Stuffing Box Plunger
The plunger, which serves as an internal blowout preventer, essentially shuts-in the stuffing box in the event of wire breakage.
If the wire breaks, the broken end will eventually pass through, and out of the stuffing box. The well now has a free path to the surface through the stuffing, so technically, a blowout exists.
When the wire leaves the stuffing box a differential pressure is created between the bottom of the plunger (which is experiencing surface well pressure) and the top of the plunger (atmospheric pressure). This differential causes the plunger to rapidly move upward. The soft rubber nose of the plunger collapses on itself and shuts off the flow.
Chemical Injection Sub
This device, usually placed just below the stuffing box, is designed to inject chemicals and de-icing agents onto the wire when there is a chance of hydrate formation.
The sub incorporates a 2 liter internal chamber which is filled using a high pressure hand pump. It also has packing which seals around the wire minimizing chemicals falling into the well.
The chemical inlet has an internal check valve which prevents the escape of wellbore fluids.
The tool catcher is designed to “latch” the rope socket after it’s been pulled into the lubricator and prevents the tools string from falling in the event the wire is accidentally pulled from the rope socket.
The spring-loaded dogs allow the rope socket head to be pulled above the dogs. If the wire is pulled out of the rope socket the dogs latch the rope socket fishing neck.
The rope socket can be released by applying hydraulic pressure to the inlet from a hand-operated pump. The dogs open and the tool string can be retrieved from the lubricator.
The lubricator acts as an extension of the wellbore enabling a tool string to enter and be retrieved from a live well.
The body sections, normally 8 feet or 10 feet in length, are connected to male and female quick unions at the top and bottom respectively.
Lubricator sections are available in pressure ratings of 5000 psi, 10000 psi and 15000 psi and in diameters up to 7”.
As an option there are those who install a pump- in sub as part of the lubricator. The sub must be of the same pressure rating as the lubricator, wireline valve, and tree connection.
A tool trap is placed below the lubricator sections and serves to prevent the tool string from falling down the hole if the operator inadvertently pulls out of the rope socket.
There are two types of tool traps: manual and hydraulic. Shown here is a manual tool trap and is recommended when surface pressure is low.
The flapper is manually opened allowing the tool string to descend into the well. After the tool string passes the tool trap, the flapper is manually closed. The flapper, which is spring-loaded (shown below) allows the wireline to move unimpeded and will open upward when the rope socket contacts the flapper. When the lower section of the tool string passes the flapper it closes.
Pictured here is a hydraulic tool trap. Its purpose and basic function is similar to the manual model on the previous page but this one operates hydraulically and incorporates a manual back-up.
The hydraulic model is recommended when surface pressure exceeds 5000 psi or if hydrogen sulfide is present at the surface.
Wireline BOP’s, or wireline valves as they are commonly known, are considered to be “secondary barriers” used to contain wellbore surface pressures. There are both manual and hydraulically operated models. The hydraulic models are complimented with manual back-ups. Wireline valves between wellhead or Xmas Tree and wireline lubricator
Dual rams can be used for slickline with one being a ram to seal around the wire and the open hole and the other being a slickline cutter ram.
Dual rams are also common in braided line work. The top ram is installed conventionally and the lower ram is inverted to assist in sealing around the braided wire. Grease can be injected between the rams under pressure to effect the seal.
Wireline valves are customarily installed directly onto the tree to provide the least number of potential leak points. Where needed, a riser can be installed between the tree and the wireline valve/s.
All wireline valves are equipped with equalizing valves which serve to equalize pressure across closed rams prior to opening.