Patent ID: 9645002
Date: 2017-05-09
CPC Classifications: E21B,G01F

Claim:
1. A method for identifying the level of three or more media in a desalter unit, comprising: providing within the desalter unit a sensing cable including an optical fiber sensor array aligned with a heating element; propagating a plurality of heat pulses through the heating element along at least a portion of the sensing cable to affect an exchange of thermal energy between the heating element and the one or more media exposed to the sensing cable; measuring, over time, a temperature profile of the sensing cable corresponding to each heat pulse at each of a plurality of sensor locations on the optical fiber sensor array; wherein measuring, over time, the temperature profile includes measuring using Fiber Bragg Grating array based sensing, wherein an optical signal interrogator is coupled to the optical fiber sensor array and configured to measure the temperature profile at a spatial resolution less than 1 cm; and identifying a level of each of the three or more media by determining one or more properties of the one or more media exposed to the sensing cable at each of the plurality of sensor locations based on the temperature profile corresponding thereto, wherein identifying the level of three or more media includes identifying the level of three or more of gas, foam, oil, emulsion, water, or solids within the desalter unit, wherein measuring the temperature profile corresponding to the heat pulse at each of the plurality of sensor locations includes, for each sensor location, measuring a plurality of temperatures over a period of time upon arrival of the heat pulse at the sensor location, wherein identifying the level of the three or more media includes, for each temperature profile: (i) generating a time derivative by calculating a derivative of the plurality of temperature measurements with respect to time; (ii) applying a transform to the time derivative to generate a complex spectrum; and (iii) determining an amplitude and a phase of the complex spectrum, wherein the amplitude and the phase of the complex spectrum relate to the one or more properties of the medium exposed to the sensing cable at the sensor location, wherein identifying the level of the three or more media further includes, for each temperature profile: generating a frequency derivative spectrum by calculating the derivative of the complex spectrum with respect to frequency; and determining an amplitude and a phase of the frequency derivative spectrum, wherein the amplitude and the phase of the frequency derivative spectrum relate to the one or more properties of the medium exposed to the sensing cable at the sensor location, and wherein identifying the level of the three or more media further includes calculating a difference in the amplitude and the phase between adjacent sensor locations, wherein the difference indicates an interface between two of the one or more media if the difference exceeds a predetermined threshold.