Wireline
From Wikipedia, the free encyclopedia
The term wireline usually refers to a cabling technology used by operators of oil and gas wells to lower equipment into the well for the purposes of a well intervention. In its simplest and most used form, the wireline simply consists of a single strand of metal wire most commonly 0.108" or 0.125" in diameter (sometimes referred to as slickline). In other cases, the wire will be composed of braided strands, rendering it stronger and heavier (called braided line). Braided line can contain an inner core of insulated wires which provide power to equipment located at the end of the cable (called electric line or E-line) and provides a pathway for electrical telemetry for communication between equipment at each end of the cable. The first use of wireline in a wellbore was as a measuring device. Measuring systems using rope or flat section steel tape, were over time replaced by wire.
Contents |
[edit] Uses
The nature of slickline requires any tools to be able to operate independently of electrical communication from surface. This limits slickline to jobs such as setting plugs and straddes, which merely require mechanical action. Some completion components may be deployed and retrieved on slickline such as wireline retrievable safety valves and gas lift valves. Slickline can also be used for light fishing, the process of trying to retrieve other equipment, which has been dropped down the hole.
Braided line is generally used when the strength of slickline is insufficient for the task. Most commonly, this is for heavy fishing such as retrieving broken drill pipe.
Electric line is used for well logging, involving deploying sensory tools designed to provide some information about the properties of the well. These tools could be gamma ray or neutron tools intended to analyse the properties of the reservoir rock or calliper tools intended to measure the size of the well bore, particularly useful for determining any corrosion in the tubing or casing. Other logging tools could measure the properties of fluids in the well bore, such as temperature, rate of flow, pressure etc. More recently, downhole cameras have seen increasing use. Another important duty for E-line is perforating, involving lowering a strong of shaped charges to blow holes in the liner or casing at the bottom of hole to connect to the reservoir.
The recent developments of wireline tractors have allowed wireline to be used in highly deviated and horizontal wells. These require a source of electrical power and so are always run on E-line. Tractors also enable wireline to expand into the operation of milling by being able to provide rotary motion.
[edit] Wireline tools
A wireline tool string can be dozens of feet long with multiple separate tools installed to perform multiple operations at once.
[edit] Rope socket
This is a standard wireline tool, required to connect the wire to the toolstring.
[edit] Stem
Stem essentially just serves to add weight to the toolstring. The weight may be necessary to overcome the pressure of the well. Some variations of stem, called roller stem, may have wheels built into the tool to allow the tool strong to glide more easily down moderately deviated wells.
[edit] Jar
This type of tool can extend and be closed rapidly to induce a mechanical shock to the tool string. This shock can induce certain components such as plugs to lock into place and then unlock for retrieving. Spang jars are manually operated by the wireline operator who either lifts or lowers wire rapidly. Power jars uses springs or built-in hydraulics to give the jarring motion.
[edit] Pulling tools
These are tools designed for fishing other wireline components, which may have been dropped down hole. All wireline tools are designed with 'fishing necks' on their top side, intended to be easily grabbed by pulling tools. Pulling tools are also used for retrieving seated components such as plugs.
[edit] Gauge cutter
The important part of these tools is their bottom end, which is a sharp metal ring of accurately determined size. By allowing for a sharp up and down motion, the metal ring can cut through contamination such as a scale, which may build up in the well bore.
[edit] Tractors
These are electrical tools that can be used to push the toolstring into hole, overcoming wireline's disadvantage of being gravity dependent. These are used for operations in highly deviated and horizontal wells, where gravity is insufficient, even with roller stem. They can push against the side of the wellbore either through the use of wheels or through a wormlike motion.
[edit] Wireline apparatus
For oilfield work, the wireline resides on the surface, wound around a large (3 to 10 feet in diameter) spool. Operators may use a portable spool (on the back of a special truck) or a permanent part of the drilling rig. Associated with the spool one finds gearing and a motor used to turn the spool and thus raise and lower the equipment into and out of the well – the winch.
[edit] Pressure control during wireline operations
The primary barrier on a wireline rigup is the stuffing box, which contains rubber packing elements that seal around the wire as it is run in and pulled out, thereby containing well pressure. A secondary barrier is a wireline blowout preventer, which can be closed around the wire if there is a risk of failure of the stuffing box. For braided line, a grease injection head is needed above the BOP to ensure a seal despite braided contours of the wire. The tertiary barrier for slickline is the upper master valve on the Xmas tree, which is capable of cutting the wire when closed. For braided line, as it is thicker, a shear-seal BOP is needed.
[edit] Wireline images
 Wireline attached to top of Chistmas Tree |
 Oil Well Top of Wirleine |
 Wirline Truck with drum (inside) |
 Wax being removed off a wireline wax knife |
 BO shifting tool |
