Electrical and electromagnetic responses over steel-cased wells

Abstract

Electrical and electromagnetic (EM) methods can be diagnostic geophysical imaging tools for monitoring applications, such as carbon capture and storage or hydraulic fracturing. In these settings, it is common that steel-cased wells and other steel infrastructure are present. Grounded source methods, which use electrodes to inject current into the earth, are of interest for casing integrity and monitoring applications. Electrostatic, or direct current (DC) resistivity, experiments form the basis of our understanding of the physics of grounded source experiments in terms of charges, currents, and electric fields. Steel-cased wells are highly conductive, and although their presence makes numerical modeling more challenging, they can help targets of interest be detected because they channel charges and currents to depth. Time-domain EM experiments use a time-varying transmitter current. Understanding the EM response requires that we consider both galvanic, or DC, currents as well as image currents that are induced in the subsurface. As compared to DC experiments, the physics of EM is more complex because of the multiple current systems as well as the need to consider magnetic permeability of steel-cased wells. However, EM experiments have the advantage that they can provide a large data set that is sensitive to a target of interest. Ultimately, this will increase the potential for being able to extract information about the target.

Electromagnetic imaging and deep learning for transition to renewable energies: a technology review

“…The study of EM measurements in the presence of metallic infrastructures (telephone networks, pipelines, railways, industrial facilities, and wells, among others) is of particular interest because the target areas are usually urbanized. Although numerically challenging, several studies have been performed in this regard, revealing a direct relationship between the presence of metallic artifacts and signal-to-noise ratio in EM responses (Um et al, 2015;Vilamajó et al, 2015;Wilt et al, 2020;Castillo-Reyes et al, 2021;Heagy and Oldenburg, 2022). The aforementioned authors remark on the importance of studying this behavior to avoid the misinterpretation of EM maps.…”

A Feasibility Study of Land CSEM Surveys With a Near-Casing Source for Hydraulic Fracturing Monitoring

“…Although the impact of steel casings on EM signals is not a new issue in geophysics, conducting efficient 3D numerical simulations that account for steel casings remains a challenging problem. Among various studies, some researchers discretize steel casings at a millimeterscale grid resolution and employ numerical algorithms to achieve detailed simulations of arbitrarily complex 3D models at the cost of computational efficiency [12], [13], [14], [15]. However, the implementation of this method in complex steel-casing systems poses significant challenges.…”