Bubble size monitoring and control

Abstract

Disclosed herein is a device and methods for enhancing oil separation from produced water. One such method includes mixing a multiphase fluid having at least a water phase and an oil phase with a flotation gas, according to at least one operating condition, so as to produce an enhanced multiphase fluid having bubbles of the flotation gas therein. The oil phase is then separated from the water phase using a separator. At least one property associated with the enhanced multiphase fluid is monitored. The operating condition is adjusted as a function of the monitored property so as to increase a percentage of the oil phase separated from the water phase by the separator over a percentage of the oil phase that would be separated from the water phase without adjustment of the operating condition.

1 . A system comprising:
 a first conduit for flowing a multiphase fluid;   a flotation gas source;   a mixing system having a first inlet in fluid communication with a downstream end of the first conduit, a second inlet in fluid communication with the flotation gas source, and an outlet, the mixing system configured to mix the multiphase fluid flowing from the downstream end of the first conduit with flotation gas from the flotation gas source so as to produce at the outlet an enhanced multiphase fluid having bubbles of the flotation gas therein;   a second conduit having an upstream end in fluid communication with the outlet of the mixing system;   a bubble control system associated with the second conduit and configured to:
 perform a measurement associated with a size of the bubbles of the flotation gas in the enhanced multiphase fluid; 
 control the mixing system in response to the measurement so as to influence the size of the bubbles of the flotation gas to be above a threshold value. 
   
     
     
         2 . The system of  claim 1 , wherein the bubble control system controls the mixing system in response to the measurement so as to influence the size of the bubbles of the flotation gas to be above a first threshold value and below a second threshold value. 
     
     
         3 . The system of  claim 1 , wherein the mixing system comprises an adjustable mixer having an adjustable outlet valve at the outlet thereof so as to adjust pressure of the enhanced multiphase fluid as it flows therethrough; and wherein the bubble control system controls the mixing system by causing a position of the adjustable outlet valve to change. 
     
     
         4 . The system of  claim 3 , wherein the adjustable outlet valve is a variable area orifice plate valve, a butterfly valve, a variable cage valve, an iris-diaphragm type variable valve, or a valve having a changeable restriction plate therein. 
     
     
         5 . The system of  claim 1 , wherein the mixing system comprises a static mixer and an adjustable valve associated with the static mixer and the second conduit so as to adjust pressure of the enhanced multiphase fluid as it flows through the second conduit; and wherein the bubble control system controls the mixing system by causing a position of the adjustable valve to change. 
     
     
         6 . The system of  claim 1 , wherein the mixing system includes a flotation gas source control for the flotation gas source; and wherein the bubble control system controls the mixing system by communicating with the flotation gas source control so as to change a flow rate of the flotation gas source. 
     
     
         7 . The system of  claim 1 , wherein the mixing system includes an adjustable gas valve associated with the flotation gas source; and wherein the bubble control system controls the adjustable gas valve so as to adjust pressure of the flotation gas as it enters the second inlet of the mixing system. 
     
     
         8 . The system of  claim 1 , wherein the bubble control system comprises:
 a camera associated with the second conduit and configured to capture images of the bubbles as the enhanced multiphase fluid flows through the second conduit; and   a controller configured to perform the measurement by performing image processing on the images of the bubbles so as to estimate the size of the bubbles, and control the mixing system in response to the estimated size of the bubbles.   
     
     
         9 . The system of  claim 1 , wherein the bubble control system comprises:
 a differential pressure sensing apparatus associated with the first conduit, second conduit, and mixing system, and configured to perform the measurement by determining a pressure differential between the multiphase fluid flowing into the first inlet of the mixer and the enhanced multiphase fluid flowing out of the outlet of the mixer; and   a controller configured to control the mixing system in response to the determined pressure differential.   
     
     
         10 . The system of  claim 1 , wherein the bubble control system performs the measurement by estimating a velocity of at least one of the multiphase fluid in the first conduit and the enhanced multiphase fluid in the second conduit. 
     
     
         11 . The system of  claim 1 , wherein the bubble control system controls the mixing system in response to the measurement so as to influence the size of the bubbles of the flotation gas to be above the threshold value regardless of a flow rate of the multiphase fluid through the first conduit. 
     
     
         12 . The system of  claim 1 , wherein the threshold value is greater than 100 microns. 
     
     
         13 . The system of  claim 1 , further comprising a separator having an inlet in fluid communication with a downstream end of the second conduit, and an oil outlet through which at least a portion of an oil phase of the enhanced multiphase fluid may be permitted to flow; and wherein the threshold value is sufficient so as to permit flowing of a majority of the oil phase through the oil outlet. 
     
     
         14 . A method comprising:
 mixing a multiphase fluid having at least a water phase and an oil phase with a flotation gas, according to at least one operating condition, so as to produce an enhanced multiphase fluid having bubbles of the flotation gas therein;   separating the oil phase from the water phase;   monitoring at least one property associated with the enhanced multiphase fluid;   adjusting the at least one operating condition as a function of the monitored at least one property so as to increase a percentage of the oil phase separated from the water phase over a percentage of the oil phase that would be separated from the water phase without adjustment of the at least one operating condition.   
     
     
         15 . The method of  claim 14 , wherein the mixing is performed using a mixer; wherein monitoring the at least one property comprises monitoring a fluid pressure differential across the mixer; and wherein adjusting the at least one operating condition comprises adjusting at least one of a flow rate of the flotation gas during the mixing and the fluid pressure differential. 
     
     
         16 . The method of  claim 14 , wherein the mixing is performed using a mixer; wherein monitoring the at least one property comprises monitoring an estimated size of the bubbles by performing image processing on images of the bubbles; and wherein adjusting the at least one operating condition comprises adjusting at least one of a flow rate of the flotation gas during the mixing and a pressure of the enhanced multiphase fluid. 
     
     
         17 . The method of  claim 14 , wherein the mixing is performed using a mixer; wherein monitoring the at least one property comprises estimating a velocity of at least one of the multiphase fluid and the enhanced multiphase fluid; and wherein adjusting the at least one operating condition comprises adjusting at least one of a flow rate of the flotation gas during the mixing and a pressure of the enhanced multiphase fluid. 
     
     
         18 . A method comprising:
 mixing a multiphase fluid with a flotation gas, according to at least one operating condition, so as to produce an enhanced multiphase fluid having bubbles of the flotation gas therein;   monitoring at least one property associated with the enhanced multiphase fluid; and   adjusting the at least one operating condition as a function of the monitored at least one property so as to influence a size of the bubbles to be above a threshold value.   
     
     
         19 . The method of  claim 18 , wherein the mixing is performed using a mixer; wherein monitoring the at least one property comprises monitoring a fluid pressure differential across the mixer; and wherein adjusting the at least one operating condition comprises adjusting at least one of a flow rate of the flotation gas during the mixing and the fluid pressure differential. 
     
     
         20 . The method of  claim 18 , wherein the mixing is performed using a mixer; wherein monitoring the at least one property comprises monitoring an estimated size of the bubbles by performing image processing on images of the bubbles; and wherein adjusting the at least one operating condition comprises adjusting at least one of a flow rate of the flotation gas during the mixing and a pressure of the enhanced multiphase fluid.