System, method and assembly for wellbore maintenance operations

Abstract

Methods for performing a wellbore maintenance operation on a system of wellbores used for improved oil recovery are disclosed. A plurality of wellbores are drilled and perforated to receive production fluids from a reservoir. The wellbores are fluidly connected to a production well that is drilled to a depth below the perforations of the wellbores. The production fluids drain and collect in the production well for delivery to the surface. A pump can be used for delivering the production fluids from the production well. During repair and maintenance operations, a fluid is injected into the production well for safely removing the pump components. The fluid is counterbalanced by the pressures in the connected wellbores such that the fluid does not rise above the perforations in the connected wellbores.

1 . A method of performing a wellbore maintenance operation, the method comprising:
 (a) providing a drainage wellbore that is perforated with a perforation such that the drainage wellbore receives reservoir fluids from a producing zone of a subterranean reservoir;   (b) providing a production wellbore in fluid communication with the drainage wellbore such that the reservoir fluids received by the drainage wellbore flow to the production wellbore;   (c) injecting fluid into the production wellbore until the flow of the reservoir fluids from the drainage wellbore to the production wellbore is stopped; and   (d) performing maintenance on the production wellbore.   
     
     
         2 . The method of  claim 1 , wherein the production wellbore is in fluid communication with the drainage wellbore through a drainage string that extends between the lower portions of the drainage wellbore and the production wellbore. 
     
     
         3 . The method of  claim 1 , wherein the fluid is injected into the production wellbore in step (b) until the fluid level within the production wellbore is at an elevation above the elevation of the perforation in the drainage wellbore. 
     
     
         4 . The method of  claim 1 , wherein the injecting of the fluid into the production wellbore in step (b) is stopped prior to the fluid level reaching the perforation in the drainage wellbore. 
     
     
         5 . The method of  claim 1 , wherein:
 at least two drainage wellbores are provided in step (a); and   the fluid is injected into the production wellbore in step (b) until the fluid level within the production wellbore is at an elevation above the perforations in the at least two drainage wellbores.   
     
     
         6 . The method of  claim 1 , wherein:
 at least two drainage wellbores are provided in step (a); and   the injecting of the fluid into the production wellbore in step (b) is stopped prior to the fluid level reaching any of the perforations in the at least two drainage wellbores.   
     
     
         7 . The method of  claim 1 , further comprising:
 (e) injecting a gas into the drainage wellbore to force the fluid back up through production wellbore and allow the reservoir fluids received by the drainage wellbore to flow to the production wellbore; and   (f) producing the reservoir fluids from the production wellbore.   
     
     
         8 . A method of performing a wellbore maintenance operation, the method comprising:
 (a) providing a system of wellbores comprising a drainage wellbore that is perforated with a perforation such that the drainage wellbore receives reservoir fluids from a producing zone of a subterranean reservoir, a production wellbore for producing the reservoir fluids, and a drainage string extending therebetween such that reservoir fluids received by the drainage wellbore flow through the drainage string to the production wellbore;   (b) injecting a fluid into the production wellbore until the hydrostatic pressure in the production wellbore is sufficient to stop the flow of the reservoir fluids received by the drainage wellbore from flowing to the production wellbore; and   (c) performing maintenance on the production wellbore.   
     
     
         9 . The method of  claim 8 , wherein the fluid is injected into the production wellbore in step (b) until the fluid level within the production wellbore is at an elevation above the elevation of the perforation in the drainage wellbore. 
     
     
         10 . The method of  claim 8 , wherein the injecting of the fluid into the production wellbore in step (b) is stopped prior to the fluid level reaching the perforation in the drainage wellbore. 
     
     
         11 . The method of  claim 8 , wherein:
 at least two drainage wellbores are provided in step (a); and   the fluid is injected into the production wellbore in step (b) until the fluid level within the production wellbore is at an elevation above the perforations in the at least two drainage wellbores.   
     
     
         12 . The method of  claim 8 , wherein:
 at least two drainage wellbores are provided in step (a); and   the injecting of the fluid into the production wellbore in step (b) is stopped prior to the fluid level reaching any of the perforations in the at least two drainage wellbores.   
     
     
         13 . The method of  claim 8 , further comprising:
 (a) injecting a gas into the drainage wellbore to force the fluid back up through production wellbore and allow the reservoir fluids received by the drainage wellbore to flow to the production wellbore; and   (b) producing the reservoir fluids from the production wellbore.   
     
     
         14 . A method of performing a wellbore maintenance operation, the method comprising:
 (a) providing a drainage wellbore that receives reservoir fluids from a producing zone of a subterranean reservoir;   (b) providing a production wellbore in fluid communication with the drainage wellbore such that the reservoir fluids received by the drainage wellbore flow to the production wellbore;   (c) injecting a fluid into the production wellbore until the hydrostatic pressure in the production wellbore is sufficient to stop the flow of the reservoir fluids from the drainage wellbore to the production wellbore;   (d) performing maintenance on the production wellbore;   (e) injecting a gas into the drainage wellbore to force the fluid back up through production wellbore and allow the reservoir fluids received by the drainage wellbore to flow to the production wellbore; and   (f) producing the reservoir fluids from the production wellbore.   
     
     
         15 . The method of  claim 14 , wherein the production wellbore is in fluid communication with the drainage wellbore through a drainage string that extends between the lower portions of the drainage wellbore and the production wellbore. 
     
     
         16 . The method of  claim 14 , wherein:
 the drainage wellbore is in fluid communication with the producing zone of the reservoir through a perforation in the drainage wellbore; and   the fluid is injected into the production wellbore in step (b) until the fluid level within the production wellbore is at an elevation above the elevation of the perforation in the drainage wellbore.   
     
     
         17 . The method of  claim 14 , wherein:
 the drainage wellbore is in fluid communication with the producing zone of the reservoir through a perforation in the drainage wellbore; and   the injecting of the fluid into the production wellbore in step (b) is stopped prior to the fluid level reaching the perforation in the drainage wellbore.   
     
     
         18 . The method of  claim 14 , wherein:
 at least two drainage wellbores are provided in step (a), each of the drainage wellbores being in fluid communication with the producing zone of the reservoir through a perforation in the drainage wellbore; and   the fluid is injected into the production wellbore in step (b) until the fluid level within the production wellbore is at an elevation above the perforations in the at least two drainage wellbores.   
     
     
         19 . The method of  claim 14 , wherein:
 at least two drainage wellbores are provided in step (a), each of the drainage wellbores being in fluid communication with the producing zone of the reservoir through a perforation in the drainage wellbore; and   the injecting of the fluid into the production wellbore in step (b) is stopped prior to the fluid level reaching any of the perforations in the at least two drainage wellbores.