Well intervention

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A well intervention, or 'well work', is an activity involving maintenance, modification, repair or completion of an oil or gas well.

Contents

[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] Completion

This is the process of making a well ready for use by putting in place the completion string, featuring the production tubing, the production packer and any valves, mandrels and wireline nipples built into the design.

[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

Any intervention involving subsea wells is difficult and requires much advanced planning. Light intervention vessels or drilling rigs need to be mobilised at great expense and the intricacy of rigging up onto a spool tree on the sea bed must be faced.

[edit] See also

[edit] External links

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