Improved Multiphase Flow Studies Employing Radioactive Tracers

Abstract

Abstract Two radioactive tracers have been tested as a means of determining coresaturation in multiphase flow studies. Cesium 134 chloride was tried as awater-phase tracer, but complications in its use in low permeability coresresulted from sorption of cesium by the core or water-wet pads. Iodo 131 benzene proved very satisfactory as an oil-phase tracer. The synthesis ofiodobenzene from the sodium iodide as received from Oak Ridge is simple anddirect. The tracer is insoluble in water and there was no evidence of sorptionby any of the core materials used. Use of the method to determine saturation profiles during capillary anddynamic desaturations and relative permeability measurements on oil-water andoil-gas systems is described. Comparisons of the dynamic and capillary methodsof relative permeability determination were made using the tracer to check coresaturation and saturation distribution. Other experiments are also described inwhich mobility of the oil phase at various saturations was measured bydisplacing labeled oil by flowing inactive oil. Similar experiments were madeusing water labeled with cesium 134. Introduction To be fundamentally sound, any laboratory method of determining relativepermeability must meet, among others, the following requirements:the coresaturation between the pressure taps must be uniform, andthere must beuniform pressure difference between the phases in the region between thepressure taps. In practice it may eventually be shown that appreciabledeparture from either or both of these conditions may be permitted withoutintroducing sensible error, but the magnitude of such error remains to beestablished. There is need then for methods of saturation determination whichwill determine the saturation profile in a core as well as the overall averagesaturation given by the gravimetric or material balance methods usuallyemployed. Methods which have received consideration include resistivity, X-rayabsorption, gamma ray absorption, neutron diffraction, and radioactive tracers.The resistivity method has use in the determination of profile, but needschecking by independent means. The X-ray method has been used successfully, butrequires elaborate equipment and calibration. At present gamma ray absorptionis practical only for very large cores. The neutron method does not appearadaptable to measurement of saturation variations in short cores since it is ascattering method. Russell, Morgan and Muskat employed radiovanadium in a studyof the mobility of interstitial water. Coomber and Tiratsoo used radioiodine asan oil-phase tracer and measured profiles in unconsolidated sand packs. T.P. 3284