Seismic range equation

Geophysics ◽  
1991 ◽  
Vol 56 (7) ◽  
pp. 1015-1026 ◽  
Author(s):  
Richard E. Duren
Keyword(s):  
Seismic Data ◽  
Amplitude Spectrum ◽  
Data Gathering ◽  
P Wave ◽  
Target Strength ◽  
Load Impedance ◽  
Transmission Coefficients ◽  
Amplitude Versus Offset ◽  
Well Data ◽  
Range Equation

The seismic range equation is the seismic equivalent to the radar range equation. It unites the relevant factors in a marine data gathering system (source, subsurface, target, and receiving system) into a single formulation and provides a systematic approach to seismic data analysis, which we have used to improve seismic data processing for marine basins around the world. While most of the concepts contained in the seismic range equation are well known, this is the first time all have been put together, described in such detail, and used effectively (by way of modeling) to improve processing. A wavelet’s amplitude spectrum can be calculated using the seismic range equation, and its phase spectrum can be calculated by considering the phase contributions from source to receiver. An amplitude‐versus‐offset (AVO) example supports our approach. Source array geometry and the outgoing waveforms from the array elements are required. The receiving system’s load impedance and the hydrophone array’s geometry, sensitivity, and impedance are also required. Subsurface factors and target strength can be determined by assuming a horizontally layered subsurface and ray theory. The required layer thicknesses, P‐wave velocities, and densities can be generated by hand, statistically, or from well data. Well data are not required at the location of interest. The Zoeppritz equations furnish all P-wave reflection and transmission coefficients along a raypath. Seismic data at the location of interest can be used to estimate an attenuation constant (effective Q).

The Paleozoic prospectivity of the Browse Basin, Australia

2020 ◽  
Vol 60 (2) ◽  
pp. 685
Author(s):  
Said Amiribesheli ◽  
Joshua Thorp ◽  
Julia Davies
Keyword(s):  
Seismic Data ◽  
Inversion Algorithm ◽  
Reservoir Properties ◽  
Depth Migration ◽  
Canning Basin ◽  
Petroleum Systems ◽  
Amplitude Versus Offset ◽  
Long Offset ◽  
Well Data

Most of the discovered hydrocarbons in the Browse Basin occurred within the Mesozoic intervals, while deeper Paleozoic sequences have been seldom explored. Lack of Paleozoic exploration in the Browse Basin has been attributed to the lack of well penetrations, poor understanding of the petroleum systems and paucity of seismic data. The onshore Canning Basin with several commercial fields and discoveries is the most appropriate analogue for understanding the Paleozoic sequences in the region. With the integration of geophysical data (i.e. gravity, magnetic and seismic), well data and geology, the Paleozoic prospectivity of the Browse Basin can be further enlightened. Modern long offset (8 m) Vampire 2D seismic data were acquired by Searcher to address some of the complex challenges in the Browse Basin. Reservoir quality of the Brewster Formation, volcanic discrimination within the Plover Formation and identification of deeper Triassic and Paleozoic plays are some examples of these challenges in the Browse Basin. Recently Searcher reprocessed this regionally important Vampire 2D seismic dataset that ties to 60 wells. The broadband pre-stack depth migration reprocessed data were inverted to extract three petro-elastic properties of acoustic impedance, Vp/Vs and density by three-term amplitude versus offset inversion algorithm to improve imaging of deeper plays and delineate reservoir properties. This paper discusses how several potential Paleozoic reservoir-seal pairs can be identified in the Browse Basin by utilising the integration of Vampire 2D seismic data, quantitative interpretation products, regional geology and knowledge of the Canning Basin’s fields and discoveries. Previously there was little exploration of Paleozoic plays because they could not be imaged on seismic data. The potential Paleozoic reservoirs identified in this study include Permo-Carboniferous subcrop, Carboniferous-Devonian anticline and Carboniferous-Devonian rollover plays.

An amplitude-based multiazimuthal approach to mapping fractures using P-wave 3D seismic data

Geophysics ◽  
2004 ◽  
Vol 69 (3) ◽  
pp. 690-698 ◽  
Author(s):  
Mu Luo ◽  
Brian J. Evans
Keyword(s):  
Physical Model ◽  
Seismic Data ◽  
Single Layer ◽  
P Wave ◽  
Data Sets ◽  
Test Results ◽  
Amplitude Versus Offset ◽  
Sorting Process ◽  
Seismic Reflections ◽  
3D Seismic Data

We have tested an amplitude-based multiazimuthal approach for mapping fractures which requires only a simple azimuth-offset sorting process. By displaying the amplitudes of all traces collected within a superbin, the method predicts fractures by mapping P-wave amplitude variations, in which a lineation within the map indicates the presence and the orientation of fractures within the superbin. Test results using physical model and field data sets suggest that the amplitude-based multiazimuthal approach could help to determine the presence of multiple fracture sets in a single layer, which may be expressed through subtle variations in P-wave multiazimuthal seismic reflections. Our experiments with a physical model containing manmade vertical fractures suggest that transmission effects could be one of the dominant factors which control azimuthal amplitude versus offset (AVO) behavior. The technique described in this paper can operate on any 3D P-wave seismic data with wide azimuth and offset distributions.

On the Forward Simulation of the Geophysical Characteristics in Fractured Reservoirs

2012 ◽  
Vol 524-527 ◽  
pp. 152-159
Author(s):  
Xiong Ju Xie ◽  
Xun Lian Wang ◽  
Yuan Feng Cheng
Keyword(s):  
Seismic Data ◽  
Fractured Reservoirs ◽  
Data Gathering ◽  
P Wave ◽  
Forward Simulation ◽  
Economic Methods ◽  
Seismic Property ◽  
Fracture Distribution ◽  
The Relationship ◽  
Made In

Anisotropic information of pre-stack 3D azimuth P wave from seismic data is already one of the most efficient and economic methods from reservoir fracture examination, which requires a wide azimuth for seismic data gathering. By forward simulation of the geophysical characteristics in fractured reservoirs, the relationship between azimuth distribution areas of seismic data gathering and fracture direction is studied. Narrow azimuth for seismic data gathering is also somewhat effective to describe fracture distribution characteristics. In addition, significant seismic property difference (amplitude, damping and frequency) can be made in fractured reservoirs, thus, fracture can be effectively examined by the seismic information of different offsets. All the results in the paper get excellent practical application.

scholarly journals Three-component amplitude versus offset analysis

1989 ◽  
Vol 20 (2) ◽  
pp. 257
Author(s):  
D.R. Miles ◽  
G. Gassaway ◽  
L. Bennett ◽  
R. Brown
Keyword(s):  
Seismic Data ◽  
P Wave ◽  
S Wave ◽  
Converted Wave ◽  
P Waves ◽  
S Waves ◽  
Avo Analysis ◽  
Avo Inversion ◽  
Amplitude Versus Offset ◽  
Converted Waves

Three-component (3-C) amplitude versus offset (AVO) inversion is the AVO analysis of the three major energies in the seismic data, P-waves, S-waves and converted waves. For each type of energy the reflection coefficients at the boundary are a function of the contrast across the boundary in velocity, density and Poisson's ratio, and of the angle of incidence of the incoming wave. 3-C AVO analysis exploits these relationships to analyse the AVO changes in the P, S, and converted waves. 3-C AVO analysis is generally done on P, S, and converted wave data collected from a single source on 3-C geophones. Since most seismic sources generate both P and S-waves, it follows that most 3-C seismic data may be used in 3-C AVO inversion. Processing of the P-wave, S-wave and converted wave gathers is nearly the same as for single-component P-wave gathers. In split-spread shooting, the P-wave and S-wave energy on the radial component is one polarity on the forward shot and the opposite polarity on the back shot. Therefore to use both sides of the shot, the back shot must be rotated 180 degrees before it can be stacked with the forward shot. The amplitude of the returning energy is a function of all three components, not just the vertical or radial, so all three components must be stacked for P-waves, then for S-waves, and finally for converted waves. After the gathers are processed, reflectors are picked and the amplitudes are corrected for free-surface effects, spherical divergence and the shot and geophone array geometries. Next the P and S-wave interval velocities are calculated from the P and S-wave moveouts. Then the amplitude response of the P and S-wave reflections are analysed to give Poisson's ratio. The two solutions are then compared and adjusted until they match each other and the data. Three-component AVO inversion not only yields information about the lithologies and pore-fluids at a specific location; it also provides the interpreter with good correlations between the P-waves and the S-waves, and between the P and converted waves, thus greatly expanding the value of 3-C seismic data.

Azimuthal anisotropy analysis of P-wave seismic data and estimation of the orientation of the in situ stress fields: An example from the Rock-Springs uplift, Wyoming, USA

Geophysics ◽  
2017 ◽  
Vol 82 (2) ◽  
pp. B63-B77 ◽  
Author(s):  
Subhashis Mallick ◽  
Debraj Mukherjee ◽  
Luke Shafer ◽  
Erin Campbell-Stone
Keyword(s):  
Seismic Data ◽  
In Situ Stress ◽  
P Wave ◽  
Stress Fields ◽  
Hydraulic Fractures ◽  
Rock Springs Uplift ◽  
Naturally Fractured ◽  
Well Data ◽  
Rock Springs

Estimating the orientation and magnitude of maximum and minimum horizontal in situ stress is important for characterizing naturally fractured, unconventional, and carbon-sequestered reservoirs. For naturally fractured reservoirs, they are needed to guide directional drilling; for unconventional reservoirs, they are used for optimal placements of hydraulic fractures; and for carbon-sequestered reservoirs, they are used to avoid fracturing of overlying seal rocks. In addition, a knowledge of stress fields can be used to induce fractures within the target reservoirs and enhance additional storage for carbon-sequestration experiments. The orientation and magnitude of in situ stress can be calculated at the well locations. For locations, away from the wells, analysis of the azimuthal dependence of the amplitude-variation-with-angle gradient or azimuthal angle stacks are used to quantify anisotropy, which are then related with well data and other geologic information for stress estimation. Such azimuthal analysis requires accurate conversion of offset-domain seismic data into angles. We use isotropic prestack waveform inversion for an accurate offset-to-angle transformation along different source-to-receiver azimuths followed by azimuthal analysis. Applying our method to the real seismic data from the Rock-Springs uplift, Wyoming, USA, and relating the results to the well data, we find that our results are favorably related to the orientation of the maximum in situ horizontal stress field measured at the well location.

scholarly journals Azimuthal offset‐dependent attributes applied to fracture detection in a carbonate reservoir

Geophysics ◽  
2002 ◽  
Vol 67 (2) ◽  
pp. 355-364 ◽  
Author(s):  
Feng Shen ◽  
Jesus Sierra ◽  
Daniel R. Burns ◽  
M. Nafi Toksöz
Keyword(s):  
Seismic Data ◽  
Small Variation ◽  
Carbonate Reservoir ◽  
P Wave ◽  
Fracture Detection ◽  
Multiple Signal Classification ◽  
Fracture Orientation ◽  
Amplitude Versus Offset ◽  
Strike Direction ◽  
Amplitude Versus

Offset‐dependent attributes—amplitude versus offset (AVO) and frequency versus offset—are extracted from 2‐D P‐wave seismic data using the multiple signal classification technique. These attributes are used to detect fracture orientation in a carbonate reservoir located in the Maporal field in the Barinas basin of southwestern Venezuela. In the fracture normal direction, P‐wave reflectivity is characterized by a large increase of amplitude with offset (large positive AVO gradient) and a large decrease of frequency with offset (large negative frequency versus offset gradient). In the fracture strike direction, P‐wave reflectivity shows a scattered variation in AVO but a small variation in frequency with offset. Our results also show that the reservoir heterogeneity can lead to large variations of AVO signatures and that using azimuthal offset‐dependent frequency attributes can help lessen the ambiguity when detecting fracture orientation.

P-wave anisotropy from azimuthal AVO and velocity estimates using 3D seismic data from Saudi Arabia

Geophysics ◽  
2006 ◽  
Vol 71 (2) ◽  
pp. E7-E11 ◽  
Author(s):  
Ahmed M. Al-Marzoug ◽  
Fernando A. Neves ◽  
Jung J. Kim ◽  
Edgardo L. Nebrija
Keyword(s):  
Saudi Arabia ◽  
Seismic Data ◽  
Azimuthal Velocity ◽  
Fracture Pattern ◽  
P Wave ◽  
Velocity Analysis ◽  
Consistent Estimate ◽  
Amplitude Versus Offset ◽  
Gas Fields ◽  
East West

A horizontal well is most productive in tight reservoirs when it intersects a large number of vertical fractures, yet strata near the borehole remain mechanically stable. Azimuthal velocity analysis and P-wave amplitude versus offset (AVO) using 3D wide-azimuth prestack surface seismic data provide a remote yet detailed way to map a fracture pattern away from well control. We estimate fracture direction and relative fracture intensity from such data at two gas fields in Saudi Arabia. Our results show a small azimuthal variation in P-wave velocity (maximum 5%) and a larger variation in azimuthal AVO at the reservoir (larger than 100%). Computed fracture attributes for field 1 show a consistent east-west fracture direction. However, in field 2, fracture azimuth is variable but generally east-west and north-south, with the strongly anisotropic north-south orientation correlating with faults and areas of large structural curvature in the reservoir. In both fields, azimuthal AVO analysis shows a more consistent estimate of fracture orientation than velocity analysis. These estimates have been instrumental in planning prolific and safe horizontal wells

scholarly journals No mafic layer in 80 km thick Tibetan crust

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Gaochun Wang ◽  
Hans Thybo ◽  
Irina M. Artemieva
Keyword(s):  
Seismic Data ◽  
P Wave ◽  
Indian Plate ◽  
Low Velocity ◽  
Crustal Earthquakes ◽  
Tectonic Processes ◽  
P Wave Velocity ◽  
Juvenile Crust ◽  
Mafic Lower Crust ◽  
Thick Crust

AbstractAll models of the magmatic and plate tectonic processes that create continental crust predict the presence of a mafic lower crust. Earlier proposed crustal doubling in Tibet and the Himalayas by underthrusting of the Indian plate requires the presence of a mafic layer with high seismic P-wave velocity (Vp > 7.0 km/s) above the Moho. Our new seismic data demonstrates that some of the thickest crust on Earth in the middle Lhasa Terrane has exceptionally low velocity (Vp < 6.7 km/s) throughout the whole 80 km thick crust. Observed deep crustal earthquakes throughout the crustal column and thick lithosphere from seismic tomography imply low temperature crust. Therefore, the whole crust must consist of felsic rocks as any mafic layer would have high velocity unless the temperature of the crust were high. Our results form basis for alternative models for the formation of extremely thick juvenile crust with predominantly felsic composition in continental collision zones.

Method for use in marine seismic data gathering

1985 ◽  
Vol 78 (3) ◽  
pp. 1152-1152
Author(s):  
Helge Brandsaeter ◽  
Olav Eimstad
Keyword(s):  
Seismic Data ◽  
Data Gathering ◽  
Marine Seismic

Dense surface seismic data confirm non-double-couple source mechanisms induced by hydraulic fracturing

Geophysics ◽  
2016 ◽  
Vol 81 (6) ◽  
pp. KS207-KS217 ◽  
Author(s):  
Jeremy D. Pesicek ◽  
Konrad Cieślik ◽  
Marc-André Lambert ◽  
Pedro Carrillo ◽  
Brad Birkelo
Keyword(s):  
Hydraulic Fracturing ◽  
Seismic Data ◽  
P Wave ◽  
Source Modeling ◽  
Moment Tensors ◽  
Amplitude Data ◽  
Double Couple ◽  
Source Mechanisms ◽  
Source Models ◽  
Favorable Conditions

We have determined source mechanisms for nine high-quality microseismic events induced during hydraulic fracturing of the Montney Shale in Canada. Seismic data were recorded using a dense regularly spaced grid of sensors at the surface. The design and geometry of the survey are such that the recorded P-wave amplitudes essentially map the upper focal hemisphere, allowing the source mechanism to be interpreted directly from the data. Given the inherent difficulties of computing reliable moment tensors (MTs) from high-frequency microseismic data, the surface amplitude and polarity maps provide important additional confirmation of the source mechanisms. This is especially critical when interpreting non-shear source processes, which are notoriously susceptible to artifacts due to incomplete or inaccurate source modeling. We have found that most of the nine events contain significant non-double-couple (DC) components, as evident in the surface amplitude data and the resulting MT models. Furthermore, we found that source models that are constrained to be purely shear do not explain the data for most events. Thus, even though non-DC components of MTs can often be attributed to modeling artifacts, we argue that they are required by the data in some cases, and can be reliably computed and confidently interpreted under favorable conditions.

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