Compensated neutron gamma density

A method comprising:

• irradiating a geological formation, via a pulsed neutron generator, with neutrons;
• detecting gamma rays from the geological formation by using one or more gamma ray detectors located at different locations relative to the pulsed neutron generator;
• detecting neutrons from the geological formation by using one or more neutron detectors located at different locations relative to the pulsed neutron generator;
• and
• analyzing the detected gamma rays and the detected neutrons to determine a compensated formation density, wherein analyzing the detected gamma rays and the detected neutrons to determine the compensated formation density comprises:
• measuring spectra of gamma rays detected by the one or more gamma ray detectors;
• and
• identifying, based on the spectra of gamma rays, gamma rays generated via inelastic scattering of the neutrons from heavy elements of the geological formation and neutron capture processes in the geological formation from the detected gamma rays;
• calculating a first calculated formation density and a second calculated formation density using the identified gamma rays from respective gamma ray detectors of the one or more gamma ray detectors and the detected neutrons from respective neutron detectors of the one or more neutron detectors;
• and
• obtaining the compensated formation density by using the first calculated formation density to compensate the second calculated formation density.

A system comprising:

• a downhole tool comprising:
• a neutron generator configured to emit neutrons into a geological formation;
• a first neutron detector and a second neutron detector located at different locations relative to the neutron generator, wherein the first and second neutron detectors are configured to detect neutrons that return to the downhole tool after interacting with the geological formation;
• and
• one or more gamma ray detectors configured to detect gamma rays from the geological formation that form when neutrons are inelastically scattered by the geological formation;
• and
• data processing circuitry associated with the downhole tool, wherein the data processing circuitry is configured to:
• calculate a first calculated formation density by using a first measurement of the first neutron detector and a measurement of a gamma ray detector of the one or more gamma ray detectors;
• calculate a second calculated formation density by using a second measurement of the second neutron detector and the measurement of the gamma ray detector;
• and
• obtain a compensated formation density by using the first calculated formation density to compensate the second calculated formation density.