The main reasons for using remedial cementation procedures are to:

abandon specific reservoirs in a multiple reservoir completed well
seal off all perforations when abandoning a well to make sure crossflow between reservoirs is impossible
repair defective casing or liner cement jobs
repair casing leaks
isolate specific zones within reservoirs (to achieve lower gas / oil ratios, water / oil ratios, etc)
casing patch
tie back
Temporary abandon.

Types of Remedial Cementation

Three types of remedial cementation are described in this section:

Preparation of Cement Programme

Any non standard operation shall be fully discussed in the Programme.
The Operations Engineer shall prepare a Cement Programme for the job and forwarded to the Drilling Supervisor. The Drilling Supervisor shall consult with the cementing contractor and return to Operations Engineer with changes if any at least two working days before the cement job when possible.
The Operations Engineer shall check the Cement Programme and confirm its acceptance.
The programme is forwarded by Operations Engineer to Senior Operations Engineer and Head of Drilling for approval.
It is the responsibility of the Drilling Supervisor to ensure that the final proposal is accepted in writing prior to this job.