An acoustic system for providing the two-phase liquid profile in oil field storage tanks

The continuing need for in situ measurements of the emulsion layer between crude oil and water within oil field tanks has initiated experimental and theoretical investigations of candidate measurement methods. This paper describes a new low-cost and nonradioactive industrial field prototype device that provides, continuously and in real time, the vertical profile of the 2-phase liquid within oil field tank separators (i.e., percentage of water in oil at different heights of the tank, as well as the emulsion layer interfaces) using ultrasonic waves. The device, which has been installed in a vessel through an 8-in. flange, consists of a 1-D array of tens of ultrasonic transducers (28 transducers in this paper) that are activated in a time-multiplexed manner by an embedded transmitter fixed on the top of the tank. This latest version implements a feedforward neural network with back-propagation learning to determine the vertical water-cut distribution along the vessel. It also implements an expert-system-based algorithm to determine the lower and higher positions of the emulsion layer. The results obtained from the extensive experiments, which have been conducted under various conditions of temperature, indicate that the device can determine the profile of the 2-phase liquid within a relative error of +/- 3%.