System and method for monitoring and removing scale from a wellbore

Abstract

A system and method for monitoring and removing scale from a wellbore according to which fluid is passed through a discharge head at a pressure and flow rate so that it discharges against the inner wall of the well to remove scale from the wall, and the pressure and flow rate of the fluid are measured so that the changes in the pressure and flow rate provide an indication of scale removal.

1 . A tool for use in a wellbore, comprising: 
 a discharge head for receiving fluid having a pressure and a flow rate, wherein the fluid is dischargeable from the discharge head to remove scale from the wellbore; and    a sensing element for engaging an inner wall in the wellbore, wherein the sensing element responds to changes in the diameter of the inner wall to change the pressure and the flow rate of the fluid.    
   
   
       2 . The tool of  claim 1  wherein the change in the pressure and the flow rate of the fluid provides an indication of the scale removal.  
   
   
       3 . The tool of  claim 1  wherein: 
 the discharge head receives the fluid from the ground surface; and    the sensing element diverts a portion of the fluid from the discharge head to change the pressure and the flow rate of the fluid.    
   
   
       4 . The tool of  claim 3  further comprising a sensing head connected to the discharge head, wherein the sensing element is mounted in the sensing head.  
   
   
       5 . The tool of  claim 4  wherein the sensing element moves from an extended position in which it engages the inner wall and a retracted position in which it engages scale on the inner wall.  
   
   
       6 . The tool of  claim 5  wherein: 
 the fluid flows from the ground surface to the discharge head when the sensing element in the extended position; and    a portion of the fluid is diverted from the discharge head to the sensing head for discharge from the tool when the sensing element is in the retracted position.    
   
   
       7 . The tool of  claim 1  wherein the changes in the diameter of the inner wall are a result of the accumulation of the scale on the inner wall.  
   
   
       8 . The tool of  claim 1  wherein: 
 the discharge head receives the fluid from a string extending between the tool and the ground surface; and    the changes in the pressure and the flow rate are measurable at the ground surface.    
   
   
       9 . The tool of  claim 8  wherein: 
 the fluid normally flows from the string to the discharge head; and    the sensing element diverts a portion of the fluid from the discharge head to change the pressure and the flow rate of the fluid.    
   
   
       10 . The tool of  claim 1  further comprising a sensing head connected to the discharge head upstream of the sensing head, wherein the sensing element is disposed in the sensing head.  
   
   
       11 . The tool of  claim 10  wherein: 
 the sensing head is in fluid flow communication with the discharge head; and    the fluid from the string passes through the sensing head to the discharge head.    
   
   
       12 . The tool of  claim 11  wherein the sensing head diverts a portion of the fluid flowing to the discharge head in response to the changes in the diameter of the inner wall and passes the diverted fluid externally of the tool to change the pressure and the flow rate of the fluid.  
   
   
       13 . The tool of  claim 10  wherein the sensing element moves relative to the sensing head in response to the changes in the diameter of the inner wall to divert the fluid.  
   
   
       14 . The tool of  claim 10  wherein the changes in the diameter of the inner wall are a result of the accumulation of the scale on the inner wall.  
   
   
       15 . The tool of  claim 10  wherein movement of the sensing element in one direction opens a diversion path for the fluid and movement of the sensing element in an opposite direction closes the diversion path.  
   
   
       16 . The tool of  claim 10  wherein the changes in the diameter of the inner wall are a result of the accumulation of the scale on the inner wall.  
   
   
       17 . The tool of  claim 1  wherein a casing disposed in the wellbore defines the inner wall.  
   
   
       18 . The tool of  claim 1  wherein a wall of the wellbore defines the inner wall.  
   
   
       19 . A method comprising the steps of: 
 flowing fluid at a pressure and a flow rate so that the fluid discharges against an inner wall of a wellbore to remove scale from the inner wall; and    responding to changes in the diameter of the inner wall to change the pressure and the flow rate of the fluid.    
   
   
       20 . The method of  claim 19  further comprising the step of measuring the pressure and the flow rate of the fluid so that the changes in the pressure and the flow rate provide an indication of scale removal.  
   
   
       21 . The method of  claim 19  wherein: 
 the fluid normally discharges from a discharge head; and    the pressure and the flow rate of the fluid is changed by diverting a portion of the fluid from the discharge head.    
   
   
       22 . The method of  claim 19  further comprising the steps of: 
 measuring the pressure and the flow rate of the fluid; and    controlling the operation of the tool accordingly.    
   
   
       23 . The method of  claim 19  wherein the step of responding comprises the step of engaging the inner wall with a sensing element which moves between an extended position and a retracted position in response to the changes in the diameter of the inner wall.  
   
   
       24 . The method of  claim 23  wherein: 
 the fluid is directed in a path so that it discharges against the inner wall to remove the scale when the sensing element is in the extended position; and    a portion of the fluid is diverted from the path to change the pressure and the flow rate of the fluid when the sensing element is in the retracted position.    
   
   
       25 . The method of  claim 24  further comprising the step of passing the diverted fluid externally of the tool.  
   
   
       26 . The method of  claim 19  wherein the changes in the diameter of the inner wall are a result of the accumulation of the scale on the inner wall.  
   
   
       27 . The method of  claim 19  further comprising the step of disposing a casing in the wellbore to define the inner wall.