Servicing >> Workover
Workover activities include one or more of a variety of remedial operations
on a producing well to try to increase production.
|
Fig. 1. Example of a workover rig
|
Sand Cleanout |
Sand cleanout operations are performed to remove buildup of sand in the wellbore. Hazards are
Potential Hazard:
Additional Information:
-
Standards. American Petroleum Institute (API).
-
RP 54, Recommended Practice for Occupational Safety for Oil and Gas Well
Drilling and Servicing Operations, Wireline Service. (2007, March).
|
Repairing
Liners and Casing |
Liners and casing are essentially the same and repair procedures are the
same for both. Casing can be damaged by corrosion, abrasion, pressure, or
other forces that create holes or splits. A packer is run down the well to
locate the hole in the casing. Fluid is pumped into the casing above the
packer. A loss of pressure indicates a hole in the casing. The following
are the principal methods for repairing casing:
-
Squeeze cementing.
-
Patching a liner.
-
Replacing casing.
-
Adding a liner.
-
Opening collapsed casing.
Potential Hazard:
|
Sidetracking |
Sidetracking is the workover term for drilling a directional hole
to bypass an obstruction in the well that cannot be removed or
damage to the well, such as collapsed casing that cannot be repaired.
Sidetracking is also done to deepen a well or to relocate the bottom of
the well in a more productive zone, which is horizontally removed from the original
well.
To sidetrack, a hole (called a window) is made in the casing above the
obstruction. The well is then plugged with cement below the window.
Special drill tools, such as a whipstock, bent housing, or bent sub are
used to drill off at an angle from the main well. This new hole is
completed in the same manner as any well after a liner is set.
Potential Hazard:
- The hazards associated with sidetracking are similar to Drilling.
|
Plug-Back |
Plug-back places a cement plug at one or
more locations in a well to shut off flow from below the plug. Plug-back is
also used before abandoning a well or before sidetracking is done.
There are two methods for placing a cement plug in a well:
Potential Hazard:
|
|