Coated And Cured Proppants

Abstract

Solid proppants are coated with a coating that exhibits the handling characteristics of a precured coating while also exhibiting the ability to form particle-to-particle bonds at the elevated temperatures and pressures within a wellbore. The coating includes a substantially homogeneous mixture of (i) at least one isocyanate component having at least 2 isocyanate groups, and (ii) a curing agent. The coating process can be performed with short cycle times, e.g., less than about 4 minutes, and still produce a dry, free-flowing, coated proppant that exhibits low dust characteristics during pneumatic handling but also proppant consolidation downhole for reduced washout and good conductivity.

1 - 33 . (canceled) 
     
     
         34 . A coated core particle that is substantially covered with a substantially cured coating that comprises at least one isocyanate component, a hydroxy-functional polyether polyol, at least one tin complex catalyst, wherein said coating can form particle-to-particle bonds under downhole conditions. 
     
     
         35 . The coated core particle of  claim 34 , wherein said coating can form particle-to-particle bonds that exhibit an unconfined compressive strength sufficient to generate proppant consolidation and provide flowback control. 
     
     
         36 . The coated core particle of  claim 34 , wherein said coating can form particle-to-particle bonds under downhole conditions that exhibit an unconfined compressive strength of greater than 100 psi. 
     
     
         37 . The coated core particle of  claim 34 , wherein the coated core particle resists proppant flowback at elevated temperature and pressure. 
     
     
         38 . The coated core particle of  claim 34 , wherein the coated core particle exhibits a negative TMA slope within the range of about 125° C. and 175° C. 
     
     
         39 . The coated core particle of  claim 34 , wherein said coated core particle exhibits a loss of coating of less than 15 wt % when tested according to ISO 13503-5:2006(E). 
     
     
         40 . The coated core particle of  claim 34 , wherein the coating comprises one or more of decarboxylated cashew nut oil, castor oil, cardol and cardanol. 
     
     
         41 . The coated core particle of  claim 34 , wherein the coating further comprises an adhesion agent. 
     
     
         42 . The coated core particle of  claim 41 , wherein the adhesion agent is a silane. 
     
     
         43 . The coated core particle of  claim 34 , wherein the core particle is a ceramic core particle. 
     
     
         44 . The coated core particle of  claim 34 , wherein the core particle is a sand particle. 
     
     
         45 . The coated core particle of  claim 34 , wherein the coating further comprises a pigment, dye, or tint. 
     
     
         46 . The coated core particle of  claim 34 , wherein the coating further comprises mica. 
     
     
         47 . A process for making the coated core particle of  claim 34 , the process comprising mixing a core particle with at least one isocyanate component, a hydroxy-functional polyether polyol, and at least one tin complex catalyst under conditions to coat the core particle with a substantially cured coating that comprises at least one isocyanate component, a hydroxy-functional polyether polyol and at least one tin complex catalyst. 
     
     
         48 . The process of  claim 47 , further comprising mixing the core particle with an adhesion agent. 
     
     
         49 . The process of  claim 48 , wherein the adhesion agent is a silane. 
     
     
         50 . The process of  claim 47 , wherein the core particle is a sand particle or a ceramic particle. 
     
     
         51 . The process of  claim 47 , further comprising mixing the core particle with a pigment, dye, or tint. 
     
     
         52 . The process of  claim 47 , wherein the process comprises:
 a) mixing the core particle with a silane;   b) mixing the product of step a) with the polyol and the tin catalyst;   c) mixing the product of step b) with the isocyanate.   
     
     
         53 . The process of  claim 52 , further comprising mixing the product of step c) with a silane.