Annulus plugging detection using a pressure transmitter in gas-lift oil production

Abstract

Outer annulus plugging detection is provided for gas-lift oil wells. The outer annulus detection is effected using a pressure transmitter. The pressure transmitter provides an indication of pressure within an outer annulus of the oil well. A statistical parameter related to a plurality of outer annulus pressure readings is used to provide an indication of annulus plugging. Examples of the statistical parameter include mean and standard deviation.

1 . A system for detecting outer annulus plugging in a gas-lift oil well, the system comprising: 
 a pressure transmitter operably coupleable to the outer annulus of the gas-lift oil well, the pressure transmitter being adapted to provide a signal related to pressure within the outer annulus; and    a controller configured to receive the signal and obtain a plurality of pressure measurements relative to the outer annulus, which measurements are temporally spaced, the controller being configured to calculate a parameter indicative of annulus plugging based on the plurality of pressure measurements.    
     
     
         2 . The system of  claim 1 , wherein the controller is a component of the pressure transmitter.  
     
     
         3 . The system of  claim 1 , wherein the pressure transmitter is adapted to provide a first signal indicative of pressure within the outer annulus, and a second signal indicative of plugging.  
     
     
         4 . The system of  claim 3 , wherein the pressure transmitter communicates over a digital process communication loop.  
     
     
         5 . The system of  claim 1 , wherein the pressure transmitter is powered by a digital process communication loop.  
     
     
         6 . The system of  claim 1 , wherein the pressure transmitter further comprises an analog-to-digital converter providing digital conversions to the controller.  
     
     
         7 . The system of  claim 1 , wherein the pressure transmitter further comprises an analog-to-digital converter providing a high-speed bitstream to the controller.  
     
     
         8 . The system of  claim 1 , wherein the parameter is a statistical parameter.  
     
     
         9 . The system of  claim 8 , wherein the statistical parameter is mean.  
     
     
         10 . The system of  claim 8 , wherein the statistical parameter is standard deviation.  
     
     
         11 . The system of  claim 8 , wherein the statistical parameter is a combination of mean and standard deviation.  
     
     
         12 . The system of  claim 1 , wherein the parameter is calculated using fuzzy logic.  
     
     
         13 . The system of  claim 1 , wherein the parameter is calculated using a neural network.  
     
     
         14 . A method of determining whether an outer annulus of a gas-lift oil well is at least partially plugged, the method comprising: 
 obtaining a plurality of temporally spaced pressure measurements within the outer annulus;    calculating a statistical parameter using the plurality of measurements; and    providing an indication of plugging based upon the statistical parameter.    
     
     
         15 . The method of  claim 14 , wherein the method is performed by a pressure transmitter.  
     
     
         16 . The method of  claim 14 , wherein the statistical parameter is mean.  
     
     
         17 . The method of  claim 14 , wherein the statistical parameter is standard deviation.  
     
     
         18 . A gas-lift oil well comprising: 
 a first pipe having a first pipe wall defining an interior adapted to convey pressurized crude oil;    a second pipe having a second pipe wall defining an inner annulus with the first pipe wall;    an outer shell defining an outer annulus with the second pipe wall; and    means for detecting plugging of the outer annulus.