Anti-accretion additives for drilling fluids

Abstract

Additives for drilling fluids, in particular for water-based drilling fluids are described which when added to the fluid at levels of up to 10% weight by volume reduces the accretion and bit-balling tendencies of shale cuttings exposed to said fluids. The additives are based on phosphonate chemistry, and are of the general class (I), wherein R, R′ and R″ are radicals exclusively containing H atoms or combinations of H, C, O or P atoms up to a maximum of 100 atoms.

1 . Additive for a drilling fluid, consisting of a compound in accordance with the formula  
       
         
           
           
               
               
           
         
       
       wherein R, R′ and R″ are radicals exclusively containing H atoms or combinations of H, C, O or P atoms up to a maximum of φatoms.  
     
     
         2 . The additive of  claim 1 , wherein R, R′ and R″ are radicals exclusively containing H atoms or combinations of H, C or O.  
     
     
         3 . The additive of  claim 1 , consisting of a compound in accordance with the formula  
       
         
           
           
               
               
           
         
       
       wherein R 1 , R 2  and R 3  are radicals exclusively containing H atoms or combinations of H, C, O or P atoms up to a maximum of 100 atoms.  
     
     
         4 . The additive of  claim 3 , wherein R 1 , R 2  and R 3  are radicals exclusively containing H atoms or combinations of H, C or O.  
     
     
         5 . The additive of  claim 1 , based on a phosphor derivative of the succinic acid.  
     
     
         6 . The additive of  claim 1 , based on a short chain phosphorylated hydrocarbon.  
     
     
         7 . Drilling fluid comprising an additive in accordance with  claim 1 .  
     
     
         8 . The drilling fluid of  claim 5 , comprising an additive in accordance with  claim 1  in a concentration of up to about 10% weight by volume.  
     
     
         9 . A drilling fluid comprising 
 water as base component;    a viscosifying agent to increase the viscosity of the fluid;    a filtrate reducing agent;    a weighting agent to adjust the density of the fluid; and    an additive for a drilling fluid, consisting of a compound in accordance with the formula                          wherein R, R′ and R″ are radicals exclusively containing H atoms or combinations of H, C, O or P atoms up to a maximum of 100 atoms.    
     
     
         10 . The drilling fluid of  claim 9 , wherein R, R′ and R″ are radicals exclusively containing H atoms or combinations of H, C or O.  
     
     
         11 . The drilling fluid of  claim 9 , wherein the additive consists of a compound in accordance with the formula  
       
         
           
           
               
               
           
         
       
       wherein R 1 , R 2  and R 3  are radicals exclusively containing H atoms or combinations of H, C, O or P atoms up to a maximum of 100 atoms.  
     
     
         12 . The drilling fluid of  claim 11 , wherein R 1 , R 2  and R 3  radicals exclusively containing H atoms or combinations of H, C or O.  
     
     
         13  The drilling fluid of  claim 9 , further comprising a shale swelling inhibition agent.  
     
     
         14 . The drilling fluid of  claim 13 , wherein the shale swelling inhibition agent comprises phosphate- or silicate-based compounds.  
     
     
         15 . Method of preventing accretion of cuttings in a borehole, said method comprising the step of adding to a drilling fluid and additive in accordance with  claim 1  prior to or during a drilling operation.  
     
     
         16 . The method of  claim 15 , wherein the additve is added in a concentration of up to about 10% weight by volume of the drilling fluid.