RADIOAKTIVE BOHRLOCHMESSMETHODE.

摘要

A method of radioactive well logging for use in well operations wherein hydraulic fracturing material, including radioactive isotopes, is injected from a steel-cased well bore (31) into surrounding earth formations (33). Low energy gamma ray emitting radioisotopes are selected for tagging the liquids phase of the fracturing material and high energy gamma ray emitting radioisotopes are selected for tagging the solids phase. The relative amount of low energy radioisotope material inside the well bore (31) relative to the amount outside the casing (35) is determined to minimize the interfering effects of borehole tracers in determining concentrations of the high energy tracers in the formations. The procedure includes detecting the intensity of gamma radiation from the tracers in the borehole and surrounding formations by a detector (38) in the borehole in proximity to the injection zones and obtaining data representative of the radiation intensity. The intensity data is then separated into an observed energy spectrum from which is obtained observed energy spectrum count rates of gamma radiation in an energy region associated with gamma radiation emitted by the low energy tracer material in at least two relatively low energy ranges, a first P of which is highly sensitive to photoelectric attenuation by iron in the well casing and a second M of which is a higher energy range primarily sensitive to Compton scattered gamma rays and much less sensitive to photoelectric absorption by iron. These count rates are then combined to obtain an observed photoelectric ratio, Rp=M/P of the low energy tracer. Count rates of radiation are then obtained in all the energy ranges associated with gamma radiation emitted by the low energy tracer to obtain the total elemental concentration of the low energy tracer in the borehole and the formations. The amount of the low energy tracer in the borehole Tr(Bor) relative to the amount of said low energy tracer outside the casing is determined by a relation involving the observed photoelectric ratio Ph Tr(Obs) of low energy tracer, the total observed concentration of the low energy tracer Tr(Tot), and the low energy photoelectric ratios, Ph Tr(Bor) and Ph Tr(For), calibrated for the tracer in the borehole and in the formation, respectively.