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Title: Detection of hydrocarbons and their movement in a reservoir using time-lapse multichannel transient electromagnetic (MTEM) data
Author: Wright, David A.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2004
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Using two time-lapse surveys over an underground gas storage reservoir in St. Illiers la Ville, in France, I demonstrate the potential for multichannel transient electromagnetic (MTEM) data to detect the presence and movement of hydrocarbons in the earth through a new approach to the acquisition and processing of the data. I introduce a new pre-processing methodology for noise reduction and deconvolution of the system response to recover the impulse response of the earth. The thesis is divided into three parts: overview of electromagnetic methods, modelling, and processing of MTEM data. I carried out a comprehensive review of all electromagnetic (EM) methods in relation to hydrocarbon exploration. Of all these, the MTEM method provides the best resolution, detectability and spatial coverage of resistive targets. In the MTEM method a transient current is injected into the ground through a grounded dipole source and measurements of induced voltages at many receiver sites form the data for analysis. 1-D modelling indicates that the in-line component of the electric field is most sensitive to a buried resistor. The response of the cross-line component is about two orders of magnitude smaller, while the magnetic field is not sensitive to the resistor at all. Modelling the St. Illiers la Ville data shows that the response of the reservoir occurs between about 3 and 15ms, and at offsets greater than about 750m. I modelled in-line electric field data to test the application of a resistivity analysis using a seismic refraction analogy. The analysis was applied after transforming the data to a wave-like non-diffusive domain in log-time. The results indicate that the approach works only for a two-layer model and breaks down if the resistive layer is thin, typically less than a few hundred metres. The new MTEM data processing methodology includes improved noise reduction through the application of a dip filter, and deconvolution for the system response each time the source is fired. This enables the impulse response of the earth to be recovered. Processing of two MTEM datasets from St Iliers la Ville reveals both the presence of the gas in the reservoir and the movement of the gas between the two surveys.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available