SALINITY COMPENSATION OF A TDT INSTRUMENT USING SLOPE CORRECTION

A Time Domain Transmissometer (TDT) instrument has been developed to measure the water content of a stream of fluid, principally crude oil. Crude oil pumped from the ground is usually emulsified with water. The salt content of the water phase can be as high as 200 parts per thousand giving rise to conductivity levels of over 375 dS/m! The fluid dynamic behavior of the crude oil emulsion is such that the bulk electrical conductivity of the emulsion can randomly vary from zero to these high values in the space of a few seconds. Because the bulk electrical conductivity of the emulsion has an affect on the calibration of the instrument, the variations in this parameter must be accounted for if an accurate water content measurement is to be obtained. An algorithm is described that uses the rise time of the rising edge of the TDT pulse to estimate the bulk electrical conductivity and this estimate is used to compensate the water content measurement.

Ronald McFarlane