6 July 2000 Analysis and optimization of NMR sensor for oilfield exploration applications
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Abstract
Nuclear magnetic resonance (NMR) measurements have become an important part of oilfield well-logging to identify and quantify oil and gas reservoirs. In this paper, some design aspects of NMR sensor for well-logging applications are discussed. The RF and static magnetic fields are computed using a 3D finite element method (FEM). A perturbation technique along with FEM is used to evaluate the power loss in conductors that avoids the need for small discretization steps along the conductor thickness. The magnet is built by stacking several magnet segments along the axial direction and the objective is to magnetize and shape these segments in such a way so as to produce a desired field profile in front of the magnet. An optimal control technique is used in conjunction with the FEM to speed up the design process with signal-to-noise ratio, frequency of operations, depth of investigation, and prepolarization time being the optimization constraints. Very good agreement between the measured and computed antenna efficiency and magnetic field is obtained thus validating the numerical model.
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Jaideva C. Goswami, Bruno Luong, "Analysis and optimization of NMR sensor for oilfield exploration applications", Proc. SPIE 4129, Subsurface Sensing Technologies and Applications II, (6 July 2000); doi: 10.1117/12.390616; https://doi.org/10.1117/12.390616
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KEYWORDS
Magnetism

Finite element methods

Antennas

Sensors

Signal to noise ratio

Signal processing

Electronic circuits

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