LAUSR

Metallic well casings strongly impact electromagnetic fields due to their high electrical conductivity. We can take advantage of their presence and increase the sensitivity of EM signals to deeper subsurface structure by driving electric currents down through existing casings, or using the metal as a wave guide for EM telemetry. Interpretation of such well-casing-enhanced measurements requires accurate simulation of these setups. The Method of Moments (MoM) can be used for modelling well casings without having to discretise them finely as part of the subsurface model. Extending the MoM for EM sources directly connected to well casings is straightforward in principle. However, we find that the accuracy of MoM results for such configurations depends strongly on details of the computational model definition, such as the exact position of the connection point and the discretisation of the source wire. We explain those important details and provide strategies for the most accurate MoM modelling of electric currents injected into well casings.