Hydrocarbons

Abstract

An oil production arrangement comprises an oil reservoir ( 4 ), a horizontal wellbore ( 6 ) and a vertically extending production well ( 8 ). A pump ( 10 ) is positioned at the bottom of the production well ( 8 ) for pumping fluid along the horizontal wellbore and up the production well for recovery. Tubing ( 12 ) having a fluid delivery device ( 14 ) at its end is introduced into the production well and moved downwards past the pump ( 10 ) and along the horizontal wellbore as far as possible for example close to the toe (not shown) of the wellbore or at least beyond a point in the wellbore at which it is assessed that the hydrocarbon flow has terminated because of a balance between reservoir pressure and wellbore differential pressure being achieved. From the start (or for example as soon as the tubing ( 12 ) enters the vertical annular gap between the product well and production tube) of introduction of tubing ( 12 ) into the production well and continuously thereafter a fluid is pumped through the tubing so it passes into the production well ( 8 ) as the tubing passes therethrough and into the horizontal wellbore ( 6 ) as the tubing passes therethrough. The fluid is still pumped into the horizontal wellbore after the tubing has reached its final position deep in the wellbore. The fluid is selected to enhance the mobility of oil and therefore increase the oil production rate.

1 . A method of increasing production of hydrocarbons from a reservoir penetrated by a wellbore which includes an associated artificial lift means, the method comprising:
 A.   (i) inserting a conduit having an outlet into the wellbore;   (ii) introducing treatment fluid into the wellbore via the outlet of the conduit as the conduit is moved into the wellbore, said treatment fluid being arranged to mobilise hydrocarbons; and/or   B.   (a) operating said artificial lift means to withdraw fluid from the wellbore and cause it to move to the production well;   (b) when said artificial lift means is operating, continuously introducing treatment fluid into the wellbore via a conduit having an outlet, said conduit extending from a production well along the wellbore, wherein said treatment fluid is arranged to mobilise said hydrocarbons.   
     
     
         2 . A method according to  claim 1 , wherein said conduit is inserted into the wellbore via an associated production well. 
     
     
         3 . A method according to  claim 1 , wherein said treatment fluid is injected from said conduit continuously as it is moved through a distance of at least 25 m along the wellbore. 
     
     
         4 . A method according to  claim 1 , wherein treatment fluid is flowing from the outlet of the conduit substantially during the entire passage of the conduit down the production well. 
     
     
         5 . A method according to  claim 1 , wherein after insertion of the conduit, the outlet is positioned at a distance of at least 25 m from the artificial lift means and/or from the heel of the wellbore. 
     
     
         6 . A method according to  claim 1 , wherein the time from the start of insertion of the conduit into the wellbore until it reaches its final stationary position is more than two hours. 
     
     
         7 . A method according to  claim 1 , wherein when said conduit is in a stationary position in the wellbore, the rate of introduction of treatment fluid into the wellbore is at least 1 m3/day and less than 200 m3/day. 
     
     
         8 . A method according to  claim 1 , wherein after reaching a stationary position, treatment fluid is introduced into the wellbore over a period of at least 10 days. 
     
     
         9 . A method according to  claim 1 , wherein the total volume of treatment fluid introduced into the wellbore is at least 250 m3. 
     
     
         10 . A method according to  claim 1 , wherein said conduit is a pipe having an external diameter of at least 1.5 cm and of 12 cm or less. 
     
     
         11 . A method according to  claim 1 , wherein said treatment fluid has a viscosity at 25° C. and 100 s-1 of greater than 0.98 cP and not greater than 10 cP. 
     
     
         12 . A method according to  claim 1 , wherein said treatment fluid comprises a first polymeric material which includes —O— moieties pendent from a polymeric backbone. 
     
     
         13 . A method according to  claim 12 , wherein said first polymeric material includes a moiety 
       
         
           
           
               
               
           
         
       
     
     
         14 . A method according to  claim 13 , wherein said first polymeric material includes a plurality of functional groups selected from hydroxyl and acetate groups. 
     
     
         15 . A method according to  claim 12 , wherein said first polymeric material includes a multiplicity of hydroxyl groups pendant from a polymeric backbone; and also includes a multiplicity of acetate groups pendant from the polymeric backbone. 
     
     
         16 . A method according to  claim 12 , wherein said first polymeric material includes a vinyl alcohol moiety. 
     
     
         17 . A method according to  claim 12 , wherein said first polymeric material comprises a 5 to 95% hydrolysed polyvinyl acetate. 
     
     
         18 . A method according to  claim 12 , wherein said first polymeric material is not cross-linked. 
     
     
         19 . A method according to  claim 12 , wherein the weight average molecular weight of said polymeric material (Mw) is in the range 5000 to 25000. 
     
     
         20 . A method according to  claim 12 , wherein said first polymeric material comprises a 60 to 99% hydrolysed polyvinylacetate. 
     
     
         21 . A method according to  claim 12 , wherein said treatment fluid includes 95 to 99 wt % of water, 0.1 to 1 wt % of said first polymeric material and 0 to 3 wt % of other additives. 
     
     
         22 . An assembly for use in the method of  claim 1 , comprising:
 (A) a conduit having an outlet for treatment fluid, said conduit extending from a surface into a wellbore and being arranged to deliver treatment fluid into the wellbore;   (B) an artificial lift means associated with the wellbore for facilitating removal of fluid from the wellbore;   (C) a receptacle at the surface, said receptacle containing treatment fluid;   (D) treatment fluid flowing within the conduit.   
     
     
         23 . A method of increasing production of hydrocarbons from a reservoir penetrated by a wellbore which includes an associated artificial lift means, the method comprising:
 A.   (i) inserting a conduit having an outlet into the wellbore;   (ii) introducing treatment fluid into the wellbore via the outlet of the conduit as the conduit is moved into the wellbore, said treatment fluid being arranged to mobilise hydrocarbons; and/or   B.   (a) operating said artificial lift means to withdraw fluid from the wellbore and cause it to move to the production well;   (b) when said artificial lift means is operating, continuously introducing treatment fluid into the wellbore via a conduit having an outlet, said conduit extending from a production well along the wellbore, wherein said treatment fluid is arranged to mobilise said hydrocarbons,
 wherein said conduit is inserted into the wellbore via an associated production well, said treatment fluid is injected from said conduit continuously as it is moved through a distance of at least 25 m along the wellbore, wherein after insertion of the conduit, the outlet is positioned at a distance of at least 25 m from the artificial lift means and/or from the heel of the wellbore, wherein the total volume of treatment fluid introduced into the wellbore in the method is at least 250 m 3 , and wherein said first polymeric material comprises a 60 to 99% hydrolysed polyvinylacetate.