Three-dimensional scheme for single-well electromagnetic inversion

Yuri Nikolaevich Lazarev; Gregory Newman; Peter Vetalevich Petrov

doi:10.1117/12.450162

27 November 2001 Three-dimensional scheme for single-well electromagnetic inversion

Yuri Nikolaevich Lazarev, Gregory Newman, Peter Vetalevich Petrov

Proceedings Volume 4491, Subsurface and Surface Sensing Technologies and Applications III; (2001) https://doi.org/10.1117/12.450162
Event: International Symposium on Optical Science and Technology, 2001, San Diego, CA, United States

Abstract

A 3-D code has been designed to reconstruct the three-dimensional conductivity distribution in beds surrounding a wellbore from electromagnetic field data measured on the well axis. An arbitrarily oriented point magnetic dipole located on the well axis is considered as a source of electromagnetic radiation, where the well is parallel or normal to bed boundaries. In the specific case the solution to the vector Helmholtz equation for layered medium including the well and invasion zones is used to determine the background field E₀. The order/size of the finite-difference operator of Helmholtz equation for the secondary field E, which arises from the 3D properties of the geological medium that differ from the background medium, is reduced by the thinning method. Formal application of the method produces a set of equations that connect the measured secondary field values on the axis with the unknown conductivity model. A biconjugate gradient method and simple iterative updates on the conductivity model are used to find the solution to the thinned system of equations, where the solution to the equations for the conductivity perturbation is sought by traditional regularization functional minimization. Specific examples are presented, which illustrate the possibilities of the method. It is shown that the use of the thinning method allows for a significant reduction in computational expenditure, without appreciable loss in the quality of the conductivity reconstruction.

Citation Download Citation

Yuri Nikolaevich Lazarev, Gregory Newman, and Peter Vetalevich Petrov "Three-dimensional scheme for single-well electromagnetic inversion", Proc. SPIE 4491, Subsurface and Surface Sensing Technologies and Applications III, (27 November 2001); https://doi.org/10.1117/12.450162

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