Identifying and Mitigating the Risks of Shallow Flow in Deepwater Cementing Operations

Abstract

Abstract 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.