Systems and methods for treating wastewater from oilfield wells with combined power generation

Abstract

The wastewater treatment system comprises a burner (33) adapted to burn a fuel and thereby generate a pressurized combustion gas. The system further comprises a gas turbine (41) adapted to expand the pressurized combustion gas and thereby generate mechanical power. The system further comprises a boiler (25) adapted to receive expanded combustion gas from the gas turbine (41). The boiler is fluidly coupled to a waste water line (7). In use, heat from the combustion gas generates steam from wastewater and removes brine from the boiler through a brine discharge line (28). In some embodiments, a steam cycle is also provided in the system to extract additional power.

Description

Technical Field

[0001] The present disclosure relates to wastewater treatment. More specifically, the present disclosure relates to systems and methods for treating wastewater from oilfield wells. Background Art

[0002] Pumping oil and gas out of the ground also produces large amounts of water containing polluting or undesirable chemicals. This wastewater is also called produced water. The amount of produced water relative to the amount of oil extracted from the oil field wells can vary over time and from one oil field to another. The nature of the suspended or dissolved solids and chemicals contained in the produced water can vary from well to well and over time.

[0003] High-salinity produced water is considered an industrial waste and should be disposed of safely in an environmentally acceptable manner. One way to treat produced water is to transport the water to a reservoir (usually an underground reservoir) and treat the water in the reservoir. Another way is to re-inject the produced water into oil field wells.

[0004] A large amount of power is required to transport and / or reinject produced water into underground reservoirs. Attempts have been made to address this problem and reduce the amount of power required. One way to reduce the amount of power required to transport or pump produced water is to reduce the volume of produced water to be processed.

[0005] In order to reduce the volume of produced water to be treated, it has been proposed to evaporate part of the water, for example using boilers. The steam generated by partial evaporation of the waste water is free of pollutants and contaminants and can simply be released into the atmosphere.

[0006] Natural gas from oil field wells can be used to heat boilers and generate steam, which is vented to the environment, leaving behind concentrated produced water (brine) that is ultimately disposed of.

[0007] These known methods and systems for reducing the amount of waste water are not efficient from an energy point of view. In addition, evaporating water containing high concentrations of chemicals may lead to early scaling or fouling of the boiler.

[0008] Therefore, more efficient systems and methods for treating wastewater from oilfield wells would be welcomed in the art. Summary of the invention

[0009] According to a first aspect, a wastewater treatment system is disclosed herein, comprising a burner adapted to burn a fuel and thereby generate pressurized combustion gases. The system also includes a gas turbine adapted to expand the pressurized combustion gases and thereby generate mechanical power. The system also includes a boiler adapted to receive the expanded combustion gases from the gas turbine, and the boiler fluid is coupled to a wastewater pipeline. In use, low-temperature heat from the combustion gases (flue gases) expanded in the gas turbine generates steam from the wastewater through heat exchange in the boiler. Part of the water is evaporated and released into the atmosphere, thereby reducing the volume of wastewater to be treated. The remaining wastewater is a brine containing a concentrated amount of chemicals, and is discharged and treated from the boiler through a discharge line.

[0010] The term "boiler" as understood herein includes any device adapted to transfer heat from the expanded combustion gases to the waste water and evaporate at least part of the waste water. The boiler may be an evaporator.

[0011] The option of completely evaporating the water and obtaining salts and solids as final products, which can then be disposed of, is not excluded.

[0012] The system improves overall energy efficiency by extracting mechanical power from the expansion of the combustion gases before they are used to evaporate the wastewater.

[0013] In a preferred embodiment, the burner is adapted to receive natural gas from an oil field well. Thus, the natural gas from the oil field well is used for power generation and wastewater concentration, rather than combustion, which further improves the overall energy efficiency of the system. If the natural gas from the oil field well is insufficient or unavailable, an additional fuel source can be provided in combination.

[0014] In some cases, gas from an oil field well may be delivered partly to a pipeline and / or to a natural gas liquefaction unit and partly to a gas turbine.

[0015] Natural gas from oil field wells may be pre-treated before use in gas turbines, for example to remove contaminants and heavier hydrocarbons.

[0016] The system also includes a pressure regulating device adapted to receive natural gas from an oilfield well and adapt its pressure to the combustion pressure in the burner. As will be described in more detail below, the pressure regulating device can be designed to increase or decrease the natural gas pressure depending on the pressure at which the natural gas is available at the well and on the burner pressure.

[0017] The mechanical power generated by the gas turbine may be converted into electrical power by a generator drivingly coupled to the gas turbine.

[0018] According to further embodiments, the system may further include a steam turbine adapted to receive steam from a boiler or evaporator and expand the steam to generate mechanical power. In some embodiments, the mechanical power generated by the steam turbine may be converted into electrical power by another generator drivingly coupled to the steam turbine.

[0019] In some embodiments, to further improve its energy efficiency, the system may also include a recuperator. The recuperator may include a heat exchanger having a hot side and a cold side. The brine discharge line flows through the hot side of the heat exchanger, and the wastewater line flows through the cold side of the heat exchanger, so that heat from the brine is recovered by the wastewater.

[0020] According to another aspect, a method for treating wastewater from an oilfield well is disclosed herein. The method comprises the following steps:

[0021] - generating pressurized combustion gases in a burner;

[0022] - expanding the combustion gases in a gas turbine and generating mechanical power therefrom;

[0023] - Producing steam and a brine stream from waste water by evaporating the waste water using waste heat from the expanding combustion gases.

[0024] The step of generating pressurized combustion gas in the burner includes the step of mixing natural gas from the oilfield well with air and burning the resulting air-gas mixture in the burner. If necessary, additional fuel can be fed to the burner (if the natural gas from the oilfield well is insufficient).

[0025] If necessary, the method further comprises the step of adapting the pressure of the natural gas coming from the oilfield well to the burner pressure.

[0026] According to some embodiments, the steam generated by partially evaporating the waste water may be released as is to the environment. In other embodiments, the method may further comprise the step of expanding the steam in a steam turbine and thereby generating mechanical power before releasing the waste steam to the atmosphere.

[0027] According to another aspect, the present disclosure relates to a wastewater treatment system for treating wastewater from an oilfield well, the wastewater treatment system comprising a burner adapted to burn a fuel and thereby generate pressurized combustion gases. The system also includes a gas turbine adapted to expand the pressurized combustion gases and thereby generate mechanical power. The boiler of the system is adapted to receive the expanded combustion gases from the gas turbine and is fluidly coupled to a wastewater line. In use, heat from the combustion gases generates steam from the wastewater. A brine discharge line from the boiler is used to discharge brine, and a steam turbine is adapted to receive steam from the boiler, expand the steam to generate mechanical power and release the exhaust steam into the atmosphere.

[0028] According to another aspect, the present disclosure also relates to a method for treating wastewater from an oilfield well, the method comprising the steps of generating pressurized combustion gases in a combustor; expanding the combustion gases in a gas turbine and thereby generating mechanical power; generating steam and a brine stream from the wastewater by evaporating the wastewater using waste heat from the expanded combustion gases; and expanding the steam in a steam turbine and releasing the exhaust steam into the atmosphere.

[0029] In some embodiments, the method may further comprise the step of recovering heat from the brine. For example, the method may comprise the step of preheating wastewater from an oil field by heat exchange with brine discharged from a boiler.

[0030] Further features and advantages of the systems and methods disclosed herein are described below with reference to some exemplary embodiments and are further outlined in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Reference will now be made briefly to the accompanying drawings, in which:

[0032] Figure 1 A schematic diagram illustrating a first embodiment of a system according to the present disclosure is illustrated;

[0033] Figure 2 A schematic diagram illustrating a first embodiment of an additional system according to the present disclosure;

[0034] Figure 3 illustrates a schematic diagram of a first embodiment of an additional system according to the present disclosure; and

[0035] Figure 4 , Figure 5 and Figure 6 Alternative embodiments of the pressure regulating unit are illustrated. DETAILED DESCRIPTION

[0036] In brief, according to the embodiments disclosed herein, a gaseous fuel, particularly natural gas (preferably natural gas from an oilfield well), is used to generate compressed combustion gas, which is expanded in a gas turbine to generate useful power. The exhausted combustion gas is then used as a low temperature heat source to evaporate part of the produced water (wastewater) from the oilfield well and produce a brine stream (i.e., wastewater with a higher concentration of residual chemicals and other substances), which is ultimately disposed of. Thus, the high temperature heat energy generated by the combustion of the fuel is used to generate mechanical power, while the waste heat at a lower temperature is used to evaporate water and produce brine for subsequent processing. The brine can be formed from a slurry of concentrated evaporated salts and solids.

[0037] Since the high temperature thermal energy is used to generate high quality power (mechanical power), the overall energy efficiency of the system is improved.

[0038] Turning now to the accompanying drawings, Figure 1 A first embodiment of a system according to the present disclosure is schematically shown in and 1 is marked as a whole. An oilfield well is schematically shown at 3. Oil pumped from the oilfield well 3 is transported through a pipeline 5, while wastewater (produced water) is removed through a wastewater pipeline 7. Natural gas from the oilfield well 3 can be collected in a gas pipeline 9, which is fluidly coupled to a gas turbine subsystem 11, wherein the natural gas can be used to power the gas turbine, as disclosed in more detail below. A flare 15 can be fluidly coupled to the gas pipeline 9 via a secondary gas pipeline 13. If necessary, for example if the natural gas cannot be processed in the gas turbine subsystem 11, for example when the subsystem 11 is unavailable due to, for example, maintenance or failure, valves 17, 19 can be used to partially or completely divert the natural gas from the oilfield well 3 toward the flare 15.

[0039] In some embodiments, the gas pipeline 9 may be fluidly coupled to another gas pipeline 6 to deliver the natural gas to a natural gas liquefaction unit or a gas pipeline (not shown).

[0040] In some embodiments, the gas from the oilfield well 3 may be pretreated in a pretreatment unit (not shown) to remove impurities or heavy hydrocarbons that cannot be fed to the combustor of the gas turbine subsystem 11 .

[0041] The system 1 also includes a wastewater pretreatment unit 21 along the wastewater line 7. If necessary, a pump 23 can also be set along the wastewater line 7. The wastewater pretreatment unit can include, but is not limited to, any of the following stages as needed: a de-oiling section, a pH adjustment section, a softening section, a filtration section, a preheating section, a dissolved gas removal section, and combinations thereof.

[0042] The system 1 also includes a boiler or evaporator 25 to which waste water (i.e., produced water from the oilfield wells 3) is delivered via a waste water line 7. In this specification and the appended claims, the terms "evaporator" and "boiler" may be used as synonyms and both encompass devices in which heat is used to heat and evaporate water.

[0043] As described below, part of the wastewater is evaporated in a boiler or evaporator 25 and discharged to the environment (arrow S), while the remaining water forms a brine containing concentrated amounts of salts and other chemicals and will be treated, such as conveyed to a suitable reservoir 27, or reinjected into the ground through a brine discharge pipeline 28.

[0044] The gas turbine subsystem 11 includes a pressure regulating unit 31 that is fluidly coupled to the gas pipeline 9 and is adapted to regulate the pressure of the natural gas so that it can be delivered to the combustor 33. In some embodiments, the natural gas produced by the oil field well 3 may have a pressure higher than the required pressure in the combustor 33. In this case, the natural gas from the gas pipeline 9 is reduced in pressure in the pressure regulating unit 31. The pressure regulating unit 31 may include an expansion valve.

[0045] In other embodiments, the pressure regulating unit includes an expander 34 that is drivingly coupled to a generator, or more generally coupled to an electric motor 35 that can alternately operate in a motor mode or in a generator mode. The electric motor 35 can be electrically coupled to an electric power distribution network 37. The natural gas is partially expanded in the expander 34, and the enthalpy drop of the natural gas is used to generate mechanical power available on a shaft connecting the expander 34 to the electric motor 35. The electric power generated by the electric motor operating in the generator mode is delivered to the electric power distribution network 37.

[0046] If the natural gas delivered via the gas pipeline 9 has a pressure lower than the pressure required in the burner 33, the pressure regulating unit 31 may comprise a compressor 34 and an electric motor 35 powered by an electric power distribution network 37 driving the compressor.

[0047] If the pressure of the natural gas in the gas line 9 fluctuates, such as alternately being above or below the pressure required in the burner 33, the expander and the compressor may be arranged in parallel, or the reversible turbine may be adapted to operate alternately as a compressor and expander in combination with a reversible motor.

[0048] In the combustor 33 , the mixture of compressed natural gas and compressed air is combusted to generate a flow of hot compressed combustion gases. The combustor 33 is fluidly coupled (at 39 ) to a power turbine 41 .

[0049] In some embodiments, air may be fed into the pressure regulating unit 31 through an air inlet line 32 and may be compressed by a compressor 34 along with natural gas.

[0050] Preferably, air is drawn through an air intake line 42 into a separate compressor 43 which compresses the air at the desired burner pressure and delivers the compressed air stream to the burner 33. Natural gas from the oil field well 3 is delivered to the burner 33 through the pressure regulating unit 31 at the correct burner pressure by expanding or compressing the natural gas.

[0051] The compressor 43 may be driven by the power turbine 41 , or by a separate drive, such as an electric motor (not shown).

[0052] In some embodiments, for example, if the natural gas supplied by the oil field well 3 is insufficient, fuel can be supplied to the burner 33 through an additional fuel pipeline 45. For example, the additional fuel pipeline 45 can be coupled to the gas pipeline. In some embodiments, the oil field well 3 can deliver a small amount of gas or no gas, and the natural gas required by the gas turbine subsystem 11 can be partially or completely provided by a different source (e.g., a different oil field well) through the gas pipeline 46.

[0053] As described above, since natural gas cannot be discharged into the atmosphere, if the gas turbine subsystem 11 is unavailable, the natural gas produced by the oil field well 3 must be burned in the flare 15, and for this purpose the valve 19 is closed and the valve 17 is open. In contrast, under normal operating conditions, the natural gas from the oil field well 3 is conveyed toward the gas turbine subsystem 11 through the open valve 19, while the valve 17 is completely closed or only partially opened, for example if an excess of natural gas is produced by the oil field well 3.

[0054] The exhaust fluid of the power turbine 41 is coupled to the boiler 25 so that the exhaust combustion gas flows through the boiler 25 to exchange heat with produced water from the waste water pipeline 7. The waste heat contained in the exhaust combustion gas is used to evaporate water and generate steam. Figure 1 In the embodiment of the present invention, the steam is discharged directly into the atmosphere. The exhaust and cooled combustion gases are discharged through a chimney 49, or can be treated in a carbon capture system to remove carbon dioxide before being discharged into the environment, thereby reducing greenhouse gas emissions.

[0055] Figure 1 The system 1 improves the efficiency of wastewater treatment and the production of brine therefrom in several ways. First, the heat required to partially evaporate produced water from the oilfield well 3 is at least partially generated using natural gas from the oilfield well 3. No natural gas is burned unnecessarily.

[0056] Second, the high temperature combustion gases from the combustor 33 are utilized in a gas turbine cycle to generate useful mechanical power, which can be used as such, or converted into electrical power by a generator 51 drivingly coupled to the power turbine 41. The generator 51 can be electrically coupled to the power distribution grid 37. Thus, if desired, the electrical power generated by the above-described gas turbine cycle can be used in part to operate the compressor 34 of the pressure regulating unit 31.

[0057] Continue to refer Figure 1 ,exist Figure 2 Another embodiment of the system according to the invention is schematically shown in FIG. Figure 1 The same reference numerals used in the drawings denote the same components, and description thereof will not be repeated.

[0058] Figure 1 Implementation plan and Figure 2 The main difference between the embodiments of is that the latter also includes a steam turbine subsystem 61. Subsystem 61 includes an open steam cycle that includes a steam turbine 63 that is fluidly coupled to boiler 25. Compressed steam from boiler 25 is expanded in steam turbine 63, and exhaust steam S is then released into the atmosphere. The mechanical power generated by steam turbine 63 can be converted into electrical power by generator 64, which can be electrically coupled to power distribution grid 37.

[0059] Therefore, in Figure 2 In an embodiment, the energy efficiency of the system 1 is further improved by generating additional useful power through an open bottom steam cycle including a steam turbine 63.

[0060] Continue to refer Figure 1 and Figure 2 ,exist Figure 3 Another embodiment of the system according to the present disclosure is disclosed in. The same reference numerals representing the same or equivalent components have been referenced. Figure 1 and Figure 2 It has been described and will not be described again.

[0061] Figure 3 Implementation plan and Figure 2 The embodiment of 20 differs mainly in that heat is recovered from the brine discharged from the boiler 25 and used to preheat the wastewater before feeding to the boiler 25. Heat is recovered from the brine flowing in the brine discharge line 28 by means of a heat exchanger 65. The brine flows through the hot side 65.1 of the heat exchanger 65 and exchanges heat with wastewater flowing through the wastewater line 7, which includes the cold side 65.2 of the heat exchanger 65.

[0062] The heat exchanger 65 for recovering heat from the brine may also be used according to Figure 1in the implementation scheme.

[0063] Because high temperature heat from the combustion of natural gas from oilfield wells cascades through one or both thermodynamic cycles to generate electrical power, the embodiments disclosed herein provide a more efficient method to concentrate and reduce the volume of produced water from oilfield wells.

[0064] In all embodiments, steam is generated by heat exchange with combustion gases previously expanded in a gas turbine to convert high temperature heat into mechanical power. The expanded combustion gases entering the boiler may have a temperature of, for example, about 400°C or less, which is lower than that typically employed in prior art boilers.

[0065] Lower evaporation temperatures compared to current evaporators can result in reduced boiler fouling

[0066] exist Figures 1 to 3 In the embodiment of the invention, the pressure regulating unit comprises a turbine drivingly coupled to an electric motor. The turbine can be a compressor, an expander or a reversible turbine adapted to operate as a compressor or an expander, depending on the pressure of the natural gas from the oil field. The electric motor can be operated in motor mode or in generator mode accordingly.

[0067] In other embodiments, where the natural gas is expected to be at a pressure higher than the burner pressure, the pressure regulating unit 31 may include a simple throttling or laminating valve that is adjustable to handle the natural gas at a variable pressure. An exemplary embodiment of the pressure regulating unit 31 including a simple pressure regulating valve 81 is shown in Figure 4 Shown in.

[0068] In an alternative embodiment, the pressure regulating unit may include a pressure regulating valve, such as a throttling valve or a laminating valve combined with an expander. The pressure regulating valve may be arranged upstream of the expander or downstream of the expander with respect to the flow direction of the natural gas. Figure 5 The pressure regulating unit 31 is schematically shown and includes an expander 83 drivingly coupled to a generator 35 electrically connected to an electric power distribution network 37. A pressure regulating valve 85A is arranged upstream of the expander 83. Alternatively or in combination, a pressure regulating valve 85B may be arranged downstream of the expander 83.

[0069] In yet another embodiment, the pressure regulating unit 31 may comprise a more complex arrangement of devices adapted to increase or decrease the pressure of the natural gas at the oilfield well as required. Figure 6A pressure regulating valve 81 is shown in parallel with the expander 83 and the compressor 91. The expander 83 is drivingly coupled to the generator 35A, which is in turn electrically coupled to the power distribution network 37. The compressor 91 is drivingly coupled to the motor 35B, which is in turn electrically connected to the power distribution network 37. Closing valves can be set on the inlet and outlet sides of the expander 83 and the suction and delivery sides of the compressor 91. In the figure, valves 93, 95, 97, and 99 are provided. In some embodiments, valve 95 and valve 99 can be omitted. As a supplement or alternative to one or both valves 93, 95, corresponding pressure regulating valves 85A and 85B can be foreseen to adjust the pressure at the inlet of the expander 83 and / or at the outlet of the expander 83, thereby adjusting the pressure drop across the expander.

[0070] Figure 6 The pressure regulating unit 31 can be operated in different modes. In one operating mode, valves 93, 95, 97, 99 can be closed and the pressure regulating valve 81 adjusts the pressure of the natural gas of the oil field well to the required burner pressure. Alternatively, the natural gas can be expanded by the expander 83 keeping valves 93, 95 open and valves 97, 99, 81 closed. If necessary, valves 85A, 85B or one of them can be used to adjust the inlet or outlet pressure of the expander, if necessary. If the pressure of the natural gas of the oil field well is lower than the burner pressure, valves 93, 95, 81 can be closed and valves 97, 99 can be opened to pressurize the natural gas to the required burner pressure.

[0071] Exemplary embodiments have been disclosed above and illustrated in the accompanying drawings. Those skilled in the art will appreciate that various changes, omissions and additions may be made to the specific disclosure herein without departing from the scope of the present invention as defined in the following claims.

Claims

1. A wastewater treatment system for treating wastewater from an oilfield well; the system comprising: Oilfield wells; a burner adapted to combust a fuel and thereby generate pressurized combustion gases; wherein the burner is adapted to receive natural gas from an oil field via a gas pipeline; a pressure regulating device adapted to receive natural gas from the oil field and to adapt its pressure to the combustion pressure in the burner; a gas turbine adapted to expand the pressurized combustion gases and generate mechanical power therefrom; a boiler adapted to receive expanded combustion gases from the gas turbine and fluidly coupled to a wastewater line conveying wastewater from the oilfield well; wherein, in use, heat from the combustion gases generates steam from the wastewater; as well as A brine discharge line from the boiler.

2. The system according to claim 1, wherein the pressure regulating device comprises a turbine, which is drivingly coupled to an electric motor, the turbine operates as a compressor or as an expander, and the electric motor operates in a motor mode or in a generator mode.

3. The system of any of the preceding claims, further comprising a first generator drivingly coupled to the gas turbine and adapted to convert mechanical power generated by the gas turbine into electrical power.

4. The system of any one of the preceding claims, further comprising a steam turbine adapted to receive steam from the boiler and expand the steam to generate mechanical power. 5 . The system of claim 4 , further comprising a second generator drivingly coupled to the steam turbine and adapted to convert mechanical power generated by the steam turbine into electrical power.

6. The system according to any one of the preceding claims, further comprising a wastewater pre-treatment unit.

7. The system of claim 6, wherein the wastewater pretreatment unit comprises at least one of the following: a de-oiling section, a pH adjustment section, a softening section, a filtration section, a preheating section, a dissolved gas removal section, or a combination thereof.

8. A system according to any of the preceding claims, further comprising a heat exchanger having a hot side and a cold side; wherein the brine discharge pipeline flows through the hot side of the heat exchanger, and wherein the wastewater pipeline flows through the cold side of the heat exchanger so that heat from the brine is recovered by the wastewater.

9. A method for treating wastewater from an oilfield well, the method comprising the steps of: transporting natural gas from the oil fields to the burners; Adapting the pressure of the natural gas from the oil field to the burner pressure; mixing natural gas from the oilfield well and compressed air in the combustor and combusting the resulting air-gas mixture and generating pressurized combustion gas; causing the combustion gases to expand in a gas turbine and thereby generate mechanical power; and Steam and a brine stream are produced from the waste water by evaporating the waste water using waste heat from the expanding combustion gases.

10. The method of claim 9, wherein the step of adapting the pressure of the natural gas comprises the step of compressing the natural gas or expanding the natural gas.

11. The method of claim 10, wherein the step of compressing the natural gas or the step of expanding the natural gas comprises the step of processing the natural gas in a turbine drivingly coupled to an electric machine; wherein, The motor provides power to drive the turbine when the natural gas is compressed, and generates power when the natural gas expands.

12. A method according to any one of claims 9 to 11, further comprising the step of venting the steam to the environment.

13. A method according to any one of claims 9 to 12, further comprising the step of converting the mechanical power generated by the gas turbine into electrical power.

14. A method according to any one of claims 9 to 13, further comprising the step of expanding the steam in a steam turbine and generating mechanical power thereby.

15. The method of claim 14, further comprising the step of converting the mechanical power generated by the steam turbine into electrical power.

16. The method according to any one of claims 9 to 15, further comprising the step of preheating the waste water by heat exchange with the brine discharged from the boiler.

17. A wastewater treatment system for treating wastewater from an oilfield well; the system comprising: a burner adapted to combust a fuel and thereby generate pressurized combustion gases, a gas turbine adapted to expand the pressurized combustion gases and generate mechanical power therefrom; a boiler adapted to receive expanded combustion gases from the gas turbine and fluidly coupled to a wastewater line; wherein in use, heat from the combustion gases generates steam from the wastewater; a brine discharge line from said boiler; as well as A steam turbine is adapted to receive steam from the boiler, expand the steam to generate mechanical power and release exhaust steam to the atmosphere.

18. The system of claim 17, further comprising a first generator drivingly coupled to the gas turbine and adapted to convert mechanical power generated by the gas turbine into electrical power.

19. The system of claim 17 or 18, further comprising a second generator drivingly coupled to the steam turbine and adapted to convert mechanical power generated by the steam turbine into electrical power.

20. The system according to any one of claims 17 to 19, further comprising a wastewater pre-treatment unit.

21. The system of claim 20, wherein the wastewater pretreatment unit comprises at least one of the following: a de-oiling section, a pH adjustment section, a softening section, a filtration section, a preheating section, a dissolved gas removal section, or a combination thereof.

22. The system of any one of claims 17 to 21, further comprising a heat exchanger having a hot side and a cold side; wherein the brine discharge line flows through the hot side of the heat exchanger, and wherein the wastewater line flows through the cold side of the heat exchanger such that heat from the brine is recovered by the wastewater.

23. A method for treating wastewater from an oilfield well, the method comprising the steps of: generating pressurized combustion gases in a combustor; causing the combustion gases to expand in a gas turbine and thereby generate mechanical power; producing steam and a brine stream from the wastewater by evaporating the wastewater using waste heat from the expanded combustion gases; and The steam is expanded in a steam turbine and exhaust steam is released into the atmosphere.

24. The method of claim 23, further comprising the step of converting the mechanical power generated by the gas turbine into electrical power.

25. A method according to claim 23 or 24, further comprising the step of converting the mechanical power generated by the steam turbine into electrical power.

26. A method according to any one of claims 23 to 25, further comprising the step of preheating the waste water by heat exchange with the brine discharged from the boiler.

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