Sequenced polymers for monitoring the filtrate

Abstract

The present invention relates to the use of a sequenced polymer as an agent for monitoring the filtrate in a fluid injected under pressure into an oil rock, wherein the fluid comprises solid particles and/or is brought into contact with solid particles within the oil rock after being injected, the polymer comprising at least three blocks, including: at least one first block which is adsorbed, preferably irreversibly, onto at least some of the particles (p); a second block (R) having a composition other than that of the first and a mean molecular weight of more than 10,000 g/mol, and which is soluble in the fluid (F); and at least one third block of type (A) or type (B).

1 . A fluid (F) for injecting under pressure into a subterranean formation, comprising a fluid loss control agent, wherein the fluid loss control agent is a block polymer (P) comprising:
 at least one first block (A); and   at least one second block (B) with a composition distinct from that of said first block, and with a weight-average molecular weight of greater than 10000 g/mol, and which is soluble in the fluid (F); and   at least one third block of type (A) or of type (B).   
     
     
         2 . The fluid claimed in  claim 1 , wherein the fluid (F) is aqueous. 
     
     
         3 . The fluid claimed in  claim 1 , wherein the block polymer (P) is a triblock polymer of (A)-(B)-(A) or (B)-(A)-(B) type or a polymer of star type comprising at least one branch of type (A) and at least two branches of type (B) or else comprising at least two branches of type (A) and at least one branch of type (B). 
     
     
         4 . The fluid claimed in  claim 1 , wherein the block polymer (P) is a polymer of comb type selected from the group consisting of:
 a polymer carrying several side blocks of type (A) on a linear block of type (B);   a polymer carrying several side blocks of type (B) on a linear block of type (A); and   a polymer carrying several side blocks of type (A) and (B) on a linear polymer chain.   
     
     
         5 . The fluid claimed in  claim 1 , wherein the fluid (F) does not comprise solid particles (p). 
     
     
         6 . The fluid claimed in  claim 1 , wherein the fluid (F) comprises, particles (p) combined with the polymer (P), the polymer being advantageously employed, in this case, as dispersing and stabilizing agent for the dispersion of the particles (p). 
     
     
         7 . The fluid claimed in  claim 1 , wherein the fluid (F) is an oil cement grout which comprises the polymer (P) as additive. 
     
     
         8 . The fluid of  claim 6 , wherein the at least one first block (A) of the polymer (P) is adsorbed on at least a portion of the particles (p). 
     
     
         9 . The fluid of  claim 8 , wherein the at least one first block (A) of the polymer (P) is adsorbed irreversibly on the the particles (p).