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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractA study from PDO indicated that the allocation and reconciliation factors of Nimr field had shown a deterioration trend since 1999. The suggested possible cause of this deterioration was the increase of net oil calculation uncertainty as water cuts approaches 80% and above. On the individual well basis, about 20% of all the wells produce at greater than 95% water cut but contribute to about 8% of production. The overall water cut of the Nimr asset is currently 87% and is forecast to increase to 90% over the next ten years causing further deterioration of the reconciliation factor.

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%.

In this paper, a low-cost and nonradioactive industrial field prototype device that provides continuous and real-time information of the vertical distribution of the oil, water, and emulsion (oil-water mixture) in the oil tank separator is presented. The device which is capable of detecting the emulsion layer with 15 cm resolution is installed into the vessel through an 8" (i.e., 20.3 cm) flange. It consists of a one dimensional array of 28 ultrasonic transducers which are activated in a time multiplexed manner by a separate transmitter located at the top of the tank. The transmitter explores the collected data, using a dedicated pattern recognition algorithm, to provide the position of the emulsion layer which is then transferred to the control room using industrial standard protocols (i.e., RS-485 and 4-20 mA output). The whole system is intrinsically safe and uses one single power source (12 VDC).