Dart-initiated multistage high pressure fracturing system

Abstract

A system and method for fracturing multiple zones in a hydrocarbon well is provided. The system comprises a series of multistage fracturing devices (MFD's) that are connected along a casing or completion tubing string and have ports that can be opened to allow fracturing of the formation adjacent the MFD. The ports in each MFD are triggered to open by a dart having a specific geometry that is pumped downhole and caught by a catching mechanism that comprises levers or “fingers” in the MFD. Upon catching of the dart, the section downhole of the dart can be sealed off and the ports located uphole of the dart can be opened to allow fracturing operations to occur.

1 . A device for connection to a casing or completion tubing in a wellbore to enable fluid access between an inner cavity of the device and a zone of interest in a hydrocarbon formation adjacent the device, the inner cavity being continuous with an internal bore in the casing or completion tubing, the device comprising:
 an outer sleeve for operative connection to the casing or completion tubing, the outer sleeve having at least one port to enable fluid access between the inner cavity and the zone of interest;   a catchment system operatively retained within the outer sleeve for catching a projectile moving through the inner cavity;   a sealing system operatively retained within the outer sleeve for sealing a downhole section of the device from an uphole section of the device when the projectile is caught;   wherein the at least one port can be opened through hydraulic activation when the sealing system is sealed; and   wherein an outer profile of the projectile determines whether the projectile will be caught.   
     
     
         2 . The device of  claim 1  wherein the projectile includes at least one shoulder on the outer profile, and the location and dimensions of the at least one shoulder determines whether the projectile will be caught by the catchment system. 
     
     
         3 . The device of  claim 1  wherein a first projectile having an outer diameter and an outer profile will be caught, while a second projectile having the same outer diameter as the first projectile and a different outer profile will pass through the catchment system. 
     
     
         4 . The device of  claim 1  wherein the catchment system comprises a plurality of levers pivotably connected around the circumference of the inner cavity, wherein the levers operatively engage with a projectile having a certain outer profile. 
     
     
         5 . The device of  claim 4  wherein the catchment system further comprises a biasing means in operative connection with the levers for biasing the levers in a first position. 
     
     
         6 . The device of  claim 1  wherein the sealing system comprises a piston and a sealing member positioned uphole and adjacent to a caught projectile, the sealing member deformable against the caught projectile by hydraulic actuation of the piston to seal the downhole section from the uphole section of the device. 
     
     
         7 . The device of  claim 1  wherein the catchment system is in a first shearing engagement with the outer housing, and wherein catchment of a projectile enables the first shearing engagement to disengage and the catchment system to move downhole with respect to the outer housing to enable the sealing system to seal. 
     
     
         8 . The device of  claim 8  wherein the catchment system is in a second shearing engagement with the outer housing, and wherein sealing of the sealing system enables the second shearing engagement to disengage and the catchment system to move further downhole with respect to the outer housing to open the at least one port. 
     
     
         9 . The device of  claim 1  wherein a caught projectile can be released from the catchment system to re-open the inner cavity. 
     
     
         10 . The device of  claim 9  wherein the caught projectile is dissolvable for releasing the caught projectile from the catchment system. 
     
     
         11 . A system for use in a wellbore comprising:
 a plurality of devices for connection to a casing or completion tubing in a wellbore to enable fluid access between an inner cavity of the device and a zone of interest in a hydrocarbon formation, each device of the plurality of devices comprising:
 an outer sleeve for operative connection to the casing or completion tubing, the outer sleeve having at least one port to enable fluid access between the inner cavity and the zone of interest; 
 a catchment system operatively retained within the outer sleeve for catching a projectile moving through the inner cavity; 
 a sealing system operatively retained within the outer sleeve for sealing a downhole section of each device from an uphole section of each device when the projectile is caught; 
 wherein the at least one port can be opened through hydraulic activation when the sealing system is sealed; and 
 wherein an outer profile of the projectile determines whether the projectile will be caught, 
   each device connected to the casing or completion tubing at a different location to selectively enable access to a zone of interest at each location by sending a projectile downhole from a well surface, the projectile having an outer profile configured to be caught by the catchment system at the desired location.   
     
     
         12 . A method for selectively enabling fluid access to a plurality of zones in a wellbore comprising the steps of:
 a) running an assembly having a plurality of actuatable devices into a wellbore having a plurality of zones, each device actuatable between a closed state and an open state, wherein in the open state fluid access between an internal bore of the assembly and a zone adjacent each device is enabled;   b) selectively actuating a device at the desired zone by:
 dropping a projectile having an outer profile with dimensions to be caught by the device at the desired zone; 
 catching the projectile in the device at the desired zone; 
 applying hydraulic pressure in the internal bore from a well surface to seal a section downhole of the caught projectile from a section uphole of the caught projectile; and 
 applying hydraulic pressure to move a member in the device downhole with respect to the assembly to open at least one port to provide fluid access between the internal bore and the adjacent zone; 
   c) performing well operations that require access to the desired zone; and   d) repeating steps b) and c) to successively actuate other devices in the assembly.   
     
     
         13 . The method of  claim 12  wherein the outer profile of the projectile includes at least one shoulder, and the position and dimensions of the shoulder determine whether the projectile is caught by a device. 
     
     
         14 . The method of  claim 12  wherein the projectile is caught by pivotable levers in the device. 
     
     
         15 . The method of  claim 12  wherein the plurality of devices are successively actuated in a downhole to uphole direction. 
     
     
         16 . The method of  claim 12  wherein the well operations include fracturing operations.