Learning Objectives
After completing this topic “Primary Cementing“, you will be able to:
- Define primary cementing and associated terms.
- Summarize the unique requirements for cementing each of the various casing strings in the context of each string’s purpose and placement in the well.
- Define primary cementing job design factors.
- Summarize the major considerations involved in planning a job.
- List general guidelines for ensuring a successful primary cement job.
- List the equipment, procedures and areas of application for single-stage, multi-stage, and liner primary cement jobs.
- State the challenges and special requirements involved in cementing subsea wells and horizontal lateral intervals.
- Describe inner string cementing and the application of an external casing packer.
- Describe best practices for operational issues.
Introduction
The most common cementing operation is primary cementing, which involves displacing the slurry down the inside of a string of casing, around the bottom of the casing shoe, and up the outside of the casing string, where it can harden into a competent cement sheath (Animation 1).
Primary cementing overview Animation 1
Primary cementing is performed immediately after casing is run into the borehole. The details and placement techniques may vary depending on conditions, but the process is nearly the same regardless of the purpose or size of the casing string. The large majority of cementing operations are primary cementing jobs.
There are three general types of primary cementing techniques:
- Single-stage cementing: The most common procedure is the single-stage primary cement job using the two-plug system. Cement is pumped down the casing between two rubber wiper plugs which are used to clean the interior wall of the casing and to prevent contamination of the cement by the drilling mud.
- Multi-stage cementing: Most multi-stage cement jobs are performed to alleviate the high hydrostatic pressure exerted on formations by a long column of cement. However, the availability of low density cement slurries have made multi-stage cementing much less common than it used to be.
- Liner cementing: Liners are casing strings that extend into an open hole section of the wellbore but are hung off the previous casing string instead of being tied back to the surface. The cement slurry is pumped through the drill pipe and into the top of the liner through specialized equipment.
This course discusses each of these types of cementing operations. Because primary cementing procedures are driven in large part by the well interval in which a particular casing string is being placed, the course begins with a review of the hole intervals and general casing classifications, followed by a review of the common data needed to design typical job.
