You must log in to edit PetroWiki. Help with editing

Content of PetroWiki is intended for personal use only and to supplement, not replace, engineering judgment. SPE disclaims any and all liability for your use of such content. More information


Borehole seismic applications: Difference between revisions

PetroWiki
Jump to navigation Jump to search
No edit summary
No edit summary
 
(One intermediate revision by the same user not shown)
Line 1: Line 1:
Reservoir geophysics should aggressively take advantage of data from boreholes that are very close to the target itself, not just for correlating seismic data to the well but also using those wells for the collection of novel geophysical data from below the noisy surface or weathered zone. New techniques for acquisition of seismic data from wellbores are available, and should become routine tools in the arsenal of the reservoir geophysicist.
Reservoir geophysics should aggressively take advantage of data from boreholes that are very close to the target itself, not just for correlating seismic data to the well but also using those wells for the collection of novel geophysical data from below the noisy surface or weathered zone. New techniques for acquisition of seismic data from wellbores are available, and should become routine tools in the arsenal of the reservoir geophysicist.


==Single-well techniques==
== Single-well techniques ==


Single-well techniques involve placing seismic sources and receivers in the same well and include:
Single-well techniques involve placing seismic sources and receivers in the same well and include:


* Sonic logging
*Sonic logging
* Single-well imaging
*Single-well imaging


===Sonic logging===
=== Sonic logging ===
[[Acoustic logging|Sonic logging]] has become routine, and the collection of [[compressional and shear velocities]] in fast and slow formations is more-or-less straightforward, particularly with the use of dipole sonic tools and waveform processing. The application of modified sonic-logging tools for imaging near the wellbore is not routine but has been demonstrated in several cases; research and development continues in this area.


Modern sonic logging tools can provide a good measure of compressional and shear velocities, values that are required for calibrating seismic data at wells and for the investigation of lithology and fluid content from seismic data. Of course, the interpreter must be careful to know if the data represent invaded or uninvaded conditions and make appropriate corrections if necessary. Modern sonic logging tools can often provide reliable values for velocities through casing; often, the most-reliable sonic logs in soft shales can only be found behind casing because of the inability to log openhole the depth intervals in which shales are flowing or collapsing.  
[[Acoustic_logging|Sonic logging]] has become routine, and the collection of [[Compressional_and_shear_velocities|compressional and shear velocities]] in fast and slow formations is more-or-less straightforward, particularly with the use of dipole sonic tools and waveform processing. The application of modified sonic-logging tools for imaging near the wellbore is not routine but has been demonstrated in several cases; research and development continues in this area.


Compressional sonic log values are used in reservoir geophysics to tie well depths to seismic two-way travel time. First the sonic transit time is integrated to obtain a depth-calibrated time scale, then synthetic seismograms are created through determination of reflection coefficients (including the [[Density logging|density log]]) and convolution with a known or assumed wavelet. This synthetic seismogram is often adjusted to account for:
Modern sonic logging tools can provide a good measure of compressional and shear velocities, values that are required for calibrating seismic data at wells and for the investigation of lithology and fluid content from seismic data. Of course, the interpreter must be careful to know if the data represent invaded or uninvaded conditions and make appropriate corrections if necessary. Modern sonic logging tools can often provide reliable values for velocities through casing; often, the most-reliable sonic logs in soft shales can only be found behind casing because of the inability to log openhole the depth intervals in which shales are flowing or collapsing.


* Borehole effects
Compressional sonic log values are used in reservoir geophysics to tie well depths to seismic two-way travel time. First the sonic transit time is integrated to obtain a depth-calibrated time scale, then synthetic seismograms are created through determination of reflection coefficients (including the [[Density_logging|density log]]) and convolution with a known or assumed wavelet. This synthetic seismogram is often adjusted to account for:
* Absence of data in the shallowest section
* Other unspecified effects, including velocity dispersion caused by thin-bed layering below seismic resolution


The shear sonic log values are then added to create synthetic seismograms that demonstrate [[Seismic attributes for reservoir studies|AVO]] behavior for comparison with the prestack data near the well. Often, additional work is conducted to model the changes in seismic response when rocks of slightly different lithology or fluid saturation are encountered away from the well. Both the compressional and shear sonic data are required to accomplish fluid-substitution modeling, although some empirical models and other short-cuts are available.<ref name="r1" /> The most common fluid substitution models employ Gassmann<ref name="r2" /> in clastic rocks; a number of models also exists for fractured rocks.<ref name="r3" />
*Borehole effects
*Absence of data in the shallowest section
*Other unspecified effects, including velocity dispersion caused by thin-bed layering below seismic resolution


===Single well imaging===
The shear sonic log values are then added to create synthetic seismograms that demonstrate [[Seismic_attributes_for_reservoir_studies|AVO]] behavior for comparison with the prestack data near the well. Often, additional work is conducted to model the changes in seismic response when rocks of slightly different lithology or fluid saturation are encountered away from the well. Both the compressional and shear sonic data are required to accomplish fluid-substitution modeling, although some empirical models and other short-cuts are available.<ref name="r1">Mavko, G., Chan, C., and Mukerji, T. 1995. Fluid Substitution: Estimating Change in Vp Without Knowing Vs. Geophysics 60 (6): 1750. http://dx.doi.org/10.1190/1.1443908</ref> The most common fluid substitution models employ Gassmann<ref name="r2">Gassmann, F. 1951. Uber die Elastizitat poroser Medien, Vier. Der Natur. Gesellshaft in Zurich 96: 1–23.</ref> in clastic rocks; a number of models also exists for fractured rocks.<ref name="r3">Mavko, G., Mukerji, T., and Dvorkin, J. 1998. The Rock Physics Handbook: Tools for Seismic Analysis in Porous Media, 329. Cambridge, UK: Cambridge University Press.</ref>
Single-well imaging, although not yet widespread, may provide a useful tool for detailed close-up structural studies, such as salt-proximity studies designed to assist in the planning of a development sidetrack from an exploration well, or in determining the location of interfaces with respect to a horizontal well. In general, a sonic-logging tool or a string of VSP receivers (geophones and/or hydrophones), coupled with a downhole seismic source, is lowered into the well, often using tubing-conveyed methods in highly deviated wells. The experiment then becomes similar to a surface reflection-seismic experiment, except that reflections may come from any direction around the well, not just from beneath it. The technique has been shown to be useful to image fractures<ref name="r4" /> and to determine proximity to upper and lower interfaces in horizontal wells<ref name="r5" /> as demonstrated in '''Fig. 1'''.  


<gallery widths=300px heights=200px>
=== Single well imaging ===
 
Single-well imaging, although not yet widespread, may provide a useful tool for detailed close-up structural studies, such as salt-proximity studies designed to assist in the planning of a development sidetrack from an exploration well, or in determining the location of interfaces with respect to a horizontal well. In general, a sonic-logging tool or a string of VSP receivers (geophones and/or hydrophones), coupled with a downhole seismic source, is lowered into the well, often using tubing-conveyed methods in highly deviated wells. The experiment then becomes similar to a surface reflection-seismic experiment, except that reflections may come from any direction around the well, not just from beneath it. The technique has been shown to be useful to image fractures<ref name="r4">Hornby, B.E. et al. 1992. Reservoir Sonics: A North Sea Case Study. Geophysics 57 (1): 146–160. http://dx.doi.org/10.1190/1.1443178</ref> and to determine proximity to upper and lower interfaces in horizontal wells<ref name="r5">Yamamoto, H., Watanabe, S., Koelman, J.M.V. et al. 2000. Borehole Acoustic Reflection Survey Experiments in Horizontal Wells for Accurate Well Positioning. Presented at the SPE/CIM International Conference on Horizontal Well Technology, Calgary, Alberta, Canada, 6-8 November 2000. SPE-65538-MS. http://dx.doi.org/10.2118/65538-MS.</ref> as demonstrated in '''Fig. 1'''.
 
<gallery widths="300px" heights="200px">
File:Vol.6 F1.23.jpg|'''Fig. 1—Single-well imaging. The use of a string of receivers and a seismic source in a highly deviated well is shown in this example to provide an image showing the proximity of the well to layers of interest above and below it.<ref name="r5" />'''
File:Vol.6 F1.23.jpg|'''Fig. 1—Single-well imaging. The use of a string of receivers and a seismic source in a highly deviated well is shown in this example to provide an image showing the proximity of the well to layers of interest above and below it.<ref name="r5" />'''
</gallery>
</gallery>


==Multiple-well techniques==
== Multiple-well techniques ==


By placing a seismic source in one well and receivers in another well, a seismic velocity model between the two wells can be constructed using tomographic techniques, and a reflection image can be obtained by processing the reflected arrivals.<ref name="r6" /> Although the images are constrained to lie in a plane connecting the two wells, the additional fine-scale information, available from such surveys,<ref name="r7" /> can be of significant value to the reservoir engineer ('''Fig. 2''').  
By placing a seismic source in one well and receivers in another well, a seismic velocity model between the two wells can be constructed using tomographic techniques, and a reflection image can be obtained by processing the reflected arrivals.<ref name="r6">Lazaratos, S.K. et al. 1995. High-Resolution Crosswell Imaging of a West Texas Carbonate Reservoir: Part 4, Reflection Imaging. Geophysics 60 (3): 702. http://dx.doi.org/10.1190/1.1443809</ref> Although the images are constrained to lie in a plane connecting the two wells, the additional fine-scale information, available from such surveys,<ref name="r7">Harris, J.M. et al. 1995. High-Resolution Crosswell Imaging of a West Texas Carbonate Reservoir: Part 1, Project Summary and Interpretation. Geophysics 60 (3): 667. http://dx.doi.org/10.1190/1.1443806</ref> can be of significant value to the reservoir engineer ('''Fig. 2''').


<gallery widths=300px heights=200px>
<gallery widths="300px" heights="200px">
File:Vol.6 F1.25.jpg|'''Fig. 2—An example of crosswell imaging and the associated surface seismic and log data, showing the relative scales involved (after Harris et al.72).<ref name="r7" />'''
File:Vol.6 F1.25.jpg|'''Fig. 2—An example of crosswell imaging and the associated surface seismic and log data, showing the relative scales involved (after Harris et al.72).<ref name="r7" />'''
</gallery>
</gallery>


==Well-to-surface techniques==
== Well-to-surface techniques ==


Methods of calibrating seismic data and imaging that involve sources and/or receivers in one well and others at the surface include checkshot surveys, VSP, reverse VSP, and seismic-while-drilling. Checkshots and VSPs were developed primarily to assist in the tie between surface seismic data and well observations, but they have been extended beyond that in many cases. VSPs provide the best data for detailed event identification and wavelet determination, but they can also be used to image the near-wellbore environment, and the image can be improved if a number of offsets and azimuths (for a 3D VSP) are used for the source location. The ability to create a 3D image from borehole methods is greatly enhanced by placing a seismic source<ref name="r8" /><ref name="r9" /> in one well and deploying surface receivers, which are already around the well, in a reverse VSP configuration. Images from such experiments can be highly detailed<ref name="r10" /> (see '''Fig. 3'''), and the time required for 3D reverse VSP acquisition is significantly reduced over the 3D VSP case in which the source is moved around the surface.  
Methods of calibrating seismic data and imaging that involve sources and/or receivers in one well and others at the surface include checkshot surveys, VSP, reverse VSP, and seismic-while-drilling. Checkshots and VSPs were developed primarily to assist in the tie between surface seismic data and well observations, but they have been extended beyond that in many cases. VSPs provide the best data for detailed event identification and wavelet determination, but they can also be used to image the near-wellbore environment, and the image can be improved if a number of offsets and azimuths (for a 3D VSP) are used for the source location. The ability to create a 3D image from borehole methods is greatly enhanced by placing a seismic source<ref name="r8">Paulsson, B., Fairborn, J., and Fuller, B. 1997. Single Well Seismic Imaging and Reverse VSP Applications for the Downhole Seismic Vibrator. Paper 2029 presented at the 1997 Society of Exploration Geophysicists Annual Intl. Meeting, Dallas, 2–7 November.</ref><ref name="r9">Daley, T.M. and Cox, D. 2001. Orbital Vibrator Seismic Source for Simultaneous P- and S-Wave Crosswell Acquisition. Geophysics 66 (5): 1471. http://dx.doi.org/10.1190/1.1487092</ref> in one well and deploying surface receivers, which are already around the well, in a reverse VSP configuration. Images from such experiments can be highly detailed<ref name="r10">Turpening, R. et al. 2000. Imaging with Reverse Vertical Profiles Using a Downhole Hydraulic Axial Vibrator. Paper presented at the 2000 Society of Exploration Geophysicists Intl. Exposition and Annual Meeting, Calgary, 6–11 August.</ref> (see '''Fig. 3'''), and the time required for 3D reverse VSP acquisition is significantly reduced over the 3D VSP case in which the source is moved around the surface.


<gallery widths=300px heights=200px>
<gallery widths="300px" heights="200px">
File:Vol.6 F1.24.jpg|'''Fig. 3—VSP and reverse VSP reflection images of different portions of the same reef in Michigan. The left image was obtained using surface sources in a VSP configuration, and the right image was obtained using a downhole source in a reverse VSP configuration. The Earth model is also shown (after Turpening et al.66).<ref name="r10" />'''
File:Vol.6 F1.24.jpg|'''Fig. 3—VSP and reverse VSP reflection images of different portions of the same reef in Michigan. The left image was obtained using surface sources in a VSP configuration, and the right image was obtained using a downhole source in a reverse VSP configuration. The Earth model is also shown (after Turpening et al.66).<ref name="r10" />'''
</gallery>
</gallery>


The drill bit can also be used as a seismic source<ref name="r11" /> much like an uncontrolled, but monitored, vibrator; it is capable of providing, in at least some instances, information useful for selecting casing or coring points and for estimating proximity to overpressure zones.<ref name="r12" /><ref name="r13" /> Through the use of receivers in a logging-while-drilling unit near the bit, a surface VSP source can be recorded during pauses in the drilling operation, which occur as a new joint of pipe is being added.<ref name="r14" />
The drill bit can also be used as a seismic source<ref name="r11">Rector, J.W. III and Marion, B.P. 1991. The Use of Drill-Bit Energy as a Downhole Seismic Source. Geophysics 56 (5): 628. http://dx.doi.org/10.1190/1.1443079</ref> much like an uncontrolled, but monitored, vibrator; it is capable of providing, in at least some instances, information useful for selecting casing or coring points and for estimating proximity to overpressure zones.<ref name="r12">Miranda, F. et al. 1996. Impact of Seismic ‘While Drilling’ Technique on Exploration Wells. First Break 14 (2): 55. http://dx.doi.org/10.3997/1365-2397.1996004</ref><ref name="r13">Kulkarni, R., Meyer, J.H., and Sixta, D. 1999. Are Pore-Pressure Related Drilling Problems Predictable? The Value of Using Seismic Before and while Drilling. Paper presented at the 1999 Society of Exploration Geophysicists Intl. Exposition and Annual Meeting, Houston, 31 October–5 November.</ref> Through the use of receivers in a logging-while-drilling unit near the bit, a surface VSP source can be recorded during pauses in the drilling operation, which occur as a new joint of pipe is being added.<ref name="r14">Underhill, W., Esmersoy, C., Hawthorn, A. et al. 2001. Demonstrations of Real-Time Borehole Seismic From an LWD Tool. Presented at the SPE Annual Technical Conference and Exhibition, New Orleans, Louisiana, 30 September-3 October 2001. SPE-71365-MS. http://dx.doi.org/10.2118/71365-MS.</ref>
 
== References ==
 
<references />


==References==
== Noteworthy papers in OnePetro ==
<references>
<ref name="r1">Mavko, G., Chan, C., and Mukerji, T. 1995. Fluid Substitution: Estimating Change in Vp Without Knowing Vs. ''Geophysics'' '''60''' (6): 1750. http://dx.doi.org/10.1190/1.1443908</ref>
<ref name="r2">Gassmann, F. 1951. Uber die Elastizitat poroser Medien, Vier. Der Natur. Gesellshaft in Zurich 96: 1–23.</ref>
<ref name="r3">Mavko, G., Mukerji, T., and Dvorkin, J. 1998. ''The Rock Physics Handbook: Tools for Seismic Analysis in Porous Media'', 329. Cambridge, UK: Cambridge University Press.</ref>
<ref name="r4">Hornby, B.E. et al. 1992. Reservoir Sonics: A North Sea Case Study. ''Geophysics'' '''57''' (1): 146–160. http://dx.doi.org/10.1190/1.1443178</ref>
<ref name="r5">Yamamoto, H., Watanabe, S., Koelman, J.M.V. et al. 2000. Borehole Acoustic Reflection Survey Experiments in Horizontal Wells for Accurate Well Positioning. Presented at the SPE/CIM International Conference on Horizontal Well Technology, Calgary, Alberta, Canada, 6-8 November 2000. SPE-65538-MS. http://dx.doi.org/10.2118/65538-MS. </ref>
<ref name="r6">Lazaratos, S.K. et al. 1995. High-Resolution Crosswell Imaging of a West Texas Carbonate Reservoir: Part 4, Reflection Imaging. ''Geophysics'' '''60''' (3): 702. http://dx.doi.org/10.1190/1.1443809 </ref>
<ref name="r7">Harris, J.M. et al. 1995. High-Resolution Crosswell Imaging of a West Texas Carbonate Reservoir: Part 1, Project Summary and Interpretation. ''Geophysics'' '''60''' (3): 667. http://dx.doi.org/10.1190/1.1443806</ref>
<ref name="r8">Paulsson, B., Fairborn, J., and Fuller, B. 1997. Single Well Seismic Imaging and Reverse VSP Applications for the Downhole Seismic Vibrator. Paper 2029 presented at the 1997 Society of Exploration Geophysicists Annual Intl. Meeting, Dallas, 2–7 November.</ref>
<ref name="r9">Daley, T.M. and Cox, D. 2001. Orbital Vibrator Seismic Source for Simultaneous P- and S-Wave Crosswell Acquisition. ''Geophysics'' '''66''' (5): 1471. http://dx.doi.org/10.1190/1.1487092</ref>
<ref name="r10">Turpening, R. et al. 2000. Imaging with Reverse Vertical Profiles Using a Downhole Hydraulic Axial Vibrator. Paper presented at the 2000 Society of Exploration Geophysicists Intl. Exposition and Annual Meeting, Calgary, 6–11 August.</ref>
<ref name="r11">Rector, J.W. III and Marion, B.P. 1991. The Use of Drill-Bit Energy as a Downhole Seismic Source. ''Geophysics'' '''56''' (5): 628. http://dx.doi.org/10.1190/1.1443079</ref>
<ref name="r12">Miranda, F. et al. 1996. Impact of Seismic ‘While Drilling’ Technique on Exploration Wells. ''First Break'' '''14''' (2): 55. http://dx.doi.org/10.3997/1365-2397.1996004</ref>
<ref name="r13">Kulkarni, R., Meyer, J.H., and Sixta, D. 1999. Are Pore-Pressure Related Drilling Problems Predictable? The Value of Using Seismic Before and while Drilling. Paper presented at the 1999 Society of Exploration Geophysicists Intl. Exposition and Annual Meeting, Houston, 31 October–5 November.</ref>
<ref name="r14">Underhill, W., Esmersoy, C., Hawthorn, A. et al. 2001. Demonstrations of Real-Time Borehole Seismic From an LWD Tool. Presented at the SPE Annual Technical Conference and Exhibition, New Orleans, Louisiana, 30 September-3 October 2001. SPE-71365-MS. http://dx.doi.org/10.2118/71365-MS. </ref>
</references>


==Noteworthy papers in OnePetro==
Baker, L.J. and Hurris, J.M. Cross-Borehole Seismic Imaging. Presented at the 1984/1/1/.
Baker, L.J. and Hurris, J.M. Cross-Borehole Seismic Imaging. Presented at the 1984/1/1/.  


Dobecki, T.L. Hydraulic Fracture Orientation Using Passive Borehole Seismics. Presented at the 1983/1/1/. http://dx.doi.org/10.2118/12110-MS.  
Dobecki, T.L. Hydraulic Fracture Orientation Using Passive Borehole Seismics. Presented at the 1983/1/1/. [http://dx.doi.org/10.2118/12110-MS http://dx.doi.org/10.2118/12110-MS].


Justice, J.H. Borehole Seismic Technology For Reservoir Imaging. Presented at the 1993/1/1/. http://dx.doi.org/10.4043/7080-MS.  
Justice, J.H. Borehole Seismic Technology For Reservoir Imaging. Presented at the 1993/1/1/. [http://dx.doi.org/10.4043/7080-MS http://dx.doi.org/10.4043/7080-MS].


Kramer, D. Multicomponent Multioffset VSP Processing. Presented at the 1991/1/1/.  
Kramer, D. Multicomponent Multioffset VSP Processing. Presented at the 1991/1/1/.


Washbourne, J.K., Bube, K.P., Antonelli, M. et al. Crosswell Reflection Tomography. Presented at the 2002/1/1/.  
Washbourne, J.K., Bube, K.P., Antonelli, M. et al. Crosswell Reflection Tomography. Presented at the 2002/1/1/.
 
== External links ==


==External links==
Use this section to provide links to relevant material on websites other than PetroWiki and OnePetro
Use this section to provide links to relevant material on websites other than PetroWiki and OnePetro


==See also==
== See also ==
[[Reservoir geophysics overview]]
 
[[Reservoir_geophysics_overview|Reservoir geophysics overview]]


[[Seismic imaging and inversion]]
[[Seismic_imaging_and_inversion|Seismic imaging and inversion]]


[[Seismic time-lapse reservoir monitoring]]
[[Seismic_time-lapse_reservoir_monitoring|Seismic time-lapse reservoir monitoring]]


[[Passive seismic monitoring]]
[[Passive_seismic_monitoring|Passive seismic monitoring]]


[[Hydraulic fracture monitoring]]
[[Hydraulic_fracture_monitoring|Hydraulic fracture monitoring]]


[[Pore pressure prediction using seismic]]
[[Pore_pressure_prediction_using_seismic|Pore pressure prediction using seismic]]


[[Pore fluid effects on rock mechanics]]
[[Pore_fluid_effects_on_rock_mechanics|Pore fluid effects on rock mechanics]]


[[PEH:Reservoir Geophysics]]
[[PEH:Reservoir_Geophysics]]


[[Category:3.3.2 Borehole Imaging and Wellbore Seismic]]
== Category ==
[[Category:3.3.2 Borehole imaging and wellbore seismic]] [[Category:YR]]

Latest revision as of 16:16, 2 July 2015

Reservoir geophysics should aggressively take advantage of data from boreholes that are very close to the target itself, not just for correlating seismic data to the well but also using those wells for the collection of novel geophysical data from below the noisy surface or weathered zone. New techniques for acquisition of seismic data from wellbores are available, and should become routine tools in the arsenal of the reservoir geophysicist.

Single-well techniques

Single-well techniques involve placing seismic sources and receivers in the same well and include:

  • Sonic logging
  • Single-well imaging

Sonic logging

Sonic logging has become routine, and the collection of compressional and shear velocities in fast and slow formations is more-or-less straightforward, particularly with the use of dipole sonic tools and waveform processing. The application of modified sonic-logging tools for imaging near the wellbore is not routine but has been demonstrated in several cases; research and development continues in this area.

Modern sonic logging tools can provide a good measure of compressional and shear velocities, values that are required for calibrating seismic data at wells and for the investigation of lithology and fluid content from seismic data. Of course, the interpreter must be careful to know if the data represent invaded or uninvaded conditions and make appropriate corrections if necessary. Modern sonic logging tools can often provide reliable values for velocities through casing; often, the most-reliable sonic logs in soft shales can only be found behind casing because of the inability to log openhole the depth intervals in which shales are flowing or collapsing.

Compressional sonic log values are used in reservoir geophysics to tie well depths to seismic two-way travel time. First the sonic transit time is integrated to obtain a depth-calibrated time scale, then synthetic seismograms are created through determination of reflection coefficients (including the density log) and convolution with a known or assumed wavelet. This synthetic seismogram is often adjusted to account for:

  • Borehole effects
  • Absence of data in the shallowest section
  • Other unspecified effects, including velocity dispersion caused by thin-bed layering below seismic resolution

The shear sonic log values are then added to create synthetic seismograms that demonstrate AVO behavior for comparison with the prestack data near the well. Often, additional work is conducted to model the changes in seismic response when rocks of slightly different lithology or fluid saturation are encountered away from the well. Both the compressional and shear sonic data are required to accomplish fluid-substitution modeling, although some empirical models and other short-cuts are available.[1] The most common fluid substitution models employ Gassmann[2] in clastic rocks; a number of models also exists for fractured rocks.[3]

Single well imaging

Single-well imaging, although not yet widespread, may provide a useful tool for detailed close-up structural studies, such as salt-proximity studies designed to assist in the planning of a development sidetrack from an exploration well, or in determining the location of interfaces with respect to a horizontal well. In general, a sonic-logging tool or a string of VSP receivers (geophones and/or hydrophones), coupled with a downhole seismic source, is lowered into the well, often using tubing-conveyed methods in highly deviated wells. The experiment then becomes similar to a surface reflection-seismic experiment, except that reflections may come from any direction around the well, not just from beneath it. The technique has been shown to be useful to image fractures[4] and to determine proximity to upper and lower interfaces in horizontal wells[5] as demonstrated in Fig. 1.

Multiple-well techniques

By placing a seismic source in one well and receivers in another well, a seismic velocity model between the two wells can be constructed using tomographic techniques, and a reflection image can be obtained by processing the reflected arrivals.[6] Although the images are constrained to lie in a plane connecting the two wells, the additional fine-scale information, available from such surveys,[7] can be of significant value to the reservoir engineer (Fig. 2).

Well-to-surface techniques

Methods of calibrating seismic data and imaging that involve sources and/or receivers in one well and others at the surface include checkshot surveys, VSP, reverse VSP, and seismic-while-drilling. Checkshots and VSPs were developed primarily to assist in the tie between surface seismic data and well observations, but they have been extended beyond that in many cases. VSPs provide the best data for detailed event identification and wavelet determination, but they can also be used to image the near-wellbore environment, and the image can be improved if a number of offsets and azimuths (for a 3D VSP) are used for the source location. The ability to create a 3D image from borehole methods is greatly enhanced by placing a seismic source[8][9] in one well and deploying surface receivers, which are already around the well, in a reverse VSP configuration. Images from such experiments can be highly detailed[10] (see Fig. 3), and the time required for 3D reverse VSP acquisition is significantly reduced over the 3D VSP case in which the source is moved around the surface.

The drill bit can also be used as a seismic source[11] much like an uncontrolled, but monitored, vibrator; it is capable of providing, in at least some instances, information useful for selecting casing or coring points and for estimating proximity to overpressure zones.[12][13] Through the use of receivers in a logging-while-drilling unit near the bit, a surface VSP source can be recorded during pauses in the drilling operation, which occur as a new joint of pipe is being added.[14]

References

  1. Mavko, G., Chan, C., and Mukerji, T. 1995. Fluid Substitution: Estimating Change in Vp Without Knowing Vs. Geophysics 60 (6): 1750. http://dx.doi.org/10.1190/1.1443908
  2. Gassmann, F. 1951. Uber die Elastizitat poroser Medien, Vier. Der Natur. Gesellshaft in Zurich 96: 1–23.
  3. Mavko, G., Mukerji, T., and Dvorkin, J. 1998. The Rock Physics Handbook: Tools for Seismic Analysis in Porous Media, 329. Cambridge, UK: Cambridge University Press.
  4. Hornby, B.E. et al. 1992. Reservoir Sonics: A North Sea Case Study. Geophysics 57 (1): 146–160. http://dx.doi.org/10.1190/1.1443178
  5. 5.0 5.1 Yamamoto, H., Watanabe, S., Koelman, J.M.V. et al. 2000. Borehole Acoustic Reflection Survey Experiments in Horizontal Wells for Accurate Well Positioning. Presented at the SPE/CIM International Conference on Horizontal Well Technology, Calgary, Alberta, Canada, 6-8 November 2000. SPE-65538-MS. http://dx.doi.org/10.2118/65538-MS.
  6. Lazaratos, S.K. et al. 1995. High-Resolution Crosswell Imaging of a West Texas Carbonate Reservoir: Part 4, Reflection Imaging. Geophysics 60 (3): 702. http://dx.doi.org/10.1190/1.1443809
  7. 7.0 7.1 Harris, J.M. et al. 1995. High-Resolution Crosswell Imaging of a West Texas Carbonate Reservoir: Part 1, Project Summary and Interpretation. Geophysics 60 (3): 667. http://dx.doi.org/10.1190/1.1443806
  8. Paulsson, B., Fairborn, J., and Fuller, B. 1997. Single Well Seismic Imaging and Reverse VSP Applications for the Downhole Seismic Vibrator. Paper 2029 presented at the 1997 Society of Exploration Geophysicists Annual Intl. Meeting, Dallas, 2–7 November.
  9. Daley, T.M. and Cox, D. 2001. Orbital Vibrator Seismic Source for Simultaneous P- and S-Wave Crosswell Acquisition. Geophysics 66 (5): 1471. http://dx.doi.org/10.1190/1.1487092
  10. 10.0 10.1 Turpening, R. et al. 2000. Imaging with Reverse Vertical Profiles Using a Downhole Hydraulic Axial Vibrator. Paper presented at the 2000 Society of Exploration Geophysicists Intl. Exposition and Annual Meeting, Calgary, 6–11 August.
  11. Rector, J.W. III and Marion, B.P. 1991. The Use of Drill-Bit Energy as a Downhole Seismic Source. Geophysics 56 (5): 628. http://dx.doi.org/10.1190/1.1443079
  12. Miranda, F. et al. 1996. Impact of Seismic ‘While Drilling’ Technique on Exploration Wells. First Break 14 (2): 55. http://dx.doi.org/10.3997/1365-2397.1996004
  13. Kulkarni, R., Meyer, J.H., and Sixta, D. 1999. Are Pore-Pressure Related Drilling Problems Predictable? The Value of Using Seismic Before and while Drilling. Paper presented at the 1999 Society of Exploration Geophysicists Intl. Exposition and Annual Meeting, Houston, 31 October–5 November.
  14. Underhill, W., Esmersoy, C., Hawthorn, A. et al. 2001. Demonstrations of Real-Time Borehole Seismic From an LWD Tool. Presented at the SPE Annual Technical Conference and Exhibition, New Orleans, Louisiana, 30 September-3 October 2001. SPE-71365-MS. http://dx.doi.org/10.2118/71365-MS.

Noteworthy papers in OnePetro

Baker, L.J. and Hurris, J.M. Cross-Borehole Seismic Imaging. Presented at the 1984/1/1/.

Dobecki, T.L. Hydraulic Fracture Orientation Using Passive Borehole Seismics. Presented at the 1983/1/1/. http://dx.doi.org/10.2118/12110-MS.

Justice, J.H. Borehole Seismic Technology For Reservoir Imaging. Presented at the 1993/1/1/. http://dx.doi.org/10.4043/7080-MS.

Kramer, D. Multicomponent Multioffset VSP Processing. Presented at the 1991/1/1/.

Washbourne, J.K., Bube, K.P., Antonelli, M. et al. Crosswell Reflection Tomography. Presented at the 2002/1/1/.

External links

Use this section to provide links to relevant material on websites other than PetroWiki and OnePetro

See also

Reservoir geophysics overview

Seismic imaging and inversion

Seismic time-lapse reservoir monitoring

Passive seismic monitoring

Hydraulic fracture monitoring

Pore pressure prediction using seismic

Pore fluid effects on rock mechanics

PEH:Reservoir_Geophysics

Category