A radioactive logging method for evaluating a wellbore and its surrounding formation in which gamma-ray emitting nuclides may be naturally present. A radioactive tracer is injected into the formation. The tracer emits gamma rays at at least one energy at which substantially none of the naturally present elements emit gamma rays. The wellbore is traversed with a gamma-ray detection system which is tuned to detect gamma rays at the one energy level of the tracer, thus providing a profile of tracer distribution in the formation.
The location in a wellbore of the top of a quantity of fill material which is sufficient to restrict flow in a tubing/casing annulus at a location deep in a well is determined by dropping a radioactive source through the annulus so that it falls to the top of the fill material. The depth of the thus deposited radioactive source is detected by radiation measurements, and the measured depth infers the location of the top of the fill material.
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, R.sub.p =(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.
A method of logging a well includes the steps of moving a tagging agent into a well so that the tagging agent is deposited in an earthen formation of the well, which tagging agent is non-radioactive at least until just prior to entering the well; irradiating the tagging agent so that the tagging agent exhibits at least one tagging agent characteristic distinguishable from earthen formation characteristics, and detecting the at least one tagging agent characteristic after the tagging agent has been deposited in the earthen formation.
A method of monitoring formation fractures in real-time is performed in which a fluid containing a radio-active tracer element is pumped at a high pressure down a wellbore into a formation. As the fluid creates fractures and moves through the formation gamma-rays are emitted from the radio-active tracer element in the fluid. Detector means placed at predetermined locations in the wellbore continuously detect these gamma-rays. Gamma-rays emitted from wellbore fracture fluids are distinguished from formation gamma-rays and the detected formation gamma-rays are counted. As the fracture fluid approaches the height or vertical depth of these detecter means, the gamma-ray count increases. Once the gamma-ray count reaches a predetermined level, the fracture will have reached a desired location in the formation and pumping of the fracture fluid will stop.
A method for removing radioactive barium sulphate from fluid carrying equipment includes immersing the equipment and scale in liquid nitrogen or other cyrogenic liquid, followed by immersing the equipment and scale in water or other aqueous solution, and subsequent impacting of the equipment and scale to remove the scale.
