Discharge Pressure Allowable

Discharge Pressure Allowable

Definition(s)

Discharge Pressure Allowable

Pressure allowable that specifies the pressure that triggers the simultaneous shutdown of all the units. Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Discharge Pressure

Discharge Pressure

Definition(s)

Discharge Pressure

Fluid pressure as it leaves a pump, compressor, or valve. Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Discharge Nozzle

Discharge Nozzle

Definition(s)

Discharge Nozzle

Port through which fluid leaves the pump or compressor. Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Discharge Control

Discharge Control

Definition(s)

Discharge Control

Control based on the limits of the station discharge pressure Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Differential Pressure

Differential Pressure

Definition(s)

Differential Pressure

Difference in pressure between any two points (p1 and p2); measured in “psid”. Source: API Specification 16A, Specification for Drill-through Equipment, Fourth Edition, April 2017. Global Standards

Differential Pressure

Difference between internal and external pressure or the difference in pressure across a closure mechanism or a packer element.

Source:API SPECIFICATION 19TT, Specification for Downhole Well Test Tools and Related Equipment, First Edition, October 2016. Global Standards

Differential Pressure

The difference in pressure between the hydrostatic head of the drilling fluid in the fluid column, and the pressure exerted by or from the formation at any given depth in the hole. May be positive, zero, or negative with respect to the hydrostatic head. Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Differential Head

Differential Head

Definition(s)

Differential Head

Increase in head between the suction and discharge nozzles of pumps or compressors (see also: head).. Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Determined Viscosity

Determined Viscosity

Definition(s)

Determined Viscosity

Actual measurement of viscosity taken with a viscometer. Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Design Capacity

Design Capacity

Definition(s)

Design Capacity

Maximum average capacity of the line or vessel calculated assuming ideal operating conditions. Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Densitometer

Densitometer

Definition(s)

Densitometer

Instrument that measures its fluid density. Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Dehydrator

Dehydrator

Definition(s)

Dehydrator

Vessel used to remove water vapor from gas. Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Dehydration

Dehydration

Definition(s)

Dehydration

Removal of water vapor from gas. Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Degree of Tolerance

Degree of Tolerance

Definition(s)

Degree of Tolerance

Value assigned by an operator for a change in system conditions (magnitude) over a given time (interval) for the present state of the system (steady state or transition). Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Degree-day

Degree-day

Definition(s)

Degree-day

Measure of the extent to which the mean daily temperature varies from an assumed base, usually 65° F; one degree day is counted for each degree of variation. Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Dead Band

Dead Band

Definition(s)

Dead Band

How far a device can move within its mechanical linkage before it triggers a reaction. Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Darcy Equation

Darcy Equation

Definition(s)

Darcy Equation

Mathematical relationship used to determine a simple system curve. Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Cyclic Surging

Cyclic Surging

Definition(s)

Cyclic Surging

Small surges of pressure that oscillate within the line or vessel; cyclic surges are associated with line or vessel equipment, such as reciprocating pumps/compressors and pressure reducing valves. Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Cup Tester or Cup Packer

Cup Tester or Cup Packer

Definition(s)

Cup Tester or Cup Packer

Device lowered into the well on a drill stem to pressure test casing and blowout preventers. The sealing component is cup – shaped, hence the name. Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Critical Zone

Critical Zone

Definition(s)

Critical Zone

see: critical flow Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Critical Velocity

Critical Velocity

Definition(s)

Critical Velocity

Speed to maintain turbulent flow and prevent transition to laminar flow. Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Critical Pressure Differential

Critical Pressure Differential

Definition(s)

Critical Pressure Differential

Difference between the pressure at the valve inlet and at the vena contracta that would cause cavitation. Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Critical Point

Critical Point

Definition(s)

Critical Point

Location on a line or vessel that determines the rate at which the fluid in the line or vessel can flow. Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Critical Flow

Critical Flow

Definition(s)

Critical Flow

fluid flow that is unstable, alternating between laminar and turbulent flow; Critical flow occurs at Reynolds numbers between 2000 and 4000. Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Cooling

Cooling

Definition(s)

Cooling

Process to lower the temperature of the fluid. Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Control Valve

Control Valve

Definition(s)

Control Valve

Valve position determined by a control system based on a set point. Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Control System

Control System

Definition(s)

Control System

System where a comparison between a measured control variable a set point prompts an action to achieve the set point. Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Control Panel – Remote or Secondary

Control Panel – Remote or Secondary

Definition(s)

Control Panel – Remote or Secondary

A system of controls usually convenient to the driller, used to actuate controls at the Master or Primary panel. Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Control Panel, – Master or Primary

Control Panel, – Master or Primary

Definition(s)

Control Panel, - Master or Primary

A manifold system of valves which is usually situated at the power source, which may be operated manually or by remote control, to direct pressurized fluids to well closing . Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Constant Choke Pressure Method

Constant Choke Pressure Method

Definition(s)

Constant Choke Pressure Method

The adjustment of choke size to maintain constant casing pressure. Used in well killing operations where the influx is composed of water, does not work with gas due to expansion of the gas as it rises up the wellbore. Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Constant Bottom Hole Pressure (CBHP)

Constant Bottom Hole Pressure (CBHP)

Definition(s)

Constant Bottom Hole Pressure (CBHP)

Methodology within MPD, Proactive Category; whereby bottomhole pressure is kept constant during connections to compensate the loss of AFP when mud pumps are off. Typical methods include:
  1. By keeping     continuous     circulation     during
  2. By trapping annular pressure prior to shutting down mud
  3. By diverting mud pump flow across the wellhead
Source: IADC UBO / MPD Glossary, December 2011. Global Standards
Connection Gas

Connection Gas

Definition(s)

Connection Gas

The small amount of gas that enters a well after stopping the mud pumps for a connection. Source: IADC UBO / MPD Glossary, December 2011. Global Standards