Radiation from a downhole air gun source

Geophysics ◽  
1984 ◽  
Vol 49 (1) ◽  
pp. 27-36 ◽  
Author(s):  
Myung W. Lee ◽  
Alfred H. Balch ◽  
Kenneth R. Parrott
Keyword(s):  
Experimental Data ◽  
Seismic Energy ◽  
High Amplitude ◽  
Infinite Medium ◽  
Air Bubble ◽  
Seismic Profiling ◽  
Vertical Seismic Profiling ◽  
Air Gun ◽  
Tube Wave ◽  
Major Emphasis

This paper describes some characteristics of a downhole air gun as a source of seismic energy for a vertical seismic profiling (VSP) experiment at Salt Valley, Utah. The major emphasis is on primary radiations from the air gun source and secondary radiations from the bottom of the source hole. The observed primary radiation pattern agrees very well with theory developed for a volume displacement source acting on the axis of a fluid-filled hole. The observed secondary radiations, whose amplitudes were much stronger than the primary radiations, can be explained by calculating the wave field resulting from the application of an equivalent point force in an infinite medium, which was caused by the reflection of a tube wave at the bottom of the source hole. The experimental data also indicate that high‐amplitude compressional and shear wave multiples are generated between the bottom of the source hole and the air bubble.

Application of instantaneous rotations to S‐wave vertical seismic profiling

Geophysics ◽  
1997 ◽  
Vol 62 (5) ◽  
pp. 1365-1368
Author(s):  
M. Boulfoul ◽  
Doyle R. Watts
Keyword(s):  
High Amplitude ◽  
Seismic Profile ◽  
P Wave ◽  
Petroleum Exploration ◽  
S Wave ◽  
Amplitude Variation With Offset ◽  
Seismic Profiling ◽  
Vertical Seismic Profiling ◽  
Seismic Models ◽  
Low Amplitude

The petroleum exploration industry uses S‐wave vertical seismic profiling (VSP) to determine S‐wave velocities from downgoing direct arrivals, and S‐wave reflectivities from upgoing waves. Seismic models for quantitative calibration of amplitude variation with offset (AVO) data require S‐wave velocity profiles (Castagna et al., 1993). Vertical summations (Hardage, 1983) of the upgoing waves produce S‐wave composite traces and enable interpretation of S‐wave seismic profile sections. In the simplest application of amplitude anomalies, the coincidence of high amplitude P‐wave reflectivity and low amplitude S‐wave reflectivity is potentially a direct indicator of the presence of natural gas.

scholarly journals Tube Wave removal from vertical seismic profiling (VSP) surveys

2012 ◽  
Vol 2012 (1) ◽  
pp. 1-4
Author(s):  
Dariush Nadri ◽  
Milovan Urosevic ◽  
Paul Wilkes ◽  
Mehdi Asgharzadeh
Keyword(s):  
Seismic Profiling ◽  
Vertical Seismic Profiling ◽  
Tube Wave

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.

Comparison of vertical seismic profiling techniques

Geophysics ◽  
1993 ◽  
Vol 58 (1) ◽  
pp. 134-140 ◽  
Author(s):  
Linda J. Zimmerman ◽  
Sen T. Chen
Keyword(s):  
Three Dimensional ◽  
Seismic Profile ◽  
Oil Field ◽  
Seismic Profiles ◽  
Severe Problem ◽  
Seismic Profiling ◽  
Vertical Seismic Profiling ◽  
Imaging Characteristics ◽  
Profiling Techniques ◽  
Tube Wave

To study the imaging characteristics of various vertical seismic profiling techniques, two vertical seismic profiles (VSP) and a reversed vertical seismic profile (RVSP), where source and receiver positions are interchanged, were collected in the Loudon Oil Field in Illinois. Both VSPs were collected using a line of dynamite charges on the surface as sources. One was collected with geophones and the other with hydrophones as downhole receivers. The RVSP was collected by detonating 25 gram explosive charges in a well and detecting the seismic response with geophones at the surface. Three subsurface images (VSP with geophones, VSP with hydrophones, and RVSP) were produced using VSP-CDP transforms. For comparison, a surface seismic profile was collected along the same line with dynamite sources and vertical geophone receivers. The RVSP and hydrophone VSP stacked sections both produced higher frequency images at shallower depths than did the geophone VSP stacked section. However, the lower frequency geophone VSP stacked section produced an interpretable subsurface image at much greater depths than either the RVSP or the hydrophone VSP sections. The differences are due in part to the more powerful surface sources that were used for the VSPs than the downhole sources used for the RVSP. Furthermore, tube‐wave noise was a more severe problem for both the RVSP and the hydrophone VSP than for the geophone VSP. The results of this experiment demonstrate that if tube‐wave noise could be suppressed, hydrophone VSPs would provide attractive alternatives to geophone VSPs, because it is much easier and cheaper to deploy multilevel hydrophones downhole than geophones. Also, if a high‐powered, nondestructive source is developed, RVSP could be a practical alternative to VSP since one can easily lay out numerous receivers on the surface to record multioffset or three‐dimensional (3-D) VSP data.

Experimental studies on downhole seismic sources

Geophysics ◽  
1990 ◽  
Vol 55 (12) ◽  
pp. 1645-1651 ◽  
Author(s):  
S. T. Chen ◽  
E. A. Eriksen ◽  
M. A. Miller
Keyword(s):  
Experimental Studies ◽  
Signal Amplitude ◽  
P Wave ◽  
Seismic Profiling ◽  
Vertical Seismic Profiling ◽  
Air Gun ◽  
Significant Damage ◽  
Explosive Charges ◽  
Borehole Televiewer ◽  
Sonic Logging

Reversed vertical seismic profiling (RVSP) and crosshole seismology can produce detailed images around a well since they record higher frequency data than surface seismic. The key issue, however, is whether or not a source can be constructed that can deliver enough energy downhole and yet do no significant damage to the borehole. We have investigated various candidate downhole sources for reversed vertical seismic profiling and crosshole seismology. The potential sources studied included explosive charges, a perforating gun, an air gun, and a water gun. The studies were conducted in both open and cased holes in various lithologies. We found that an explosive charge or an air gun can be a viable direct source in both open and cased wells (cemented or free casing). In an open borehole or in a cased well (with new casing), neither explosive charges nor air gun produced damage that was detectable by the borehole televiewer. However, the long‐spaced sonic logging tool indicated that both sources may cause a deterioration of the cement bond between the formation and the casing where the cement is new and its integrity is questionable. The direct P-wave signal is found to be approximately linearly proportional to the amount of explosives used. The signal amplitude decreases as the transmitting distance increases approximately as the power law (−2.14).

An examination of tube wave noise in vertical seismic profiling data

Geophysics ◽  
1981 ◽  
Vol 46 (6) ◽  
pp. 892-903 ◽  
Author(s):  
B. A. Hardage
Keyword(s):  
Body Wave ◽  
Effective Means ◽  
Power Spectra ◽  
Effective Field ◽  
The Body ◽  
Seismic Profiles ◽  
Seismic Profiling ◽  
Vertical Seismic Profiling ◽  
Vsp Data ◽  
Tube Wave

Tube waves act as noise that camouflages upgoing and downgoing body wave events which are the fundamental seismic data measured in vertical seismic profiling (VSP). In two onshore vertical seismic profiles, the principal source of tube waves is shown to be surface ground roll that sweeps across the well head. Secondary tube wave sources revealed in these VSP data are the downhole geophone tool itself and the bottom of the borehole. Body wave signals are also shown to create tube waves when they arrive at significant impedance contrasts in the borehole such as changes in casing diameter. Computer simulated vertical geophone arrays are used to reduce these tube waves, but such arrays attenuate and filter body wave events unless static time shifts are made so that the body wave signal occurs at the same two‐way time at each geophone station. Consequently, actual downhole vertical geophone arrays are not an effective means by which tube waves can be eliminated. Power spectra comparisons of tube wave and compressional body wave events demonstrate that band‐pass filters designed to eliminate tube waves also suppress body wave signals. A simple but effective field technique for reducing tube waves is shown to be proper source offset. Using velocity filters to retrieve upgoing compressional events from VSP data heavily contaminated with tube wave noise yields in one example an agreement with surface measured reflections that is superior to that obtained from synthetic seismograms calculated from log data recorded in the same well.

Fracture detection using P-wave and S-wave vertical seismic profiling at The Geysers

Geophysics ◽  
1988 ◽  
Vol 53 (1) ◽  
pp. 76-84 ◽  
Author(s):  
E. L. Majer ◽  
T. V. McEvilly ◽  
F. S. Eastwood ◽  
L. R. Myer
Keyword(s):  
Fractured Rock ◽  
Geothermal Field ◽  
P Wave ◽  
Velocity Variation ◽  
Fracture Detection ◽  
S Wave ◽  
Fracture Geometry ◽  
Seismic Profiling ◽  
Vertical Seismic Profiling ◽  
The Geysers

In a pilot vertical seismic profiling study, P-wave and cross‐polarized S-wave vibrators were used to investigate the potential utility of shear‐wave anisotropy measurements in characterizing a fractured rock mass. The caprock at The Geysers geothermal field was found to exhibit about an 11 percent velocity variation between SH-waves and SV-waves generated by rotating the S-wave vibrator orientation to two orthogonal polarizations for each survey level in the well. The effect is generally consistent with the equivalent anisotropy expected from the known fracture geometry.

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