Method of stabilising clay or shale

Abstract

A method of reducing the swelling of shale or clay encountered in a wellbore, the method comprising introducing into the wellbore a composition comprising: (a) a continuous aqueous phase; (b) a source of borate ions; (c) a source of ions selected from the group consisting of alkali metal ions, alkaline earth metal ions and ammonium ions; and (d) optionally a source of at least one sugar selected from the group consisting of monosaccharides and oligosaccharides having from 2 to 4 saccharide groups.

1 - 20  (cancelled).  
     
     
         21 . A method of reducing the swelling of shale or clay encountered during drilling a wellbore, the method comprising circulating in the wellbore a composition comprising: 
 (a) a continuous aqueous phase;    (b) a source of borate ions;    (c) a source of ions selected from the group consisting of alkali metal ions, alkaline earth metal ions and ammonium ions; and    (d) optionally a source of at least one sugar selected from the group consisting of monosaccharides and oligosaccharides having from 2 to 4 saccharide groups.    
     
     
         22 . A method of reducing the swelling of shale or clay encountered during the drilling of a wellbore through a formation using a drill string disposed within the wellbore, said drill string having a first end and a second end, the first end of the drill string being located at or near the surface of the wellbore and the second end of the drill string being in communication with a drill bit having ports therein, wherein: 
 (A) a drilling fluid composition comprising (a) a continuous aqueous phase, (b) a source of borate ions, (c) a source of ions selected from the group consisting of alkali metal ions, alkaline earth metal ions and ammonium ions, and (d) optionally a source of at least one sugar selected from the group consisting of monosaccharides and oligosaccharides having from 2 to 4 saccharide groups is introduced into the first end of the drill string, is pumped through the drill string from the first end to the second end thereof and is discharged into the wellbore through the ports in the drill bit; and (B) the drilling fluid composition is recycled to the first end of the drill string via an annular space which is provided between the drill string and the walls of the wellbore.    
     
     
         23 . A method according to  claim 21  wherein the source of borate ions is selected from the group consisting of sodium borates, potassium borates, caesium borates, ammonium borates, and boric acid.  
     
     
         24 . A method according to  claim 23  wherein the source of borate ions is selected from the group consisting of: 
 Disodium tetraborate pentahydrate—Na 2 O 2B 2 O 3  5H 2 O (borax pentahydrate),    Disodium tetraborate decahydrate—Na 2 O 2B 2 O 3  10H 2 O (borax decahydrate, tincal),    Disodium tetraborate tetrahydrate—Na 2 O 2B 2 O 3  4H 2 O (kernite),    Disodium tetraborate—Na 2 O 2B 2 O 3  (anhydrous borax),    Sodium metaborate tetrahydrate—Na 2 O B 2 O 3 8H 2 O,    Sodium metaborate dihydrate—Na 2 O B 2 O 3  4H 2 O,    Sodium pentaborate pentahydrate—Na 2 O 5B 2 O 3  10H 2 O,    Disodium octaborate tetrahydrate—Na 2 O 4B 2 O 3  4H 2 O,    Boric acid—H 3 BO 3 ,    Dipotassium tetraborate tetrahydrate—K 2 O 2B 2 O 3  4H 2 O,    Potassium pentaborate tetrahydrate—K 2 O 5B 2 O 3  8H 2 O,    Diammonium tetraborate tetrahydrate—(NH 4 ) 2 O 2B 2 O 3  4H 2 O,    Ammonium pentaborate tetrahydrate—(NH 4 ) 2 O 5B 2 O 3  8H 2 O, and    Caesium pentaborate tetrahydrate—Cs 2 O 5B 2 O 3  8H 2 O.    
     
     
         25 . A method according to  claim 21  wherein the concentration of borate expressed as B 2 O 3  in the continuous aqueous phase is in the range 0.1 to 150 lb/bbl.  
     
     
         26 . A method according to  claim 21  wherein the source of the alkali metal ions, alkaline earth metal ions and ammonium ions is a water soluble salt of an alkali(ne earth) metal, a water soluble ammonium salt or mixtures thereof.  
     
     
         27 . A method according to  claim 26  wherein the salt is selected from the group consisting of potassium salts, caesium salts, and ammonium salts.  
     
     
         28 . A method according to  claim 27  wherein the salt is selected from the group consisting of potassium bromide, caesium bromide, ammonium bromide, potassium chloride, caesium chloride, ammonium chloride, potassium hydroxide, caesium hydroxide and ammonium hydroxide.  
     
     
         29 . A method according to  claim 26  wherein the concentration of alkali metal salt, alkaline earth metal salt or ammonium salt in the continuous aqueous phase is in the range 0.1 to 150 lb/bbl.  
     
     
         30 . A method according to  claim 21  wherein the sugar is selected from the group consisting of glucose, fructose, sucrose, maltose, lactose and mixtures thereof.  
     
     
         31 . A method according to  claim 21  wherein the concentration of sugar in the continuous aqueous phase is in the range 0.1 to 150 lb/bbl.  
     
     
         32 . A method according to  claim 21  wherein the composition comprises additional additives selected from the group consisting of weighting agents, viscosifiers, fluid loss control agents, defoamers, lubricants, and glycols.  
     
     
         33 . A composition comprising (a) a continuous aqueous phase (b) a source of borate ions, (c) a source of ions selected from the group consisting of alkali metal ions, alkaline earth metal ions and ammonium ions and (d) a source of at least one sugar selected from the group consisting of monosaccharides and oligosaceharides having from 2 to 4 saceharide groups.  
     
     
         34 . A concentrate comprising a source of borate ions, a source of ions selected from the group consisting of alkali metal ions, alkaline earth metal ions and ammonium ions and a source of at least one sugar selected from the group consisting of monosaccharides and oligosaccharides having from 2 to 4 saceharide groups dissolved or dispersed in an aqueous phase.  
     
     
         35 . A concentrate as claimed in  claim 34  wherein the concentration of borate, expressed as B 2 O 3 , is in the range 10 to 250 lb/bbl, the concentration of alkali metal salt, alkaline earth metal salt or ammonium salt is in the range 10 to 150 lb/bbl and the concentration of sugar is in the range 10 to 300 lb/bbl.  
     
     
         36 . A concentrate as claimed in  claim 34  wherein the source of borate ions is as defined in claim  3 .  
     
     
         37 . A concentrate as claimed in  claim 34  wherein the source of the alkali metal ions, alkaline earth metal ions or the ammonium ions is as defined in claim  6 .  
     
     
         38 . A concentrate as claimed in  claim 34  wherein the source of the sugar is as defined in claim  10 .  
     
     
         39 . Use of a composition according to  claim 33  as a drilling fluid.