Hydraulic fracturing of ground formations

Abstract

A method of hydraulic fracturing of ground formations. Such formations may be natural rock, earth or mineral formations and may be located on land or under a sea bed.

1 . A method of hydraulic fracturing a ground formation comprising: 
 passing a fracturing fluid through a fluid pump to generate a flow of pressurised fracturing fluid in a pumping line,    holding saturated particulate proppant in a proppant storage vessel disposed above the pumping line,    feeding saturated proppant from the storage vessel downwardly into the flow of pressure fluid downstream from the pump, and    passing the pressurised fracturing fluid with added proppant into the ground formation.    
     
     
         2 . A method as claimed in  claim 1 , wherein the saturated proppant is held in the storage vessel under pressure generally equal to the pressure in the pumping line to allow the saturated proppant to feed downwardly into the pumping line as a solids feed under gravity.  
     
     
         3 . A method as claimed in  claim 2 , wherein clean fluid is tapped from the pumping line upstream of the vessel to substantially equalise the pressure in the vessel with that of the pumping line.  
     
     
         4 . A method as claimed in  claim 1 , wherein the proppant in the vessel is saturated with the clean fracturing fluid and held in the vessel as close packed solid particulate material.  
     
     
         5 . A method as claimed in  claim 1 , wherein the fracturing fluid comprises water or a water based gel.  
     
     
         6 . A method as claimed in  claim 5 , wherein the fracturing fluid comprises water containing viscosity enhancing polymer material.  
     
     
         7 . A method as claimed in  claim 1 , wherein the proppant comprises sand.  
     
     
         8 . Apparatus for producing a supply of fracturing fluid containing a particulate proppant for use in hydraulic fracturing of ground formations, said apparatus comprising: 
 a clean fluid pump;    an output line from the pump for flow of pressurised clean fluid from the pump;    a proppant storage vessel to contain particulate proppant disposed above the output line from the pump and connectable to the output line to feed proppant from the vessel downwardly into the output line.    
     
     
         9 . Apparatus as claimed in  claim 8 , and further comprising a pressure equalisation line connected or connectable between an upper part of the vessel and the pump output line at a location upstream from the pressure vessel to enable the proppant to be held in the vessel at a pressure generally equal to the pressure in the pumping line to allow the proppant to feed into the pumping line as a solids feed under gravity.  
     
     
         10 . Apparatus as claimed in  claim 8 , further comprising a proppant meter to meter the admission of proppant from the vessel into the output line.  
     
     
         11 . Apparatus as claimed in  claim 10 , wherein the proppant meter is located at the bottom of the vessel to meter the proppant at a controlled rate from the vessel into the output line.  
     
     
         12 . Apparatus as claimed in  claim 11 , wherein the meter comprises a metering gate.  
     
     
         13 . Apparatus as claimed in  claim 8  wherein the pressure vessel is provided with a top valve operable to allow the vessel to be filled with proppant through the valve when opened and to be closed to allow the vessel to pressurised.  
     
     
         14 . Apparatus as claimed in  claim 13 , wherein there is a valve on the pressure equalisation line operable to close off that line for filling of the vessel with proppant.  
     
     
         15 . Apparatus as claimed in  claim 14 , wherein the top valve and the valve on the pressure equalisation line are operatively linked such that opening of the top valve causes the valve on the pressure equalisation line to close thereby to close off the connection of the fluid equalisation line with the upper part of the vessel.  
     
     
         16 . Apparatus as claimed in  claim 13  wherein the vessel is provided with a bottom valve operable to isolate the interior of the vessel from the output line.  
     
     
         17 . Apparatus as claimed in  claim 16 , wherein the top and bottom valves are operatively linked such that the bottom valve to be closed so as to isolate the vessel from the output line when the top valve is opened for a filling operation.