PROCEDURE FOR NEUTRON GAMMA LOGGING AND FACILITY FOR ITS IMPLEMENTATION Russian patent published in 2010 - IPC G01V5/10 

FIELD: oil and gas production.

SUBSTANCE: borehole medium is radiated with neutrons generated by means of neutron generator with built-in alpha-particles detector. Alpha-particles resulted from reaction and escaped from the target in the direction counter to fast neutron escape are recorded. Also there is recorded gamma-radiation of inelastic scattering induced with neutrons. Notably, in the remote from the borehole zone dimensions and position of the alpha-particles detector in the neutron generator are chosen so, that controlled cone of neutron escape will have opening angle 30° and will be perpendicular to axis of the downhole instrument. A signal of gamma-quantum is recorded continuously in time by means of an analogue-digital converter with discreetness of 0.1…0.3 nano-seconds and is continuously recorded into memory of a micro-processor. At appearance of a pulse from an alpha-particle from the detector of alpha-particles built in the generator the micro-processor continues to record the signal of the gamma-quantum detector within a specified time interval. Upon completion of this interval there is established presence of the pulse from the gamma-quantum detector, its amplitude and time of arrival relative to the moment of neutron production in the pre-determined interval. There are selected pulses from gamma-quantum coinciding with power of not-scattered gamma-radiation of not-flexible scattering neutrons of elements Ca, Si, C, O, Fe, Mg, Al, Ti and S. Out of them there are formed time distributions, and there are calculated coordinates of boundaries of cylinder zones surrounding the well and concentration of elements Ca, Si, C, O, Fe, Mg, Al, Ti and S in them by selection of parameters of pre-determined model of borehole environment to the best coincidence with results of measured time distributions.

EFFECT: upgraded accuracy of logging and obtaining more complete data on borehole environment.

2 cl, 6 dwg