The UTEM 4 Borehole system is a new generation borehole EM system from Lamontagne Geophysics Ltd. The main new feature of the system is its ability to do simultaneous three-axis oriented down-hole UTEM measurements. Orientation of the EM sensor is achieved by the combined use of three-axis magnetometer and temperature compensated three-axis accelerometer. The digital data are preprocessed down the hole, compressed, and transmitted to the surface by means of a single fibre optical link at a rate of 100k samples simultaneously for each component. Magnetometer data, accelerometer based tilt sensor data, temperature, and system monitoring data are multiplexed with the three-component EM data.
The key performance numbers of the system are:
> 3400 m depth capability
> Very low deep hole system noise levels
Less than 40 pT/s transverse component repeatability
Less than 8 pT/s axial component repeatability
> Very high system gain fidelity for "on" time measurement use
Less than 0.05% late channel probe/receiver gain variation
The UTEM 4 BH system is composed of the UTEM 4 BH down-hole probe and the UTEM 4 BH Receiver. A field ready system would also include a BH UTEM winch, a winch motor controller, one or more fibre optic cable spools, inter-connecting cables, and wire laying accessories which are unchanged from those used in the BH UTEM 3 system. The UTEM 4 BH down-hole probe has a maximum diameter of 38 mm for use in holes of AQ and greater diameter. The UTEM 4 BH data reduction and display software includes 3-axis data reduction oriented relative to a user specified section. Magnetometer, inclinometer and temperature data profiles can be plotted in addition to the EM data. Software is available for interactive 3D viewing of the vector fields.