Device for evaluating a uranium content and a hydrogen porosity of a particular region in a geological formation when drilling and associated method

A device for the borehole evaluation of a uranium content and a hydrogen porosity of a region of interest of a geological formation, the device comprising:

• a probe intended to be inserted into a borehole facing the region of interest, the probe including a pulsed neutron generator configured to emit at least one neutron pulse, at least some of said neutrons being emitted toward the region of interest, a single neutron detector arranged offset from the pulsed neutron generator, said neutron detector being suitable for detecting a plurality of neutrons resulting from interactions between neutrons emitted by the pulsed neutron generator and the region of interest, the probe further comprising a shielding device surrounding the neutron detector, the shielding device being suitable for absorbing a plurality of neutrons having an energy less than a cutoff energy, and resulting from interactions between the neutrons emitted by the pulsed neutron generator and the region of interest;
• a neutron counting unit connected to the neutron detector, the neutron counting unit being at least configured to measure, over time, during a first time interval, a number of neutrons backscattered by hydrogen nuclei of the region of interest and to measure, over time, during a second time interval, a number of prompt fission neutrons resulting from interactions between the neutrons emitted by the pulsed neutron generator and uranium nuclei present in the region of interest, the second time interval being subsequent to the first time interval;
• a hydrogen porosity evaluation unit configured to evaluate the hydrogen porosity of the region of interest using a total number of neutrons measured during the first time interval;
• and
• a uranium evaluation unit configured to evaluate the uranium content of the region of interest using a total number of neutrons measured during the second time interval.