NEUTRON ACTIVATION LOGGING METHOD AND DEVICE FOR IT PERFORMING Russian patent published in 1997 - IPC

FIELD: geophysical prospecting engineering. SUBSTANCE: rock cyclic-discret neutron radiation flow exposing is making by well instrument moving from opening to bottom, induced gamma ray radiation appears correspondingly to well instrument moving velocity. Radiation flow N1 is measuring by gamma-quantum detector within interval length 40-60 cm and concentration of element is determining by induced gamma ray flow spectrum intensity measuring. Exposure is making by 14 MeV neutron flow puls generator and gamma ray induced radiation flow spectrum from nitrogen isotopic element 16 N2 is measuring additionally as function of time t with one step period 1-5 s by second gamma ray detector using which is placed by 40-60 cm upper than neutron source is placed and it is moving synchronously with the first one. Molecules N2 flow as function f(t) is measuring in interval between fast neutrons pulses with initial time delay t equal to 5-6 mcs when total cyclic exposure in one cycle is t=h/V where h is basic length of free displacement of neutron detector, V is well instrument raising up velocity. Spectrum intensity of N16 isotopic nuclear flow and it's raising time measuring permits seam overcurrent velocity of fluid and it relative intensity determining by V_f=l/t_f expression using where l is distance between second detector of gamma quantum and neutron pulse generator, t_f is time counting from exposure beginning moment of N2 flow entering to second detector area. Device for this method realizing has movable part of system control block and well instrument connected to surface control panel by geophysical cable. Surface control panel has depth pulse pick-up, n-capacity digital pulse counter, pulse amplitude analyzer, logging registrar, exposition block, power supply unit for well neutron generator and cycle start marker of exposure-metering beginning. Well instrument has additional second gamma quantum detector, second recorder-transmitting unit and moving part control block with depth signal pulses pick-up, end switch, blocking-up unit, second n-capacity digital pulse counter and second digit-analog converter. Moving system has second gamma ray quantum detector placed at 40-100 cm distance up with respect to neutron source position. EFFECT: higher accuracy of logging measurements. 2 cl, 3 dwg