High Performance Drilling Fluids with Submicron-Size Particles as the Weighting Agent

Abstract

Methods and compositions utilizing a drilling fluid comprising sub-micron precipitated barite having a weight average particle diameter below about 1 micron. Methods include a method comprising circulating a drilling fluid in a well bore, wherein the drilling fluid comprises: a carrier fluid; and a weighting agent that comprises sub-micron precipitated barite having a weight average particle diameter below about 1 micron are disclosed. In some embodiments, the drilling fluid may comprise an invert emulsion. In some embodiments, the sub-micron precipitated barite has a particle size distribution such that at least 10% of particles in the sub-micron precipitated barite have a diameter below about 0.2 micron, at least 50% of the particles in the of the sub-micron precipitated barite have a diameter below about 0.3 micron and at least 90% of the particles in the sub-micron precipitated barite have a diameter below about 0.5 micron.

1 - 20 . (canceled) 
     
     
         21 . A method comprising:
 circulating a drilling fluid in a well bore, wherein the drilling fluid comprises:
 a carrier fluid; 
 a weighting agent that comprises sub-micron precipitated barite having a particle size distribution such that at least 10% of particles in the sub-micron precipitated barite have a diameter below about 0.2 microns, at least 50% of the particles in the sub-micron precipitated barite have a diameter below about 0.3 microns and at least 90% of the particles in the sub-micron precipitated barite have a diameter below about 0.5 microns; 
 a particle having a specific gravity of greater than about 2.6,
 wherein the particle having a specific gravity of greater than about 2.6 is not sub-micron precipitated barite; 
 
 such that the ratio of the sub-micron precipitated barite to the particle is about 10:90 to about 99:1; and 
 a degradable bridging agent that is not the submicron-precipitated barite or the particle, wherein the degradable bridging agent comprises at least one degradable polymer selected from the group consisting of a poly ether ester, poly(hydroxy ester ether), a polyester amide, and any combination thereof. 
   
     
     
         22 . The method of  claim 21  wherein the drilling fluid has a density of greater than about 9 pounds per gallon. 
     
     
         23 . The method of  claim 21  wherein the carrier fluid comprises at least one fluid selected from the group consisting of an aqueous-based fluid and an oleaginous-based fluid. 
     
     
         24 . The method of  claim 21  wherein the weighting agent is present in the drilling fluid in an amount of about 5% to about 70% by volume of the drilling fluid. 
     
     
         25 . The method of  21  wherein the drilling fluid comprises at least one additive selected from the group consisting of a viscosifying agent, a shale inhibitor, a pH-control agent, an emulsifier, a filtration-control agent, calcium hydroxide, and a salt. 
     
     
         26 . The method of  claim 21  wherein the drilling fluid is essentially free of viscosifying agent. 
     
     
         27 . The method of  claim 21  wherein the particle comprises at least one selected from a group consisting of manganese tetraoxide, barite, hematite, ilmenite, galena, calcium carbonate, and any combination thereof. 
     
     
         28 . The method of  claim 21  wherein the degradable bridging agent is self-degradable. 
     
     
         29 . The method of  claim 21  wherein the degradable bridging agent is degradable in a cleanup-solution. 
     
     
         30 . The method of  claim 21  wherein the degradable bridging agent has a size of about 1 micron to about 200 microns. 
     
     
         31 . The method of  claim 21  wherein the degradable bridging agent is present in the drilling fluid in an amount up to about 200 pounds per barrel. 
     
     
         32 . The method of  claim 21  wherein the carrier fluid has an oil-to-water ratio of 60/40 to 85/15. 
     
     
         33 . A method comprising:
 circulating a drilling fluid in a well bore, wherein the drilling fluid comprises:
 a foamed aqueous carrier fluid; 
 a weighting agent that comprises sub-micron precipitated barite having a particle size distribution such that at least 10% of particles in the sub-micron precipitated barite have a diameter below about 0.2 microns, at least 50% of the particles in the sub-micron precipitated barite have a diameter below about 0.3 microns and at least 90% of the particles in the sub-micron precipitated barite have a diameter below about 0.5 microns; 
 a particle having a specific gravity of greater than about 2.6, wherein the particle having a specific gravity of greater than about 2.6 is not sub-micron precipitated barite; 
 such that the ratio of the sub-micron precipitated barite to the particle is about 10:90 to about 99:1; and 
   a degradable bridging agent that is not the submicron-precipitated barite or the particle, wherein the degradable bridging agent comprises at least one degradable polymer selected from the group consisting of a poly ether ester, poly(hydroxy ester ether), a polyester amide, and any combination thereof.   
     
     
         34 . The method of  21  wherein the drilling fluid comprises at least one additive selected from the group consisting of a viscosifying agent, a shale inhibitor, a pH-control agent, an emulsifier, a filtration-control agent, calcium hydroxide, and a salt. 
     
     
         35 . The method of  claim 33  wherein the drilling fluid is essentially free of viscosifying agent. 
     
     
         36 . The method of  claim 33  wherein the particle comprises at least one selected from a group consisting of manganese tetraoxide, barite, hematite, ilmenite, galena, calcium carbonate, and any combination thereof. 
     
     
         37 . The method of  claim 33  wherein the degradable bridging agent is self-degradable. 
     
     
         38 . The method of  claim 33  wherein the degradable bridging agent is degradable in a cleanup-solution. 
     
     
         39 . The method of  claim 33  wherein the degradable bridging agent has a size of about 1 micron to about 200 microns. 
     
     
         40 . The method of  claim 33  wherein the degradable bridging agent is present in the drilling fluid in an amount up to about 200 pounds per barrel.