Assessment of the Applicability Gamma Ray Attenuation Method for Measurement of Three-PhasePermeability of Core Samples

Abstract

A gamma-ray attenuation method is an effective way for measurement of fraction content in oil/water mix in the petroleum industry. In particular, it is successfully applied for measurements of oil content of three-phase flux (oil/water/gas) in flowmeters of producing oil and gas wells. Another application of gamma densitometry is a direct measurement of dynamics of saturation of rock core samples in experimental studies of multiphase fluid filtration. Nonetheless, a realization of such measurement has a fundamental limitation associated with the large absorption of radiation in the core material and a weak dependence of attenuation on the composition of the fluid. The objectives of this work are to determine the optimal energies of gamma rays and to evaluate the time need for collecting sufficient statistics required to measure oil and water concentrations in the core. Based on the analysis of statistical errors, the optimal energy was found for one (“low energy”) of the two spectral lines used for the radiography of 40 keV. The energy of the second spectral line should be within the range of 80–300 keV. For reasonable parameters of gamma-ray source and geometry of the system, oil content measurement accuracy of 1% can be reached in 100 seconds.