Downhole pressure wave generating device
A device for generating pressure waves in a well or a wellbore. The device includes a housing containing an impact-generating mechanism for generating the pressure waves and a connector for connecting the housing to a conveyor for transporting the device to any desired location within the well or the wellbore. The device may be used for a number of downhole applications such as cleaning perforations, fracturing processes, vibration of a casing to prevent fluid flow in a cemented annulus, hydraulic jar operations for freeing stuck downhole objects, generating data to optimize pumping parameters and as an enhancement to percussion drilling techniques.
1. A device for generating pressure waves in a well or a wellbore, the device comprising:
a housing containing an impact-generating mechanism for generating the pressure waves, wherein the impact-generating mechanism comprises a piston contained within a cylinder, the piston configured to impact an upper surface of an anvil; and
a connector for connecting the housing to a conveyor for transporting the device to any desired location within the well or the wellbore,
wherein the device is configured for operation by a pneumatic control system, the device including a plurality of valves configured to fire the piston and to return the piston to a firing position and vent air from the device.
2. The device of claim 1 , further comprising a pressure wave outlet located below the anvil, the pressure wave outlet defined by a plurality of openings permitting propagation of the pressure waves from inside the device into fluid contained in the well or wellbore.
3. The device of claim 2 , wherein the upper surface of the anvil is located above the pressure wave outlet and a bottom surface of the anvil is located within a cavity of the pressure wave outlet.
4. The device of claim 2 , wherein the anvil further comprises an upper radial extension below a contact surface, wherein a lower surface of the radial extension is adjacent to an upper surface of the pressure wave outlet.
5. The device of claim 2 , wherein the plurality of openings is at least one set of three radially aligned elliptical or stadium-shaped openings.
6. The device of claim 1 , wherein the cylinder is configured to provide a piston stroke which is longer than half of the length of the piston.
7. The device of claim 6 , wherein the piston stroke is at least about twice as long as the length of the piston.
8. The device of claim 7 , wherein the piston stroke is about three times as long as the length of the piston.
9. The device of claim 1 , wherein the anvil comprises a constricted middle portion and a flared bottom portion.
10. The device of claim 9 , further comprising one or more seals between an outer sidewall of the anvil above the constricted middle portion and an inner sidewall of a pressure wave outlet, wherein working fluid contacts the anvil below the one or more seals.
11. The device of claim 1 , wherein the conveyor further comprises a coiled tubing conveyor, and wherein the connector is configured for connection to the coiled tubing conveyor.
12. The device of claim 1 , wherein the pneumatic control system is further configured to purge the device with an airflow to remove fluid and/or contaminants from the device when the impact-generating mechanism is not operating.
13. The device of claim 1 , wherein the pneumatic control system is further configured to provide a gas spring between a lower surface of an upper radial extension of the anvil and an upper surface of a pressure wave outlet.
14. The device of claim 1 , wherein the plurality of valves are located in a control system housing located above the impact-generating mechanism.
15. The device of claim 14 , further comprising one or more pneumatic pilot circuits extending between the cylinder and at least one of the valves of the plurality of valves to provide switching between a purge mode and an operational mode by only controlling an air pressure conveyed into the device past a pre-set pressure threshold.
16. The device of claim 15 , wherein the plurality of valves includes:
a purge valve to switch between the purge mode and the operating mode;
a vent check valve to provide a path to vent air from the device;
an outlet valve to provide a path to vent air from the device and to prevent ingress of fluids into the device; and
a primary control valve to switch between a piston firing mode and a piston return mode.
17. The device of claim 14 , further comprising a filter housing located between the control system housing and the connector, the filter housing provided to filter air entering the device via the conveyor.
18. The device of claim 1 , wherein the plurality of valves includes:
a vent check valve to provide a path to vent air from the device;
an outlet valve to provide a path to vent air from the device and to prevent ingress of fluids into the device;
a primary control valve to switch between a piston firing mode and a piston return mode; and
a pair of solenoid-actuated spool valves under electronic control to actuate the outlet valve and the primary control valve.
19. A system for generating downhole pressure waves, the system comprising:
the device of claim 1 connected to an end of a length of coiled tubing; and
a pressure-controllable air supply unit for conveying pressurized air to the device via the coiled tubing,
wherein the device is configured to switch between a low pressure purge mode and a cycling operating sequence when the air supply unit is controlled to provide an air pressure in the device which is above a pre-determined threshold pressure.