were selected from within the organization and the initiative was introduced to operations in the first quarter of 2011. The team provides an additional level of peer review of all deepwater cementing programs. The purpose of the peer review is to support the engineer's program design and to verify that the program is in compliance with internal standards, client standards, and applicable regulatory requirements. If required, the team will act as a liaison for the operations personnel and additional experts on critical jobs. The reviews are documented so that all communication can easily be tracked.The main objective of the team is to provide a proactive approach to identify risks early in the design phase and elevate the risks to the appropriate levels of management so that appropriate actions can be taken. The goal is to review all deepwater cement programs before submitting the final procedures for operations.Sharing worldwide knowledge and adding to the worldwide knowledge base is necessary as new challenges are faced while drilling and cementing offshore wells in deep and ultradeep waters. Risks and potential hazards may be recognized long before the job execution-giving sufficient time to change, improve, and enhance the cementing design. Several examples are given for job designs that have been improved prior to execution. As a result of this initiative, a continuous improvement of job procedures is being observed worldwide, resulting in designs with a higher likelihood of achieving the job objectives, and avoiding unnecessary, costly remedial work.