WO2021051157A1

WO2021051157A1 - A gas well gathering pipeline gas re-injection system

Info

Publication number: WO2021051157A1
Application number: PCT/AU2020/050943
Authority: WO
Inventors: Colin STENT; Rebecca SPARROW; Adam STENT
Original assignee: Solar Injection Australia Pty Ltd
Priority date: 2019-09-17
Filing date: 2020-09-08
Publication date: 2021-03-25
Also published as: AU2020347873A1; AU2021104054A4

Abstract

A gas reinjection system has a gathering system water pipeline gas take-off inlet and a gathering system gas pipeline gas reinjection outlet. An electric motor drives a gas booster interfacing the inlet and the outlet to pressurise gas drawn from the inlet to a pressure in excess of that of the gas pipeline.

Description

A gas well gathering pipeline gas re-injection system

Field of the Invention

[0001 ] This invention relates generally to a gas reinjection system for removing gas from water pipelines of gas well gathering systems.

Background of the Invention

[0002] Gas wells typically emit gas that is heavily entrained with groundwater. As such, well heads are typically fitted with a separator that separates gas from water, each of which is piped to treatment plants via separate water and gas pipelines, referred to as a gathering system.

[0003] However, well head separators are unable to completely separate water and gas, resulting in water collecting in the gas pipeline and gas collecting in the water pipeline of the gathering system, both being undesirable for causing a reduction in flow efficiency thereof.

[0004] The present invention seeks to provide a system, which will overcome or substantially ameliorate at least some of the deficiencies of the prior art, or to at least provide an alternative.

[0005] It is to be understood that, if any prior art information is referred to herein, such reference does not constitute an admission that the information forms part of the common general knowledge in the art, in Australia or any other country.

Summary of the Disclosure

[0006] There is provided herein a gas reinjection system which may be installed along a gathering system between a well head and processing plant.

[0007] The system comprises a water pipeline gas take-off inlet and a gas pipeline gas reinjection outlet. A motor drives a gas booster interfacing the inlet and the outlet to pressurise gas drawn from the inlet to a pressure in excess of the gas pipeline. The inlet may be typically at a high point of the water pipeline.

[0008] The system is preferably solar powered for remote location deployment and, as such, may be configured for minimising power draw and be suited for outdoor conditions including extreme temperature. [0009] In this regard, the system may comprise a gas accumulator tank between the inlet and the gas booster which accumulates gas periodically drawn from the inlet. A pressure transducer may interface the gas accumulator tank to monitor inlet pressure. The system may comprise a controller which operates the motor when the inlet pressure exceeds a threshold. Preferably the controller operates the motor until the inlet pressure falls beneath the threshold by a margin for hysteresis control.

[0010] The gas booster preferably allows for free flow of gas from the inlet to the outlet and, in this regard, may be a double acting reciprocating pump. As such, when inlet pressure happens to exceed outlet pressure, gas may flow from the water pipeline to the gas pipeline without mechanical assistance and associated power draw. In embodiments, the system monitors outlet pressure so as to not operate the motor if the inlet pressure exceeds the outlet pressure by a margin.

[0011 ] The system may comprise an arrangement of dryers to ensure that dry gas is fed into at least one of the gas booster and the gas pipeline.

[0012] The system may comprise an aftercooler between the gas booster and the outlet to ensure that cool gas enters the gas pipeline. The system may comprise a gas outlet temperature sensor to selectively operate the aftercooler when gas outlet temperature exceeds a threshold.

[0013] The system may monitor various setpoint parameters for selective operation so as to, for example, only operate when the battery bank is sufficiently charged and temperatures and pressures fall within normal ranges.

[0014] In embodiments, the system comprises a data interface for remote operation, reconfiguration and/or data gathering. The gas booster may be isolated for volatile gas (such as methane gas) handling safety rating.

[0015] With the foregoing in mind, in accordance with one embodiment, there is provided a gas reinjection system comprising: a gathering system water pipeline gas take-off inlet; a gathering system gas pipeline gas reinjection outlet; and an electric motor driving a gas booster interfacing the inlet and the outlet to pressurise gas drawn from the inlet to a pressure in excess of that of the gas pipeline. [0016] The system may comprise an inlet pressure transducer to measure inlet pressure and wherein the system may be configured to operate the motor according to the inlet pressure.

[0017] The system may comprise a gas accumulator tank between the take-off inlet and the gas booster and wherein the inlet pressure transducer interfaces the tank. [0018] The system may be configured to operate the motor when the inlet pressure exceeds a first pressure threshold and deactivate the motor when the inlet pressure falls beneath a second pressure threshold, the second pressure threshold being less than the first pressure threshold.

[0019] The gas booster may allow free flow of gas when inlet pressure exceeds outlet pressure.

[0020] The gas booster may comprise a reciprocating pump.

[0021 ] The gas booster may comprise a double acting reciprocating pump.

[0022] The system may comprise an outlet pressure transducer to measure outlet pressure and wherein the system may be configured to not operate the motor when the inlet pressure exceeds the outlet pressure.

[0023] The system may be configured to not operate the motor when the inlet pressure exceeds the outlet pressure by a pressure margin.

[0024] The take-off may be a pipeline highpoint.

[0025] The system may further comprise a dryer between the take-off and the booster. [0026] The system may further comprise a back-check valve between the booster and the outlet.

[0027] The system may further comprise a pressure safety valve between the gas booster and the outlet.

[0028] The pressure safety valve may comprise a safety valve outlet between the inlet and the gas booster and wherein the pressure safety valve may be configured to release pressure via the safety valve outlet when pressure exceeds a first safety threshold.

[0029] The pressure safety valve may comprise an atmospheric valve outlet and wherein the pressure safety valve may be configured to release pressure to atmosphere when the pressure exceeds a second safety threshold exceeding the first safety threshold by a margin.

[0030] The system may further comprise an aftercooler between the gas booster and the outlet.

[0031 ] The aftercooler may comprise an aftercooler electric motor.

[0032] The system may comprise an outlet gas temperature sensor and wherein the system may be configured to operate the aftercooler electric motor when outlet gas exceeds an outlet gas threshold.

[0033] The system may further comprise an inlet pressure transducer to monitor inlet pressure; and an outlet pressure transducer to monitor outlet pressure; and a gas accumulator between the take-off inlet and the gas booster, wherein the gas booster allows free flow of gas when the inlet pressure exceeds outlet pressure and wherein, as gas from the water pipeline periodically enters the inlet and gradually increases the pressure within the gas accumulator and depending on a difference between the inlet pressure and the outlet pressure, the system is configured to: not operate the motor such that gas flows without mechanical assistance of the gas booster through the system between the inlet and the outlet; or operate the motor to pressurise the gas to a pressure in excess of that of the gas pipeline for reinjection.

[0034] Other aspects of the invention are also disclosed.

Brief Description of the Drawings

[0035] Notwithstanding any other forms which may fall within the scope of the present invention, preferred embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which:

[0036] Figure 1 shows a gas reinjection system in accordance with an embodiment; and

[0037] Figure 2 shows exemplary operation of the gas reinjection system in accordance with an embodiment. Description of Embodiments

[0038] A gas well pipeline gathering system 131 comprises a water pipeline 101 and a gas pipeline 102 between a well head and a processing plant.

[0039] A gas reinjection system 100 comprises a water pipeline gas take-off inlet 1 19 and a gas pipeline reinjection outlet 120. Isolation valves 103 and 1 18 may selectively isolate system 100.

[0040] The system 100 further comprises an electric motor 113 driving a gas booster 110. The gas booster 1 10 interfaces the inlet 119 and the outlet 120 to pressurise gas drawn from the inlet to a pressure in excess of that of the gas pipeline 102 for reinjection.

[0041 ] The inlet 1 19 may be at a suitable highpoint along the water pipeline 101 . The inlet 119 may interface a highpoint valve 104.

[0042] A control interface 112 may operably interface with the motor 113. The control interface 112 may comprise a controller such as a programmable logic controller (PLC). The interface 112 may further comprise a power controller to power the motor 113.

[0043] In a preferred embodiment, the system 100 is solar powered and, in this regard, comprises an array of solar panels charging a battery bank from which the power controller draws power for the motor 113.

[0044] The gas booster 110 may be a reciprocating pump. The reciprocating pump may be a double acting reciprocating pump to utilise inlet pressure to reduce power consumption and allow for non-mechanically assisted free flow when inlet pressure exceeds outlet pressure, especially beneficial for reducing power consumption. [0045] A data interface (such as a digital cellular network data interface) may interface the controller for remote data access, reconfiguration and/or operation of the system 100.

[0046] The system 100 may comprise an inlet pressure transducer 107 to measure inlet pressure and the controller may be configured to operate the motor 1 13 when the inlet pressure exceeds a first pressure threshold. [0047] The system 100 may comprise a gas accumulator tank 106 between the inlet 119 and the booster 1 10 which accumulates gas periodically drawn from the inlet 119. An isolation valve 105 may interface an inlet of the gas accumulator tank 106.

[0048] The inlet pressure transducer 107 may interface the gas accumulator tank so as to determine the pressure therein.

[0049] The system 100 may further comprise an outlet pressure transducer (not shown) between the booster 110 and the outlet 120.

[0050] In embodiments, the controller may be configured for not operating the motor 113 when the measured inlet pressure exceeds the measured outlet pressure by a margin, thereby allowing free flow of gas through the system 100 from the water pipeline 101 to the gas pipeline 102 without operation of the motor 113.

[0051 ] The system 100 may comprise a gas dryer 11 1 between the inlet 1 19 and the booster 110. The gas dryer 1 11 may interface between the gas accumulator tank 106 and the gas booster 1 10. The gas dryer 111 may dry gas through compression, centrifugal coalescing, refrigeration or chemical absorption.

[0052] An isolation valve 109 may isolate an inlet of the gas booster 110. A further isolation valve 108 may isolate an inlet of the dryer 1 11.

[0053] The system 100 may comprise a pressure safety valve 116 at an outlet of the gas booster 110.

[0054] The pressure safety valve 116 may comprise an outlet feeding back into an inlet of the gas booster 110 so as to feed gas back into the inlet of the gas booster 110 when the outlet pressure exceeds a first safety threshold. The pressure safety valve 116 may further comprise an atmospheric outlet to vent gas to the atmosphere when the outlet pressure exceeds a second safety threshold greater than the first safety threshold.

[0055] The system 100 may comprise a back-check valve 114 between the gas booster 110 and the outlet 120.

[0056] The system 100 may comprise an aftercooler 115 between the gas booster 110 and the outlet 120. An aftercooler electric motor 1 16 may operate the aftercooler 1 15. [0057] Furthermore, the system 100 may comprise a dryer 117 between the gas booster 1 10 and the outlet 120. The aftercooler 115 and the dryer 117 may allow for the reinjection of cool dry gas back into the gas line 102.

[0058] The system 100 may further comprise temperature sensors (not shown) configured to monitor temperature of at least one of ambient temperature, gas inlet temperature, gas outlet temperature, motor operational temperature and gas booster operational temperature.

[0059] The system 100 is preferably volatile gas safety rated. In this regard, the gas booster 110 may be isolated from other components of the system such as away from the motor 113 by a sufficiently elongate piston or driveshaft and/or away from the control interface 1 12. For example, the solar power battery supply system may be located more than 5 m away from the gas booster 110.

[0060] Exemplary operational 120 of the system 100 is given in Figure 2.

[0061 ] The operation 120 may comprise startup at step 123 wherein the controller checks whether system parameters fall within expected ranges. For example, the controller 100 may check battery charge state, temperatures and/or pressures. [0062] At step 124, the controller may monitor inlet pressure using the inlet pressure transducer 107. Gas from the water pipeline 1 10 periodically enters the inlet 119 and the gas accumulator 106 gradually increasing the interior pressure thereof.

[0063] At step 125, the controller may determine that the inlet pressure exceeds a first inlet pressure threshold.

[0064] At step 126, the controller may check that the inlet pressure is less than the outlet pressure. If the controller determines that the inlet pressure is in excess of the outlet pressure by a margin, the controller may not operate the motor 1 13 such that gas flows without mechanical assistance of the gas booster 110 through the system between the inlet 1 19 and the outlet 120.

[0065] At step 127, the controller may check various operational parameter setpoints. For example, the controller may check that the gas booster 110 and the motor 1 13 are within an operational temperature range. The controller may confirm that the batteries comprise sufficient charge. The controller may confirm that the inlet gas temperature is beneath a certain temperature. The controller may confirm that ambient temperature is beneath a certain temperature.

[0066] Upon confirmation of the setpoints, the controller may start the motor 113 at step 128. The motor 113 may by operated until the controller determines that the inlet pressure falls beneath a second inlet pressure threshold at step 130, being less than the first inlet pressure threshold by a margin.

[0067] The controller may thereafter continuously monitor the inlet pressure to repeat the process.

[0068] The controller may measure the outlet gas temperature to operate the motor 116 of the aftercooler 115 if the outlet gas temperature exceeds a threshold.

[0069] The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that specific details are not required in order to practise the invention. Thus, the foregoing descriptions of specific embodiments of the invention are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed as obviously many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the following claims and their equivalents define the scope of the invention.

[0070] The term "approximately" or similar as used herein should be construed as being within 10% of the value stated unless otherwise indicated.

Claims

1 . A gas reinjection system comprising: a gathering system water pipeline gas take-off inlet; a gathering system gas pipeline gas reinjection outlet; and an electric motor driving a gas booster interfacing the inlet and the outlet to pressurise gas drawn from the inlet to a pressure in excess of that of the gas pipeline.

2. The system as claimed in claim 1 , wherein the system comprises an inlet pressure transducer to measure inlet pressure and wherein the system is configured to operate the motor according to the inlet pressure.

3. The system as claimed in claim 2, wherein the system comprises a gas accumulator tank between the take-off inlet and the gas booster and wherein the inlet pressure transducer interfaces the tank.

4. The system as claimed in claim 3, wherein the system is configured to operate the motor when the inlet pressure exceeds a first pressure threshold and deactivate the motor when the inlet pressure falls beneath a second pressure threshold, the second pressure threshold being less than the first pressure threshold.

5. The system as claimed in claim 1 , wherein the gas booster allows free flow of gas when inlet pressure exceeds outlet pressure.

6. The system as claimed in claim 5, wherein the gas booster comprises a reciprocating pump.

7. The system as claimed in claim 6, wherein the gas booster comprises a double acting reciprocating pump.

8. The system as claimed in claim 2, wherein the gas booster allows free flow of gas when inlet pressure exceeds outlet pressure, wherein the system comprises an outlet pressure transducer to measure outlet pressure and wherein the system is configured to not operate the motor when the inlet pressure exceeds the outlet pressure.

9. The system as claimed in claim 8, wherein the system is configured to not operate the motor when the inlet pressure exceeds the outlet pressure by a pressure margin.

10. The system as claimed in claim 1 , wherein the take-off is a pipeline highpoint.

11 . The system as claimed in claim 1 , further comprising a dryer between the take off and the booster.

12. The system as claimed in claim 1 , further comprising a back-check valve between the booster and the outlet.

13. The system as claimed in claim 1 , further comprising a pressure safety valve between the gas booster and the outlet.

14. The system as claimed in claim 13, wherein the pressure safety valve comprises a safety valve outlet between the inlet and the gas booster and wherein the pressure safety valve is configured to release pressure via the safety valve outlet when pressure exceeds a first safety threshold.

15. The system as claimed in claim 14, wherein the pressure safety valve comprises an atmospheric valve outlet and wherein the pressure safety valve is configured to release pressure to atmosphere when the pressure exceeds a second safety threshold exceeding the first safety threshold by a margin.

16. The system as claimed in claim 1 , further comprising an aftercooler between the gas booster and the outlet.

17. The system as claimed in claim 16, wherein the aftercooler comprises an aftercooler electric motor.

18. The system as claimed in claim 17, wherein the system comprises an outlet gas temperature sensor and wherein the system is configured to operate the aftercooler electric motor when outlet gas exceeds an outlet gas threshold.

19. The system as claimed in claim 1 , wherein the system further comprises an inlet pressure transducer to monitor inlet pressure; and an outlet pressure transducer to monitor outlet pressure; and a gas accumulator between the take-off inlet and the gas booster, wherein the gas booster allows free flow of gas when the inlet pressure exceeds the outlet pressure and wherein, as gas from the water pipeline periodically enters the inlet and gradually increases the pressure within the gas accumulator and depending on a difference between the inlet pressure and the outlet pressure, the system is configured to: not operate the motor such that gas flows without mechanical assistance of the gas booster through the system between the inlet and the outlet; or operate the motor to pressurise the gas to a pressure in excess of that of the gas pipeline for reinjection.