Method for reducing the viscosity of viscous fluids

Abstract

A viscous fluid, such as heavy crude oil which is too viscous to enable it to be pumped from a flowing phase of a reservoir into and along a pipeline for delivery to a refinery or other storage facility, may be contacted with a formulation to reduce its viscosity. The formulation comprises a polymeric material AA which includes —O— moieties pendent from a polymeric backbone thereof and said material is optionally cross-linked. In one embodiment, the formulation may comprise polyvinyl alcohol. In an alternative embodiment, the formulation may comprise a cross-linked polymeric material, such as cross-linked polyvinyl alcohol. After the viscous composition has been transported to a desired location, it may be separated from the other components.

1 - 61 . (canceled) 
     
     
         62 . A method for reducing the viscosity of a viscous composition which is arranged to flow along a fluid flow path, said method comprising contacting the viscous composition with a treatment fluid formulation, said treatment fluid formulation comprising a polymeric material AA which includes —O— moieties pendent from a polymeric backbone thereof, wherein polymeric material AA is an optionally cross-linked polysaccharide. 
     
     
         63 . A method according to  claim 62 , wherein the viscosity of the viscous composition after contact with the treatment fluid formulation is less than 300 cP measured at 25° C. and 1000 s −1 . 
     
     
         64 . A method according to  claim 62 , wherein the viscous composition, after contact with the treatment fluid formulation, exhibits shear thinning. 
     
     
         65 . A method according to  claim 62 , wherein said viscous composition is an oil. 
     
     
         66 . A method according to  claim 62 , wherein said treatment fluid formulation is initially contacted with said viscous composition at or downstream of a production means. 
     
     
         67 . A method according to  claim 62 , wherein said treatment fluid formulation is initially contacted with said viscous composition below ground. 
     
     
         68 . A method according to  claim 62 , wherein said fluid flow path is defined, in part, by a conduit which extends upwardly from below ground to above ground. 
     
     
         69 . A method according to  claim 62 , wherein said treatment fluid formulation is arranged to disperse and/or emulsify said viscous composition on contact therewith. 
     
     
         70 . A method according to  claim 62 , wherein flow is turbulent at the point of initial contact of said viscous composition with said treatment fluid formulation so that said composition is dispersed and/or emulsified on contact with said formulation. 
     
     
         71 . A method according to  claim 62 , wherein the amount of water in the composition in said fluid flow path immediately after contact between said viscous composition and said treatment fluid formulation is less than 70 wt %. 
     
     
         72 . A method according to  claim 62 , wherein said treatment fluid formulation has a viscosity at 25° C. and 1000 s −1  of greater than 1 cP and not greater than 50 cP. 
     
     
         73 . A method according to  claim 62 , wherein said treatment fluid formulation includes at least 70 wt % water. 
     
     
         74 . A method according to  claim 62 , wherein said treatment fluid formulation includes at least 0.2 wt % and less than 10 wt % of said polymeric material AA. 
     
     
         75 . A method according to  claim 62 , wherein said treatment fluid formulation includes 94.5 to 99.6 wt % water and 0.4 to 5.5 wt % of said polymeric material AA; and the ratio of the wt % of said treatment fluid formulation to the wt % of said viscous composition contacted in the method is in the range 0.4 to 0.9. 
     
     
         76 . A method according to  claim 62 , wherein said polymeric material AA is wholly soluble in water at 25° C. 
     
     
         77 . A method according to  claim 62 , wherein said polymeric material AA includes, on average, at least 10 —O— moieties pendent from the polymeric backbone thereof. 
     
     
         78 . A method according to  claim 62 , wherein the free bond to the oxygen atom in the —O— moiety pendent from the polymeric backbone of polymeric material AA is bonded to a group R 10  which comprises fewer than 10 carbon atoms and only includes atoms selected from carbon, hydrogen and oxygen atoms. 
     
     
         79 . A method according to  claim 62 , wherein said polymeric material AA includes a multiplicity of hydroxyl groups pendant from said polymeric backbone. 
     
     
         80 . A method according to  claim 62 , wherein said polymeric material AA is not cross-linked. 
     
     
         81 . A method according to  claim 62 , wherein after the viscous composition has been delivered to a desired location the viscous composition is caused to separate from other components of the treatment fluid formulation. 
     
     
         82 . A method according to  claim 81 , wherein separation is achieved by reducing mixing or turbulent movement of the mixture and allowing the viscous composition to settle out from the water and optionally cross-linked polymeric material AA. 
     
     
         83 . A method of reducing the viscosity of an oil which is arranged to flow along a fluid flow path, said method comprising contacting the viscous composition with a treatment fluid formulation, wherein said treatment fluid formulation includes a polymeric material which is an optionally cross-linked polysaccharide which:
 (a) associates with said oil in order to enable droplets of said oil to be formed and/or stabilised; and/or   (b) forms a coating around droplets of said oil; and/or   (c) forms a hydrogel which is able to stabilise droplets of said oil.   
     
     
         84 . A fluid flow path positioned at or downstream of a producing face of a subterranean formation, wherein said flow path contains a fluid comprising petroleum, water and a polysaccharide.