This article discusses perforating casing with the use of wireline for:
- carrying out remedial casing cementing, by squeezing through perforations and
- for monitoring of (formation) pressures behind the casing.
1 Casing perforation
A meeting should be held prior to rigging up for perforation, with the following staff present:
- Logging Engineer/ Well Site Geologist
- Well Service Supervisor, as applicable
- Wireline Operations Supervisor
- Drilling Supervisor
- Well Site Drilling Engineer
The main purpose of the meeting is to:
- Clarify the reporting and communication lines.
- Discuss the operation.
- Discuss any special circumstances, e.g. weather conditions, hole condition, radio silence, timing, concurrent operations, etc.
In addition a pre-job discussion with the logging and drill crews should be held.
Before the gun is run in the hole, a dummy run is made, to check that the tubing/casing is free from obstructions. The dummy should have the same OD. as the perforating gun to be used. Logging run previously conducted without any obstructions encountered, may be regarded as a dummy run, which under such circumstances may be excluded, subject to discussion with Base.
If pressures are expected to be released during perforation, or if a permeable zone is perforated, a wireline BOP, lubricator and stuffing box shall be rigged up on a wireline riser nippled up on top of the BOP. With the cable head in the lubricator, pressure test the equipment to the required pressure.
Make sure that there are no stray voltages in the cable head, or voltage potential between rig and casing, and also that the wireline unit is properly earthed.
Measure the length of each gun and the distance between first shot and CCL/GR, when assembled.
During all handling of guns, nonessential personnel must be excluded from the work area.
When guns are armed all personnel shall keep out of the line of fire, until the gun is safely in the well.
2 Depth Correlation
Run casing collar locator (CCL) and gamma-ray (GR) logs over the entire interval to be perforated. Record log at perforation depth, and correlate with previously run gamma-ray logs on the reference logs. To ensure that the gun is at the correct depth before shooting, the depth calculations shall independently checked twice, prior to authorise the logging engineer to fire the guns.
During the detonation, observe for indications that gun has fired.
The mud level in the hole should be carefully observed for losses or gains throughout the logging run, and specifically prior to POH. The hole should be kept full at all times.
When the perforating assembly is retrieved, ensure that the gun is in the top of lubricator before closing the wire-line valve.
When the gun is laid out on catwalk it shall be checked for unfired charges.