An adaptable technique for comparative image assessment: Application to crosswell electromagnetic survey design for fluid monitoring

Abstract

Reservoir integrity stewardship accompanying carbon capture and sequestration considers reservoir fluid extraction and re-injection as a risk-mitigating method against reservoir overpressuring that could lead to caprock damage and ensuing CO2 leakage. Crosswell electromagnetics offers a technically viable monitoring method with the spatial volume coverage necessary for reservoir-encompassing pressure management. However, a certain logistical dilemma for deep gas sequestration into saline and thus electrically conductive aquifers is that crosswell magnetic-field measurements underperform in the imaging of more resistive plume bodies, further exacerbated when vertical arrays intersect, as opposed to surround, plumes. Comparative synthetic-data plume imaging of such scenarios rates the information content of magnetic-field versus electric-field 3D crosswell layouts for reservoir and infrastructure conditions of a representative pilot site in a coastal area in Florida. The image quality of the resulting plume replications can be ranked numerically through a newly proposed semblance qualifier, appraising the model goodness of fit to a given reference. In contrast to common least-squares measures for goodness of fit, the semblance formulation employs classifying logistic function types, thus enabling a better distinction of predefined anomaly features.

1DCSEMQWE: 1D Controlled Source Electromagnetic Method in Geophysics Using Quadrature With Extrapolation

“…The typical concept of marine CSEM is to deploy the receivers on the seafloor to obtain the electromagnetic signal emitted by a deep-towing electric transmitter [1]. On the other hand, a crosswell configuration, where both transmitter and receiver are located inside boreholes, has proved important in reservoir characterization and fluid monitoring [31,32]. For the latter configuration, it is more convenient to use the magnetic dipole source.…”