METHOD FOR DETERMINING THE DENSITY subterranean formations using measured neutron gamma logging

摘要

FIELD: instrumentation.;SUBSTANCE: application: to define density of subsurface formations. The essence of the invention consists in the fact the density of a subsurface formation surrounding a bore well is defined on the basis of measuring the gamma rays resulting from the formation's exposure to the radiation from a nuclear source in the device casing which is set in the bore well, and the gamma ray flux is measured in the device casing at two different distances of detectors from the source; the method provides the definition of, in essence, straight-line relationship between the measurements of gamma ray fluxes at each different distance of detectors in terms of the formation density in case of no deviation of the device casing; definition of the relationship setting the density deviation caused by the device deviation and defined on the basis of the measurements of measured gamma ray flux at two different distances of detectors in terms of the density calculated on the basis of the straight-line relationships, and for this pair of measurements of gamma ray flux at different distances of detectors, a definition of intersection of the relationship, setting the deviation, with the straight-line relationship in order to specify the density of the formation surrounding the bore well. The source is a neutron source and the gamma rays measured in the device casing are the gamma rays induced by the neutrons and resulting from the neutron irradiation of the formation.;EFFECT: improved accuracy at the definition of subsurface formation density.;25 cl, 5 dwg