Fluid Saturation in Porous Media by X-Ray Technique

This paper describes the application of x-ray theory to design procedures inconnection with fluid saturation determinations during fluid flow experimentswith porous media. A reliable and rapid method for calibrating the x-rayapparatus is described. Extension of the method to fluid saturationdeterminations in three-fluid systems is described. Introduction In research on oil production problems a method is required which will givequickly the quantity of each component of a fluid flow system present at anycross-section of a porous medium. The sample of porous medium under investigation is usually referred to as acore. The ratio of the volume of one component to the total fluid volume isdefined as the saturation of the porous medium by that component. This ratio isgenerally given as per cent saturation. Some means of measuring saturation which have received considerationinclude: electrical conductivity of the fluids; emissions from radioactivetracers dissolved in the fluids; the radioactivity of silver caused byreflection of neutrons from hydrogen atoms in the fluids, the attenuation of amicrowave beam, the diminution and phase shift of ultrasonic wave trains, andthe reduction in intensity of x-ray beams in passing through the fluids. X-rays have already been used with some success. Since every material has adifferent power to absorb x-rays, the reduction in intensity of an x-ray beamas it passes through a core depends on the fluids present. The strength of theemergent beam can be found by converting its energy into a measurable form suchas heat or ionic current, or by its effect on a photographic plate orfluorescent screen.. The beam strengths could be interpreted as quantities ofknown fluids in the core if, previously, these beam strengths had beenidentified with a known combination of the same fluids. With some fluidcombinations it might be desirable to dissolve powerful x-ray absorbingmaterials in one or more of the fluids, to increase the differences in the beamstrengths for various fluid saturations. Boyer, Morgan and Muskat have described a method of measuring two componentfluid saturation. One component was air or water; the other, mineral seal oilin which was dissolved 25 per cent by weight of iodobenzene to increase itsabsorbing power. The x-ray source was a tungsten target tube operated at 43 kvpotential. The beam emerging from the core was measured as ionic currentflowing across an air-filled ionization chamber by means of an amplifyingcircuit and galvanometer. Another portion of the beam from the x-ray tube waspassed through a metal plate and measured in another ionization chamber. Thisportion, called the monitor beam, was used as an indication of the performanceof the x-ray tube. The galvanometer readings were calibrated against air-oilcore saturations, gravimetrically determined. The method was apparentlyestablished by experimental means. T.P. 3169