AU2016277731B2 - Hydraulic Valve - Google Patents

Abstract

Disclosed is a hydraulic power unit. The hydraulic power unit has a hydraulic pump driveable by a stationary engine, and the hydraulic pump is connectable to a mechanical drivehead for driving a downhole pump, the downhole pump for pumping fluid from a well. The hydraulic power unit also has a restriction valve located between the hydraulic pump and the mechanical drivehead for restricting the flow of hydraulic oil to the mechanical drivehead. The restriction valve is automatically adjustable so that the load on the stationary engine driving the hydraulic pump remains at or above a set threshold during pumping of fluid from the well. 8554456_1 (GHMatters) P101912.AU.3 1110 CN C CN CC (DC CD cD

Description

CN C CN CC (DC

CD cD

Operation of a hydraulic power unit

Technical Field

The present disclosure relates to the operation of a hydraulic power unit.

Background

The extraction of oil or gas from a well often involves removing a head of liquid from a well using a pump such as a progressive cavity pump (PCP). The pump can be used to pump water from a well to lower the water table. The operating .0 parameters of the pump can be determined by the amount of water that needs to be removed, the water table height, and the rate at which the water needs to be removed. While the long term rate of water removal and water table height can be estimated, short term variations in water table heights can mean that the torque required by the pump will vary considerably. .5

A hydraulic power unit (HPU) is designed to drive, via a hydraulic circuit, a mechanical drivehead which, in turn, drives the downhole progressive cavity pump. The hydraulic power unit can utilise a stationary internal combustion engine to drive one or more hydraulic pumps in order to provide the necessary power. Due to the inherently variable downhole conditions, the degree of hydraulic power required to turn the mechanical drivehead can fluctuate. A change in the downhole pump load can be translated back to the load on the stationary engine driving the hydraulic pump. For example, any increase in pressure in the water table can reduce the load on the downhole pump, which can also reduce the load on the hydraulic pump. If the load on the hydraulic pump varies beyond set operating parameters, this can have a deleterious effect on the stationary engine driving the hydraulic pump.

Decreasing loads on the stationary engine driving the hydraulic pump can lead to a decrease in engine operating temperatures and sub-optimal lubricity of the engine oil. Should the power demand drop, for instance in low torque, or "free flowing tubing" situations, the engine can be exposed to these low loads. Prolonged exposure to low loads can lead to degradation of certain engine components and, in

1 18710052_1 (GHMatters) P101912.AU.2 some cases, catastrophic engine failure.

It is to be understood that, where prior art is referred to herein, such reference does not constitute an admission that the prior art forms a part of the common general knowledge in the art, in Australia or any other country. Such a reference is also not intended to limit in any way the system as disclosed herein.

Summary

Disclosed is a system for operating a hydraulic power unit. The system .0 comprises a downhole pump. The downhole pump is driven by a mechanical drivehead and is for pumping fluid out of a well. The system further comprises a hydraulic pump which is configured to be driven by a stationary engine. The hydraulic pump is also configured to drive at least the mechanical drivehead of the downhole pump. A restriction valve is located between the hydraulic pump and the .5 mechanical drivehead for restricting the flow of hydraulic oil to the mechanical drivehead. The restriction valve may be a globe valve, butterfly valve, poppet valve or similar. The restriction valve is capable of adjusting the load on the stationary engine driving the hydraulic pump. The restriction valve is configured to be automatically adjusted so that the load on the stationary engine driving the hydraulic o0 pump remains at or above a set threshold during pumping of fluid from the well.

The term "stationary engine" as employed herein is intended to mean that the engine is immobile and does not power or form part of e.g. a moving vehicle. The stationary engine can be operated in situ and does not motivate a vehicle to move. The fluid pumped from the well can be hydrocarbons such as oil or gas, water, or a mixture of water and hydrocarbons such as natural gas.

The set threshold can be a load on the stationary engine in a range of from about 70 to about 80 % of the total available load of the engine. By operating the stationary engine at or above the set threshold, the reliability of the pumping process may be improved and the lifetime of the engine may be increased by reducing exposure of the stationary engine to undesirable low load conditions. Low load conditions can be a load below a value in the range of from about 80 to about 70 %

2 18710052_1 (GHMatters) P101912.AU.2 of the total available load.

The system may further comprise a flow valve. The flow valve can be configured to divert a portion of the hydraulic oil flowing from the hydraulic pump to the drivehead. This arrangement can help to reduce the flow rate of the hydraulic oil reaching the drivehead. A control input signal may be used to adjust the flow valve.

The restriction valve can allow restricted flow or unrestricted flow of hydraulic oil. When the flow of hydraulic oil is restricted by the valve, this can have the effect of .0 increasing the pressure of the oil upstream of the restriction valve. The increase in pressure can cause an increase in the hydraulic power required. In response to the increase in hydraulic power, the load on the stationary engine driving the hydraulic pump can be increased. Thus, closing the restriction valve can increase the load on the engine driving the hydraulic pump. .5

The system may further comprise a means for measuring the load on the stationary engine driving the hydraulic pump during pumping of fluid from the well, such that the measured load is able to provide an input signal to a controller for the restriction valve. The means for measuring the load can be a load reader. The load o0 on the stationary engine can be calculated by multiplying the speed of the mechanical drivehead by the torque output of the drivehead. The amount of flow required though the restriction valve can be determined by a control input signal received from a Programmable Logic Controller (PLC) monitoring the stationary engine. The amount of flow required though the restriction valve can be controlled by a control input signal as written in the PLC, the control input signal being responsive to said input signal provided to the PLC.

The PLC can use a Proportional Integral Derivative (PID) loop to set the position of the restriction valve, and the amount of restriction required. The PID controller can operate to continuously calculate the difference between the set threshold (e.g. 70% load on the engine as measured by the means for measuring) and a measured process variable (the actual load on the engine). The PID controller may attempt to minimise the difference between the two measured values over time by adjustment of the position of the restriction valve. In one embodiment, the

3 18710052_1 (GHMatters) P101912.AU.2 information received from the PID controller can be such that the restriction valve reacts slowly and does not cause a rapid increase in load on the engine. Rapid changes in load can put strain on the engine which can reduce its operational lifetime.

In an embodiment, a pilot valve may be configured to receive the control input signal. The pilot valve can hydraulically adjust the restriction valve. This arrangement can be advantageous when the physical force required to move the restriction valve exceeds that which can be effectively actuated electronically. .0 Also disclosed is a hydraulic power unit. The hydraulic power unit has a hydraulic pump that is driveable by a stationary engine. The hydraulic pump is connectable to a mechanical drivehead for driving a downhole pump, the downhole pump being for pumping fluid from a well. The hydraulic power unit also has a .5 restriction valve located between the hydraulic pump and the mechanical drivehead for restricting the flow of hydraulic oil to the mechanical drivehead. The restriction valve is automatically adjustable so that the load on the stationary engine driving the hydraulic pump remains at or above a set threshold during pumping of fluid from the well. -O The restriction valve can have a body having a longitudinal bore extending therethrough from an opening at one end to a second opening at the opposite end. The body can comprise a number of apertures in the wall forming the body. A flow diverting member in the form of a piston can be positioned within the bore of the body and be movable so as to restrict or allow fluid flow through the valve. A sleeve can be slidably mounted relative to the valve body for movement along the body to cause some or all of the apertures to be open or closed to fluid flow. The piston and the sleeve can be used to allow restricted or unrestricted flow of hydraulic oil through the restriction valve.

The hydraulic power unit may further comprise a flow valve. The flow valve may be configured to divert a portion of the hydraulic oil flowing from the hydraulic pump to the drivehead so as to reduce the flow rate of the hydraulic oil reaching the

4 18710052_1 (GHMatters) P101912.AU.2 drivehead.

Also disclosed is a method for operating a hydraulic power unit. The method comprises the step of allowing a fluid to be pumped from a well using a downhole pump driven by a mechanical drivehead. The mechanical drivehead is driven by a hydraulic pump driven by a stationary engine. The method also comprises the step of determining a set load threshold for the stationary engine driving the hydraulic pump, The method further comprises controlling by restricting the flow of hydraulic oil between the hydraulic pump and the mechanical drivehead. The method additionally .0 comprises automatically adjusting the restriction to the flow of hydraulic oil to maintain the load on the stationary engine at or above the set threshold during pumping of fluid from the well.

In the method the restriction on the flow of hydraulic oil between the hydraulic .5 pump and the mechanical drivehead may be provided by a restriction valve located between the hydraulic pump and the mechanical drivehead. The restriction valve can be controlled so as to for restrict the flow of hydraulic oil to the mechanical drivehead.

o0 In the method the step of automatically adjusting the restriction to the flow of hydraulic oil may be effected by automatically adjusting the restriction valve to thereby maintain the load on the stationary engine at or above the set threshold during pumping of fluid from the well.

The method may include the step of sending a control input signal from a PLC to the restriction valve. If the load on the stationary engine driving the hydraulic pump needs to be increased, then the hydraulic oil flow through the restriction valve can be restricted. If the load on the stationary engine needs to be decreased, then the hydraulic oil flow through the restriction valve can be increased.

The method may further include the step of measuring a load on the stationary engine driving the hydraulic pump during pumping of fluid from the well such that the measured load is able to provide an input signal to a controller for the restriction valve. The load on the stationary engine can be calculated by multiplying

5 18710052_1 (GHMatters) P101912.AU.2 the speed of the mechanical drivehead by the torque output of the drivehead.

The method may further include the step of opening a relief valve if the hydraulic pressure of the hydraulic oil increases to a pre-determined maximum system pressure. The maximum system pressure may be in the range of from about 150 to 250 bar, for example 180 to 200 bar. The relief valve can ensure that any restriction applied to the system by the restriction valve does not cause system failure. The method can include the step of closing the restriction valve and entering a HOLD mode when the hydraulic pressure reaches the set maximum system .o pressure. In HOLD mode, the restriction valve can be held in the closed position. This may result in an engine load less than about 70% in some cases. The load on the drivehead can be measured while the restriction valve is in the HOLD mode and if the actual load increases to be greater than 5 % above the desired load, the restriction valve can be instructed to leave HOLD mode and open the valve to .5 reduce the restriction.

The method may include the step of starting the stationary engine remotely. The stationary engine can be allowed to run for a period of time before the system starts to monitor the load on the stationary engine. In one embodiment, the stationary engine must reach the set threshold of load before the restriction valve is activated. In one embodiment, the restriction valve does not receive any signals from the PLC until at least about 30 seconds after the stationary engine has been started.

The method may comprise the step of diverting a portion of the hydraulic oil flowing from the hydraulic pump to the drivehead. Diverting a portion of the hydraulic oil may help to reduce the flow rate of the hydraulic oil reaching the drivehead.

The system, hydraulic power unit and method can be used to provide hydraulic power for coal seam gas wells. The coal seam gas wells may be located in remote locations with extreme environments such as high temperatures. Use of the restriction valve can help to increase the service intervals, which may help to reduce maintenance costs, especially for hydraulic power units used in remote locations.

Brief Description of Figures

6 18710052_1 (GHMatters) P101912.AU.2

Embodiments will now be described by way of example only with reference to the accompanying non-limiting drawings in which:

Figure 1 is a schematic of a hydraulic power unit.

Figures 2 are isometric and end-on views of an embodiment of a physical form of the valve system.

Figure 3 is a schematic of a hydraulic circuit. .o Figure 4 is a flow diagram of a process.

Figure 5 is a schematic of a hydraulic circuit.

.5 Figure 6 is a schematic of a hydraulic circuit for powering a drivehead with a hydraulic power unit.

Figure 7 is a flow diagram of a process for controlled a hydraulic power unit.

o0 Figure 8 is a flow diagram of a process for controlled a hydraulic power unit.

Figure 9 is a schematic of a hydraulic circuit for powering a drivehead with a hydraulic power unit.

Detailed Description

Figure 1 is a schematic of a hydraulic power unit 10 in which there is an enclosure 12 housing a stationary Internal Combustion Engine (ICE) in the form of engine 24. The engine 24 is connected to a hydraulic pump in the form of first pump 21. First pump 21 is connected by a hydraulic conduit 17 to a drivehead 32 for driving a downhole pump in a well (not shown). The fluid pumped out of the well by the downhole pump is generally a liquid. The liquid can be oil. The liquid can be water. The liquid can be a combination of oil and water. The oil can contain a

7 18710052_1 (GHMatters) P101912.AU.2 proportion of gas hydrocarbons. The fluid(s) pumped out of the well in some embodiments are those commonly found in coal seam gas wells.

In Figure 1, the hoses and cables for connection to the downhole pump are omitted from the Figure for the sake of clarity. In some embodiments a second hydraulic pump such as a booster pump 21'can be provided. The booster pump 21' can be used if required to transfer fluids pumped from a well to other locations. Therefore, the hydraulic power unit 10 can be used to drive pumps located in different wells and/or fluids from one location to another. .0 Air is drawn into the enclosure 12 via an inlet 14 and exhausts through outlets 16, 16'. The engine 24 also drives a fan 22 to provide cooling to fluids circulating in the unit 10. The type of fan 22 and the rate of cooling is generally determined by the type of the engine 24, the location of the intended use of the engine 24, and the .5 intended load profiles of the engine 24. Coolant from the engine 24 can be cooled in heat exchanger 20. Hydraulic oil is cooled by flowing through a heat exchanger 18. The air is drawn in over the heat exchangers 18, 20 and passes upwardly through a vent or hood 16a and can be exhausted through any number of outlets 16, 16'which are generally disposed towards the upper side of the enclosure. Other airflow paths O are used in some embodiments, and the airflow path is generally determined by the rate of required cooling and the arrangement of the components in the hydraulic power unit 10.

A restriction valve in the form of a valve 23, that operates in the hydraulic oil circuit to restrict the flow of hydraulic oil, is located between the first pump 21 and the drivehead 32. In the embodiment of Figure 1, only one valve 23 is fitted between the pumps 21 and 21'and the drive head. In some embodiments, each pump (21, 21' etc.) is fitted with a valve 23.

Figure 2A and Figure 2B show an embodiment of a physical form of the valve 23. In this embodiment, first pump 21 and booster pump 21' are connected along a common longitudinal axis defined by a shaft of each pump, as represented by dashed line 19. The first pump 21 is fitted with valve 23. Valve 23 has a manifold, defined in part by face 23a, that is directly bolted to a pump outlet port of pump 21.

8 18710052_1 (GHMatters) P101912.AU.2

The use of a manifold helps to reduce the number of hoses and fitting connections required between the valve 23 and pump 21. The consolidation of hydraulic fittings in the system can also reduce the number of potential leak points as well as noise. However, in some embodiments the valve 23 is connected to the pump outlet port via hosing such as hydraulic hosing. In embodiments where hosing is used, a manifold may not be required.

In Figure 3, there is shown a simplified schematic of a hydraulic circuit 30 of the hydraulic power unit 10. The circuit includes the mechanical drive from the .0 stationary engine 24, first pump 21, the valve 23 and the hydraulic motor on the drivehead 32. The circuit also has a hydraulic oil tank 35. While only first pump 21 is described, the same principles apply for booster pump 21', or any additional pump associated with the engine 24. The drivehead 32 drives the downhole pump that is located at the bottom of a well that pumps fluids out of the well. In the circuit the .5 valve 23 is located between the hydraulic motor on the drivehead 32 and the first pump 21 from the stationary engine 24. The valve 23 can also be referred to as an artificial load valve because it acts to artificially increase the load on the stationary engine.

o0 In this regard, the valve 23 is configured to allow restricted flow or unrestricted flow of hydraulic oil in the circuit. When the flow of hydraulic oil is restricted by the valve, this has the effect of increasing the pressure of the oil upstream of the valve 23 (i.e. on the first pump 21 and in turn on the stationary engine 24). The increase in pressure can cause an increase in the hydraulic power required. In response to the increase in hydraulic power, the load on the stationary engine 24 driving the first pump 21 is increased. Thus, closing the valve 23 can increase the load on the engine 24 driving the first pump 21. The presence of the valve 23 in the hydraulic circuit can thereby function to improve the safety of the pumping process. In this regard, the valve can remove, or at least reduce, the need for manual human intervention to move/activate the valve. This is because opening and closing of the valve can be controlled as part of an automatic control procedure. In this regard, the valve 23 can also increase the reliability of the downhole pumping process by reducing the exposure of the engine of the hydraulic pump to low load conditions.

9 18710052_1 (GHMatters) P101912.AU.2

When operating at low loads, the running conditions of the engine 24 may not be optimal. For example, the engine 24 may run at a temperature that is lower than recommended. When non-optimal running conditions are encountered, the engine 24 can be susceptible to premature damage. For example, cooler running conditions can cause engine seals to not perform adequately, and this can lead to unwanted ingress of oil, which decreases the life of the engine.

The stationary engine 24 is preferably operated at a load above low-load conditions. The stationary engine 24 is preferably operated at its optimal load or .0 above. Prolonged exposure to low loads can lead to degradation of certain engine components and, in some cases, catastrophic engine failure. The stationary engine 24 can have optimal operating parameters which can be referred to as the "set operating parameters". The set operating parameters can include a set load threshold. The engine load can be calculated by multiplying the speed of the .5 drivehead 32 (or the booster-pump) by the torque output of the drivehead (or the booster-pump motor). The calculated engine load can be used to generate a control input signal to valve 23. The set load threshold can be a load on the engine in a range of from about 70 to about 80 %, for example about 75 to 78 % of the total available load of the stationary engine. Valve 23 can be adjusted between a fully or o0 partially open position and a fully or partially closed position in an attempt to keep the load on the engine at or above the set threshold during pumping of fluid from the well. By constantly adjusting valve 23, the load on the engine may be kept substantially constant around the set operating parameters. By "substantially constant" it is meant that the load on the stationary engine can be kept within the range of at least about 1 to about 15 % of the set threshold, for example, about 5 to 10 % of the set threshold.

To determine the load on the engine, the hydraulic circuit 30 includes a means 33 for measuring the load on the engine 24. The means can include pressure sensors located in one or more conduits upstream of the drivehead 32 (not shown). Since the pressure of a fluid is determined in part by its temperature, the means can also include sensors that determine temperature including temperature fluctuations. Sensors that determine the flow rate of the hydraulic oil can also be used to determine the engine load. Because the hydraulic power unit is intended to be

10 18710052_1 (GHMatters) P101912.AU.2 operated for extended periods of time, the hydraulic oil may degrade over the period. Degradation of hydraulic oil often causes the viscosity of the fluid to increase, which affects the operational pressure of the hydraulic oil. Therefore, the means may also include viscosity sensors. Whatever sensor(s) are used, they can be used to provide an input signal to a controller for valve 23 (described below).

The means 33 for measuring the load can be a load reader. When a load reader is used, the means 22 calculates the load on the engine 24 and may be calculated by multiplying the speed of the drivehead 32 by the torque output of the .0 drivehead 32. The means 33 can calculate a load on the engine 24 by multiplying the speed of the mechanical drivehead by the torque output of the drivehead.

In an embodiment, the valve 23 allows free flow of the fluid in one direction and restricted flow in the opposite direction. Generally the valve 23 functions as a .5 pressure regulator. The pressure regulator includes a restricting element and a loading element. The restricting element is a valve that provides a variable restriction to the flow, such as a globe valve, butterfly valve or a poppet valve. The loading element is a part that applies the needed force to the restricting element. This loading can be provided by a weight, a pressure (e.g. gas or fluid), a spring, a piston O actuator, or a force.

In one embodiment, valve 23 is in the form of valve 400, as shown in Figure 10. The top half of valve 400 is shown as being cut away above centreline 401 to reveal the internal features of valve 400. Valve 400 has a body 402 having a longitudinal bore extending therethrough from an open end 406. The valve body comprises a number of apertures 408 in the wall forming the body 402. The apertures 408 are in fluid communication with open end 406. A flow-diverting member in the form of a piston 414 is positionable within the bore 402 and is movable so as to restrict or allow fluid flow through the valve by blocking one or more apertures 408. Alternatively, a sleeve is mounted relative to the valve body for movement along the body to cause some or all of the apertures to be open or closed (not shown).

This arrangement (or other known valve arrangements) allows for the

11 18710052_1 (GHMatters) P101912.AU.2 controlled flow of fluid flow through the valve in both directions. The valve 23 is activated to be fully closed, and deactivated to be fully open. Alternatively, the valve 23 is deactivated to be fully open and activated to be fully closed. In any case, the valve can be activated or deactivated to be at any stage in between open or closed. The valve can be automatically, incrementally opened and/or closed. The open or closed (or partially opened or partially closed) condition of the valve can affect the load on the stationary engine driving the hydraulic pump.

In an embodiment, valve 400 can take the form of a solenoid valve. Activation .0 of the solenoid either closes or opens the apertures 408. Valve 400 is a normally closed, electro-proportional throttle valve that is spring-biased closed (spring 418). A solenoid coil is positioned in head 416. Energizing the coil via an input signal e.g. 31 generates an opening force on the so-called spool, i.e. on piston 414, proportional to the command current, and this force is countered by spring 418 as well as fluid flow .5 forces. This balance of forces enables the valve 400 to, in effect, provide a metering orifice whose effective size is proportional to the current. In an alternative embodiment, an actuator is positioned within head 416 for operation of piston 414.

Valve body 402 is fitted within a manifold 410 that defines conduit 412. o0 Manifold 410 can be milled from a block of metal, such as stainless steel, or can be located at a fitting at the end of a hydraulic hose. The manifold 410 also has conduits 420a and 420b that are in fluid communication with apertures 408. When the apertures 408 are open, hydraulic oil flowing through conduit 412 can flow in through the open end 406, into the bore located in the body 402, out of apertures 408 and into conduits 420a and 420b. The hydraulic oil can also flow in the opposite direction. It should be noted that in some embodiments conduit 420b is absent from manifold 410.

In the embodiment described, in order to affect a restricted flow of e.g. hydraulic oil, at least some of the apertures in valve 400 are closed. This has the effect of increasing the resistance to flow of hydraulic oil, which can increase the pressure of the oil upstream of valve 400. The increase in pressure causes an increase in the hydraulic power required. Hydraulic power is the pressure of the hydraulic oil multiplied by the flow rate of the hydraulic oil. Higher hydraulic power

12 18710052_1 (GHMatters) P101912.AU.2 requires higher engine power, and therefore increases the load on the engine driving the hydraulic pump. Thus, closing the valve increases the load on the engine driving the hydraulic pump. Alternatively, the valve 23 can allow relatively unrestricted flow of e.g. hydraulic oil. The unrestricted flow occurs by opening at least some of the apertures in the valve to allow relatively unrestricted flow through the valve. Decreasing the resistance to flow of hydraulic oil decreases the pressure of the oil upstream of valve 23. The decrease in pressure can cause a decrease in the hydraulic power required and therefore decreases the load on the engine driving the hydraulic pump. Thus, opening the valve 23 decreases the load on the engine .o driving the hydraulic pump. The valve 23 may be sequentially opened (unrestricted) and closed (restricted) in response to the engine load. The valve 23 may be partially or fully opened, or partially or fully closed. The valve 23 adds an artificial load to the engine in an attempt to operate the engine within its ideal set operating parameters.

.5 In some circumstances, the drivehead 32 needs to be run at low speeds e.g. <200 RPM, which requires a low flow rate of hydraulic oil being pumped from the hydraulic power unit to the drivehead 32. When the drivehead 32 is run at low speeds, the load placed on engine 24 can be reduced past the set load threshold. To keep the load on the engine 24 above the set threshold, the valve 23 closes to restrict the flow of the hydraulic oil to increase the load on the engine 24. However, in some situations, the low flow rate cannot be achieved whilst having the engine load being greater than 70%.

To account for this, in some embodiments the valve 23 is equipped with a flowback conduit 34 in communication with a flow valve. The flow valve can take the form of flowback valve 36, as shown in Figure 6. The flowback valve 36 in some embodiments can also comprise the solenoid valve 400. The flowback valve 36 can be considered an artificial load flow valve. In the embodiment of Figure 6, some of the flow of hydraulic oil from the first pump 21 to the drivehead 32 is able to be diverted to hydraulic oil tank 35 through the flowback conduit 34 when flowback valve 36 is open. This arrangement allows for a high flow rate of hydraulic oil at the first pump 21 to be passed through valve 23, but some of the flow of hydraulic oil downstream of valve 21 is then allowed to be diverted through flowback valve 36, which lowers the flow rate of the hydraulic oil being pumped to drivehead 32

13 18710052_1 (GHMatters) P101912.AU.2 compared to the flow rate of the hydraulic oil at the first pump 21. In this way, a high flow rate at the first pump 21 can be achieved whilst having a low flow rate at the drivehead 32. The flowback conduit 34 can be a bore or passage formed in e.g. a manifold, or a pipe such as a hydraulic pipe. When a hydraulic pipe is employed, it would be appreciated by a person of ordinary skill that there are many ways in which the hydraulic pipe can be attached to the various components e.g. first pump 21, which are all included within the scope of this disclosure.

Generally, the flowback valve 36 is opened when the operational speed of the .0 drivehead 32 is less than approximately 200 RPM. The flowback valve can be deactivated to be fully open and activated to be fully closed. Alternatively, the flowback valve can be activated to be fully open and deactivated to be fully closed. In any case, once the speed of the drivehead 32 is above 200 RPM, the flow rate of hydraulic oil at the pump is sufficient for engine loads to be greater than 70% by .5 restriction of the valve 23 only. Therefore, once the drivehead 32 is running at speeds of greater than 200 RPM, the flowback valve 26 is closed. In this way, the presence of flowback conduit 34 and flowback valve 36 forms two hydraulic oil circuits in respect of valve 23, a first circuit running from the first pump 21 through valve 23 to drivehead 32 and back to the hydraulic oil reservoir 35, and a second o0 circuit running from the first pump 21 through valve 23 and back to the hydraulic oil reservoir 35 via flowback valve 36. These two circuits are interconnected and are controllable to ensure that the set load threshold of the engine 24 is in a range of from about 70 to about 80 %. In some embodiments the RPM threshold for the flowback valve 36 is greater than 200 RPM, and will be determined by the type of drivehead, the engine 24 and the well type and well conditions. In some embodiments, the RPM threshold is less than 150 RPM. In some embodiments, the RPM threshold is greater than 200 RPM, such as 250 RPM.

Including flowback conduit 34 and flowback valve 36 can allow the hydraulic power unit 10 to power a wide variety of hydraulic motors, for example, the drivehead 32 when used in a variety of wells. For example, for wells with unstable water tables that rise and fall uncontrollably, the use of flowback conduit 34 and flowback valve 36 allows the engine 24 to continually run at loads of about 70% or more and thereby minimise engine load fluctuations, regardless of the status of the

14 18710052_1 (GHMatters) P101912.AU.2 water table. The flowback valve 36 is controllable using Programmable Computer Logic via input 42, as will be described below.

Figure 5 shows is a hydraulic circuit 60 showing the circuits comprising first pump 21 driving a hydraulic motor on the drivehead 32, and booster pump 21' driving a hydraulic motor of an auxiliary booster pump 32'. The booster pump 32' can increase the pressure of the produced fluid (water or oil) to propel the fluid through pipelines to a processing facility. The valve 23, shown as a dashed box, includes subcomponents such as pilot operated relief valve 70 in fluid communication with .o proportional relief valve 68. The pilot operated relief valve 70 is configured to be operated to open the proportional relief valve 68 when the engine load passes a predetermined value. The pilot operated relief valve 70 is some embodiments can also comprise the solenoid valve 400. In other embodiments, pilot operated relief valve 70 is operated using pilot hydraulic pressure. A proportional valve 72 is fitted .5 upstream of the pilot operated relief valve 70 and helps to regulate the hydraulic pressure and/or flow rate prior to reaching the proportional relief valve 68.

A relief valve 73 is included in valve 23. The relief valve 73 in this embodiment is located in the manifold defined by valve 23. In some embodiments, however, the relief valve 73 is located elsewhere in the circuit 60, e.g. between valve 23 and drivehead 32. The relief valve has a threshold value higher than the maximum operating system pressure, but within the envelope of the maximum system pressure of the weakest point in the system. The maximum system pressure is the pressure at which the system cannot tolerate the conditions for a sustained period of time. The control system including the PLC can prevent the valve 23 from restricting the hydraulic pressure to a value that exceeds a maximum operating system pressure by monitoring the hydraulic pressure. However, the relief valve 73 is provided as a failsafe in the event that an over-pressure situation occurs, such as when the pressure compensator already included in the pump fails to operate (or has been set incorrectly).

Conduit 74 connects components of valve 23 with drivehead 32. A bypass valve 66 is positioned between the drivehead 32 and the pilot operated relief valve 70 and proportional relief valve 68. The bypass valve 66 is configured to provide a

15 18710052_1 (GHMatters) P101912.AU.2 flow path to allow the hydraulic oil to be diverted from travelling down conduit 74, and instead return via common return conduit 82 to the hydraulic oil tank 64. Hydraulic oil will only bypass drivehead 32 if the bypass valve 66 is open. Once hydraulic oil has passed through the drivehead 32, it flows through conduit 76 and into common return conduit 82. Apparatus for further hydraulic oil processing, such as hydraulic oil cooling and filtering is represented generally by box 62 and is positioned on common return conduit 82. The type of further hydraulic oil processing will be determined by the hydraulic oil used, the load(s) on the engine 24 and the environmental factors affecting the circuit 60 e.g. external temperature. .0 Valve 85 is also provided on conduit 78 that is in communication with booster pump 21' and the hydraulic motor for an auxiliary booster pump 32'. Valve 85 has a proportional valve 84 similar to valve 72, and valve 86 that is a relief valve similar to valve 73. Conduit 78 is in communication with booster pump 32'. Once the hydraulic .5 oil has passed through booster pump 32', it then flows downstream through conduit 80 before joining common return conduit 82.

The amount of flow required though the valve 23 in some embodiments is determined by a control input signal. The control system that sends the control input '0 signal can be written in a Programmable Logic Controller (PLC). The PLC can be an automotive engine controller. The PLC can be an InteliDrive ID-Mobile expandable automotive engine controller. The PLC can use a Proportional Integral Derivative (PID) loop to set the position of the valve 23, and the amount of restriction required. The PID controller is configured to minimize the difference between the two measured values over time by adjustment of the position of valve 23. The set points of the PID are such that the valve 23 reacts slowly and does not cause rapid increases in load on the engine. The load can be increased by a 2 to 10 RPM, optionally 3 to 4 RPM over 10 to 30 seconds, optionally 10 to 15 seconds. The PLC can be associated with one or more computers.

In an embodiment, the engine has an Electronic Control Unit (ECU). The ECU measures the engine load and feeds this data as an input signal to the PLC. The PLC can then send a control input signal to valve 23 and/or to flowback valve 36. If the load on the engine driving the hydraulic pump 21 needs to be increased, then a

16 18710052_1 (GHMatters) P101912.AU.2 control input signal e.g. 31 in Figs. 3 & 6 can be received by valve 23 to cause the hydraulic oil flow through it to be restricted. If the load on the engine driving the hydraulic pump needs to be decreased, then control input signal 31 is received by valve 23 to cause the hydraulic oil flow through it to be increased. In some embodiments, the valve 23 comprises a pilot operated valve 70 and proportional relief valve 68. Pilot operated valve 70 receives the control input signal 31. Upon receiving the control input signal, the pilot operated valve 70 then sends a signal to the proportional relief valve 68. In some embodiments, the signal from the pilot operated valve 70 is communicated hydraulically. This arrangement may be .0 necessary when the proportional relief valve 68 is not responsive enough to an electrical signal and instead requires hydraulic actuation. In other embodiments, the proportional relief valve 68 is controlled via an actuator, e.g. linear or rotational actuator, or other similar mechatronics. The type of actuator will be determined by the type and in-use loads of the proportional relief valve 68. A pilot operated relief .5 valve 70 will generally be used when the pressures on the proportional relief valve 68 are too great for use of an actuator.

With reference to Figure 3, the PLC generates an input 31 signal that is delivered to valve 23. Depending on the information contained in input signal 31, the o valve 23 will remain in its current state, or open or close to adjust the engine load. Likewise, with reference to Figure 6, the PLC generates an input signal 42 to the flowback valve 36. The flowback valve 36 will either remain in its current state, or open or close in response to the information contained in signal 42. While signal 31 and 42 have been shown as two separate signals, in some embodiments they can be delivered to valve 23 in the same data packet. When solenoid valve 400 is employed, input signal 31 and/or 42 are electrical inputs that activate the coil housed in head 416. Alternatively, input signals 31 and/or 42 can function to adjust hydraulic pressures, for example using electromechanical means, to operate valves such as the pilot operated valve 70.

Figure 4 is a flow diagram of the logic in the controller of a control system 100. The control system 100 starts the engine 24 at the beginning of the process at step 105. The engine 24 can be started remotely through e.g. a wireless server network. Alternatively, the engine 24 is started manually by an operator. The control system

17 18710052_1 (GHMatters) P101912.AU.2

100 can be programmed to commence only once the engine 24 has successfully started and has been run for a set time, adjustable by a set point. Alternatively, the engine 24 can be allowed to run for a period of time before the system starts to monitor the load on the stationary engine. The control system 100 monitors the state of the engine 24 and can be programmed to only enable the valve 23 to function once the engine 24 has reached "nominal" condition. Nominal condition is when the engine has reached equilibrium and is running normally. In one embodiment, the engine 24 must reach the set threshold of load before the valve 23 is activated.

.0 If conditions are correct following starting the engine, the control system will be initiated at step 110. The system 100 then begins to determine loads on the engine 24 using the steps defined in dashed box 150. The load on the stationary engine is first measured at step 115. If an engine load less than the desired set point (e.g. 70%) is determined at step 120, the control system 100 proceeds to determine .5 if there is a speed differential between the actual downhole progressive cavity pump (PCP) speed and the desired speed at step 125. If it is determined at step 125 that the speed desired from the drivehead 32 is more than a certain number of RPM different from the PCP, such as 20 RPM, an input signal is directed to the valve 23 to slowly open the valve until the desired engine load is reached. The speed difference o can be when the drivehead is running at an RPM in the range of from about 5 to 25 RPM, optionally about 20 RPM different from the PCP.

Interactions with other valves in the hydraulic circuit can cause situations where the desired speed required from the drivehead to impart load on the engine driving the hydraulic pump is higher than the actual speed of the drivehead. Effectively, the drivehead is running too slowly. If there is no speed differential determined at step 125, the system proceeds to determine if the hydraulic pressure has reached the HOLD pressure at step 130. If the pressure is at or above the hold pressure, an input signal is received by valve 23 to be held in the closed position at step 140. If the pressure at step 130 is below the HOLD pressure, an input signal is received by valve 23 to be closed at step 135. The load on the drivehead 32 can be measured while the valve 23 is in the HOLD mode by repeating step 115. If the actual load increases to be greater than 5 % above the desired load, as determined at step 120, the valve can be instructed at step 145 to leave HOLD mode and open

18 18710052_1 (GHMatters) P101912.AU.2 to reduce the restriction and thus engine load.

Figure 7 shows another embodiment of a control system 200. The control system 200 takes into account whether or not the PCP speed is less than 200 RPM. Therefore, system 200 controls flowback valve 36, as described in Figure 6, and valve 23. In system 200, engine 24 is started at step 205. The control system is then initiated at step 210, similar to that of system 100. The system 200 then determines if the PCP speed is less than 200 RPM at step 215. If the PCP is less than 200 RPM, the engine load is measured at step 220, and if it is not less than the set threshold .0 e.g. 70%, flowback valve 36 is instructed to close at step 240. If, however, it is determined at step 225 that the engine load is less than the set threshold, the system then determines if the PCP speed is more than a set threshold e.g. 200 RPM at step 230. If the PCP is more than the threshold, the flowback valve 36 is instructed to close at step 240. If the PCP is less than the threshold, the flowback .s valve 36 is instructed to open at step 235. After steps 235 and 240, the control system goes back to determine if the PCP is less than 200 RPM at step 215. If at step 215 it is determined that the PCP speed is greater than 200 RPM, the load on the engine 24 is determined using the steps within the dashed box 150 in Figure 4. In any case, the control system 200 always determines the RPM of the PCP prior to adjusting valve 23 and/or flowback valve 36.

In some embodiments, system 200 returns to step 220 after steps 235 and 240 rather than step 215. In these embodiments, the system is configured to determine the RPM of the PCP at step 215 at predefined time points, for example once every 1-60 minutes, such as every 30 minutes. If the answer to step 215 provides an opposite answer to a current status at one of these predefined time points, such as the PCP RPM is now greater than 200 RPM, the control system 200 will proceed according to the new information. This helps to ensure that the load placed on the engine 24 is done most efficiently.

In some embodiments, the logic loop, i.e. control system 100 or 200, is repeated continuously until one of the decisions returns an opposite answer, or the engine 24 is stopped, or the control system 100 is disabled. Alternatively, the control system 100 or 200 is run at regular time intervals. The engine 24 and/or control

19 18710052_1 (GHMatters) P101912.AU.2 system 100 can be stopped or disabled remotely or manually. If, during any loop, the load is greater than the desired set-point, the valve 23 will be opened. If during any loop there is a downhole pump speed differential, the valve 23 will be opened.

Any data generated during use of the hydraulic power unit 10 can be sent to a data logger (not shown). The data logger allows an operator to track the performance of the hydraulic power unit 10, which can assist when determining events such as maintenance and key well conditions. The data logger can be housed in the hydraulic power unit 10. Alternatively, the data logger can be housed .0 offsite and data is sent to the data logger using e.g. wireless communication.

The various variables and signals that affect the engine load is summarised in Figure 8. A load set point is selected e.g. 70% and is fed as an input into the controller at 305. Controller output signal is used to adjust the various valves e.g. .5 valve 23 and flowback valve 36. The valve adjustments etc. are considered manipulated variables. During adjustment of the valves, disturbances in the well, such as movement in the water table, changes in the downhole load and/or speed of the downhole pump, affect the engine load. At a set point after the valves have been adjusted, the engine load is measured and is fed as an input into the controller. The o engine load is considered a process variable. If the engine load is less than the set point e.g. <70%, the cycle is continued until the engine load is at least equal to the set point. If the cycle is unable to adjust the engine load to at least 70%, a wireless signal may be sent to an operator to indicate a fault with the hydraulic power unit. Wireless communication between the hydraulic power unit, e.g. PLC and data logger, and an operator may be via 3G, 4G, 5G, Wi-Fi, Bluetooth and/or satellite communication.

The maximum system pressure can be in the range of from about 150 to 250 bar, optionally about 200 bar. The control system can prevent the valve from restricting the hydraulic pressure to a value that exceeds a maximum system pressure by monitoring the hydraulic pressure. When the system is stopped, a poppet valve or bypass valve can be de-energised and any pressure in the outlet line of the hydraulic pump that is present can be allowed to bleed away at a controlled rate. Control system 100 or 200 can optionally instruct the relief valve 73 to open.

20 18710052_1 (GHMatters) P101912.AU.2

However, the relief valve 73 generally automatically opens in response to pressures exceeding set upper limits.

Figure 9 shows another hydraulic circuit 90. Hydraulic circuit 90 is similar to hydraulic circuit 60 described in Figure 5, but with the flowback valve 36 and conduit 34 (as described in Figure 6). Flowback valve 36 is positioned on conduit 34 between the pilot operated relief valve 70 and proportional relief valve 68, and bypass valve 66. When the flowback valve 36 is opened, a portion of the hydraulic oil flowing through conduit 74a is allowed to flow through conduit 34 and back into the .0 hydraulic oil tank 64. The proportion of the flow that is diverted back to tank 64 via conduit 34 is determined by the flow rate through conduit 74a, the valve 36 and how close it is to be fully opened or fully closed. If flowback valve 36 is closed, then no hydraulic oil flows through conduit 34.

.5 Example The Hydraulic pump unit 10 was operated according to the circuitry shown in Figure 5 and the following data was calculated:

• Drivehead speed: 350 RPM • Drivehead Torque: 300 ft-lbs • Engine size: 5.7L * Maximum Engine Power: 77 HP * Drivehead motor size 4.91ci/rev * Drivehead gear ratio: 4.63:1 • Hydraulic Motor Mechanical Efficiency: 95% * Hydraulic Motor Volumetric Efficiency: 97% * Hydraulic Pump Mechanical Efficiency: 95%

Hydraulic Pressure =(Torque * 75) / (Motor size * Gear Ratio* Motor Mechanical Efficiency)

=(300 * 75) / (4.91 * 4.63 * 0.95)

= 1042.6 psi

21 18710052_1 (GHMatters) P101912.AU.2

Drivehead Motor Speed = Drivehead speed * Gear Ratio

= 350 * 4.63

= 1621 RPM

Hydraulic Flow Rate = (Motor Size* Motor Speed / Motor Volumetric Efficiency)/ 231

= (4.91 * 1621 0.97) /231

= 35.5 us GPM

Hydraulic Power = Hydraulic Pressure * Hydraulic Flow Rate / 1714

= 1042.6 * 35.5 / 1714

.0 = 21.6 HP

Engine Power = Hydraulic Power / Hydraulic Pump Mechanical Efficiency

= 21.6 /.95

= 22.7 HP

Percentage Engine Load = Engine Power/ Maximum Engine Power

.5 = 22.7 / 77

= 30%

In this case the valve will close until the hydraulic pressure is 2488 psi:

Hydraulic Power = Hydraulic Pressure * Hydraulic Flow Rate / 1714

= 2488 * 35.5 / 1714

= 51.5 HP

Engine Power = Hydraulic Power / Hydraulic Pump Mechanical Efficiency

= 51.5 /.95

= 54.2 HP

22 18710052_1 (GHMatters) P101912.AU.2

Percentage Engine Load = Engine Power/ Maximum Engine Power

= 54.2 / 77

= 70%

It will be understood to persons skilled in the art that many modifications may be made without departing from the spirit and scope of the disclosure.

In the claims which follow and in the preceding description of the system, apparatus and method as disclosed herein, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or .0 variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the system, apparatus and method as disclosed herein.

23 18710052_1 (GHMatters) P101912.AU.2

Claims (20)

Claims

1. A system for operating a hydraulic power unit, the system comprising: a downhole pump, wherein the downhole pump is configured to be driven by a mechanical drivehead and is for pumping fluid out of a well; a hydraulic pump, driveable by a stationary engine, wherein the hydraulic pump is configured to drive at least the mechanical drivehead of the downhole pump; a restriction valve located between the hydraulic pump and the .0 mechanical drivehead for restricting the flow of hydraulic oil to the mechanical drivehead, wherein the restriction valve is capable of adjusting the load on the stationary engine driving the hydraulic pump; wherein the restriction valve is configured to be automatically adjusted so that the load on the stationary engine driving the hydraulic pump remains .5 at or above a set threshold during pumping of fluid from the well.

2. The system according to claim 1, wherein the set threshold is a load on the stationary engine in a range of from about 70 to about 80 % of the total available load on the engine. -o

3. The system according to claim 1 or 2, wherein the system further comprises: a flow valve that is configured to divert a portion of the hydraulic oil flowing from the hydraulic pump to the drivehead so as to reduce the flow rate of the hydraulic oil reaching the drivehead; and a means for measuring the load on the stationary engine driving the hydraulic pump during pumping of fluid from the well, such that the measured load is able to provide an input signal to a controller for the restriction valve.

4. The system according to claim 3, wherein the controller is a Programmable Logic Controller (PLC), and wherein the amount of flow required though the restriction valve is controllable by a control input signal as written in the PLC, the control input signal being responsive to said input signal provided to the PLC.

24 18710052_1 (GHMatters) P101912.AU.2

5. The system according to claim 4, wherein the PLC uses a Proportional Integral Derivative (PID) loop to set the position of the restriction valve and wherein the information received by the restriction valve from the PID is such that the restriction valve reacts slowly and does not cause rapid increase in load on the stationary engine.

6. The system according to any one of claims 3 to 5, wherein a pilot valve is configured to receive the control input signal; and whereupon receiving the control input signal, the pilot valve is configured to communicate hydraulically .0 with the restriction valve to set the position of the restriction valve.

7. The system according to any one of the preceding claims, wherein the system further comprises a relief valve which is operable if the hydraulic pressure of the oil increases during restriction to a pre-determined maximum system .5 pressure.

8. A hydraulic power unit comprising: a hydraulic pump driveable by a stationary engine, wherein the hydraulic pump is connectable to a mechanical drivehead for driving a downhole pump, the downhole pump for pumping fluid from a well; a restriction valve located between the hydraulic pump and the mechanical drivehead for restricting the flow of hydraulic oil to the mechanical drivehead; wherein the restriction valve is automatically adjustable so that the load on the stationary engine driving the hydraulic pump remains at or above a set threshold during pumping of fluid from the well.

9. The hydraulic power unit according to claim 8, wherein the set threshold is a load on the stationary engine in a range of from about 70 to about 80 % of the total available load on the engine. 10.The hydraulic power unit according to claim 8 or 9, further comprising a means for measuring the load on the stationary engine driving the hydraulic pump during pumping of fluid from the well such that the measured load is able to provide an input signal to a controller for the restriction valve.

25 18710052_1 (GHMatters) P101912.AU.2

11.The hydraulic power unit according to any one of claims 8 to 10, wherein the restriction valve has a body having a longitudinal bore extending therethrough from an opening at one end to a second opening at the opposite end, the body comprising a number of apertures in the wall forming the body; and a flow-diverting member in the form of a piston is positioned within the bore and movable so as to restrict or allow fluid flow through the valve; and a sleeve slidably mounted relative to the valve body for movement along the body to cause some or all of the apertures to be open or closed. .o

12.The hydraulic power unit according to any one of claims 8 to 11, further comprising a flow valve that is configured to divert a portion of the hydraulic oil flowing from the hydraulic pump to the drivehead so as to reduce the flow rate of the hydraulic oil reaching the drivehead. .5

13.The hydraulic power unit according to claim 12, further comprising a Programmable Logic Controller (PLC) for generating control input signal, wherein the amount of flow required though the restriction valve is controllable by a control input signal as written in the PLC, the control input signal being o0 responsive to said input signal provided to the PLC, and wherein the control input signal is further configured to adjust the flow valve.

14.A method for operating a hydraulic power unit, the method comprising the steps of: allowing a fluid to be pumped from a well using a downhole pump driven by a mechanical drivehead, wherein the mechanical drivehead is driven by a hydraulic pump driven by a stationary engine; determining a set load threshold for the stationary engine driving the hydraulic pump; controlling by restricting the flow of hydraulic oil between the hydraulic pump and the mechanical drivehead; automatically adjusting the restriction to the flow of hydraulic oil to maintain the load on the stationary engine at or above the set threshold during pumping of fluid from the well.

26 18710052_1 (GHMatters) P101912.AU.2

15. The method according to claim 14, wherein the set threshold is a load on the stationary engine in a range of from about 70 to about 80 % of the total available load on the engine.

16.The method according to claim 14 or 15, wherein the method further includes the step of measuring a load on the stationary engine driving the hydraulic pump during pumping of fluid from the well such that the measured load is able to provide an input signal to a controller for a restriction valve that is .0 arranged for restricting the flow of hydraulic oil between the hydraulic pump and the mechanical drivehead, and wherein measuring a load on the stationary engine comprises measuring the speed and the torque of the mechanical drivehead and multiplying the speed of the mechanical drivehead by the torque output of the mechanical drivehead. .5

17.The method according to claim 16, wherein the step of automatically adjusting the restriction valve includes the steps of: restricting the flow of hydraulic oil through the restriction valve if the load on the stationary engine driving the hydraulic pump needs to be o0 increased; and unrestricting the flow of hydraulic oil through the restriction valve if the load on the stationary engine needs to be decreased; wherein the position of the restriction valve is set by sending a signal to a pilot valve; and whereupon receiving the signal, the pilot valve communicates hydraulically with the restriction valve to set the position.

18.The method according to any one of claims 14 to 17, wherein the method further includes the step of: monitoring the hydraulic pressure of the hydraulic oil in the system; and opening a relief valve if the hydraulic pressure of the oil increases to a pre-determined maximum system pressure.

19.The method according to claim 16, or any one of claims 17 to 18 when dependent on claim 16, wherein the step of automatically adjusting the

27 18710052_1 (GHMatters) P101912.AU.2 restriction valve includes the steps of: closing the restriction valve and entering a HOLD mode when the hydraulic oil pressure reaches the set maximum system pressure; holding the restriction valve in position while in HOLD mode; measuring the load on the mechanical drivehead while the valve is in the HOLD mode; instructing the restriction valve to leave HOLD mode and opening the restriction valve to reduce the restriction, if the load on the stationary engine would be greater than 5 % above the set threshold. .0

20.The method according to any one of claims 14 to 19, wherein the method further includes the steps of: starting the engine remotely, and wherein the step of automatically adjusting the restriction to the flow of hydraulic oil only commences once the .5 load on the stationary engine has reached the set threshold; and diverting a portion of the hydraulic oil flowing from the hydraulic pump to the drivehead so as to reduce the flow rate of the hydraulic oil reaching the drivehead.

28 18710052_1 (GHMatters) P101912.AU.2