System and apparatus for creating a liquid carbon dioxide fracturing fluid

Abstract

A method, system, and apparatus required for creating a mixture of dry proppant and liquid carbon dioxide (LCO 2 ) for fracturing oil and gas formations is presented. The operation includes making a mixture of dry proppant and liquid carbon dioxide (LCO 2 ) for use in a fracturing operation by supplying dry proppant that is pressurized to between 75 and 600 psia with a gas; further supplying a stream of sub-cooled LCO 2 having a pressure substantially equal to that of the pressurized dry proppant; and adding dry, pressurized proppant to the stream of sub-cooled LCO 2 , thereby forming a mixed LCO 2 and proppant fracturing slurry.

1 - 9 . (canceled) 
     
     
         10 . An apparatus employed in a fracturing operation, comprising: at least one pressurized proppant storage vessel containing proppant and a gas, said vessel connected to a metering device for adding proppant into a sub-cooled LCO2 stream and;
 a sub-cooler for ensuring that the liquid carbon dioxide (LCO2) is in a sub-cooled liquid state and/or a booster pump(s) for increasing the pressure of the LCO2 stream above its saturation point and conveying the LCO2 to a mixing point, wherein proppant is metered into the LCO2 to form a fracturing fluid.   
     
     
         11 . The apparatus of  claim 10 , wherein said fracturing fluid is delivered to at least one high pressure pump to further increase the pressure of the fracturing fluid prior to supply to an injection well to carry out the fracturing operation. 
     
     
         12 . The apparatus of  claim 10 , wherein said sub-cooler provides a sub-cooled feed stream of LCO2 coupled with a device that monitors and/or controls pressure of at least one or more LCO2 storage tank(s) and simultaneously measures and controls the pressure and temperature of said sub-cooled LCO2 stream. 
     
     
         13 . The apparatus of  claim 10 , wherein said device includes a flow meter and a densitometer that measures the flow rate and density of said fracturing fluid. 
     
     
         14 . The apparatus of  claim 10 , wherein the gas added to said proppant storage tank is substantially a dry gas. 
     
     
         15 . The apparatus of  claim 10 , wherein said pressurized storage vessel includes at least one lock hopper for loading and unloading proppant. 
     
     
         16 . The apparatus of  claim 10 , wherein said fracturing fluid is provided on a continuous basis for fracturing during well injection. 
     
     
         17 . The apparatus of  claim 16 , wherein said fracturing fluid is provided on a semi-continuous basis for fracturing during well injection. 
     
     
         18 . The apparatus of  claim 16 , wherein said fracturing fluid is provided on a batch basis for fracturing during well injection. 
     
     
         19 . The apparatus of  claim 10 , wherein the sub-cooling of the feed stream of LCO2 is provided by any one of at least one heat exchanger, a head space pressurization unit, or by flashing LCO2 followed by increasing the pressure using a booster pump. 
     
     
         20 . The apparatus of  claim 10 , wherein said booster pump(s) are required to boost insufficient pressure supplied from said LCO2 storage tanks if said pressure is insufficient for maintaining sub-cooling of LCO2. 
     
     
         21 . The apparatus of  claim 10 , wherein said metering device is an auger, eductor, and/or proppant flow control valve, ensuring maintaining the proper flow-rate of said fracturing proppant. 
     
     
         22 . The apparatus of  claim 10 , wherein a densitometer and flow meter are also provided to ensure maintaining said flow rate in a manner required to achieve semi-continuous or continuous slurry injection for fracturing of a hydrocarbon well. 
     
     
         23 . The apparatus of  claim 10 , wherein said densitometer is a nuclear-sourced based densitometer. 
     
     
         24 . The apparatus of  claim 22 , wherein said flow meter is a magnetic field or coriolis-based flow meter, wherein said coriolis-based meter measures both density and flow-rate. 
     
     
         25 . The apparatus of  claim 10 , wherein said system is mobile in that it can be moved from one well location to another. 
     
     
         26 . A method for controlling a fracturing fluid composition, wherein a dry proppant is being routed and introduced into LCO2, thereby forming a liquid carbon dioxide proppant fracturing fluid. 
     
     
         27 . The method of  claim 26 , wherein conveying said fracturing fluid to at least one high pressure pump further raises the pressure of said fracturing slurry prior to supplying said slurry to an injection well for completing the fracturing operation. 
     
     
         28 . The method of  claim 26 , wherein a feedback loop controller capable of using parameter feedback data obtained from sensing devices for controlling the flow rate and pressure of said dry proppant, or said liquid carbon dioxide, or said or said fracturing fluid, or any combination thereof, is employed. 
     
     
         29 . A system for combining metered dry and warm proppant with a sub-cooled LCO2 stream resulting in a fracturing fluid comprising:
 (i) mixing of said proppant and LCO2 preventing carbon dioxide vapor from being generated by providing a pressure level of 50 psi NPSH or at least a pressure sufficiently above saturation conditions; and   (ii) recondensing any gaseous carbon dioxide entrained within the proppant of said fracturing fluid.   
     
     
         30 . (canceled)