Electromagnetic Tool for High-Resolution Logging: Theoretical and Experimental Studies
Authors: Epov M. I. , Glinskikh V. N. , Eremin V. N. , Nikitenko M. N. , Petrov A. N. , Mikhaylov I. V. 
Published: October 2017

The presented work is devoted to development of new electromagnetic methods of geophysical logging in oil and gas wells. The aim of the work is the development of an electromagnetic tool designed to study electrophysical parameters of sedimentary rocks characterized by macroanisotropic properties. Based on new theoretical and engineering ideas, we have proposed, designed and developed an electromagnetic tool with a high spatial resolution. The main problems to be solved are related to the substantiation and creation of the sonde, as well as the study of its capabilities on the basis of large-scale mathematical simulation and experimental research.

To study the anisotropic properties of thin-bedded terrigenous reservoirs, an alternative method to multicomponent induction tools, based on a new ‘excitation-observation’ system using a source in the form of a circular magnetic current, is proposed. With its application, an electromagnetic field is excited in the borehole environment, depending both on the vertical and horizontal resistivity. We designed and developed an electromagnetic tool which uses sets of transmitting and receiver coils, operating at several frequencies and realizing a number of operating modes. To substantiate the optimal configuration, realistic simulation was carried out, taking into account finite dimensions on the basis of the finite-difference and finite-element methods. Cmprehensive testing on laboratory stands and in real borehole conditions was performed.

We developed complexes of algorithms and computer programs for the analysis of signals of the new electromagnetic logging tool in spatially inhomogeneous media. The measured electromagnetic signals and their sensitivity functions to electrophysical parameters of the models are studied, and conclusions about the spatial resolution of the tool are drawn. An approach to the valid choice of the tool's parameters, including its lengths, operating frequencies, as well as the types of signals measured and modes of operation. The results obtained made it possible to choose the optimal configuration of the sonde system. Large-scale mathematical simulation of the signals of the multi-coil multi-frequency multi-mode electromagnetic probe was carried out. We performed a complex analysis of signals of the electromagnetic tool in typical models of oil and gas reservoirs, taking into account a realistic description of the sonde system. The work on the development of the new electromagnetic tool was started with the creation of its laboratory model. The results of creating the laboratory model are presented. A comparative analysis of the results of mathematical simulation and physical modeling using the laboratory model of the tool was made. We provide examples of the test results obtained in a metrological tank with electrolyte, as well as in natural and artificial freshwater reservoirs. A prototype of the electromagnetic tool was designed and created, with further testing of the prototype and its main components on laboratory test facilities and in conditions close to those in boreholes. In conclusion, we present the results of successful pilot testing.

The theoretical and practical significance of the presented work is determined by the creation of a new method for electromagnetic logging of oil and gas wells. In this direction, there have been only theoretical studies and no practical implementation. The developed tool is protected by 6 patents. The results of the studies at hand are presented publicly and in print for the first time.