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drape

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.

en echelon

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.

dirty

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.

downdip

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.

MR0103

Sulfide stress cracking in corrosive environments.

depositional energy

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.

development

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.

diapirism

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.

moment

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

erosion

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

erode

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

Diatom

_____ 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.

Diatomite

the sedimentary rock that forms from diatom frustules.

effective porosity

the total porosity less the isolated porosity.

exploration play

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.

evaporite

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

disconformity

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.

dipping bed

A layer of rock or sediment that is not horizontal.

elastic deformation

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.

frustule

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.

differential compaction

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.

diapir

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.

dolostone

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.)

estuary

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

diatomite

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.

dry rock

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

dome

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

diagenetic porosity

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

nautical mile

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.

international nautical mile

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.

knot

A unit of speed used for marine and aerial navigation.

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

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.

1943

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.

STP

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.

elasticity

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.

API Recommended Practices ("RPs")

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

density current

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

dike

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

dyke

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.

Halite

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).

eustasy

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.

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

Common evaporite minerals are ...

MR0175

Corrosion resistant materials for oil and gas applications

deepwater play

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.

erosion

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.

dry gas

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.

Apparent Dip

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

eustasy

Global sea level variations.

nautical mile

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

effective porosity

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.

Isolated Porosity

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

absolute permeability

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

effective porosity

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

TRUE

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.

density

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

dead oil

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

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.

detritus

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.)

diatomaceous

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.

elastic

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.

dextral

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.

estuarine

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

diagenetic

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

eustatic

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

evaporitic

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

exploratory

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.

detrital

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.

disharmonic

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.

eolian

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

dissolution of minerals and dolomitization.

Porosity usually decreases during diagenesis, except in rare cases such as ...

API Specifications ("Specs")

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 ________.

sulfide stress cracking in corrosive environments.

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

corrosion resistant materials for oil and gas applications

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

effective permeability

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,

displacement

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.

deposit

The action of moving sediments and laying them down.

dip

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

depositional environment

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.

depocenter

The area of thickest deposition in a basin.

nautical mile

The conventional value for the nautical mile was established at the First International Extraordinary Hydrographic Conference held in the Principality of Monaco in 1929 and named the international nautical mile.

1929

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

Principality of Monaco

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

First International Extraordinary Hydrographic Conference

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

effective porosity

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

dolomitization

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.

exploration

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

diagenesis

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.

knot

The measurement is one nautical mile per hour.

dolomite

The name given to dolomitized limestone.

earthquake

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).

down lap

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

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.

Gas initially in place (GIIP)

The volume of gas in a reservoir before production.

erosion

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

elastic limit

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.

pyrolysis

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

True Dip

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

Apparent Dip

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