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On the possibility of inversion in borehole seismic modifications

UDK: 550.834:26.21
DOI: 10.24887/0028-2448-2019-6-28-32
Key words: borehole seismic, data inversion, elastic impedance, forecast under bottomhole
Authors: V.A. Lensky (SPC Geostra LLC, RF, Ufa), A.S. Zhuzhel (Bashneftegeofizika JSC, RF, Ufa), W.G. Umetbaev (Ufa State Petroleum Technological University, RF, Ufa)

There is almost universally a demand for data inversion, both to data from borehole seismic and by analogy with land seismic. In this paper we have considered the feasibility of inversion in the main modifications of the borehole seismic. In case of zero-offset VSP, inversion can be performed to predict the geological section below the bottomhole. The solution of the problem requires the highly skilled performer. It is also possible only if there is data from acoustic and density logging in the drilled part and brute information about the structure of the environment under the bottomhole. The offset VSP modification refers to use methods of full-fold data inversion known in the 2D seimic, but the task is not correct due to large incidence angles varying in a wide range and changes in the recording environment, the effect of which on the wave field far exceeds the effect of changes in the properties of formations. The reliability of the results is, at best, limited to a small near-wellbore zone, which has no practical significance. Modifications of walkaway VSP and VSP-3D are multiple observation systems, but, unlike land seismic, the use of inversion of sums partial multiples is impossible, since the vast majority of space cells correspond to a narrow range of stack angles. The use of inversion of full-fold stacks is also incorrect due to changes in the angles of incidence and the complexity of taking into account the changes in the structure of the upper part of the section. Thus, the inversion of offset VSP, walkaway VSP and VSP-3D data is hardly appropriate.

Reference

1. Ampilov Yu.P., Barkov A.Yu., Yakovlev I.V. et al., Almost everything about the seismic inversion. Part 1 (In Russ.), Tekhnologii seysmorazvedki, 2009, no. 4, pp. 3–16.

2. Zhuzhel' A.S., Lenskiy V.A., Irkabaev D.R., Sharova T.N., The choice of modification of borehole seismic exploration in the study of near wellbore space (In Russ.), Burenie i neft', 2018, no. 9, pp. 56–61.

3. Tabakov A.A., Rakhimov R.G., Shamsiev M.G., Method of predicting the section below the bottomhole of an exploration well according to VSP using the method of solving inverse dynamic problems (In Russ.), Collected papers “Geofizicheskie issledovaniya na neft' i gaz v Uzbekistane” (Geophysical surveys on oil and gas in Uzbekistan), 1977, V. 27, pp. 98–100.

4. German V.A., Algoritm obrabotki materialov skvazhinnykh nablyudeniy po metodike dinamicheskogo seysmicheskogo zondirovaniya (Algorithm for processing well observations data by the method of dynamic seismic sounding), Collected papers “Novye rezul'taty geofizicheskikh issledovaniy v Belorussii” (New results of geophysical studies in Belarus), 1986, pp. 94–100.

5. Conn P.J. and Nelson C.M., Prediction of formation depths and velocities from VSP data using a linear calibration method, Proceedings of SPWLA 26th Annual Logging Symposium, Dallas, Texas, 17–20 June.

6. Mace D., Lailly P., Solution of the VSP one-dimensional invers problem, Geophysical Prospecting, 1986, V. 34, no. 7, pp. 1002–1021.

7. Lenskiy V.A., Prognozirovanie zon AVPD po dannym VSP (Prediction of abnormally high formation pressure zones according to VSP data), Collected papers “Novye metody, sistemy obrabotki i interpretatsii seysmorazvedochnoy informatsii na EVM” (New methods, systems for computer processing and interpretation of seismic data): edited by Dyadyura V.A., Proceedings of workshop of Assotsiatsiya razrabotchikov i pol'zovateley komp'yuternykh tekhnologiy integrirovannoy obrabotki i interpretatsii geologo-geofizicheskikh dannykh, Tyumen', 7–12 October 1991, Moscow: Publ. of Geoinformmark, 1991, Part 1, pp. 109–114.

8. Silvia M.T., Robinson E.A., Deconvolution of geophysical time series in the exploration for oil and natural gas, Elsevier Science, 1979, 275 p.

9. Aleksandrov B.L., Anomal'no vysokie plastovye davleniya v neftegazonosnykh basseynakh (Abnormally high reservoir pressures in oil and gas basins), Moscow: Nedra Publ., 1987, 216 p.

There is almost universally a demand for data inversion, both to data from borehole seismic and by analogy with land seismic. In this paper we have considered the feasibility of inversion in the main modifications of the borehole seismic. In case of zero-offset VSP, inversion can be performed to predict the geological section below the bottomhole. The solution of the problem requires the highly skilled performer. It is also possible only if there is data from acoustic and density logging in the drilled part and brute information about the structure of the environment under the bottomhole. The offset VSP modification refers to use methods of full-fold data inversion known in the 2D seimic, but the task is not correct due to large incidence angles varying in a wide range and changes in the recording environment, the effect of which on the wave field far exceeds the effect of changes in the properties of formations. The reliability of the results is, at best, limited to a small near-wellbore zone, which has no practical significance. Modifications of walkaway VSP and VSP-3D are multiple observation systems, but, unlike land seismic, the use of inversion of sums partial multiples is impossible, since the vast majority of space cells correspond to a narrow range of stack angles. The use of inversion of full-fold stacks is also incorrect due to changes in the angles of incidence and the complexity of taking into account the changes in the structure of the upper part of the section. Thus, the inversion of offset VSP, walkaway VSP and VSP-3D data is hardly appropriate.

Reference

1. Ampilov Yu.P., Barkov A.Yu., Yakovlev I.V. et al., Almost everything about the seismic inversion. Part 1 (In Russ.), Tekhnologii seysmorazvedki, 2009, no. 4, pp. 3–16.

2. Zhuzhel' A.S., Lenskiy V.A., Irkabaev D.R., Sharova T.N., The choice of modification of borehole seismic exploration in the study of near wellbore space (In Russ.), Burenie i neft', 2018, no. 9, pp. 56–61.

3. Tabakov A.A., Rakhimov R.G., Shamsiev M.G., Method of predicting the section below the bottomhole of an exploration well according to VSP using the method of solving inverse dynamic problems (In Russ.), Collected papers “Geofizicheskie issledovaniya na neft' i gaz v Uzbekistane” (Geophysical surveys on oil and gas in Uzbekistan), 1977, V. 27, pp. 98–100.

4. German V.A., Algoritm obrabotki materialov skvazhinnykh nablyudeniy po metodike dinamicheskogo seysmicheskogo zondirovaniya (Algorithm for processing well observations data by the method of dynamic seismic sounding), Collected papers “Novye rezul'taty geofizicheskikh issledovaniy v Belorussii” (New results of geophysical studies in Belarus), 1986, pp. 94–100.

5. Conn P.J. and Nelson C.M., Prediction of formation depths and velocities from VSP data using a linear calibration method, Proceedings of SPWLA 26th Annual Logging Symposium, Dallas, Texas, 17–20 June.

6. Mace D., Lailly P., Solution of the VSP one-dimensional invers problem, Geophysical Prospecting, 1986, V. 34, no. 7, pp. 1002–1021.

7. Lenskiy V.A., Prognozirovanie zon AVPD po dannym VSP (Prediction of abnormally high formation pressure zones according to VSP data), Collected papers “Novye metody, sistemy obrabotki i interpretatsii seysmorazvedochnoy informatsii na EVM” (New methods, systems for computer processing and interpretation of seismic data): edited by Dyadyura V.A., Proceedings of workshop of Assotsiatsiya razrabotchikov i pol'zovateley komp'yuternykh tekhnologiy integrirovannoy obrabotki i interpretatsii geologo-geofizicheskikh dannykh, Tyumen', 7–12 October 1991, Moscow: Publ. of Geoinformmark, 1991, Part 1, pp. 109–114.

8. Silvia M.T., Robinson E.A., Deconvolution of geophysical time series in the exploration for oil and natural gas, Elsevier Science, 1979, 275 p.

9. Aleksandrov B.L., Anomal'no vysokie plastovye davleniya v neftegazonosnykh basseynakh (Abnormally high reservoir pressures in oil and gas basins), Moscow: Nedra Publ., 1987, 216 p.



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