Sealing element and related methods

Abstract

Provided are sealing elements useful for isolating or diverting segments of a well in a hydraulic fracturing operation. These sealing elements resist the extreme temperatures and pressures encountered within a well, yet can be degraded or dissolved when no longer needed without use of hazardous acids or other chemicals. The sealing elements are made from a composite containing one or more resins of polylactic acid combined with a degradant that can be customized to provide facile degradation of the sealing element over a wide range of operative temperatures and pressures. These compositions may optionally include a swellant that causes the sealing element to expand after being seated against a well perforation or passageway to provide an enhanced seal.

1 . A sealing element for sealing at least a portion of a well for a hydraulic fracturing process, the sealing element made from a composite comprising:
 an amorphous polylactic acid resin; and cellulose acetate propionate.   
     
     
         2 . The sealing element of  claim 1 , wherein the cellulose acetate propionate is present in an amount of from 2 percent to 95 percent by weight, based on the overall weight of the composite. 
     
     
         3 . The sealing element of  claim 1 , wherein the sealing element further comprises a semi-crystalline polylactic acid resin. 
     
     
         4 . The sealing element of  claim 1 , wherein the composite further comprises a swellant selected from starch, polyvinylpyrrolidone, and combinations thereof. 
     
     
         5 . (canceled) 
     
     
         6 . The sealing element of  claim 4 , wherein the swellant is a modified starch comprising dextrin, cyclodextrin, acid-treated starch, alkaline-treated starch, bleached starch, oxidized starch, enzyme-treated starch, monostarch phosphate, distarch phosphate, phosphated distarch phosphate, acetylated distarch phosphate, starch acetate, acetylated distarch adipate, hydroxypropyl starch, hydroxypropyl distarch phosphate, hydroxypropyl distarch glycerol, starch sodium octenyl succinate, acetylated oxidized starch, or a combination thereof. 
     
     
         7 . The sealing element of  claim 4 , wherein the swellant is present in an amount of from 0.5 percent to 50 percent by weight, based on the overall weight of the composite. 
     
     
         8 . A sealing element for sealing at least a portion of a well for a hydraulic fracturing process, the sealing element made from a composite comprising:
 a polylactic acid resin; and a swellant comprising modified starch, wherein the composite is generally solid.   
     
     
         9 . The sealing element of  claim 8 , wherein the composite further comprises a carboxylic acid. 
     
     
         10 . The sealing element of  claim 9 , wherein the carboxylic acid is citric acid. 
     
     
         11 . The sealing element of  claim 8 , wherein the sealing element further comprises a plasticizer, the plasticizer comprising acetyl tributyl citrate. 
     
     
         12 . A method of sealing at least a portion of a well for a hydraulic fracturing process comprising:
 placing the sealing element of  claim 8  against a perforation or passageway within the well, the perforation or passageway having a smaller cross-section than the sealing element to restrict fluid communication between a first segment and a second segment of the well; and   degrading the sealing element to restore the fluid communication between the first and second segments.   
     
     
         13 . The method of  claim 12 , wherein degrading the sealing element comprises exposing the sealing element to a fracturing fluid at a temperature of from 50° C. to 170° C. and a pressure of 0.1 to 80 MPa. 
     
     
         14 . The method of  claim 13 , wherein the fracturing fluid comprises citric acid. 
     
     
         15 . A sealing element for sealing at least a portion of a well for a hydraulic fracturing process, the sealing element made from a composite comprising:
 a polylactic acid resin; and
 a swellant comprising polyvinylpyrrolidone. 
   
     
     
         16 . The sealing element of  claim 1 , wherein the sealing element further comprises a plasticizer, the plasticizer comprising acetyl tributyl citrate. 
     
     
         17 . A method of sealing at least a portion of a well for a hydraulic fracturing process comprising:
 placing the sealing element of  claim 1  against a perforation or passageway within the well, the perforation or passageway having a smaller cross-section than the sealing element to restrict fluid communication between a first segment and a second segment of the well; and   degrading the sealing element to restore the fluid communication between the first and second segments.