Well intervention
From Wikipedia, the free encyclopedia
A well intervention, or 'well work', is any operation carried out on a oil or gas well during , or at the end of its productive life, that alters the state of the well and or well geometry, provides well diagnostics or manages the production of the well.
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[edit] Types of well work
[edit] Pumping
This is the simplest form of intervention as it does not involve putting hardware into the well itself. Frequently it simply involves rigging up to the kill wing valve on the Xmas tree and pumping the chemicals into the well.
[edit] Wellhead and Xmas tree maintenance
The complexity of this operation can vary depending on the condition of the wellheads. Scheduled annual maintenance may simply involve greasing and pressure testing the value on the hardware. Sometimes the downhole safety valve is pressure tested as well.
[edit] Slickline
Slickline operations may be used for fishing, gauge cutting, setting or removing plugs, deploying or removing wireline retrievable valves and memory logging.
[edit] Braided line
This is more complex than slickline due to the need for a grease injection system in the rigup to ensure the BOPs can seal around the braided contours of the wire. It also requires an additional shear-seal BOP as a tertiary barrier as the upper master valve on the Xmas tree can only cut slickline. Braided line includes both the core-less variety used for heaving fishing and electric-line used for logging and perforating.
[edit] Coiled tubing
Coiled tubing is used when it is desired to pump chemicals directly to the bottom of the well, such as in a circulating operation or a chemical wash. It can also be used for wireline tasks if the deviation in the well is too severe for gravity to lower the toolstring and circumstances prevent the use of a wireline tractor.
[edit] Snubbing
Also known as hydraulic workover, this involves lowering a string of pipe into the well to perform the required tasks. The rigup is larger than for coiled tubing and the pipe more rigid.
[edit] Workover
In some older wells, changing reservoir conditions or deteriorating condition of the completion may necessitate pulling it out to replace it with a fresh completion.
[edit] Subsea Well Intervention
Subsea Well Interventions offer up many challenges and requires much advanced planning. The cost of subsea intervention has in the past inhibited the intervention but in the current climate are much more viable. These interventions are commonly executed from Light/ medium intervention vessels or Mobile Offshore Drilling Units(MODU) for the heavier interventions such as Snubbing and Workover drilling rigs.
[edit] See also
- Petroleum industry
- Oil well
- Xmas tree
- Wellhead
- Wireline
- Coiled tubing
- Snubbing
- Well services
- List of oilfield service companies
- Blowout preventer
- Drilling rig
