External Casing Packer

Abstract

A method and apparatus for cementing a zone of borehole casing using an external casing packer (ECP). The method involves sealing the base of the ECP with a ball dropped in a seat, and then pressurising the casing to inflate an elastomeric packer sleeve through a one-way valve. When a design differential pressure is reached across the casing and elastomeric sleeve, a grout valve in the upper part of the packer opens to limit the sleeve inflation pressure and to provide a one-way valve through which cement grout passes to permit grouting of the annulus between the casing and the borehole.

1 . A method of cement grouting an annulus between a casing and a borehole using an inflatable packer system, comprising:
 placing a casing with an external casing packer attached thereto at a location in a borehole for cement grouting a portion of the borehole annulus that is located above the external casing packer;   inflating an inflatable elastomeric sleeve of the external casing packer to block the annulus of the borehole by pressurising the casing with an inflation fluid, which opens a one-way inflation valve in the external casing packer with the pressurised inflation fluid and inflates the inflatable sleeve to a preset pressure;   determining the preset pressure by a pressure relief valve located between the external casing packer and the annulus which opens at the preset pressure and then becomes a one-way grout valve;   pumping a liquefied cement grout mixture down through the casing via the open one-way grout valve which is located in the external casing packer above a portion of the inflated inflatable sleeve; and   biasing the grout valve to a closed position using an elastomeric member attached to the packer, whereby when the pressure of the cement grout mixture is reduced in the casing, the elastomeric member causes the grout valve to close and prevent backflow of the cement grout mixture from the annulus back into the casing.   
     
     
         2 . The method of  claim 1 , further including rupturing or shearing a portion of the grout valve at a given pressure to open the grout valve and permit a pressure drop in the casing. 
     
     
         3 . The method of  claim 2 , further including using the pressure drop in the casing to maintain closure of the sleeve inflation valve. 
     
     
         4 . The method of  claim 1 , further including pressurising the casing to open the one-way inflation valve and inflate the inflatable sleeve, and using the pressurised casing to shear an element of the grout valve to allow the grout valve to open when the inflatable sleeve is inflated. 
     
     
         5 . The method of  claim 1 , further including biasing the grout valve to a closed condition by the elastomeric member, by using an elastomeric sleeve member which both encircles the packer and is attached to a movable part of the grout valve. 
     
     
         6 . The method of  claim 1 , further including fabricating the elastomeric sleeve of the grout valve as part of the inflatable elastomeric sleeve, whereby when the grout valve is opened the elastomeric sleeve member stretches radially outwardly. 
     
     
         7 . The method of  claim 5 , further including bonding a portion of the elastomeric sleeve of the grout valve to a mandrel of the packer and bonding the elastomeric sleeve of the grout valve to a chamfered grout valve member, which is the movable member of the grout valve. 
     
     
         8 . The method of  claim 5 , further including forming the elastomeric sleeve member as a unitary part of the inflatable elastomeric sleeve during one manufacturing process. 
     
     
         9 . The method of  claim 1 , further including using a sleeve of an elastomeric material as a flap member of the non-return inflation valve, and bonding one annular edge of the elastomeric flap member sleeve to the mandrel of the packer, allowing another annular edge of the sleeve of elastomer material to be free for lifting off of respective ports in the mandrel to permit one-way fluid flow. 
     
     
         10 . A method of setting an external casing packer in an annulus of a borehole to fix a casing therein, comprising:
 sealing a base of the packer;   pressurising the packer to inflate an inflatable elastomeric sleeve surrounding a portion of a packer mandrel by passing a pressurised fluid through a one-way inflation valve into the inflatable sleeve;   limiting the inflation pressure of the inflatable sleeve by using a pressure relief valve in the packer which relieves the pressure in the packer to the outside of the casing when a design differential pressure is reached;   using the pressure relief valve as a one-way valve to permit a grout material to flow therethrough to the annulus of the borehole; and   closing the pressure relief valve to prevent a backflow of the grout material from the annulus back into the packer.   
     
     
         11 . A method according to  claim 10  whereby the base of the packer is sealed by dropping a ball into a seat located in the base of the packer. 
     
     
         12 . A method of cement grouting a borehole using an inflatable packer system, comprising:
 lowering into a borehole a casing with the inflatable packer system attached thereto;   pressurising the casing with a fluid so that the pressurised fluid enters one or more one-way inflation valves in the packer system to inflate a sleeve and obstruct an annulus of the borehole;   increasing the pressure of the fluid in the casing until one or more one-way frangible grout valves rupture to allow pressurised fluid to enter the borehole annulus above the packer system, whereby the pressure of the casing drops and the one-way inflation valves close and maintain the inflation of the sleeve in the borehole annulus;   pumping cement grout down through the casing and through the ruptured one-way grout valves into the portion of the borehole annulus located above the packer system.   
     
     
         13 . The method of  claim 12 , further including pumping a predetermined volume of the cement grout down the casing and into the borehole annulus, and then stopping the pumping of the cement grout, whereby the one-way grout valves close and prevent a backflow of the cement grout from the annulus back into the casing. 
     
     
         14 . The method of  claim 12 , further including sealing the base of the packer system before pumping the cement grout down the casing to prevent the cement grout from passing into a perforated portion of the casing below the packer system. 
     
     
         15 . The method of  claim 13 , further including forcing a plug down through the casing after the predetermined volume of cement grout has been pumped down the casing, to clear at least a portion of the cement gout from the casing and force the same through the one-way grout valves and into the borehole annulus. 
     
     
         16 . The method of  claim 15 , further including drilling the portion of the cement grout that has set in the packer system to provide a flow path of production fluid from the bottom of the borehole to the top of the casing. 
     
     
         17 . The method of  claim 12 , further including forming an elastomeric sleeve around a mandrel body of the packer system, where an annular top portion of the sleeve is anchored and scaled to the mandrel, and a bottom portion of the sleeve is slideable along and sealed to the mandrel as the sleeve is inflated. 
     
     
         18 . The method of  claim 17 , further including forming a portion of the elastomeric sleeve over the one-way grout valves so that elasticity of the sleeve moves the one-way grout valves into closed positions in respective ports formed in the mandrel. 
     
     
         19 . The method of  claim 17 , further including anchoring the top portion of the sleeve to the mandrel using a retaining ring which clamps the sleeve around the mandrel, and forming the one-way inflation valves by using an elastomeric flapper which covers respective ports formed in the mandrel, where the flappers are anchored at one end thereof to the mandrel under the retaining ring. 
     
     
         20 . An inflatable packer system for grouting a borehole annulus, said packer system comprising:
 a mandrel forming a body of the packer system, said mandrel adapted for attachment to a casing, said mandrel having formed therein one or more ports for respective grout valves, and one or more ports for respective inflation valves;   a seat formed in a bottom part of said mandrel, said seat adapted for being blocked by a ball dropped down the easing;   an elastomeric sleeve formed around the mandrel and around the inflation valve ports;   an anchor seal formed at a top portion of the elastomeric sleeve around the mandrel above the inflation valve ports and below the grout valve ports;   a sliding seal formed at a bottom portion of the elastomeric sleeve along said mandrel;   one or more one-way inflation valves, each said one-way inflation valve located over one said inflation valve port, each said one-way inflation valve adapted for allowing an inflation fluid to pass through the inflation valve port and into the elastomeric sleeve, but not in a reverse direction;   one or more one-way grout valves, each said one-way grout valve located over one said grout valve port, each said one-way grout valve adapted for allowing a cement grout to pass through the grout valve port and into the borehole annulus, but not in a reverse direction; and   each said one-way grout valve formed with a frangible member which breaks in response to a predetermined inflation fluid pressure, whereby when said elastomeric sleeve is inflated to the predetermined fluid pressure the frangible members break to enable operation of the one-way grout valves, and the one-way inflation valves close to allow the elastomeric sleeve to maintain the predetermined inflation fluid pressure.