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System VSP-3D to refine the geological structure of the borehole environment

UDK: 550.834
DOI: 10.24887/0028-2448-2018-9-82-87
Key words: observation systems, three-dimensional vertical seismic profiling (VSP-3D), study of near-well space
Authors: V.A. Lensky (SPC Geostra LLC, RF, Ufa), A.J. Adiev (SPC Geostra LLC, RF, Ufa), D.R. Irkabaev (Bashneftegeofizika JSC, RF, Ufa), A.S. Zhuzhel (Bashneftegeofizika JSC, RF, Ufa)

Currently, there is an increased interest in VSP-3D when detailing the structure of hydrocarbon traps in the near-well space. The article provides a justification for the most optimal variants of VSP-3D observation systems and a method of calculating their parameters, the multiplicity of tracking and the size of the illuminated area depending on the required density of observations, the depth of the installation and the length of the used borehole equipment. It is necessary to distinguish between two modifications of 3D borehole seismic with different requirements for observations: VSP-3D observations for the purpose of studying the geological structure of the near-well space and combined observations of CDP-3D and VSP focused on the implementation of the tasks of CDP-3D. The choice of VSP-3D observation system for studying the near-wellbore space is determined by the length of the used well probe. With a short probe (several dozens of receiving modules), the optimal placement of sources on a square grid on the area in the form of a circle, which ensures the preservation of the multiplicity of tracking and the reduction of the maximum removal of the source, but is expensive. When using a long equipment, covering the wellbore to the bottom, preferably the placement of sources in a circle, the multiplicity of tracking in this case is uneven and quickly decreases with the distance from the well. Combined observations are more cheaper, but cause the appearance of unlit areas and do not provide high-quality cube VSP-3D data, so cannot be recommended for detailing the geological structure of the near-well space. Practical examples are given.

References

1. Shekhtman G.A., Area modification of the VSP method (In Russ.), Geofizika, 1996, no. 1, pp. 23–28.

2. Shekhtman G.A., Zernov A.E., Potapov O.A., Lebedeva I.I., Sokolova K.B., Areal modification of the VSP method, Proceedings of 55th Annual Meeting of EAGE, 1993, Stavanger.

3. Baranov K.V., Bikeev V.S., Starikov N.V., Tabakov A.A., Results for applying the 3D + VSP local project and 2D + VSP local project in Western Siberia (In Russ.), Tekhnologii seysmorazvedki, 2004, no. 1, pp. 19-22.

4. Tabakov A.A., Baranov K.V., Rykovskaya N.V., Kopchikov A.V., Techniques and some results of walkaway and 3D VSP data processing (In Russ.), Tekhnologii seysmorazvedki, 2006, no. 2, pp. 8–13.

5. Andersen J., Bartling B., Nelson H.R.Jr., Borehole seismic defines reservoirs at point of extraction, Oil & Gas Journal, 2014, June, pp. 50–57.

6. Irkabaev D.R., Atnabaev R.F., Lenskiy V.A., Yakupov M.T., Complex seismic technologies VSP-2D, VSP-3D,VSP-CDP (In Russ.), Geofizika, 2017, no. 3, pp. 24–28.В 

Currently, there is an increased interest in VSP-3D when detailing the structure of hydrocarbon traps in the near-well space. The article provides a justification for the most optimal variants of VSP-3D observation systems and a method of calculating their parameters, the multiplicity of tracking and the size of the illuminated area depending on the required density of observations, the depth of the installation and the length of the used borehole equipment. It is necessary to distinguish between two modifications of 3D borehole seismic with different requirements for observations: VSP-3D observations for the purpose of studying the geological structure of the near-well space and combined observations of CDP-3D and VSP focused on the implementation of the tasks of CDP-3D. The choice of VSP-3D observation system for studying the near-wellbore space is determined by the length of the used well probe. With a short probe (several dozens of receiving modules), the optimal placement of sources on a square grid on the area in the form of a circle, which ensures the preservation of the multiplicity of tracking and the reduction of the maximum removal of the source, but is expensive. When using a long equipment, covering the wellbore to the bottom, preferably the placement of sources in a circle, the multiplicity of tracking in this case is uneven and quickly decreases with the distance from the well. Combined observations are more cheaper, but cause the appearance of unlit areas and do not provide high-quality cube VSP-3D data, so cannot be recommended for detailing the geological structure of the near-well space. Practical examples are given.

References

1. Shekhtman G.A., Area modification of the VSP method (In Russ.), Geofizika, 1996, no. 1, pp. 23–28.

2. Shekhtman G.A., Zernov A.E., Potapov O.A., Lebedeva I.I., Sokolova K.B., Areal modification of the VSP method, Proceedings of 55th Annual Meeting of EAGE, 1993, Stavanger.

3. Baranov K.V., Bikeev V.S., Starikov N.V., Tabakov A.A., Results for applying the 3D + VSP local project and 2D + VSP local project in Western Siberia (In Russ.), Tekhnologii seysmorazvedki, 2004, no. 1, pp. 19-22.

4. Tabakov A.A., Baranov K.V., Rykovskaya N.V., Kopchikov A.V., Techniques and some results of walkaway and 3D VSP data processing (In Russ.), Tekhnologii seysmorazvedki, 2006, no. 2, pp. 8–13.

5. Andersen J., Bartling B., Nelson H.R.Jr., Borehole seismic defines reservoirs at point of extraction, Oil & Gas Journal, 2014, June, pp. 50–57.

6. Irkabaev D.R., Atnabaev R.F., Lenskiy V.A., Yakupov M.T., Complex seismic technologies VSP-2D, VSP-3D,VSP-CDP (In Russ.), Geofizika, 2017, no. 3, pp. 24–28.В 



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