An Innovative Approach to Successful Cement Plug Placement in Harsh and Deep Complicated Environments—A Mexican Case Study

Abstract Proper design and planning are crucial when placing a cement plug, especially when coordinating multiple teams. Achieving the desired plug properties hinges on the slurry design, but equally important is maintaining the slurry’s integrity during placement to ensure its purity at its final position. To prevent interface interaction and safeguard the slurry, mechanical separators like darts can be used at significant depths. This approach allows for reduced cement slurry volumes and minimizes contamination from non-cementing fluids such as spacers or mud. Consequently, the slurry remains intact and fulfills its intended objectives upon reaching its destination. The slurry design must be stable and compatible, with appropriate solid content and particle size distribution. Additionally, it should include special additives to meet thickening time requirements and ensure the development of adequate compressive strength (CS). In situations where cement plug operations face a high risk of contamination, the limitations of conventional mechanical separators can pose significant challenges. These limitations include long drill pipe lengths, the typical telescopic configuration of drill pipes (with larger inside diameters at the surface tapering to smaller diameters at the bottom, along with crossover connections that can damage mechanical separators), small cement volumes, and limited fluid hierarchy density. In such cases, the use of a plug placement tool has proven successful, even for operations at depths of up to 5,000 meters. In high-pressure, high-temperature (HPHT) environments at depths ranging from 5,000 to 8,000 meters, cement plug placement has been achievable only through optimizing slurry properties and modifying standard placement techniques. This study explores how adapting the existing placement method by increasing the amount of darts from two to three has significantly improved efficiency, resulting in less than a 2% discrepancy between the theoretical and actual tagged top of cement.