Low-cost multi-element capacitive monitor for measuring levels of substances in storage tanks at oil fields

Oil wells produce not only crude oil but also other substances such as water and methane. The production from an oil well is usually pumped into an on-site storage tank where different substances separate into oil, water, and oil/water emulsions. Economical instrumentation to reliably monitor the various layers would be useful for oil field operations.;This thesis describes the design and test results of a multi-level fluid monitor that is based on an array of capacitive sensors. The proposed design uses information from a series of capacitors that are equally distributed from top to bottom in the tank to distinguish different substances and determine the boundaries of air/oil and oil/water. Each sensor was calibrated separately in oil and in water to obtain a set of constants, which were used to process the sensor's output. The calibration method and data processing are described. To test the concept, a five-foot prototype consisting of 19 sensors was built and tested in water and in vegetable oil. The tests were designed to find the accuracy and the precision of the sensors when operating in water and in oil. The results and analysis for both types of fluids are reported. Most of the sensors acted as expected. However, there were several issues found in the current design, implementation, and test methodology, which are analyzed and discussed.