done 2

The conventional value for the nautical mile was established at the First International Extraordinary Hydrographic Conference held in the Principality of Monaco in?

1929

A worldwide professional organization committed to corrosion prevention and control, founded in ____, is headquartered in Houston, Texas, USA and areas of focus include oil and gas, water, transportation and infrastructure protection.

1943

active margin

A boundary of colliding lithospheric plates. The present subduction zones of the Pacific Rim, the older mountains of the Alps, and the Himalayas represent ______.

gas-water contact

A bounding surface in a reservoir above which predominantly gas occurs and below which predominantly water occurs. Gas and water are somewhat miscible, so the contact between gas and water is not necessarily sharp and there is typically a transition zone between 100% gas and 100% water in reservoirs.

Bouma sequence

A characteristic sequence of sedimentary structures occurring in sedimentary rocks deposited in areas of deep water sedimentation by turbidity currents, which form deposits called turbidites. In theory, a complete _____ comprises sediments that fine upwards, consisting of a lowermost layer of coarse, chaotic clastic sediments deposited under conditions of high depositional energy overlain by successively finer grained and better stratified sediments like sands and muds deposited under calmer conditions that are labeled as Units A though E. In practice, however, the chaotic, high-energy nature of turbidite deposition can alter or remove underlying sediments so that incomplete sequences of sediments typically remain preserved.

geologic time scale

A chronological chart of the stages and ages of events in the history of the Earth, from its initial formation to present, that has been constructed on the basis of the rock record. As is the typical natural position of rocks, the oldest event is at the bottom of the chart and the youngest is at the top. Both absolute and relative ages of rocks and fossils supplement interpretations from rocks. The vastness of geologic time and the slowness of geological processes are difficult to capture in a simple chart.

carbonate

A class of sedimentary rock whose chief mineral constituents (95% or more) are calcite and aragonite (both CaCo3) and dolomite [CaMg(CO3)2], a mineral that can replace calcite during the process of dolomitization.

bentonite

A clay mineral that is composed principally of three-layer clays, such as montmorillonite, and widely used as a mud additive for viscosity and filtration control. Commercial bentonite ores vary widely in amount and quality of the swelling clay, sodium montmorillonite. Ores of lower quality, those with more calcium-type montmorillonite, are treated during grinding by adding one or more of the following: sodium carbonate, long-chain synthetic polymers, carboxymethylcellulose (CMC), starch, or polyphosphates. These help make the final product meet quality specifications. Unfortunately, the additives may not remain effective in "the real mud world" when in use at the rig due to hardness ions in the water, high temperature, bacterial attack, mechanical shear-degradation, and other factors that can render these additives ineffective.

granite

A coarse-grained, plutonic or intrusive igneous rock of felsic composition having large crystals of quartz, feldspar and mica. In the oil field, "______" is sometimes used incorrectly to indicate any type of hard rock.

caliche

A crust of coarse sediments or weathered soil rich in calcium carbonate. It forms when lime-rich groundwater rises to the surface by capillary action and evaporates into a crumbly powder, forming a tough, indurated sheet called calcrete.

barite

A dense mineral comprising barium sulfate [BaSO4]. Commonly used as a weighting agent for all types of drilling fluids, barites are mined in many areas worldwide and shipped as ore to grinding plants in strategic locations, where API specifies grinding to a particle size of 3 to74 microns. Pure barium sulfate has a specific gravity of 4.50 g/cm3, but drilling-grade barite is expected to have a specific gravity of at least 4.20 g/cm3 to meet API specifications. Contaminants in barite, such as cement, siderite, pyrrhotite, gypsum, and anhydrite, can cause problems in certain mud systems and should be evaluated in any quality assurance program for drilling mud additives.

basin

A depression in the crust of the Earth, caused by plate tectonic activity and subsidence, in which sediments accumulate. (Sedimentary basins vary from bowl-shaped to elongated troughs. Basins can be bounded by faults. Rift basins are commonly symmetrical; basins along continental margins tend to be asymmetrical. If rich hydrocarbon source rocks occur in combination with appropriate depth and duration of burial, then a petroleum system can develop within the basin. Most basins contain some amount of shale, thus providing opportunities for shale gas exploration and production.)

glauconite

A green silicate mineral found in sedimentary rocks and formed on continental shelves characterized by slow sedimentation and organic matter, such as fecal pellets, present in an oxidizing environment. In sufficient quantity, it can form a sandy, green deposit such as the Cretaceous greensands of the US and UK.

clay

A large family of complex minerals containing the elements magnesium, aluminum, silicon and oxygen (magnesium, aluminum silicates) combined in a sheet-like structure. These are mined from surface pits as relatively pure deposits and used for bricks, pottery, foundry molds and in drilling fluids among other uses. (Clays, as claystones, shales and intermixed with sands and sandstones make up the largest percentage of minerals drilled while exploring for oil and gas. Individual clay platelets can be viewed only with an electron microscope. . The atomic structure of the clay group of layered silicate minerals varies from two-layer to three-layer or four-layer (mixed-layer) structures. One of the structural layers is a plane of silicon dioxide tetrahedra (silicon at the center and oxygen at all four corners of the tetrahedron). The other structural layer is a plane of aluminum hydroxide octahedra (aluminum at the center and hydroxides at all six corners). The tetrahedral and octahedral layers fit one on top of the other, with oxygen atoms being shared as oxide and hydroxide groups.)

bed

A layer of sediment or sedimentary rock, or stratum.

bed

A layer of sediment or sedimentary rock, or stratum. A ____ is the smallest stratigraphic unit, generally a centimeter or more in thickness. To be labeled a ____, the stratum must be distinguishable from adjacent beds.

base map

A map on which primary data and interpretations can be plotted. A ______ typically includes locations of lease or concession boundaries, wells, seismic survey points, and other cultural data such as buildings and roads, with a geographic reference such as latitude and longitude or Universal Transverse Mercator (UTM) grid information. Geologists use topographic maps as base maps for construction of surface geologic maps. Geophysicists typically use shot point maps, which show the orientations of seismic lines and the specific points at which seismic data were acquired, to display interpretations of seismic data. In the field, geologists can use a plane table and alidade to construct a base map.

geologic map

A map showing the type and spatial distribution of rocks at the surface of the Earth. Rock formations are color-coded and symbols for geological structures are annotated, so age relationships are evident. Topographic contours and cultural features can also appear on ______.

antithetic fault

A minor, secondary fault, usually one of a set, whose sense of displacement is opposite to its associated major and synthetic faults. Antithetic-synthetic fault sets are typical in areas of normal faulting.

weathered layer

A near-surface, possibly unconsolidated layer of low seismic velocity. The base of the _____ commonly coincides with the water table and a sharp increase in seismic velocity. The ______ typically has air-filled pores.

gas sand

A porous sand layer or sand body charged with natural gas.

GPTS

A record of the onset and duration of the multitude of episodes of reversal of the Earth's magnetic polarity, or geomagnetic polarity reversals. (The ____ was developed by thorough study of rocks from around the world, during which it was observed that rocks from specific time periods contained magnetic minerals whose orientation was opposite to that of the current magnetic field. By comparing the patterns of magnetic reversals with those of rocks of known age, the approximate ages of rocks can be established. This is particularly useful for basalts of the oceanic crust, which record the Earth's magnetic field as they solidify from molten lava symmetrically about the midocean ridges. The time scale has been accurately extended back to the Upper Jurassic, the age of oldest existing oceanic crust.)

geomagnetic polarity time scale

A record of the onset and duration of the multitude of episodes of reversal of the Earth's magnetic polarity, or geomagnetic polarity reversals. The GPTS was developed by thorough study of rocks from around the world, during which it was observed that rocks from specific time periods contained magnetic minerals whose orientation was opposite to that of the current magnetic field. By comparing the patterns of magnetic reversals with those of rocks of known age, the approximate ages of rocks can be established. This is particularly useful for basalts of the oceanic crust, which record the Earth's magnetic field as they solidify from molten lava symmetrically about the midocean ridges. The time scale has been accurately extended back to the Upper Jurassic, the age of oldest existing oceanic crust.

caprock

A relatively impermeable rock, commonly shale, anhydrite, or salt, that forms a barrier or seal above and around reservoir rock so that fluids cannot migrate beyond the reservoir.

graben

A relatively low-standing fault block bounded by opposing normal faults. ______ (used as both singular and plural) can form in areas of rifting or extension, where normal faults are the most common type of fault. Between graben are relatively high-standing blocks called horsts. A half-graben is a downdropped block bounded by a normal fault on only one side.

allochthon

A rock mass formed somewhere other than its present location, which was transported by fault movements, large-scale gravity sliding, or similar processes.

geologist

A scientist trained in the study of the Earth. In the petroleum industry, _____ perform a wide variety of functions, but typically generate prospects and interpret data such as maps, well logs, outcrops, cuttings, core samples and seismic data.

zone

A slab of reservoir rock bounded above and below by impermeable rock.

asphalt

A solid or nearly solid form of bitumen that can melt upon heating and contains impurities such as nitrogen, oxygen, and sulfur. ____ forms naturally when the light components or volatiles of petroleum have been removed or evaporated.

angular unconformity

A surface that separates younger strata from eroded, dipping, older strata and represents a gap in the geologic record.

GPS

A system of numerous Earth-orbiting satellites that can be used to determine the location (latitude, longitude and elevation) of a receiver or station on the Earth within about 2 m [6 ft]. Fixed receivers on Earth can be used to determine the relative motions of fault blocks and lithospheric plates. Hand-held receivers can be used for producing accurate geologic maps, acquiring navigation data for 3D seismic surveys, and positioning wells in the field.

Global Positioning System

A system of numerous Earth-orbiting satellites that can be used to determine the location (latitude, longitude and elevation) of a receiver or station on the Earth within about 2 m [6 ft]. Fixed receivers on Earth can be used to determine the relative motions of fault blocks and lithospheric plates. Hand-held receivers can be used for producing accurate geologic maps, acquiring navigation data for 3D seismic surveys, and positioning wells in the field.

alidade

A telescopic surveying device used to construct surface topographic and geologic maps in the field. The ____ is mounted on a plane table, which has a sheet of paper on which to draw the map, and an object or location is sighted through the alidade. The edge of the _____ is aligned in the azimuthal direction of the object or location. The vertical angle from which elevation of the location can be calculated is measured using the calibrated arc of the alidade.

hard rock

A term applied to igneous and metamorphic rocks that are distinguished from sedimentary rocks because they are typically more difficult to disaggregate. Well cemented sedimentary rocks are sometimes described as being hard, but are usually called soft rock. The term can be used to differentiate between rocks of interest to the petroleum industry (soft rocks) and rocks of interest to the mining industry (hard rocks).

cataclasite

A type of metamorphic rock with shearing and granulation of minerals caused by high mechanical stress during faulting or dynamic metamorphism, typically during episodes of plate tectonic activity.

growth fault

A type of normal fault that develops and continues to move during sedimentation and typically has thicker strata on the downthrown, hanging wall side of the fault than in the footwall. ____ are common in the Gulf of Mexico and in other areas where the crust is subsiding rapidly or being pulled apart.

wrench fault

A type of strike-slip fault in which the fault surface is vertical, and the fault blocks move sideways past each other. Given the geological complexity of some deformed rocks, including rocks that have experienced more than one episode of deformation, it can be difficult to distinguish a wrench fault from a strike-slip fault. Also, areas can be deformed more than once or experience ongoing structuring such that fault surfaces can be rotated from their original orientations.

anticlinal trap

A type of structural hydrocarbon trap whose closure is controlled by the presence of an anticline.

clear brine

A water-based solution of inorganic salts used as a well-control fluid during the completion and workover phases of well operations. _____ are solids free, containing no particles that might plug or damage a producing formation. In addition, the salts in brine can inhibit undesirable formation reactions such as clay swelling. ______ are typically formulated and prepared for specific conditions, with a range of salts available to achieve densities ranging from 8.4 to over 20 lbm/gal (ppg) [1.0 to 2.4 g/cmo]. Common salts used in the preparation of simple brine systems include sodium chloride, calcium chloride and potassium chloride. More complex brine systems may contain zinc, bromide or iodine salts. These _____are generally corrosive and costly.

Benioff zone

A zone of the upper mantle in which earthquakes occur when a lithospheric plate is subducted, named in honor of seismologists Kiyoo Wadati and Hugo Benioff.

Wadati-Benioff zone

A zone of the upper mantle in which earthquakes occur when a lithospheric plate is subducted, named in honor of seismologists Kiyoo Wadati and Hugo Benioff. The dip of the Wadati-Benioff zone coincides with the dip of the subducting plate. The Wadati-Benioff zone extends to a depth of about 700 km [435 miles] from the Earth's surface.

Among its long-term endeavors is the development of standardized testing procedures for drilling equipment, drilling fluids and cements, called ____.

API Recommended Practices ("RPs")

The API licenses the use of its monogram (logo), monitors supplier quality assurance methods and sets minimum standards for materials used in drilling and completion operations, called API ________.

API Specifications ("Specs")

CBM

Abbreviation for coalbed methane.

A trade association founded in 1919 with offices in Washington, DC, USA and is sponsored by the oil and gas industry and is recognized worldwide.

American Petroleum Institute (API)

anticline

An arch-shaped fold in rock in which rock layers are upwardly convex. The oldest rock layers form the core of the fold, and outward from the core progressively younger rocks occur. Anticlines form many excellent hydrocarbon traps, particularly in folds with reservoir-quality rocks in their core and impermeable seals in the outer layers of the fold. A syncline is the opposite type of fold, having downwardly convex layers with young rocks in the core.

hydrocarbon kitchen

An area of the subsurface where source rock has reached appropriate conditions of pressure and temperature to generate hydrocarbons; also known as source kitchen, oil kitchen or gas kitchen.

anomaly

An entity or property that differs from what is typical or expected, or which differs from that predicted by a theoretical model. May be the measurement of the difference between an observed or measured value and the expected values of a physical property.

horizon

An interface that might be represented by a seismic reflection, such as the contact between two bodies of rock having different seismic velocity, density, porosity, fluid content or all of those.

accumulation

An occurrence of trapped hydrocarbons, an oil field.

gas hydrate

An unusual occurrence of hydrocarbon in which molecules of natural gas, typically methane, are trapped in ice molecules.

Wentworth scale

Another name for the Udden-Wentworth scale, a grade scale for classifying the diameters of sediments. Particles larger than 64 mm in diameter are classified as cobbles. Smaller particles are pebbles, granules, sand and silt. Those smaller than 0.0039 mm are clay. Several other grain size scales are in use, but the Udden-Wentworth scale (commonly called the Wentworth scale) is the one that is most frequently used in geology.

aquifer

Any water-bearing formation encountered while drilling. Drillers often are concerned about aquifers and are required to take special precautions in the design and execution of the well plan to protect fresh water aquifers from contamination by wellbore fluids. Water in aquifers can flow into the wellbore, contaminate drilling fluids and cause well control problems.

Given the apparent dip and the strike, or two apparent dips, the true dip can be computed.

Apparent Dip

the angle measured in any direction other than perpendicular to the strike of the plane.

Apparent Dip

Grain

As used in log and core analysis, this term refers to all the solid material in the rock, since, when interpreting the measurements, no effort is made to distinguish grains from other solid material.

The value of the separation between two adjacent contours.

CI

A display of seismic traces that share a source.

CSG (common source gather)

X-ray diffraction (XRD).

Crystal structures are also determined by ____.

argillaceous

Describing rocks or sediments containing particles that are silt- or clay-sized, less than 0.625 mm in size. Most have a high clay-mineral content, and many contain a sufficient percentage of organic material to be considered a source rock for hydrocarbon.

arenaceous

Describing sandy-textured rock or sediment. ______ does not necessarily imply silica-rich, but rather particles of sand size, 0.625 to 2 mm, according to the Udden-Wentworth scale.

_____ are so abundant that they can form thick layers of sediment composed of the frustules of the organisms that died and sank to the bottom.

Diatom

the sedimentary rock that forms from diatom frustules.

Diatomite

anomalous

Different from what is typical or expected, or different from what is predicted by a theoretical model. The difference or anomaly may refer to the measurement of the difference between an observed or measured value and the expected values of a physical property. Anomalies can be of great interest in hydrocarbon and mineral exploration because they often indicate hydrocarbon and mineral prospects and accumulations, such as geologic structures like folds and faults. Geochemical anomalies at the surface of the Earth can also indicate an accumulation of hydrocarbons at depth. Geophysical anomalies, such as amplitude anomalies in seismic data and magnetic anomalies in the Earth's crust, can also be associated with hydrocarbon accumulations.

The conventional value for the nautical mile was established at the?

First International Extraordinary Hydrographic Conference

simply water found in the pore spaces of a rock, and might not have been present when the rock was formed.

Formation water, or interstitial water

The volume of gas in a reservoir before production.

Gas initially in place (GIIP)

gas in solution

Gas that is dissolved in a liquid, such as water or oil.

the presence of organic matter rich enough to yield hydrocarbons, adequate temperature, and sufficient time to bring the source rock to maturity.

Generation depends on three main factors. Name two of it.

Certain evaporite minerals, particularly ____, can form excellent cap rocks or seals for hydrocarbon traps because they have minimal porosity and they tend to deform plastically (as opposed to brittle fracturing that would facilitate leakage).

Halite

anisotropic

Having directionally dependent properties. For a crystal of a mineral, variation in physical properties observed in different directions is anisotropy. In rocks, variation in seismic velocity measured parallel or perpendicular to bedding surfaces is a form of anisotropy.

It is a compounds in which gas molecules are trapped within a crystal structure.

Hydrates

axial surface

In folded rocks, the imaginary surface bisecting the limbs of the fold. The _____ is called the axial plane when the fold is symmetrical and the lines defined by the points of maximum curvature of each folded layer, or hinge lines, are coplanar.

grain density

In logs, ______ is calculated from the density log, using an estimate of porosity and knowledge of the fluid content.

density log

In logs, grain density is calculated from the ____ , using an estimate of porosity and knowledge of the fluid content.

porosity and knowledge of the fluid content.

In logs, grain density is calculated from the density, using an estimate of ____.

aulacogen

In plate tectonics, a failed rift arm. At the junctions of tectonic plates, three intersecting lithospheric plates typically are separated by "arms." Arms might be areas of rifting, convergence, or transform faults (similar to a strike-slip fault). The arm along which the motion that spreads the plates apart ceases is termed the failed arm, or aulacogen. Spreading or rifting along the other arms of the triple junction can form new oceanic basins, whereas the ____ can become a sediment-filled graben.

It is rare in such formations and is ignored, being included in the effective porosity.

Isolated Porosity

Gas Water Contact (GWC)

It is a bounding surface in a reservoir above which predominantly gas occurs and below which predominantly water occurs. Gas and water are somewhat miscible, so the contact between gas and water is not necessarily sharp and there is typically a transition zone between 100% gas and 100% water in reservoirs.

Sulfide stress cracking in corrosive environments.

MR0103

Corrosion resistant materials for oil and gas applications

MR0175

alluvium

Material deposited in an alluvial environment, typically detrital sediments that are poorly sorted.

autochthonous

Materials, especially rock masses, that formed in their present location and have not been transported. Fault surfaces can separate indigenous rocks from allochthonous rocks, although some allochthonous rocks are clearly delineated by their differing composition.

A worldwide professional organization committed to corrosion prevention and control, founded in 1943, is headquartered in Houston, Texas, USA and areas of focus include oil and gas, water, transportation and infrastructure protection.

NACE, or NACE International (National Association of Corrosion Engineers)

wet gas

Natural gas containing significant heavy hydrocarbons. Propane, butane and other liquid hydrocarbons can be liquefied.

benthos

Organisms that live at the bottom of a body of water.

hiatal

Pertaining to a hiatus, a cessation in deposition of sediments during which no strata form or an erosional surface forms on the underlying strata; a gap in the rock record. This period might be marked by development of a lithified sediment (hardground) or burrowed surface characteristic of periods when sea level was relatively low. A disconformity can result from a hiatus.

cataclastic

Pertaining to a type of metamorphic rock with shearing and granulation of minerals caused by high mechanical stress during faulting or dynamic metamorphism, typically during episodes of plate tectonic activity.

zonal

Pertaining to a zone, an interval or unit of rock differentiated from surrounding rocks on the basis of its fossil content or other features, such as faults or fractures. For example, a fracture zone contains numerous fractures. A biostratigraphic zone contains a particular fossil or fossils.

anticlinal

Pertaining to an anticline, an arch-shaped fold in rock in which rock layers are upwardly convex. The oldest rock layers form the core of the fold, and outward from the core progressively younger rocks occur. Anticlines form many excellent hydrocarbon traps, particularly in folds with reservoir-quality rocks in their core and impermeable seals in the outer layers of the fold. A syncline is the opposite type of fold, having downwardly convex layers with young rocks in the core.

biostratigraphic

Pertaining to biostratigraphy, the application of plant and animal fossils to date and correlate strata in order to elucidate Earth history, combining the principles of paleontology and stratigraphy. In the petroleum industry, biostratigraphy often denotes the use of terrestrial (pollen and spores) and marine (diatoms, foraminifera, nanofossils) microfossils to determine the absolute or relative age and depositional environment of a particular formation, source rock, or reservoir of interest.

geologic

Pertaining to geology, the study of the Earth-its history, structure, composition, life forms and the processes that continue to change it.

geological

Pertaining to geology, the study of the Earth-its history, structure, composition, life forms and the processes that continue to change it.

allochthonous

Pertaining to materials, particularly rock masses, that formed somewhere other than their present location, and were transported by fault movements, large-scale gravity sliding, or similar processes. _____ material, in contrast, formed in its present location. Landslides can result in large masses of allochthonous rock, which typically can be distinguished from autochthonous rocks on the basis of their difference in composition. Faults and folds can also separate allochthons from autochthons.

authigenic

Pertaining to minerals or materials that grow in place with a rock, rather than having been transported and deposited. These include quartz, chlorite, and other pore-filling minerals or cements that grow during diagenesis. Evaporite minerals are authigenic, or formed in situ.

allogenic

Pertaining to minerals or rock fragments that formed in one location but were transported to another location and deposited. Clastic sediments in a rock such as sandsHTMLtone are allogenic, or formed elsewhere.

anaerobic

Pertaining to systems, reactions, or life processes of species, such as bacteria, in which atmospheric oxygen is not present or not required for survival.

azimuthal

Pertaining to the angle between the vertical projection of a line of interest onto a horizontal surface and true north or magnetic north measured in a horizontal plane, typically measured clockwise from north.

abyssal

Pertaining to the depositional environment of the deepest area of the ocean basins, the abyss. The depositional energy is low, the abyssal plain is flat and nearly horizontal, and fine-grained sediments are deposited slowly by waning turbidity currents or from suspension in the water. The water is thousands of meters deep, so the water is cold and sunlight is minimal.

benthic

Pertaining to the environment and conditions of organisms living at the water bottom, or benthos. Also called benthonic.

bathyal

Pertaining to the environment of deposition and the organisms of the ocean between depths of 200 m [656 ft], the edge of the continental shelf, and 2,000 m [6,560 ft]. The ______ environment is intermediate between the neritic environment and the abyss.

glacial

Pertaining to the environment of deposition by glaciers.

aeolian

Pertaining to the environment of deposition of sediments by wind, such as the sand dunes in a desert. Because fine-grained sediments such as clays are removed easily from wind-blown deposits, eolian sandstones are typically clean and well-sorted.

alluvial

Pertaining to the subaerial (as opposed to submarine) environment, action and products of a stream or river on its floodplain, usually consisting of detrital clastic sediments, and distinct from subaqueous deposition such as in lakes or oceans and lower energy fluvial deposition. Sediments deposited in an alluvial environment can be subject to high depositional energy, such as fast-moving flood waters, and may be poorly sorted or chaotic.

aeolotropy

Predictable variation of a property of a material with the direction in which it is measured, which can occur at all scales. For a crystal of a mineral, variation in physical properties observed in different directions is aeolotropy (also known as anisotropy). In rocks, variation in seismic velocity measured parallel or perpendicular to bedding surfaces is a form of aeolotropy. Often found where platy minerals such as micas and clays align parallel to depositional bedding as sediments are compacted, _____ is common in shales.

anisotropy

Predictable variation of a property of a material with the direction in which it is measured, which can occur at all scales. For a crystal of a mineral, variation in physical properties observed in different directions is anisotropy. In rocks, variation in seismic velocity measured parallel or perpendicular to bedding surfaces is a form of anisotropy. Often found where platy minerals such as micas and clays align parallel to depositional bedding as sediments are compacted, anisotropy is common in shales.

The conventional value for the nautical mile was established at the First International Extraordinary Hydrographic Conference held in?

Principality of Monaco

aggradational

Related to the accumulation of stratigraphic sequences by deposition that stacks beds atop each other, building upwards during periods of balance between sediment supply and accommodation.

abnormal pressure

Reservoir pore fluid pressure that is not similar to normal saltwater gradient pressure. The term is usually associated with higher than normal pressure, increased complexity for the well designer, and an increased risk of well control problems. Pressure gradients in excess of around 10-lbm/galUS equivalent fluid density [0.52 psi/foot of depth] are considered abnormal. Gradients below normal are commonly called subnormal.

Abbreviation for standard temperature and pressure. Organizations establish a standard temperature and pressure to enable the comparison of datasets and to meet their members' and stakeholders' laboratory, industrial and regulatory requirements. For example, the International Union of Pure and Applied Chemistry (IUPAC) defines standard temperature to be 0°C [273.15°K, 32°F] and standard pressure to be 100 kPa [1 bar, 0.9869 atm, 14.504 psi] and the Society of Petroleum Engineers (SPE) defines standard temperature to be 15°C [288.15°K, 59°F] and standard pressure to be 100 kPa.

STP

anhydrite

See: calcium contamination, calcium mud, gyp mud, water-base drilling fluid

accommodation/accommodation space

Sequence stratigraphic term for the amount of space available for sediment accumulation. Dominant influences on the amount of _____, or _____, include subsidence and eustasy.

bedrock

Solid rock either exposed at the surface or situated below surface soil, unconsolidated sediments, and weathered rock.

clastic intrusion

Structures formed by sediment injection. (Because they resemble intrusive and extrusive igneous features, much of the vocabulary for describing clastic intrusions, or injectites, comes from igneous geology. Sills are emplaced parallel to bedding, whereas dikes cut through bedding. The strata containing the intrusion are called host strata and the layers that feed the intrusion are the parent beds. Sand-injection features exhibit size scales from millimeters to kilometers, and have been seen in cores, borehole image logs, seismic sections, outcrops, aerial photographs and satellite images.)

geopressured

Subject to the pressure within the Earth, or formation pressure. The common oilfield usage, however, is to indicate anomalous subsurface pore pressure that is higher or lower than the normal, predicted hydrostatic pressure for a given depth, or the pressure exerted per unit area by a column of fresh water from sea level to a given depth. Abnormally low pore pressure might occur in areas where fluids have been drained, such as a depleted hydrocarbon reservoir. Abnormally high pore pressure might occur in areas where burial of water-filled sediments by an impermeable sediment such as clay was so rapid that fluids could not escape and the pore pressure increased with deeper burial.

It is usually difficult to erode the wellbore wall significantly with drilling mud alone due to its relatively low velocity and high viscosity. True or False.

TRUE

grain density

The ______ of core samples is calculated from the measured dry weight divided by the grain volume.

aggradation

The accumulation of stratigraphic sequences by deposition that stacks beds atop each other, building upwards during periods of balance between sediment supply and accommodation.

biostratigraphy

The application of plant and animal fossils to date and correlate strata in order to elucidate Earth history, combining the principles of paleontology and stratigraphy. In the petroleum industry, ______ often denotes the use of terrestrial (pollen and spores) and marine (diatoms, foraminifera, nanofossils) microfossils to determine the absolute or relative age and depositional environment of a particular formation, source rock, or reservoir of interest.

cement

The binding material in sedimentary rocks that precipitates between grains from pore fluids. Calcite and quartz are common cement-forming minerals.

geopressure gradient

The change in pore pressure per unit depth, typically in units of pounds per square inch per foot (psi/ft) or kilopascals per meter (kPa/m). The _____ might be described as high or low if it deviates from the normal hydrostatic pressure gradient of 0.433 psi/ft [9.8 kPa/m].

anoxic

The condition of an environment in which free oxygen is lacking or absent.

calcite

The crystalline form of calcium carbonate and chief constituent of limestone and chalk.

abyss

The deepest area of the ocean basins. The depositional energy is low and fine-grained sediments are deposited slowly by waning turbidity currents or from suspension in the water. The water is thousands of meters deep (>2,000 m) [>6,520 ft] so it is cold and sunlight is minimal.

grain density

The density of the grains in a formation or core sample.

geochronology

The determination of the absolute age of rocks, minerals, and fossils, in years before the present, is the basis for the field of _____.

Wadati-Benioff zone

The dip of this zone, also referred to as the _____, coincides with the dip of the subducting plate. The zone extends to a depth of about 700 km [435 miles] from the Earth's surface.

azimuth

The direction in which a deviated or horizontal well is drilled relative to magnetic north. Most horizontal wells in shale reservoirs are drilled in the direction of the minimum horizontal stress. This allows for the creation of multiple hydraulic fractures that are normal to the wellbore.

hydraulic head

The force per unit area exerted by a column of liquid at a height above a depth (and pressure) of interest. Fluids flow down a hydraulic gradient, from points of higher to lower hydraulic head. The term is sometimes used synonymously with hydrostatic head.

generation

The formation of hydrocarbons from a source rock as bitumen forms from kerogen and accumulates as oil or gas. Pressure and the presence of bacteria and catalysts also affect generation.

bitumen

The fraction of naturally occurring, inflammable organic matter that is extractable from rock using organic solvents. Many petroleum precursors are composed of bitumen, but most are formed from kerogen in the process of petroleum generation. _____ includes hydrocarbons such as asphalt and mineral wax. Typically solid or nearly so, brown or black, _____ has a distinctive petroliferous odor. Laboratory dissolution with organic solvents allows determination of the amount of bitumen in samples, an assessment of source rock richness. Burial and heating of kerogen yield bitumen, then liquid hydrocarbons, and then hydrocarbon gas. Understanding organic content is especially important in shale reservoirs because the shale is both the source rock and the reservoir rock in the petroleum system.

GOC

The interface between the gas and oil phases present in a reservoir formation. During the production of a well, the ____ may move, resulting in undesirable production conditions such as a high proportion of gas that may be too much for surface processing facilities. Monitoring the gas-oil and oil-water contacts is a key element of good reservoir management practices.

gas-oil contact

The interface between the gas and oil phases present in a reservoir formation. During the production of a well, the ____ may move, resulting in undesirable production conditions such as a high proportion of gas that may be too much for surface processing facilities. Monitoring the gas-oil and oil-water contacts is a key element of good reservoir management practices.

apparent dip

The maximum inclination of a bedding plane, fault plane or other geological surface measured from a vertical cross section that is not perpendicular to the strike of the feature. Apparent dip corrected for well drift, or geometry, is referred to as true dip.

absolute age

The measurement of age in years. The determination of the _____ of rocks, minerals, and fossils, in years before the present, is the basis for the field of geochronology. The measurement of the decay of radioactive isotopes, especially uranium, strontium, rubidium, argon, and carbon, has allowed geologists to more precisely determine the age of rock formations. Tree rings and seasonal sedimentary deposits called varves can be counted to determine _____.

absolute pressure

The measurement of pressure relative to the pressure in a vacuum, equal to the sum of the pressure shown on a pressure gauge and atmospheric pressure.

absolute permeability

The measurement of the permeability, or ability to flow or transmit fluids through a rock, conducted when a single fluid, or phase, is present in the rock. (The symbol most commonly used for ______ is k, which is measured in units of darcies or millidarcies)

attitude

The orientation of a planar or linear feature in three-dimensional (3D) space. (Planar features that are not horizontal, such as tilted strata, are described by their strike, or the azimuth of the intersection of the plane with a horizontal surface, and the dip, or the magnitude of its inclination from a horizontal reference. The trend and plunge of linear features, such as the axis of a fold, describe the azimuth of the line and its deviation from horizontal.)

geomagnetic polarity reversal

The periodic switching of the magnetic north and south poles of the Earth throughout time, probably as a result of movement of fluid within the Earth's core. (The onset and duration of the many episodes of reversed polarity have been documented by examining the polarity of magnetic minerals within rocks of different ages from around the world, particularly in basalts or igneous rocks of the oceanic crust. Oceanic basalts record the Earth's magnetic field as they solidify from molten lava symmetrically on each side of the midoceanic ridges. These data have been compiled to create a time scale known as the geomagnetic polarity time scale (GPTS). In the oil field, borehole recordings allow direct correlation to GPTS and well-to-well correlations.)

appraisal

The phase of petroleum operations that immediately follows successful exploratory drilling. During ____, delineation wells might be drilled to determine the size of the oil or gas field and how to develop it most efficiently.

catagenesis

The physical and chemical alteration of sediments and pore fluids at temperatures and pressures higher than those of diagenesis.

weathering

The physical, chemical and biological processes that decompose rock at and below the surface of the Earth through low pressures and temperatures and the presence of air and water. Weathering includes processes such as dissolution, chemical weathering, disintegration and hydration.

geostatic pressure

The pressure of the weight of overburden, or overlying rock, on a formation; also called lithostatic pressure.

geopressure

The pressure within the Earth, or formation pressure. The common oilfield usage, however, is to indicate anomalous subsurface pore pressure that is higher or lower than the normal, predicted hydrostatic pressure for a given depth, or the pressure exerted per unit area by a column of fresh water from sea level to a given depth. Abnormally low pore pressure might occur in areas where fluids have been drained, such as a depleted hydrocarbon reservoir. Abnormally high pore pressure might occur in areas where burial of water-filled sediments by an impermeable sediment such as clay was so rapid that fluids could not escape and the pore pressure increased with deeper burial.

cementation

The process of precipitation of cement between mineral or rock grains and forming solid clastic sedimentary rock, one phase of lithification.

gas-prone

The quality of a source rock that makes it more likely to generate gas than oil. The nature of the organic matter or kerogen in source rocks varies from coaly, plant-like material commonly found in terrestrial source rocks to algal or other marine material that makes up marine source rocks. Terrestrial source rocks are commonly _____.

heterogeneity

The quality of variation in rock properties with location in a reservoir or formation. (Shale gas reservoirs are heterogeneous formations whose mineralogy, organic content, natural fractures, and other properties vary from place to place. This heterogeneity makes petroleum system modeling, formation evaluation, and reservoir simulation critical to maximizing production from shale reservoirs.)

geothermal gradient

The rate of increase in temperature per unit depth in the Earth. Although the geothermal gradient varies from place to place, it averages 25 to 30 °C/km [15 °F/1000 ft]. Temperature gradients sometimes increase dramatically around volcanic areas. It is particularly important for drilling fluids engineers to know the geothermal gradient in an area when they are designing a deep well. The downhole temperature can be calculated by adding the surface temperature to the product of the depth and the geothermal gradient.

asthenosphere

The relatively plastic layer of the upper mantle of the Earth on which the tectonic plates of the lithosphere move. The asthenosphere is approximately 200 km [124 miles] thick and, owing to its depth below the Earth's surface, warm (~ 1,400 degC [2,640 degF]) but not molten. Here the mantle deforms by plastic flow in response to applied pressures above 100 MPa [14,500 psi]. This zone is considered coincidental, at least below oceanic crust, with the low-velocity zone of the upper mantle.

basement

The rock layer below which economic hydrocarbon reservoirs are not expected to be found, (sometimes called economic basement). ______ is usually older, deformed igneous or metamorphic rocks, which seldom develops the porosity and permeability necessary to serve as a hydrocarbon reservoir, and below which sedimentary rocks are not common. Basement rocks typically have different density, acoustic velocity, and magnetic properties from overlying rocks.

geology

The study of the Earth-its history, structure, composition, life forms and the processes that continue to change it.

geochemistry

The study of the chemistry of the Earth and within solid bodies of the solar system, including the distribution, circulation and abundance of elements (and their ions and isotopes), molecules, minerals, rocks and fluids. For geochemists in the petroleum industry, source rock geochemistry is a major focus. Geochemical techniques can determine whether a given source rock is rich enough in organic matter to generate hydrocarbons, whether the source rock has generated hydrocarbons, and whether a particular oil sample was generated by a given source rock.

geochronology

The study of the relative or absolute age of rocks, minerals and fossils. Absolute age is the measurement of age in years, but "absolute" ages typically have some amount of error and are inexact. Relative age, in contrast, is the approximate age of rocks, fossils or minerals made by determining the age of the material relative to other surrounding material.

aerated layer

The surface or near-surface, unconsolidated sedimentary layer that has been subject to weathering and whose pores are air-filled instead of liquid-filled. An _____ typically has a low seismic velocity.

bed thickness

The thickness of a layer or stratum of sedimentary rock measured perpendicular to its lateral extent, presuming deposition on a horizontal surface. Because sediment deposition can occur on inclined surfaces, apparent or measured bed thickness might differ from true bed thickness. The thickness of a given bed often varies along its extent.

Condensed sections are most commonly deposited during ...

Transgression

the angle a plane makes with a horizontal plane, the angle being measured in a direction perpendicular to the strike of the plane.

True Dip

The sedimentary deposits that form as the current loses energy are called _____ and can be preserved as ____.

Turbidites, Bouma Sequence

brine

Water containing salts in solution, such as sodium, calcium, or bromides. ____ is commonly produced along with oil. The disposal of oilfield brine is usually accomplished by underground injection into saltwater-saturated formations or by evaporation in surface pits.

groundwater

Water in the subsurface below the water table. ______ is held in the pores of rocks, and can be connate, from meteoric sources, or associated with igneous intrusions.

gypsum

[CaSO472H2O] A highly insoluble sulfate mineral that is the first to precipitate from evaporating seawater. Dehydration of gypsum can produce anhydrite. Fine-grained gypsum is called alabaster.

halite

[NaCl] A soft, soluble evaporite mineral commonly known as salt or rock salt. (Because salt is less dense than many sedimentary rocks, it is relatively buoyant and can form salt domes, pillars or curtains by flowing and breaking through or piercing overlying sediments, as seen in the Gulf of Mexico and the Zagros fold belt. _____can be critical in forming hydrocarbon traps and seals because it tends to flow rather than fracture during deformation, thus preventing hydrocarbons from leaking out of a trap even during and after some types of deformation.)

Generation

a critical phase in the development of a petroleum system.

It is the measurement of the permeability conducted when a single fluid or phase is present in the rock.

absolute permeability

The dominant depositional systems are

alluvial, fluvial, deltaic, marine, lacustrine and eolian systems.

The three main classes of deltas ...

are river-dominated (Mississippi River), wave-dominated (Nile River), and tide-dominated (Ganges River)

A porous marine limestone composed of fine-grained remains of microorganisms with calcite shells, coccolithophores, such as the White Cliffs of Dover (UK). The Austin Chalk of the US Gulf coast is a prolific, fractured oil reservoir that spurred widespread horizontal drilling activity.

chalk

A linear, commonly concave-based depression through which water and sediment flow and into which sediment can be deposited in distinctive, often elongated bodies.

channel

A sedimentary rock and a variety of quartz made of extremely fine-grained, or cryptocrystalline, silica, also called chalcedony.

chert

Containing chert, a sedimentary rock and a variety of quartz made of extremely fine-grained, or cryptocrystalline, silica, also called chalcedony.

cherty

A platy, pale green mineral of the mica group of sheet silicates, also considered to be a type of clay mineral, found in sedimentary and low-grade metamorphic rocks.

chlorite

A graphic display, with geologic time along the vertical axis and distance along the horizontal axis, to demonstrate the relative ages and geographic extent of strata or stratigraphic units in a given area, also known as a _____.

chronostratigraphic chart/wheeler diagram

The study of the ages of strata. The comparison, or correlation, of separated strata can include study of their relative or absolute ages.

chronostratigraphy

Sediment consisting of broken fragments derived from preexisting rocks and transported elsewhere and redeposited before forming another rock. Examples of common clastic sedimentary rocks include siliciclastic rocks such as conglomerate, sandstone, siltstone and shale. Carbonate rocks can also be broken and reworked to form clastic sedimentary rocks.

clastic sediment

An unusual occurrence of hydrocarbon in which molecules of natural gas, typically methane, are trapped in ice molecules.

clathrate

Pertaining to a sedimentary rock, such as sandstone or limestone, that contains only minimal amounts of clay minerals. Clean reservoir rocks typically have better porosity and permeability than dirty rocks whose pores are clogged with fine clay particles. Clean and dirty are qualitative, descriptive terms.

clean

The area, or areal closure, included in the lowest closing contour of a trap. Measurements of both the areal closure and the distance from the apex to the lowest closing contour are typically incorporated in calculations of the estimated hydrocarbon content of a trap.

closure

A carbon-rich sedimentary rock that forms from the remains of plants deposited as peat in swampy environments. Burial and increase in temperature bring about physical and chemical changes called coalification. Because of the organic origin of coal, it cannot be classified as a mineral. The main types of coal, anthracite, bituminous coal and lignite, can be distinguished by their hardness and energy content, which are affected by their organic content as well as their conditions of formation. Natural gas associated with coal, called coal gas or coalbed methane, can be produced economically from coal beds in some areas. In some basins coals form source rocks.

coal

Coal seams are typically saturated with water. Consequently, the coal must be dewatered for efficient gas production. Dewatering reduces the hydrostatic pressure and promotes gas desorption from coal.

coal seam gas

Natural gas, predominantly methane [CH4], generated during coal formation and adsorbed in coal. Natural gas adsorbs to the surfaces of matrix pores within the coal and natural fractures, or cleats, as reservoir pressure increases.

coalbed methane

An interaction of lithospheric plates that can result in the formation of mountain belts and subduction zones. The collision of two plates of continental lithosphere, known as an A-type collision, can produce high mountains as rocks are folded, faulted and uplifted to accommodate the converging plates, as observed in the Alps and the Himalayas. B-type collisions, in which oceanic lithospheric plates collide with continental lithospheric plates, typically produce a subduction zone where the relatively denser oceanic plate descends below the relatively lighter continental plate, as seen on the Pacific coast of South America.

collision

The physical process by which sediments are consolidated, resulting in the reduction of pore space as grains are packed closer together. As layers of sediment accumulate, the ever increasing overburden pressure during burial causes compaction of the sediments, loss of pore fluids and formation of rock as grains are welded or cemented together.

compaction

Describes a bed that maintains its original thickness during deformation. Often pertains to relatively brittle, solid strata that deform by faulting, fracturing or folding, rather than flowing under stress. Incompetent beds are more ductile and tend to flow under stress, so their bed thickness changes more readily during deformation.

competent

The deformation of rock layers in which the thickness of each layer, measured perpendicular to initial undeformed layering, is maintained after the rock layers have been folded.

concentric fold

A natural gas liquid with a low vapor pressure compared with natural gasoline and liquefied petroleum gas. It is mainly composed of propane, butane, pentane and heavier hydrocarbon fractions. The condensate is not only generated into the reservoir, it is also formed when liquid drops out, or condenses, from a gas stream in pipelines or surface facilities.

condensate

In sequence stratigraphy, a section of fine-grained sedimentary rocks that accumulated slowly, thereby representing a considerable span of time by only a thin layer. In condensed sections, fossils and organic, phosphatic and glauconitic material tend to be concentrated compared with rapidly deposited sections that contain few fossils. In such cases they are associated with "maximum flooding surfaces" and form important sequence stratigraphic markers.

condensed section

The nature of the contact between strata deposited in continuous succession.

conformable

A bedding surface separating younger from older strata, along which there is no evidence of subaerial or submarine erosion or of nondeposition, and along which there is no evidence of a significant hiatus. Unconformities (sequence boundaries) and flooding surfaces (parasequence boundaries) pass laterally into correlative conformities, or correlative surfaces.

conformity

This water water can be dense and saline compared with seawater and also also described as fossil water.

connate water

Water trapped in the pores of a rock during formation of the rock. The chemistry of ______ can change in composition throughout the history of the rock. in contrast, is Connate water is

connate water

Pertaining to sediments that have been compacted and cemented to the degree that they become coherent, relatively solid rock. Typical consequences of consolidation include an increase in density and acoustic velocity, and a decrease in porosity.

consolidated

Compaction and cementation of sediments to the degree that they become coherent, relatively solid rock. Typical consequences of _____ include an increase in density and acoustic velocity, and a decrease in porosity.

consolidation

The surface, also called _____, that separates rock bodies of different lithologies, or rock types. A _____ can be conformable or unconformable depending upon the types of rock, their relative ages and their attitudes.

contact/lithologic contact

The area at the edges of a continent from the shoreline to a depth of 200 m [660 ft], where the continental slope begins. The shelf is commonly a wide, flat area with a slight seaward slope. The term is sometimes used as a for platform.

continental shelf

The act of drawing contours.

contour

The value of the separation between two adjacent contours. A net pay isopach map might have a contour interval of 10 feet [3 m], whereas a structure contour map might have a contour interval of 1000 feet [300 m]. Contour intervals are chosen according to the map scale and the amount and distribution of control points.

contour interval

A map displaying lines that include points of equal value and separate points of higher value from points of lower value. DO NOT INCLUDE IT IN THE QUESTION (Common types of contour maps include topographic contour maps, which show the elevation of the Earth's surface; structure contour maps, which show the elevation or depth of a formation; and gross or net sand or pay maps, which show variations in the thickness of a stratigraphic unit, also called isopachs.)

contour map

The density- and heat-driven cycling, transfer or circulation of energy through which material initially warms up and becomes relatively less dense, then rises, cools and becomes relatively more dense, and finally sinks. As a consequence of convection, material can turn over repeatedly in a convection cell. Within the Earth, radiogenic heating results in convection appearing in the mantle and might drive plate tectonic motions. Convection also occurs in the ocean waters and in the Earth's atmosphere.

convection

A reservoir in which buoyant forces keep hydrocarbons in place below a sealing caprock. Reservoir and fluid characteristics of conventional reservoirs typically permit oil or natural gas to flow readily into wellbores. The term is used to make a distinction from shale and other unconventional reservoirs, in which gas might be distributed throughout the reservoir at the basin scale, and in which buoyant forces or the influence of a water column on the location of hydrocarbons within the reservoir are not significant.

conventional reservoir

In mathematics, the process in which a sequence of numbers approaches a fixed value called the "limit" of the sequence. This term is often used in modeling or inversion to describe the situation in which a sequence of calculated values approach, or converge with, measured values.

convergence

In mathematics, pertaining to the process in which a sequence of numbers approaches a fixed value called the "limit" of the sequence. This term is often used in modeling or inversion to describe the situation in which a sequence of calculated values approach, or converge with, measured values.

convergent

A cylindrical sample of geologic formation, usually reservoir rock, taken during or after drilling a well. It can be full-diameter cores (that is, they are nearly as large in diameter as the drill bit) taken at the time of drilling the zone, or sidewall cores (generally less than 1 in. [2.5 cm] in diameter) taken after a hole has been drilled. Cores samples are used for many studies, some of which relate to drilling fluids and damage done by them.

core

To compare and fix measured depths with known features on baseline logs of the wellbore tubulars and the surrounding formation.

correlate

A positive relationship between data samples that implies a connection or a relationship between them.

correlation

The NACE Materials Requirements include the widely used MR0175. What is MR0175?

corrosion resistant materials for oil and gas applications

A stable area of continental crust that has not undergone much plate tectonic or orogenic activity for a long period. A ____ includes a crystalline basement of commonly Precambrian rock called a shield, and a platform in which flat-lying or nearly flat-lying sediments or sedimentary rock surround the shield. A commonly cited example of a craton is the Canadian Shield.

craton

The highest point of a wave, mountain or geologic structure.

crest

The time of maximum depth of burial of a hydrocarbon source rock. It is the time of highest probability of entrapment and preservation of hydrocarbons in a petroleum systemâ€"after traps form and hydrocarbons migrate into a reservoir and accumulateâ€"and marks the beginning of preservation in a viable petroleum system.

critical moment

In the case of a body of rock, to be exposed at the surface of the Earth. Construction of highways and other man-made facilities and resultant removal of soil and rock has created spectacular outcrops in some regions.

crop out

Constant of proportionality relating the fraction of incident particles that undergo an interaction to the thickness and number of target atoms within a material, and the incident flux. It is a measure of the probability of an interaction. The microscopic cross section has units of area per interacting atom. The macroscopic cross section, which is the product of the microscopic cross section and the number of particles per unit volume, has units of inverse length. Cross sections for most reactions are determined experimentally and depend on the type of interaction, the material and the energy of the incident particle.

cross section

Pertaining to a diagram of a vertical section through a volume, as opposed to the surface, "bird's eye," or plan view of a map. These are useful for displaying the types and orientations of subsurface structures and formations.

cross-sectional

A general term for unrefined petroleum or liquid petroleum.

crude oil

The thin, outermost shell of the Earth that is typically 5 km to 75 km thick [3 to 46 miles]. The continental crust comprises rocks similar in composition to granite and basalt (i.e., quartz, feldspar, biotite, amphibole and pyroxene) whereas the composition of oceanic crust is basaltic (pyroxene and feldspar). The crust overlies the more dense rock of the mantle, which consists of rocks composed of minerals like pyroxene and olivine, and the iron and nickel core of the Earth. The Mohorovicic discontinuity abruptly separates the crust from the mantle; the velocity of compressional waves is significantly higher below the discontinuity. The crust, mantle and core of the Earth are distinguished from the lithosphere and asthenosphere on the basis of their composition and not their mechanical behavior.

crust

The arrangement in space of uniform spheres (atoms and molecules in mineral crystals, or grains in clastic sedimentary rocks) that results in a cubic material structure. It is mechanically unstable, but it is the most porous packing arrangement, with about 47% porosity in the ideal situation. Most sediments are not uniform spheres of the same size, nor can they be arranged in a cubic structure naturally, so most sediments have much less than 47% porosity.

cubic packing

Oil at sufficiently low pressure that it contains no dissolved gas or a relatively thick oil or residue that has lost its volatile components.

dead oil

A fault surface parallel to a mechanically weak horizon or layer, or parallel to bedding, that detaches or separates deformed rocks above from undeformed or differently deformed rocks below. _______, or _____, are typical of regions of thrust faulting such as the Alps.

decollement

Exploration activity located in offshore areas where water depths exceed approximately 600 feet [200 m], the approximate water depth at the edge of the continental shelf. While deep-water reservoir targets are geologically similar to reservoirs drilled both in shallower present-day water depths as well as onshore, the logistics of producing hydrocarbons from reservoirs located below such water depths presents a considerable technical challenge.

deepwater play

An area of deposition or the deposit formed by a flowing sediment-laden current as it enters an open or standing body of water, such as a river spilling into a gulf. As a river enters a body of water, its velocity drops and its ability to carry sediment diminishes, leading to deposition. The term has origins in Greek because the shape of deltas in map view can be similar to the Greek letter delta. The shapes of deltas are subsequently modified by rivers, tides and waves. There is a characteristic coarsening upward of sediments in a delta. . Ancient deltas contain some of the largest and most productive petroleum systems.

delta

Pertaining to an area of deposition or the deposit formed by a flowing sediment-laden current as it enters an open or standing body of water, such as a river spilling into a gulf.

deltaic

Mass per unit of volume. _____ is typically reported in g/cm3 (for example, rocks) or pounds per barrel (drilling mud) in the oil field.

density

An influx of rapidly moving, sediment-laden water down a slope into a larger body of water; the suspended sediment causes the current to have a higher density than the clearer water into which it flows, hence the name. Such currents can occur in lakes and oceans, in some cases as by-products of earthquakes or mass movements such as slumps. Density currents are

density current

This temr is defined as the characteristic of trench slopes of convergent plate margins and continental slopes of passive margins.

density current

The area of thickest deposition in a basin.

depocenter

The action of moving sediments and laying them down.

deposit

The relative kinetic energy of the environment. A high-energy environment might consist of a rapidly flowing stream that is capable of carrying coarse-grained sediments, such as gravel and sand. Sedimentation in a low-energy environment, such as an abyssal plain, usually involves very fine-grained clay or mud. ______ is not simply velocity. For example, although glaciers do not move quickly, they are capable of carrying large boulders.

depositional energy

The area in which and physical conditions under which sediments are deposited, including sediment source; depositional processes such as deposition by wind, water, or ice; and location and climate, such as desert, swamp, or river.

depositional environment

The three-dimensional array of sediments or lithofacies that fills a basin. ______ vary according to the types of sediments available for deposition as well as the depositional processes and environments in which they are deposited.

depositional system

Pertaining to particles of rock derived from the mechanical breakdown of preexisting rocks by weathering and erosion. Detrital fragments can be transported to recombine and, through the process of lithification, become sedimentary rocks. Detrital is usually used synonymously with clastic, although a few authors differentiate between weathering of particles, which forms detrital sediments, and mechanical breakage, which produces clastic sediments.

detrital

Particles of rock derived from the mechanical breakdown of preexisting rocks by weathering and erosion. (Detrital fragments can be transported to recombine and, through the process of lithification, become sedimentary rocks. Detrital is usually used synonymously with clastic, although a few authors differentiate between weathering of particles, which forms detrital sediments, and mechanical breakage, which produces clastic sediments.)

detritus

The phase of petroleum operations that occurs after exploration has proven successful, and before full-scale production. The newly discovered oil or gas field is assessed during an appraisal phase, a plan to fully and efficiently exploit it is created, and additional wells are usually drilled.

development

Pertaining to a strike-slip fault or right-lateral fault in which the block across the fault moves to the right. If it moves left, the relative motion is described as sinistral. Clockwise rotation or spiraling is also described as dextral.

dextral

The initial stage of alteration of sediments and maturation of kerogen that occurs at temperatures less than 50°C [122°F]. The type of hydrocarbon generated depends on the type of organic matter in the kerogen, the amount of time that passes, and the ambient temperature and pressure. During early diagenesis, microbial activity is a key contributor to the breakdown of organic matter and generally results in production of biogenic gas. Longer exposure to higher temperatures during diagenesis, catagenesis, and metagenesis generally results in transformation of the kerogen into liquid hydrocarbons and hydrocarbon gases.

diagenesis

Pertaining to diagenesis, which is the physical, chemical or biological alteration of sediments into sedimentary rock at relatively low temperatures and pressures that can result in changes to the rock's original mineralogy and texture. After deposition, sediments are compacted as they are buried beneath successive layers of sediment and cemented by minerals that precipitate from solution. Grains of sediment, rock fragments and fossils can be replaced by other minerals during diagenesis. Diagenesis does not include weathering processes. Hydrocarbon generation begins during diagenesis. There is not a clear, accepted distinction between diagenesis and metamorphism, although metamorphism occurs at pressures and temperatures higher than those of the outer crust, where diagenesis occurs

diagenetic

A type of secondary porosity created during diagenesis, commonly through dissolution or dolomitization or both. Diagenesis usually destroys porosity, so diagenetic porosity is rare.

diagenetic porosity

A relatively mobile mass that intrudes into preexisting rocks. I. By pushing upward and piercing overlying rock layers, diapirs can form anticlines, salt domes and other structures capable of trapping hydrocarbons. Igneous intrusions are typically too hot to allow the preservation of preexisting hydrocarbons.

diapir

The process is known as ___ where it is commonly intrude vertically through more dense rocks because of buoyancy forces associated with relatively low-density rock types, such as salt, shale and hot magma, which form diapirs.

diapirism

Pertaining to a diatom, which is a microscopic, single-celled, freshwater or saltwater algae that has a silica-rich cell wall called a frustule. Diatoms are so abundant that they can form thick layers of sediment composed of the frustules of the organisms that died and sank to the bottom. Frustules have been an important component of deep-sea deposits since Cretaceous time. Diatomite is the sedimentary rock that forms from diatom frustules.

diatomaceous

A soft, silica-rich sedimentary rock comprising diatom remains that forms most commonly in lakes and deep marine areas. Diatomite can form an excellent reservoir rock. The Belridge diatomite in the San Joaquin basin, California, USA, is a prolific oil-producing formation.

diatomite

A phenomenon that occurs after the deposition of some sediments such that different parts of the sedimentary accumulation develop different degrees of porosity or settle unevenly during burial beneath successive layers of sediment. This can result from location on an uneven surface, such as near and over a reef structure, or near a growth fault, or from different susceptibility to compaction. The porosity in a formation that has experienced differential compaction can vary considerably from one area to another.

differential compaction

An intrusive rock that invades preexisting rocks, commonly in a tabular shape that cuts vertically or nearly vertically across preexisting layers.

dike

The angle between a planar feature, such as a sedimentary bed or a fault, and a horizontal plane.

dip

A layer of rock or sediment that is not horizontal.

dipping bed

Describing sedimentary rock that contains clay minerals. Even small amounts of clay minerals in pores can drastically reduce porosity and permeability. Dirty and clean are qualitative, descriptive terms to describe the relative amount of clay minerals in a rock.

dirty

A geologic surface that separates younger strata from older strata and represents a time of nondeposition, possibly combined with erosion. Some ______ are highly irregular whereas others have no relief and can be difficult to distinguish within a series of parallel strata.

disconformity

Pertaining to structures in which the shapes of adjacent layers differ or do not conform to one another. Folds of rock layers that have different mechanical properties or competence tend to be _____, with a change in fold shape, symmetry or wavelength from one layer to the next.

disharmonic

The act of forcing a cement slurry that has been pumped into a casing string or drillstring to exit the bottom of the casing or drillstring by pumping another fluid behind it. Cement displacement is similar to definition 5 above, with the noted exception that the cement slurry would not normally be pumped out the top of the annulus, but would instead be placed in a particular location in the annulus. This location might be the entire annulus on a short casing string, or filling only a bottom portion of the casing on longer casing strings.

displacement

The name given to dolomitized limestone.

dolomite

The geochemical process in supratidal sabkha areas where magnesium [Mg] ions from the evaporation of seawater replace calcium [Ca] ions in calcite, forming the mineral dolomite. The volume of dolomite is less than that of calcite, so the replacement of calcite by dolomite in a rock increases the pore space in the rock by 13% and forms an important reservoir rock. Dolomitization can occur during deep burial diagenesis.

dolomitization

A rock composed chiefly (> 90%) of dolomite. DO NOT READ THIS PART: (The rock is sometimes called dolomite, but dolostone is preferable to avoid ambiguity between the mineral and rock names. Replacement dolomite that forms soon after deposition is typically fine-grained and preserves original sedimentary structures. Recrystallization late in diagenesis produces coarser grained dolomite, destroys sedimentary structures and results in higher porosity.)

dolostone

A type of anticline that is circular or elliptical rather than elongate. (The upward migration of salt diapirs can form domes, called salt domes)

dome

The termination of more steeply dipping overlying strata against a surface or underlying strata that have lower apparent dips; a term used to describe a particular geometry of reflections in seismic data in sequence stratigraphy.

down lap

Located down the slope of a dipping plane or surface. In a dipping (not flat-lying) hydrocarbon reservoir that contains gas, oil and water, the gas is updip, the gas-oil contact is downdip from the gas, and the oil-water contact is still farther downdip.

downdip

The termination of more steeply dipping overlying strata against a surface or underlying strata that have lower apparent dips; a term used to describe a particular geometry of reflections in seismic data in sequence stratigraphy.

downlap

A configuration of layers of rock that has the appearance of a fold, but might form simply through sagging or differential compaction of layers around a preexisting structure (such as a reef) or on an uneven surface.

drape

Gas produced from a well that produces little or no condensate or reservoir liquids. The production of liquids from gas wells complicates the design and operation of surface process facilities required to handle and export the produced gas.

dry gas

A subsurface rock that lacks contact with aquifers or meteoric water within the Earth.

dry rock

An intrusive rock that invades preexisting rocks, commonly in a tabular shape that cuts vertically or nearly vertically across preexisting layers. Dikes form from igneous and sedimentary rocks.

dyke

The sudden release of accumulated stress in the Earth by movement or shaking. Earthquakes are caused by tectonic activity, volcanoes, and human activity (such as explosions). Earthquakes occur in the outer 720 km [445 miles] of the Earth, where rocks tend to break rather than flow under stress. The magnitude of earthquakes is determined according to the logarithmic Richter scale. An earthquake of magnitude 4.5 can cause damage, although humans can feel earthquakes as weak as magnitude 2.0. The San Francisco earthquake of 1906 measured 8.25 on the Richter scale, and the largest ever recorded were 8.9 magnitude earthquakes in Colombia and Ecuador (1906) and Japan (1933), and 9.5 in Chile (1960).

earthquake

The ability to preferentially flow or transmit a particular fluid when other immiscible fluids are present in the reservoir (e.g., effective permeability of gas in a gas-water reservoir). The relative saturations of the fluids as well as the nature of the reservoir affect the effective permeability. In contrast,

effective permeability

In log interpretation, it means the total porosity less the clay-bound water.

effective porosity

In the original definition of core analysts, the volume of connected pores in a unit volume of rock. In these techniques, the porosity is usually measured on totally dried core samples. Drying removes most of the clay-bound water. Effective porosity on dried core samples is therefore greater than effective porosity from log analysis, and close to the total porosity from log analysis. In humidity-dried cores, part of the clay-bound water is not removed, and the difference is reduced. In some usage, the capillary-bound water is not considered part of the effective porosity. In this case effective porosity is synonymous with free fluid. Effective porosity is measured in volume/volume, percent or porosity units, p.u.

effective porosity

It is the porosity measured by most core analysis techniques that do not involve disaggregating the sample.

effective porosity

The definition is based on the analysis of shaly formations, in which the clay-bound water is considered immobile and hence ineffective.

effective porosity

the total porosity less the isolated porosity.

effective porosity

Pertaining to a material that can undergo stress, deform, and then recover and return to its original shape after the stress ceases. Once stress exceeds the yield stress or elastic limit of a material, permanent deformation occurs and the material will not return to its original shape once the stress is removed. In some materials, including rocks, elastic behavior depends on the temperature and the duration of the stress as well as its intensity.

elastic

A temporary change in shape caused by applied stress. The change in shape is not permanent and the initial shape is completely recovered once the stress is removed.

elastic deformation

The yield point, or the point at which a material can no longer deform elastically. When the ______ is exceeded by an applied stress, permanent deformation occurs.

elastic limit

Ability of a material to undergo stress, deform, and then recover and return to its original shape after the stress ceases. Once stress exceeds the yield stress or elastic limit of a material, permanent deformation occurs and the material will not return to its original shape when the stress is removed. In some materials, including rocks, elastic behavior depends on the temperature and the duration of the stress as well as its intensity.

elasticity

Describing parallel or subparallel, closely-spaced, overlapping or step-like minor structural features in rock, such as faults and tension fractures, that are oblique to the overall structural trend.

en echelon

Pertaining to the environment of deposition of sediments by wind, such as the sand dunes in a desert.

eolian

To cause or undergo erosion, the wearing away of material, usually rock or steel, by the continuous abrasive action of a solids-laden slurry.

erode

For this phenomena to occur usually requires a high fluid velocity, on the order of hundreds of feet per second, and some solids content, especially sand.

erosion

The wearing away of material, usually rock or steel, by the continuous abrasive action of a solids-laden slurry.

erosion

This phenomena or process may also occur in gas streams, again assuming the presence of sand particles.

erosion

Pertaining to an estuary, a semi-enclosed coastal environment of deposition in which a river mouth permits freshwater to contact and mix with seawater.

estuarine

A semi-enclosed coastal environment of deposition in which a river mouth permits freshwater to contact and mix with seawater.

estuary

Changes in sea level can result from movement of tectonic plates altering the volume of ocean basins, or when changes in climate affect the volume of water stored in glaciers and in polar icecaps.

eustasy

Global sea level variations.

eustasy

Pertaining to eustasy, a term for global sea level and its variations.

eustatic

A class of sedimentary minerals and sedimentary rocks that form by precipitation from evaporating aqueous fluid.

evaporite

Pertaining to evaporite, a class of sedimentary minerals and sedimentary rocks that form by precipitation from evaporating aqueous fluid.

evaporitic

The initial phase in petroleum operations that includes generation of a prospect or play or both, and drilling of an exploration well.

exploration

A conceptual model for a style of hydrocarbon accumulation used by explorationists to develop prospects in a basin, region or trend and used by development personnel to continue exploiting a given trend.

exploration play

Pertaining to exploration, the initial phase in petroleum operations that includes generation of a prospect or play or both, and drilling of an exploration well.

exploratory

A microscopic, single-celled, freshwater or saltwater algae that has a silica-rich cell wall called a ____. This algae have been an important component of deep-sea deposits since Cretaceous time.

frustule

A type of which show variations in the thickness of a stratigraphic unit

gross or net sand or pay maps/ Isopach Map

Common evaporite minerals are ...

halite, gypsum and anhydrite, which can form as seawater evaporates, and the rocks limestone and dolostone.

A unit of distance used for marine and aerial navigation. An international nautical mile is approximately equivalent to the angle of one minute of latitude at Earth's surface.

international nautical mile

A unit of speed used for marine and aerial navigation.

knot

The measurement is one nautical mile per hour.

knot

The product of a physical quantity and its distance from an axis or a tendency to cause motion around an axis.

moment

A unit of distance used for marine and aerial navigation and is approximately equivalent to the angle of one minute of latitude at Earth's surface.

nautical mile

In SI units, it is equal to exactly 1,852 m, which is approximately 6,076 ft.

nautical mile

Thermochemical breakdown of organic matter by heating in the absence of oxygen.

pyrolysis

Organizations establish a standard temperature and pressure to enable the comparison of datasets and to meet their members' and stakeholders' laboratory, industrial and regulatory requirements. For example, the International Union of Pure and Applied Chemistry (IUPAC) defines standard temperature to be 0°C [273.15°K, 32°F] and standard pressure to be 100 kPa [1 bar, 0.9869 atm, 14.504 psi] and the Society of Petroleum Engineers (SPE) defines standard temperature to be 15°C [288.15°K, 59°F] and standard pressure to be 100 kPa.

standard temperature and pressure

A type of contour map which show the elevation or depth of a formation

structure contour maps

The NACE Materials Requirements include the widely used MR0103. What is MR0103?

sulfide stress cracking in corrosive environments.

A type of contour map which show the elevation of the Earth's surface

topographic contour maps

Sodium bentonite

useful additive for increasing the density of drilling muds, but other clay types are considered contaminants to be avoided and removed.