Institute of Computational Mathematics and Mathematical Geophysics SB RAS

International Conference on Mathematical Methods in Geophysics «MMG-2008»

Akademgorodok, Novosibirsk, Russia, October 13-15, 2008

Abstracts

Mathematical Simulation in Geophysical Problems. Electromagnetic Methods

Inversion of logs acquired with VIKIZ and BKZ probes based on 2D mathematical simulation

Nesterova G.V., Surodina I.V.

IPGG SB RAS (Novosibirsk),
ICM&MG SB RAS

Inversion of logs acquired with VIKIZ and BKZ probes based on 2D mathematical simulation In conventional practice of inversion of electrical and electromagnetic measurements in boreholes, a 1D model of the radial resistivity distribution is used. The formation is divided into horizontal layers in the vertical direction and into several cylindrical zones in the horizontal direction. These cylindrical layers are treated as a borehole, invaded zone, bordering zone, and formation. One-dimensional simulation of readings acquired with probes of both high-frequency induction logging isoparametric sounding (VIKIZ in Russian abbreviation) and laterologging (BKZ in Russian abbreviation) has been well established and it is used for solution of inverse problems and can be used in automatic mode as well (MFS-VIKIZ, Select, EMF PRO). When the formation is represented by such a way and 1D simulation of responses of both direct current (laterologging) probes and alternating current (VIKIZ) ones is applied, a variety of equivalence models arises. Narrowing the equivalency domain is attained by different ways: involving a priory data, combination of different methods (joint inversion including the inversion based on joint hydrodynamic and geoelectric models), as well as using more complicated models (two- and three-dimensional) for responses of probes. In the process of development and creation of software-algorithmic means for simulation of two- and three-dimensional geoelectric problems, one is forced to select in favor of one of three possible procedures for creation of software product. As it is known, simulation of electromagnetic fields is implemented by using the method of integral equations, the method of finite elements or finite-difference algorithms. Each of these approaches has its own advantages and some drawbacks. In connection with the necessity for creation of program packages for simulation of laterolog and VIKIZ logs just as in quasi-three- dimensional and three-dimensional isotropic models, so in quasi- three-dimensional and three-dimensional anisotropic models, the decision has been made in favor of finite-difference methods of calculation. It can be explained by the fact that going from isotropic models to anisotropic ones is comparative simple In the report, the description of mathematical and numerical two-dimensional simulation of VIKIZ and laterolog probe readings, applying this simulation for interpretation of measurements acquired in boreholes of the Kogalym and Russinsk fields are given.

Note. Abstracts are published in author's edition

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