DOSAS provides high-quality services for well construction and remedial applications. These services are based on best practices, environmentally sound wellsite operations and innovative technology and always have safety as a priority.
Cementing is a process used to support and protect the casings in a well and to achieve or renew zonal isolation. Zonal isolation is required to prevent liquids or gases from flowing from one zone to another within the wellbore. This isolation allows the completion and production and subsequent abandonment of the well at the lowest possible cost. Isolation allows more accurate well testing to define the reservoir, maximum recovery at the least cost (reduced costs for produced water and disposal), more effective stimulation through placement focused on the reservoir, more effective enhanced recovery and reduced abandonment costs. Without isolation, the cost of each of these processes is increased and its effectiveness is reduced.
When isolation is not achieved by the primary cement job (cementation of the casing string) a squeeze job is required to correct the deficiency. Squeeze jobs are also used during the well’s life to meet changing objectives as the well and field age. Occasionally, cement plugs are set in the well to allow changes in drilling. Plugs are also used to isolate intervals within the well when it is depleted and abandoned.
Consequences of poor zonal isolation and gas migration
All these cementing treatments require careful design of the cement systems to provide the required properties of the slurry before setting and of the cement once it is in place and set. Designs must consider the conditions in the well at the time of cement placement as well as conditions that may occur at any time during the life of the well. In addition to the design of the slurry and set-cement properties, the mechanics of the placement process must be designed to accomplish optimal mud removal and cement placement. On location, the cement must be properly mixed to achieve the required properties and pumped into place, maintaining the integrity of the well.
To achieve the cementing objectives, various additives can be used to modify the slurry and set-cement properties. Specific cement slurry systems are employed to meet especially demanding applications.
DOSAS’ Cementing Technical team has international experience in achieving zonal isolation and cement-sheath integrity.