A Deep Dive on Stage Cementing Operations in Sub-Saharan Africa: A Case Study

Abstract Cementing through weak sand and unconsolidated formations are a common occurrence in today's drilling operations. Main challenges include well control, poor zonal isolation, failed top of cement objectives that could lead to a shortened lifespan of wells. From annular gas migration through micro annulus to getting the top of cement to an undesired depth below referenced hydrocarbon sands, cementing through unconsolidated formations can lead to an increase in the cost of delivering a well. There are different methods deployed in cementing through unconsolidated zones. Stage cementing is one key method to ensure proper zonal isolation across formations with significantly loose sands and fault across a specified depth. With stage cementing, primary cementing can be performed in several stages to get annular cement slurry placement to specified depths without interfering with lost circulation depths. In addition to stage cementing, high performance lightweight slurry designs are common, and this is widely deployed through blending glass beads in the cement slurry designs which enables slurries achieve low density requirements without compromising compressive strength. Foam cementing is another method to lower density of slurry to aid placement in such cases. Stage cementing is not a common practice in the Sub-Saharan African region due to the lithological lay-up of formations around the region. This paper aims to perform an in-depth analysis on the design challenges, key planning consideration, materials requirement and the operational challenges that is often experienced while performing stage cementing. Different case studies of wells cemented using this method will be examined highlighting these key considerations. A breakdown will also be done on the economic models of deploying stage cementing as compared to other cementing solutions like lightweight slurry deployment. Stage cementing can provide a means to delivering cementing solutions to traditionally challenging environments in a cost-effective way which drives performance excellence.