Glossary
Browse the IADC Lexicon alphabetically or by category. Get comprehensive definitions of drilling industry terms.
Class 3
Definition(s)
Class 3
Third in the hierarchy of used drill pipe service classifications for used drill pipe that does not meet class 2 requirements. Source: API RP 7G-2, Recommended Practice for Inspection and Classification of Used Drill Stem Elements, First Edition, August 2009. Global StandardsLeak-Off Test (LOT)
Definition(s)
Leak-Off Test
Application of pressure by superimposing a surface pressure on a fluid column in order to determine the pressure at which the exposed formation accepts whole fluid. Source: ISO 16530-1:2017, Petroleum and natural gas industries — Well integrity – Part 1: Life cycle governance, First Edition, March 2017. Global Standards Source: API RP 59, Recommended Practice for Well Control Operations, Second Edition, May 2006. Global StandardsLeak-Off Test (LOT)
A leak-off test is a procedure used to determine the wellbore pressure required to initiate a fracture in the open or exposed formations. Source: API STD 65 – Part 2, Isolating Potential Flow Zones During Well Construction, Upstream Segment, Second Edition, December 2010. Global StandardsBox Thread
Definition(s)
Box Thread
Internal (female) threads of a rotary shouldered connection. Source: API RP 7G-2, Recommended Practice for Inspection and Classification of Used Drill Stem Elements, First Edition, August 2009. Global StandardsLCM
Definition(s)
LCM
Life cycle management. Source: API STANDARD 18LCM, Product Life Cycle Management System Requirements for the Petroleum and Natural Gas Industries, First Edition, April 2017. Global StandardsLCM
Lost control material. Source:API SPECIFICATION 19TT, Specification for Downhole Well Test Tools and Related Equipment, First Edition, October 2016. Global StandardsLCM
Lost circulation material. Source: API STD 65 – Part 2, Isolating Potential Flow Zones During Well Construction, Upstream Segment, Second Edition, December 2010. Global Standards Source: Deepwater Well Control Guidelines. IADC GuidelinesBox End
Definition(s)
Box End
End of pipe with internal threads. Source: API RP 7G-2, Recommended Practice for Inspection and Classification of Used Drill Stem Elements, First Edition, August 2009. Global StandardsBottleneck Sub
Definition(s)
Bottleneck Sub
Sub with two distinct outside diameters. Source: API RP 7G-2, Recommended Practice for Inspection and Classification of Used Drill Stem Elements, First Edition, August 2009. Global StandardsHybrid Wells
Definition(s)
Hybrid Wells
Well drilled with a subsea wellhead and completed with a surface casing head, a surface tubing head, a surface tubing hanger and a surface tree.- Note: 1 to entry: A hybrid well can have either one (single-bore production riser) casing string or two (dual-bore production riser) casing strings brought up from the subsea wellhead and tied back to the surface equipment.
Hybrid Wells
Wells drilled with a subsea wellhead and completed with a surface casing head, a surface tubing head, a surface tubing hanger, and a surface christmas tree. A hybrid well may have either one (single bore production riser) casing string or two (dual bore production riser) casing strings brought up from the subsea wellhead and tied back to the surface equipment. These wells are typically located on floating production platforms such as spars or TLPs. Source: API RP 90, Annular Casing Pressure Management for Offshore Wells, Upstream Segment. First Edition, August 2006. Global StandardsHybrid Wells
Wells drilled with a subsea wellhead and completed with a surface casing head, a surface tubing head, a surface tubing hanger and a surface tree. Source: API STD 65 – Part 2, Isolating Potential Flow Zones During Well Construction, Upstream Segment, Second Edition, December 2010. Global StandardsFormation Fluids
Definition(s)
Formation Fluids
Fluids present within the pores, fractures, faults, vugs, caverns, or any other spaces of formations are called formation fluids whether or not they were naturally formed or injected therein. The physical state of formation fluids may be liquids or gases and include various types such as hydrocarbons, fresh or saline water, carbon dioxide, hydrogen sulfide, etc. Source: API STD 65 – Part 2, Isolating Potential Flow Zones During Well Construction, Upstream Segment, Second Edition, December 2010. Global StandardsFormation Fluids
Formation fluids as mentioned in the first subsection, also means hydrates and water under pressure. Source: Guidelines Regarding the Activities Regulations, Norway, updated December 2012. Regulatory GuidanceFixed Platform Wells
Definition(s)
Fixed Platform Wells
Wells completed with a surface wellhead and a surface tree on a fixed platform. All of the casing strings are tied back to the surface wellhead. Source: API STD 65 – Part 2, Isolating Potential Flow Zones During Well Construction, Upstream Segment, Second Edition, December 2010. Global Standards Source: API RP 90, Annular Casing Pressure Management for Offshore Wells, Upstream Segment. First Edition, August 2006. Global StandardsFIT
Definition(s)
FIT
Application of pressure by superimposing a surface pressure on a fluid column in order to determine ability of a subsurface zone to withstand a certain pressure. Source: ISO 16530-1:2017, Petroleum and natural gas industries — Well integrity – Part 1: Life cycle governance, First Edition, March 2017. Global StandardsFIT
Geometric relationship between parts. Source: API SPEC 6A, Specification for Wellhead and Christmas Tree Equipment, Twentieth Edition, October 2010 (Addendum November 2012). Global StandardsFIT
Fit, when defined as the geometric relationship between parts, includes the tolerance criteria used during the design of a part and its mating parts. Fit, when defined as the state of being adjusted to or shaped for, includes the tolerance criteria used during the design of a seal and its mating parts. Source: API SPEC 6A, Specification for Wellhead and Christmas Tree Equipment, Twentieth Edition, October 2010 (Addendum November 2012). Global Standards Source: API SPEC 17D, Design and Operation of Subsea Production Systems—Subsea Wellhead and Tree Equipment, Upstream Segment, Second Edition May 2011 (Errata September 2011). Global StandardsFIT
Geometric relationship between parts including the tolerance criteria used during the design of a part and its mating parts.
Source:API SPECIFICATION 19TT, Specification for Downhole Well Test Tools and Related Equipment, First Edition, October 2016. Global StandardsFIT
Geometric relationship between parts. NOTE This includes the tolerance criteria used during the design of a part and its mating parts, including seals. Source: API SPEC 14A, Specification for Subsurface Safety Valve Equipment, Eleventh Edition, October 2005 (Reaffirmed June 2012). Global StandardsFIT
1. The geometric relationship between parts. This would include the tolerance criteria used during the design of a part and its mating parts. 2. The state of being adjusted to or shaped for, this would include the tolerance criteria used during the design of a seal and its mating parts. Source: API SPEC 16C, Specification for Choke and Kill Systems, First Edition, January 1993 (Reaffirmed 2001). Global StandardsFIT
Formation integrity test. Source: ISO 16530-1:2017, Petroleum and natural gas industries — Well integrity – Part 1: Life cycle governance, First Edition, March 2017. Global Standards Source: API Bulletin 97, Well Construction Interface Document Guidelines, First Edition, December 2013. Global Standards Source: API STD 65 – Part 2, Isolating Potential Flow Zones During Well Construction, Upstream Segment, Second Edition, December 2010. Global Standards Source: Deep Water Well Control Guidlines. IADC GuidelinesFG
Definition(s)
FG
Frac gradient. Source: API STD 65 – Part 2, Isolating Potential Flow Zones During Well Construction, Upstream Segment, Second Edition, December 2010. Global StandardsExternal Casing Packer (ECP)
Definition(s)
External Casing Packer (ECP)
An external casing packer is a mechanical annular barrier that has elastomeric elements that seal the annulus when inflated. Also see the definition in this section for annular packers and the description of an ECP in 4.4. Source: API STD 65 – Part 2, Isolating Potential Flow Zones During Well Construction, Upstream Segment, Second Edition, December 2010. Global StandardsEquivalent Circulating Density (ECD)
Definition(s)
Equivalent Circulating Density
The effective density of the circulating fluid in the wellbore resulting from the sum of the pressure imposed by the static fluid column, friction pressure and surface back-pressure.
Source: ABS Guide for Classification and Certification of Managed Pressure Drilling Systems, September 2017. Global StandardsEquivalent Circulating Density (ECD)
Equivalent circulating density is the effective density of the circulating fluid in the wellbore resulting from the sum of the hydrostatic pressure imposed by the static fluid column and the friction pressure. Source: API STD 65 – Part 2, Isolating Potential Flow Zones During Well Construction, Upstream Segment, Second Edition, December 2010. Global StandardsEquivalent Circulating Density (ECD)
The sum of pressure exerted by hydrostatic head of fluid, drilled solids, and friction pressure losses in the annulus divided by depth of interest and by 0.052, if ECD is to be expressed in pounds per gallon (lb/gal). Source: API RP 59, Recommended Practice for Well Control Operations, Second Edition, May 2006. Global StandardsEMW
Definition(s)
EMW
Equivalent mud weight. Source: API STD 65 – Part 2, Isolating Potential Flow Zones During Well Construction, Upstream Segment, Second Edition, December 2010. Global StandardsECP
Definition(s)
ECP
External casing packer. Source: API STD 65 – Part 2, Isolating Potential Flow Zones During Well Construction, Upstream Segment, Second Edition, December 2010. Global StandardsECD
Definition(s)
ECD
Equivalent circulating density. Source: ABS Guide for Classification and Certification of Managed Pressure Drilling Systems, September 2017. Global Standards Source: ISO 16530-1:2017, Petroleum and natural gas industries — Well integrity – Part 1: Life cycle governance, First Edition, March 2017. Global Standards Source: API STD 65 – Part 2, Isolating Potential Flow Zones During Well Construction, Upstream Segment, Second Edition, December 2010. Global Standards Source: NORSOK D-010, Well integrity in drilling and well operations, Rev. 3, August 2004. Global StandardsECD
The effective density of the circulating fluid in the wellbore resulting from the sum of the pressure imposed by the static fluid column, friction pressure and surface back-pressure.
Source: ABS Guide for Classification and Certification of Managed Pressure Drilling Systems, September 2017. Global StandardsDrive/Jet Pipe
Definition(s)
Drive/Jet Pipe
Supports unconsolidated deposits and provides hole stability for initial drilling operations. This is normally the first string set and provides no pressure containment. This string can also provide structural support to the well system. Source: API RP 90, Annular Casing Pressure Management for Offshore Wells, Upstream Segment. First Edition, August 2006. Global StandardsDrive/Jet Pipe
Casing which supports unconsolidated sediments providing hole stability for initial drilling operations. This is normally the first string set and provides no pressure containment. This string can also provide structural support to the well system. See also definition for structural pipe (or casing). Source: API STD 65 – Part 2, Isolating Potential Flow Zones During Well Construction, Upstream Segment, Second Edition, December 2010. Global StandardsDiverter
Definition(s)
Diverter
Device attached to the marine riser or wellhead to close the vertical flow path and direct the flow in a predetermined direction.
Source: API Specification 16Q, Design, Selection, Operation, and Maintenance of Marine Drilling Riser Systems, Second Edition, April 2017. Global StandardsDiverter
A device attached to the wellhead or marine riser to close the vertical flow path and direct well flow away from the drillfloor and rig. Source: API RP 16Q, Recommended Practice for Design, Selection, Operation and Maintenance of Marine Drilling Riser Systems, First Edition, November 1993 (Reaffirmed August 2001). Global Standards Source: ISO 13624-1:2009, Petroleum and natural gas industries – Drilling and production equipment – Part 1:Design and operation of marine drilling riser equipment. Global StandardsDiverter
A device attached to the wellhead or marine riser to close the vertical access and direct flow into a line away from the rig. Source: API RP 59, Recommended Practice for Well Control Operations, Second Edition, May 2006. Global StandardsDiverter
A device attached to the wellhead or marine riser to close the vertical access and direct any flow into a line and away from the rig. Source: API RP 64, Recommended Practice for Diverter Systems Equipment and Operations, Second Edition, November 2001 (March 1, 2007). Global StandardsDiverter
A device attached to the wellhead or marine riser to close the vertical flow path and direct well flow (typically shallow gas) into a vent line away from the rig. Source: API SPEC 16D, Specification for Control Systems for Drilling Well Control Equipment and Control Systems for Diverter Equipment, Upstream Segment, Second Edition, July 2004. Global StandardsDiverter
A device connected to the top of the wellhead or marine riser, directing flow away from the rig. Source: API STD 65 – Part 2, Isolating Potential Flow Zones During Well Construction, Upstream Segment, Second Edition, December 2010. Global StandardsDiverter
Typically a device attached to the wellhead or marine riser to close the vertical access and direct any flow from the well away from the rig. The line running from the diverter may be referred to as the “Blooie line”. Source: IADC UBO / MPD Glossary, December 2011. Global StandardsDiverter
"Diverter" means a device attached to the wellhead to close the vertical access and direct any flow into a line away from the rig. Diverters differ from blowout preventers in that flow is not stopped but rather the flow path is redirected away from the rig. Source: Corporation Commission, Oil and Gas Conservation, Oklahoma Administrative Code 165:10, February 2013. RegulationsCritical Static Gel Strength (CSGS)
Definition(s)
Critical Static Gel Strength (CSGS)
Specific static gel strength of a cement in which hydrostatic-pressure equilibrium is reached between the decayed hydrostatic pressure transmission of the cement column (and other fluids in the annulus) and the pore pressure of the formation. See Annex A. NOTE The critical static gel strength is measured in pascals or newtons per square metre (pounds force per 100 square feet). Source: API RP 10B-6, Recommended Practice on Determining the Static Gel Strength of Cement Formulations, Upstream Segment, First Edition, August 2010. Global StandardsCritical Static Gel Strength (CSGS)
The static gel strength of the cement that results in the decay of hydrostatic pressure to the point at which pressure is balanced (hydrostatic equals pore pressure) at a point adjacent to the potential flowing formation(s). Source: API STD 65 – Part 2, Isolating Potential Flow Zones During Well Construction, Upstream Segment, Second Edition, December 2010. Global StandardsCritical Gel Strength Period (CGSP)
Definition(s)
Critical Gel Strength Period
Time required for the cement to progress from Critical Static Gel Strength to a static gel strength of 500 lb/100 ft2. Source: API RP 65, Cementing Shallow Water Flow Zones in Deepwater Wells, First Edition, September 2002 (August 2003). Global StandardsCritical Gel Strength Period (CGSP)
The time between the development of the critical static gel strength (CSGS) and a static gel strength of 500 lbf/100 ft2. Source: API STD 65 – Part 2, Isolating Potential Flow Zones During Well Construction, Upstream Segment, Second Edition, December 2010. Global StandardsConductor Casing
Definition(s)
Conductor Casing
Component that provides structural support for the well, wellhead and completion equipment, and often used for hole stability for initial drilling operations- Note: 1 to entry: This casing string is not designed for pressure containment, but upon completion of the well it might have a casing head; therefore, it can be capable of containing low annulus pressures. For subsea and hybrid wells, the low-pressure subsea wellhead is normally installed on this casing string.
Conductor Casing
“Conductor casing” means the casing that is installed in a well to facilitate drilling of the hole for the surface casing (tubage initial). Source: Canada Oil and Gas Drilling and Production Regulations, SOR/2009-315, February 2013. Regulations Source: Drilling and Production Guidelines, The Canada-Nova Scotia Offshore Petroleum Board and Canada-Newfoundland and Labrador Offshore Petroleum Board, Canada, March 31, 2011. Regulatory Guidance Source: Nova Scotia Offshore Petroleum Drilling and Production Regulations, SOR/2009-317, Canada, current to May 31, 2012. RegulationsConductor Casing
"Conductor casing" means a casing string which is often set and cemented at a shallow depth to support and protect the top of the borehole from erosion while circulating and drilling the surface casing hole. Source: Corporation Commission, Oil and Gas Conservation, Oklahoma Administrative Code 165:10, February 2013. RegulationsConductor Casing
- “Conductor casing” means one or more strings of casing set and cemented to provide a base for an air body for diversion of shallow naturally occurring natural gas including coalbed methane and to accomplish one or more of the following well construction objectives: (a) Stabilize unconsolidated sediments; (b) Isolate shallow aquifers that provide or are capable of providing groundwater for water wells and springs in the vicinity of the well; or (c) Isolate groundwater before penetrating the workings of an active underground mine.
Conductor Casing
Provides structural support for the well, wellhead and completion equipment, and often provides hole stability for initial drilling operations. This casing string is typically not designed for pressure containment. However, in some cases, the conductor casing may serve to isolate shallow formations, similar to a surface casing. Source: API STD 65 – Part 2, Isolating Potential Flow Zones During Well Construction, Upstream Segment, Second Edition, December 2010. Global StandardsConductor Casing
"Conductor casing" means a casing string set before surface casing; depending on well configuration, "conductor casing" can be either the first or second string of casing set in a well and usually supports a diverter system. Source: Alaska Oil and Gas Conservation Commission, Definitions, Alaska Admin. Code tit. 20, § 25.990, December 7, 2012. RegulationsConductor Casing or Conductor Pipe (onshore and bottom-supported offshore installations)
A relatively short string of large diameter pipe that is set to keep the top of the hole open and provide a means of returning the upward flowing drilling fluid from the well bore to the surface drilling fluid system until the first casing string is set in the well. Source: API RP 59, Recommended Practice for Well Control Operations, Second Edition, May 2006. Global StandardsConductor Casing
Provides structural support for the well, wellhead and completion equipment, and often provides hole stability for initial drilling operations. This casing string is not designed for pressure containment, but upon completion of the well, it may have a casing head; therefore, it may be capable of containing low annular pressures. This casing is set prior to encountering any hydrocarbons at a depth where the fracture gradient will allow for an increase in mud density and is cemented to the surface or mudline. For subsea and hybrid wells, the low pressure subsea wellhead is normally installed on this casing string. Source: API RP 90, Annular Casing Pressure Management for Offshore Wells, Upstream Segment. First Edition, August 2006. Global StandardsCompletion String
Definition(s)
Completion String
String consisting primarily of production tubing, but also including additional components such as the surface-controlled subsurface safety valve (SCSSV), gas-lift mandrels, chemical injection and instrument ports, landing nipples, and packer or packer seal assemblies- Note: 1 to entry: The production string is run inside the production casing and is used to conduct production fluids to the surface.