Control Line
Control lines are metal tubes that are used for conveying hydraulic pressure from control unit to the downhole equipment to be operated. In completion or testing mode, the control lines run along the tubing from surface to the downhole tool like ‘Sub-surface safety valve’. It is connected to the control panel on rig / platform, which is used for operating the downhole tool.
Coil Tubing
Coil Tubing is a continuous string of flexible steel pipe that wound on a reel. Coil tubing is normally hundreds to thousand of feet long. The coil tubing reel is mounted on the coil tubing unit which also has other devices and controls for lowering the coil tubing into the well by unwinding and pull it out to rewind on the reel.
Bridge Plug
Bridge plugs are used for zonal isolation or suspension. They are made up of cast iron, brass, aluminum and rubber parts. Bridge plugs can be set on wireline, slickline or drill pipe.
Retarder
Retarders are the chemicals added to cement slurry for delaying the setting time. Class G ad H are most commonly used cements for well cementing. Neat slurry prepared with these cements do not have long enough setting time or thickening time at temperatures above 100 deg F. Depending on the well depth, downhole temperature and total cementing operation time, the slurry prepared with neat cement could start thickening before the completion of cementing process and make the slurry un-pumpable. Hence cement retarders need to be added to the slurry in required proportion depending on specific application.
Remedial Cementing
Remedial cementing is carried out to repair the cement if the primary cement job fails to achieve desired results. As part of remedial cement job, cement is either squeezed into the casing annulus or placed at specified depth as a plug.
Primary Cementing
Primary cementation is the process of securing the casing in the well with cement. Cement is pumped through the casing and is placed in the annulus between casing and formation. Objective of primary cementation is to create zonal isolation between the casing annulus and hydrocarbon or water bearing formation. Good cementation is important for safety of the well and also for successful well testing or completion.
Fluid Loss Control Agent
Fluid loss control agent is an important cement additive that reduces the fluid loss from slurry. When cement slurry is pumped into the well, it comes across several open formations. If a formation is porous and permeable, the aqueous phase of the slurry escapes into the formation under pumping pressure. This changes the rheological properties of the slurry due to improper solid and liquid fraction. If the loss of fluid is not controlled, the slurry could become too thick and eventually unpumpable causing failure of cement job.
Dump Bailer
Dump Bailer is a mechanical device used for spotting a cement plug above a permanent bridge plug. It is a vessel that is filled with measured quantity of cement slurry and is run in the well on wireline. As the Dump Bailer touches the permanent bridge plug, it is opened through a mechanical or electrical opening mechanism. As the vessel opens, the cement slurry is dumped on the plug by raising the bailer. Dump Bailer provides a quick and relatively inexpensive means of spotting cement plug. It is used quiet effectively at shallow depths. At deeper intervals, special cement slurry design is required to maintain desired slurry properties considering well temperature and static time for running the bailer in the well to spotting depth.
Dispersant
Dispersant is a chemical that is used for reducing the viscosity of the cement slurry. Since cement slurry is prepared by mixing dry blended cement with mix-water which has many chemicals, achieving desired rheological properties in the final mixture could be a challenge. It is very important for the slurry to have good rheological properties to be able to pump it through long narrow annuli. Dispersant helps in reducing the viscosity and making slurry pumpable without too high surface pressure.
Cement Squeeze
Cement Squeeze is a method of carrying out a remedial cementing job. Cement slurry is forced into the holes, fractures or splits in casing / formation. As the slurry is forced under pressure, the solid particles bridge the opening and the aqueous part escapes the slurry under squeeze pressure. The slurry is squeezed until the pressure reaches a predetermined level.
Cement Plug
Cement plugs are placed in the well for either repairing a leak, sealing a severe loss circulation zone, for side tracking or abandoning the well. It is a process of placing the cement slurry at desired depth and allowing it to set. Various different placing techniques are used depending on requirement and scenarios.
Cement Additives
Cement slurry pumped for casing cementation or setting a cement plug need to fulfill several property requirements like weight, fluid loss, thickening time etc. Mix water is prepared by adding various different chemicals for achieving required properties. These chemicals are called cement additives. Every cementing company has its own proprietary chemicals that they use as cement additives.
Balanced Plug
Balanced plug is a technique of placing a cement plug in such a way that the levels of different fluids inside and outside drill pipe are same. It is the most common method of plug placement. Having the same level of fluids in drill pipe and annulus provides stability to the fluid system in the slurry. It minimizes the contamination risk and enhances the plug effectiveness.
Accelerators
Accelerator, Intensifier, or Booster are different names for the same tool. An accelerator is used in conjunction with a jar in the string to intensify the force generated by the jar. It is positioned above the jar separated by drill collars. Accelerators are also available in double-acting mode to match the jar action.
A compressible fluid and an effective sealing assembly in the accelerator make the intensifying action possible. It stores energy when put under strain and acts like a hydraulic spring by releasing the energy as the strain is removed. It becomes a handy tool in shallow intervals where the drill string is not too long. Using an accelerator in combination with a jar increases the chances of releasing a stuck string.
Accelerator helps in keeping the energy generated by the jarring impact from being lost up the hole. Without an accelerator, the drill string absorbs some of the impact force of the jar, which reduces its effectiveness, and the string is also subject to undesirable jarring shock loads. The jar accelerator combination is used to intensify the effect of the jar at any depth.
PVT Sampling
PVT is the abbreviation of Pressure, Volume, Temperature. PVT Sampling is the process of collecting reservoir fluid samples for laboratory PVT analysis. The samples are collected at appropriate location downhole or on surface where the samples represent the system in the reservoir.
P&A
P&A is a commonly used abbreviation of Plug & Abandon. It is the process of permanently abandoning a well by setting a set of abandonment plugs. Usually, when a well is drilled to the intended target depth and after evaluation if it is determined that the well will not be completed for production in near future, the well is abandoned. A set of cement and/or mechanical plugs are placed in the well to ensure complete isolation as per regulatory requirements. Every company has its own guidelines and policies for well abandonment. The type and number of plugs depend on the type of well and expected reservoir pressure, fluid, etc.
A well can be temporarily abandoned as well if it is planned to complete, produce or reenter in the future. Offshore, a Mud Line Suspension (MLS) system is installed to be able to tie back the well in the future once the platform is installed. A corrosion cap is also installed on the top of the well to protect tieback threads and to avoid any debris getting into the well. The Corrosion Cap can be removed and retrieved before tying back the well to the platform.
Sucker Rod Pump
Sucker Rod Pumps are artificial lift method very commonly used for wells where reservoir does not have enough energy to flow naturally. The system broadly consists of a down hole pump plunger and valve assembly. The pump is powered by beam and crank assembly at surface. These are used for land wells and application becomes limited with deeper wells.
PCP
PCP is an abbreviation of 'Progressive Cavity Pump'. This is used for artificially lifting a well where the reservoir does not have enough energy to flow naturally. PCP creates negative pressure forcing the fluid to move up. PCP has been found to be useful for extracting high-viscosity crude oil. PCPs do not perform well in deeper and deviated wells.
Tubing
Tubing is broadly referred to as the conduit that is run inside the casing or open hole in a wellbore. Tubing is used as a flow path for the formation fluid to flow from the reservoir to the surface or for pumping fluid downhole. The term is mainly used for the tubulars that are used for well testing or well completion after drilling a well. Tubing should be able to withstand burst, collapse, tensile, compressive, and tri-axial loads during all operations. They should also have the material properties to handle the corrosivity of fluid in a wellbore or formation. Tubing is designed to meet all stresses and conditions in routine well operations and also to specific requirements of special operations.
TCP
TCP is the abbreviation of 'Tubing Conveyed Perforating'. It's the process of running perforating guns on tubing, drill pipe, or coil tubing for perforating a required section of the well. Guns can also be run on wireline, but have limited application to low inclination wells. TCP is well suited for perforating vertical, highly deviated, or horizontal wells. It also facilitates underbalanced perforations, which limit the formation damage. TCP guns can be dropped in the well if there is enough rat hole. They can also be left attached to the tubing string and can be recovered later when pulling the tubular out of the well.