scholarly journals Application of Frequency-Dependent Traveltime Tomography to 2D Crosswell Seismic Field Data

2017 ◽  
Vol 22 (4) ◽  
pp. 421-426 ◽  
Author(s):  
Jianping Liao ◽  
Zhenwei Guo ◽  
Hexiu Liu ◽  
Shixin Dai ◽  
Yanlin Zhao ◽  
...  
Keyword(s):  
High Resolution ◽  
Field Data ◽  
Seismic Waves ◽  
Velocity Model ◽  
Oil Field ◽  
Frequency Dependent ◽  
Traveltime Tomography ◽  
First Arrival ◽  
Forward And Inverse Modeling ◽  
High Resolution Reconstruction

We applied Zelt's new frequency-dependent traveltime tomography (FDTT) method to 2D crosswell seismic field data from an eastern oil field in China. The FDTT uses the frequency content in the seismic waves in both the forward and inverse modeling steps. Although FDTT only uses a 300 Hz frequency to invert the dataset, the degree of matching between the inverted layers from FDTT and that of a sonic well logging curve is high, which shows that FDTT provides a high resolution reconstruction of subsurface structure through the simple use of the first-arrival traveltime data. The case study demonstrates that the FDTT algorithm is practical and can stand up to the complexities of a real 2D crosswell dataset. Additionally, we show that the FDTT method can create a high resolution long wavelength velocity model.

scholarly journals 2D High-Resolution Crosswell Seismic Traveltime Tomography

2020 ◽  
Vol 25 (1) ◽  
pp. 47-53
Author(s):  
Chuan Li ◽  
JianXin Liu ◽  
Jianping Liao ◽  
Andrew Hursthouse
Keyword(s):  
High Resolution ◽  
Eastern China ◽  
Velocity Model ◽  
Well Logging ◽  
Oil Field ◽  
Traveltime Tomography ◽  
Reference Velocity ◽  
Velocity Information ◽  
High Resolution Reconstruction

This paper presents a method for combining the hybrid eikonal solver and the prior velocity information to obtain high-resolution crosswell imaging. The hybrid eikonal solver in this technique can ensure rapid and reliable forward modeling of traveltime field in an unsmoothed velocity model. We also utilize the sonic well logging curve to properly develop an initial reference velocity model, and use the sonic well logging data as the prior information for the inversion part, which can restrict the problem of non-uniqueness. The results of the numerical experiment of traveltime in multi-layer media showed that the hybrid eikonal solver was more accurate than the finite difference method. The case study of an oil field in eastern China demonstrated that our method can derive a high-resolution reconstruction of the subsurface structure by inverting the primary traveltime datasets. These results suggest that even though the eikonal equation is a high frequency approximation to the wavefield, the hybrid eikonal solver can provide an accurate traveltime field in the forward modelling step of seismic crosswell tomography, which is critical to ensure high-resolution invert imaging in a highly heterogeneous environment.

APPARENT ATTENUATION DUE TO INTRABED MULTIPLES, II

Geophysics ◽  
1978 ◽  
Vol 43 (4) ◽  
pp. 730-737 ◽  
Author(s):  
M. Schoenberger ◽  
F. K. Levin
Keyword(s):  
Seismic Data ◽  
Field Data ◽  
Seismic Waves ◽  
Synthetic Seismograms ◽  
Frequency Dependent ◽  
Total Attenuation ◽  
The World ◽  
Apparent Attenuation

In a paper with the same title published in Geophysics (June 1974), we showed that synthetic seismograms from two wells gave a frequency‐dependent attenuation due to intrabed multiples of about 0.06 dB/wavelength. This loss was 1/3 to 1/2 of the total attenuation found for field data on lines near the wells. Our data sufficed to confirm the conclusion of O’Doherty and Anstey that attenuation caused by intrabed multiples may be appreciable, but the number of wells was insufficient to establish the magnitude of that attenuation in general. To get a better feel for intrabed multiple‐generated attenuation, we have computed losses for 31 additional wells from basins all over the world. Sonic and, where available, density logs were digitized every foot and converted into synthetic seismograms with 50 orders of intrabed multiples. Using the technique of the 1974 paper of extending the logs and placing an isolated reflector 2000 ft below the bottom of the wells, we computed attenuation constants for plane seismic waves that had traveled down and back through the subsurfaces defined by the logs. Computed constants varied from 0.01 dB/wavelength to 0.22 dB/wavelength. Total traveltimes ranged from 0.7 to 2.7 sec; the average was 1.9 sec. Attenuation constants computed from surface seismic data near four of the 31 wells gave values 1.3 to 7 times the corresponding intrabed constants. Thus, attenuation due to intrabed multiples accounts for an appreciable fraction of the observed attenuation but by no means all of it.

Anisotropic frequency-dependent spreading of seismic waves from first-arrival vertical seismic profile data analysis

Geophysics ◽  
2013 ◽  
Vol 78 (6) ◽  
pp. C41-C52 ◽  
Author(s):  
Amin Baharvand Ahmadi ◽  
Igor Morozov
Keyword(s):  
Seismic Waves ◽  
Seismic Profile ◽  
Anisotropic Scattering ◽  
Profile Data ◽  
Vertical Seismic Profile ◽  
Data Set ◽  
Frequency Dependent ◽  
Geometric Spreading ◽  
First Arrival ◽  
Viscoelastic Modeling

A model of first-arrival amplitude decay combining geometric spreading, scattering, and inelastic dissipation is derived from a multioffset, 3D vertical seismic profile data set. Unlike the traditional approaches, the model is formulated in terms of path integrals over the rays and without relying on the quality factor ([Formula: see text]) for rocks. The inversion reveals variations of geometric attenuation (wavefront curvatures and scattering, [Formula: see text]) and the effective attenuation parameter ([Formula: see text]) with depth. Both of these properties are also found to be anisotropic. Scattering and geometric spreading (focusing and defocusing) significantly affect seismic amplitudes at lower frequencies and shallower depths. Statistical analysis of model uncertainties quantitatively measures the significance of these results. The model correctly predicts the observed frequency-dependent first-arrival amplitudes at all frequencies. This and similar models can be applied to other types of waves and should be useful for true-amplitude studies, including inversion, inverse [Formula: see text]-filtering, and amplitude variations with offset analysis. With further development of petrophysical models of internal friction and elastic scattering, attenuation parameters [Formula: see text] and [Formula: see text] should lead to constraints on local heterogeneity and intrinsic physical properties of the rock. These parameters can also be used to build models of the traditional frequency-dependent [Formula: see text] for forward and inverse numerical viscoelastic modeling.

Crosswell seismic reflection/diffraction tomography: A reservoir characterization application

Geophysics ◽  
1994 ◽  
Vol 59 (3) ◽  
pp. 351-361 ◽  
Author(s):  
M. Ali C. Tura ◽  
Robert J. Greaves ◽  
Wafik B. Beydoun
Keyword(s):  
Data Acquisition ◽  
Field Data ◽  
Large Scale ◽  
Reservoir Characterization ◽  
Synthetic Data ◽  
Velocity Model ◽  
Oil Field ◽  
Diffraction Tomography ◽  
Median Filters ◽  
Zero Offset

A crosswell seismic experiment at the San Emidio oil field in Bakersfield, California, is carried out to evaluate crosswell reflection/diffraction tomography and image the interwell region to locate a possible pinchout zone. In this experiment, the two wells used are 2500 ft (762 m) apart, and the zone to be imaged is 11 000 ft (3350 m) to 13 000 ft (3960 m) deep. With the considered distances, this experiment forms the first large scale reservoir characterization application of crosswell reflection/diffraction tomography. A subset of the intended data, formed of two common receiver gathers and one common shot gather, was collected at the San Emidio oil field. The crosswell data display a wide variety of wave modes including tube waves, singly and multiply reflected/diffracted waves, and refracted waves. The data are processed using frequency filters, median filters, and spatial muting filters to enhance the reflected/diffracted energy. A 2-D layered velocity model with gradients is built using zero‐offset VSPs and full‐waveform acoustic logs from the two wells. This model is used to generate synthetic finite‐difference data for the field data acquisition geometry. The synthetic data are processed and imaged using the elastic ray‐Born 𝓁2-migration/inversion (ERBMI) method. A smooth 2-D velocity model incorporating only gradients and a few layers is used as a background model for the imaging. Considering the limited data acquisition geometry, synthetic data images compare favorably with the initial velocity model. With the encouraging results obtained from synthetic data, the ERBMI method, with the smooth background velocity model is used next to image the processed field data. Images obtained from the crosswell data show a good match with the reflected field in the zero‐offset VSPs and with migrated surface seismic data. From the interpretation of these images, the potential of this crosswell seismic method for answering questions regarding reservoir continuity and existence of pinchout zones can be seen.

Turning-ray tomography using a low-spatial-frequency model parameterization

Geophysics ◽  
2008 ◽  
Vol 73 (5) ◽  
pp. VE93-VE100 ◽  
Author(s):  
James L. Simmons
Keyword(s):  
Velocity Field ◽  
Spatial Frequency ◽  
Field Data ◽  
Velocity Model ◽  
Surface Velocity ◽  
Low Velocity ◽  
Arrival Times ◽  
Model Parameterization ◽  
First Arrival ◽  
Velocity Anomalies

A linear least-squares inversion is applied to the turning-ray first-arrival times of a shallow-marine seismic reflection data set to estimate the slowly varying (laterally and vertically) components of the near-surface velocity field. The velocity model is represented with a low-spatial-frequency parameterization (2D cubic B-splines) designed specifically for the predicted components of the data. This model parameterization effectively decouples the slowly varying background from the higher spatial-frequency component of the velocity field produced by shallow, low-velocity, gas-charged sands and allows the solution to be obtained in a single iteration. The observed first-arrival times (background and shallow anomaly-induced perturbations) and the slowly varying first-arrival times related to the background velocity are inverted separately. Similar velocity-model estimates result, demonstrating the decoupling imposed by the B-spline model parameterization. The background velocity and the low-velocity anomalies are best treated as separate inverse problems using very different model parameterizations. Ray tracing a synthetic model containing local low-velocity anomalies embedded in a smooth background does not accurately predict the anomaly-induced first-arrival time perturbations seen in the field data. Acoustic finite-difference waveform modeling shows that reflections and diffractions from the anomalies interfere with the diving-wave first arrivals. First-arrival times picked from the full-waveform synthetics more accurately predict the field data first-arrival times.

Imaging permafrost velocity structure using high resolution 3D seismic tomography

Geophysics ◽  
2011 ◽  
Vol 76 (5) ◽  
pp. B187-B198 ◽  
Author(s):  
Kumar Ramachandran ◽  
Gilles Bellefleur ◽  
Tom Brent ◽  
Michael Riedel ◽  
Scott Dallimore
Keyword(s):  
High Resolution ◽  
Velocity Structure ◽  
Velocity Model ◽  
Water Bodies ◽  
Unfrozen Water ◽  
3D Seismic ◽  
Tomographic Inversion ◽  
Near Surface ◽  
First Arrival ◽  
Velocity Variations

A 3D seismic survey (Mallik 3D), covering [Formula: see text] in the Mackenzie Delta area of Canada’s north, was conducted by industry in 2002. Numerous lakes and marine inundation create a complex near-surface structure in the permafrost terrain. Much of the near subsurface remains frozen but significant melt zones exist particularly from perennially unfrozen water bodies. This results in an irregular distribution of permafrost ice creating a complex pattern of low and high frequency near-surface velocity variations which induce significant traveltime distortions in surface seismic data. A high resolution 3D traveltime tomography study was employed to map the permafrost velocity structure utilizing first-arrival traveltimes picked from 3D seismic shot records. Approximately 900,000 traveltime picks from 3167 shots were used in the inversion. Tomographic inversion of the first-arrival traveltimes resulted in a smooth velocity model for the upper 200 m of the subsurface. Ray coverage in the model is excellent down to 200 m providing effective control for estimating velocities through tomographic inversion. Resolution tests conducted through horizontal and vertical checkerboard tests confirm the robustness of the velocity model in detailing small scale velocity variations. Well velocities were used to validate tomographic velocities. The tomographic velocities do not show systematic correlation with well velocities. The velocity model clearly images the permafrost velocity structure in lateral and vertical directions. It is inferred from the velocity model that the permafrost structure in the near subsurface is discontinuous. Extensions of surface water bodies in depth, characterized by low P-wave velocities, are well imaged by the velocity model. Deep lakes with unfrozen water, inferred from the tomographic velocity model, correlate with areas of strong amplitude blanking and frequency attenuation observed in processed reflection seismic stack sections.

3D seismic refraction traveltime tomography at a groundwater contamination site

Geophysics ◽  
2006 ◽  
Vol 71 (5) ◽  
pp. H67-H78 ◽  
Author(s):  
Colin A. Zelt ◽  
Aron Azaria ◽  
Alan Levander
Keyword(s):  
Groundwater Contamination ◽  
Velocity Structure ◽  
Seismic Refraction ◽  
Vertical Direction ◽  
Velocity Model ◽  
3D Seismic ◽  
Traveltime Tomography ◽  
3D Velocity Model ◽  
First Arrival ◽  
Tomographic Approach

We have applied traveltime tomography to 3D seismic refraction data collected at Hill Air Force Base, Utah, in an approximately [Formula: see text] area over a shallow [Formula: see text] groundwater contamination site. The purpose of this study is to test the ability of 3D first-arrival-time data to characterize the shallow environment and aid remediation efforts. The aquifer is bounded below by a clay aquiclude, into which a paleochannel has been incised and acts as a trap for dense nonaqueous phase liquid (DNAPL) contaminants. A regularized nonlinear tomographic approach was applied to [Formula: see text] first-arrival traveltimes to obtain the smoothest minimum-structure 3D velocity model. The resulting velocity model contains a velocity increase from less than [Formula: see text] in the upper [Formula: see text]. The model also contains a north-south-trending low-velocity feature interpreted to be the paleochannel, based on more than 100 wells in the area. Checkerboard tests show [Formula: see text] lateral resolution throughout most of the model. The preferred final model was chosen after a systematic test of the free parameters involved in the tomographic approach, including the starting model. The final velocity model compares favorably with a 3D poststack depth migration and 2D waveform inversion of coincident reflection data. While the long-wavelength features of the model reveal the primary target of the survey, the paleochannel, the velocity model is likely a very smooth characterization of the true velocity structure, particularly in the vertical direction, given the size of the first Fresnel zone for these data.

Joint refraction traveltime tomography and migration for multilayer near-surface imaging

Geophysics ◽  
2019 ◽  
Vol 84 (6) ◽  
pp. U31-U43
Author(s):  
Yihao Wang ◽  
Jie Zhang
Keyword(s):  
High Velocity ◽  
Velocity Structure ◽  
Joint Inversion ◽  
Velocity Model ◽  
Surface Velocity ◽  
Inversion Method ◽  
Near Surface ◽  
Traveltime Tomography ◽  
First Arrival ◽  
Migration Method

In near-surface velocity structure estimation, first-arrival traveltime tomography tends to produce a smooth velocity model. If the shallow structures include a weathering layer over high-velocity bedrock, first-arrival traveltime tomography may fail to recover the sharp interface. However, with the same traveltime data, refraction traveltime migration proves to be an effective tool for accurately mapping the refractor. The approach downward continues the refraction traveltime curves and produces an image (position) of the refractor for a given overburden velocity model. We first assess the validity of the refraction traveltime migration method and analyze its uncertainties with a simple model. We then develop a multilayer refraction traveltime migration method and apply the migration image to constrain traveltime tomographic inversion by imposing discontinuities at the refraction interfaces in model regularization. In each subsequent iteration, the shape of the migrated refractors and the velocity model are simultaneously updated. The synthetic tests indicate that the joint inversion method performs better than the conventional first-arrival traveltime tomography method with Tikhonov regularization and the delay-time method in reconstructing near-surface models with high-velocity contrasts. In application to field data, this method produces a more accurately resolved velocity model, which improves the quality of common midpoint stacking by making long-wavelength static corrections.

High Resolution Imaging of the South Hikurangi Subduction Zone, New Zealand, Using 2‐D Full‐Waveform Inversion

2020 ◽  
Author(s):  
Adnan Djeffal ◽  
Ingo Pecher ◽  
Satish Singh ◽  
Jari Kaipio
Keyword(s):  
New Zealand ◽  
High Resolution ◽  
Seismic Data ◽  
Waveform Inversion ◽  
Velocity Model ◽  
Seismic Profile ◽  
Full Waveform Inversion ◽  
Traveltime Tomography ◽  
Full Waveform ◽  
Velocity Images

<p>Large quantities of fluids are predicted to be expelled from compacting sediments on subduction margins. Fluid expulsion is thought to be focussed, but its exact locations are usually constrained on very small scales and rarely can be resolved using velocity images obtained from traditional velocity analysis and ray-based tomography because of their resolution and accuracy limitation. However, with recent advancement in computing power, the full waveform inversion (FWI) is a powerful alternative to those traditional approaches as it uses phase and amplitude information contained in seismic data to yield a high-resolution velocity model of the subsurface.</p><p>Here, we applied elastic FWI along an 85 Km long 2D multichannel seismic profile on the southern Hikurangi margin, New Zealand. Our processing sequence includes: (1) downward continuation, (2) 2D traveltime tomography, and (3) full waveform inversion of wide-angle seismic data. We will present the final high-resolution velocity model and our interpretation of the fluid flow regimes associated with both the deforming overriding plate and the subducting plate.</p>

Imaging high-resolution seismic velocity from walkaway vertical seismic profile data in a carbonate reservoir using acoustic waveform tomography

Geophysics ◽  
2018 ◽  
Vol 83 (3) ◽  
pp. B77-B85 ◽  
Author(s):  
Eric M. Takam Takougang ◽  
Youcef Bouzidi
Keyword(s):  
High Resolution ◽  
United Arab Emirates ◽  
Seismic Velocity ◽  
Velocity Model ◽  
Seismic Profile ◽  
Carbonate Reservoir ◽  
Oil Field ◽  
Vertical Seismic Profile ◽  
Final Velocity ◽  
Waveform Tomography

High-resolution seismic velocity was obtained using acoustic full-waveform tomography of walkaway vertical seismic profile (VSP) data from an oil field dominated by carbonate rocks, offshore Abu Dhabi in the United Arab Emirates. The data were collected in a deviated borehole with receivers located from 521 to 2742 m depth. The inversion was performed in the frequency domain. The success of the inversion was determined by three important factors: the starting model, the preconditioning of the input data, and the inversion strategy, which included an appropriate selection of a damping term [Formula: see text] in the Laplace–Fourier transformation. The inversion was performed between the frequencies of 4 and 50 Hz, and a logarithmic data residual was used. The extracted 1D velocity profiles from the final high-resolution velocity model correlate well with the sonic log, and estimated vertical incidence VSP velocities. The predicted data obtained by the final velocity model indicate a generally good fit with the field data, thus confirming the success of the inversion. A reverse time migrated section derived by the final velocity model provides additional structural details. The velocity model indicates anomalous zones of low-velocity values that correlate with known locations of hydrocarbon reservoirs.

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