Interpretation of near-field transient electromagnetic sounding data with the account of induction-induced polarization in areal exploration for oil and gas in the south of the Siberian craton

The main electrical prospecting technique in the study of the geological section of the Siberian platform sedimentary cover is a near-field transient electromagnetic method (TEM) used for oil and gas exploration along with seismic prospecting. In recent years more and more signals complicated by the effect of induction-induced polarization (IIP) are registered. Interpretation of such signals in the horizontally stratified conductive models leads to errors when defining the resistivity of the sedimentary cover horizons located in the target interval of the section. The aim of the study has been to define the IIP-complicated transient response registered during the areal exploration for oil and gas, as well as to develop guidelines for interpreting the TEM data with the account of the induced polarization (IP). Using mathematical modeling, the IP effect has been evaluated for the transient characteristics calculated by the model in which the polarized horizon is located at different depths. Based on the TEM data inversion results considering the IP, the effectiveness of methodology has been validated. According to the inversion results, the IP manifestation is associated with the rocks in the upper part of the section. The nature of IP is explained by the presence of pyrite in the Jurassic and Upper Cambrian sediments. The resistivity distribution for the target horizons with the account of IP is lognormal. Applying the parameter characterizing the TEM curve divergence at the qualitative analysis stage allows the area zoning by the degree of IIP manifestation. Interpretation of the TEM data with the account of IP enhances the accuracy of the TEM data inversion and allows to obtain the models that are consistent with the geological structure of the survey area. Thus, it enables a detailed forecast of the reservoir properties of the subsalt sediments.

TEM, induced polarization, Siberian craton

1. Pospeeva E.V., Pospeev V.I. Rezul'taty glubinnykh magnitotelluricheskikh issledovanii v Yakutskoi almazanosnoi provintsii [The results of deep magnetotelluric investigations in the Yakutsk diamond- bearing province]. Obespechenie nauchnotekhnicheskogo progressa pri geofizicheskikh issledovaniyakh v Vostochnoi Sibiri [Digest of articles. Support of scientific and technical progress in geophysical research in Eastern Siberia]. Irkutsk; Novosibirsk: Siberian Research Institute of Geology, Geophysics and Mineral Resources Publ., 1987, рр. 107–116. (In Russ.).

2. Antonov E.Yu., Kozhevnikov N.O., Kompaniets S.V. The manifestation of and allowing for the inductively induced polarization of the near-surface in Eastern Siberia. GEO-Sibir' [GEO-Siberia], 2011, vol. 2, no. 2, рр. 185–191. (In Russ.).

3. Kompaniets S.V., Kozhevnikov N.O., Antonov E.Yu. The manifestation of and allowing for the inductively induced polarization in TEM sounding studies of sedimentary cover in the south of Siberian platform. Geofizika [Russian Geophysics], 2013, no. 1, рр. 35–40. (In Russ.)

4. Stognii V.V., Korotkov Yu.V. Poisk kimberlitovykh tel metodom perekhodnykh protsessov [Exploration for kimberlite bodies by TEM]. Novosibirsk: Malotirazhnaya tipografiya 2D Publ., 2010, 121 р. (In Russ.).

5. Sharlov M.V., Agafonov Yu.A., Stefanenko S.M. Modern telemetric electromagnetic prospecting systems SGS-TEM and FastSnap. Efficiency and usage expertise. Pribory i sistemy razvedochnoi geofiziki [Devices and Systems of Exploration Geophysics], 2010, no. 1 (31), рр. 20–24. (In Russ.).

6. Pelton W.H., Ward S.H., Hallof P.G., Sill W.R., Nelson P.H. Mineral discrimination and removal of inductive coupling with multifrequency IP. Geophysics, 1978, vol. 43, рр. 588–609.

7. Kozhevnikov N.O., Antonov E.Yu. Impulseinductive electrical survey of polarizable medium. Geofizicheskii zhurnal [Geophysical Journal], 2009, vol. 31, no. 4, pp. 104–118. (In Russ.).

8. Guseinov R.G., Petrov A.V., Agafonov Yu.A., Sharlov M.V., Buddo I.V., Gomul'skii V.V. Quality control system for transient electromagnetic soundings. Vestnik Irkutskogo gosudarstvennogo tekhnicheskogo universiteta [Proceedings of Irkutsk State Technical University], 2015, no. 5 (100), pp. 53–60. (In Russ.).

9. Pospeev A.V., Buddo I.V., Agafonov Yu.A., Sharlov M.V., Kompaniets S.V., Tokareva O.V., Misyurkeeva N.V., Gomul'skii V.V., Surov L.V., Il'in A.I., Emel'yanov V.S., Murzina E.V., Guseinov R.G., Seminskii I.K., Sharlov R.V., Vakhromeev A.G., Sen' E.A. Sovremennaya prakticheskaya elektrorazvedka [Modern electrical survey practice]. Novosibirsk: Geo Publ., 2018, 231 р. (In Russ.).

10. Kompaniets S.V., Tokareva O.V., Pospeev A.V., Seminskii I.K. To possibility of using lateral logging data when building geoelectric models of Southern Siberian platform sedimentary cover. Vestnik Irkutskogo gosudarstvennogo tekhnicheskogo universiteta [Proceedings of Irkutsk State Technical University], 2014, no. 5 (88), рр. 53–57. (In Russ.).

11. Murzina E.V., Emel'yanov V.S., Pospeev A.V., Agafonov Yu.A. Podkhod k otsenke kachestva avtomaticheskoi inversii dannykh vysokoplotnykh elektromagnitnykh zondirovanii [Approach to assessing the quality of automatic inversion of high-density electromagnetic sounding data]. Tez. dokl. ХХVII Vseros. molodezhn. konf. “Stroenie litosfery i geodinamika” [Heads of reports, 27th AllRussian youth' conference “Lithosphere structure and geodynamics”]: Irkutsk: Institute of the Earth’s crust, SB RAS Publ., 2017, рр. 159–161. (In Russ.).

12. Kontorovich A.E., Surkov B.C., Trofimuk A.A. Geologiya nefti i gaza Sibirskoi platformy [Geology of oil and gas of the Siberian craton]. Moscow: Nedra Publ., 1981, 552 p. (In Russ.).

13. Shkirya M.S., Davydenko Yu.A. On the relationship between the presence of hydrocarbons and epigenetic sulfides in the south of Yakutia. Zapiski Gornogo instituta [Journal of Mining Institute], 2017, vol. 227, рр. 523–529. (In Russ.) https://doi.org/10.25515/PMI.2017.5.523.