Tank dewatering sensing and valve control method and apparatus

Abstract

A system for separating water from crude oil includes a bulk-storage tank for storing unrefined crude oil, a first pipe for delivering water separated from crude oil in the bulk-storage tank to a containment system, a second pipe for delivering crude oil to a shipping system, a first valve for controlling flow in the first pipe, a second valve for controlling flow in the second pipe, and a control system for controlling operation of the first and second valves. The control system has a control device for controlling the first and second valves, an acoustic sensor array mounted on the first pipe for sensing a sound pressure level during flow of water through the first pipe, means for comparing the sensed sound pressure level with a predetermined sound pressure threshold level characterizing flow of oil-water mixture through the pipe, and a control device for closing the first valve and opening the second valve when the measured sound pressure level reaches the sound pressure threshold level.

Description

RELATED APPLICATIONS[0001]This application claims the benefit of priority to U.S. Provisional Patent Application No. 61 / 541,713 filed Sep. 30, 2011, the disclosure of which is incorporated herein by reference in its entirety.FIELD OF THE INVENTION[0002]The present invention relates generally to dewatering a bulk-storage tank and, in particular, to a method and apparatus for detecting water-to-crude oil transition in a pipe.BACKGROUND[0003]Unrefined crude oil stored in a bulk-storage tank has a percentage of water entrained within the oil. Such crude oil is typically pumped into a bulk-storage tank prior to shipment. The capacity of bulk-storage tanks vary, but may be one-hundred (100) million barrels (i.e., 15.9 giga-litres). Over a period of twenty-four (24) to forty-eight (48) hours, the water and oil stored in a tank separate naturally, with the water collecting at the bottom of the tank beneath the oil. The separated water and the crude oil within the tank are very distinct exce...

AI Technical Summary

Benefits of technology

[0011]It is an object of the present invention to substantially overcome, or at least ameliorate, one or more disadvantages of prior art arrangements.

Problems solved by technology

However, recovering the oil from the containment area is an expensive exercise.

The reliability and accuracy of such a dewatering method is subject to the diligence of the operators.

However, density sensors such as those discussed above are not suitable for use with any liquid of unpredictable or erosive nature which can damage the tines causing erratic results.

Further, such density sensors require complicated fitting within a pipe in order to perform the sampling.

Still further such density sensors are prone to fouling when sampling particularly viscous liquids such as crude oil.

Images