Repeatability issues of 3-D VSP data

Geophysics ◽  
1999 ◽  
Vol 64 (6) ◽  
pp. 1673-1679 ◽  
Author(s):  
Martin Landrø
Keyword(s):  
Vertical Component ◽  
Time Lapse ◽  
Management Tool ◽  
Data Set ◽  
Hydrocarbon Reservoir ◽  
Vertical Seismic Profiling ◽  
Positioning Errors ◽  
Vsp Data ◽  
The Difference ◽  
Pressure Changes

Increased repeatability is recognized as one major issue for improving the time‐lapse seismic technology as a reservoir management tool. A 3-D vertical seismic profiling (VSP) data set, acquired over a period of two days, is used to analyze how repeatable a permanent installed geophone array can be and how repeatability changes with inaccuracies in source positioning. It is found that for a frequency range between 3.5 and 50 Hz, the difference root‐mean‐square (rms) level between two recorded traces belonging to two different shots is about 8%. This fact shows that there is a potential for acquiring very accurate time‐lapse seismic data by using a permanently installed downhole geophone array. Repeatability variation with increasing shot separation distances is analyzed, showing a rapid decrease in repeatability as the accuracy of the positioning of the repeat survey decreases. Horizontal geophone components show approximately the same degree of repeatability compared to the vertical component, but horizontal geophone data is slightly more sensitive to positioning errors. The results show that repeated 3-D VSP surveys (preferably using permanently installed geophone arrays) might be an efficient tool for detailed and precise monitoring of fluid and pressure changes within a hydrocarbon reservoir.

Analysis and removal of multiply scattered tube waves

Geophysics ◽  
2000 ◽  
Vol 65 (3) ◽  
pp. 745-754 ◽  
Author(s):  
Gérard C. Herman ◽  
Paul A. Milligan ◽  
Qicheng Dong ◽  
James W. Rector
Keyword(s):  
Wave Field ◽  
Large Amplitude ◽  
Data Set ◽  
Impedance Function ◽  
Seismic Profiling ◽  
Vertical Seismic Profiling ◽  
Total Data ◽  
Vsp Data ◽  
Tube Wave

Because of irregularities in or near the borehole, vertical seismic profiling (VSP) or crosswell data can be contaminated with scattered tube waves. These can have a large amplitude and can interfere with weaker upcoming reflections, destroying their continuity. This type of organized noise cannot always be removed with filtering methods currently in use. We propose a method based on modeling the scattered tube‐wave field and then subtracting it from the total data set. We assume that the scattering occurs close to the borehole axis and therefore use a 1-D impedance function to characterize borehole irregularities. Estimation of this impedance function is one of the first steps. Our method also accounts for multiply scattered tube waves. We apply the method to an actual VSP data set and conclude that the continuity of reflected, upcoming events improves significantly in a washout zone.

Correlation between seismic diffractions extracted from vertical seismic profiling data and borehole logging in a carbonate environment

2015 ◽  
Vol 3 (2) ◽  
pp. T121-T129 ◽  
Author(s):  
Alexander Klokov ◽  
Damir Irkabaev ◽  
Osareni C. Ogiesoba ◽  
Nail Munasypov
Keyword(s):  
Joint Analysis ◽  
Seismic Attribute ◽  
Data Set ◽  
Borehole Logging ◽  
Seismic Profiling ◽  
Vertical Seismic Profiling ◽  
Fluid Saturation ◽  
Attribute Analysis ◽  
Vsp Data ◽  
Tectonic Dislocations

Seismic diffractions may play an important role in seismic interpretation because they characterize geologic objects that might not be visible for conventional seismic attribute analysis. Diffractivity may be caused by, and consequently may define, tectonic dislocations (faults and fractures), lithologic variations, and fluid saturation within rocks. We have tied seismic diffractions extracted from vertical seismic profiling (VSP) data and borehole logging, from which we recognized the reasons that were responsible for diffractivity of the strata. First, we processed a multisource multicomponent VSP data set to extract seismic diffractions and constructed diffraction images of the strata for all three of the VSP data components. Then, we performed joint analysis of well logs and diffractions to obtain petrophysical attributes associated with diffraction images. We divided the rock succession into several units, which have different diffraction properties. We identified compacted rock, alternating intervals, isolated fractured zones, and fluid-saturated layers.

scholarly journals Application of time-lapse ERT imaging to watershed characterization

Geophysics ◽  
2008 ◽  
Vol 73 (3) ◽  
pp. G7-G17 ◽  
Author(s):  
Carlyle R. Miller ◽  
Partha S. Routh ◽  
Troy R. Brosten ◽  
James P. McNamara
Keyword(s):  
Reference Model ◽  
Time Lapse ◽  
Data Sets ◽  
Data Set ◽  
Resistivity Tomography ◽  
Practical Applications ◽  
Data Inversion ◽  
Time Periods ◽  
The Difference ◽  
Base Data

Time-lapse electrical resistivity tomography (ERT) has many practical applications to the study of subsurface properties and processes. When inverting time-lapse ERT data, it is useful to proceed beyond straightforward inversion of data differences and take advantage of the time-lapse nature of the data. We assess various approaches for inverting and interpreting time-lapse ERT data and determine that two approaches work well. The first approach is model subtraction after separate inversion of the data from two time periods, and the second approach is to use the inverted model from a base data set as the reference model or prior information for subsequent time periods. We prefer this second approach. Data inversion methodology should be consideredwhen designing data acquisition; i.e., to utilize the second approach, it is important to collect one or more data sets for which the bulk of the subsurface is in a background or relatively unperturbed state. A third and commonly used approach to time-lapse inversion, inverting the difference between two data sets, localizes the regions of the model in which change has occurred; however, varying noise levels between the two data sets can be problematic. To further assess the various time-lapse inversion approaches, we acquired field data from a catchment within the Dry Creek Experimental Watershed near Boise, Idaho, U.S.A. We combined the complimentary information from individual static ERT inversions, time-lapse ERT images, and available hydrologic data in a robust interpretation scheme to aid in quantifying seasonal variations in subsurface moisture content.

First-break vertical seismic profiling tomography for Vinton Salt Dome

Geophysics ◽  
2006 ◽  
Vol 71 (3) ◽  
pp. U29-U36 ◽  
Author(s):  
Hua-wei Zhou
Keyword(s):  
A Priori ◽  
Salt Dome ◽  
Data Set ◽  
Velocity Anisotropy ◽  
Seismic Profiling ◽  
Velocity Models ◽  
Vertical Seismic Profiling ◽  
Vsp Data ◽  
Multiscale Inversion ◽  
Sonic Logs

Building laterally depth-varying velocity models for vertical seismic profiling (VSP) imaging is challenging because of the narrow ray-angle coverage of VSP data, especially if only first arrivals are used. This study explores the potential of a new deformable-layer tomography (DLT) for building velocity models with a VSP data set acquired over the Vinton salt dome in southwestern Louisiana. The DLT method uses first breaks to constrain the geometry of velocity interfaces from an initial model of flat, constant-velocity layers parameterized using a priori geologic and geophysical information. A progressive multiscale inversion loop gradually updates the interface geometry. The final solution model, containing 3D geometry, is well supported by resolution and reliability tests and closely matches the long-wavelength trends of area sonic logs. The presence of velocity anisotropy is also indicated.

Estimating interval shear-wave splitting from multicomponent virtual shear check shots

Geophysics ◽  
2008 ◽  
Vol 73 (5) ◽  
pp. A39-A43 ◽  
Author(s):  
Andrey Bakulin ◽  
Albena Mateeva
Keyword(s):  
Shear Wave ◽  
Shear Wave Splitting ◽  
Azimuthal Anisotropy ◽  
Data Set ◽  
Vertical Seismic Profiling ◽  
Wave Splitting ◽  
Vsp Data ◽  
Classic Approach ◽  
A New Technique

Measuring shear-wave splitting from vertical seismic profiling (VSP) data can benefit fracture and stress characterization as well as seismic processing and interpretation. The classic approach to measuring azimuthal anisotropy at depth involves layer stripping. Its inherent weakness is the need to measure and undo overburden effects before arriving at an anisotropy estimate at depth. That task is challenging when the overburden is complex and varies quickly with depth. Moreover, VSP receivers are rarely present all the way from the surface to the target. That necessitates the use of simplistic assumptions about the uninstrumented part of the overburden that limit the quality of the result. We propose a new technique for measuring shear-wave splitting at depth that does not require any knowledge of the overburden. It is based on a multicomponent version of the virtual source method in which each two-component (2-C) VSP receiver is turned into a 2-C shear source and recorded at deeper geophones. The resulting virtual data set is affected only by the properties of the medium between the receivers. A simple Alford rotation transforms the data set into fast and slow shear virtual check shots from which shear-wave splitting can be measured easily and accurately under arbitrarily complex overburden.

Bayesian time-lapse inversion

Geophysics ◽  
2006 ◽  
Vol 71 (3) ◽  
pp. R43-R48 ◽  
Author(s):  
Arild Buland ◽  
Youness El Ouair
Keyword(s):  
Water Injection ◽  
Rock Physics ◽  
Real Data ◽  
Time Lapse ◽  
Baseline Survey ◽  
Inversion Method ◽  
Data Set ◽  
Uncertainty Calculation ◽  
The Difference ◽  
Fast Inversion

A new, fast inversion approach for time-lapse seismic data is developed where the uncertainty of the inversion results is an integral part of the solution. The inversion method estimates changes in the elastic material properties of a reservoir because of production of hydrocarbons, including uncertainty bounds on these estimates. The changes in elastic properties then can be related to changes in hydrocarbon saturation and reservoir pressure by using rock-physics relations. The inversion operates directly on the difference between a repeat survey and a baseline survey. This is advantageous with respect to the uncertainty calculation, because an estimate of the seismic uncertainty can be obtained directly from the difference data in zones not affected by production. The method is formulated in a Bayesian setting, and the solution is represented by explicit expressions for the posterior expectation and the covariance of the elastic parameter changes. The explicit analytical form of the posterior distribution provides a computationally fast inversion method. Results of the applied approach to a real data set from the Norne field are consistent with the expected effects of water flushing because of water injection.

Discrimination between pressure and fluid saturation changes from time‐lapse seismic data

Geophysics ◽  
2001 ◽  
Vol 66 (3) ◽  
pp. 836-844 ◽  
Author(s):  
Martin Landrø
Keyword(s):  
Seismic Data ◽  
Time Lapse ◽  
Seismic Survey ◽  
Baseline Survey ◽  
Water Contact ◽  
Data Set ◽  
Seismic Surveys ◽  
Fluid Saturation ◽  
Oil Water ◽  
Pressure Changes

Explicit expressions for computing saturation‐ and pressure‐related changes from time‐lapse seismic data have been derived and tested on a real time‐lapse seismic data set. Necessary input is near‐and far‐offset stacks for the baseline seismic survey and the repeat survey. The method has been tested successfully in a segment where pressure measurements in two wells verify a pore‐pressure increase of 5 to 6 MPa between the baseline survey and the monitor survey. Estimated pressure changes using the proposed relationships fit very well with observations. Between the baseline and monitor seismic surveys, 27% of the estimated recoverable hydrocarbon reserves were produced from this segment. The estimated saturation changes also agree well with observed changes, apart from some areas in the water zone that are mapped as being exposed to saturation changes (which is unlikely). Saturation changes in other segments close to the original oil‐water contact and the top reservoir interface are also estimated and confirmed by observations in various wells.

scholarly journals Elastic full-waveform inversion of vertical seismic profile data acquired with distributed acoustic sensors

Geophysics ◽  
2018 ◽  
Vol 83 (3) ◽  
pp. R273-R281 ◽  
Author(s):  
Anton Egorov ◽  
Julia Correa ◽  
Andrej Bóna ◽  
Roman Pevzner ◽  
Konstantin Tertyshnikov ◽  
...  
Keyword(s):  
Elastic Properties ◽  
Particle Velocity ◽  
Waveform Inversion ◽  
Vertical Component ◽  
Seismic Profile ◽  
Full Waveform Inversion ◽  
Vertical Seismic Profile ◽  
Data Set ◽  
Full Waveform ◽  
Vsp Data

Distributed acoustic sensing (DAS) is a rapidly developing technology particularly useful for the acquisition of vertical seismic profile (VSP) surveys. DAS data are increasingly used for seismic imaging, but not for estimating rock properties. We have developed a workflow for estimating elastic properties of the subsurface using full-waveform inversion (FWI) of DAS VSP data. Whereas conventional borehole geophones usually measure three components of particle velocity, DAS measures a single quantity, which is an approximation of the strain or strain rate along the fiber. Standard FWI algorithms are developed for particle velocity data, and hence their application to DAS data requires conversion of these data to particle velocity along the fiber. This conversion can be accomplished by a specially designed filter. Field measurements show that the conversion result is close to vertical particle velocity as measured by geophones. Elastic time-domain FWI of a synthetic multioffset VSP data set for a vertical well shows that the inversion of the vertical component alone is sufficient to recover elastic properties of the subsurface. Application of the proposed workflow to a multioffset DAS data set acquired at the CO2CRC Otway Project site in Victoria, Australia, reveals salient subhorizontal layering consistent with the known geology of the site. The inverted [Formula: see text] model at the well location matches the upscaled [Formula: see text] log with a correlation coefficient of 0.85.

Comparison of seismic attenuation models using zero-offset vertical seismic profiling (VSP) data

Geophysics ◽  
2005 ◽  
Vol 70 (2) ◽  
pp. F17-F25 ◽  
Author(s):  
Tommy Toverud ◽  
Bjørn Ursin
Keyword(s):  
Model Fitting ◽  
Seismic Attenuation ◽  
Data Set ◽  
Seismic Profiling ◽  
Vertical Seismic Profiling ◽  
Vsp Data ◽  
Seismic Frequencies ◽  
Standard Linear Solid ◽  
Attenuation Models ◽  
Zero Offset

For seismic frequencies it is common to use an empirical equation to model attenuation. Usually the attenuation coefficient is modeled with linear frequency dependence, a model referred to as the Kolsky-Futterman model. Other models have been suggested in the geophysical literature. We compare eight of these models on a zero-offset vertical seismic profiling (VSP) data set: the Kolsky-Futterman, the power law, the Kjartansson, the Müller, the Azimi second, the Azimi third, the Cole-Cole, and the standard linear solid (SLS) models. For three separate depth zones we estimate velocities and Q-values for all eight models. A least-squares model-fitting algorithm gives almost the same normalized misfit for all models. Thus, none of the models can be preferred or rejected based on the given data set. Slightly better overall results are obtained for the Kolsky-Futterman model; for one depth zone, the SLS model gave the best result.

Difference Fourier Analysis of Glucose Embedded and Frozen Hydrated Purple Membrane

1982 ◽  
Vol 40 ◽  
pp. 74-75
Author(s):  
Jules S. Jaffe ◽  
Robert M. Glaeser
Keyword(s):  
Purple Membrane ◽  
Data Set ◽  
High Resolution Data ◽  
X Ray ◽  
X Ray Crystallography ◽  
Fourier Techniques ◽  
Versus Protein ◽  
The Difference ◽  
Difference Fourier ◽  
Ideal Method

Although difference Fourier techniques are standard in X-ray crystallography it has only been very recently that electron crystallographers have been able to take advantage of this method. We have combined a high resolution data set for frozen glucose embedded Purple Membrane (PM) with a data set collected from PM prepared in the frozen hydrated state in order to visualize any differences in structure due to the different methods of preparation. The increased contrast between protein-ice versus protein-glucose may prove to be an advantage of the frozen hydrated technique for visualizing those parts of bacteriorhodopsin that are embedded in glucose. In addition, surface groups of the protein may be disordered in glucose and ordered in the frozen state. The sensitivity of the difference Fourier technique to small changes in structure provides an ideal method for testing this hypothesis.

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