Applications of degradable polymers in wells

Abstract

Degradable polylactic or polyhydroxyalkanoate polymers may be used to viscosify aqueous fluids for use in wells, Sand control screen or liner can be coated with a solid degradable polymer during placement in a well. Mechanical changes or flow changes in a well can be caused by solid degradable polymer that changes physical properties after it is placed in a well. Parts of devices or entire devices can be made of solid degradable polymer that converts to a fluid after selected times in an aqueous environment in a well.

1 . A viscous well-treating fluid comprising a polylactic acid or a polyhydroxyalkanoate.  
     
     
         2 . The fluid of  claim 1  wherein the polylactic acid or polyhydroxyalkanoate is selected to be amorphous in the fluid.  
     
     
         3 . The fluid of  claim 1  further comprising an enzyme for increasing degradation rate of the polylactic acid or the polyhydroxyalkanoate.  
     
     
         4 . The fluid of  claim 1  further comprising a material to crosslink the polylactic acid or the polyhydroxyalkanoate.  
     
     
         5 . A method for preparing a viscous fluid for use in a well, the fluid comprising a degradable polymer, comprising: 
 supplying the degradable polymer; and    heating the degradable polymer in the presence of water to cause a decrease in molecular weight of the polymer before using the polymer in the well.    
     
     
         6 . The method of  claim 5  further comprising cooling the polymer and water before using the polymer in the well.  
     
     
         7 . The method of  claim 6  further comprising stabilizing or partially stabilizing the polymer against further decrease of molecular weight before using the polymer in the well.  
     
     
         8 . A sand control screen or liner comprising a solid degradable polymer coating.  
     
     
         9 . The sand control screen or liner of  claim 8  wherein the solid degradable polymer is a polyester.  
     
     
         10 . The sand control screen or liner of  claim 8  wherein the solid degradable polymer is selected from the group consisting of polylactic acid, polyhydroxyalkanoate, starches, polycaprolactone, polyesters based on polyethylene terephthalate or blends thereof.  
     
     
         11 . The sand control screen or liner of  claim 8  wherein the solid degradable polymer coating further comprises a solid material to increase strength of the polymer coating.  
     
     
         12 . The sand control screen or liner of  claim 8  wherein the solid degradable polymer coating further comprises a chemical to be released to enter fluids around the screen or liner as the polymer degrades.  
     
     
         13 . A method for delaying a mechanical action in a well comprising placing a solid degradable polymer in a device in an aqueous environment such that degradation of a mechanical property of the degradable polymer after a selected range of time allows operation of the mechanical action.  
     
     
         14 . The method of  claim 13  wherein the mechanical action is the release of a spring-loaded mechanism.  
     
     
         15 . A device for use in a well comprising a solid degradable polymer selected to decrease in strength a selected amount in a selected range of time in an aqueous environment in the well.  
     
     
         16 . The device of  claim 15  wherein the device is a packer, valve, bridge plug, flotation device or cement retainer.  
     
     
         17 . A method for changing a flow pattern or pressure in a well having an aqueous environment comprising placing a solid degradable polymer in a device or flow channel such that decrease of a strength of the degradable polymer after a selected range of time causes changing of the flow pattern or pressure.  
     
     
         18 . The method of  claim 17  wherein the solid degradable polymer is in the form of a plug, seal or gasket.  
     
     
         19 . A part of a device to be placed in a well in an aqueous environment, the part being made of a solid degradable polymer.  
     
     
         20 . The part of  claim 19  wherein the degradable polymer includes solid particles so as to form a composite with the solid degradable polymer.