Energy dispersive X-ray scatter for measurement of oil/water ratios

A technique for measuring oil and water concentrations in a bulk liquid using energy-dispersive X-ray scatter will be discussed. It is a requirement of the oil industry to measure accurately on-line the oil/water ratio of fluids extracted from oil fields across a wide range of gas–liquid flow regimes. To this end, a low cost, robust system is being developed using the energy dependence of coherent scatter as a probe to measure oil/water ratios. The scatter profiles are inherently broad and thus the relaxed energy resolution requirements allow the use of CdZnTe detectors suitable for field deployment. Energy-dispersive diffraction spectra of a range of oil–water emulsions have been measured. The ratio of the scattering into two energy windows, where the diffraction spectrum from oil is maximised and minimised with respect to that of water, is shown to be dependent upon the oil/water mixture ratios. The measurement is made independent of gas volume flow rate by normalisation of the scattered data to the transmission data. A relative error of 0.6% in the oil/water ratio measurement at 80% water fraction, and independent of gas fraction, is obtained.