Method for producing rubber member for downhole tool

Abstract

Provided is a rubber member for downhole tools, of which a decrease rate of 50% strain compressive stress after immersion for 24 hours in 150° C. water relative to 50% strain compressive stress before immersion is not less than 5%, and preferably not less than 50%. The rubber member is suitable for a seal member, ball sealer, ball seat, and a protecting member. Also provided is a downhole tool comprising the rubber member, and a method for recovering a hydrocarbon resource using the downhole tool.

1 . A method for producing a rubber member for a downhole tool, comprising
 performing a plurality of cycles of a molding process for obtaining a single rubber member,   wherein the rubber member is degradable within several weeks in a downhole.   
     
     
         2 . The method according to  claim 1 , wherein each of the plurality of cycles of the molding process comprises at least one of kneading, casting and injecting. 
     
     
         3 . The method according to  claim 1 , wherein each of the plurality of cycles of the molding process comprises the steps of:
 mixing a cross-linking agent into a thermoplastic urethane rubber; and   cross-linking the thermoplastic urethane rubber into which the cross-linking agent has been mixed.   
     
     
         4 . The method according to  claim 3 , wherein the step of cross-linking is performed during a melt molding process. 
     
     
         5 . The method according to  claim 3 , wherein the cross-linking agent is 5 to 30 parts by mass relative to 100 parts by mass of the thermoplastic urethane rubber. 
     
     
         6 . The method according to  claim 1 , wherein the rubber member is formed of a cast molding type urethane rubber and wherein each of the plurality of cycles of the molding process comprises casting and thermocuring a liquid starting material. 
     
     
         7 . The method according to  claim 1 , wherein the rubber member is formed of a crosslinked type, thermoplastic polyester-based urethane rubber. 
     
     
         8 . The method according to  claim 1 , wherein the rubber member is a circular rubber member. 
     
     
         9 . The method according to  claim 8 , wherein the circular rubber member is configured to be provided in an isolation plug. 
     
     
         10 . The method according to  claim 9 , wherein the isolation plug includes a mandrel and a pair of wedges which is configured to compress the circular rubber member so that the circular rubber member diametrically expands in a direction orthogonal to an axial direction of the mandrel so as to come into contact with an inside wall of the downhole. 
     
     
         11 . The method according to  claim 1 , wherein the rubber member exhibits a decrease rate of a 50% strain compressive stress after immersion for 24 hours in 150° C. water relative to a 50% strain compressive stress before the immersion of not less than 5%.