Apparatus and method for stimulating subterranean formations

A pressure equalization valve for a treatment tool movable in a completion string, a space being formed between the treatment tool and the completion string above an isolation device, the valve comprising:

• a cylindrical valve body having an axial bore in fluid communication with the treatment tool, a valve opening between the axial bore and the completion string below the isolation device, and one or more fluid ports above the valve opening between the axial bore and the space;
• a cylindrical shuttle axially and sealably movable in the axial bore and having an uphole bell-like portion for diverting fluid flow through the diverter flow ports and a downhole portion having the same diameter;
• one or more diverter flow ports adjacent the shuttle's uphole portion and formed between the axial bore of the valve body and the space, wherein the shuttle is operable between
• a closed position, the shuttle's downhole portion blocking the valve opening for blocking fluid flow through the one or more fluid ports between the space and the completion string below the isolation device, and
• an open position, the shuttle's downhole portion spaced from the valve opening for fluid communication between the space and the valve opening, fluid flowing from the treatment tool above, through the axial bore, diverting by the shuttle's uphole portion through the one or more diverter flow ports, flowing through the space, through the one or more flow ports and through the valve opening to the completion string below the isolation device;
• at least an upper seal between the axial bore and the shuttle's uphole portion;
• a stop fit in the axial bore intermediate the valve opening and the upper seal;
• a shoulder fit in the shuttle intermediate the shuttle's uphole and downhole portions and uphole of the stop in the axial bore;
• and
• a spring located between the stop and the shoulder and acting between the shuttle and the valve body for normally biasing the shuttle to the open position, wherein,
• when a flow rate of the fluid flowing from the treatment tool exceeds a preset rate to overcome the spring biasing, the shuttle shifts to the closed position, retaining the fluid flow in the space;
• and
• when the flow rate from the treatment tool drops below the preset rate, the spring biases the shuttle to the open position for equalizing the pressure above and below the isolation device.

A pressure equalization valve for a fracturing tool movable in a completion string, a space being formed between the fracturing tool and the completion string above at least two isolation devices forming the space therebetween and straddling a fluid ejection opening in the fracturing tool, the valve comprising:

• a cylindrical valve body having an axial bore in fluid communication with the treatment tool, a valve opening between the axial bore and the completion string below the isolation device, and one or more fluid ports above the valve opening between the axial bore and the space;
• a cylindrical shuttle axially and sealably movable in the axial bore and having an uphole portion and a downhole portion having the same diameter;
• one or more diverter flow ports adjacent the shuttle's uphole portion and formed between the axial bore of the valve body and the space, wherein the shuttle is operable between
• a closed position, the shuttle's downhole portion blocking the valve opening for blocking fluid flow through the one or more fluid ports between the space and the completion string below the isolation device, and
• an open position, the shuttle's downhole portion spaced from the valve opening for fluid communication between the space and the valve opening, fluid flowing from the treatment tool above, through the axial bore, diverting by the shuttle's uphole portion through the one or more diverter flow ports, flowing through the space, through the one or more flow ports and through the valve opening to the completion string below the isolation device;
• at least an upper seal between the axial bore and the shuttle's uphole portion;
• a stop fit in the axial bore intermediate the valve opening and the upper seal;
• a shoulder fit in the shuttle intermediate the shuttle's uphole and downhole portions and uphole of the stop in the axial bore;
• and
• a spring located between the stop and the shoulder and acting between the shuttle and the valve body for normally biasing the shuttle to the open position, wherein,
• when a flow rate of the fluid flowing from the treatment tool exceeds a preset rate to overcome the spring biasing, the shuttle shifts to the closed position, retaining the fluid flow in the space;
• and
• when the flow rate from the treatment tool drops below the preset rate, the spring biases the shuttle to the open position for equalizing the pressure above and below the isolation device.