Rheological agent, preparation methods and uses thereof

Abstract

The present invention relates to a method to prepare a rheological agent comprising the polymerization of the following monomers: (a) at least one styrene-based monomer, (b) at least one (meth)acrylate-based monomer or butadiene, and (c) optionally a copolymerisable surfactant containing an optionally substituted vinyl function and moieties derived from propylene oxide and/or ethylene oxide, optionally in the presence of a non polymerisable surfactant containing moieties derived from propylene oxide and/or ethylene oxide, and optionally in the presence of another surfactant, wherein at least the copolymerisable surfactant or the non polymerisable surfactant is present during the said polymerization, as well as a rheological agent obtainable by said method, an oil-based drilling fluid containing such a rheological agent, the use of such a rheological agent as a thixotropic agent in an oil-based drilling fluid and a method of drilling using an oil-based drilling fluid containing such a rheological agent.

1 - 15 . (canceled) 
     
     
         16 . A method to prepare a rheological agent comprising the polymerization of the following monomers:
 (a) at least one styrene-based monomer substituted on the phenyl moiety,   (b) optionally at least one (meth)acrylate-based monomer or butadiene, and   (c) a copolymerisable surfactant containing an optionally substituted vinyl function and moieties derived from propylene oxide and/or ethylene oxide,   
       optionally in the presence of a non polymerisable surfactant containing moieties derived from propylene oxide and/or ethylene oxide, and 
       optionally in the presence of another surfactant. 
     
     
         17 . The method according to  claim 16 , wherein the copolymerisable surfactant is chosen among anionic and non-ionic surfactants. 
     
     
         18 . The method according to  claim 16 , wherein the non polymerisable surfactant is chosen among anionic and non-ionic surfactants. 
     
     
         19 . The method according to  claim 16 , wherein the styrene-based monomer is styrene substituted on the phenyl moiety with one or more substituents chosen among (C 1 -C 15 )alkyl, (C 2 -C 6 )alkenyl, (C 5 -C 8 )cycloalkyl, aryl and aryl-(C 1 -C 6 )alkyl. 
     
     
         20 . The method according to  claim 19 , wherein the styrene-based monomer is a (C 1 -C 6 )alkyl-styrene. 
     
     
         21 . The method according to  claim 19 , wherein the styrene-based monomer is chosen among para-tert-butyl-styrene (PTBS), para-methyl-styrene (PMS) and mixtures thereof. 
     
     
         22 . The method according  claim 16 , wherein monomer (b) is present and is at least one (meth)acrylate-based monomer corresponding to the following formula: 
       
         
           
           
               
               
           
         
       
       wherein:
 R a  represents a hydrogen atom or a methyl group, and 
 R b  represents a (C 1 -C 15 ) saturated hydrocarbon group. 
 
     
     
         23 . The method according to  claim 22 , wherein monomer (b) is at least one (meth)acrylate-based monomer chosen among isobornyl methacrylate (IBOMA), isobornyl acrylate (IBOA), isobutyl methacrylate (IBMA), 2-ethylhexyl acrylate (2-EHA) and mixtures thereof. 
     
     
         24 . The method according to  claim 16 , wherein the ratio by weight of monomer (a) to monomer (b) is comprised between 100:0 and 10:90. 
     
     
         25 . The method according to  claim 24 , wherein the ratio by weight of monomer (a) to monomer (b) is comprised between 100:0 and 50:50. 
     
     
         26 . The method according to  claim 25 , wherein the ratio by weight of monomer (a) to monomer (b) is comprised between 100:0 and 70:30. 
     
     
         27 . The method according to  claim 16 , wherein the copolymerisable surfactant has the following formula:
   CHR′═CRL-(O—CHR 7n —CHR 8n ) n —X 1  
   
       wherein:
 L represents a single bond or a linker, 
 R and R′ represent, independently of each other, H or a (C 1 -C 25 )alkyl, 
 n represents an integer of at least 1, 
 each R 7n  and each R 8n  represent, independently of each other, a hydrogen atom or a methyl group but R 7n  and R 8n  cannot both represent a methyl group, and 
 X 1  represents an —O-(optionally substituted aryl), —O(C 1 -C 25 )alkyl, —O—(C 1 -C 6 )alkanediyl-SO 3 H, —OH, —S(O) 2 (OH), —O—P(O)(OH) 2  or —O—S(O) 2 (OH) group, or a salt thereof. 
 
     
     
         28 . The method according to  claim 27 , wherein:
 R and R′ represent, independently of each other, H or a (C 1 -C 6 )alkyl, and   n represents an integer comprised between 3 and 120.   
     
     
         29 . The method according to  claim 28 , wherein:
 R and R′ represent, independently of each other, H or a methyl, and   n represents an integer comprised between 5 and 70.   
     
     
         30 . The method according to  claim 29 , wherein:
 R and R′ represent, independently of each other, H, and   n represents an integer comprised between 5 and 40.   
     
     
         31 . The method according to  claim 27 , wherein X 1  represents an —O-(optionally substituted aryl), —O(C 1 -C 25 )alkyl, —O—(C 1 -C 6 )alkanediyl-SO 3 H, —OH, —S(O) 2 (OH), —O—P(O)(OH) 2  or —O—S(O) 2 (OH) group, or a sodium, potassium or ammonium salt thereof. 
     
     
         32 . The method according to  claim 16 , wherein the non polymerisable surfactant has the following formula:
   X 3 —(OCH 2 CH 2 ) q —X 2  
   
       wherein:
 q represents an integer comprised between 1 and 60, 
 X 3  represents a (C 8 -C 25 )alkyl chain or an aryl optionally substituted with a (C 1 -C 25 )alkyl, and 
 X 2  represents an —OH, —S(O) 2 (OH), —O—P(O)(OH) 2  or —O—S(O) 2 (OH) group, or a salt thereof, 
 
     
     
         33 . The method according to  claim 32 , wherein
 represents an integer comprised between 3 and 20.   
     
     
         34 . The method according to  claim 32 , wherein X 2  represents an —OH, —S(O) 2 (OH), —O—P(O)(OH) 2  or —O—S(O) 2 (OH) group, or a sodium, potassium or ammonium salt thereof. 
     
     
         35 . The method according to  claim 16 , wherein the polymerization is carried out in the presence of a crosslinking agent. 
     
     
         36 . The method according to  claim 16 , using 0.5 to 10 wt % of copolymerisable and non polymerisable surfactants relatively to the total weight of the rheological agent on a dry basis. 
     
     
         37 . The method according to  claim 36 , using 1 to 7 wt % of copolymerisable and non polymerisable surfactants relatively to the total weight of the rheological agent on a dry basis. 
     
     
         38 . A rheological agent obtainable by the method according to  claim 16 . 
     
     
         39 . An oil-based drilling fluid comprising a rheological agent according to  claim 38 . 
     
     
         40 . The oil-based drilling fluid according to  claim 39 , containing 0.1 to 10 ppb (0.285 to 28.5 kg/m 3 ) of the rheological agent. 
     
     
         41 . A method of drilling using an oil-based drilling fluid according to  claim 39 .