SYSTEM FOR PULSE-INJECTING FLUID INTO A BOREHOLE

• US 20110048724A1
• Filed: 01/19/2009
• Published: 03/03/2011
• Est. Priority Date: 01/17/2008
• Status: Active Grant

• Current Assignee: Wavefront Reservoir Technologies Ltd.
• Original Assignee: Wavefront Reservoir Technologies Ltd.
• Inventors: Mailand, Jason C., Davidson, Brett Charles, Pringle, Ronald E., Warren, John Michael, Samaroo, Mahenrda
• Granted Patent: US 8,316,944 B2
• Time in Patent Office: Days
• US Class Current: 166/320
• CPC Class Codes: E21B 28/00 Vibration generating arrangements for boreholes or wells, e.g. for stimulating production for fishing for or freeing objects E21B31/005; for transmitting measuring-signals E21B47/14; for geophysical measurements G01V1/02
• CPC Class Codes: E21B 43/25 Methods for stimulating production by vibrating earth formations E21B43/003

Abstract

Applying pulses to liquid being injected into wells makes the ground/liquid formation more homogenous, and more penetrative. A system for automatically creating the pulses is described, in which a piston is acted upon by the pressure differential (PDAF) between the supplied accumulator pressure and the formation pressure. The changing levels of the PDAF as the pulse-valve opens (and the PDAF falls) and as the pulse-valve closes (and the PDAF rises) are harnessed to actuate an inhibitor that restrain movement of the valve-piston, and delays opening and/or closing of the pulse-valve. The pulse-valve is engineered to open explosively, and thus create penetrative porosity-waves in the formation. The system includes a pressurized-gas accumulator, and injection-check-valve which can maintain pulsing even when the ground is not saturated, and the static injector, which allows non-pulsed injection only when the ground is non-saturated.

Claims

1. A down-hole tool for pulse-injecting pressurized fluid from a fluid-reservoir out from a hole in the ground into the surrounding ground formation, wherein:

the tool includes a pulse-valve, having a valve-member and a valve-housing;

the valve-member is movable relative to the valve-housing between an open position of the pulse-valve, in which pressurized fluid can pass through the pulse-valve out of the tool and into the formation, and a closed position;

the tool includes an accumulator, which is arranged for storing pressurized fluid from the fluid-reservoir at a magnitude of pressure termed the accumulator-pressure, ready for presentation to the pulse-valve;

the pressure differential between the accumulator-pressure and the hydraulic pressure in the ground formation, termed the formation-pressure, is termed the PDAF;

the tool and the fluid-reservoir are so arranged that, during operation, when the pulse-valve is closed the PDAF increases, and when the pulse-valve is open the PDAF decreases;

the tool includes a valve-cylinder and relatively movable valve-piston;

the valve-piston is so connected to the valve-member as to be movable therewith;

the tool is so arranged that an accumulator-surface of the valve-piston is exposed to the accumulator-pressure, and an oppositely-facing formation-surface of the valve-piston is exposed to the formation-pressure, whereby the valve-piston is subjected to a net force, termed the PDAF-force;

the tool is so arranged that, in operation, the accumulator-pressure being higher than the formation-pressure, the PDAF-force acting on the valve-piston is so directed as to urge the valve-piston to move in the direction to open the pulse-valve;

the tool includes a piston-biasing means, for example a spring, which provides a biasing-force that acts upon the valve-piston in such direction as to close the pulse-valve.

2. As in claim 1, wherein:

the magnitude of the biasing-force is such that there exists, in operation of the tool, an equalization-level of the PDAF;

the equalization-level of the PDAF is a level of the PDAF at which the PDAF-force acting on the piston in the direction to open the pulse-valve is balanced by the biasing-force acting on the piston in the direction to close the pulse-valve;

whereby, when the tool is operated in an environment in which the PDAF varies over a range from a highest level to a lowest level, during the course of pulsing, and when the magnitude of the biasing-force is such that the equalization-level of the PDAF falls within the said range, the tool cycles automatically between an injection-phase in which the pulse-valve is open and fluid is being injected into the formation and the PDAF is falling, and a recovery- or recharge-phase in which the pulse-valve is closed and the PDAF is rising.

3. As in claim 2, wherein:

the tool includes an opening-trigger, which is effective, the pulse-valve having closed, first to prevent the pulse-valve from opening, and then later to release the pulse-valve to open;

the opening-trigger includes an operable opening-inhibitor, which operates in response to the closing of the pulse-valve, and is effective, when operated, to inhibit the pulse-valve from opening;

the opening-trigger includes an operable opening-inhibitor-disabler, which operates in response to the PDAF having increased, over a period of time, to a high-level of the PDAF;

the opening-inhibitor-disabler is effective, when operated, to disable the opening-inhibitor, and to release the pulse-valve to open

4. As in claim 3, wherein:

the opening-inhibitor includes walls that define a dashpot-chamber of variable volume;

the opening-inhibitor is effective to enable the pulse-valve to remain closed, for a period of time, even though the rising PDAF has increased above its equalization-level;

the opening-inhibitor is so arranged that the presence of pressurized fluid in the dashpot-chamber is effective to inhibit movement of the valve-piston in the direction to open the pulse-valve;

the said period of time is determined by the structure of the dashpot;

the walls of the dashpot-chamber include a constricted-port, which is so structured that fluid can only leak out of the dashpot-chamber at a restricted flowrate;

the walls of dashpot-chamber include a wide-port, which is so structured that, when the wide-port is open, fluid can leave the dashpot-chamber therethrough at a rapid flowrate;

the walls of the dashpot-chamber include a recharge-port, through which fluid outside the dashpot-chamber at a higher pressure than fluid already in the dashpot-chamber can enter the dashpot-chamber;

the opening-inhibitor-disabler includes a configuration of the wide-port in relation to the valve-piston such that fluid can only leave the dashpot-chamber through the wide-port after a substantial quantity of fluid has already escaped from the dashpot-chamber through the constricted-port, and after the volume of the dashpot-chamber has substantially decreased;

the period of time starts when, the dashpot-chamber having been refilled, fluid starts to leak out of the dashpot-chamber through the constricted-port; and

the period of time ends when fluid starts to leave the dashpot-chamber at a rapid flowrate through the wide-port.

5. As in claim 4, wherein:

the dashpot-chamber and a recovery-chamber are respective sub-chambers of the inhibitor mechanism;

the constricted-port, the wide-port, and the entry-port, communicate the dashpot-chamber with the recovery-chamber;

the dashpot-chamber and the recovery-chamber together form an inhibitor-chamber of the inhibitor mechanism of the tool;

the inhibitor is so arranged that, during operation, the recovery-chamber is in pressure-equalizing communication with the formation-chamber; and

either

the inhibitor-chamber is an enclosed, sealed, chamber, containing a fixed quantity of a dashpot-liquid, e.g oil;

or

the recovery-chamber of the inhibitor is in open fluid-conveying communication with the formation-chamber, whereby fluid pressure in the recovery-chamber substantially equals the formation-pressure.

6. As in claim 2, wherein:

the tool includes a closing-trigger, which is effective, the pulse-valve having opened, first to prevent the pulse-valve from closing, and then later to release the pulse-valve to close;

the closing-trigger includes an operable closing-inhibitor, which operates in response to the opening of the pulse-valve, and is effective, when operated, to inhibit the pulse-valve from closing;

the closing-trigger includes an operable closing-inhibitor-disabler, which operates in response to the PDAF having fallen, over a period of time, to a low-level of the PDAF;

the closing-inhibitor-disabler is effective, when operated, to disable the closing-inhibitor, and to release the pulse-valve to close;

7. As in claim 6, wherein:

the closing-inhibitor includes walls that define a catchpot-chamber of variable volume;

the closing-inhibitor is effective to enable the pulse-valve to remain open for a period of time, even though the falling PDAF has decreased below its equalization-level;

the closing-inhibitor is so arranged that the presence of reduced-pressure fluid in the catchpot-chamber is effective to inhibit movement of the valve-piston in the direction to close the pulse-valve;

the said period of time is determined by the structure of the catchpot;

the walls of the catchpot-chamber include a constricted-port, which is so structured that fluid can only leak into the catchpot-chamber at a restricted flowrate;

the walls of the catchpot-chamber include a wide-port, which is so structured that, when the wide-port is open, fluid can enter the catchpot-chamber at a rapid flowrate;

the walls of the catchpot-chamber include a recharge-port, through which fluid inside the catchpot chamber at a higher pressure than fluid outside the catchpot-chamber can leave the catchpot-chamber;

the closing-inhibitor-disabler includes the placement of the wide-port in relation to the valve-piston such that fluid can only enter the catchpot-chamber through the wide-port after a substantial quantity of fluid has already entered the catchpot-chamber through the constricted-port, and after the volume of the catchpot-chamber has thereby substantially increased;

the period of time starts when fluid starts to leak into the catchpot-chamber through the constricted-port; and

the period of time ends when fluid starts to enter the catchpot-chamber at a rapid flowrate through the wide-port.

8. As in claim 1, wherein:

the accumulator is located in the tool in close proximity to the pulse-valve;

the accumulator includes an accumulator-resilience, which is so structured that;

—

the volume of the accumulator-chamber is variable in proportion to the accumulator-pressure;

the volume of the accumulator-chamber is variable over substantially the whole range of the accumulator-pressure, being the range over which, during operation of the tool, the PDAF is at its highest or its lowest level, or any level therebetween, including the said equalization-level;

the accumulator-resilience includes preferably an enclosed volume of a pressurized gas.

9. As in claim 1, wherein:

the tool includes an injection check valve (ICV);

the ICV includes an ICV-piston and an ICV-spring;

the ICV includes an ICV-main-conduit through which fluid from the reservoir passes, upon being conveyed to the pulse-valve;

the ICV-piston includes a restrictor or choke, through which the said flow in the ICV-main-conduit also passes;

the choke has a smaller flow-conveying area than the ICV-main-conduit, to the extent that, when flowrate through the ICV-conduit is rapid, a pressure differential develops between the upstream side and the downstream side of the choke, the magnitude of the differential being proportional to the flowrate through the choke;

the ICV-piston is movable in response to the said pressure differential, against the ICV-spring, in such manner as to close an ICV-flow-control-valve;

whereby flowrate through the ICV-conduit is self-inhibiting.

10. As in claim 1, wherein:

the tool includes a static injection sub-assembly (SIS);

the SIS includes an SIS-conduit through which fluid from the reservoir passes, upon being conveyed to the pulse-valve;

the SIS includes an SIS-check-valve which is so structured and located as to enable excess pressure inside the SIS-conduit to emerge into the formation, without passing through the pulse-valve.

11. As in claim 1, wherein the tool includes an accumulator, an ICV, and an SIS, which are arranged, in the down-hole tool, above the pulse valve, and one above the other, preferably in that order.