Water Content of Oil-Water Mixtures by the Speed of Sound Measurement

Abstract

Ultrasonic meters are calibrated for flow rate measurement of pure oil flows. However, the indicated oil flow rate is greater than its true value when water is mixed with oil in the flow, as usual in pipeline flows. A methodology was developed to continuously measure the water content of oil–water mixtures, using the already measured speed of sound by installed intrusive or non-intrusive (clamp on type) ultrasonic meters for flow rate measurement, together with the previously determined speed of sound and density of pure water and oil as a function of temperature, thus avoiding the traditional method of laboratory analysis of samples. This chapter shows a reduction of the uncertainty of measurement when the meter indicated speed of sound in the oil–water mixture is directly correlated to the traceable measurements of water content and temperature of previously prepared oil–water mixtures, what turns out to be the meter calibration for water content measurement. Water content uncertainty value of 0.0025 is obtained when fitting a curve to the experimental data by the least square method in the 0–0.025 range that covers the fiscal measurement range (<0.01).