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Drafting

Process of delivering more gas than is presently entering the system. Source: IADC UBO / MPD Glossary, December 2011. Global Standards

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Down Surge

Line or vessel pressure surge, which is negative because its magnitude is below the normal operating pressure of the line or vessel. Source: IADC UBO / MPD Glossary, December 2011. Global Standards

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Downhole Pumping MPD

A pump of some design is used downhole to apply upward lift to annulus returns; to offset annulus friction pressure when circulating, to return riserless drilled mud and cuttings to the rig, or mid riser to reduce the hydrostatic head of mud and cuttings in ultra-deep water. Source: IADC UBO / MPD Glossary, December 2011. Global Standards

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Displacement Meter

A type of meter that measures flow based on the physical displacement of fluid. Source: IADC UBO / MPD Glossary, December 2011. Global Standards

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Discharge Valve

OPEN/CLOSED valve, such as a gate valve or a ball valve, that allows or disallows fluid from leaving a pump or compressor. Source: IADC UBO / MPD Glossary, December 2011. Global Standards

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Discharge Set Point

The set limit for discharge pressure allowed to exit the station. Source: IADC UBO / MPD Glossary, December 2011. Global Standards

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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

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Discharge Pressure

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

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Discharge Nozzle

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

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Discharge Control

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

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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

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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

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Determined Viscosity

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

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Design Capacity

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

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Densitometer

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

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Dehydrator

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

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Dehydration

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

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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

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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

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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

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Darcy Equation

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