Gravity-assisted multiphase geothermal reinjection system and method
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- NUOVO PIGNONE TECH SRL
- Filing Date
- 2024-07-25
- Publication Date
- 2026-08-03
Smart Images
Figure 2026525743000001_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to a system and method for reinjecting used geothermal fluid in a geothermal facility.
Background Art
[0002] Geothermal fluid having a high enthalpy content is often, but not exclusively, used as an energy source for various types of facilities for generating electric power or mechanical power. Geothermal fluid, which is either in the form of steam or in the form of a two-phase fluid containing steam and hot water, also usually contains a certain amount of non-condensable gas.
[0003] Non-condensable gas is mixed into the geothermal steam from the production well and remains in the gas phase after the steam is condensed when delivering its energy to the power plant. In other cases, when the geothermal fluid from the production well is in the liquid phase (brine), it can be associated with reinjecting the non-condensable gas, which may require compression, into the reinjection well together with the used liquid brine. Non-condensable gas can include, inter alia, carbon dioxide (CO2), methane (CH4), hydrogen (H2), ammonia (NH3), and hydrogen sulfide (H2S).
[0004] A common method for treating non-condensable gas from geothermal fluid was to separate the non-condensable gas from the geothermal resource and treat the toxic components (e.g., H2S, etc.) to avoid its release into the environment. However, most of the non-condensable gas released in geothermal plants is non-toxic greenhouse gases such as CH4 and CO2. Conventionally, the greenhouse gases generated by the utilization of geothermal energy have simply been released into the atmosphere.
[0005] However, in recent years, concerns about environmental impacts and awareness of the effects of greenhouse gases on climate change have increased, making it necessary to reduce or eliminate emissions of these gases into the environment. New geothermal power plants must be zero-emission in order to be considered a renewable resource and to take advantage of higher feed-in tariff schemes.
[0006] Currently, technologies for reinjecting spent two-phase geothermal fluids containing non-condensable gases are under investigation (see Vlasios Leontidis, et al., "Modelling reinjection of two-phase non-condensable gases and water in geothermal wells" in Applied Thermal Engineering; 223(2023)120018, available at https: / / doi-org / 10.1016 / j.applthermaleng.2023.120018).
[0007] Reciprocating compressors, commonly used to reinject non-condensable gases from spent geothermal fluids into geothermal reinjection wells, are a cumbersome and costly part of the equipment. Reciprocating compressors can increase the overall plant CAPEX by up to 10% compared to conventional plants where greenhouse non-condensable gases are simply released into the environment without reinjection, and can also reduce net power output by approximately 5% (due to the power required to operate the compressor). Due to the high cost of reciprocating compressors, providing redundant compressors for reinjection purposes is impractical. As a result, plant utilization is reduced by up to 4%, and maintenance and operating costs increase by up to 20%.
[0008] These factors make the use of geothermal energy unattractive.
[0009] Therefore, there is a need to mitigate the drawbacks associated with the reinjection of non-condensable gases in geothermal power plants or similar facilities that utilize geothermal fluids. [Overview of the project]
[0010] According to one embodiment, a system for reinjecting spent geothermal liquid and non-condensable geothermal gas into a geothermal reinjection well is disclosed. The system comprises a gas-liquid separator having an inlet, a gas outlet, and a liquid outlet. The system further includes a first vessel, a second vessel, a pump unit having a suction side and a delivery side, and a fluid connection to a geothermal reinjection well. The suction side of the pump unit is adapted to be selectively fluid-coupled with the lower side of the gas-liquid separator, the lower side of the first vessel, and the lower side of the second vessel. The delivery side of the pump unit is adapted to be selectively fluid-coupled with the first vessel and the second vessel. The gas outlet of the gas-liquid separator is adapted to be selectively fluid-coupled with the upper side of the first vessel and the upper side of the second vessel. The fluid connection to the geothermal reinjection well is adapted to be selectively fluid-coupled with the upper side of the first vessel and the upper side of the second vessel.
[0011] Two vessels are alternately filled and emptied by a pump unit through suitably controlled valves. The variable volume above the liquid in each vessel is used to draw in, compress, and deliver non-condensable gas from the gas-liquid separator into the geothermal reinjection well. Intermittently, the liquid is also pumped into the reinjection well to form a liquid column or act as a piston within the geothermal reinjection well, which, using gravity, further compresses the gas pockets previously formed within the well. As the liquid column and gas pockets move deeper into the geothermal reinjection well, the pressure and mixing of liquid and gas result in the formation of a single-phase flow, if teaching geological formations. Variable gas composition and gas / liquid ratios can be accommodated by suitable timing of different pump phases, as will be described in detail below with reference to non-limiting embodiments.
[0012] In another aspect, this specification discloses a method for reinjecting geothermal liquids and non-condensable geothermal gases from an exhaust geothermal fluid flow into a geothermal reinjection well, the method comprising the following steps: (i) A step of pumping a pressurized non-condensable gas pocket into a geothermal reinjection well, (ii) A step of pumping a column of pressurized liquid into a geothermal reinjection well over a pocket of pressurized noncondensable gas, (iii) a step of repeating steps (i) and (ii).
[0013] According to several embodiments, a method is provided for reinjecting geothermal liquids and non-condensable geothermal gases from an exhaust geothermal fluid flow into a geothermal reinjection well, the method comprising the following steps: A step of delivering a flow of spent geothermal fluid containing a liquid phase and non-condensable gas into a gas-liquid separator, A step of selectively delivering a non-condensable gas from the gas outlet of a gas-liquid separator into at least a first container and a second container, A step of pumping the liquid from the gas-liquid separator into at least one of the first container and the second container, A step of pumping the liquid from one of the first container and the second container into the other of the first container and the second container, The process includes the step of sequentially delivering a pressurized non-condensable gas pocket and a liquid column from at least one of the first and second containers into a geothermal reinjection well.
[0014] Embodiments disclosed herein provide a method for reinjecting geothermal liquids and non-condensable geothermal gases from the exhaust geothermal fluid flow into a geothermal reinjection well. The method involves the following steps: A step of delivering a flow of spent geothermal fluid containing a liquid phase and non-condensable gas into a gas-liquid separator having an inlet, a gas outlet, and a liquid outlet. A step in a pumping system to supply liquid separately from the liquid outlet of a gas-liquid separator and non-condensable gas separately from the gas outlet of a gas-liquid separator, wherein the pumping system comprises at least a first vessel and a second vessel adapted to be selectively fluid-coupled to a gas-liquid separator and a geothermal reinjection well, and a pump unit for pumping the liquid from one of the first and second vessels to the other of the first and second vessels and into the geothermal reinjection well, sequentially pumping the pockets of pressurized non-condensable gas and the columns of liquid from the first and second vessels into the geothermal reinjection well from the system. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Reference is now made briefly to the accompanying drawings. [Figure 1] FIG. 1 is a schematic diagram of a geothermal power plant for the purpose of power generation using a Rankine cycle operated by high enthalpy geothermal fluid. [Figure 2A] FIG. 2 shows a reinjection system and the sequence of its operation in one embodiment. [Figure 2B] FIG. 2 shows a reinjection system and the sequence of its operation in one embodiment. [Figure 2C] FIG. 2 shows a reinjection system and the sequence of its operation in one embodiment. [Figure 3] FIG. 3 shows a schematic diagram of a reinjection well in which a non-condensable gas pocket and a column of liquid are formed inside using the system according to the present disclosure. [Figure 4] FIG. 4 shows a further embodiment of the reinjection system according to the present disclosure. [Figure 5A] FIG. 5 shows the sequence of operation of the system according to the present disclosure in a further embodiment. [Figure 5B] FIG. 5 shows the sequence of operation of the system according to the present disclosure in a further embodiment. [Figure 5C] FIG. 6 shows the sequence of operation of the system according to the present disclosure in a further embodiment. [Figure 5D] FIG. 7 shows the sequence of operation of the system according to the present disclosure in a further embodiment. [Figure 6A] FIG. 8 shows the sequence of operation of the system according to the present disclosure in a further embodiment. [Figure 6B] FIG. 9 shows the sequence of operation of the system according to the present disclosure in a further embodiment. [[ID=4�]] [Figure 6C] FIG. 10 shows the sequence of operation of the system according to the present disclosure in a further embodiment. [Figure 6D]Shows the sequence of operations of the system of the present disclosure in a further embodiment. [Figure 6E] Shows the sequence of operations of the system of the present disclosure in a further embodiment. [Figure 7] Shows a further embodiment of the reinjection system according to the present disclosure.
Mode for Carrying Out the Invention
[0016] According to the present disclosure, reinjection of spent geothermal fluid containing a liquid phase and non-condensable gas is facilitated by compressing the non-condensable gas in a reinjection well to form a column or pocket of pressurized non-condensable gas therein, and a column of pressurized liquid is pumped onto the pocket. Due to gravity, the column of pressurized liquid facilitates further compression of the non-condensable gas towards the bottom of the well in the reinjection well. A novel system for performing the above process is also disclosed. The system includes a gas-liquid separator and a plurality of containers, which are fluidly coupled to each other and to the gas-liquid separator through piping further including a pump unit. By selectively connecting the containers to the liquid outlet and gas outlet of the gas-liquid separator, the pump unit, and the well, the liquid and non-condensable gas can be delivered separately into the well in the form of a sequence of gas pockets and columns of liquid.
[0017] The novel reinjection system and method can be used in any facility where power is extracted from high-enthalpy geothermal fluid and spent liquid and non-condensable gas are to be reinjected into a reinjection well.
[0018] Referring here to the drawings, Figure 1 illustrates an exemplary and non-limiting geothermal plant in which the reinjection system and method of the present disclosure can be used. In the exemplary embodiment of Figure 1, the geothermal plant is a power plant that uses a thermodynamic cycle to convert the thermal energy contained in a pressurized, high-temperature geothermal fluid into mechanical force and electricity. Those skilled in the art will understand that it may also be advantageous to combine the same reinjection system and method with different types of geothermal plants, such as plants used for heating or other purposes. The methods and systems disclosed herein may be advantageous in situations where it is necessary to reinject non-condensable gases released by the geothermal fluid into a reinjection well to prevent or reduce the release of toxic or polluting gases, including greenhouse gases, into the environment.
[0019] The geothermal plant in Figure 1, shown as a whole by reference numeral 1, may include a thermodynamic cycle 3, a geothermal production well 5 from which high-temperature, pressurized geothermal fluid is extracted, and a geothermal reinjection well 7 from which spent geothermal fluid, including a liquid phase and a non-condensable gas phase (containing one or more non-condensable gases), can be reinjected. Reference numeral 9 indicates a system for reinjecting spent geothermal fluid, including liquid and non-condensable gases, into the reinjection well 7. System 9 will hereafter be referred to simply as the “reinjection system”. Embodiments of the reinjection system 9 and methods for operating it are disclosed in detail below with reference to Figures 2 to 7.
[0020] In the embodiment shown in Figure 1, thermodynamic cycle 3 includes a Rankine cycle. In some embodiments, thermodynamic cycle 3 can be an organic Rankine cycle (ORC) using an organic fluid such as carbon dioxide, ammonia, pentane, cyclopentane, or HFC (hydrofluorocarbon) refrigerant as the process fluid. In other embodiments, the thermodynamic cycle can be a Rankine cycle using vapor (water vapor) instead of an organic fluid as the process fluid.
[0021] The thermodynamic cycle can include a waste heat recovery system, with or without multiple pressure levels.
[0022] Thermodynamic cycle 3 comprises a heat exchanger section 11 which may include a preheater 11.1 and an evaporator 11.2. A pressurized process fluid flows through the low-temperature side of the preheater 11.1 and evaporator 11.2 and is heated and evaporated by heat exchange with a geothermal fluid from a geothermal production well 5 that flows through the high-temperature side of the evaporator 11.2 and preheater 11.1.
[0023] Thermodynamic cycle 3 further comprises a turbine 13, in which evaporated process fluid expands to generate mechanical power available in the turbine shaft 15. The turbine shaft 5 can be driven and coupled to a load such as a compressor or another rotating machine. In some embodiments, the load may include a generator 17, which converts the mechanical power into electricity, which is then delivered, for example, to a power distribution grid 19.
[0024] The spent process fluid from the turbine 13 is condensed in the condenser 20 and pumped by the pump 21 toward the preheater 11.1. The thermodynamic cycle may include a waste heat recovery unit 22 that can cool the spent process fluid from the turbine 13 toward the flow of condensed process fluid delivered by the pump 21.
[0025] The non-condensable gas may be dissolved in the geothermal liquid from the production well, or it may be contained in gaseous form in the steam or two-phase (liquid and steam) mixture from the production well 5. The non-condensable gas is separated from the liquid phase, for example, into a portion of the preheater 11.1, or directly into a dedicated separator, as will be described in more detail below, and then reinjected into the reinjection well 7 using system 9 as follows.
[0026] Figures 2A, 2B, and 2C show schematic diagrams of the reinjection system 9 at different steps of the reinjection process in one embodiment. The reinjection system 9 comprises a gas-liquid separator 31. As understood herein, the “gas-liquid separator” can be any part of the equipment in which an inlet flow containing liquid and non-condensable gases is divided into a liquid stream and a gas stream containing non-condensable gases such as carbon dioxide, methane, and other chemical species to be separated from the geothermal fluid produced by the production well 5. For example, the gas-liquid separator may include a heat exchanger, which also performs other functions and operations such as heat exchange to the process fluid of thermodynamic cycle 3 within the plant 1. As mentioned above, the gas-liquid separator can be, for example, part of a preheater 11.1.
[0027] The gas-liquid separator 31 includes an inlet 31.1, a liquid outlet 31.2, and a gas outlet 31.3.
[0028] The reinjection system 9 further comprises a plurality of vessels adapted to receive gas and liquid from the gas-liquid separator 31 in a specific sequence for the purpose of reinjecting liquid and non-condensable gas into the reinjection well 7. In the embodiment shown in Figure 2, the reinjection system 9 comprises first vessels 33 and 35. The two vessels 33 and 35 may be identical or different from each other; for example, the two vessels 33 and 35 may have the same capacity or different capacities.
[0029] The reinjection system 9 further comprises a pump unit 37. In some embodiments, the pump unit 37 may include a turbopump, for example, a centrifugal pump. The pump unit 37 includes a suction side 37.1 and a delivery side 37.2. The pump unit 37 is fluidly coupled to a gas-liquid separator 31, a first vessel 33, and a second vessel 35 through a piping system 39. Specifically, the suction side 37.1 of the pump unit 37 can be fluidly connected through the piping system 39 to the lower part of the gas-liquid separator 31, and more specifically, to its liquid outlet 31.2. For this purpose, the piping system 39 includes a first connection 39.1 having a control valve 39.2. The control valve 39.2 can be selectively opened and closed to selectively open and close the fluid connection between the liquid outlet 31.2 of the gas-liquid separator 31 and the suction side 37.1 of the pump unit 37.
[0030] The suction side 37.1 of the pump unit 37 can be selectively fluid-coupled to the lower side of the first container 33 and the lower side of the second container 35. In the schematic diagram of Figure 2, duct 39.3 extends from the lower side of the first container 33 to the suction side 37.1 of the pump unit 37, and duct 39.4 extends from the lower side of the second container 35 to the suction side 37.1 of the pump unit 37. Using a valve device, the suction side 37.1 of the pump unit 37 can be selectively fluid-coupled to the liquid outlet 31.2 of the gas-liquid separator 31, the lower side of the first container 33, and the lower side of the second container 35. The valve device includes, for example, a valve 39.2 and a further two-way or three-way valve. In the embodiment of Figure 2, the valve device includes a three-way valve 39.5.
[0031] The piping system 39 further comprises ducts adapted to selectively fluid-couple the delivery side 37.2 of the pump unit 37 to the first vessel 33 and the second vessel 35. Specifically, in the embodiment of Figure 2, duct 39.6 is provided for fluid-coupled the delivery side 37.2 of the pump unit 37 to the first vessel 33. Furthermore, duct 37.7 is provided for fluid-coupled the delivery side 37.2 of the pump unit 37 to the second vessel 35. Valve devices are further provided to selectively establish fluid connections between the delivery side 37.2 and the first vessel 33 and the second vessel 35. In the embodiments of Figures 2A, 2B, and 2C, the valve device includes a three-way valve 39.8.
[0032] In the embodiments of Figures 2A, 2B, and 2C, ducts 39.3 and 39.6 merge in a common port at the bottom or lower side of the first container 33, and ducts 39.4 and 39.7 merge in a common port at the bottom or lower side of the second container 35. In a different embodiment, ducts 39.6 and 39.3 may be connected to the first container 33 at different locations, for example, at an intermediate position between the top and bottom of the first container 33, and at the lower side or bottom of the first container 33. Similarly, in a different embodiment, ducts 39.7 and 39.4 may be connected to the second container 35 at different locations, for example, at an intermediate position between the top and bottom of the second container 35, and at the lower side or bottom of the second container 35.
[0033] The piping system 41 is provided at the top of the gas-liquid separator 31, the first vessel 33, and the second vessel 35. The piping system 41 includes a fluid connection 41.1 between the gas outlet 31.3 of the gas-liquid separator 31 and the first vessel 33 and the second vessel 35. Valve equipment, including, for example, a three-way valve 41.2, is provided along the fluid connection 41.1 and is adapted to connect the gas outlet 31.3 of the gas-liquid separator 31 to the first vessel 33 and the second vessel 35, respectively.
[0034] The piping system 41 further comprises fluid connections 41.3 adapted to selectively connect the tops or upper parts of the first vessel 33 and the second vessel 35 to the geothermal reinjection well 7 by fluid connections 41.4. A valve device, which may include a three-way valve 41.5, is combined with the fluid connections 41.3 to establish a fluid coupling between either the first vessel 33 or the second vessel 35 and the reinjection vessel 7 through the fluid connections 41.4.
[0035] Backflow prevention valves or check valves 45, 47 can be provided between the fluid connection 41.3 and the first container 33 and the second container 35.
[0036] The reinjection system 9 described above can be operated according to the sequential operation shown in Figures 2A, 2B, and 2C. In the various operating stages, ducts that are open and through which fluid is flowing are shown with solid lines, and closed ducts are shown with dashed lines.
[0037] In the first stage (Figure 2A), the suction side 37.1 of the pump unit 37 is fluid-coupled to the lower part of the first container 33 through a three-way valve 39.5 and a duct 39.3. The delivery side 37.2 of the pump unit 37 is fluid-coupled to the second container 35 through a three-way valve 39.8 and a duct 39.7. The gas outlet 31.3 of the gas-liquid separator 31 is fluid-coupled to the first container 33 through a duct 41.1 and a three-way valve 41.2.
[0038] The first container 33 contains liquid in its lower part and non-condensable gas in its upper part. The pump unit 37 pumps the liquid from the first container 33 to the second container 35, thereby increasing the liquid level in the second container 35. The non-condensable gas contained in the second container 35 is pressurized and forced into the fluid connection 41.4 through the duct 41.3 and the three-way valve 41.5, and from there into the reinjection well 7 (Figure 1). The delivery pressure of the non-condensable gas in the fluid connection 41.4 can be, for example, in the range of 15 to 20 barA.
[0039] As the liquid level in the first container 33 decreases, non-condensable gas is delivered into the first container 33 from the gas outlet 31.3 by suction.
[0040] At this stage, pockets or columns of non-condensable gas are formed within the reinjection well 7. The non-condensable gas is pressurized within the reinjection well by the pump unit 37, which processes the spent geothermal liquid and pumps it from the first container 33 to the second container 35. The volume reduction occupied by the non-condensable gas in the second container 35 is filled with liquid from the first container 33, and as a result, new non-condensable gas is drawn in from the gas-liquid separator 31.
[0041] Meanwhile, spent geothermal fluid containing the liquid phase and non-condensable gas is continuously supplied into the gas-liquid separator through the inlet 31.1, causing the liquid level inside the gas-liquid separator 31 to increase, while spent non-condensable gas flows out toward the first container 33 through the gas outlet 31.3.
[0042] At some point when the liquid level in the second container 35 has increased, and even before the second container 35 is filled with liquid, the operating state of the pump unit 37 is switched by switching the three-way valves 39.5 and 39.8, as shown in Figure 2B, and the second operating stage begins. In this stage, the liquid is pumped from the bottom of the second container 35 to the first container 33 through duct 39.4, three-way valve 39.5, pump unit 37, three-way valve 39.8, and duct 39.6.
[0043] The non-condensable gas collected in the first container 33 during the previous stage is pushed, for example, under a pressure of 20-30 barA, through the three-way valve 41.5 into the fluid connection 41.4 and from there into the reinjection well 7. The gas pocket in the reinjection well 7 continues to grow within the reinjection well 7 and permeates towards its bottom. The non-condensable gas is drawn into the second container 35 through the gas outlet 31.3, the duct 41.1 and the three-way valve 41.2.
[0044] Pumping of the liquid from the second container 35 into the first container 33 continues until the liquid level in the second container 35 reaches a low level. At this point, the system is switched to the state shown in Figure 2C. During the stage shown in Figure 2B, the liquid continues to be collected at the bottom of the gas-liquid separator 31, while the non-condensable gas flows into the second container 35 through the gas outlet 31.3.
[0045] In the stage shown in Figure 2C, the suction side 37.1 of the pump unit 37 is fluid-coupled to the liquid outlet 31.1 of the gas-liquid separator 31. The liquid is pumped from the liquid outlet 31.1 to the first container 33 and from there to the reinjection well 7. The liquid pressure in the first container 33 and therefore in the fluid connection 41.3 can be, for example, about 15-30 barA. During this stage, the second container 35 can be isolated.
[0046] During this stage, the liquid pumped into the reinjection well 7 forms a column of liquid, i.e., a column of liquid within the reinjection well 7. The pump pressure and the weight of the liquid column press down on the top of the previously formed gas pocket until the non-condensable gas dissolves in the liquid or is absorbed into the solid structure at the bottom of the reinjection well, and the top of the gas pocket is pushed further into the reinjection well.
[0047] When the liquid level in the gas-liquid separator 31 drops to the bottom of the gas-liquid separator 31, or when a sufficiently high column of liquid is formed in the reinjection container 7, the system 9 is switched back to the operating conditions shown in Figure 2A, and the cycle described above is repeated.
[0048] In some embodiments, the switching from the stage in Figure 2A to the stage in Figure 2B, the switching from the stage in Figure 2B to the stage in Figure 2C, and the switching back from the stage in Figure 2C to the stage in Figure 2A can be controlled by suitable level sensors. In the embodiments of Figures 2A, 2B, and 2C, a first level sensor 40 is associated with a first container 33, a second level sensor 42 is associated with a second container 35, and a third level sensor is associated with a gas-liquid separator 31. The level sensors 40, 42, and 44 can be adapted to detect a minimum level threshold of liquid in their respective containers or separators, and when this is detected, the system switches from one operating condition to another.
[0049] In some embodiments, when the first sensor 40 detects that the liquid level in the first container 33 has reached a minimum threshold, the system switches from the operating state shown in Figure 2A to the operating state shown in Figure 2B. In fact, in the state shown in Figure 2A, the liquid is pumped out of the first container 33, and therefore the liquid level inside it decreases. Pumping from the first container 33 is interrupted before the gas is drawn into the pump unit 37. In stage 2B, the liquid is pumped from the second container 35. When the second sensor 42 detects that the liquid level in the second container 35 has reached a minimum threshold, the suction of liquid from the second container 35 is interrupted. A signal from the second sensor 42 causes the system to switch from the operating state shown in Figure 2B to the operating state shown in Figure 2C. This third operating state continues until the third sensor 44 detects that the liquid level in the gas-liquid separator 31 has reached a minimum threshold.
[0050] In other embodiments, the level sensor can be omitted. The system switches from one operating state to the other when gas begins to enter the suction side of the pump unit 37. This can be detected indirectly, for example, by detecting a decrease in power absorbed by the motor driving the pump unit 37.
[0051] In a further embodiment, once the capacities (internal volumes) of the gas-liquid separator 31, the first container 33, and the second container 35 are known, switching can be performed based on time and flow rate measurements.
[0052] Figure 3 schematically illustrates what happens inside the reinjection vessel 7 during the operation cycle described above. The first liquid column LS1 formed in the previous step is shown at the bottom of the reinjection well 7. In the embodiment shown, the injection well has a depth of 3000m, but it should be understood that this value is merely an example and should not be construed as limiting the scope of this disclosure. The first liquid column LS1 is again shown, merely as an example, having a height of over 1000m. A gas pocket GP1 of non-condensable gas is formed on top of the first liquid column LS1. A second liquid column LS2 is formed on top of the gas pocket GP1. As an example, the pressure at the interface between the first liquid column LS1 and the gas pocket GP1 is approximately 110 barA, and the pressure at the interface between the second liquid column LS2 and the gas pocket GP1 is approximately 90 barA.
[0053] These pressure values are generated by the delivery pressure of the pump unit and by the weight of the liquid column formed in the reinjection well 7.
[0054] The high pressure achieved in the first liquid column LS1 dissolves non-condensable gases, and especially carbon dioxide (CO2), into the liquid, which then permeates the solid structure surrounding the reinjection well 7. In fact, as the liquid column and gas pocket move toward the bottom of the reinjection well 7, the pressure and mixing result in the formation of a single-phase flow when it reaches the geological formations surrounding the bottom of the reinjection well.
[0055] The efficient reinjection process for non-condensable gases in two-phase (liquid-gas) systems is achieved using centrifugal pumps (rather than reciprocating compressors).
[0056] The variable gas composition and variable gas / liquid ratio can be accommodated by preferred timings at different stages as disclosed above.
[0057] In some embodiments, the centrifugal pump of the pump unit 37 may be a variable-speed pump driven, for example, by a variable-speed electric motor. The rotational speed of the pump can be varied as a function of the delivery pressure to optimize pump efficiency. For example, the rotational speed of the centrifugal pump can be slowed down as the height of the liquid column increases.
[0058] Figure 4 illustrates a further embodiment of the reinjection system 9. The same reference numerals in Figures 2A, 2B, and 2C are used to indicate the same or equivalent components and will not be described again. The main difference between Figure 4 and Figures 2A, 2B, and 2C is the additional fluid coupling 51 that connects the tops of the first vessel 33 and the second vessel 35 to each other. The fluid coupling 51 is provided with a valve 52 for selectively connecting and disconnecting the two vessels 33, 35 to each other. The valve 52 and the fluid coupling 51 equalize the pressure in the two vessels during the stages shown in Figures 2A and 2B. In this configuration, rather than reducing the effective volume of the vessel drawing in new low-pressure gas, some of the energy of the compressed gas released by the liquid can be recovered and transferred to the vessel in the compression stage.
[0059] Continuing with the references to Figures 1-4, Figures 5A, 5B, 5C, and 5D illustrate different operating sequences of the reinjection system 9 described above. The structure of the reinjection system is the same as that shown in Figures 2A, 2B, and 2C and will not be described again. The same reference numbers refer to the same elements shown in Figures 2A, 2B, and 2C.
[0060] In Figure 5A, the pump unit 37 pumps the liquid from the first container 33 to the second container 35. Non-condensable gas is drawn into the first container 33 from the top of the gas-liquid separator 31, and non-condensable gas contained in the upper part of the second container 35 is pushed into the reinjection well, forming a gas pocket.
[0061] In the next stage (Figure 5B), the first container 33 is in a non-operating state, and the pump unit 37 pumps the liquid from the bottom of the gas-liquid separator 31 into the second container 35, and then pumps it from there into the re-injection well 7 to form a liquid column.
[0062] In Figure 5C, the operation of the pump unit 37 is switched back, and the liquid is pumped from the second container 35 into the first container 33 by the pump unit 37. Meanwhile, the non-condensable gas is pushed from the first container 33 into the reinjection well 7 and drawn into the second container 35 from the gas-liquid separator 31. In Figure 5D, the reinjection system 9 is once again in the operating state shown in Figure 5A.
[0063] Continuing with the references to Figures 1 through 5D, Figures 6A, 6B, 6C, 6D, and 6E illustrate different operating sequences of the reinjection system 9 described above. The structure of the reinjection system is the same as that shown in Figures 2A, 2B, and 2C and will not be described again. The same reference numbers refer to the same elements shown in Figures 2A, 2B, and 2C.
[0064] In Figure 6A, the pump unit 37 pumps the liquid from the first container 33 to the second container 35, thereby pushing the non-condensable gas from the second container 35 into the fluid connection 41.4 and from there into the reinjection well 7, forming a gas pocket.
[0065] In the next step (Figure 6B), the first container 33 is in a non-operating state and can be filled with non-condensable gas. The pump unit 37 draws liquid from the gas-liquid separator 31 and pumps that liquid through the second container 35 into the reinjection well 7.
[0066] In Figure 6C, the pump unit 37 is switched to a further operating mode, and liquid is drawn in from the bottom of the second container 35 and pumped into the first container 33. As a result, the pressurized non-condensable gas is pushed from the first container 33 into the reinjection well 7 through the fluid connection 41.4. The non-condensable gas is further drawn into the second container 35 from the top of the gas-liquid separator 31.
[0067] In the next step (Figure 6D), the second container 35 is inactive, and the pump unit 37 pumps the liquid from the bottom of the gas-liquid separator 31 through the first container 33 into the reinjection well 7, forming a column of liquid on top of the gas pocket previously formed inside.
[0068] Finally (Figure 6E), the reinjection system 9 is switched back to the operating mode shown in Figure 6A.
[0069] Continuing with the references to Figures 1 to 6E, Figure 7 shows a further embodiment of the reinjection system 9, in which the same reference numerals include the same or equivalent components already described in relation to Figures 2A, 2B, and 2C, and will not be described again.
[0070] In the embodiment shown in Figure 7, the reinjection system comprises three containers 33, 35, and 36. In alternative embodiments, a different number of containers may be used, for example, two containers as shown in Figures 2A to 6E, or even more than three parallel containers.
[0071] The delivery side 37.2 of the pump unit 37 is adapted to be selectively fluid-coupled to one or more of the parallel vessels 33, 35, and 36, and the connection between the delivery side 37.2 and one or more of the parallel vessels 33, 35, and 36 can be established by selectively opening and closing the respective valves 63, 65, and 67 through the line 61.
[0072] The suction side 37.1 of the pump unit 37 is also selectively connectable to one or more of the parallel-positioned vessels 33, 35, and 36, or to the gas-liquid separator 31. Valve 39.2 is positioned along the first connection 39.1 between the liquid outlet 31.2 and the suction side 37.1 of the pump unit 37, as described above. A connection line 69 is further provided, which connects the suction side 37.1 of the pump unit 37 to the three vessels 33, 35, and 36 through valves 71, 73, and 75, respectively. The connections between the suction side 37.1 of the pump unit 37 and one or more of the vessels 33, 35, and 37 and the gas-liquid separator 31 are selectively established by switching valves 39.2, 71, 73, and 75 as needed.
[0073] Non-condensable gases from each of the containers 33, 35, and 36 can be delivered into the reinjection well 7 through the check valves 45, 47, and 48 and the fluid connection 41.3, in exactly the same manner as shown in Figures 2A, 2B, and 2C. Non-condensable gases from the gas outlet 31.3 of the gas-liquid separator 31 can be selectively delivered to each of the containers 33, 35, and 37 through the fluid connection 41.1 and selectively activated valves 77, 79, and 81.
[0074] The reinjection system 9 in Figure 7 can operate substantially the same as the reinjection system described with reference to Figures 2A to 6E. By sequentially switching the operating modes of the pump unit 37 and using containers 33, 35, and 36 to collect non-condensable gas and liquid from the gas-liquid separator 31, gas pockets and liquid columns can be sequentially formed in the reinjection well 7.
[0075] In the exemplary embodiment described above, a single power plant is provided that is supported by a single reinjection system, while in other embodiments, multiple power plants can be supported by a single reinjection system, or vice versa, multiple reinjection systems can support one power plant.
[0076] Exemplary embodiments are disclosed above and illustrated in the accompanying drawings. Those skilled in the art will understand that various modifications, omissions, and additions can be made to what is specifically disclosed herein without departing from the scope of the invention as defined in the following claims.
Claims
1. A system for reinjecting spent geothermal liquid and non-condensable geothermal gas into a geothermal reinjection well, wherein the system A gas-liquid separator having an inlet, a gas outlet, and a liquid outlet, The first container and The second container, A pump unit having a suction side and a delivery side, The system includes a fluid connection to the aforementioned geothermal reinjection well, The suction side of the pump unit is adapted to be selectively fluid-coupled with the lower side of the gas-liquid separator, the lower side of the first container, and the lower side of the second container. The delivery side of the pump unit is adapted to be selectively fluid-coupled with the first container and the second container. The gas outlet of the gas-liquid separator is adapted to be selectively fluid-coupled to the upper side of the first container and the upper side of the second container. A system in which the fluid connection to the geothermal reinjection well is adapted to be selectively fluid-coupled to the upper side of the first vessel and the upper side of the second vessel.
2. The system according to claim 1, wherein the first container, the second container, and the pump unit are configured such that the first container and the second container are alternately filled and emptied by the pump unit through suitably controlled valves, and a variable volume above the liquid in the first container and the second container is used to draw in, compress, and send non-condensable gas from the gas-liquid separator into the geothermal reinjection well.
3. The system according to claim 1 or 2, wherein the pump unit comprises a dynamic pump such as a centrifugal pump.
4. The system according to claim 3, wherein the dynamic pump is a variable-speed dynamic pump.
5. The system according to any one of claims 1 to 4, further comprising a pressure equalization connection between the first container and the second container.
6. The system according to any one of claims 1 to 5, wherein the delivery side and suction side of the pump unit are connected to the lower side of the first container, to a suction control valve device on the suction side, and to a delivery control valve device on the delivery side of the pump unit, via a single duct.
7. The system according to claim 6, wherein the delivery side and suction side of the pump unit are connected to the lower side of the second container via a single duct to the suction control valve device on the suction side and to the delivery control valve device on the delivery side of the pump unit.
8. The system according to claim 6 or 7, wherein the suction control valve device comprises a three-way valve.
9. The system according to claim 6, 7, or 8, wherein the delivery control valve device comprises a three-way valve.
10. The system according to any one of claims 1 to 9, wherein the upper side of the first container and the upper side of the second container are connected to the fluid connection to the geothermal reinjection well via a three-way valve.
11. The system according to any one of claims 1 to 10, wherein the gas outlet of the gas-liquid separator is connected to the upper side of the first container and the upper side of the second container via a three-way valve.
12. It is a geothermal plant, Geothermal fluid intake and A unit adapted to extract heat from the geothermal fluid, A geothermal plant comprising the system described in any one of claims 1 to 11.
13. The geothermal plant according to claim 12, wherein the unit includes a thermodynamic cycle adapted to convert heat extracted from the geothermal fluid into mechanical power.
14. The geothermal plant according to claim 13, wherein the thermodynamic cycle comprises a turbomachinery and a generator that is drive-coupled to the turbomachinery and converts the mechanical power generated by the turbomachinery into electricity.
15. The aforementioned thermodynamic cycle, A thermodynamic closed circuit comprising: a heater adapted to circulate a process fluid and to heat the compressed process fluid; a power-generating turbomachinery adapted to expand the compressed and heated process fluid; a cooler adapted to cool the expanded process fluid; and a pump unit adapted to pressurize the cooled process fluid; A geothermal power plant according to claim 13 or 14, comprising a heat exchanger adapted to receive a flow of high-pressure and high-temperature geothermal fluid and to transfer heat from the geothermal fluid to the process fluid in the thermodynamic closed circuit.
16. A method for reinjecting geothermal liquids and non-condensable geothermal gases from an exhaust geothermal fluid flow into a geothermal reinjection well, wherein the method comprises the following steps: (i) A step of pumping a pressurized non-condensable gas pocket into the geothermal reinjection well, (ii) Pumping a column of pressurized liquid into the geothermal reinjection well over the pocket of pressurized noncondensable gas, A method comprising the step of repeating (iii)(i) and (ii).
17. The following steps: A step of delivering a flow of spent geothermal fluid containing a liquid phase and non-condensable gas into a gas-liquid separator having an inlet, a gas outlet, and a liquid outlet. A step in a pump system for supplying liquid separately from the liquid outlet of a gas-liquid separator and non-condensable gas separately from the gas outlet of a gas-liquid separator, wherein the pump system comprises at least a first container and a second container adapted to be selectively fluid-coupled with the gas-liquid separator and the geothermal reinjection well, and a pump unit for pumping the liquid from one of the first and second containers to the other of the first and second containers and into the geothermal reinjection well. The method according to claim 16, comprising the step of sequentially pumping the pressurized non-condensable gas pocket and the liquid column from the system into the geothermal reinjection well.
18. The step of sequentially delivering the pressurized non-condensable gas pocket and the liquid column from the system into the geothermal reinjection well is, The steps include: pumping the liquid from one of the gas-liquid separator, the first container, and the second container into the other of the first and second containers; and pushing the non-condensable gas from the other of the first and second containers into the geothermal reinjection well to form the pressurized non-condensable gas pocket in the geothermal reinjection well; The steps of pumping a liquid from the other of the first and second containers into the one of the first and second containers, and pushing a non-condensable gas from the one of the first and second containers into the geothermal reinjection well, The method according to claim 17, comprising the step of pumping a pressurized liquid from one of the first container and the second container into the geothermal reinjection well.
19. The following steps: (a) A step of delivering a flow of spent geothermal fluid containing liquid and non-condensable gas to a gas-liquid separator, wherein the gas-liquid separator has an inlet, a gas outlet, and a liquid outlet. (b) A step of delivering non-condensable gas from the gas outlet of the gas-liquid separator into the first container, simultaneously pumping the liquid from the first container into the second container, and pushing the non-condensable gas from the second container into the geothermal reinjection well to form a pressurized non-condensable gas pocket inside it. (c) A step of delivering non-condensable gas from the gas outlet of the gas-liquid separator into the second container, simultaneously pumping the liquid from the second container into the first container, and pushing the non-condensable gas from the first container into the geothermal reinjection well to form a pressurized non-condensable gas pocket inside it. (d) Pumping the liquid from the liquid outlet of the gas-liquid separator into the first container, into the second container, or into the first container and the second container, and from there into the geothermal reinjection well, thereby forming a column of liquid inside over the pressurized noncondensable gas pocket, The method according to claim 16, comprising the step of (e) repeating the sequence of steps (d) to (b).
20. The following steps: (a) A step of delivering a flow of spent geothermal fluid containing liquid and non-condensable gas into the gas-liquid separator, (b) The steps of delivering non-condensable gas from the gas outlet of the gas-liquid separator into the first container, simultaneously pumping the liquid from the first container into the second container, pushing the non-condensable gas from the second container into the geothermal reinjection well, and forming a pocket of non-condensable gas inside it, (c) Pumping the liquid from the gas-liquid separator into the second container, and pushing the liquid from the second container into the geothermal reinjection well to form a column of liquid inside the well over the pressurized non-condensable gas pocket, (d) The steps of delivering a non-condensable gas into the second container, pumping the liquid from the second container into the first container, and pushing the non-condensable gas from the second container into the geothermal reinjection well to form a pressurized non-condensable gas pocket inside it. The method according to claim 16, comprising the step of repeating steps (b) to (d).
21. The following steps: (a) A step of delivering a flow of spent geothermal fluid containing liquid and non-condensable gas into the gas-liquid separator, (b) A step of delivering non-condensable gas from the gas outlet of the gas-liquid separator into the first container, simultaneously pumping the liquid from the first container into the second container, and pushing the non-condensable gas from the second container into the geothermal reinjection well to form a pocket of non-condensable gas inside it. (c) Pumping the liquid from the gas-liquid separator into the second container, and pushing the liquid from the second container into the geothermal reinjection well, (d) drawing non-condensable gas into the second container, pumping the liquid from the second container into the first container, and pushing the non-condensable gas from the second container into the geothermal reinjection well, (e) Pumping the liquid from the gas-liquid separator into the first container, and pumping the liquid from the first container into the geothermal reinjection well to form a column of liquid inside thereof. The method according to claim 16, comprising the step of repeating steps (b) to (e).
22. A method for reinjecting geothermal liquids and non-condensable geothermal gases from an exhaust geothermal fluid flow into a geothermal reinjection well, wherein the method comprises the following steps: A step of delivering a flow of spent geothermal fluid containing a liquid phase and non-condensable gas into a gas-liquid separator, A step of selectively delivering a non-condensable gas from the gas outlet of the gas-liquid separator into at least a first container and a second container, Steps include pumping the liquid from the gas-liquid separator into at least one of the first container and the second container, A step of pumping the liquid from one of the first container and the second container into the other of the first container and the second container, A method comprising the step of sequentially delivering a pressurized non-condensable gas pocket and a liquid column from at least one of the first and second containers into the geothermal reinjection well.