Abstract
The propagation of electromagnetic waves in the annular region of oil wells was studied. The present study aims to analyse the propagation attenuation along the well, as well as the input impedance determined by a source placed near the wellhead. A coaxial waveguide model was adopted with heterogeneous dielectrics and losses. First, a wave equation solution for the waveguide is presented, assuming a homogeneous medium with losses, by solving the equation in cylindrical coordinates using the vector potential technique. An uncertainty analysis model is then developed to model the heterogeneous characteristics of the medium. Monte Carlo simulations were performed with the created model using data gathered from the literature. The results of the simulations indicate that propagation in the transverse electromagnetic mode has the smallest attenuation and that for depths of up to 4000 m, there is an attenuation of less than 52 dB. Furthermore, the input impedance ranges from 10 Ω to 10 kΩ because of the uncertainties involved in the problem in question.
Highlights
Oil wells today are extremely complex and demand very expensive maintenance [1]
The present study aims to analyse the propagation attenuation along the well, as well as the input impedance determined by a source placed near the wellhead
The input impedance ranges from 10 Ω to 10 kΩ because of the uncertainties involved in the problem in question
Summary
Oil wells today are extremely complex and demand very expensive maintenance [1]. Modern drilling techniques can reach a few kilometres in depth, and the costs of a floating platform at open sea can cost billions of Brazilian Reais. One possibility would be the use of signal transmission techniques using a magnetic field [3] In this method, a coil that is capable of inducing alternating current through the production pipe is used. For long distances, on the order of 3000 m or more, the method is unfeasible Another possible approach would be to analyse the oil well from the perspective of a coaxial propagation structure, which is formed by a conductor tube with a perfect centre (production tube) and a cylindrical shell that is coaxial with the tube and is a perfect conductor. Approach makes it possible to conduct the analysis as it would be performed on a coaxial cable, and propagation occurs in the transverse electromagnetic mode [6] This approach, has been studied without considering fluids of significant conductivity or possible uncertainties caused by temperature and electrical parameter variations of the fluid that fills the well. The study uses Monte Carlo analysis to illustrate how the propagation attenuation behaves and to analyse the input impedance of the coaxial waveguide as a function of position
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