Discover the IHRDC Energy Glossary_beta

m

The cementation exponent in Archie's equation, relating formation factor to porosity, typically near 2.

M f

Methyl orange filtrate alkalinity — the total alkalinity of a mud filtrate, titrated to the methyl orange endpoint.

m-learning

Learning delivered on mobile devices, designed for short sessions and small screens.

Ma

Mega-annum — millions of years, used for an age before present in geological literature.

maceral

The microscopic organic constituent of coal or kerogen, whose type predicts oil or gas.

macerals

The organic constituents of coal and source rock, whose type determines what hydrocarbons form.

machine

A device that uses applied forces advantageously to perform work.

machine learning

Algorithms that infer patterns from data instead of following rules written in advance.

machine learning (ml)

Methods that fit models to data so they can recognize patterns and predict, without the rules being written out explicitly.

machine learning operations (MLOps)

The practice of managing a model's whole life cycle — deployment, monitoring, retraining — as an engineering discipline, abbreviated MLOps.

macroscopic

At a scale visible without magnification, as distinct from pore scale.

mafic

Describing igneous rocks and minerals rich in magnesium and iron, and therefore dark and dense.

magma

Molten rock beneath the Earth's surface, which cools at depth as intrusive rock or erupts as lava.

magnesium test

The determination of magnesium in a mud filtrate by subtracting the calcium titration from the total hardness titration.

magnetic constant

The magnetic permeability of free space, used as the reference value in electromagnetic calculations.

magnetic controller

A motor controller in which control functions are performed by electromagnetic switches.

magnetic field

A portion of space or area within which magnetic forces produced by a magnet or a current-carrying conductor can be detected; the lines of force surrounding a permanent magnet or a moving charged particle.

magnetic flux

The magnetic field passing through a region, which links windings and produces voltage.

magnetic lines of flux

Lines used to represent a magnetic field.

magnetic moment

Magnetic moment is the property of a magnet that interacts with an applied field to give a mechanical moment.

magnetic mud

A mud whose magnetic susceptibility is high enough to disturb magnetic measurements made through it.

magnetic overload device

A type of overload device that operates on the magnetic field produced by current.

magnetic particle inspection (MPI)

A nondestructive test in which iron particles gather at the flux leakage from a surface crack in a magnetized component, abbreviated MPI.

magnetic permeability

The ratio of magnetic flux density to magnetizing field strength in a material, in henries per meter.

magnetic pickup

A feedback device that senses the movement of motor shafts or machinery parts and provides a feedback signal to a variable speed controller.

magnetic resonance

Magnetic resonance is a phenomenon by which a nucleus absorbs electromagnetic radiation of a specific frequency in the presence of a strong magnetic field.

magnetic resonance imaging log (MRIL)

The Magnetic Resonance Imaging Log (MRIL) is the proprietary nuclear magnetic resonance (NMR) logging service developed by Numar, a company subsequently bought by Halliburton.

magnetic reversal sequence

The record of the Earth's magnetic field switching polarity, dated and ordered into a global time scale.

magnetic susceptibility

How readily a rock is magnetized, measured to identify lithology and correlate cores.

magnetic toolface

Toolface measured clockwise from magnetic north, used where the hole is too near vertical for a gravity high side to be defined.

magnetic total field

The magnitude of the total magnetic field vector, regardless of its direction.

magnetic-flux leakage

The flux that escapes from magnetized casing at a defect, detected by sensors to locate pits and holes.

magnetics

The study of the Earth's magnetic field and of the anomalies caused by magnetic minerals in the subsurface.

magnetism

How materials respond on the microscopic level to an applied magnetic field; to categorize the magnetic phase of a material.

magnetite

An iron oxide used as a weighting material and detected in magnetic surveys.

magnetization

The magnetic moment induced in a material, exploited in nuclear magnetic resonance logging.

magnetizing current

Current required by an induction motor; used to create a magnetic field in the motor.

magnetometer

An instrument used for measuring magnetic forces, especially the Earth's magnetism.

magnetostratigraphy

Dating and correlating strata by their recorded magnetic polarity reversals.

magnetostrictive material

A magnetostrictive material consists of tiny ferromagnets.

magnetotelluric method

An electromagnetic method mapping subsurface resistivity from naturally occurring electric and magnetic field variations measured at surface.

main condenser

The exchanger condensing turbine exhaust steam, whose vacuum sets cycle efficiency.

main fractionator

The area of a cat cracking unit where hot cracked gas from the reactor is separated into different fractions.

main inlet

The plant's principal feed connection, as distinct from recycle or utility inlets.

main magnetic field

The Earth's own magnetic field, generated by dynamo action in the fluid outer core.

main steam stop valve

A specially designed, hydraulic cylinder operated valve that stops the flow of steam to the turbine to prevent possible damage.

main steam system

A system of pipes and valves that directs and controls the flow of steam from the boiler to the turbine.

main transformer

The transformer connecting a generator or plant to the system.

maintenance and reliability programme

The planned work keeping equipment available and preventing unplanned failure.

make a connection

To add a joint or stand of pipe to the drillstring so drilling can continue deeper.

make hole

To deepen the wellbore — to drill ahead.

make up

To assemble and tighten a threaded connection to its specified torque.

makeup catalyst

Catalyst that is continually added to maintain desired yields and conversion and to make up for catalyst lost in the cracking process.

makeup cathead

A clutched spool driven off the drawworks that pulls the chain on the makeup tongs to tighten a connection.

makeup gas

Gas added to a system from outside to make up a shortfall — in a gas lift system, when separator gas alone is insufficient.

makeup tongs

Large self-locking wrenches that grip a tubular and apply the torque needed to make up a connection.

makeup water

Water added to a cooling tower's catch basin to maintain the proper level.

makeup water system

The support system that adds water to the steam cycle to replace water and steam lost as a result of leakage.

malaria

A disease caused by a parasitic protozoan that is usually transferred to the human bloodstream by a mosquito. It is characterized by attacks of chills, fever and sweating. Malaria destroys red blood cells.

male-female flange

A flange similar to the tongue-and-groove. The female part of one flange half is formed in a raised area around the center opening into which the male part of the other flange half fits.

mallet

A short-handed hammer, usually with a cylindrical wooden, rubber, plastic, or rawhide head, used for striking a chisel.

malware

Software written to damage, disrupt or gain unauthorized access.

managed pressure drilling

An adaptive drilling process that controls the annular pressure profile precisely, holding it within close tolerances the length of the well.

Management by Objectives (MBO)

Managing by agreeing measurable objectives and reviewing against them, rather than directing activity.

management control

The limits, reporting and segregation of duties that keep a trading desk within mandate.

management of change (MOC)

The formal process ensuring a modification is reviewed for safety and integrity before it is made.

management plane

The interface controlling cloud resources, whose compromise means losing everything at once.

management reorganization

Restructuring the management layer, usually to change cost, control or direction.

management vs. leadership

The distinction between running existing arrangements well and setting a new direction.

managerial coaching

Coaching by the person who also directs and appraises, which requires separating the two roles.

managerial mindset

The shift from valuing one's own output to valuing what the team produces.

mandatory training (formerly known as compliance)

A function in CMS Online used to assign and track required training across all business locations and functions. Certain training, such as Health, Environment and Safety courses, may be required by the organization, and in some cases may be required as a result of government mandate.

mandrel

A bar, shaft, spindle, or tapered tool around which other components are arranged or assembled. In riveting, the shank of a rivet.

manifold

A system of tubing attached to the main pipe that may divide flow, combine flows or reroute a flow.

manifold valve

A valve on a manifold, routing one of several streams.

manipulated variable

The variable in a process that is adjusted or manipulated by the final control element to keep the controlled variable at set point.

manometer

A basic instrument used to measure and indicate pressure or vacuum in terms of the height of a column of liquid.

manometers

Instruments that are used to measure condenser vacuum.

manpower planning

Forecasting how many people with which skills will be needed, and when.

mantle

The layer of the Earth between the crust and the core, about 2,900 km thick and divided into upper and lower mantle.

manual bypass

A hand-operated route around a device, allowing service without shutting the process down.

manual control

A basic form of process control in which an operator monitors process variables and then makes manual adjustments to an output device to modify the process.

manual trip

A mechanism that allows operators to stop, or trip, a system manually.

manufacturer instruction

The maker's stated method for operating or maintaining equipment.

manufacturer recommendation

The maker's advised practice, which warranty and insurance both refer to.

manufacturer specification

The values the maker states equipment must be operated and maintained within.

manway

A covered access port on a tank that can be opened to allow workers to enter the tank for cleaning, repairs, and inspections; also called a manhole.

manway cover

The removable cover over a vessel access opening.

map

A scaled representation on a plane surface of the features of a part of the Earth's surface or of a subsurface horizon.

marcellus

The Appalachian shale that is the largest single United States gas source.

marcellus shale

The Appalachian formation that is the largest single source of United States natural gas.

marginal field

A discovery too small for a major to develop, offered to indigenous companies instead.

marginal marine

Deposited at the boundary of land and sea, giving rapidly changing facies.

marginal well

A well near the limit of economic production, whether through depletion or naturally low deliverability.

marine

Pertaining to the sea — its environments, sediments and organisms, from low tide to the ocean floor.

marine drilling riser

The large-diameter pipe connecting a subsea BOP stack to a floating rig, returning mud to surface and guiding the string.

marine flooding surface

A surface across which water depth increases abruptly, separating shallower strata below from deeper marine strata above.

marine sediment

Sediment deposited in the sea.

marine sedimentary rock

Marine sedimentary rock is any deposit of insoluble material transported from land areas to the ocean by wind, ice and rivers, as well as the remains of marine organisms, products of submarine volcanism and chemical precipitates from seawater that accumulates on the seafloor.

marine seismic

Seismic acquired at sea, with airgun sources and towed receiver streamers.

marine shale

Shale deposited in the sea, often the source rock of a petroleum system.

marker bed

A distinctive, widespread bed that can be recognized and correlated over a large area.

marker crude

A widely traded crude whose price serves as the reference for pricing others.

marker crude oil

A widely traded crude whose price serves as the reference for others.

marker joint

A joint of distinctive length or profile placed in a string to serve as a depth reference for later operations.

marker price

The published price of a benchmark grade against which others are set.

market acceptance

Whether the market actually buys, as against saying it would.

market intelligence

Knowledge of supplier capacity, pricing and appetite gathered before tendering.

market segmentation

Dividing a market into groups that respond differently, so each can be addressed properly.

market structure change

A shift between contango and backwardation, which can reverse a storage trade mid-position.

marketable product

A stream meeting specification and therefore saleable.

marketer

An intermediary buying and reselling gas or products rather than producing them.

marketing agreement

A contract under which one party sells another's production and passes on the proceeds, less an agreed fee.

marketing automation

Software that executes campaigns and follow-up according to defined rules.

marketing email

Email sent to prospects or customers, subject to consent rules and measured on response.

Marketing mix (the Four Ps)

Product, price, place and promotion, the levers a marketer controls.

marketing planning process

The sequence from analysis through objectives and strategy to programs and control.

marketing strategy

The chosen approach to creating and capturing value in a market.

marketscan

A Platts daily price report covering a regional product and crude market.

marking to market

Revaluing open positions at current prices so unrealized gains and losses are visible daily.

markings

Labelling information that is printed on packaging to identify the contents of the packaging.

Markov model

A Markov model is a stochastic method for randomly changing systems where it is assumed that future states do not depend on past states.

marl

A sedimentary rock of mixed clay and calcium carbonate, intermediate between shale and limestone.

marsh

A permanently or frequently wet lowland supporting grassy vegetation, which does not accumulate peat.

Marsh funnel

A conical funnel with a fixed-bore outlet used to time the flow of a set volume of mud, giving funnel viscosity in seconds.

Marsh funnel viscosity

The time in seconds for one quart of mud to run out of a Marsh funnel.

mask

A pattern of bits (often expressed in hexadecimal) that acts as a filter to determine which bits in a data word are used or acted upon by an instruction.

mass

The amount of matter an object possesses. In measurement, the weight of a product corrected for air buoyancy.

mass flowmeter

A meter measuring mass directly rather than volume, so no density correction is needed.

mass measurement

A method for measuring the quantity of NGLs by multiplying volume by density without needing to correct for temperature and pressure.

mass spectrometer

An analytical device that measures and identifies components in a multi-component mixture by measuring the deflection of ionized particles as they pass through a magnetic field.

mass spectrometry

Identifying compounds by sorting their ionized fragments by mass.

massif

A large rigid block of rock that has moved as a unit and stands out structurally or topographically.

mast

A movable support structure on some types of cranes that provides a connection point for the boom pendant lines and boom hoist lines.

mast unit

A well servicing unit carrying its own mast, so it can lift and run tools without a separate crane or gin pole.

master (static) budget

The consolidated budget for the whole organization at a single planned activity level.

master calibration

Master calibration is the regular calibration of a logging tool in the workshop, usually monthly or quarterly. These are run to ensure that the tool is operating within the tolerances of the calibration coefficients from the primary calibration.

master meter factor

The calibrated number of pulses per unit volume.

master meter prover

A meter, usually a turbine meter, which is used to check the measuring accuracy of a NGL meter.

master production schedule

The plan of what will be produced, in what quantity, and when.

master valve

The valve on a Christmas tree that controls all flow from the well, closed to isolate everything above it.

mastery (competency level 4)

Has thorough understanding of activity or process / Has detailed knowledge of the industry standards, trends and best practices / Is regarded as an expert and final decision-maker / Develops new procedures, modifies existing methods and sets policy / Manages team and coordinates work.

mastery quiz

An assessment a learner must pass to proceed, usually retakeable.

material balance

An accounting statement that mass entering a system equals mass leaving it plus mass accumulated within it.

material balance equation

The reservoir engineering expression of conservation of mass, relating cumulative production to fluid expansion, influx and pressure decline.

material balancing

A method of calculating how much of each raw material is needed to produce a desired product.

material misstatement

An error in the accounts large enough to matter, the thing an audit is designed to detect.

material safety data sheet

A document that identifies a specific material and provides information on exposure limits, physical and chemical characteristics, the nature of hazards, precautions for safe handling and use, protective equipment requirements, first aid procedures, storage and handling precautions, and spill/leak/disposal practices.

material safety data sheet (MSDS)

A document containing information about the identity of a hazardous material, its physical and chemical characteristics, the nature of its hazards, safe handling procedures, health effects and treatment, clean-up instructions, and other safety information.

materiality

The threshold above which an error or omission would change a reader's decision.

materiality assessment

Determining which issues matter enough to the business and its stakeholders to be reported.

maternity and paternity leave

Leave around the birth or adoption of a child.

mathematical model

A set of equations standing in for the physical system, solved instead of it.

matrix

In catalysis, materials that support zeolite crystals and provide shape and bulk to a catalyst particle. In geology, the finer-grained mass of material in which larger grains, crystals, or clasts are embedded within a rock.

matrix acidizing

Acid treatment below fracture pressure, so the acid enters the pore system and dissolves damage near the wellbore.

matrix block

A block of unfractured rock between fractures, which stores the fluid the fractures carry away.

matrix density, grain density

Matrix, or grain, density is the density of the minerals forming a rock, often referred to in core analysis as grain density.

matrix permeability

The permeability of the unfractured rock.

matrix porosity

The porosity determined from a small sample of a rock core, in contrast to total porosity, where the whole core is used.

matrix stimulation

A treatment aimed at the near-wellbore formation rather than at the wellbore or the production conduit.

matter

Anything that has weight (mass) and occupies space.

maturation

The thermal conversion of organic matter in a source rock into hydrocarbons as burial temperature rises.

maturation level

How far the conversion of organic matter has progressed.

maturity

How far a source rock has progressed through thermal conversion — immature, mature or overmature for the hydrocarbon of interest.

MAWP

Maximum Allowable Working Pressure.

maximum boiling point azeotrope

An azeotrope that boils at a temperature that is above the boiling points of its components.

maximum flooding surface

The surface marking the greatest landward extent of marine influence, separating the transgressive systems tract below from the highstand tract above.

maximum fork height

The distance from the floor to the forks of a forklift when the forks are raised to full mast extension.

maximum horizontal stress

The larger horizontal stress, whose direction fixes the plane a fracture will follow.

maximum operating temperature

The highest final operating temperature at which a conductor can operate without overheating.

maximum peak output voltage

The maximum peak-to-peak output voltage that can be obtained without clipping when the op-amp is operated from a bipolar supply.

maximum recorded temperature

The highest temperature reached during a logging run, recorded by a maximum-reading thermometer on the tool string.

maximum treating pressure

The surface pressure limit a treatment must stay below, set by the weakest element in the pressurized system.

maximum working pressure (MWP)

The maximum pressure the compressor can handle while operating continuously.

maximum-output-swing

The range of frequencies within which the maximum output voltage swing is above a specified value or the maximum frequency of an amplifier in which the output amplitude is at the extents of its linear range. Also called full power bandwidth.

Maxwell's equations

The four partial differential equations — Faraday's law, Ampere's law and the two Gauss laws — that describe classical electric and magnetic fields.

MBBL

One thousand barrels of crude oil, bitumen, condensate or natural gas liquids.

MBD

One thousand barrels per day.

MBOE

One thousand barrels of oil equivalent.

MBT test

The methylene blue titration, which measures how much dye a mud sample adsorbs and so how much reactive clay it holds.

MCF

One thousand standard cubic feet of natural gas. In the United States, standard conditions are defined as gas at 14.7 psia and 60oF.

MD

Measured depth — the distance along the wellbore from the surface reference, as against true vertical depth.

mean

The arithmetic average of a set of values — their sum divided by their count.

mean cell residence time

The amount of time that the average micro-organism, or bug, spends in an activated sludge system before it is removed.

mean square dip (MSD)

Mean square dip (MSD) uses all 28 possible cross correlations from an eight curve dipmeter tool to compute 28 displacements.

mean, median, mode

The average, the midpoint and the most frequent value, which diverge in skewed data.

meandering

Of a river that migrates sideways in loops, leaving isolated point-bar sands.

meandering stream

A river migrating sideways in loops, leaving point-bar sands within floodplain mud.

measure point

The point on a logging tool that the recorded measurement is referenced to, at the center of its vertical response.

measured depth

The distance along the wellbore from the depth reference, as though measured with a tape down the hole.

measured variable

The physical quantity, property, or condition that is measured to determine the actual condition of a controlled variable.

measurement accuracy

How close a measured quantity is to the true one, which custody contracts state a tolerance for.

measurement after drilling

Logging data recorded by measurement-while-drilling sensors on a later pass, rather than as the bit first cuts the formation.

measurement chamber

The fixed volume a positive-displacement meter fills and empties to count throughput.

measurement data

The pressures, temperatures and volumes a measurement is computed from.

measurement device

The instrument making a measurement.

measurement equipment

The meters, recorders and provers making up a measurement installation.

measurement error

The difference between a measured value and the true value, from instrument limitations, noise or the act of measuring itself.

measurement range

The span of values over which an instrument's error stays within its specified limits.

measurement unit

The unit a quantity is expressed in.

measurement while drilling

Measurements taken downhole with an electromechanical device located in the bottom hole assembly. All MWD systems typically have three major subcomponents: power system, telemetry system, and directional sensor.

measurements-while-drilling

Downhole measurement of wellbore trajectory, and usually pressure and temperature, taken while the hole is being drilled.

measures of performance

The standard set of economic indicators reported together, since no single one is sufficient.

measuring chamber

The fixed volume a positive-displacement meter fills and empties to count flow.

measuring device

The instrument taking a measurement.

measuring tank

A calibrated tank used to measure produced liquid volume, by gauging the change in level over a period.

measuring tape

A flexible graduated tape for measuring length.

mechanical advantage

The advantage gained in transmitting force through the use of a machine; the ratio between resistance force and applied force.

mechanical compaction

Porosity loss by grains packing more tightly under load, before any cementation.

mechanical connector or terminal

A connector or terminal that is installed by tightening a bolt or setscrew to clamp the connector or terminal onto a conductor.

mechanical diversion

Diverting a treatment with hardware — ball sealers, packers or straddle assemblies — rather than with chemical diverting agents.

mechanical float switch

In a single-point level detection system, an electrical switch that is operated by the mechanical action of a linkage and a float rod.

mechanical interlock

An arrangement of components intended to prevent energizing an electrical device in a way that could damage it or that could be unsafe.

mechanical jar

A jar released by a mechanical trip mechanism at a preset load, rather than by a hydraulic delay.

mechanical leak

Leakage past a seal, gasket or joint rather than through a wall.

mechanical linkage

The rods and levers transmitting motion between components.

mechanical operator

An electric, hydraulic, or pneumatic device that is used to open and close a valve.

mechanical seal

A device composed of a rotating element and a stationary element used to seal between a rotating shaft and a stationary housing (such as a pump casing) with virtually no leakoff.

mechanical skin

The component of skin caused by physical restriction near the wellbore — partial completion, perforation geometry or debris — rather than by permeability damage.

mechanical specific energy

The mechanical energy needed to remove a unit volume of rock, abbreviated MSE.

mechanical sticking

Sticking of the drillstring by physical obstruction — settled cuttings, sloughing shale, junk or a keyseat — rather than by differential pressure.

mechanical stratigraphy

The layering of rock strength, which controls where a fracture stops rather than where the geology changes.

mechanical-draft cooling tower

A cooling tower in which air is moved through the tower by fans.

mechanics of oil trading

The practical sequence of a deal: negotiation, nomination, pricing, documentation and settlement.

media

The physical connection or cable used for PLC network connections between nodes on a network.

median

The middle value of an ordered dataset — the value at 50% cumulative probability.

mediation

A neutral third party helping disputants reach their own agreement.

medical consultation

A consultation that takes place between an employee and a licensed physician for the purpose of determining what medical examinations or procedures, if any, are appropriate in cases where a significant exposure to a hazardous chemical may have taken place.

medical marijuana card

State authorization for medical cannabis, which complicates workplace drug policy.

medium

In the strict API sense, a particle in the 74 to 250 micron size range.

medium distillate

The kerosene and gasoil range between naphtha and residue.

medium induction

The intermediate-depth curve of an induction tool, reading between the shallow and deep measurements.

medium sour

Crude of intermediate density with appreciable sulfur.

medium sour crude

Crude of intermediate density with appreciable sulfur.

medium/heavy sour

Crude that is dense and high in sulfur, requiring conversion capacity.

meeting agenda

The circulated list of items and intended outcomes, without which meetings drift.

meeting minutes

The record of decisions and actions, distinguished from a transcript of discussion.

mega-methanol plant

A methanol plant built at very large scale to exploit low-cost gas.

megahertz

1,000,000 hertz; a unit of frequency.

megawatt (MW)

One million watts.

megawatt-hour (MWh)

One million watt-hours.

Megger

A trademarked term commonly used to indicate the procedure of measuring the insulation resistance of a motors windings.

megohmmeter

An instrument applying high voltage to measure insulation resistance in megohms.

melting point

The temperature a solid becomes liquid at.

membrane potential

The electromagnetic force generated across an ion-selective membrane when solutions on either side of the membrane have different salinities.

memo

A short internal document conveying one matter to a defined readership.

memory gauge

A downhole pressure gauge that records to internal memory rather than transmitting to surface.

memory gauge investigations

Memory gauge investigation refers to memory operations that store the acquired data/images for later review, as opposed to real-time operations when the data/image is immediately available for review.

memory map

A graphical representation of the memory model of a microprocessor.

meniscus

The curve in the upper surface of a liquid close to the surface of the container or another object, caused by surface tension. It can be either convex or concave, depending on the liquid and the surface.

mental health initiative

An employer program addressing psychological health directly rather than by implication.

mental lift

A planning session in which the load's size, weight, contents, location, and destination are considered before the load is lifted.

mental models of negotiation

The assumptions a negotiator brings, such as whether the pie is fixed.

mentor

A person assigned to assist an employee with their professional development. Based on the Competency Development Plan configuration chosen by the client, the Mentor can play a role in building and/or assessing the plan.

mentor-facilitated workshop

A session where an experienced practitioner guides teams and receives their decisions at gates.

mentoring

mentorship

A relationship in which an experienced person guides another's development.

mercaptan (RSH)

A slightly acidic organic compound containing sulfur and hydrogen.

mercury displacement method

Measuring a core plug's bulk volume from the mercury it displaces when pushed into a filled chamber.

mercury switch

A switch consisting of a glass vial that contains a pool of mercury and a set of contacts; a circuit is completed when the mercury covers the contacts and broken when the vial tips and the mercury no longer covers the contacts.

mergers, acquisitions and spin-offs

Changing what a company owns through corporate transactions rather than through projects.

mesozoic

The era whose strata host a very large share of world reserves.

metagenesis

The highest-temperature stage of organic matter alteration, in which kerogen, bitumen and oil break down to methane and pyrobitumen.

metal bellow

A metal corrugated element accommodating movement while containing pressure.

metal gain

An apparent increase in casing or tubing wall thickness on an inspection log, above the nominal value assumed.

metal loss

The reduction of casing or tubing wall thickness by corrosion or erosion, on the inside or outside.

metal oxide semiconductor field effect transistor

A type of IGFET that has a gate that is insulated from the transistor body by a thin layer of metal oxide.

metal oxides

Contain a metal cation and the oxide anion 02.

metal-to-metal seal

A seal formed by metal surfaces pressed directly together, without an elastomer between them.

metamorphic

Metamorphic rocks are a category of rocks that arise from the transformation of existing rocks into new rock types, which are generated by high temperatures and pressures that cause profound physical or chemical changes and result in new textures and mineral compositions. Common metamorphic rocks include schist, gneiss, slate, quartzite and marble.

metamorphic rock

Rock recrystallized by heat and pressure, which holds no primary porosity.

metamorphism

The alteration of a rock's mineralogy and texture by heat, pressure or chemically active fluids, without melting.

meteoric

Derived from rainfall, said of water that has entered the subsurface from surface.

meteoric water

Water that entered the subsurface as rainfall, which dissolves carbonate and can create secondary porosity.

meter

A device that measures the volume or rate of a flowing fluid.

meter calibration

Checking a meter's reading against a known standard and correcting it to bring the error within acceptable limits.

meter capacity

The range of flow rates between which a meter will read within its stated accuracy.

meter difference

The discrepancy between the volumes registered by two meters measuring the same stream.

meter factor

The correction to volume measurement attributable to variations in fluid viscosity, flow rate or meter wear.

meter movement

The device in an analog display that converts the flow of current into the mechanical motion of the pointer.

meter proving

The process of checking a flow meter against another calibrated device, either a prover or master meter.

meter range

The pressure, temperature and viscosity variation specified for a meter by the manufacturer.

meter slippage

The fluid that passes a positive displacement meter through its internal clearances without being counted.

meter witnessing

The process of being present when an orifice meter is being checked and calibrated.

meter-in circuit

A flow control circuit that controls the amount of fluid going to an actuator by restricting flow directly between the pump and the actuator.

meter-out circuit

A flow control circuit that controls the amount of fluid returning from an actuator.

metering

Measuring flow quantity, usually for custody or control.

metering device

The element that measures flow, whose accuracy the whole custody chain rests on.

metering station

The skid carrying meters, provers and instruments at a custody point.

meth

A prefix for the name of a hydrocarbon that has one carbon atom.

methane

A one-carbon compound (CH4) in which the carbon is attached by single bonds to four hydrogen atoms. It is a colorless, odorless, non-toxic but flammable light gaseous paraffin hydrocarbon that is the chief component of natural gas.

methane emission

Released methane, far more warming per tonne than carbon dioxide over twenty years.

methane emissions management

Measuring and reducing methane released through venting, flaring and leaks.

methane ethane propane

The successive light hydrocarbons separated in gas processing.

methane hydrate

A crystalline solid in which methane molecules are caged within a lattice of water ice, stable at low temperature and high pressure.

methane reforming smr

Steam methane reforming, the dominant industrial hydrogen route.

methanol

A liquid alcohol injectant used for three purposes: To dissolve hydrates, to inhibit hydrate formation and to remove water from a natural gas stream.

methanol price

The market price of methanol, driven by gas cost and chemical demand.

methyl group

A single carbon with three hydrogens attached to a larger molecule.

methyl orange

A pH indicator that changes color near pH 4, used to reach the final endpoint in alkalinity titrations.

methyl orange alkalinity

The total alkalinity of a mud filtrate, from titration with acid to the methyl orange endpoint at about pH 4.3, reported as Mf.

methylene blue

A dye used in the test measuring reactive clay content in drilling fluid.

methylene blue dye

A cationic blue dye that adsorbs onto clay surfaces in proportion to their exchange capacity, used as the reagent in the methylene blue test.

methylene blue test

A titration measuring how much methylene blue dye a mud takes up, as an indicator of its reactive clay content.

methylglucoside drilling fluid

A water-base mud carrying a high concentration of methylglucoside, a sugar derivative that inhibits shale hydration.

metric

A standard against which results can be measured.

metric system

The world standard system of measurements in which all units are multiples of ten; includes meters, centimeters, and millimeters.

metrics vs. KPIs

Everything that can be measured, against the few measures actually being managed.

MFFI

The free fluid index in NMR log interpretation. In Halliburton's terminology, MFFI has been used as the abbreviation for the free fluid index.

mgal

The milligal, the unit in which gravity anomalies are measured.

MGO (Marine Gas Oil)

A distillate marine fuel, cleaner and dearer than residual fuel oil.

mho

A basic unit of electrical conductivity, the reciprocal of an ohm, used to describe a substance's ability to conduct current. Usually expressed in readings as micromhos.

mica

The mica group of sheet silicate (phyllosilicate) minerals includes several closely related materials having nearly perfect basal cleavage.

micellar-polymer flooding

An enhanced recovery process injecting a surfactant micellar slug to mobilize residual oil, followed by polymer to control the mobility behind it.

micelle

An ordered cluster of surfactant molecules that forms once concentration passes a critical point, hiding the insoluble ends inside.

micrite

Fine-grained carbonate mud, and the rock made of it, formed by breakdown of larger grains or by direct precipitation.

micro porosity, microporosity, micropores

A micro porous formation is one containing pores with diameters less than 2 nm.

micro-imager

A pad tool making a fine-resolution resistivity image of the borehole wall.

micro-induction sensors

A micro-induction sensor is a device that uses the principle of electromagnetic induction (a current produced because of voltage production (electromotive force) resulting from a changing magnetic field) to detect or measure objects.

micro-organisms

Extremely small plants and animals, such as algae and bacteria, that can contaminate water systems including cooling towers.

micro-porosity

Micro-porosity is that part of the pore space that has a characteristic dimension less than 1 micron.

microannulus

A very narrow gap between casing and its cement sheath, wide enough to break the acoustic bond and sometimes to allow flow.

microbe

A single-celled organism, here the agent doing the work in fermentation and digestion routes.

microbial fermentation

Producing hydrogen by feeding organic matter to bacteria, slow but tolerant of wet waste.

microcylindrical log

A pad microresistivity device with cylindrically focused electrodes, reading the flushed zone just past the mudcake.

microearthquake

A very small natural or induced seismic event.

microemulsion

A thermodynamically stable mixture of oil, water and surfactant that forms spontaneously and remains clear.

microfossil

A fossil or fossil fragment that can only be seen with a microscope; the preserved remains or traces of animals, plants, and other organisms visible only under magnification.

microfossils

Microfossils are fossils or fragments that can only be seen with a microscope.

microgal

The microgal, (\( \mu \)gal), is one millionth of a gal.

microgel

A partly hydrated polymer particle too small to see, small enough to enter pore throats and plug them.

microlaterolog

A pad-mounted focused electrode device with very small spacings, reading the flushed zone immediately behind the borehole wall.

microlearning

Delivers targeted right-sized nuggets of information when and where employees need and want it. It can take different forms, from text to interactive multimedia. Smaller learning sessions provide all the information necessary for learners to achieve a specific training objective quickly, making microlearning valuable in business contexts.

microlog

An unfocused pad device with two very short spacings, whose curves separate opposite permeable beds where mudcake has built.

micrometer

A type of precision caliper used for making accurate measurements to the nearest thousandth or ten-thousandth, using a combination of a fixed scale and a rotating scale.

micrometers

1 meter = 1 million micrometers.

micron

One millionth of a meter, the scale pore throats and clay particles are measured on.

microns

Micrometres, the scale at which pore throats and filtration are measured.

microorganism

Any organism too small to be viewed by the unaided eye, such as bacteria, protozoa, and some fungi and algae.

micropalaeontology

Micropalaeontology is the study of very small fossils under a microscope.

micropaleontology

Micropaleontology is a branch of paleontology that studies microfossils, fossils so tiny a microscope must be used to view them.

microprocessor

The programmable logic device at the heart of modern instruments and controllers.

microresistivity

Microresistivity is the resistivity related to the flushed/invaded zone immediately adjacent to the borehole wall.

microresistivity tool

A pad-mounted tool measuring the resistivity of the flushed zone close to the wall.

microresistivity, micro resistivity

Microresistivity is related to a log of the resistivity of the flushed zone recorded by a wireline electrode device. The device is mounted on a pad and pressed against the borehole wall. Several designs exist, for example microlog, microlaterolog, proximity log, microspherically focused log.

microresistivity, micro resistivity, micro-resistivity

Microresistivity is related to a log of the resistivity of the flushed zone recorded by a wireline electrode device. The device is mounted on a pad and pressed against the borehole wall. Several designs exist, for example microlog, microlaterolog, proximity log, microspherically focused log.

microsecond

A unit of time equivalent to 0.000001 seconds.

microseismic

Very small induced seismic events, located to map where a hydraulic fracture went.

microseismic event

A tiny rock failure detected during stimulation, from which fracture growth is mapped.

microseismic monitoring

Locating the tiny seismic events generated by rock failure, to map where a hydraulic fracture or a producing reservoir is deforming.

microseismic survey

Recording the small events induced by stimulation to map where the fractures went.

microspheres

Extremely fine particles that make up the catalyst used for fluid catalytic cracking.

microspherical log

A pad microresistivity device with spherically focused electrodes, measuring flushed zone resistivity with minimal mudcake effect.

microstructure

Rock texture at the scale of grains and pores.

microwave

A microwave is an electromagnetic wave with a wavelength in the range 0.001–0.3 m, shorter than that of a normal radio wave but longer than those of infrared radiation.

microwave channel

A transfer trip communication channel that uses microwaves to send transfer trip signals from one substation to another.

middle distillate

The kerosene and gasoil cuts between naphtha and residue.

middle-time transient data

The part of a well test response after wellbore storage has died out and before boundaries are felt — infinite-acting radial flow.

midoceanic ridge

The submarine mountain chain along a divergent plate boundary, where new oceanic crust is created as magma rises and cools.

midpoint

The surface point halfway between a source and a receiver.

midrange

The value halfway between the smallest and largest in a dataset, or the middle of an instrument's span.

midstream

Transport, storage and processing between the wellhead and the refinery or end market.

Midstream and Downstream Gas Infrastructure Fund

The Act's fund for investment in domestic gas infrastructure.

midstream company

A business owning transport, storage or processing assets rather than reserves.

midstream gas

Gas gathering, processing and transport between the wellhead and the market.

midstream gas sector

The gathering, processing and transport of gas between wellhead and market.

midstream sector

The part of the industry between production and refining.

migrate

Of hydrocarbons, to move out of a source rock and through carrier beds toward a trap.

migration

The processing step that moves seismic reflections to their true subsurface positions and collapses diffractions to their apexes.

migration aperture

The lateral distance migration gathers energy from, which must be wide enough for steep dips.

migration method

The algorithm used to reposition reflections.

migration path

The route hydrocarbons followed from source rock to trap.

migration pathway

The route hydrocarbons took from source to trap.

migration velocity

The velocity field used to move reflections to their correct position.

mil shim

A shim measured in thousandths of an inch.

Milankovitch cycles

Cyclical variations in the Earth's orbit and axial tilt that change insolation and, through ice volume, drive climate and sea level.

milestone

A dated point marking completion of a defined block of work.

milk emulsion mud

A water-base mud with oil dispersed as the internal phase, as in milk.

mill

A downhole tool with abrasive cutting surfaces used to grind away metal in the hole.

mill out

To remove metal downhole by milling — a plug, a packer, casing or debris.

mill shoe

A dressed cutting shoe run on the bottom of a washpipe or fishing string to mill the top and outside of a fish.

mill, milled

A mill is a tool that grinds metal downhole. A mill is usually used to remove junk in the hole.

milliamp

One thousandth of an ampere, the unit instrument signals are transmitted in.

milliamp output

The four to twenty milliamp signal an instrument transmits.

milliampere

One thousandth of an ampere.

milliampere (mA)

One thousandth an ampere.

millidarcie

The practical unit of permeability.

millidarcy

One thousandth of a darcy (10⁻³ darcy).

milligrams per kilogram

A mass-basis concentration unit, equal to parts per million by weight, abbreviated mg/kg.

milligrams per liter

A concentration unit expressing mass of solute per liter of solution, abbreviated mg/L.

milliliters

The volume unit used in laboratory fluid measurement.

milling

A process that uses a mill or similar downhole tool to cut and remove material from equipment or tools located in the wellbore.

Million British thermal units (MMBtu)

The energy unit in which gas is usually priced, since gas is bought for its heat content.

million standard cubic feet

A gas volume unit, abbreviated MMscf, measured at defined standard pressure and temperature.

million tonnes per annum (mtpa)

The unit in which LNG plant capacity is quoted.

millisecond

A unit of time equivalent to 0.001 seconds.

mils per year penetration

A corrosion rate in thousandths of an inch of metal loss per year, abbreviated mpy.

mindfulness

Deliberate attention to the present, used to reduce reactivity and stress.

mineral

A naturally occurring inorganic crystalline solid with a definite chemical composition and structure.

mineral interest

Ownership of the minerals beneath a tract, with the right to explore for and produce them or to lease that right to another.

mineral right

The legal right to extract minerals from a property, separable from the surface right.

mineral staining

Mineral staining is the discoloration of a sample's surface by the presence or reaction of minerals and fluids in the subsurface.

mineral, mineralogy, mineralogical

A mineral is a naturally occurring substance that is solid and inorganic representable by a chemical formula, usually abiogenic, and has an ordered atomic structure. It is different from a rock, which can be an aggregate of minerals or non-minerals and does not have a specific chemical composition.

mineralogy

The study of minerals — their composition, structure, formation and properties — and by extension the mineral make-up of a rock.

Minerals Management Service

The former US agency for offshore leasing, royalty collection and platform inspection, reorganized into BOEM and BSEE in 2011.

minicase

A short scenario, usually a page, presenting one dilemma for discussion.

minifrac

A small calibration injection performed before the main fracture treatment, to measure closure pressure, fluid efficiency and formation response.

minimalist design

Removing everything that does not carry information.

minimum boiling point azeotrope

An azeotrope that boils at a temperature that is below the boiling points of its components.

minimum exploration work program

The seismic and drilling a license obliges the holder to complete within a set period.

minimum horizontal

The smaller horizontal stress, perpendicular to which hydraulic fractures open.

minimum horizontal stress

Minimum horizontal stress is one of the principal stresses that confined underground formations are subjected to. Hydraulic fracture propagates perpendicular to the minimum principal stress.

minimum miscibility concentration

The least amount of enriching component that must be added to an injection gas for it to be first-contact miscible with the reservoir oil.

minimum miscibility enrichment

Another term for the minimum miscibility concentration of an injection gas.

minimum miscibility pressure

The lowest pressure at which an injection gas and a reservoir oil become miscible at a given temperature and composition.

minimum restriction

The smallest internal diameter a toolstring must pass to reach its working depth.

minimum-time path

The route a seismic ray actually takes between two points, the one that makes traveltime stationary under Fermat's principle.

minority participant

A partner whose interest is too small to control decisions under the operating agreement.

miocene

The geological epoch whose sediments host many major producing reservoirs.

misalignment

Shafts not on a common axis, which loads bearings and couplings until something fails.

miscibility

The condition under which injected gas and reservoir oil mix without an interface.

miscibility pressure

The pressure above which injected gas and reservoir oil mix without an interface.

miscible

Describing fluids that mix in all proportions to form a single homogeneous phase, with no interface between them.

miscible displacement

A recovery process in which the displacing fluid becomes miscible with the oil, so no interface and therefore no capillary trapping remains.

miscible flooding

Injecting a fluid that mixes with the oil, removing the interfacial tension that traps it.

miscible gas

Injected gas that mixes with reservoir oil without an interface.

misclassification

Treating an employee as a contractor, whether by error or to avoid obligations.

missile

The manifold trailer on a fracturing location that takes blender discharge and distributes it to the pumps and the wellhead line.

mission statement

What the organization exists to do, stated so it can guide choices.

mist

Fine liquid droplets carried suspended in a gas stream.

mist drilling

Air drilling with a small amount of water and foaming agent injected, so modest formation water inflow is carried out as a dispersed mist.

mist eliminator

Pad or vane bank at a vessel's gas outlet, coalescing fine droplets so they drain back.

mist extractor

A device in the separator, usually of woven wire mesh, which re-moves liquid mist from the gas.

mist flow

A multiphase regime in which gas is the continuous phase and the liquid travels entrained within it as fine droplets.

mistie

A failure of interpreted horizons or values to agree where two seismic lines cross.

mixed deposits

Downhole deposits combining organic material such as wax or asphaltene with inorganic scale, silt or clay.

mixed number

A number that consists of a whole number and a fraction.

mixed-metal hydroxide

A layered hydroxide of two or more metals, used as a mud additive that gives extremely high low-shear viscosity, abbreviated MMH.

mixed-metal silicate

A silicate-based viscosifier that builds a strongly shear-thinning structure with bentonite, abbreviated MMS.

mixing box

A device used in double-duct ventilation systems to mix air coming from warm air ducts and cold air ducts.

mixing tank

A vessel with an agitator for blending or dissolving.

MMBBL

One million barrels of crude oil, bitumen, condensate or natural gas liquids.

MMBOE

One million barrels of oil equivalent.

MMBTU

One million British thermal units.

MMC

Minimum miscibility concentration — the least enrichment of an injection gas that achieves miscibility with the reservoir oil at given conditions.

MMCF

One million standard cubic feet of natural gas. In the United States, standard conditions are defined as gas at 14.7 psia and 60oF.

MMH

Mixed metal hydroxide: a clay-mud additive whose hydroxide layers carry two or more metal cations, producing a mud that thins sharply under shear and suspends solids at rest.

MMS

The Minerals Management Service: the former US agency responsible for offshore leasing, royalty collection and platform inspection.

MMSCF

One million standard cubic feet of gas. (One cubic foot of gas at 60°F (15°C) and atmospheric pressure.)

MMSCFD

Measurement of natural gas equaling "one million standard cubic feet perday."

mnemonic

A simple abbreviation for a PLC instruction that is often somewhat descriptive. For example, "TON" for Timer: On-Delay.

mobile marketing

Marketing designed for mobile devices and the contexts in which they are used.

mobile offshore drilling unit

Any self-contained drilling vessel that can be moved between locations — jackup, submersible, semisubmersible or drillship.

mobile platform threat

Risks specific to phones and tablets, which leave the perimeter and mix personal use.

mobility

The ratio of effective permeability to phase viscosity. The overall mobility is the sum of individual phase mobilities. Well productivity is directly proportional to the product of mobility and layer thickness.

mobility buffer

A polymer-thickened water slug pumped behind a chemical flood to protect it from being fingered through by the drive water.

mobility control

Managing the mobility of an injected fluid so that it stays at or below that of the oil it is displacing, keeping the front stable.

mobility ratio

The mobility of an injectant divided by that of the fluid it is displacing. A comparison of the ability of one fluid to move through or displace another fluid.

MODBUS protocol

A standard communications protocol that governs the transmission of data through networks.

model

A representation of a property or system used to make predictions and to test observations against assumptions.

model context protocol (mcp)

An open standard by which a language model connects to external data sources and tools through a defined interface.

model drift

The gradual loss of a deployed model's accuracy as the data it sees departs from the data it was trained on.

Model management

The tracking, versioning, deployment and monitoring of machine learning models across their working life.

model parameter

A value the model is given rather than one it computes.

modeling

The construction of a model — physical, analogue or numerical — to represent a system.

Modern Banking Representative Certification

A credential covering the products, regulation and conduct expected of retail banking staff.

modern office

The reconfigured workplace built around collaboration rather than assigned desks.

Modified Carry Agreement

A funding arrangement where a partner advances the state's share and recovers it from production.

modified isochronal

A gas well test variant used where the reservoir will not stabilize between flows.

modified isochronal test

An isochronal test in which shut-in periods are made equal in length to the flow periods, rather than long enough for full stabilization.

MODU

Mobile offshore drilling unit: any self-contained floating or bottom-supported drilling vessel — jackup, submersible, semisubmersible or drillship.

moduli

The elastic constants relating stress to strain, from which seismic velocity follows.

modulus

A measure of a rock's stiffness, relating applied stress to resulting strain.

modulus of compression

The bulk modulus — the ratio of applied pressure to the fractional volume change it produces.

modulus of elasticity

Any of the constants relating stress to strain in an elastic material, each corresponding to a different mode of deformation.

modulus of rigidity

The shear modulus — the ratio of shear stress to shear strain, describing resistance to change of shape at constant volume.

Moho

The Mohorovicic discontinuity: the boundary between the Earth's crust and mantle, marked by a sharp rise in seismic velocity past 8 km/s.

Mohorovicic discontinuity

The boundary between the Earth's crust and mantle, recognized by a sharp increase in seismic velocity, at depths from about 5 km to 75 km.

moisture

A measure of the amount of water absorbed by a solid material.

moisture content

How much water a material holds.

moisture separator

A vessel removing water droplets from a gas or steam stream.

molded-case circuit

A circuit breaker with its mechanism enclosed in a molded housing.

molded-case circuit breaker

A circuit breaker that is fully enclosed in an insulated housing.

moldic

Porosity formed where a grain or fossil has dissolved, leaving its mold.

moldic porosity

Secondary porosity formed where a grain, shell or crystal has been dissolved away, leaving a void in the shape of what was there.

mole

The fundamental unit of mass for a substance usually expressed in grams. Often shortened to mol.

mole fraction

The proportion of a mixture accounted for by one component, counted in molecules rather than mass.

molecular motion

The movement of molecules, which is what temperature measures.

molecular sieve

A crystalline adsorbent with pores of a fixed size, used where glycol cannot reach the dryness required.

molecular sieve bed

A vertical vessel filled with solid desiccant pellets for dehydrating a natural gas stream.

molecular structure

The arrangement of atoms in a compound, which determines its behavior and value.

molecular weight

The mass of a molecule, which determines a hydrocarbon's phase behavior and value.

molecule

The smallest particle of a substance that retains all of the properties of that substance.

moment

The turning effect of a force about an axis — the force multiplied by its perpendicular distance from that axis.

moment tensor

The mathematical description of a seismic source's mechanism, from which fracture orientation is inferred.

MON

Motor octane number; indicates gasoline performance under severe operating conditions.

monitoring and controlling

Tracking progress against plan and acting on the variance.

monkeyboard

The platform partway up the derrick from which the derrickman handles the top of each stand during a trip.

mono-conductor cable

Mono-conductor cables, with a typical diameter of around 1/4 inch, are mostly used for well completion services, such as firing perforating guns or setting wireline packers and plugs, and for basic production logging surveys, such as flowmeters and temperature logs in hydrocarbon producing wells.

monobore

A completion of uniform internal diameter from surface to the reservoir.

monochromator

The optical element selecting a single wavelength from a spectrum.

monoethanolamine (MEA)

A type of amine that consists of one nitrogen atom, two hydrogen atoms, and an ethanol molecule.

monomer

A small, individual molecule that is used to make a polymer chain.

monomineralic

Monomineralic refers to rocks composed primarily of a single mineral, such as rock salt (halite), limestone (calcite), and quartzite (quartz).

monopole

An acoustic transmitter that expands and contracts uniformly, radiating equally in all directions around the borehole.

monopole sonic tool excitation

In monopole excitation, the sonic logging tool's transmitter emits acoustic energy uniformly around the tool. In fast formations, this energy excites three waves that travel down the borehole wall: Compressional; Shear; Stoneley waves.

monostable multivibrator

A multivibrator that has one stable state.

Monte Carlo risk analysis

Assessing risk by sampling a project's uncertain inputs many times over and building the distribution of outcomes that results.

Monte Carlo sampling

Drawing random values for an uncertain input, either from a fitted theoretical distribution or directly from the histogram of observed data.

Monte Carlo simulation

Running a model repeatedly with randomly sampled inputs, so that the spread of results shows the risk carried by the answer.

montmorillonite

A very soft phyllosilicate group of minerals that typically form in microscopic crystals, forming a clay. A member of the smectite group, it is a 2:1 clay with 2 tetrahedral sheets sandwiching a central octahedral sheet. The particles are plate-shaped with an average diameter around 1 μm.

montmorillonite illite

The clay conversion with burial depth, used as a maturity and overpressure indicator.

monument

A permanent surveyed marker of known position and elevation, set so a location can be reoccupied later.

moon pool

The opening through the hull of a drillship or semisubmersible through which drilling equipment is run.

mooring

The system holding a floating vessel or unit on station.

mooring system

The anchors and lines holding a floating unit on station.

moorings

Lines that are used to secure a barge to a dock during a transfer.

moral argument

Reasoning from premises to a conclusion about what ought to be done.

moral vs. nonmoral standards

Standards concerning right and wrong against standards of taste, law or custom.

morale

The prevailing mood of a team, which shows in effort and turnover before it shows in results.

morning tour

The drilling crew shift that begins in the early morning, conventionally pronounced tower.

mosquito bill

The dip tube inside a gas anchor that draws fluid from below the gas separation point into the rod pump.

motion

A body changing position.

motivation

What causes someone to expend effort, which differs person to person.

motor action

The movement of an object that results from the interaction of two magnetic fields.

motor branch circuit

A circuit that provides power and protection for a particular motor.

motor contactor

The switching device making and breaking the motor supply.

motor control center

A common housing in which several motor controllers and other electrical devices are grouped together. Also called a switch rack.

motor controller

A device or group of devices whose purpose is to control and protect a motor.

motor gasoline

Gasoline for road vehicles, the largest refined product market by volume in some regions.

motor operator

A motor-driven assembly used to position a valve electrically by the use of gearing.

motor shaft

The rotating output shaft of a motor.

motor starter

A large relay designed for controlling power to a motor; also called a contactor.

motor winding

The insulated coils in a motor that carry current and produce its field.

motorman

The crew member responsible for the rig's engines and mechanical plant.

mousehole

A lined hole in the rig floor beside the rotary that holds the next joint ready to be picked up.

mouth bar

Mouth bars are part of a deltaic system, typically referring to the mid-channel deposition of river-transported sediment at the river's mouth.

movable contact

The contact that moves to make or break a circuit.

moveable

Able to be displaced by flow, as distinct from held by capillary force.

moveable hydrocarbons

The volume of hydrocarbon per unit volume of rock that can actually be produced, as opposed to that held immovably.

moved hydrocarbons

The volume of hydrocarbon that invasion has displaced from the flushed zone, indicating that it was mobile.

moveout

The difference in arrival time of the same reflection recorded at two different offsets.

moveout pattern

The way arrival time changes across offsets, from which velocity is derived.

moveout velocity

The velocity derived from how arrival time changes with offset.

moving R chart

A chart for which the value of each plotted point is calculated by subtracting the smallest value from the largest value of a specific number of the most recent samples.

moving X-bar chart

A chart for which the value of each plotted point is calculated by averaging the values of a specific number of the most recent samples.

moving-source method

A survey in which the transmitter is moved with the receivers rather than left fixed, common in electromagnetic work.

MPD

Managed pressure drilling: an adaptive process that controls the annular pressure profile precisely, holding it within close tolerances the length of the well.

MPHI

MPHI is the effective porosity derived from NMR log interpretation.

mpy

Abbreviation for mils per year, the corrosion rate of a coupon in thousandths of an inch of penetration.

MR tanker (Medium Range)

The Medium Range product tanker, the workhorse of regional clean-product trade.

MRIAN

A proprietary, computer-based petrophysical analysis developed by NUMAR that uses MRIL measurements to augment conventional resistivity and porosity logs within a Dual Water petrophysical interpretation model.

mril

The magnetic resonance imaging log, measuring pore fluid rather than rock matrix.

MRS

Magnetic reversal sequence: the succession of switches between normal and reversed polarity of the Earth's magnetic field through geological time.

mscf

Thousand standard cubic feet, a customary unit of gas volume.

MSCFD

Measurement of natural gas equaling "one thousand standard cubic feet perday."

MSD signs

Objective findings that an MSD is present including decreased range of motion, decreased grip strength, loss of muscle function and, in the most severe cases, even deformity.

MSD symptoms

Physical indications that an employee may be developing an MSD. They include numbness, burning, an ache or pain, tingling, cramping and stiffness.

MSDS

Material safety data sheet: the document setting out a chemical's hazards, physical and chemical properties, safe handling and emergency measures.

MSE

Mechanical specific energy — the work the bit expends per unit volume of rock removed.

MSIG

MSIG is the total porosity from NMR log interpretation.

MT

Magnetotelluric — a method mapping subsurface resistivity from naturally occurring electric and magnetic field variations.

MTPA

Millions of tonnes per annum.

mucous membranes

A lubricating membrane lining an internal surface or an organ, such as the mouth, throat, eyes, nasal passages and wind pipe.

mud

The circulating fluid used in drilling, whatever its base — synonymous with drilling fluid.

mud acid

A mixture of hydrofluoric and hydrochloric acid used to dissolve clay and silica in a sandstone matrix treatment.

mud additive

Any material added to a drilling fluid to give or restore a specific property — weight, viscosity, filtration control, lubricity or inhibition.

mud anchor

A large-diameter pipe around the gas anchor that lets solids settle out of the fluid before it enters the pump.

mud balance

A beam balance with a fixed-volume cup, used at the rig to measure the density of mud, cement or another slurry.

mud cake

Mud cake is the residue deposited on a permeable rock when a drilling fluid is forced against the borehole wall under a differential pressure.

mud cake, filter cake

Mud cake, also termed filter cake, is the residue deposited on a permeable rock when a drilling fluid is forced against the borehole wall under a differential pressure.

mud cleaner

A desilter whose underflow is passed over a fine vibrating screen, so weighting material is recovered while drilled fines are discarded.

mud column

The standing column of drilling fluid, whose weight holds the formation pressure back.

mud cup

A graduated cup used at the rig to take mud samples and measure crude volumes for testing.

mud density

The mass per unit volume of a drilling fluid — the property that sets its hydrostatic pressure.

mud engineer

The specialist who tests the drilling fluid at the rig and prescribes the treatments that keep its properties within program.

mud filtrate

The liquid that passes through a filter cake from a slurry held against the filter medium, driven by differential pressure. Both dynamic and static filtration can produce a filtrate.

mud filtrate invasion

The penetration of drilling fluid liquid into the formation, which alters what logs measure.

mud gas

Gas carried up in the drilling fluid, logged continuously as a first indication of hydrocarbons.

mud hopper

A funnel and jet arrangement through which dry materials are drawn into the circulating mud system.

mud house

The store at the rig where sacked mud additives are kept, adjacent to the mixing hopper.

mud in

The mud being pumped into the well, as distinct from what returns.

mud log

A detailed record (a well log) of a borehole generated by examining the cuttings of rock, associated gases, and hydrocarbon fluorescence brought to the surface by the circulating drilling mud. It typically denotes rock formation properties, associated gases, and hydrocarbon fluorescence for cuttings at specified intervals.

mud logger

A mud logger is an oil and gas professional who collects samples of drill cuttings as a well is being drilled. These cuttings are usually taken from shale shakers. Mud loggers analyze these samples to identify the rock types and their properties, determine the presence of hydrocarbons, and correlate them to depths in the well.

mud logging

The process whereby circulating drilling mud and its associated drill cuttings and gas are continuously monitored as the well is being drilled, and findings are documented in a mud log.

mud logging unit

A trailer or cabin at the wellsite (or a designated safe location near the shale shakers) that contains the special equipment and materials needed to collect, process, and evaluate drill cutting samples and analyze any gas contained in the returning drilling mud.

mud motor

A downhole motor driven by the circulating mud, turning the bit without rotating the drillstring.

mud out

The mud returning from the well through the flowline.

mud oven

A temperature-controlled oven in which mud samples in test cells are aged at downhole temperature before testing.

mud pit

A surface tank holding drilling fluid at the rig or a mixing plant.

mud program

The plan setting out the fluid system, properties and treatments for each interval of a specific well.

mud property

A measured characteristic of drilling fluid such as density, viscosity or filtrate loss.

mud pulse

Pressure pulses in the mud column used to telemeter measurements to surface while drilling.

mud pulse telemetry

A method of transmitting LWD and MWD data acquired downhole to the surface using pressure pulses in the mud system. The measurements are usually converted into an amplitude- or frequency-modulated pattern of mud pulses. The same telemetry system is used to transmit commands from the surface.

mud pump

The high-pressure pump circulating drilling fluid down the string and up the annulus.

mud report

The daily record the mud engineer files, giving measured fluid properties, materials used and treatments made.

mud retort

A small distillation unit that heats a measured mud sample to drive off and condense its water and oil, so the solids content can be calculated by difference.

mud return line

The large-diameter line carrying returns from the bell nipple to the shakers and mud tanks.

mud scale

The beam balance used at the rig to measure mud density, another term for the mud balance.

mud still

A retort that heats a measured mud sample to drive off its water and oil and condense them, giving the oil, water and solids fractions by volume.

mud system

The circulating drilling fluid with its mixing, treating and solids-removal equipment.

mud tracer

A distinctive, inert material put into the mud at a known time so that its return at surface gives the lag.

mud up

To convert water or a thin water-clay slurry into a proper mud by adding commercial materials.

mud weight

The density of a drilling fluid, and so the hydrostatic pressure it exerts per unit of depth.

mud-aging cell

A sealed pressure vessel in which a mud sample is heated to downhole temperature before its properties are measured.

mud-boats

Mud-boats supply drilling mud to offshore drilling rigs.

mud-in sample

Mud taken from the suction pit, representing what is about to be pumped down the well.

mud-out sample

Mud taken from the flowline or possum belly after it has returned from the well and passed the shakers.

mud-pulse telemetry

Mud-pulse telemetry refers to pressure waves traveling through drilling mud.

mud-supported or grain-supported

In this context, “supported” refers to the fabric matrix of the rock. Therefore, the grains are either encompassed by mud or by smaller grains.

mudding off

Damaging a productive interval by coating the grains and plugging permeability with mud solids and filtrate.

mudding up

Adding commercial products to water or a water-clay slurry to make it a drilling mud.

mudline

The sea floor, the datum offshore depths and casing programs are referenced to.

mudrock

A fine-grained detrital rock formed by the consolidation of clay- and silt-sized particles — shale, mudstone and siltstone together.

mudstone

A type of mud rock; a fine-grained sedimentary rock whose original constituents were clays or muds. Grain size is up to 0.0625 mm (0.0025 in), with individual grains too small to be distinguished without a microscope.

multi-agent system (mas)

An arrangement in which several model-driven agents coordinate on parts of a larger task, abbreviated MAS.

multi-conductor wireline logging cable, multi-conductor cable

Seven (7)-conductor wireline is the standard for open hole logging. It is better than a single conductor cable for supplying power to the tools and for electrical communications.

multi-lateral well

A multilateral well is a well that has more than one branch radiating from the main wellbore.

multi-mineral

Multi-mineral is a situation where there is more than one mineral present.

multi-mineral analysis

Multi-mineral analysis methods emphasise the mineral content of the formation rocks. Such log analysis techniques are often based on a probabilistic, or optimizing, approach to modeling wireline and rock data.

multi-mode fiber

Common 62.5/125 fiber that can use inexpensive, low power, LEDs as transmitting light sources but has a range of about two kilometers due to pulse distortion.

multi-pass heat exchanger

A heat exchanger in which one or both fluids pass through more than once.

multi-shot reclosing

A reclosing relay that recloses a circuit breaker several times; the first reclose is usually instantaneous, and can be followed by up to two or three delayed recloses.

multi-stage compressor

A compressor which has two or more cylinders to compress gas in stages from low pressure to high pressure.

multi-touch campaign

A campaign reaching the same prospect through several coordinated contacts.

multiazimuth towed-streamer acquisition

Repeating a conventional narrow-azimuth marine survey over the same area along several different sail directions.

multicapacitance flowmeter

A flowmeter that times a disturbance passing between two dielectric sensors a known distance apart.

multicomponent

Recording more than one direction of ground motion, so shear waves can be used.

multicomponent seismic data

Seismic data recorded with sensors measuring motion in more than one direction, so shear as well as compressional waves are captured.

multiconductor cable

A cable that consists of a group of conductors that are insulated from one another.

multicore solder

Solder that has flux embedded in it.

multidraw tower

A distillation tower that separates a feed into more than two products; also called a side-draw tower.

multifinger caliper

A tool with many independently sprung fingers that measures the internal profile of tubing or casing, finding pits, wear and deformation.

multigenerational workforce

A workforce spanning several age cohorts with different expectations of work.

multilateral

A well with more than one branch drilled off the main wellbore.

multimeter

A handheld instrument measuring voltage, current and resistance.

multimodal models

Models that take in and relate more than one kind of data — text, images, audio, video — in a single system.

multipart valve

A valve that can route fluid flow through a number of different openings, or ports.

multiparty negotiation

Negotiation among three or more parties, where coalitions form and change the arithmetic.

multipass method

Interpreting a spinner flowmeter from several passes over the zone at different logging speeds, run both up and down.

multiphase

Involving more than one distinct fluid phase — oil, water and gas together.

multiphase flow

The simultaneous flow of more than one fluid phase, in a pipe or through a porous medium.

multiphase fluid

A fluid stream comprising more than one phase — liquids, gas and sometimes solids together.

multiphase fluid flow

The commingled movement of different fluid phases through the same conduit or pore system.

multiphase holdup log

A log of gas, oil and water holdup versus depth derived from pulsed-neutron spectroscopy measurements.

multiphase meter

An inline meter that reports oil, gas and water rates from a flowing stream without separating it first.

multiphase pump

A pump that handles the full produced stream — oil, gas, water and some solids — without separating it first.

multiple completion

A single wellbore completed so that two or more zones can be produced separately.

multiple loop control

A type of process control in which more than one process loop is controlled by a single controller. Each loop includes its own inputs, setpoints, control algorithms, and outputs.

multiple reflection

Seismic energy that has been reflected more than once on its path, arriving later than the primary from the same interface.

multiple regression

A statistical method fitting a response to two or more predictor variables at once.

multiple salinity

A laboratory method that measures a shaly core's resistivity while saturated with brines of several different salinities, to separate clay conductivity from that of the pore water.

multiple service contract

A contract in which the host country specifies the services, and their cost, that the operator must use in developing a concession.

multiple-contact miscibility

Miscibility achieved not on first contact but after repeated exchange of components between injected gas and reservoir oil as the front advances.

multiple-isotope log

A log of the individual radioactive isotopes present near the borehole, resolved by their gamma ray energies.

multiple-isotope spectroscopy

The energy-resolved gamma ray measurement from which a multiple-isotope log is produced.

multiple-rate tests

A well test conducted at a series of different flow rates, used where a constant rate cannot be held long enough for a drawdown test.

multiplication component

A control device in which the output is the product of two inputs.

multiplication factor

A factor a reading is multiplied by to give the true value.

multipoint

Using several measurement points, as in a multipoint deliverability test.

multiport valve

A valve that can route fluid flow through a number of different openings, or ports.

multishot survey

A wellbore deviation survey in which a single instrument records inclination and azimuth at many depths on one run.

multistage

Performed in several separate stages, as a fracture treatment along a horizontal well.

multistage centrifugal pump

A centrifugal pump with impellers in series, developing high head at moderate flow.

multivariate testing

Testing several elements at once to find the best combination.

multivibrator

An RC oscillator that has two amplifier stages and produces non-sinusoidal signals. The frequency of the signals is determined by resistance and capacitance rather than by inductance and capacitance.

multiwell pad

A single surface location from which several wells are drilled, their laterals fanning out into the reservoir below.

murban

Abu Dhabi's light sour crude, traded on its own exchange and used as a regional benchmark.

musculoskeletal disorder (MSD)

Disorders of the muscles, nerves, tendons, ligaments, joints, cartilage, blood vessels and spinal discs. They may include muscle strains and tears, ligament sprains, joint and tendon inflammation, pinched nerves and spinal disc degeneration. Although MSDs can result from one-time incidents, more often than not they result from damage to the body that has accumulated over a period of time. These types of MSDs are also sometimes referred to as cumulative trauma disorders.

mushrooming

A damage condition in which the striking surface of a tool, such as a chisel, is misshaped, creating a mushroom pattern.

muskat

Author of the foundational texts on the physics of flow through porous media.

mute

To zero part of a seismic trace before stacking, removing energy that would otherwise degrade the stack.

mutual solvent

An additive soluble in oil, water and acid alike, used to leave the formation uniformly water-wet after a treatment.

MWD

Measurement while drilling: measuring wellbore trajectory, and usually pressure and temperature, downhole while the hole is being drilled.

mwd tool

The instrument measuring and transmitting directional data while drilling.

My

Million years — a duration rather than an age, though the usage is inconsistent.

MYBP

Millions of years before present: a geological dating unit, now more usually written Ma.

Myers-Briggs Type Indicator

A personality instrument sorting preferences into sixteen types, widely used and widely disputed.

mysid shrimp

Mysidopsis bahia, the small shrimp used as the test organism in the US EPA's marine toxicity bioassay.