Casing mounted EM transducers having a soft magnetic layer

摘要

Illustrative permanent electromagnetic (EM) monitoring systems and methods have a casing string positioned inside a borehole and equipped with one or more EM transducer modules having a layer of soft magnetic material that substantially encircles the casing string to amplify a signal response of a magnetic field transmitting and/or sensing element. The layer preferably has an axial dimension at least twice an axial dimension of the magnetic field sensing element, with a relative permeability at least twice that of the casing material. The magnetic field transmitting element can be a coil. The magnetic field sensing element can be a coil or a piezoelectric or magnetostrictive element that applies stress to an optical fiber. A well interface system communicates with the one or more EM transducer modules to transmit and/or collect EM signals over time. Additional casing strings may be provided in other nearby boreholes to enable tomographic mapping and monitoring of fluid interfaces in the reservoir.

主权项

1. A permanent electromagnetic (EM) monitoring system that comprises:
a casing string installed inside a borehole, the casing string having at least one EM transducer module that includes:
a wire coil that encircles the casing string; anda layer of soft magnetic material between the coil and the casing string; and a well interface system coupled to the at least one EM transducer module to periodically transmit and/or collect EM signals in order to monitor at least one parameter of the subsurface formation over time.