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Oil and Gas Well Drilling and Servicing eTool
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Servicing Workover
Fig. 1. Example of a workover rig
Workover activities include one or more of a variety of remedial operations on a producing well to try to increase production.
Hazards related to workover activities may include:
- Sand Cleanout
- Repairing Liners and Casing
- Well Recompletions
Sand cleanout operations are performed to remove buildup of sand in the wellbore.
Potential Hazard:
- Hazards are similar to those for well servicing. See Wireline Operations.
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).
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:
- Hazards are similar to those for installing casing. See Casing Operations and Cementing.
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 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:
- Plug-back using tubing.
- Plug-back using a dump bailer (see Wireline Operations).
Potential Hazard: