Well Drilling Method for Prevention of Lost Circulation of Drilling Muds

Abstract

An improved well drilling method for directional drilling in subterranean formations which comprises incorporating into the drilling fluid an effective amount of fibrillated hydrophobic polypropylene fibers to form a suspension and injecting the suspension into the drill string whereby debris is swept from the borehole and seepage of drilling fluid into the subterranean formation is reduced.

1 . An improved well drilling method for drilling in subterranean formations wherein a drilling fluid is injected into a drill string having a bottom hole assembly inserted into a borehole and the borehole can deviate from a vertical orientation by as much as 90 degrees, the improvement which comprises incorporating into the drilling fluid an effective amount of fibrillated hydrophobic polypropylene fibers to form a suspension and circulating the suspension through the drill string whereby debris is swept from the borehole and loss of drilling fluid into the subterranean formation is reduced. 
   
   
       2 . The improvement of  claim 1  wherein an effective amount of fibrillated hydrophobic polypropylene fibers is from 1.5 lbs up to 50 lbs of fibrillated hydrophobic polypropylene fibers per joint of pipe in the drill string. 
   
   
       3 . The improvement of  claim 2  wherein the circulating suspension of fibrillated hydrophobic polypropylene fibers is immediately followed by circulating one or more suspensions of other additives selected from the group consisting of cedar fibers, mica, cotton seed hulls and mixtures of such additives. 
   
   
       4 . In a directional well drilling process wherein the orientation of the borehole can deviate from vertical by as much as 90 degrees, an improved method for simultaneously sweeping debris from the borehole with a circulating drilling fluid while reducing lost circulation which comprises incorporating into the drilling fluid an effective amount of fibrillated hydrophobic polypropylene fibers. 
   
   
       5 . The method of  claim 4  wherein an effective amount of fibrillated hydrophobic polypropylene fibers is from 1.5 lbs up to 50 lbs of fibrillated hydrophobic polypropylene fibers per joint of pipe in the drill string. 
   
   
       6 . The method of  claim 5  which includes the additional step of circulating one or more suspensions of other additives selected from the group consisting of cedar fibers, mica, cotton seed hulls and mixtures of such additives in series with said fibrillated hydrophobic polypropylene fibers.