1D, 2D, 3C, 4C, and 3D Seismic Data

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Questions and Answers

What is a single seismic trace?

1-D seismic data

What is a check-shot survey used for?

To correct the sonic log and generate a synthetic seismogram that displays changes in amplitude versus traveltime.

What is a vertical section of seismic data consisting of numerous adjacent traces acquired sequentially?

2D seismic data

What is the term for a group of 2D seismic lines acquired individually?

<p>2D seismic data</p> Signup and view all the answers

What is a seismic data or a group of seismic lines acquired individually with significant gaps between adjacent lines?

<p>2D survey</p> Signup and view all the answers

What is a type of multicomponent seismic data acquired using three orthogonally oriented geophones or accelerometers?

<p>3C seismic data</p> Signup and view all the answers

What type of seismic data is a set of numerous closely-spaced seismic lines that provide a high spatially sampled measure of subsurface reflectivity?

<p>3D seismic data</p> Signup and view all the answers

What is the process of acquiring seismic data as closely spaced receiver and shot lines such that there typically are no significant gaps in the subsurface coverage?

<p>3D survey</p> Signup and view all the answers

How is four-component (4C) borehole or marine seismic data typically acquired?

<p>Using three orthogonally-oriented geophones and a hydrophone within an ocean-bottom sensor.</p> Signup and view all the answers

What are three-dimensional (3D) seismic data acquired at different times over the same area for?

<p>To assess changes in a producing hydrocarbon reservoir with time.</p> Signup and view all the answers

What term indicates features in seismic data other than reflections?

<p>Abnormal events</p> Signup and view all the answers

What is the range of wavelengths of energy that can be absorbed by a given substance?

<p>Absorption band</p> Signup and view all the answers

What is an algorithm used in numerical simulation along the boundary of a computational domain to absorb all energy incident upon that boundary and to suppress reflection artifacts?

<p>Absorbing boundary conditions</p> Signup and view all the answers

What is the ratio of absorbed incident energy to the total energy to which a body is exposed?

<p>Absorptance</p> Signup and view all the answers

What is the property of some liquids or solids to soak up water or other fluids?

<p>Absorption</p> Signup and view all the answers

What term refers to the conversion of one form of energy into another as the energy passes through a medium?

<p>Absorption</p> Signup and view all the answers

What is a device used during surveying to measure the acceleration of a ship or aircraft?

<p>Accelerometer</p> Signup and view all the answers

What is the term relating to sound?

<p>Acoustic</p> Signup and view all the answers

In geophysics, what does acoustic refer to specifically?

<p>P-waves in the absence of S-waves</p> Signup and view all the answers

What obsolete piece of equipment converts acoustic signals from analog to electrical form and back?

<p>Acoustic coupler</p> Signup and view all the answers

What is a type of elastic wave produced by deformation or brittle failure of material and characterized by relatively high frequency?

<p>Acoustic emission</p> Signup and view all the answers

What is the product of density and seismic velocity called?

<p>Acoustic impedance</p> Signup and view all the answers

What is a seismic reflectivity section that has been inverted for acoustic impedance?

<p>Acoustic impedance section</p> Signup and view all the answers

What type of display shows traveltime of acoustic waves versus depth in a well?

<p>Acoustic log</p> Signup and view all the answers

What type of record shows some acoustic property of the formation or borehole?

<p>Acoustic log / acoustic velocity log</p> Signup and view all the answers

What is a method of calculating the position of marine seismic equipment?

<p>Acoustic positioning</p> Signup and view all the answers

What is the quality of a medium whose acoustic impedance is constant throughout called?

<p>Acoustic transparency</p> Signup and view all the answers

What is the duration of the passage of a signal from the source through the Earth and back to the receiver referred to as?

<p>Acoustic traveltime</p> Signup and view all the answers

What is the rate at which a sound wave travels through a medium?

<p>Acoustic velocity</p> Signup and view all the answers

What is an elastic body wave or sound wave in which particles oscillate in the direction the wave propagates?

<p>Acoustic wave / dilatational wave</p> Signup and view all the answers

What is generation and recording of seismic data called?

<p>Acquisition</p> Signup and view all the answers

What is surface or near-surface, unconsolidated sedimentary layer that has been subject to weathering and whose pores are air-filled instead of liquid-filled?

<p>Aerated layer</p> Signup and view all the answers

What are measurements of the Earth's magnetic field gathered from aircraft?

<p>Aeromagnetic survey</p> Signup and view all the answers

What does AGC stand for?

<p>Automatic gain control</p> Signup and view all the answers

What is exponential rate constant (Ï„) called?

<p>AGC time constant</p> Signup and view all the answers

What is source of seismic energy used in acquisition of marine seismic data which releases highly compressed air into water?

<p>Air gun</p> Signup and view all the answers

What is method of seismic acquisition using charges detonated in the air or on poles above the ground as the source?

<p>Air shooting</p> Signup and view all the answers

What is a sound wave that travels through the air at approximately 330 m/s called?

<p>Air wave</p> Signup and view all the answers

What is a filter, or a set of limits used to eliminate unwanted portions of the spectra of the seismic data called?

<p>Alias filter</p> Signup and view all the answers

What is the distortion of frequency introduced by inadequately sampling a signal called?

<p>Aliasing</p> Signup and view all the answers

What is the difference between the maximum displacement of a wave and the point of no displacement, or the null point called?

<p>Amplitude</p> Signup and view all the answers

What is abrupt increase in seismic amplitude that can indicate the presence of hydrocarbons called?

<p>Amplitude anomaly / bright spot</p> Signup and view all the answers

What is a change in the amplitude of a waveform that is generally undesirable called?

<p>Amplitude distortion</p> Signup and view all the answers

What is the inability of a system to exactly match input and output amplitude called?

<p>Amplitude distortion</p> Signup and view all the answers

What is azimuthal variation of the AVO response called?

<p>Amplitude variation with offset and azimuth / AVOAZ</p> Signup and view all the answers

What is variation in seismic reflection amplitude with change in distance between shotpoint and receiver called?

<p>Amplitude variation with offset/ AVO</p> Signup and view all the answers

What is the acute angle at which a wavefront impinges upon an interface called?

<p>Angle of approach</p> Signup and view all the answers

What is the acute angle at which a raypath impinges upon a line normal to an interface called?

<p>Angle of incidence</p> Signup and view all the answers

What is the variation of seismic velocity in different directions called?

<p>Angular dispersion / seismic velocity</p> Signup and view all the answers

What means having directionally dependent properties?

<p>Anisotropic</p> Signup and view all the answers

What is predictable variation of a property of a material with the direction in which it is measured?

<p>Anisotropy/ aeolotropy</p> Signup and view all the answers

What is a portion of a data set, such as seismic data, to which functions or filters are applied called?

<p>Aperture/ window</p> Signup and view all the answers

What is a mechanism to limit the affects of measurements on a device or system?

<p>Aperture/ window</p> Signup and view all the answers

What is the ratio of the velocity determined from normal moveout to velocity measured vertically called?

<p>Apparent anisotropy</p> Signup and view all the answers

In geophysics, what is the velocity of a wavefront in a certain direction called?

<p>Apparent velocity</p> Signup and view all the answers

What is the wavelength measured by receivers when a wave approaches at an angle called?

<p>Apparent wavelength</p> Signup and view all the answers

What is a technique to map a potential field generated by stationary electrodes by moving an electrode around the survey area called?

<p>Applied-potential method</p> Signup and view all the answers

In computing, what is code written to access data in more than one dimension according to a name and subscripts that correspond to each dimension called?

<p>Array</p> Signup and view all the answers

What is geometrical arrangement of seismic sources called?

<p>Array</p> Signup and view all the answers

What is an arrangement or configuration of electrodes or antennas used for resistivity, induced polarization (IP), or other types of electromagnetic surveying called?

<p>Array</p> Signup and view all the answers

What is a geometrical configuration of transducers (sources or receivers) used to generate or record a physical field called?

<p>Array/ nest</p> Signup and view all the answers

What is the elapsed time between the release of seismic energy from a source and its arrival at the receiver?

<p>Arrival time</p> Signup and view all the answers

What is the removal of undesirable features, such as multiple events, from seismic data called?

<p>Attenuate/ attenuation</p> Signup and view all the answers

What is the loss of energy or amplitude of waves as they pass through media called?

<p>Attenuation</p> Signup and view all the answers

What is the reduction in amplitude of an electromagnetic wave passing through the formation called?

<p>Attenuation/ attenuate</p> Signup and view all the answers

What is a measurable property of seismic data called?

<p>Attribute</p> Signup and view all the answers

What is the comparison of a waveform to itself called?

<p>Autocorrelation</p> Signup and view all the answers

What is a system to control the gain automatically called?

<p>Automatic gain control</p> Signup and view all the answers

What is using computer software to pick a particular reflection or attribute in seismic data automatically called?

<p>Autotrack</p> Signup and view all the answers

In geophysics, what is the depth divided by the traveltime of a wave to that depth called?

<p>Average velocity</p> Signup and view all the answers

What is an axis of rotational invariance?

<p>axis of rotational symmetry</p> Signup and view all the answers

What is a method for reconstructing the location and shape of the wave at an earlier time using the wave equation?

<p>back propagation</p> Signup and view all the answers

What is a modeling technique to assess the geologic history of rock layers through the use of geologic cross sections or seismic sections?

<p>back stripping</p> Signup and view all the answers

What kind of phenomenon of energy in which a nonreflective surface, which is a surface that does not reflect energy coherently, randomly scatters energy.

<p>backscatter</p> Signup and view all the answers

What is a range of frequencies or wavelengths?

<p>band</p> Signup and view all the answers

What is a function or time series whose Fourier transform is restricted to a finite range of frequencies or wavelengths?

<p>band-limited function</p> Signup and view all the answers

What is Frequencies within the acceptable limits of a filter.

<p>band-pass</p> Signup and view all the answers

What is Frequencies beyond the limits of a filter?

<p>band-reject</p> Signup and view all the answers

What is the lower boundary of the near-surface, low-velocity zone in which rocks are physically, chemically or biologically broken down?

<p>base of weathering</p> Signup and view all the answers

What is a reference location for a survey called?

<p>base station</p> Signup and view all the answers

What is a line joining base stations whose transmissions are synchronized during surveying?

<p>baseline</p> Signup and view all the answers

What is a reference line, such as a "shale baseline,", called?

<p>baseline</p> Signup and view all the answers

What is the original survey of a set of surveys covering the same area but acquired over a period of time?

<p>baseline</p> Signup and view all the answers

What is the shape of a wavelet produced by reflection of an actual wave train at one interface with a positive reflection coefficient?

<p>basic wavelet/ embedded wavelet</p> Signup and view all the answers

What does the 0 to 12 scale for measurement of wind strength according to its effect on objects such as trees, flags and water measure?

<p>Beaufort scale</p> Signup and view all the answers

What is the unit of measurement to describe or compare the intensity of acoustic or electrical signal called?

<p>bel</p> Signup and view all the answers

What is a permanently fixed marker cited in surveying called?

<p>benchmark/ BM</p> Signup and view all the answers

What is a standard against which the performance of processes are measured called?

<p>benchmark/ BM</p> Signup and view all the answers

What is An adjustment of the relative positive and negative excursions of reflections during seismic processing by bulk shifting the null point, or baseline, of the data to emphasize peaks at the expense of troughs or vice versa?

<p>bias</p> Signup and view all the answers

What is To sort seismic data into small areas according to the midpoint between the source and the receiver, reflection point or conversion point prior to stacking?

<p>bin</p> Signup and view all the answers

What is a subdivision of a seismic survey?

<p>bin</p> Signup and view all the answers

What is a device containing a magnetometer and possibly other instruments that can be towed by an aircraft during aeromagnetic surveying?

<p>bird</p> Signup and view all the answers

What is a check-shot survey of a well used for?

<p>To correct the sonic log and generate a synthetic seismogram that displays changes in amplitude versus traveltime.</p> Signup and view all the answers

What seismic data consist of a group of 2D seismic lines acquired individually?

<p>2D seismic data</p> Signup and view all the answers

What is a 2D survey?

<p>Seismic data or a group of seismic lines acquired individually such that there typically are significant gaps (commonly 1 km or more) between adjacent lines. A 2D survey typically contains numerous lines acquired orthogonally to the strike of geological structures (such as faults and folds) with a minimum of lines acquired parallel to geological structures to allow line-to-line tying of the seismic data and interpretation and mapping of structures.</p> Signup and view all the answers

What is 3C seismic data?

<p>A type of multicomponent seismic data acquired in a land, marine, or borehole environment by using three orthogonally oriented geophones or accelerometers. 3C is particularly appropriate when the addition of a hydrophone (the basis for 4C seismic data) adds no value to the measurement, as for example, on land. This technique allows determination of both the type of wave and its direction of propagation.</p> Signup and view all the answers

Describe 4C seismic data.

<p>Four-component (4C) borehole or marine seismic data are typically acquired using three orthogonally-oriented geophones and a hydrophone within an ocean-bottom sensor (deployed in node-type systems as well as cables). Provided the system is in contact with the seabed or the borehole wall, the addition of geophones allows measurement of shear (S) waves, whereas the hydrophone measures compressional (P) waves.</p> Signup and view all the answers

What are abnormal events in seismic data?

<p>A term to indicate features in seismic data other than reflections, including events such as diffractions, multiples, refractions and surface waves. Although the term suggests that such events are not common, they often occur in seismic data.</p> Signup and view all the answers

What is an absorption band?

<p>The range of wavelengths of energy that can be absorbed by a given substance.</p> Signup and view all the answers

What are absorbing boundary conditions?

<p>An algorithm used in numerical simulation along the boundary of a computational domain to absorb all energy incident upon that boundary and to suppress reflection artifacts.</p> Signup and view all the answers

What is absorptance?

<p>The ratio of absorbed incident energy to the total energy to which a body is exposed.</p> Signup and view all the answers

Define absorption in the context of seismic waves.

<p>The conversion of one form of energy into another as the energy passes through a medium. For example, seismic waves are partially converted to heat as they pass through rock.</p> Signup and view all the answers

What is an accelerometer?

<p>A device used during surveying to measure the acceleration of a ship or aircraft, or to detect ground acceleration in boreholes or on the Earth's surface produced by acoustic vibrations.</p> Signup and view all the answers

How is the term 'acoustic' generally defined?

<p>Pertaining to sound. Generally, acoustic describes sound or vibrational events, regardless of frequency. The term sonic is limited to frequencies and tools operated in the frequency range of 1 to 25 kilohertz.</p> Signup and view all the answers

What does the term 'acoustic' specifically refer to in geophysics?

<p>In geophysics, acoustic refers specifically to P-waves in the absence of S-waves (i.e., in fluids, which do not support S-waves, or in cases in which S-waves in solids are ignored).</p> Signup and view all the answers

What was an acoustic coupler used for?

<p>An obsolete piece of equipment that converts acoustic signals from analog to electrical form and back. A common use of an acoustic coupler was to provide an interface between a telephone and an early type of computer modem.</p> Signup and view all the answers

What is acoustic emission?

<p>A type of elastic wave produced by deformation or brittle failure of material and characterized by relatively high frequency.</p> Signup and view all the answers

What is acoustic impedance?

<p>The product of density and seismic velocity, which varies among different rock layers, commonly symbolized by Z. The difference in acoustic impedance between rock layers affects the reflection coefficient.</p> Signup and view all the answers

What is an acoustic impedance section?

<p>A seismic reflectivity section, or a 2D or 3D seismic section, that has been inverted for acoustic impedance. Sonic and density logs can be used to calibrate acoustic impedance sections.</p> Signup and view all the answers

What is an acoustic log?

<p>A display of traveltime of acoustic waves versus depth in a well. The term is commonly used as a synonym for a sonic log. Some acoustic logs display velocity.</p> Signup and view all the answers

Describe an acoustic log / or acoustic velocity log

<p>A record of some acoustic property of the formation or borehole. The term is sometimes used to refer specifically to the sonic log, in the sense of the formation compressional slowness. However, it may also refer to any other sonic measurement, for example shear, flexural and Stoneley slownesses or amplitudes, or to ultrasonic measurements such as the borehole televiewer and other pulse-echo devices, and even to noise logs.</p> Signup and view all the answers

What is acoustic positioning used for?

<p>A method of calculating the position of marine seismic equipment. Range measurements are made whereby distance is equal to acoustic signal traveltime from transmitter to hydrophone multiplied by the speed of sound in water. When sufficient acoustic ranges with a proper geometric distribution are collected, location coordinates x, y and z of the marine seismic equipment can be computed by the method of trilateration (measuring the lengths of the sides of overlapping triangles). Acoustic positioning is commonly used in towed streamer and ocean-bottom cable seismic acquisition modes.</p> Signup and view all the answers

What is acoustic transparency?

<p>The quality of a medium whose acoustic impedance is constant throughout, such that it contains no seismic reflections. An example of an acoustically transparent medium is water.</p> Signup and view all the answers

What does acoustic travel time refer to?

<p>The duration of the passage of a signal from the source through the Earth and back to the receiver. A time seismic section typically shows the two-way traveltime of the wave.</p> Signup and view all the answers

Explain acoustic velocity.

<p>The rate at which a sound wave travels through a medium. Unlike the physicist's definition of velocity as a vector, its usage in geophysics is as a property of a medium: distance divided by traveltime. Velocity can be determined from laboratory measurements, acoustic logs, vertical seismic profiles or from velocity analysis of seismic data. It can vary vertically, laterally and azimuthally in anisotropic media such as rocks, and tends to increase with depth in the Earth because compaction reduces porosity. Velocity also varies as a function of how it is derived from the data. For example, the stacking velocity derived from normal moveout measurements of common depth point gathers differs from the average velocity measured vertically from a check-shot or vertical seismic profile (VSP). Velocity would be the same only in a constant-velocity (homogeneous) medium.</p> Signup and view all the answers

What is a synonymous term for acoustic log?

<p>A display of traveltime of acoustic waves versus depth in a well. The term is commonly used as a synonym for a sonic log. Some acoustic logs display velocity.</p> Signup and view all the answers

What is an acoustic wave/dilatational wave?

<p>An elastic body wave or sound wave in which particles oscillate in the direction the wave propagates. P-waves are the waves studied in conventional seismic data. P-waves incident on an interface at other than normal incidence can produce reflected and transmitted S-waves, in that case known as converted waves.</p> Signup and view all the answers

Explain the term 'acquisition'.

<p>The generation and recording of seismic data. Acquisition involves many different receiver configurations, including laying geophones or seismometers on the surface of the Earth or seafloor, towing hydrophones behind a marine seismic vessel, suspending hydrophones vertically in the sea or placing geophones in a wellbore (as in a vertical seismic profile) to record the seismic signal. A source, such as a vibrator unit, dynamite shot, or an air gun, generates acoustic or elastic vibrations that travel into the Earth, pass through strata with different seismic responses and filtering effects, and return to the surface to be recorded as seismic data. Optimal acquisition varies according to local conditions and involves employing the appropriate source (both type and intensity), optimal configuration of receivers, and orientation of receiver lines with respect to geological features. This ensures that the highest signal-t</p> Signup and view all the answers

What is an aerated layer?

<p>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 aerated layer typically has a low seismic velocity.</p> Signup and view all the answers

What is an aeromagnetic survey?

<p>Measurements of the Earth's magnetic field gathered from aircraft. Magnetometers towed by an airplane or helicopter can measure the intensity of the Earth's magnetic field. The differences between actual measurements and theoretical values indicate anomalies in the magnetic field, which in turn represent changes in rock type or in thickness of rock units.</p> Signup and view all the answers

What is AGC?

<p>Abbreviation for automatic gain control. A system to automatically control the gain, or the increase in the amplitude of an electrical signal from the original input to the amplified output. AGC is commonly used in seismic processing to improve visibility of late-arriving events in which attenuation or wavefront divergence has caused amplitude decay.</p> Signup and view all the answers

What is the AGC time constant?

<p>The exponential rate constant (τ) that determines how quickly the output amplitude of an electrical signal that is under automatic gain control (AGC) responds to a sudden increase or decrease in input signal amplitude. Mathematically, Af(t) = Ai(t) + ΔAi (1 − e−t/τ) , where Af is the output signal amplitude, Ai is the input signal amplitude (Ai), ΔAi is the change in input signal amplitude and t is time. When t equals τ, the function (1 − e−t/τ) equals (1 − 1/e) equals 0.63. Therefore, the AGC time constant (τ) is the amount of time that elapses for the output signal of AGC to reflect 63% of the change in the input signal amplitude.</p> Signup and view all the answers

What is an air gun?

<p>A source of seismic energy used in acquisition of marine seismic data. This gun releases highly compressed air into water. Air guns are also used in water-filled pits on land as an energy source during acquisition of vertical seismic profiles.</p> Signup and view all the answers

What is air shooting?

<p>A method of seismic acquisition using charges detonated in the air or on poles above the ground as the source. Air shooting is also called the Poulter method after American geophysicist Thomas Poulter.</p> Signup and view all the answers

What is an alias filter?

<p>A filter, or a set of limits used to eliminate unwanted portions of the spectra of the seismic data, to remove frequencies that might cause aliasing during the process of sampling an analog signal during acquisition or when the sample rate of digital data is being decreased during seismic processing.</p> Signup and view all the answers

Explain aliasing.

<p>The distortion of frequency introduced by inadequately sampling a signal, which results in ambiguity between signal and noise. Aliasing can be avoided by sampling at least twice the highest frequency of the waveform or by filtering frequencies above the Nyquist frequency, the highest frequency that can be defined accurately by that sampling interval.</p> Signup and view all the answers

What is amplitude?

<p>The difference between the maximum displacement of a wave and the point of no displacement, or the null point. The common symbol for amplitude is a.</p> Signup and view all the answers

What is an amplitude anomaly/bright spot?

<p>An abrupt increase in seismic amplitude that can indicate the presence of hydrocarbons, although such anomalies can also result from processing problems, geometric or velocity focusing or changes in lithology. Amplitude anomalies that indicate the presence of hydrocarbons can result from sudden changes in acoustic impedance, such as when a gas sand underlies a shale, and in that case, the term is used synonymously with hydrocarbon indicator.</p> Signup and view all the answers

What is amplitude distortion?

<p>A change in the amplitude of a waveform that is generally undesirable, such as in seismic waves.</p> Signup and view all the answers

What is amplitude variation with offset and azimuth / AVOAZ?

<p>The azimuthal variation of the AVO response.</p> Signup and view all the answers

What is amplitude variation with offset/ AVO?

<p>Variation in seismic reflection amplitude with change in distance between shotpoint and receiver that indicates differences in lithology and fluid content in rocks above and below the reflector. AVO analysis is a technique by which geophysicists attempt to determine thickness, porosity, density, velocity, lithology and fluid content of rocks. Successful AVO analysis requires special processing of seismic data and seismic modeling to determine rock properties with a known fluid content. With that knowledge, it is possible to model other types of fluid content. A gas-filled sandstone might show increasing amplitude with offset, whereas a coal might show decreasing amplitude with offset. A limitation of AVO analysis using only P-energy is its failure to yield a unique solution, so AVO results are prone to misinterpretation. One common misinterpretation is the failure to distinguish a gas-filled reservoir from a reservoi</p> Signup and view all the answers

Explain the angle of approach.

<p>The acute angle at which a wavefront impinges upon an interface, such as a seismic wave impinging upon strata. Normal incidence is the case in which the angle of incidence is zero, the wavefront is parallel to the surface and its raypath is perpendicular, or normal, to the interface. Snell's law describes the relationship between the angle of incidence and the angle of refraction of a wave.</p> Signup and view all the answers

What is the angle of incidence?

<p>The acute angle at which a raypath impinges upon a line normal to an interface, such as a seismic wave impinging upon strata. Normal incidence is the case in which the angle of incidence is zero, the wavefront is parallel to the surface and its raypath is perpendicular, or normal, to the interface. Snell's law describes the relationship between the angle of incidence and the angle of refraction of a wave.</p> Signup and view all the answers

What is angular dispersion / seismic velocity?

<p>The variation of seismic velocity in different directions.</p> Signup and view all the answers

What does it mean for a substance to be anisotropic?

<p>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. Often found where platy minerals such as micas and clays align parallel to depositional bedding as sediments are compacted, anisotropy is common in shales.</p> Signup and view all the answers

What is anisotropy/ aeolotropy?

<p>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.</p> Signup and view all the answers

What is an aperture/ window?

<p>A portion of a data set, such as seismic data, to which functions or filters are applied. Aperture time, for example, can be specified, such as a window from 1.2 to 2.8 seconds.</p> Signup and view all the answers

Explain what 'aperture/ window' means.

<p>A mechanism to limit the affects of measurements on a device or system. In seismic data acquisition, the length of the spread has the effect of an aperture.</p> Signup and view all the answers

What is apparent anisotropy?

<p>In seismic data, the ratio of the velocity determined from normal moveout (i.e., primarily a horizontal measurement) to velocity measured vertically in a vertical seismic profile or similar survey. Apparent anisotropy is of particular importance when migrating long-offset seismic data and analyzing AVO data accurately. The normal moveout velocity involves the horizontal component of the velocity field, which affects sources and receivers that are offset, but the horizontal velocity field is not involved in velocity calculations from vertically measured time-depth pairs.</p> Signup and view all the answers

What is apparent velocity?

<p>In geophysics, the velocity of a wavefront in a certain direction, typically measured along a line of receivers and symbolized by va. Apparent velocity and velocity are related by the cosine of the angle at which the wavefront approaches the receivers: va = v cos θ, whereva = apparent velocityv = velocity of wavefrontθ = angle at which a wavefront approaches the geophone array.</p> Signup and view all the answers

What is apparent wavelength?

<p>The wavelength measured by receivers when a wave approaches at an angle. The relationship between true and apparent wavelength can be shown mathematically as follows: λ = λa sin θ, whereλ = wavelengthλa = apparent wavelengthθ = angle at which a wavefront approaches the geophone array.</p> Signup and view all the answers

What is the applied-potential method?

<p>A technique to map a potential field generated by stationary electrodes by moving an electrode around the survey area.</p> Signup and view all the answers

Describe the arrangement of seismic sources or receivers that are recorded by one channel.

<p>A geometrical arrangement of seismic sources (a source array, with each individual source being activated in some fixed sequence in time) or receivers (a hydrophone or geophone array) that is recorded by one channel.</p> Signup and view all the answers

Describe the arrangement of electrodes or antennas used for resistivity, etc.

<p>An arrangement or configuration of electrodes or antennas used for resistivity, induced polarization (IP), or other types of electromagnetic surveying. Resistivity arrays typically consist of two current electrodes and two potential electrodes and are distinguished by the relative separations between the electrodes. Examples are the dipole-dipole, Schlumberger and Wenner arrays.</p> Signup and view all the answers

What is an Array/ Nest?

<p>Generally, a geometrical configuration of transducers (sources or receivers) used to generate or record a physical field, such as an acoustic or electromagnetic wavefield or the Earth's gravity field.</p> Signup and view all the answers

What does 'arrival time' refer to?

<p>The elapsed time between the release of seismic energy from a source and its arrival at the receiver.</p> Signup and view all the answers

Define attenuate/ attenuation.

<p>The removal of undesirable features, such as multiple events, from seismic data.</p> Signup and view all the answers

What is attenuation?

<p>The loss of energy or amplitude of waves as they pass through media. Seismic waves lose energy through absorption, reflection and refraction at interfaces, mode conversion and spherical divergence, or spreading of the wave.</p> Signup and view all the answers

Explain what is meant by 'attenuation/ attenuate'.

<p>The reduction in amplitude of an electromagnetic wave passing through the formation, usually measured in decibels/meter, dB/m. The term is used in particular with reference to the propagation resistivity log and the electromagnetic propagation log.</p> Signup and view all the answers

What is an attribute?

<p>A measurable property of seismic data, such as amplitude, dip, frequency, phase and polarity. Attributes can be measured at one instant in time or over a time window, and may be measured on a single trace, on a set of traces or on a surface interpreted from seismic data. Attribute analysis includes assessment of various reservoir parameters, including ahydrocarbon indicator, by techniques such as amplitude variation with offset (AVO) analysis.</p> Signup and view all the answers

What is autocorrelation?

<p>The comparison of a waveform to itself. Autocorrelation is useful in the identification of multiples or other regularly repeating signals, and in designing deconvolution filters to suppress them.</p> Signup and view all the answers

What is automatic gain control?

<p>A system to control the gain, or the increase in the amplitude of an electrical signal from the original input to the amplified output, automatically. AGC is commonly used in seismic processing to improve visibility of late-arriving events in which attenuation or wavefront divergence has caused amplitude decay.</p> Signup and view all the answers

What is autotrack?

<p>To use computer software to pick a particular reflection or attribute in seismic data automatically. Autotracking can speed interpretation of three-dimensional seismic data, but must be checked for errors.</p> Signup and view all the answers

What is a group of 2D seismic lines acquired individually called?

<p>2D seismic data.</p> Signup and view all the answers

What are abnormal events?

<p>A term to indicate features in seismic data other than reflections, including events such as diffractions, multiples, refractions and surface waves.</p> Signup and view all the answers

What is absorption (in the context of energy)?

<p>The conversion of one form of energy into another as the energy passes through a medium.</p> Signup and view all the answers

What does acoustic pertain to?

<p>Sound.</p> Signup and view all the answers

In geophysics, what does acoustic refer to?

<p>Specifically to P-waves in the absence of S-waves (i.e., in fluids, which do not support S-waves, or in cases in which S-waves in solids are ignored).</p> Signup and view all the answers

What was an acoustic coupler?

<p>An obsolete piece of equipment that converts acoustic signals from analog to electrical form and back.</p> Signup and view all the answers

What is measured in an acoustic log?

<p>A record of some acoustic property of the formation or borehole.</p> Signup and view all the answers

What is acoustic positioning?

<p>A method of calculating the position of marine seismic equipment. Range measurements are made whereby distance is equal to acoustic signal traveltime from transmitter to hydrophone multiplied by the speed of sound in water.</p> Signup and view all the answers

What is acoustic traveltime?

<p>The duration of the passage of a signal from the source through the Earth and back to the receiver.</p> Signup and view all the answers

What is acoustic velocity?

<p>The rate at which a sound wave travels through a medium. Unlike the physicist's definition of velocity as a vector, its usage in geophysics is as a property of a medium: distance divided by traveltime.</p> Signup and view all the answers

What is an acoustic velocity log?

<p>A display of traveltime of acoustic waves versus depth in a well.</p> Signup and view all the answers

What does acquisition involve?

<p>The generation and recording of seismic data. Acquisition involves many different receiver configurations, including laying geophones or seismometers on the surface of the Earth or seafloor, towing hydrophones behind a marine seismic vessel, suspending hydrophones vertically in the sea or placing geophones in a wellbore (as in a vertical seismic profile) to record the seismic signal.</p> Signup and view all the answers

What is aliasing?

<p>The distortion of frequency introduced by inadequately sampling a signal, which results in ambiguity between signal and noise.</p> Signup and view all the answers

What is an amplitude anomaly?

<p>An abrupt increase in seismic amplitude that can indicate the presence of hydrocarbons, although such anomalies can also result from processing problems, geometric or velocity focusing or changes in lithology.</p> Signup and view all the answers

What is amplitude variation with offset and azimuth?

<p>The azimuthal variation of the AVO response.</p> Signup and view all the answers

What is the angle of approach?

<p>The acute angle at which a wavefront impinges upon an interface, such as a seismic wave impinging upon strata.</p> Signup and view all the answers

What is angular dispersion?

<p>The variation of seismic velocity in different directions.</p> Signup and view all the answers

What does it mean to be anisotropic?

<p>Having directionally dependent properties.</p> Signup and view all the answers

Define anisotropy.

<p>Predictable variation of a property of a material with the direction in which it is measured, which can occur at all scales.</p> Signup and view all the answers

What is an aperture (in seismic data acquisition)?

<p>A mechanism to limit the affects of measurements on a device or system.</p> Signup and view all the answers

What is an array (in computing)?

<p>In computing, code written to access data in more than one dimension according to a name and subscripts that correspond to each dimension.</p> Signup and view all the answers

What is an array (in seismic context)?

<p>A geometrical arrangement of seismic sources (a source array, with each individual source being activated in some fixed sequence in time) or receivers (a hydrophone or geophone array) that is recorded by one channel.</p> Signup and view all the answers

What is an array (in electrical or electromagnetic surveying)?

<p>An arrangement or configuration of electrodes or antennas used for resistivity, induced polarization (IP), or other types of electromagnetic surveying.</p> Signup and view all the answers

What is an array (general definition)?

<p>Generally, a geometrical configuration of transducers (sources or receivers) used to generate or record a physical field, such as an acoustic or electromagnetic wavefield or the Earth's gravity field.</p> Signup and view all the answers

What is arrival time?

<p>The elapsed time between the release of seismic energy from a source and its arrival at the receiver.</p> Signup and view all the answers

What does attenuate mean?

<p>The removal of undesirable features, such as multiple events, from seismic data.</p> Signup and view all the answers

What is attenuation (in electromagnetic waves passing through formation)?

<p>The reduction in amplitude of an electromagnetic wave passing through the formation, usually measured in decibels/meter, dB/m.</p> Signup and view all the answers

What is average velocity?

<p>In geophysics, the depth divided by the traveltime of a wave to that depth.</p> Signup and view all the answers

What is an axis of rotational symmetry?

<p>An axis of rotational invariance. A material whose properties exhibit cylindrical, or invariant rotational, symmetry may be rotated about this axis by any amount and its properties will be indistinguishable from what they were before the rotation.</p> Signup and view all the answers

What is back propagation?

<p>A method for reconstructing the location and shape of the wave at an earlier time using the wave equation.</p> Signup and view all the answers

What is back stripping method?

<p>A modeling technique to assess the geologic history of rock layers through the use of geologic cross sections or seismic sections.</p> Signup and view all the answers

What is backscatter?

<p>A reflection phenomenon of energy in which a nonreflective surface, which is a surface that does not reflect energy coherently, randomly scatters energy.</p> Signup and view all the answers

What is a band-limited function?

<p>A function or time series whose Fourier transform is restricted to a finite range of frequencies or wavelengths.</p> Signup and view all the answers

What does band-pass mean?

<p>Frequencies within the acceptable limits of a filter.</p> Signup and view all the answers

What does band-reject mean?

<p>Frequencies beyond the limits of a filter.</p> Signup and view all the answers

What is the base of weathering?

<p>The lower boundary of the near-surface, low-velocity zone in which rocks are physically, chemically or biologically broken down, in some cases coincident with a water table.</p> Signup and view all the answers

What is a base station?

<p>A reference location for a survey, or a survey point whose measured values of a given parameter of interest are understood and can be used to normalize other survey points.</p> Signup and view all the answers

What is a basic wavelet?

<p>The shape of a wavelet produced by reflection of an actual wave train at one interface with a positive reflection coefficient.</p> Signup and view all the answers

What is the Beaufort scale?

<p>The 0 to 12 scale for measurement of wind strength according to its effect on objects such as trees, flags and water established by Admiral Francis Beaufort (1774 to 1857).</p> Signup and view all the answers

Flashcards

Single Seismic Trace

A single seismic trace represents 1-D seismic data.

Check-Shot Survey

A check-shot survey of a well, used to correct sonic logs and generate synthetic seismograms.

Vertical Seismic Section

A vertical section of seismic data consisting of numerous adjacent traces acquired sequentially.

2D Seismic Data

Seismic data or lines acquired individually with significant gaps between them.

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3C Seismic Data

Data acquired using three orthogonally oriented geophones or accelerometers to determine wave type and direction.

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3D Seismic Data

Closely spaced seismic lines that provide a highly spatially sampled measure of subsurface reflectivity.

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4C Seismic Data

Seismic data acquired using three geophones and a hydrophone to measure compressional and shear waves.

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4D Seismic Data

3D seismic data acquired at different times to assess changes in a producing reservoir.

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Abnormal Events

Seismic data features other than reflections, such as diffractions, multiples, and surface waves.

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Absorption Band

The range of wavelengths of energy that can be absorbed by a given substance.

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Absorptance

The ratio of absorbed incident energy to the total energy to which a body is exposed.

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Absorption

Conversion of energy as it passes through a medium, like seismic waves converting to heat.

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Accelerometer

A device to measure acceleration of ships, aircraft, or ground acceleration from acoustic vibrations.

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Acoustic

Pertaining to sound or vibrational events, generally describes P-waves in the absence of S-waves.

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Acoustic Impedance

The product of density and seismic velocity.

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Acoustic Impedance Section

A seismic reflectivity section inverted for acoustic impedance, calibrated with well logs.

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Acoustic Log

A display of traveltime of acoustic waves versus depth in a well.

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Acoustic Positioning

Determining the position of marine seismic equipment by measuring acoustic signal traveltime.

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Acoustic Transparency

A medium with constant acoustic impedance, containing no seismic reflections.

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Acoustic Traveltime

The duration of a signal from the source through the Earth and back to the receiver.

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Acoustic Velocity

The rate at which a sound wave travels through a medium.

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Acoustic Wave

An elastic wave in which particles oscillate in the direction the wave propagates.

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Acquisition

The generation and recording of seismic data.

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Aerated Layer

A near-surface sedimentary layer subject to weathering with air-filled pores and low seismic velocity.

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Aeromagnetic Survey

Measurements of the Earth's magnetic field gathered from aircraft.

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AGC

A system to automatically control the gain of an electrical signal, improving visibility of late-arriving events.

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Air Gun

A marine seismic energy source that releases compressed air into water.

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Air Shooting

A seismic acquisition method using charges detonated in the air as the source.

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Air Wave

A type of coherent noise, a sound wave that travels through the air during seismic surveying.

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Alias Filter

A filter used to eliminate unwanted portions of the spectra of seismic data.

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Aliasing

The distortion of frequency that results if a signal is sampled inadequately.

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Amplitude

The difference between the maximum displacement of a wave and the point of no displacement.

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Amplitude Anomaly

An abrupt increase in seismic amplitude that can indicate the presence of hydrocarbons.

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Amplitude Variation with Offset/ AVO

Variation in seismic reflection amplitude with distance between shot and receiver.

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Angle of Incidence

The acute angle at which a wavefront impinges upon an interface.

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Anisotropic

Having directionally dependent properties.

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Antialias Filter

To remove frequencies that might cause aliasing when sampling an analog signal

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Aperture

A selection of data to which a filter or function is applied.

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Apparent Anisotropy

Ratio of horizontal to vertical seismic velocity

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Apparent Velocity

Velocity of a wavefront in a certain direction measured along a line of receivers.

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Applied potential Method

A method to map a potential field by moving an electrode around the survey area

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Array

A geometrical arrangement of seismic sources (a source array or receivers.

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Arrival Time

The elapsed time between the release of seismic energy from a source and its arrival at the receiver

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Attenuate

The removal of undesirable features, such as multiple events, from seismic data.

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Attenuation

The loss of energy or amplitude of waves as they pass through media.

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Attribute

A measurable property of seismic data, such as amplitude, dip, frequency, phase and polarity

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Autocorrelation

A filter, or a set of limits used to eliminate unwanted portions of the spectra of the seismic data

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Autotrack

To use computer software to pick a particular reflection or attribute in seismic data automatically.

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Average Velocity

In geophysics, the depth divided by the traveltime of a wave to that depth.

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Axis of Rotational Symmetry

An axis of rotational invariance.

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Study Notes

  • A single seismic trace is considered 1D seismic data.
  • A check-shot survey of a well helps correct the sonic log and create a synthetic seismogram that reveals amplitude changes versus traveltime and is considered 1D seismic data.
  • A vertical section of seismic data with adjacent, sequentially acquired traces is considered 2D seismic data.
  • A set of 2D seismic lines obtained separately, unlike the closely spaced lines in 3D seismic data, is considered 2D seismic data.
  • A 2D survey contains widely spaced lines orthogonal to geological strike and minimal lines parallel for data tying and structural mapping.
  • 3C seismic data uses three orthogonal geophones or accelerometers in land, marine, or borehole settings, measuring wave type and propagation direction.
  • 4C seismic data requires a hydrophone, but 3C is suitable when a hydrophone adds no value, like on land.
  • 3D seismic data is acquired with closely spaced receiver and shot lines for high spatial sampling of subsurface reflectivity, with line spacing from 300 m to over 600 m.
  • 3D seismic data has shotpoint and receiver group distances of about 25 m internationally and 34 to 67 m onshore USA.
  • 3D seismic data bin sizes are commonly 25 m, 110 ft, or 220 ft.
  • In 3D seismic data, original seismic lines are in-lines, with perpendicular lines displayed as crosslines, allowing accurate subsurface maps.
  • A 3D survey involves closely spaced receiver and shot lines with no significant subsurface coverage gaps.
  • 4C seismic data uses three geophones and a hydrophone in ocean-bottom sensors to measure shear (S) and compressional (P) waves.
  • 4D seismic data involves acquiring 3D seismic data at different times over the same area to monitor reservoir changes, acquired on the surface or in a borehole.
  • Abnormal events refer to non-reflection features in seismic data like diffractions, multiples, refractions, and surface waves.
  • Absorption band is the range of energy wavelengths a substance can absorb.
  • Absorbing boundary conditions are algorithms used in numerical simulation to absorb energy at computational domain boundaries, suppressing reflections.
  • Absorptance is the ratio of absorbed incident energy to the total energy a body is exposed to.
  • Absorption is when liquids or solids soak up water or other fluids; natural gas dehydration uses glycols to absorb water vapor.
  • Absorption is the conversion of energy from one form to another as it passes through a medium, like seismic waves converting to heat in rock.
  • An accelerometer measures acceleration of a ship, aircraft, or ground acceleration from acoustic vibrations.
  • Acoustic generally describes sound or vibrational events, regardless of frequency, while sonic is limited to frequencies from 1 to 25 kHz.
  • In geophysics, acoustic refers to P-waves in the absence of S-waves.
  • An acoustic coupler is an obsolete device that converts acoustic signals from analog to electrical form and back, used with early modems.
  • Acoustic emission is a type of elastic wave produced by deformation or brittle failure, characterized by high frequency.
  • Acoustic impedance is the product of density and seismic velocity that varies among rock layers (Z), influencing the reflection coefficient.
  • An acoustic impedance section is a seismic reflectivity section inverted for acoustic impedance, calibrated with sonic and density logs.
  • An acoustic log displays traveltime of acoustic waves versus depth in a well; it's often a synonym for a sonic log, while some display velocity.
  • An acoustic log records acoustic properties of the formation or borehole, also refers to compressional slowness, as well as shear, flexural and Stoneley slownesses or amplitudes.
  • Acoustic positioning calculates the position of marine seismic equipment using acoustic signal traveltime and the speed of sound in water with trilateration.
  • Acoustic transparency is the quality of a medium with constant acoustic impedance, containing no seismic reflections, like water.
  • Acoustic traveltime is the duration of a signal's passage from source through the Earth and back to the receiver; time seismic sections show two-way traveltime.
  • Acoustic velocity is the rate at which a sound wave travels through a medium.
  • Acoustic velocity can be determined from laboratory measurements, acoustic logs, vertical seismic profiles, or velocity analysis of seismic data.
  • Acoustic velocity, in anisotropic media such as rocks, increase with depth due to compaction reducing porosity and can vary vertically, laterally, and azimuthally.
  • Acoustic velocity varies based on how it's derived from data; stacking velocity differs from average velocity.
  • An acoustic wave/dilatational wave is an elastic body wave in which particles oscillate in the direction the wave propagates (P-waves).
  • Acquisition involves the generation and recording of seismic data using various receiver configurations and sources, optimized for local conditions.
  • An aerated layer is unconsolidated, weathered sedimentary layer with air-filled pores, typically having low seismic velocity.
  • Aeromagnetic surveys gather measurements of the Earth's magnetic field from aircraft to indicate anomalies.
  • AGC (automatic gain control) automatically controls the gain to improve visibility of late-arriving events with amplitude decay.
  • AGC time constant (Ï„) determines how quickly output amplitude responds to changes in input signal amplitude; it's the time for the output signal to reflect 63% of the change.
  • An air gun is a marine seismic energy source that releases compressed air into water, also used in water-filled pits on land.
  • Air shooting (Poulter method) is a seismic acquisition method using charges detonated in the air or on poles above the ground as the source.
  • An air wave is a sound wave that travels through the air at approximately 330 m/s and can be generated and recorded during seismic surveying.
  • An alias filter eliminates unwanted portions of seismic data spectra to prevent aliasing while sampling an analog signal or decreasing the sample rate of digital data.
  • Aliasing is frequency distortion from inadequately sampling a signal, avoided by sampling at least twice the highest frequency or filtering frequencies above the Nyquist frequency.
  • Amplitude is the difference between the maximum displacement of a wave and the point of no displacement.
  • An amplitude anomaly/bright spot is an abrupt increase in seismic amplitude that can indicate hydrocarbons, processing problems, focusing, or lithology changes.
  • Amplitude distortion is a change in the amplitude of a waveform, generally undesirable, such as in seismic waves.
  • Amplitude distortion is the inability of a system to exactly match input and output amplitude.
  • Amplitude variation with offset and azimuth/AVOAZ is the azimuthal variation of the AVO response.
  • Amplitude variation with offset/AVO helps determine lithology and fluid content of rocks by analyzing changes in seismic reflection amplitude with distance between shotpoint and receiver.
  • AVO analysis involves seismic data processing and modeling to determine rock properties with known fluid content, limitations include failure to yield a unique solution.
  • Angle of approach is the acute angle at which a wavefront impinges upon an interface.
  • Angle of incidence is the acute angle at which a raypath impinges upon a line normal to an interface.
  • Angular dispersion/seismic velocity is the variation of seismic velocity in different directions.
  • Anisotropic materials have directionally dependent properties like seismic velocity variation in rocks, and is common in shales.
  • Anisotropy/aeolotropy is the predictable variation of a material's property with measurement direction, which can occur at all scales.
  • An antialias filter eliminates unwanted portions of seismic data spectra to prevent aliasing while sampling an analog signal or decreasing the sample rate of digital data.
  • Aperture/window refers to a portion of a data set, such as seismic data, to which functions or filters are applied.
  • Aperture/window is a mechanism to limit the affects of measurements on a device or system.
  • Apparent anisotropy is the ratio of velocity determined from normal moveout to velocity measured vertically in a vertical seismic profile.
  • Apparent velocity is the velocity of a wavefront in a certain direction.
  • Apparent wavelength is the wavelength measured by receivers when a wave approaches at an angle.
  • The applied-potential method is a technique to map a potential field generated by stationary electrodes by moving an electrode around the survey area.
  • Array refers to: code written to access data in more than one dimension according to a name and subscripts that correspond to each dimension, a geometrical arrangement of seismic sources, and an arrangement of electrodes or antennas used for resistivity.
  • Array/nest generally refers to a geometrical configuration of transducers used to generate or record a physical field, such as acoustic or electromagnetic.
  • Arrival time is the elapsed time between seismic energy release and its arrival at the receiver.
  • Attenuate/attenuation is the removal of undesirable features, such as multiple events, from seismic data, as well as the loss of energy or amplitude of waves as they pass through media.
  • Attenuation/attenuate is the reduction in amplitude of an electromagnetic wave passing through the formation, usually measured in decibels/meter, dB/m.
  • Attribute is a measurable property of seismic data (amplitude, dip, frequency, phase, and polarity) that can be measured at one instant in time or over a time window.
  • Autocorrelation is the comparison of a waveform to itself, useful for identifying multiples or repeating signals and designing deconvolution filters.
  • Automatic gain control automatically controls the gain to improve visibility of late-arriving events with amplitude decay.
  • Autotrack/autotracking is to use computer software to pick a particular reflection or attribute in seismic data automatically.
  • AVA is short for amplitude variation with angle of incidence.
  • AVAZ is short for amplitude variation with azimuth.
  • Average velocity is depth divided by the traveltime of a wave to that depth.
  • AVO (amplitude variation with offset) helps determine lithology and fluid content of rocks by analyzing changes in seismic reflection amplitude with distance between shotpoint and receiver.
  • AVOAZ/amplitude variation with offset and azimuth is the azimuthal variation of the AVO response.
  • Axis of rotational symmetry is an axis of rotational invariance of a material that exhibits cylindrical, or invariant rotational, symmetry.
  • Back propagation is a method for reconstructing the location and shape of the wave at an earlier time using the wave equation.
  • Back stripping is a modeling technique to assess the geologic history of rock layers through the use of geologic cross sections or seismic sections.
  • Backscatter is a reflection phenomenon of energy in which a nonreflective surface, which is a surface that does not reflect energy coherently, randomly scatters energy.
  • Band is a range of frequencies or wavelengths, i.e. audible frequencies of sound and visible wavelengths of light.
  • A band-limited function is a function or time series whose Fourier transform is restricted to a finite range of frequencies or wavelengths.
  • Band-pass refers to frequencies within the acceptable limits of a filter.
  • Band-reject are frequencies beyond the limits of a filter.
  • Base of weathering is the lower boundary of the near-surface, low-velocity zone where rocks are broken down, and is used for static corrections to seismic data.
  • Base station is a reference location for a survey, or a survey point whose measured values of a given parameter of interest are understood and can be used to normalize other survey points.
  • Baseline is a line joining base stations whose transmissions are synchronized during surveying.
  • Baseline is a reference line, such as a "shale baseline," a line representing the typical value of a given measurement for a shale on a well log, or the zero-amplitude line of a seismic trace.
  • Baseline is the original survey of a set of surveys covering the same area but acquired over a period of time.
  • Basic wavelet/embedded wavelet is the shape of a wavelet produced by reflection of an actual wave train at one interface with a positive reflection coefficient.
  • Beaufort scale is the 0 to 12 scale for measurement of wind strength according to its effect on objects such as trees, flags and water established by Admiral Francis Beaufort (1774 to 1857).
  • Bel is the unit of measurement to describe or compare the intensity of acoustic or electrical signal, named for American inventor Alexander Graham Bell (1847 to 1922).
  • Benchmark/BM is a permanently fixed marker cited in surveying, such as a concrete block or steel plate, with an inscription of location and elevation, but also more generally a standard against which the performance of processes are measured.
  • Bias is an adjustment of the relative positive and negative excursions of reflections during seismic processing by bulk shifting the null point, or baseline, of the data to emphasize peaks at the expense of troughs or vice versa.
  • Bin is to sort seismic data into small areas according to the midpoint between the source and the receiver, reflection point or conversion point prior to stacking and a subdivision of a seismic survey.
  • Bird is a device containing a magnetometer and possibly other instruments that can be towed by an aircraft during aeromagnetic surveying or in a marine seismic streamer to provide dynamic information about the streamer position.

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