Abstract Application of electromagnetic methods in regional investigations, prospecting and exploration for oil and gas deposits in the USSR greatly increases geological and economical effectiveness of geophysical surveys.
The theory and technique of new methods have been developed that are based on measurements of variable and transient, natural and artificial electromagnetic fields.
The technique for investigation of a horizontally non-uniform earth has been developed with the help of modelling.
A particular consideration is given to a complex use of different electromagnetic methods including resistivity measurements. D.C. methods, transients measurements and magnetotelluric surveys make a complex of electrical prospecting that, with a small amount of additional information, allows sufficiently reliable results concerning the structure of a given territory and its geoelectrical hydrogeological and facial characteristics to be obtained.
Depending upon the resistivity structure of the earth, local conditions and the objective of the investigations, the complex of electrical prospecting is applied in different combinations, with each method making its own contribution. Magnetotelluric soundings are made for control measurements needed for determination of a range of variation periods to be recorded in a telluric survey and magnetotelluric profiling as well as in studying the laws of variation of an average lateral resistivity of the Sediments.
Magnetotelluric profiling is employed in regional investigations for the purpose of studying variations of the total lateral conductivity of the Sediments and making structural maps of the area.
Telluric survey is generally used for locating major local structures.
D.C. methods serve to evaluate the resistivity structure and to explore the relief of a shallow (2-3 km) low-resistivity or high-resistivity control horizon. by A. M. ALEXEYEV, M. N. BERDICHEVSKY, I. A. BEZRUCK, V. I. FOMTNA, K. I. NICKI- TENKO, M. K. POLSHKOV, and L. L. VANJAN Ministry of Geology, U.S.S.R.
Résumé En l'URSS l'application des méthodes électromagnétiques au cours des investigations régionales, des recherches et de la prospection de gisements de pétrole et de gas naturel augmente sensiblement l'effectivité géologique et économique des travaux géophysiques. On a élaboré la théorie et la technique des nouvelles méthodes basées sur l'étude des champs électromagnétiques alternatifs et transitoires artificiels et naturels.
Grâce à la simulation on a créé la technique de l'investigation d'une coupe horizontale non homogène.
On attire l'attention à l'application de l'association de plusieurs méthodes de la prospection électrique y compris la méthode de résistivités. La méthode de courant continu, la transient méthode et l'investigation magnétotellurique se forment un ensemble unique