Inorganic deposit inhibitors, in particular in oil wells, particularly in high pressure/high temperature conditions

Abstract

The invention concerns inorganic deposit inhibitors, in particular in oil wells. Said inhibitors comprise a water soluble copolymer consisting of (in mol % of polymerised monomers): a) 5 to 95% of styrenesulphonic acid or one of its salts; b) 5 to 95% of vinylsulphonic acid or one of its salts; c) 0 to 20% of one or several non-ionizable unsaturated monomers. They are particularly efficient against calcium carbonate and/or barium sulphate deposits. They are capable of being used in accordance with a so-called squeeze process in HP/MT conditions with desorption compatible with the desired treatment duration.

1 - water soluble copolymer comprising (in mole % of polymerised monomers): 
 a) 5 to 95% of styrenesulphonic acid or one of its salts;    b) 5 to 95% of vinylsulphonic acid or one of its salts;    c) 0 to 20% of one or several non-ionisable unsaturated monomers, with the exception of monomers of the following formula:                          wherein R 1  and R 2  are, independently of each other, a hydrogen, a C 1  to C 4  alkyl, an ammonium ion or an alkali metal or alkaline earth metal ion.    
     
     
         2 - Copolymer according to  claim 1 , consisting of (in mole % of polymerised monomers): 
 a) 10 to 45% of styrenesulphonic acid or one of its salts;    b) 55 to 90% of vinylsulphonic acid or one of its salts.    
     
     
         3 - Copolymer according to claims  1  or  2 , wherein all or part of the sulphonic acids are replaced by their alkaline metal salts or their ammonium salts or their quaternised amine salts.  
     
     
         4 - Copolymer according to any of  claims 1  to  3 , wherein the styrenesulphonic acid is 4-styrenesulphonic acid.  
     
     
         5 - Copolymer according to any of  claims 1  to  4 , with a molar mass (by number) between 3 000 and 50 000 and preferably between 5 000 and 30 000.  
     
     
         6 - Copolymer according to any of  claims 1  to  5 , with a dispersity index M w /M n  less than or equal to 3.  
     
     
         7 - Inorganic deposit inhibitor consisting of a copolymer according to any of  claims 1  to  6 .  
     
     
         8 - Process for preparing a copolymer according to any of  claims 1  to  6 , wherein it comprises polymerising monomers in aqueous, water/alcohol or alcohol solution, in the presence of a free radical initiator and at a temperature of between 40 and 120° C.  
     
     
         9 - Use of the inorganic deposit inhibitor according to  claim 7  in oil wells.  
     
     
         10 . Use according to  claim 9  according to the squeeze process, consisting in injecting sea water into the well, then injecting the fluid containing the inhibitor into the well and injecting once again a flow of sea water.