Drilling lost circulation material

Abstract

An engineered composition for reducing lost circulation in a well includes a mixture of coarse, medium and optional fine particles, and a blend of long fibers and short fibers. The long fibers are rigid and the short fibers are flexible. The long fibers form a tridimensional mat or net in the lost-circulation pathway that traps the mixture of particles and short flexible fibers to form a mudcake. The mixture of particles and blend of fibers may be added to water-based and oil-based drilling fluids. The composition, size, and concentration of each component of the mixture of particles and blend of fibers may be fine-tuned for each application.

1 . A composition for reducing lost circulation in a well comprising a mixture of coarse particles having an average particle size of from 300 to 1200 μm, medium particles having an average particle size of from 20 to 150 μm and optionally fine particles having an average particle size of from 5 to 15 μm, and a blend of long fibers having an average length of from 8 to 15 mm and short fibers having an average length of from 1 to 8 mm. 
   
   
       2 . The composition of  claim 1  wherein the mixture of particles comprises from about 0 to about 15 weight percent fine particles, about 20 to about 40 weight percent medium particles, and about 40 to about 60 weight percent coarse particles. 
   
   
       3 . The composition of  claim 1  wherein the particles are selected from the group consisting of alkaline earth carbonates, poly-paraphenyleneterephthalamide, mica, rubber, polyethylene, polypropylene, polystyrene, poly(styrene-butadiene), fly ash, silica, mica, alumina, glass, barite, ceramic, metals and metal oxides, starch and modified starch, hematite, ilmenite, microspheres, glass microspheres, magnesium oxide, gilsonite, sand, and mixtures thereof. 
   
   
       4 . The composition of  claim 1  wherein the mixture of particles comprises about 8 to about 12 weight percent fine calcium carbonate, about 30 to about 40 weight percent poly-paraphenyleneterephthalamide, mica or calcium carbonate, and about 45 to about 60 weight percent coarse calcium carbonate. 
   
   
       5 . The composition of  claim 1  wherein at least about 60 weight percent of the mixture of particles is acid-soluble. 
   
   
       6 . The composition of  claim 1  wherein the fibers are selected from the group consisting of polyvinyl alcohol, polyamide, aramid, para-aramid, polylactic acid, polyglycolic acid, metals, painted metals, polymer-coated metals, hollow metals, hollow painted metals, hollow coated metals, polypropylene, polyethylene, polyester, polyamide, polyolefin, novoloid, phenol-aldehyde, nylon, rayon, extruded mineral wool, carbon, basalt, asbestos, and glass. 
   
   
       7 . The composition of  claim 1  wherein the weight ratio of long fibers to short fibers is from about 1:4 to about 4:1. 
   
   
       8 . The composition of  claim 7  wherein the length ratio of long fibers to short fibers is from about 1 to about 3. 
   
   
       9 . The composition of  claim 1  wherein at least a portion of the fibers is acid-soluble. 
   
   
       10 . The composition of any of  claim 1  wherein the long fibers comprise water-insoluble polyvinyl alcohol and the short fibers comprise water-soluble polyvinyl alcohol. 
   
   
       11 . The composition of  claim 1  wherein the short fibers comprise a mixture of fibers of two different lengths. 
   
   
       12 . The composition of  claim 11  wherein the short fibers comprise a mixture of two different lengths of polyvinyl alcohol fibers. 
   
   
       13 . The composition of  claim 11  wherein the short fibers comprise a mixture of multiple lengths of polyaramid fibers. 
   
   
       14 . A composition for reducing lost circulation in a well comprising a mixture of coarse particles having an average particles size of from 300 to 1200 μm, medium particles having an average particles size of from 20 to 150 μm and optionally fine particles having an average particles size of from 5 to 15 μm, and a blend of long fibers having an average length of from 8 to 15 mm and short fibers having an average length of from 1 to 8 mm., and a drilling fluid. 
   
   
       15 . The composition of  claim 14  wherein the mixture of particles is added to the drilling fluid at a concentration of from about 2.85 kg/m 3  to about 130 kg/m 3 . 
   
   
       16 . The composition of  claim 14  wherein the blend of fibers is added to the drilling fluid at a concentration of from about 14 kg/m 3  to about 42 kg/m 3 . 
   
   
       17 . The composition of  claim 14  wherein at least a portion of the fibers is coated with a material that improves the dispersion of the fibers in the drilling fluid. 
   
   
       18 . The composition of  claim 14  wherein the drilling fluid is water-based, the long fibers comprise water-insoluble polyvinyl alcohol and the short fibers comprise polyaramid fibers, water soluble polyvinyl alcohol fibers, or magma fiber. 
   
   
       19 . The composition of  claim 14  wherein the drilling fluid is oil-based and the long fibers comprise water-insoluble polyvinyl alcohol or para-aramid. 
   
   
       20 . The composition of  claim 14  wherein the drilling fluid is oil-based, the short fibers comprise para-aramid fibers and the long fibers comprise polyaramid fibers. 
   
   
       21 . The composition of  claim 14  wherein the drilling fluid is oil-based, the long fibers comprise non-water soluble polyvinyl alcohol fiber or magma fiber. 
   
   
       22 . The composition of  claim 14  wherein the long fibers comprise polyaramid fibers or polyvinyl alcohol fibers. 
   
   
       23 . The composition of  claim 14  wherein the short fibers comprise a mixture of two different lengths or a mixture of multiple lengths of fibers. 
   
   
       24 . The composition of  claim 14  wherein both the long fibers and the short fibers comprise polyvinyl alcohol fibers. 
   
   
       25 . A composition for reducing lost circulation in a well comprising a mixture of coarse particles having an average particle size of from 300 to 1200 μm, medium particles having an average particle size of from 20 to 150 μm and fine particles having an average particle size of from 5 to 15 μm, and a blend of fibers having a Young's Modulus of greater than about 20 GPa. 
   
   
       26 . The composition of  claim 25  wherein the different rigid fibers each comprise water-insoluble polyvinyl alcohol. 
   
   
       27 . A method of reducing lost circulation in a well comprising adding a mixture coarse particles having an average particles size of from 300 to 1200 μm, medium particles having an average particles size of from 20 to 150 μm and optionally fine particles having an average particles size of from 5 to 15 μm and adding a blend of long fibers having an average length of from 8 to 15 mm and short fibers having an average length of from 1 to 8 mm, to a drilling fluid and injecting the fluid into the well.