System and method for treating wastewater from oil field wells with power co-production

Abstract

The wastewater treatment system includes a combustor (33) adapted to combust a fuel, thereby generating pressurized combustion gases. The system also includes a gas turbine (41) adapted to expand the pressurized combustion gases, thereby generating mechanical power. The system further includes a boiler (25) adapted to receive the expanded combustion gases from the gas turbine (41). The boiler is fluidly coupled to the wastewater line (7). In use, heat from the combustion gases generates steam from the wastewater, and brine is removed from the boiler through the brine discharge line (28). In some embodiments, a steam cycle is also provided within the system to extract additional power.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE This disclosure relates to wastewater treatment, and more particularly to systems and methods for treating wastewater from oilfield wells. [Background technology]

[0002] Pumping oil and gas from the ground also produces large amounts of water containing contaminants or undesirable chemicals. This wastewater is also known as produced water. The amount of produced water relative to the oil extracted from an oil field well can vary over time and from field to field. 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] Produced water, which is highly saline, is considered an industrial waste and must be safely disposed of in an environmentally acceptable manner. One method of disposing of produced water is to transfer the water to a reservoir, usually an underground reservoir, and dispose of the water there. Another method is to reinject 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 treated.

[0005] To reduce the volume of produced water to be disposed of, it has been proposed to evaporate a portion of the water, for example, using a boiler. The steam generated by partial evaporation of the wastewater is free of pollutants and pollutants 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 therefore ultimately disposed of.

[0007] These known methods and systems for reducing the amount of wastewater are not energy efficient. Moreover, vaporizing water containing high concentrations of chemicals can lead to premature scaling or fouling of the boiler.

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

[0009] According to a first aspect, disclosed herein is a wastewater treatment system including a combustor adapted to combust a fuel, thereby generating pressurized combustion gases. The system further includes a gas turbine adapted to expand the pressurized combustion gases, thereby generating mechanical power. The system also includes a boiler adapted to receive the expanded combustion gases from the gas turbine and fluidly coupled to a wastewater line. In use, low-temperature heat from the combustion gases (flue gases) expanded in the gas turbine generates steam from the wastewater by heat exchange in the boiler. A portion of the water evaporates and is released into the atmosphere, thereby reducing the volume of wastewater to be disposed of. The remaining wastewater, which is brine containing concentrated amounts of chemicals, is discharged from the boiler through a discharge line and disposed of.

[0010] As understood herein, the term "boiler" includes any device adapted to transfer heat from expanding combustion gases to wastewater and evaporate at least a portion of the wastewater. A boiler may be an evaporator.

[0011] The option of completely evaporating the water and obtaining salts and solids as the final product, which are then 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 combustor is adapted to receive natural gas from an oil field well. The natural gas from the oil field well is therefore used for power generation and concentration of wastewater rather than being flared, which further increases the overall energy efficiency of the system. If 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 partially to a pipeline and / or natural gas liquefaction unit and partially to a gas turbine.

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

[0016] The system further includes a pressure regulating device adapted to receive the natural gas from the oil field well and adjust its pressure to match the combustion pressure in the combustor. As 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 the combustor pressure.

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

[0019] In some embodiments, to further improve its energy efficiency, the system can further include a heat recovery device. The heat recovery device can 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, such that heat from the brine is recovered by the wastewater.

[0020] According to a further aspect, disclosed herein is a method for treating wastewater from an oil field well, the method comprising: generating pressurized combustion gases in a combustor; expanding the combustion gases in a gas turbine, thereby producing mechanical power; - producing a steam and brine stream from the wastewater by evaporating the wastewater using waste heat from the expanding combustion gases.

[0021] Generating pressurized combustion gas in the combustor includes mixing natural gas from the oil field well with air and burning the resulting air-gas mixture in the combustor. If the natural gas from the oil field well is insufficient, additional fuel can be supplied to the combustor as needed.

[0022] The method further includes, if necessary, matching the pressure of the natural gas from the oil field well to the combustor pressure.

[0023] According to some embodiments, the steam generated by partially evaporating the wastewater may be directly released into the environment. In other embodiments, the method may further include expanding the spent steam in a steam turbine, thereby generating mechanical power, before releasing the spent steam into the atmosphere.

[0024] According to a further aspect, the present disclosure relates to a wastewater treatment system for treating wastewater from oil field wells, comprising a combustor adapted to combust fuel and thereby generate pressurized combustion gases, the system further comprising a gas turbine adapted to expand the pressurized combustion gases and thereby generate mechanical power. A boiler of the system is adapted to receive the expanded combustion gases from the gas turbine and is fluidly coupled to the 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 the brine, and a steam turbine is adapted to receive steam from the boiler, expand the steam to generate mechanical power, and discharge the spent steam to the atmosphere.

[0025] According to a further aspect, the present disclosure also relates to a method for treating wastewater from an oil field well, the method including generating pressurized combustion gases in a combustor; expanding the combustion gases in a gas turbine to thereby produce mechanical power; producing steam and a brine stream from the wastewater by evaporating the wastewater using waste heat from the expanded combustion gases; expanding the steam in the steam turbine and releasing the spent steam to the atmosphere.

[0026] In some embodiments, the method may further include recovering heat from the brine. For example, the method may include preheating wastewater from an oil field by heat exchange with the brine discharged from the boiler.

[0027] Additional features and advantages of the systems and methods disclosed herein are described below with reference to some exemplary embodiments and are further set forth in the appended claims. [Brief explanation of the drawings]

[0028] Reference will now be made briefly to the accompanying drawings, in which: [Figure 1] 1 illustrates a schematic diagram of a first embodiment of a system according to the present disclosure. [Figure 2]1 illustrates a schematic diagram of a first embodiment of a further system according to the present disclosure. [Figure 3] 1 illustrates a schematic diagram of a first embodiment of a further system according to the present disclosure. [Figure 4] 10 illustrates an alternative embodiment of a pressure regulation unit. [Figure 5] 10 illustrates an alternative embodiment of a pressure regulation unit. [Figure 6] 10 illustrates an alternative embodiment of a pressure regulation unit. DETAILED DESCRIPTION OF THE INVENTION

[0029] Briefly, according to embodiments disclosed herein, a gaseous fuel, particularly natural gas, preferably from an oil field well, is used to generate compressed combustion gases, which are expanded in a gas turbine to produce useful power. The flue gases are then used as a lower-temperature heat source to vaporize a portion of the produced water (wastewater) from the oil field well and produce a brine stream, i.e., wastewater with a higher concentration of residual chemicals and other materials, for eventual disposal. Thus, the high-temperature thermal power generated by the combustion of the fuel is used to generate mechanical power, while the lower-temperature waste heat is used to vaporize the water and produce brine for subsequent disposal. Brine can be formed by a slurry of concentrated vaporized salts and solids.

[0030] The high temperature thermal energy is used to generate high quality power (mechanical power), improving the overall energy efficiency of the system.

[0031] Referring now to the drawings, a first embodiment of a system according to the present disclosure is shown schematically in FIG. 1 and generally labeled 1. An oil field well is shown generally at 3. Oil pumped from oil field well 3 is delivered through duct 5, while wastewater (produced water) is removed through wastewater line 7. Natural gas from oil field well 3 may be collected in gas line 9 fluidly coupled to gas turbine subsystem 11, where the natural gas may be used to power the gas turbine, as disclosed in more detail below. Flare 15 may be fluidly coupled to gas line 9 through secondary gas line 13. Valves 17, 19 may be used to partially or completely divert natural gas from oil field well 3 to flare 15 as needed, for example, when the natural gas cannot be processed in gas turbine subsystem 11, for example, when subsystem 11 is unavailable, for example, due to maintenance or failure.

[0032] In some embodiments, the gas line 9 may be fluidly coupled to a further gas line 6 to deliver the natural gas to a natural gas liquefaction unit or a gas pipeline (not shown).

[0033] In some embodiments, the gas from the oil field well 3 may be pre-treated in a pre-treatment unit (not shown) to remove impurities or heavy hydrocarbons that cannot be fed to the combustor of the gas turbine subsystem 11.

[0034] The system 1 further comprises a wastewater pretreatment unit 21 along the wastewater line 7. If necessary, a pump 23 may further be provided along the wastewater line 7. The wastewater pretreatment unit may 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 pre-heating section, a dissolved gas removal section, or combinations thereof.

[0035] System 1 further comprises a boiler or evaporator 25 to which wastewater, i.e., produced water from oil field wells 3, is delivered through wastewater line 7. In this specification and the appended claims, the terms "evaporator" and "boiler" may be used synonymously and both encompass devices that use heat to heat and evaporate water.

[0036] As explained below, a portion of the wastewater is vaporized in a boiler or evaporator 25 and discharged to the environment (arrow S), while the remaining water forms brine containing concentrated amounts of salts and other chemicals and is disposed of, for example, by being transferred through a brine discharge line 28 to a suitable reservoir 27 or by being reinjected into the ground.

[0037] Gas turbine subsystem 11 includes a pressure regulation unit 31 that is fluidly coupled to gas line 9 and adapted to regulate the pressure of the natural gas so that it can be delivered to combustor 33. In some embodiments, the natural gas produced by oil field well 3 may have a higher pressure than required in combustor 33. In such cases, the natural gas from gas line 9 is depressurized in pressure regulation unit 31. Pressure regulation unit 31 may include an expansion valve.

[0038] In other embodiments, the pressure regulation unit comprises an expander 34 that may be drivingly coupled to a generator, or more generally, to an electric machine 35 that may alternately operate in motor or generator mode. The electric machine 35 may be electrically coupled to an electrical power distribution grid 37. The natural gas is partially expanded in the expander 34, and the enthalpy drop of the natural gas is used to generate available mechanical power on a shaft connecting the expander 34 to the electric machine 35. Electrical power generated by the electric machine operating in generator mode is supplied to the electrical power distribution grid 37.

[0039] If the natural gas delivered through the gas line 9 has a lower pressure than that required in the combustor 33, the pressure regulating unit 31 may include a compressor 34 and an electric machine 35 powered by a power distribution network 37 that drives the compressor.

[0040] If the pressure of the natural gas in the gas line 9 fluctuates alternately higher or lower than the pressure required in the combustor 33, an expander and compressor may be provided in parallel, or a reversible turbomachine may be provided that is adapted to operate alternately as a compressor and expander in combination with a reversible electric machine.

[0041] In combustor 33, a mixture of compressed natural gas and compressed air is combusted to generate a flow of hot compressed combustion gases. Combustor 33 is fluidly coupled (at 39) to a power turbine 41.

[0042] In some embodiments, air may be supplied into pressure regulation unit 31 through air inlet line 32 and compressed by compressor 34 along with natural gas.

[0043] Preferably, air is drawn through an air suction line 42 to a separate compressor 43 which compresses the air at the required combustor pressure and delivers the compressed air stream to the combustor 33. Natural gas is delivered to the combustor 33 through a pressure regulation unit 31 at the correct combustor pressure by expanding or compressing natural gas from the oil field wells 3.

[0044] The compressor 43 may be driven by the power turbine 41 or by a separate drive device such as an electric motor (not shown).

[0045] In some embodiments, for example, if the natural gas supplied by oil field well 3 is insufficient, fuel may be supplied to combustor 33 through additional fuel line 45. Additional fuel line 45 may be coupled to, for example, a gas pipeline. In some embodiments, oil field well 3 may deliver little or no gas, and the natural gas needed by gas turbine subsystem 11 may be partially or completely provided by a different source, for example, a different oil field well, through gas pipeline 46.

[0046] As mentioned above, natural gas cannot be released into the atmosphere, so when gas turbine subsystem 11 is unavailable, the natural gas produced by oil field well 3 must be burned in flare 15, for which reason valve 19 is closed and valve 17 is open. Conversely, under normal operating conditions, natural gas from oil field well 3 is delivered through open valve 19 towards gas turbine subsystem 11, while valve 17 is either fully closed or only partially open when excess natural gas is produced by oil field well 3.

[0047] The exhaust of power turbine 41 is fluidly coupled to boiler 25 so that the flue gas flows through boiler 25 in heat exchange with product water from wastewater line 7. Waste heat contained in the flue gas is used to evaporate water and generate steam, which, in the embodiment of Figure 1, is exhausted directly to the atmosphere. The exhausted and cooled flue gas is exhausted through exhaust stack 49 or can be treated in a carbon capture system for carbon dioxide removal before being exhausted to the environment, thus reducing greenhouse gas emissions.

[0048] 1 improves the efficiency of wastewater treatment and the production of brine from wastewater treatment in several ways. First, the heat required for the partial vaporization of produced water from oil field wells 3 is generated at least in part by utilizing natural gas from oil field wells 3. Natural gas is not unnecessarily flared.

[0049] Second, the hot combustion gases from the combustor 33 are utilized in a gas turbine cycle to generate useful mechanical power that can be used directly or converted to electrical power through a generator 51 drivingly coupled to the power turbine 41. The generator 51 can be electrically coupled to the electrical power distribution grid 37. Thus, the electrical power generated by the gas turbine cycle described above can be used in part to operate the compressor 34 of the pressure regulation unit 31, if required.

[0050] With continuing reference to Figure 1, a further embodiment of a system according to the present invention is shown schematically in Figure 2. The same reference numerals used in Figure 1 designate the same parts, which will not be described again.

[0051] 1 and 2 is that the latter further includes a steam turbine subsystem 61. Subsystem 61 comprises an open steam cycle including a steam turbine 63 fluidly coupled to boiler 25. Compressed steam from boiler 25 expands in steam turbine 63, and exhaust steam S is discharged to the atmosphere. Mechanical power generated by steam turbine 63 can be converted to electrical power by a generator 64, which can be electrically coupled to electrical power distribution grid 37.

[0052] Thus, in the embodiment of FIG. 2, additional useful power is generated by the open-bottom steam cycle including the steam turbine 63, further improving the energy efficiency of the system 1.

[0053] With continued reference to Figures 1 and 2, a further embodiment of a system according to the present disclosure is disclosed in Figure 3. Parts that are the same as or equivalent to those already described with reference to Figures 1 and 2 are designated with the same reference numerals and will not be described again.

[0054] The embodiment of Figure 3 differs from the embodiment of Figure 2 primarily in that heat is recovered from the brine discharged from boiler 25 and used to preheat wastewater before feeding it to boiler 25. Heat is recovered from the brine flowing in brine discharge line 28 through heat exchanger 65. The brine flows through the hot side 65.1 of heat exchanger 65 and exchanges heat with wastewater flowing through wastewater line 7, including the cold side 65.2 of heat exchanger 65.

[0055] A heat exchanger 65 for recovering heat from the brine can also be used in the embodiment according to FIG.

[0056] The embodiments disclosed herein provide a more efficient approach to the concentration and volume reduction of produced water from oil field wells, as high temperature heat from the combustion of natural gas from the oil field wells is cascaded to generate power through one or two thermodynamic cycles.

[0057] In all embodiments, steam is generated by heat exchange with combustion gases that have been 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, approximately 400° C. or less, which is lower than temperatures typically employed in current technology boilers.

[0058] Lower evaporation temperatures compared to current evaporators may result in reduced scaling of the boiler.

[0059] 1-3, the pressure regulation unit comprises a turbomachine drivingly coupled to an electric machine. The turbomachine may be a compressor, an expander, or a reversible turbomachine adapted to operate as a compressor or an expander depending on the pressure of the natural gas from the oil field. The electric machine may therefore operate in a motor mode or a generator mode.

[0060] In other embodiments where natural gas at pressures higher than the combustor pressure is anticipated, the pressure regulation unit 31 may include a single throttle valve or a stack of valves that may be adjustable to handle natural gas at variable pressures. A schematic embodiment of a pressure regulation unit 31 including a single pressure regulation valve 81 is shown in FIG.

[0061] In alternative embodiments, the pressure regulation unit may include a pressure regulation valve, such as a throttle valve or stacked valve, combined with an expander. The pressure regulation valve may be located upstream of the expander or downstream of the expander with respect to the direction of natural gas flow. FIG. 5 schematically illustrates a pressure regulation unit 31 comprising an expander 83 drivingly coupled to a generator 35 electrically connected to a power distribution grid 37. A pressure regulation valve 85A is located upstream of the expander 83. Alternatively, or in combination, a pressure regulation valve 85B may be located downstream of the expander 83.

[0062] In yet another embodiment, the pressure regulation unit 31 can include a more complex arrangement of devices adapted to increase or decrease the pressure of the natural gas in the oilfield well, as needed. FIG. 6 illustrates a pressure regulation valve 81 in parallel with an expander 83 and a compressor 91. The expander 83 is drivingly coupled to a generator 35A, which is in turn electrically coupled to the power distribution grid 37. The compressor 91 is drivingly coupled to an electric motor 35B, which is in turn electrically connected to the power distribution grid 37. Shut-off valves may be provided on the inlet and outlet sides of the expander 83 and on the suction and delivery sides of the compressor 91. In the figure, valves 93, 95, 97, and 99 are provided. In some embodiments, valves 95 and 99 may be omitted. In addition to, or instead of, one or both of the valves 93 and 95, respective pressure regulation valves 85A and 85B may be envisioned to regulate the pressure at the inlet of the expander 83 and / or the outlet of the expander 83 to regulate the pressure drop across the expander.

[0063] The pressure regulation unit 31 of FIG. 6 can operate in different modes. In one mode of operation, valves 93, 95, 97, and 99 can be closed, and pressure regulation valve 81 regulates the pressure of the oilfield well natural gas at the required combustor pressure. Alternatively, the natural gas can be expanded through expander 83 with valves 93 and 95 open and valves 97, 99, and 81 closed. If needed, valves 85A and 85B, or one of them, can be used to regulate the expander inlet or outlet pressure as needed. If the pressure of the oilfield well natural gas falls below the combustor pressure, valves 93, 95, and 81 can be closed, and valves 97 and 99 can be opened to pressurize the natural gas at the required combustor pressure.

[0064] Exemplary embodiments are disclosed above and shown in the accompanying drawings. Those skilled in the art will understand that various modifications, omissions, and additions may be made to what is specifically disclosed herein without departing from the scope of the invention as defined in the claims that follow.

Claims

1. 1. A wastewater treatment system for treating wastewater from an oil field well, said system comprising: Oil field wells, a combustor adapted to combust a fuel and thereby generate pressurized combustion gases, the combustor adapted to receive oil field natural gas through a gas line; a pressure regulating device adapted to receive the oil field natural gas and adjust its pressure to match the combustion pressure within the combustor; a gas turbine adapted to expand the compressed combustion gases thereby producing mechanical power; a boiler adapted to receive expanded combustion gases from the gas turbine and fluidly coupled to a wastewater line delivering wastewater from the oil field well, wherein, in use, heat from the combustion gases generates steam from the wastewater; and a brine discharge line from said boiler.

2. 10. The system of claim 1, wherein the pressure regulation device comprises a turbomachine drivingly coupled to an electric machine, the turbomachine operating as a compressor or an expander, and the electric machine operating in a motor mode or a generator mode.

3. The system of claim 1 or 2, 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. 4. The system of claim 1, 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 claims 1 to 5, further comprising a wastewater pre-treatment unit.

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

8. 8. The system of any one of claims 1 to 7, 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 the wastewater line flows through the cold side of the heat exchanger, such that heat from the brine is recovered by the wastewater.

9. 1. A method for treating wastewater from an oil field well, comprising: delivering the oil field natural gas to a combustor; adjusting the pressure of the natural gas from the oil field to a combustor pressure; mixing the natural gas from the oil field well with compressed air and combusting the resulting air-gas mixture in the combustor to generate pressurized combustion gases; expanding the combustion gases in a gas turbine, thereby producing mechanical power; and generating a steam and brine stream from the wastewater by evaporating the wastewater using waste heat from the expanding combustion gas.

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

11. 11. The method of claim 10, wherein the step of compressing the natural gas or the step of expanding the natural gas includes processing the natural gas in a turbomachine drivingly coupled to an electric machine, the electric machine providing power to drive the turbomachine when the natural gas is compressed and the electric machine generating power when the natural gas is expanded.

12. The method of any one of claims 9 to 11, further comprising the step of venting the vapor to the environment.

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

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

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

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

17. 1. A wastewater treatment system for treating wastewater from an oil field well, said system comprising: a combustor adapted to combust a fuel thereby generating pressurized combustion gases; a gas turbine adapted to expand the compressed combustion gases thereby producing mechanical power; 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; and a brine discharge line from the boiler; a steam turbine adapted to receive steam from the boiler, expand the steam to generate mechanical power, and discharge spent 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. 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. 21. The system of claim 20, wherein the wastewater pretreatment unit comprises at least one of a de-oiling section, a pH adjustment section, a softening section, a filtration section, a pre-heating section, a dissolved gas removal section, or combinations thereof.

22. 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 the wastewater line flows through the cold side of the heat exchanger, such that heat from the brine is recovered by the wastewater.

23. 1. A method for treating wastewater from an oil field well, comprising: generating pressurized combustion gases in a combustor; expanding the combustion gases in a gas turbine, thereby producing mechanical power; generating a steam and brine stream from the wastewater by evaporating the wastewater using waste heat from the expanding combustion gas; expanding the steam in a steam turbine and venting the spent steam to the atmosphere.

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

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

26. 26. The method of any one of claims 23 to 25, further comprising the step of preheating the wastewater by heat exchange with the brine discharged from a boiler.

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