Well intervention
A well intervention, or well work, is any operation carried out on an oil or gas well during, or at the end of, its productive life that alters the state of the well or well geometry, provides well diagnostics, or manages the production of the well.
Pumping 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 Christmas tree and pumping in a fluid determined necessary for the particular well.
The complexity of wellhead and Christmas tree maintenance can vary depending on the condition of the wellheads. Scheduled annual maintenance may simply involve greasing and pressure testing the valve on the hardware. Sometimes the downhole safety valve is pressure tested as well.
Slickline operations may be used for fishing, gauge cutting, setting or removing plugs, deploying or removing wireline retrievable valves and memory logging.
Braided line is more complex than slickline due to the need for a grease injection system in the rigup to ensure the blowout preventer (BOP) 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 Christmas tree can only cut slickline. Braided line includes both the core-less variety used for heaving fishing and electric-line used for well logging and perforating.
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 tasks normally done by wireline if the deviation[clarification needed] in the well is too severe for gravity to lower the toolstring and circumstances prevent the use of a wireline tractor.
