Patent Application
20240287875
The present disclosure relates to methods and systems for recovering pressure energy from multiphase streams.
Pressure energy of multiphase streams, such as crude oil and gas, in strong flowing wells may be wasted in choke valves. Energy conversion turbines, for example, a turbo expander for recovering energy from gas streams or a power recovery turbine for recovering energy from liquid streams, may not be used directly on multiphase streams due to pressure fluctuation and stresses exerted on the turbine blades. An example of a multiphase stream is crude oil and gas mixtures produced from wells. Because of the dirty nature of some fluids, for example, crude oil and gas well fluids, turbo expanders may not be installed on multiphase streams or dirty liquid streams.
The present disclosure involves methods and systems for recovering pressure energy from multiphase streams. One example method includes separating a multiphase stream into a gas stream and a liquid stream. The separated gas stream is passed through a turbo expander. The separated liquid stream is passed through a multiphase ejector as a motive fluid. The separated gas stream in the turbo expander is sent from an outlet of the turbo expander to a low pressure nozzle of the multiphase ejector. Electricity is generated using a generator connected to the turbo expander.
Some or all of the aspects may be methods or further included in respective systems or other devices for performing this described functionality. The details of these and other aspects and implementations of the present disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims.
Like reference numbers and designations in the various drawings indicate like elements.
This specification relates to recovering pressure energy from multiphase streams. Instead of wasting the pressure energy from multiphase streams in choke valves, the energy can be utilized to generate electricity by running a gas turbo expander in combination with an ejector, for example, a multiphase ejector. As production fluids flow up the wellbore and to the remote manifold, some gas is evolved. In some implementations, a two-phase separator can separate a multiphase stream into a gas stream and a liquid stream. The separated liquid stream can flow through an ejector as a motive fluid and can create low pressure for the separated gas stream to flow and mix again with the liquid stream in the ejector. A turbo expander can be installed on the separated gas stream and can be connected to an electric generator to generate electricity using the energy recovered from the multiphase stream. This system of combined turbo expander and ejector can be used to recover pressure energy from both the separated gas and liquid streams which may have been lost through a throttling valve. An advantage of the system is to increase the energy recovery from both the separated gas and liquid streams. Another advantage of the system is to provide a source of green energy with reduced carbon footprint.
At 102, a multiphase stream is separated into a gas stream and a liquid stream. In some implementations, the multiphase stream, for example, a multiphase stream high pressure hydrocarbon mixture, is separated into liquid stream and gas stream in a two-phase separator. An example two-phase separator is two-phase separator 216 shown in
At 104, the separated gas stream is passed through a turbo expander. In some implementations, a turbo expander can be installed on the gas stream in order to lower gas stream pressure and thereby generating electricity. For oil and gas applications, pre-heater 218 can be used to preheat gas stream 214 and glycol injection 220 can be used to inject glycol into preheated gas stream from pre-heater 218, before the glycol-injected preheated gas stream flows through turbo expander 222. Pre-heater 218 and glycol injection 220 can be used to avoid the risk of condensation and hydrate formation, in order to have stable and reliable operation of turbo expander.
At 106, the separated liquid stream is passed through an ejector, for example, a multiphase ejector, as a motive fluid. In some implementations, the separated liquid stream can be used as a motive fluid in a multiphase ejector which creates low pressure on the low pressure nozzle of the multiphase ejector.
At 108, the separated gas stream in the turbo expander is connected to a low pressure nozzle of the multiphase ejector. This connection is shown between turbo expander 222 and ejector 228 in
At 110, electricity is generated using a generator connected to the turbo expander. As shown in
In some implementations, as shown in
In some implementations, if an energy delivery system, for example, a grid, cannot be made available, the generated energy can also be used to drive or supplement a multiphase pump to increase production from weaker wells.
In some implementations, gas turbo expanders can operate at an efficiency of 80-90% while multiphase ejectors are low efficiency devices and operate at efficiency of 25-35%.
A real oil and gas wellhead application can be selected and a computer program, for example, Aspentech Hysys® software, can be used to obtain liquid and gas properties and parameters for the design of a system that includes a turbo expander and a multiphase ejector, and in particular, the design of the ejector.
In some implementations, the computer program can calculate thermophysical properties of complex mixture of fluids using thermodynamic models. One example of these models is Peng-Robinson equation of state. It is not required to look up data tables to obtain properties of pure components and use empirical correlations to estimate properties of mixtures. It can also predict phase equilibria to estimate volumes of gases and liquids in equilibrium at contained conditions of temperature and pressures.
In some implementations, these thermophysical properties can be used in sizing ejectors and turbo expanders. Actual volumetric flows and velocities inside nozzles can be predicted using these thermophysical properties and therefore, low pressure generated due to high velocities inside the ejector can be estimated. Prediction of choked flow is also an important factor in ejector design. Calculation of enthalpies at inlet and outlet of these ejectors and turbo expanders can determine the energy recovered.
In some implementations, the suction pressure of a multiphase ejector can be calculated in order to determine the incremental power generation due to the addition of the multiphase ejector.
Representative operating parameters can include (1) inlet temperature of 183.3 F, (2) inlet pressure of 820.6 psig, and (3) ejector outlet pressure of 135.3 psig.
Representative volumetric flow of all phases can include (1) water flowrate of 5695 bbl/day, (2) oil flowrate of 5523 bbl/day, and (3) gas flow of 3.53 mmscfd at standard conditions.
Representative properties of all phases, at flowing conditions, can include (1) water density of 60.15 1b/ft3, (2) oil density of 46.6 1b/ft3, (3) oil viscosity of 0.8227 cP, (4) gas molecular weight of 25.01, (5) gas Cp/Cv of 1.291, and (6) gas heat capacity of 1.291 BTU/lboF.
Based on these parameters and a design of multiphase ejector, the suction pressure of ejector (outlet of turbo expander) can be determined to be 85.3 psig. The calculated power recovery based on 85% overall efficiency of turbo expander, was 271.6 HP. This includes 46.1 HP additional power generated due to the inclusion of the ejector in the design. This additional power is generated by reduction of discharge pressure of turbo expander from 135.3 psig to 85.3 psig due to the inclusion of the ejector which recovers a part of energy from liquid stream.
In some implementations, varying the gas to liquid ratio (GLR) can have an impact on the total power generated. Increasing the GLR can increase the total power generated due to the increase in gas flowrate. Decreasing the GLR can decrease the total power generated due to the decrease in gas flowrate. The generated power might increase despite of decreasing the GLR due to the decrease in pressure, on low pressure nozzle of the ejector, due to the increase in liquid flowrate. The generated power can decrease, with decreasing GLR, once the decrease in gas flow has more impact on the power generated.
In some implementations, turbo expanders used for sour service can be used to handle condensed liquids at the discharge. These turbo expanders can be equipped with magnetic bearings to avoid bearing oil contamination.
Certain aspects of the subject matter described here can be implemented as a method. A multiphase stream is separated into a gas stream and a liquid stream. The separated gas stream is passed through a turbo expander. The separated liquid stream is passed through a multiphase ejector as a motive fluid. The separated gas stream in the turbo expander is sent from an outlet of the turbo expander to a low pressure nozzle of the multiphase ejector. Electricity is generated using a generator connected to the turbo expander.
Methods can include one or more of the following features.
In some implementations, after the separated gas stream in the turbo expander is sent from the outlet of the turbo expander to the low pressure nozzle of the multiphase ejector and before electricity is generated using the generator connected to the turbo expander, the separated gas stream from the outlet of the turbo expander and the separated liquid stream in the multiphase ejector are mixed in the multiphase ejector.
In some implementations, after the multiphase stream is separated into the gas stream and the liquid stream and before the separated gas stream is passed through the turbo expander, glycol is injected into the separated gas stream.
In some implementations, after the multiphase stream is separated into the gas stream and the liquid stream and before the glycol is injected into the separated gas stream, the separated gas stream is preheated.
In some implementations, after separating the multiphase stream is separated into the gas stream and the liquid stream and before the separated gas stream is passed through the turbo expander, the separated gas stream is passed through a knock-out drum.
In some implementations, a level of the separated gas stream in the knock-out drum is controlled using a level controller.
In some implementations, a multiphase pump is driven using the generated electricity. In some implementations, the multiphase stream is crude oil from one or more wells.
In some implementations, an efficiency of the turbo expander is between 80 and 90 percent.
In some implementations, an efficiency of the multiphase ejector is between 25 and 35 percent.
Certain aspects of the subject matter described here can be implemented as a system. The system includes a two-phase separator, a turbo expander, and a multiphase ejector. An outlet of the turbo expander is coupled to a low pressure nozzle of the multiphase ejector. The two-phase separator is coupled to the turbo expander and the multiphase ejector and is configured to separate a multiphase stream into a gas stream and a liquid stream. The turbo expander is configured to pass the separated gas stream from the two-phase separator through the turbo expander and send the separated gas stream in the turbo expander from the outlet of the turbo expander to the low pressure nozzle of the multiphase ejector. The multiphase ejector is configured to pass the separated liquid stream from the two-phase separator through the multiphase ejector as a motive fluid and mix, in the multiphase ejector, the separated gas stream from the outlet of the turbo expander and the separated liquid stream in the multiphase ejector.
Systems can include one or more of the following features.
In some implementations, the system further includes a generator coupled to the turbo expander, and the generator is configured to generate electricity using energy from the separated gas stream in the turbo expander.
In some implementations, the generator is further configured to drive a multiphase pump using the generated electricity from the generator.
In some implementations, the system further includes a knock-out drum coupled to the two-phase separator, and the knock-out drum is configured to pass the separated gas stream from the two-phase separator through the knock-out drum.
In some implementations, the system further includes a level controller, and the level controller is configured to controlling a level of the separated gas stream in the knock-out drum.
In some implementations, the system further includes a pre-heater coupled to the knock-out drum, the pre-heater is configured to preheat the separated gas stream from the knock-out drum, and preheating the separated gas stream from the two-phase separator includes preheating the separated gas stream from the knock-out drum.
In some implementations, the system further includes a glycol injection device coupled to the pre-heater and the turbo expander, the glycol injection device is configured to inject glycol into the preheated gas stream from the pre-heater, and passing the separated gas stream from the two-phase separator through the turbo expander includes passing the glycol-injected preheated gas stream from the glycol injection device through the turbo expander.
In some implementations, the multiphase stream is crude oil from a well.
In some implementations, the system is positioned at a remote manifold location separated from a location of the well.
In some implementations, an efficiency of the turbo expander is between 80 and 90 percent, and wherein an efficiency of the multiphase ejector is between 25 and 35 percent.
While this specification contains many specific implementation details, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features that may be specific to particular implementations. Certain features that are described in this specification in the context of separate implementations can also be implemented, in combination, in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations, separately, or in any sub-combination. Moreover, although previously described features may be described as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can, in some cases, be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.
As used in this disclosure, the terms “a,” “an,” or “the” are used to include one or more than one unless the context clearly dictates otherwise. The term “or” is used to refer to a nonexclusive “or” unless otherwise indicated. The statement “at least one of A and B” has the same meaning as “A, B, or A and B.” In addition, it is to be understood that the phraseology or terminology employed in this disclosure, and not otherwise defined, is for the purpose of description only and not of limitation. Any use of section headings is intended to aid reading of the document and is not to be interpreted as limiting; information that is relevant to a section heading may occur within or outside of that particular section.
As used in this disclosure, the term “about” or “approximately” can allow for a degree of variability in a value or range, for example, within 10%, within 5%, or within 1% of a stated value or of a stated limit of a range.
As used in this disclosure, the term “substantially” refers to a majority of, or mostly, as in at least about 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, or at least about 99.999% or more.
Values expressed in a range format should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a range of “0.1% to about 5%” or “0.1% to 5%” should be interpreted to include about 0.1% to about 5%, as well as the individual values (for example, 1%, 2%, 3%, and 4%) and the sub-ranges (for example, 0.1% to 0.5%, 1.1% to 2.2%, 3.3% to 4.4%) within the indicated range. The statement “X to Y” has the same meaning as “about X to about Y,” unless indicated otherwise. Likewise, the statement “X, Y, or Z” has the same meaning as “about X, about Y, or about Z,” unless indicated otherwise.
Particular implementations of the subject matter have been described. Other implementations, alterations, and permutations of the described implementations are within the scope of the following claims as will be apparent to those skilled in the art. While operations are depicted in the drawings or claims in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed (some operations may be considered optional), to achieve desirable results. In certain circumstances, multitasking or parallel processing (or a combination of multitasking and parallel processing) may be advantageous and performed as deemed appropriate.
Moreover, the separation or integration of various system modules and components in the previously described implementations should not be understood as requiring such separation or integration in all implementations, and it should be understood that the described components and systems can generally be integrated together or packaged into multiple products.
Accordingly, the previously described example implementations do not define or constrain the present disclosure. Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of the present disclosure.
