Low‐ and high‐frequency radiation from seismic sources in cased boreholes

Geophysics ◽  
1994 ◽  
Vol 59 (11) ◽  
pp. 1780-1785 ◽  
Author(s):  
Richard L. Gibson ◽  
Chengbin Peng
Keyword(s):  
Numerical Solutions ◽  
Low Frequency ◽  
Seismic Source ◽  
Seismic Sources ◽  
Radiation Patterns ◽  
Full Waveform ◽  
Amplitude Data ◽  
Analytic Expressions ◽  
Field Radiation ◽  
Borehole Seismic

An accurate characterization of borehole seismic sources is necessary to model and interpret waveforms observed in crosshole and reverse vertical seismic profiling (VSP) surveys, since the radiation pattern of a source will directly influence the amplitudes of elastic wave arrivals at receiver locations. Any attempt to study these data or perform inversions of amplitude data without incorporating the borehole effects will have serious limitations. Most previous studies of borehole seismic source radiation patterns have applied low‐frequency approximations to develop expressions for the radiation patterns of volume injection or stress sources (Heelan, 1953; White, 1960; White and Senghush, 1963; Lee and Balch, 1982; Lee, 1986; Kurkjian, 1986; Meredith, 1990; Winbow, 1991; Ben‐Menahem and Kostek, 1991). For example, Lee and Balch (1982) used this approach, along with a steepest descent solution, to derive closed‐form analytic expressions for the asymptotic far‐field radiation from sources located in uncased boreholes. Meredith (1990) applied the same methodology to study the radiation patterns of a variety of types of sources, though he also computed full waveform synthetic seismograms using the discrete wavenumber method. Likewise, Greenfield (1978) used full waveform numerical solutions to compute seismograms for force sources applied to the wall of a cylindrical cavity.

Borehole seismic‐source radiation pattern in transversely isotropic media

Geophysics ◽  
1995 ◽  
Vol 60 (1) ◽  
pp. 29-42 ◽  
Author(s):  
Wenjie Dong ◽  
M. Nafi Toksöz
Keyword(s):  
Radiation Effects ◽  
Low Frequency ◽  
Transversely Isotropic ◽  
Seismic Source ◽  
Wave Pattern ◽  
Radiation Patterns ◽  
S Wave ◽  
Source Radiation ◽  
Air Gun ◽  
Borehole Seismic

We extend previous discussions on crosswell tomography in anisotropic formations by deriving the radiation patterns of three typical downhole seismic sources (impulsive air gun or dynamite, wall‐clamped vertical vibrators, and cylindrical bender) inside a fluid‐filled borehole embedded in a transversely isotropic (TI) formation. The method of steepest descents, in conjuncture with the low‐frequency and far‐field assumptions, is applied to the exact displacement integrals of these sources to obtain their radiation patterns asymptotically. In spite of complications caused by quasi‐P‐ and quasi‐SV‐wave coupling and wavefront triplication in homogeneous TI media, the final results can still be expressed in slowness components determined by a ray direction, which is desired when source radiation effects are to be accounted for by ray‐based tomography techniques. Tests with the radiation patterns show that while the effect of anisotropy on P‐waves is moderate, its effect on the S‐wave pattern is significant even for slightly anisotropic formations. One can predict the S‐wave pattern from the sign of the Thomsen’s measure δ*.

Theoretical far‐field radiation from a low‐frequency horizontal acoustic point force in a vertical borehole

Geophysics ◽  
1986 ◽  
Vol 51 (4) ◽  
pp. 930-939 ◽  
Author(s):  
Andrew L. Kurkjian
Keyword(s):  
Body Force ◽  
Low Frequency ◽  
Vibration Sensor ◽  
Point Force ◽  
Small Radius ◽  
Seismic Sources ◽  
Low Frequencies ◽  
Field Radiation ◽  
Point Body ◽  
Vertical Borehole

A subsurface point body force can be realized using a body force on the axis of a small‐radius borehole drilled perpendicular to the force. This observation, originally made by Kitsunezaki (1980), is having a significant impact in shear‐wave logging, and may potentially affect downhole seismic sources. Applying the principle of reciprocity to this finding, a horizontal vibration sensor on the axis of a vertical hole will be unaffected by the existence of the hole at low frequencies. Numerical methods determine both the frequency below which, and the offset beyond which, borehole‐related effects are negligible. If the shear wavelength is greater than ten times the diameter of the hole and if the measurement is made at least one shear wavelength from the point force, then the borehole effects will be minimal.

The Wolfspar experience with low-frequency seismic source field data: Motivation, processing, and implications

2022 ◽  
Vol 41 (1) ◽  
pp. 9-18
Author(s):  
Andrew Brenders ◽  
Joe Dellinger ◽  
Imtiaz Ahmed ◽  
Esteban Díaz ◽  
Mariana Gherasim ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Seismic Data ◽  
Field Data ◽  
Model Building ◽  
Low Frequency ◽  
Seismic Source ◽  
Velocity Model ◽  
Seismic Sources ◽  
Velocity Model Building ◽  
Air Gun

The promise of fully automatic full-waveform inversion (FWI) — a (seismic) data-driven velocity model building process — has proven elusive in complex geologic settings, with impactful examples using field data unavailable until recently. In 2015, success with FWI at the Atlantis Field in the U.S. Gulf of Mexico demonstrated that semiautomatic velocity model building is possible, but it also raised the question of what more might be possible if seismic data tailor-made for FWI were available (e.g., with increased source-receiver offsets and bespoke low-frequency seismic sources). Motivated by the initial value case for FWI in settings such as the Gulf of Mexico, beginning in 2007 and continuing into 2021 BP designed, built, and field tested Wolfspar, an ultralow-frequency seismic source designed to produce seismic data tailor-made for FWI. A 3D field trial of Wolfspar was conducted over the Mad Dog Field in the Gulf of Mexico in 2017–2018. Low-frequency source (LFS) data were shot on a sparse grid (280 m inline, 2 to 4 km crossline) and recorded into ocean-bottom nodes simultaneously with air gun sources shooting on a conventional dense grid (50 m inline, 50 m crossline). Using the LFS data with FWI to improve the velocity model for imaging produced only incremental uplift in the subsalt image of the reservoir, albeit with image improvements at depths greater than 25,000 ft (approximately 7620 m). To better understand this, reprocessing and further analyses were conducted. We found that (1) the LFS achieved its design signal-to-noise ratio (S/N) goals over its frequency range; (2) the wave-extrapolation and imaging operators built into FWI and migration are very effective at suppressing low-frequency noise, so that densely sampled air gun data with a low S/N can still produce useable model updates with low frequencies; and (3) data density becomes less important at wider offsets. These results may have significant implications for future acquisition designs with low-frequency seismic sources going forward.

Radiation from seismic sources in cased and cemented boreholes

Geophysics ◽  
1994 ◽  
Vol 59 (4) ◽  
pp. 518-533 ◽  
Author(s):  
Richard L. Gibson
Keyword(s):  
Boundary Condition ◽  
Stationary Phase ◽  
Axial Stress ◽  
Broad Band ◽  
Low Frequency ◽  
Seismic Sources ◽  
Radiation Patterns ◽  
S Waves ◽  
Impedance Contrast ◽  
Phase Solution

Far‐field, stationary phase approximations are often used to study the radiation of P‐ and S‐waves from seismic sources located in boreholes, usually with an assumption of low frequency and in application to uncased boreholes. These two assumptions allow explicit analytical results for the radiation patterns to be derived, as boundary condition equations can be solved analytically in fairly simple forms. Applying the same methodology to cased and cemented boreholes, however, is much more difficult because of the increased number of simultaneous boundary condition equations. I circumvent this difficulty by solving the boundary condition equations numerically using propagator matrices, as is generally done in the calculation of synthetic full‐waveform acoustic logs. In this way, the assumption of low frequency is also avoided, and a generalized stationary‐phase solution for sources in general, concentrically layered borehole models is easily obtained. Computation of the radiation patterns for cased and uncased boreholes in various formations shows that the amplitude reduction, because of the introduction of casing, is a function of both source type and of formation velocities. Axial stress sources are less affected by the casing than either radial stress or volume‐injection sources, and as formation velocity decreases, the effect of the casing becomes more significant as the impedance contrast between steel and the formation becomes larger. The new generalized stationary‐phase solution also shows that as frequency approaches 1000 Hz, the results obtained by low‐frequency approximations for stress sources can be inaccurate and that the energy radiated from the source becomes more highly directed in the horizontal directions. The radiation pattern begins to change relatively rapidly as a function of frequency, so that the resulting observations from broad‐band sources will show changes in waveforms that mimic the effects of attenuation. These changes occur because the length of the source becomes important as wavelength decreases, demonstrating the need to consider the influence of frequency, as well as casing and cement, on source radiation.

A test of a controlled downhole seismic source

Geophysics ◽  
1989 ◽  
Vol 54 (9) ◽  
pp. 1193-1198
Author(s):  
G. J. Elbring ◽  
H. C. Hardee ◽  
B. N. P. Paulsson
Keyword(s):  
Broad Band ◽  
Seismic Source ◽  
Seismic Sources ◽  
Seismic Profiling ◽  
Vertical Seismic Profiling ◽  
Seismic Frequencies ◽  
New Instrumentation ◽  
Borehole Seismic

With the growing interest in borehole seismic investigations such as vertical seismic profiling and crosshole surveys, the need for new instrumentation has arisen, especially in the area of seismic sources. An ideal seismic downhole source should be nondestructive to the well, provide enough energy to be recorded at useful distances, produce a broad band of seismic frequencies, and create a reproducible signal. A prototype of a source that fits these requirements has been constructed and was described in a previous paper (Hardee et al., 1987).

The shape of things to come — Development and testing of a new marine vibrator source

2019 ◽  
Vol 38 (9) ◽  
pp. 680-690 ◽  
Author(s):  
Benoît Teyssandier ◽  
John J. Sallas
Keyword(s):  
Seismic Source ◽  
Test Facility ◽  
Data Sets ◽  
Far Field ◽  
Ocean Bottom ◽  
Air Gun ◽  
Seismic Image ◽  
Field Radiation ◽  
Technical Issues ◽  
To Come

Ten years ago, CGG launched a project to develop a new concept of marine vibrator (MV) technology. We present our work, concluding with the successful acquisition of a seismic image using an ocean-bottom-node 2D survey. The expectation for MV technology is that it could reduce ocean exposure to seismic source sound, enable new acquisition solutions, and improve seismic data quality. After consideration of our objectives in terms of imaging, productivity, acoustic efficiency, and operational risk, we developed two spectrally complementary prototypes to cover the seismic bandwidth. In practice, an array composed of several MV units is needed for images of comparable quality to those produced from air-gun data sets. Because coupling to the water is invariant, MV signals tend to be repeatable. Since far-field pressure is directly proportional to piston volumetric acceleration, the far-field radiation can be well controlled through accurate piston motion control. These features allow us to shape signals to match precisely a desired spectrum while observing equipment constraints. Over the last few years, an intensive validation process was conducted at our dedicated test facility. The MV units were exposed to 2000 hours of in-sea testing with only minor technical issues.

scholarly journals Multi-scale time-frequency domain full waveform inversion with a weighted local correlation-phase misfit function

2019 ◽  
Vol 16 (6) ◽  
pp. 1017-1031 ◽  
Author(s):  
Yong Hu ◽  
Liguo Han ◽  
Rushan Wu ◽  
Yongzhong Xu
Keyword(s):  
Frequency Domain ◽  
Seismic Data ◽  
Waveform Inversion ◽  
Low Frequency ◽  
Full Waveform Inversion ◽  
Local Correlation ◽  
Time Frequency ◽  
Model Dependence ◽  
Full Waveform ◽  
Frequency Components

Abstract Full Waveform Inversion (FWI) is based on the least squares algorithm to minimize the difference between the synthetic and observed data, which is a promising technique for high-resolution velocity inversion. However, the FWI method is characterized by strong model dependence, because the ultra-low-frequency components in the field seismic data are usually not available. In this work, to reduce the model dependence of the FWI method, we introduce a Weighted Local Correlation-phase based FWI method (WLCFWI), which emphasizes the correlation phase between the synthetic and observed data in the time-frequency domain. The local correlation-phase misfit function combines the advantages of phase and normalized correlation function, and has an enormous potential for reducing the model dependence and improving FWI results. Besides, in the correlation-phase misfit function, the amplitude information is treated as a weighting factor, which emphasizes the phase similarity between synthetic and observed data. Numerical examples and the analysis of the misfit function show that the WLCFWI method has a strong ability to reduce model dependence, even if the seismic data are devoid of low-frequency components and contain strong Gaussian noise.

A new parameter set for anisotropic multiparameter full-waveform inversion and application to a North Sea data set

Geophysics ◽  
2016 ◽  
Vol 81 (4) ◽  
pp. U25-U38 ◽  
Author(s):  
Nuno V. da Silva ◽  
Andrew Ratcliffe ◽  
Vetle Vinje ◽  
Graham Conroy
Keyword(s):  
North Sea ◽  
Waveform Inversion ◽  
Real Data ◽  
Model Parameters ◽  
Full Waveform Inversion ◽  
Radiation Patterns ◽  
Data Set ◽  
Full Waveform ◽  
Seismic Image ◽  
Central North Sea

Parameterization lies at the center of anisotropic full-waveform inversion (FWI) with multiparameter updates. This is because FWI aims to update the long and short wavelengths of the perturbations. Thus, it is important that the parameterization accommodates this. Recently, there has been an intensive effort to determine the optimal parameterization, centering the fundamental discussion mainly on the analysis of radiation patterns for each one of these parameterizations, and aiming to determine which is best suited for multiparameter inversion. We have developed a new parameterization in the scope of FWI, based on the concept of kinematically equivalent media, as originally proposed in other areas of seismic data analysis. Our analysis is also based on radiation patterns, as well as the relation between the perturbation of this set of parameters and perturbation in traveltime. The radiation pattern reveals that this parameterization combines some of the characteristics of parameterizations with one velocity and two Thomsen’s parameters and parameterizations using two velocities and one Thomsen’s parameter. The study of perturbation of traveltime with perturbation of model parameters shows that the new parameterization is less ambiguous when relating these quantities in comparison with other more commonly used parameterizations. We have concluded that our new parameterization is well-suited for inverting diving waves, which are of paramount importance to carry out practical FWI successfully. We have demonstrated that the new parameterization produces good inversion results with synthetic and real data examples. In the latter case of the real data example from the Central North Sea, the inverted models show good agreement with the geologic structures, leading to an improvement of the seismic image and flatness of the common image gathers.

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