TECHNICAL FIELD

[0001 ] The present invention relates to removal and recovery of gas from a high point vent or liquid from a low point drain. In particular, although not exclusively, the present invention relates to automated removal and recovery of gas from a high point vent of a water pipeline or water from a low point drain associated with a coal seam gas pipeline.

BACKGROUND ART

[0002] Underground gas pipelines are often used to distribute gas. These pipelines are often undulating, particularly when installed in undulating land, and it is well known that liquid gathers in low points of gas pipelines. This is particularly the case in the coal seam gas industry, where water vapour associated with the produced gas condenses in the pipelines and accumulate at low points in the pipelines.

[0003] This accumulation of liquid, in the low points of the gas pipelines, causes an effective loss in pipeline cross sectional area, increases the pressure drop in the pipeline, and thus restricts gas flow in the pipeline. As such, this liquid must be regularly removed from the pipeline to ensure efficient operation of the pipeline. Additionally, the accumulation of the water may result in the slugging of liquids with potential equipment damage.

[0004] Low point drains are commonly installed at low points of the pipelines, which allow for the liquid at these low points to be drained. Figure 1 illustrates a low point drain 100, according to the prior art. The low point drain 100 comprises an enlarged tee piece, including an inlet 105, an outlet 1 10, and an enlarged body 115 in between the inlet 105 and outlet 1 10, the enlarged body 1 15 includes a drain 120 at a base thereof. In use, the water gathers in the body 1 15, and can be drained through the drain 120.

[0005] Figure 2 illustrates a simple low point drain assembly 200, according to the prior art. The low point drain assembly 200 includes a low point drain 100, a U-shaped polyethylene collector 205, and a steel pipe 210 that extends upwardly such that it emerges from the ground. A valve 215 is located at an end of the steel pipe 210, which can be manually operated to blow liquid out of the low point drain 100 using the pressure of the gas pipeline.

[0006] In such case, an operator may collect the liquid in a liquid tank, and manually close the valve when gas break through occurs (i.e. when gas exits the pipeline through the low point drain assembly 200). [0007] As gas pipeline networks include a large number of low point drains, manually draining liquid is labour intensive. As such, certain systems exist that automatically drain liquid from a low point drain.

[0008] Certain systems exist which include underground reservoirs associated with the low point drain, which are used to accumulate water from the drain. A level switch, such as a float switch, is then used to turn on and off a discharge pump, to discharge the underground reservoir. A problem with such systems is that they are costly to install and costly to maintain, as moving parts are located underground, and are not suitable for retrofitting into existing low point drains.

[0009] Other systems exist, which incorporate above-ground gas break through detection systems, and are configured to stop draining the water from the low point drain upon detection of gas break through. A problem with such systems is that they are expensive and unreliable.

[0010] Water pipelines are often also associated with coal seam gas production, where associated water is pumped for storage and treatment. When the water and gas are separated, small amounts of gas may enter the water pipeline. Additionally, any gas dissolved in the water may eventually separate from the water in the water pipeline. This gas accumulates at high points in the water pipeline, much like water accumulates at low points in a gas pipeline.

[0011 ] This accumulation of gas in high points of the water pipelines causes an effective loss in pipeline cross sectional area, increases the pressure drop in the pipeline, and thus restricts water flow in the pipeline. As such, this gas must be regularly removed from the pipeline to ensure efficient operation of the pipeline.

[0012] Vents are commonly installed at these high points of the water pipeline, which allow for the gas at these high points to be released to atmosphere. This is often done manually, which is labour intensive, but even in automatic systems, releasing gas to the atmosphere is not environmentally friendly, and therefore clearly undesirable.

[0013] An alternate to atmospheric release is to connect the gas discharge to an adjacent gas pipeline, however the pressure of the gas pipeline is frequently higher than the liquid pipeline rendering naturally driven recovery problematic. Additionally, such connections present a possibility for liquid entry into the gas line or vice versa.

[0014] As such, there is clearly a need for improved high point vent and low point drain systems.

[0015] It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.

SUMMARY OF INVENTION

[0016] The present invention is directed to automated high point vent and low point drain systems, which may at least partially overcome at least one of the abovementioned disadvantages or provide the consumer with a useful or commercial choice.

[0017] With the foregoing in view, the present invention in one form, resides broadly in an automated gas or liquid reinjection system, for reinjecting gas from an underground water pipeline into an associated gas pipeline, or reinjecting water from an underground gas pipeline into an associated water pipeline, the gas or liquid reinjection system including: a pump, configured to either pump a) gas from a riser of the underground water pipeline into the associated gas pipeline, or b) water from a low point drain of the underground gas pipeline into the associated water pipeline; one or more pressure sensors, configured to either sense a level of liquid in the riser or the low point drain; and a controller, coupled to the pump and one or more pressure sensors, configured to automatically control operation of the pump according to the sensed level of liquid in the riser or low point drain.

[0018] Advantageously, the system provides a simple and efficient means for transferring water from a low point drain while preventing gas break-through or gas from a high point vent while preventing water breakthrough. By using pressure to sense a level in the low point drain or riser, complex underground float-based systems are not needed, and underground moving parts may be avoided all together. Such configuration reduces installation costs, increases reliability and makes the system suitable for installation in existing low point drains.

[0019] The riser may include a float assembly configured to close an output of the riser when water reaches the float assembly, the one or more pressure sensors including a pressure sensor configured to sense pressure in the riser and a pressure sensor configured to sense pressure outside of the riser. A difference between the pressure in and outside of the riser may be used to determine a closing of the output by the float assembly.

[0020] The pump may be hydraulically driven. The pump may be driven by an adjacent hydraulic cylinder, which is driven by a hydraulic pump.

[0021 ] The system may be configurable to operate in a calibration mode, for establishing a baseline for water or gas pipeline operating conditions, wherein the controller is configured to operate with reference to the baseline. The system may be configured to periodically operate in calibration mode.

[0022] Preferably, in calibration mode, pressure measurements are made 1 ) when all water is displaced from the riser, and 2) when water fills the riser. These measurements may then be used to determine a height of the riser with reference to the pipeline.

[0023] High and low setpoints defining start and stop operations of the pump may be set in calibration mode.

[0024] Preferably, pressure measurements are made each time water completely fills the riser. This measurement, along with known height of the riser and water properties, provides measurement of pipeline pressure.

[0025] High and low setpoints defining start and stop operations of the pump may be set at least in part according to the pipeline pressure measurements defining an operating window that minimizes water column in the riser, thereby maximizing pump inlet pressure, thereby minimizing pump energy consumption.

[0026] Preferably, the system is configurable to operate in a vent mode, where the pump is not available, and the system is configured to vent gas from the water pipeline to the atmosphere. Such vent mode may comprise a failsafe, e.g. in case power is not available. The system may be configured to automatically operate in the vent mode when power is unavailable.

[0027] The one or more pressure sensors may comprise aboveground sensors.

[0028] In another form, the invention resides broadly in an automated gas or liquid breakthrough detection system including: an aboveground pump configured to drain liquid or pump gas from an in-ground pipeline; and one or more sensors associated with the pump configured to sense a load of the pump; and a controller, coupled to the sensors and the pump, configured to determine gas or liquid break-through when draining liquid or venting gas according to the sensed load of the pump.

[0029] Preferably, the pump comprises a hydraulically driven pump, wherein the load of the pump is determined according to a hydraulic pressure of the pump or the current drawn by the motor, at a given speed. [0030] Preferably, the liquid level is controlled to maximize the inlet pressure to the pump improving energy efficiency.

[0031 ] Preferably, a calibration sequence determines the height of the riser by fully discharging and then fully charging the riser.

[0032] Preferably the pipeline pressure is calculated each time the riser is fully discharged using the height of the riser.

[0033] In another form, the invention resides in an automated low point drain system including: one or more pressure sensors, configured to sense level of liquid in an in-ground low point drain; and a controller, coupled to the one or more pressure sensors, configured to automatically control drainage of the low point drain according to the sensed level in the low point drain to prevent gas break-through when draining the low point drain.

[0034] Advantageously, the system provides a simple and efficient means for transferring water from a low point drain while preventing gas break-through. By using pressure to sense a level in the low point drain, complex underground float-based systems are not needed, and underground moving parts may be avoided all together. Such configuration reduces installation costs, increases reliability and makes the system suitable for installation in existing low point drains.

[0035] Preferably, the low point drain is a low point drain of a gas pipeline. Suitably, the gas pipeline is a coal seam gas pipeline.

[0036] Preferably, the liquid comprises water. The skilled addressee will readily appreciate that the water will generally contain impurities.

[0037] Preferably, the sensors are aboveground sensors.

[0038] Preferably, the system is configured to transfer the water to an adjacent water pipeline. Alternatively, the system may be configured to transfer the water to an aboveground reservoir.

[0039] Preferably, the system includes a liquid drainage tube extending from a bottom portion of the low point drain to above ground level.

[0040] Preferably, the system includes a pump coupled to the liquid drainage tube, for draining liquid from the low point drain. Preferably, the pump is above ground.

[0041 ] Preferably, the pump is a multi-phase pump. The multi-phase pump may be configurable to pump gas from a gas pipeline associated with the low point drain.

[0042] The pump may comprise a booster pump.

[0043] Preferably, the pump comprises a hydraulically driven pump.

[0044] Alternatively, the system may utilise gas pressure from a gas pipeline associated with the low point drain to drain the low point drain.

[0045] Preferably, the system includes a level sensing tube extending down into the low point drain from above ground. At least one of the one or more pressure sensors may be coupled to the level sensing tube.

[0046] Preferably, the system is configured to inject gas into the level sensing tube, and measure a back pressure of the gas in the level sensing tube.

[0047] Preferably, the gas injected into the level sensing tube is injected at a higher pressure than an associated gas pipeline, to enable the gas to displace all water in the level sensing tube. A back pressure of the gas in the level sensing tube may then be measured.

[0048] Preferably, the gas injected into the level sensing tube is gas from a pipeline associated with the low point drain.

[0049] Preferably, the system includes a gas storage container, configured to store high- pressure gas for injection into the level sensing tube. The gas storage container may comprise a gas cylinder.

[0050] Suitably, the gas storage container is recharged using a pump and gas from pipeline. The same pump may be used to drain the low point drain and to recharge the gas storage container.

[0051 ] The one or more pressure sensors may include a sensor for sensing a pressure in an associated gas pipeline. The liquid level may be determined at least in part according to a pressure differential between a pressure of the gas pipeline and a pressure of the level sensing tube.

[0052] Preferably, the system includes a pump, for draining liquid from the low point drain, wherein the pump is configured to detect gas breakthrough. The pump may be configured to detect gas breakthrough by change in load of the pump.

[0053] The pump may be configured to stop upon detection of gas breakthrough. Such configuration may be a fault condition.

[0054] The system may be reconfigured to recharge a gas storage container upon detection of gas breakthrough.

[0055] The pump may comprise a hydraulically driven pump, wherein the load of the pump is determined according to a hydraulic pressure of the pump.

[0056] In another form, the invention resides broadly in an automated gas break-through detection system including: an aboveground pump configured to drain liquid from an in-ground low point drain; and one or more sensors associated with the pump configured to sense a load of the pump; and a controller, coupled to the sensors and the pump, configured to determine gas break-through when draining the low point drain according to the sensed load of the pump.

[0057] Preferably, the controller is configured to automatically control operation of the pump according to the determined gas break-through.

[0058] The pump may be configured to operate periodically and stop upon detection of gas break-through. As such, the system may comprise an automated low point drain system.

[0059] The pump may comprise a hydraulic pump, wherein the load of the pump is determined according to a hydraulic pressure of the pump.

[0060] In yet another form, the invention resides broadly in an automated low point drain method including: sensing a level of liquid in an in-ground low point drain using, at least in part, one or more pressure sensors; and automatically controlling drainage of the low point drain according to the sensed level in the low point drain to prevent gas break-through when draining the low point drain.

[0061 ] In yet another form, the invention resides broadly in an automated gas break-through detection method including: draining liquid from an in-ground low point drain using an aboveground pump; sensing a load of the pump using one or more sensors associated with the pump; and determining gas break-through when draining the low point drain according to the sensed load of the pump.

[0062] Any of the features described herein can be combined in any combination with any one or more of the other features described herein within the scope of the invention.

[0063] The reference to any prior art in this specification is not, and should not be taken as an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge.

BRIEF DESCRIPTION OF DRAWINGS

[0064] Various embodiments of the invention will be described with reference to the following drawings, in which:

[0065] Figure 1 illustrates a low point drain, according to the prior art.

[0066] Figure 2 illustrates a simple low point drain assembly, according to the prior art.

[0067] Figure 3 illustrates an automated coal seam gas low point drain system, according to an embodiment of the present invention.

[0068] Figure 4 illustrates a schematic of a controller of the system of Figure 3, according to an embodiment of the present invention.

[0069] Figure 5 illustrates an automated coal seam gas low point drain system, according to an embodiment of the present invention.

[0070] Figure 6 illustrates an automated coal seam gas low point drain system, according to an embodiment of the present invention.

[0071] Figure 7 illustrates an automated coal seam gas low point drain system, according to an embodiment of the present invention.

[0072] Figure 8 illustrates an automated coal seam gas low point drain system, according to an embodiment of the present invention.

[0073] Figures 9a shows an exemplary power load curve for a compressible fluid, where piston travel is mapped against load for the fluid.

[0074] Figures 9b shows an exemplary power load curve for a non-compressible fluid, where piston travel is mapped against load for the fluid.

[0075] Figure 10 illustrates an automated high point vent system, according to an embodiment of the present invention.

[0076] Figure 11 illustrates a simplified view of an automated high point vent system, according to an embodiment of the present invention.

[0077] Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way.

DESCRIPTION OF EMBODIMENTS

[0078] Embodiments of the present invention are described below that provide various means for draining low point drains and venting high points that are safe, simple and cost effective, and are suited for installation in existing low point drains.

[0079] Figure 3 illustrates an automated coal seam gas low point drain system 300, according to an embodiment of the present invention. The automated coal seam gas low point drain system 300 provides a simple and efficient means for transferring water from a low point drain 305 associated with a gas pipeline 310 to an adjacent water pipeline 315. The automated coal seam gas low point drain system 300 is able to detect a water level in the low point drain 305 and thereby provide effective drainage of the low point drain 305, while preventing gas breakthrough from the gas pipeline 310.

[0080] The automated coal seam gas low point drain system 300 includes a multi-phase pump 320, coupled to a drainage tube 325 in the low point drain 305, for transferring water from the low point drain 305 into the water pipeline 315. The multi-phase pump 320 is hydraulically driven, and is driven by a hydraulic drive 330. Operation of the multi-phase pump 320 is controlled by a controller, described in further detail below, to ensure that the multi-phase pump 320 drains the low point drain 305 when needed, while preventing gas breakthrough from the gas pipeline 310 by stopping drainage before gas breakthrough occurs.

[0081 ] A level sensing tube 335 extends down into the low point drain 305. Gas may be introduced into the level sensing tube 335 from above ground level to determine a level of water in the low point drain 305, which may in turn be used to activate the multi-phase pump 320. In particular, the introduction of gas into the level sensing tube 335 displaces any water from an inside of the level sensing tube 335, which in turn creates a back pressure on the gas in the level sensing tube 335. This pressure in the level sensing tube 335 is measured, and the pressure in the level sensing tube 335 and the pressure in the low point drain 305 enables a water level in the low point drain 305 to be accurately determined.

[0082] The automated coal seam gas low point drain system 300 includes a gas storage container 340 to supply the compressed gas to the level sensing tube 335. A flow control device 340a is associated with the gas storage container 340

[0083] The gas storage container 340 includes compressed gas from the gas pipeline 310, and is recharged using the multi-phase pump 320. As such, the multi-phase pump 320 is able to function both to drain the water from the low point drain 305 and to recharge the gas storage container 340 from the gas pipeline 310.

[0084] A number of actuated valves 345 and pressure sensors 350 are coupled to the controller to automatically direct the flow of water and gas to perform the various measurement, drainage and recharging operations of the system 300, as outlined below.

[0085] The drainage tube 325 and the level sensing tube 335 comprise parallel tubes, each passing into the low point drain 305 in a sealed manner from aboveground, therefore allowing installation and operation of the tubes 325, 335 without loss of fluids from the low point drain 305. In alternative embodiments, the drainage tube 325 and the level sensing tube 335 comprise concentric tubes.

[0086] In operation, as water flows into the low point drain 305 from the gas pipeline 310 the water level in the low point drain 305 rises. Small quantities of gas are introduced intermittently into the level sensing tube 335 by opening gas injection valve 345a, which displaces water in the level sensing tube 335 into the low point drain 305. The level sensing tube 335 functions thus as a bubble tube.

[0087] The gas pressure in the level sensing tube 335 quickly decays to an equilibrium point that is equal to the head of water above the bottom of the level sensing tube 335 plus the gas pressure in the low point drain 305.

[0088] A pressure sensor 350 monitors the pressure of the gas in the level sensing tube 335 and the pressure of the gas in the low point drain 305. The difference in these pressures is then used to calculate a height of the water relative to the bottom of the level sensing tube 335.

[0089] When the water level is above a predefined start threshold height 355, the pump 320 is activated. The predefined start threshold height 355 is chosen such that it is below a water level in the low point drain 305 where the low point drain 305 is isolated from the gas pipeline 310 by water. In particular, the gas pipeline 310 is coupled to the low point drain 305 by a connecting pipe 360, and the predefined start threshold height 355 is chosen such that no part of the connecting pipe 360 is filled with water. This prevents an unbalanced “ll-tube” from being created between the low point drain 305 and the gas pipeline 310, which could otherwise prevent accurate level measurements from being made.

[0090] Water level measurements are similarly used to stop the transfer of water from the low point drain 305 before gas break through occurs, thereby preventing gas break through. In other words, when the water level is below a predefined stop threshold height 365, which is before gas break through, the pump 320 is stopped.

[0091 ] The pressure in the gas storage container 340 is monitored by a pressure sensor 350. When the pressure in the gas storage container 340 drops to a predefined pressure (e.g. a pressure approaching the gas pipeline pressure), a recharging procedure is activated.

[0092] The multi-phase pump 320 is started to initiate the recharge procedure and water is transferred from the low point drain 305 into the water pipeline 315, until the water level in the low point drain 305 falls to below the level sensing tube 335 and near a bottom of the drainage tube 325. The level sensing tube 335 is a predetermined height above the bottom of the drainage tube 325, and as such, the pump 320 may run for a predetermined period of time below the stop threshold height 365 to reach such level.

[0093] At this point, a pump water inlet valve 345b is closed, and pump gas inlet valve 345c is opened and the pump 320 is restarted. This configuration draws gas from the level sensing tube 335 into the pump 320 where it is compressed sufficiently to displace any water from the pump 320, through a water discharge valve 345d, and into the water pipeline 315.

[0094] After a pre-set number of strokes (or operating time) of the pump 320, a gas storage container supply valve 345e is opened and a water pipeline shut-off valve 345d is closed, directing compressed gas from the pump 320 into the gas storage container 340. The gas injection valve 345a remains closed during the recharging procedure.

[0095] When the pressure measured in the gas storage container 340 reaches a high setpoint value, the pump 320 is stopped, the gas storage container supply valve 345e is closed, the water discharge valve 345d is opened, the pump gas inlet valve 345c is closed and the pump water inlet valve 345b is opened. The gas injection valve 345a is then reopened, upon which level measurement is performed.

[0096] As outlined above, the automated coal seam gas low point drain system 300 includes a controller, that controls the functions of the system 300 by taking measurements, and turning on and off the pump 320 and opening and closing the valves 345.

[0097] Figure 4 illustrates a schematic of a controller 400 of the system 300, according to an embodiment of the present invention.

[0098] The controller 400 includes a processor 405, and a memory 410 coupled to the processor 405, the memory 410 including instruction code executable by the processor 405 for performing the functions of the controller 400. The controller 400 further includes a sensor interfaces 415, a pump interface 420 and valve interfaces 425, coupled to the processor 405, for interfacing with the sensors 350, pump 320 and valves 345, respectively.

[0099] In normal use, when functioning to drain the low point drain 305, the controller 400 is initially configured in a monitoring cycle, where small quantities of gas are introduced intermittently into the level sensing tube 335 using the valve interfaces 425 and pressure data is received from the various pressure sensors 350 by the sensor interfaces 415. From the pressure data, the processor 405 determines a level of water in the low point drain 305. This may be performed by comparing the pressure values to data of one or more tables in the memory 410, or performing various calculations on the pressure values. The memory may include non-volatile memory ensuring retention of key memory tables after a power loss.

[00100] If the level of water in the low point drain 305 is determined to be above the start threshold height 355, the pump 320 is turned on using the pump interface 410, and the various valves 345 are configured to couple an output of the pump 320 to the water pipeline 315.

[00101] The pump 320 may be configured to operate for a pre-defined period, or a period corresponding to the determined water level, upon which the pump 320 is turned off, and the valves are reconfigured to determine a water level in the low point drain.

[00102] If the level is above the stop threshold height 365, the pump 320 is again configured to operate, and the process is repeated until the water level reaches the stop threshold height 365 and the drainage cycle is completed. The controller 400 is then reconfigured to the monitoring cycle.

[00103] The controller 400 periodically monitors the pressure of the gas storage container 340 on the sensor interfaces 415, and if the pressure of the gas storage container 340 drops below a defined level, the controller 400 moves to a recharge cycle. In the recharge cycle, the pump 320 is configured to empty the low point drain 305, until the water level in the low point drain 305 falls to below the level sensing tube 335 and near a bottom of the drainage tube 325. [00104] The controller then reconfigures the valves 345 using the valve interfaces 425 such that the pump 320 is configured to draw gas from the level sensing tube 335 where it is compressed sufficiently to displace any water from the pump 320, through the water discharge valve 345d, and into the water pipeline 315. The valves 345 are then again reconfigured using the valve interfaces 425, such that compressed gas is directed from the pump 320 into the gas storage container 340 until the pressure in the gas storage container 340 reaches a high setpoint value.

[00105] In some situations, it is not possible to choose the predefined start threshold height such that it is below a water level in the low point drain 305 where the low point drain 305 is isolated from the gas pipeline 310 by water, while enabling the low point drain to retain sufficient volumes of water. As an illustrative example, the connecting pipe 360 may be the lowest point in the low point drain 305, causing isolation between the low point drain 305 and the gas pipeline 310 with even small amounts of water. In such case, it is desirable to measure gas pressure directly from the gas pipeline 310.

[00106] Figure 5 illustrates an automated coal seam gas low point drain system 500, according to an embodiment of the present invention. The automated coal seam gas low point drain system 500 is similar to the automated coal seam gas low point drain system 300, but wherein gas pressure is measured at the gas pipeline 310, rather than through the low point drain 305.

[00107] In particular, a header 505 extends upwardly from the gas pipeline 310. The header is then coupled to a pressure sensor 350, to enable a pressure of the gas pipeline 310 to be determined regardless of whether the low point drain 305 and the gas pipeline 310 are isolated by water or not.

[00108] In some embodiments, a system may be provided that utilises the pressure of the gas pipeline 310 to discharge the water from the low point drain 305. In such case, the multiphase pump 320 may be removed altogether.

[00109] Figure 6 illustrates an automated coal seam gas low point drain system 600, according to an embodiment of the present invention. The automated coal seam gas low point drain system 600 is similar to the automated coal seam gas low point drain system 300, but where pressure of the gas pipeline 310 is used to discharge the water from the low point drain 305.

[00110] Similar to the system 300, the system 600 includes pressure sensors 350 and valves 345 and the gas storage container 340 supplies compressed gas through to the level sensing tube 335 to determine a water level in the low point drain.

[0011 1] However, instead of activating a pump, the controller is configured to open and close an outlet valve 605 associated with the drainage tube 325. While not illustrated, an output of the outlet valve 605 may be coupled to the water pipeline 315 or an aboveground reservoir.

[00112] As the system 600 does not include the multi-phase pump 320, a micro gas compressor 610 is coupled to a gas outlet of the low point drain 305 and is configured to recharge the gas storage container 340 when the pressure in the gas storage container 340 drops below a defined threshold.

[00113] In other embodiments, instead of utilising a level sensing tube 335, pressure measurements may be taken from the drainage tube 325 directly, e.g. at the inlet of the pump 320.

[00114] Figure 7 illustrates an automated coal seam gas low point drain system 700, according to an embodiment of the present invention. The automated coal seam gas low point drain system 700 is similar to the automated coal seam gas low point drain system 300, but wherein pressure measurements are taken using the drainage tube 325 rather than a separate level sensing tube 335.

[00115] When the pump 320 is not operating, the water pressure (Pw) at the inlet of the pump 320 is a function of the vertical height (Vh) of the pump 320 above the bottom of the drainage tube 325, the gas pressure (Pg) in the low point drain 305 and the height of water (Hw) above the bottom of the drainage tube 325.

[00116] Hw may be determined according to:

Hw = (Pw - Pg + Vh / 100) X 100; where

Hw and Vh are expressed in millimetres;

Pw and Pg are expressed in kPa;

[00117] Vh is established during the installation of the system, Pg may be measured by the pressure sensor 350 at the low point drain 305; and Pw is the pressure value measured by the pressure sensor 350 connected to the pump 320.

[00118] EXAMPLES

[00119] Pg has a measured value of 160 kPag; Vh has a fixed value of 3000 mm; and Pw has a measured value of 135 kPag. [00120] Using these values:

Hw = (135 - 160 + 3000/100) x 100

= 500 mm

[00121] When the level of water in the low point drain 305 is equal with the bottom of the drainage tube 325, Pw will have a measured value of 130 kPag and the calculated value of Hw is zero.

[00122] When the level of water in the low point drain 305 is 1000 mm above the bottom of the drainage tube 325, Pw will have a measured value of 120 kPag and the calculated value of Hw is 1000 mm.

[00123] Indicatively, the pump stop level may be set at about 50 mm above the bottom of the drainage tube 325 which equals 500 pascals and the pump start level may be set at 500 mm above the bottom of the drainage tube 325 which equals 5000 pascals.

[00124] In some embodiments, the systems are able self-calibrate by estimating a level of water in the low point drain 305, draining a known amount from the low point drain 305 (e.g. measuring a volume of water through the pump 320), and re-estimating the level of water in the low point drain 305 taking into consideration the volume of water removed from the low point drain 305.

[00125] The systems are also able to self-calibrate to zero by pumping water from the low point drain 305 until gas breakthrough occurs, wherein the Pw measurement immediately before gas breakthrough is used to recalibrate a zero water level.

[00126] In other embodiments of the invention, the level measurement methods may be avoided altogether and replaced by gas break through detection in the pump 320.

[00127] Figure 8 illustrates an automated coal seam gas low point drain system 800, according to an embodiment of the present invention. The automated coal seam gas low point drain system 800 is similar to the automated coal seam gas low point drain system 300, but wherein gas break through is detected at the pump 320 to control operation thereof.

[00128] Instead of the multiphase pump 320 being started according to water level measurements, it is instead periodically started, e.g. using a timer. When the multiphase pump 320 is in operation, water is drawn from the low point drain 305 and transferred into the water pipeline 315, in a similar manner to the system 300. However, the pump 320 continues to operate until gas enters the pump 320 (i.e. gas break through occurs), upon which the pump 320 is stopped. [00129] The pump 320 is driven by a hydraulic pump 805 and hydraulic reservoir 810 coupled to the hydraulic drive 330. As gas enters the pump 320, the load signature of the hydraulic pump 805 changes, due to the change from a non-compressible fluid (water) to a compressible fluid (gas). This change in load signature is instantly (very quickly) recognisable, and can be identified by sensors before gas is pumped into the water pipeline 315.

[00130] Figures 9a and 9b show exemplary power load curves for compressible and non- compressible fluids respectively, where piston travel is mapped against load for the fluid.

[00131] As can be clearly seen from Figures 9a and 9b, the load differences are identifiable from an early stage in piston travel, and as such, the system 800 is able to identify gas break through even part way through a stroke in which the gas first enters the pump.

[00132] The load of the hydraulic pump is continuously monitored by hydraulic pressure sensors, and upon identification of gas break through using the load signature, the pump 320 is stopped. The timer is then restarted, and the process may be repeated.

[00133] In some embodiments, the run time of the pump 320 is recorded and the volume of water transferred is calculated and compared the volume of the low point drain 305 between the bottom of the drainage tube 325 and the top of the pipe 360 connecting the low point drain 305 to the gas pipeline 310. This information is then used to adjust the timer to limit the number of pump cycles while ensuring that the water level in the low point drain 305 does not exceed a desired level.

[00134] The system 800 further includes a solar panel 815, a battery 820 and a DC control panel 825, coupled to and configured to power the hydraulic pump 805. Such configuration alleviates the need for generators or power supplied, and enables the system 800 to be configured off-site, and transported in a near ready-to-use configuration.

[00135] While the above embodiments have been separately illustrated, the skilled addressee will readily appreciate that the embodiments may be combined in any suitable manner. As an illustrative example, the solar panel 815, battery 820 and a DC control panel 825 may be used with any of the systems 300, 500 or 700. Similarly, the gas break through detection of the system 800 may be used to complement the liquid level measurements of the systems 300, 500, 700, to detect if gas breakthrough has unexpectedly occurred (i.e. as a failsafe).

[00136] While the above embodiments describe draining water from a low point drain 305 associated with a coal seam gas pipeline 310, the skilled addressee will readily appreciate that the systems may be used for draining any type of liquid from any suitable type of low point drain. [00137] Furthermore, while the above embodiments describe draining water from a low point drain 305, similar embodiments relate to venting gas from a high point of a water pipeline.

[00138] Figure 10 illustrates an automated high point vent system 1000, according to an embodiment of the present invention. The automated high point vent system 1000 provides a simple and efficient means for venting (transferring gas from) a high point of a water pipeline 1005 associated with a coal seam gas pipeline 1010. The automated high point vent system 1000 is configured to reinject gas from the water pipeline 1005 into the coal seam gas pipeline 1010, while preventing water breakthrough from the water pipeline 1005 into the coal seam gas pipeline 1010. As such, the term venting refers to the removal of gas from the pipeline, and does not imply any venting to atmosphere.

[00139] The automated high point vent system 1000 includes an injection pump 1015, coupled to an outlet of the riser 1020, for transferring gas from the water pipeline 1005 into the gas pipeline 1010. The injection pump 1015 is mechanically driven by a hydraulic cylinder 1025 and a coupling 1030 comprising a universal joint. The hydraulic cylinder 1025 is preferably driven by a bi-directional hydraulic pump 1035, or optionally a unidirectional pump and valves, which are configured to change motive direction of the hydraulic cylinder 1025 to thereby provide a reciprocating action, which may be mechanically translated to the injection pump 1015.

[00140] The riser 1020 includes a float assembly 1040 configured to close an output of the riser 1020 when water reaches the float assembly 1040. Upper and lower pressure transducers 1045a, 1045b are provided on either side of the output of the riser 1020, such that when rising water causes the float assembly 1040 to close the outlet, the upper and lower pressure transducers 1045a, 1045b become separated, and pressure measurements of the upper and lower pressure transducers 1045a, 1045b will immediately diverge.

[00141] Operation of the pump 1015 is controlled by a controller 1050, to ensure that the pump 1015 vents gas from the water pipeline 1005 when needed, while preventing water from being pumped from the water pipeline 1005. In particular, the controller identifies closing of the outlet by the float assembly 1040 by a difference in pressure measurements at the upper and lower pressure transducers 1045a, 1045b, and therefore terminates operation of the pump 1015, and thereby reinjection of gas.

[00142] The system 1000 further includes a pneumatic control system, coupled to the controller 1050. The pneumatic control system comprises an air pump 1055 and a compressed air cylinder 1060, and a plurality of air activated valves 1065, coupled to the controller 1050, to automatically perform the various operations of the system 1000, as outlined below. [00143] An atmospheric vent 1070 is provide intermediate the riser 1020 and pump 1015, and is associated with an air actuated (fail open) ball valve that allows the system 1000 to operate without power, venting gas to atmosphere.

[00144] A solar powered battery pack 1075 provides power to the controller 1050, and in turn a motor 1080 that drives the hydraulic pump 1035. A hydraulic reservoir 1085 is also associated with the hydraulic pump 1035. The solar powered battery pack 1075 also powers the air compressor 1055. Such configuration ensures that the system need not be connected to a power grid.

[00145] The system 1000 operates in five main operating modes, as follows:

1 ) a reinjection mode, where the pump 1015 is configured to reinject gas from the water pipeline 1005 into the gas pipeline;

2) a calibration mode, for establishing a baseline for water pipeline and riser geometry and operating conditions;

3) a standby mode, where the pump 1015 is turned off and the pressure at the upper and lower pressure transducers 1045a, 1045b is monitored;

4) a vent mode, where the pump 1015 is turned off, vent 1070 is open and gas from the water pipeline 1005 is vented to atmosphere; and

5) a safe (hibernation) mode, where the pump 1015 is turned off, vent 1070 is open and gas from the water pipeline 1005 is vented to atmosphere, and wherein the system 1000 is prevented from restarting.

[00146] Further detail of these operation modes are provided below.

[00147] Calibration Mode

[00148] The calibration mode is performed initially as part of the commissioning process and subsequently at a predetermined rate (i.e., hourly / daily), to establish a baseline for water pipeline operating conditions.

[00149] As part of this calibration process, the following parameters are established: a vertical offset between the bottom of the riser 1020 and the float assembly 1040; a calibration offset between upper and lower pressure transducers 1045a, 1045b at the water pipeline operating pressure; and a pressure in the water pipeline 1005.

[00150] From this data, high and low setpoints are established which are used to turn the pump 1015 on and off. [00151] Initially, sufficient gas is allowed to accumulate in the riser 1020 to displace all water from the riser 1020. The gas pressure is then measured at the lower pressure transducer 1045b and recorded, which corresponds to the pressure in the water pipeline 1005.

[00152] The pressure is then measured by the upper transducers 1045a and compared with that of the lower transducer 1045b, and a measurement error between the transducers 1045a, 1045b is recorded. This measurement error (offset) is then (permanently) applied to the upper pressure transducer 1045a to calibrate the upper transducer 1045a, such that its value is exactly equal that of the lower pressure transducer 1045b.

[00153] Gas is then removed from the riser 1020 and reinjected into the gas pipeline until the float assembly 1050 closes an orifice of the riser 1020, which may be identified by a divergence between the pressures measured by the upper and lower pressure transducers 1045a, 1045b. The reduction in the pressure recorded by the lower pressure transducer 1045b after the gas is removed is directly proportional to the vertical offset between the bottom of the riser 1020 and the float assembly 1050.

[00154] Any variation, however, in the underlying pressure in the water pipeline will impact the above calculation therefore the procedure is repeated multiple times until a consistent value is established and/or periodically.

[00155] High and low setpoints are then set between pressure values corresponding to the bottom of the riser 1020 and the float assembly 1050, the high and low setpoints configured to transition the system between reinjection and standby mode, such that a column of water is maintained in the riser 1020 during standby mode. These setpoints may be chosen to maximise inlet pressure to the pump 1015, by minimising the height or head of liquid in the riser 1020, in doing so optimising energy efficiency.

[00156] Standby Mode

[00157] In the standby mode, pressures measured by the upper and lower pressure transducers 1045a, 1045b are monitored such that the system may transition to reinjection mode when reaching the low setpoint. As outlined above, the high and low setpoints configured such that a column of water is maintained in the riser 1020 between the high and low setpoints.

[00158] In use, the standby mode may be initiated with the float assembly 1040 closing the orifice of the riser 1020 when the pressure measured by the upper pressure transducer 1045a is for example a nominal 20 kPa below the pressure measured by the lower pressure transducer 1045b. As gas accumulates in the riser 1020, the water level is depressed, causing the float assembly to open the orifice, causing the gas to enter the pipework above the riser, thereby allow the water level in the riser 1020 to rise such that the float assembly 1040 closes the orifice.

[00159] This process repeats, and the system 1000 monitors the gas pressure at the upper and lower pressure transducers 1045a, 1045b. The system may identify this opening and closing by the float assembly by differences between measurements from the upper and lower pressure transducers. When the measurements from the upper and lower pressure transducers track together, from the float assembly being open, the water level in the riser corresponds to the pressure read. The system continues to monitor the rising pressure in the upper and lower pressure transducers as gas accumulates in the riser, initiating reinjection mode when reaching the low setpoint.

[00160] Reinjection Mode

[00161] In reinjection mode, the pump 1015 is initially operated at a default speed to transfer gas from the riser 1020 into the gas pipeline 1010. Simultaneously or periodically, the pressure is measured by the upper and lower pressure transducers 1045a, 1045b. The pump 1015 continues to operate at the default speed as the gas pressure measured at the lower pressure transducer 1045b falls, corresponding to a continually rising water level.

[00162] In the event that the pressure measured by the lower pressure transducer 1045b continues to rise, the speed of the pump is increased until the pressure begins to fall and then modulated to achieve an approximate decrease in gas pressure of 5kPa per minute.

[00163] When the rising water level ultimately causes the float assembly 1040 to close the orifice, the pressure measurements of the upper and lower pressure transducers 1045a, 1045b diverge, upon which standby mode is initiated.

[00164] Subject to the measured underlying variations in the water pipeline pressure, the controller may adjust the speed of the motor 1015 to maintain the water level in the riser at around the midpoint riser. This may result in a low stroke rate for the system, and less intermittent operation, which correspond to low power consumption per unit of gas transferred. The system control thus may optimise the speed, to the minimal stroke speed of the motor 1015 required to evacuate the gas from the highpoint, thus optimising the energy efficiency of the mechanical system by minimising fluid dynamic and mechanical losses.

[00165] Vent Mode

[00166] Upon detection of a low voltage in the solar powered battery pack 1075, vent mode is activated and power is switched off, causing valves to open such that the vent 1070 vents gas to atmosphere.

[00167] In particular, a low voltage relay is configured to power down the system 100, and enable the solar panels to recharge the batteries. When the battery bank is recharged to a predetermined voltage, a second (high voltage) relay causes the controller to reboot and enter standby mode.

[00168] Safe (Hibernation) Mode

[00169] Upon detection of a fault, safe mode is activated and power and power is switched off, causing valves to open such that the vent 1070 vents gas to atmosphere, much like vent mode. However, in safe mode, automatic restart is prevented, requiring a visit by a technician to troubleshoot the function that caused the trip before re-entering standby mode.

[00170] In some embodiments, high and low setpoints may be set to maintain a minimum water column in the riser such as to give maximum inlet pressure to the booster, while keeping the pipeline clear of gas. Such configuration is more efficient than maintaining a high column of water.

[00171] In addition to controlling operation between the different modes, the controller calculates a volume of gas pumped into the pipeline. In particular, the controller utilises the swept volume of the gas compressor cylinder, the volumetric efficiency of the inlet/outlet check valves and the recorded gas pressure and temperature for every stroke of the pump to calculate the quantity of gas that is transferred into the gas pipeline.

[00172] The pump 1015 is double acting, in that gas is drawn into the pump 1015 on one side and compressed on the other, in a reciprocating manner.

[00173] Proximity switches may be mounted on each end of the cylinder 1025 to detect the ends of strokes, and invert the direction of the hydraulic drive (e.g. using valves) to thereby cause reciprocation of the cylinder (and thereby the pump).

[00174] The pump 1015 and the hydraulic cylinder 1025 may be mounted sufficiently apart that cylinder 1025 is in a gas non-hazardous area.

[00175] The system 1000 is particularly suited to being retrofitted to a valve outlet of a high point vent which is configured to vent to atmosphere. In such case, the system may be coupled directly to the existing high point vent components with minimal modification.

[00176] While the above embodiment utilises a float assembly to automatically prevent water from leaving the riser, in other embodiments, water may be detected at the pump, according to an increase in load in the motor when liquid enters the pump.

[00177] Figure 11 illustrates a simplified view of an automated high point vent system 1 100, according to an embodiment of the present invention. The automated high point vent system 1100 is similar to the automated high point vent system 1000, but wherein load characteristics of the pump are used to identify water in the pump 1015.

[00178] The system 1100 includes a riser 1120, similar to the riser 1020, but gas is normally withdrawn below the float valve assembly, and therefore does not automatically prevent water from leaving the water pipeline 1005. This avoids pressure loss through the float valve and optimises energy efficiency, whilst leaving the float valve orifices appropriately sized for atmospheric fail over flow rate requirements. A check valve 1071 and pressure transducer 1072 is included providing optional provision to withdraw gas above the float valve.

[00179] The system 1100 includes a controller 1 150, similar to the controller 1050, but further configured to monitor a load of the hydraulic pump 1035. As such, the controller 1 150 is able to distinguish between gas (compressible fluid) and water (non-compressible fluid) in the pump 1015.

[00180] The system 1 100 is configured to operate in a reinjection mode, where gas is pumped from the riser 1120 to the gas pipeline 1010, until a load of the hydraulic pump 1035 increases, indicating that water is present in the pump.

[00181] At this stage, the system is configured to operate in a standby mode, and a pressure of the riser is monitored. When the pressure in the riser goes above a threshold, a recirculation mode is activated.

[00182] The recirculation mode is configured to clear water from the pump and pipework, and pump same back into the riser 1120, until a load of the hydraulic pump 1035 indicates that gas is present in the pump. At this stage, the system 1 100 is again configured to operate in a reinjection mode.

[00183] In addition to monitoring pressures for operating the systems outlined above, the systems 1000, 1100 may be configured to log pipeline pressure measurement. Given the height of the riser H1 in metres then each time the booster pumps till the float shuts off in the system 1000 or water breaks through in the system 1 100, then pressure in the pipeline can be calculated as P1 + H1 *10 kPa, where P1 is the pump inlet pressure.

[00184] Advantageously, the systems and methods described above provide simple and efficient means for transferring water from a low point drain while preventing gas break-through, or venting gas from a high point while preventing water breakthrough.

[00185] By using pressure to sense a level in the low point drain, complex underground floatbased systems are not needed, and underground moving parts may be avoided all together. Such configuration reduces installation costs, increases reliability and makes the system suitable for use in existing low point drains.

[00186] Furthermore, systems and methods are described which provide gas or water break through detection, without requiring a separate gas or water break through device. In particular, the pump, which is used to pump the liquid from the low point drain or gas from the high point vent, is also used to detect gas or water break through. This enables gas or water break through detection to be included in such systems with minimal impact thereto.

[00187] In the present specification and claims (if any), the word ‘comprising’ and its derivatives including ‘comprises’ and ‘comprise’ include each of the stated integers but does not exclude the inclusion of one or more further integers.

[00188] Reference throughout this specification to ‘one embodiment’ or ‘an embodiment’ means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases ‘in one embodiment’ or ‘in an embodiment’ in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.

[00189] In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims (if any) appropriately interpreted by those skilled in the art.