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Electromagnetic response of electrically conductive pipelines and well casings: algorithms and experimental validation, The

Orujov, Gurban
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Abstract
Controlled-source electromagnetics (CSEM) can be used for subsurface resistivity imaging and add value in petroleum exploration and reservoir monitoring. The existence of long and thin, but highly conductive metal infrastructure creates a major challenge for the application of CSEM methods due to current channeling effects and subsequent distortion of the signal from subsurface. In this thesis, I develop a methodology for modeling the electromagnetic (EM) response of steel casings and pipelines. I validate the developed methodology with small, medium, and large-scale experiments. First, I develop a methodology for modeling the EM response of complex steel infrastructure using the Method of Moments (MoM) approach. I validate the developed algorithm with numerical examples and small-scale experiments. I demonstrate the efficiency of the algorithm on the example of a long horizontal submarine pipeline. Next, I analyze the effect of steel casings on surface-to-surface time-lapse EM measurements. I use thin resistive sheet approximation to model the EM response of a hydrocarbon reservoir. Then, I apply the MoM algorithm to simulate scenarios with a single and multiple casings. Numerical results show that the steel infrastructure effects on surface electric fields are significant and therefore can not be ignored. Finally, I invert two CSEM datasets, which I purposefully collected over two different vertical steel casings for the validation of hybrid 3D finite volume – MoM algorithm. I show that the casing artifacts in recovered resistivity models are reduced significantly through the introduction of casing physics into the forward model, allowing the surrounding subsurface conductivity and corresponding geology to be characterized.
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