Variable density treatment fluids

Abstract

The present invention provides variable density fluid compositions and methods for using such compositions in a subterranean formation. One exemplary embodiment of the variable density fluid compositions of the present invention comprises a variable density fluid comprising: a base fluid, and a portion of variable pressure weighting material particles.

1 . A variable density treatment fluid comprising: 
 a base fluid; and    a portion of variable pressure weighting material particles.    
   
   
       2 . The treatment fluid of  claim 1  wherein a portion of the variable pressure weighting material particles further comprises a compressible fluid that comprises air, propane, ammonia, fluorinated hydrocarbon refrigerants, nitrogen, carbon dioxide, argon, or mixtures thereof.  
   
   
       3 . The treatment fluid of  claim 1  having a density at sea level in the range of from about 4 lb/gallon to about 18 lb/gallon.  
   
   
       4 . The treatment fluid of  claim 1  wherein the portion of variable pressure weighting material particles is present in the treatment fluid in an amount in the range of from about 0.01% to about 40% by volume of the treatment fluid.  
   
   
       5 . The treatment fluid of  claim 1  wherein a portion of the variable pressure weighting material particles have a specific gravity in the range of from about 0.1 to about 0.5.  
   
   
       6 . The treatment fluid of  claim 1  wherein a portion of the variable pressure weighting material particles can withstand a pressure up to about 21,000 psi without crushing.  
   
   
       7 . The treatment fluid of  claim 6  wherein a portion of the variable pressure weighting material particles can rebound to about their original size and shape when the pressure is removed.  
   
   
       8 . The treatment fluid of  claim 1  wherein a portion of the variable pressure weighting material particles can withstand temperatures up to about 500° F. without degrading.  
   
   
       9 . The treatment fluid of  claim 1  wherein the density of the treatment fluid increases as the pressure in a subterranean bore hole increases.  
   
   
       10 . The treatment fluid of  claim 9  wherein the density of the treatment fluid in the bore hole is in the range of from about 0.01% to about 25% higher than its density at sea level.  
   
   
       11 . The treatment fluid of  claim 9  wherein the bore hole is located beneath the ocean floor.  
   
   
       12 . The treatment fluid of  claim 11  wherein the density of the treatment fluid decreases as the treatment fluid travels from the bore hole up to sea level.  
   
   
       13 . The treatment fluid of  claim 1  further comprising a salt, a fluid loss additive, a shale swelling inhibitor, an emulsifier, a viscosifier, caustic, or a fixed-density weighting agent.  
   
   
       14 . The treatment fluid of  claim 1  wherein the variable pressure weighting material particle comprises a material selected from the group consisting of: a plastic, an elastomer, a metal, and a memory metal.  
   
   
       15 . The treatment fluid of  claim 9  having a density sufficient to prevent kicks without fracturing a region of the subterranean formation adjacent to the borehole.  
   
   
       16 . A variable pressure weighting material particle comprising a hollow, elastically deformable particle.  
   
   
       17 . The variable pressure weighting material particle of  claim 16  further comprising a compressible fluid.  
   
   
       18 . The variable pressure weighting material particle of  claim 16  having a specific gravity in the range of from about 0.1 to about 0.5.  
   
   
       19 . The variable pressure weighting material particle of  claim 16  being capable of withstanding a pressure up to about 21,000 psi without crushing.  
   
   
       20 . The variable pressure weighting material particle of  claim 16  comprising a material selected from the group consisting of: a plastic, an elastomer, and a metal.