Self-calibration for multiphase flow meters
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- CHEVRON USA INC
- Filing Date
- 2025-11-22
- Publication Date
- 2026-06-04
Smart Images
Figure US2025056768_04062026_PF_FP_ABST
Abstract
Description
SELF-CALIBRATION FOR MULTIPHASE FLOW METERSFIELD OF THE INVENTION
[0001] The present disclosure is directed generally to multiphase flow meter (MPFM) systems and, more particularly, to techniques for measuring fluid properties to self-calibrate MPFMs.BACKGROUND
[0002] This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and / or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
[0003] Multiphase flow meters (MPFMs) measure gas, oil, and water flow rates in pipes. An MPFM is a device installed in a pipe carrying a stream of three-phase fluid (having unseparated gas, oil, and water), typically flowing from a well. MPFMs generally include several sensing elements, which can be used to measure how much of each one of the three phases is flowing through the MPFM. Some designs use a combination of differential pressure sensor(s) (e.g., a Venturi flow meter) and fluid density sensor(s) (e.g., Gamma-spectrometer and / or permittivity sensor) to measure total flow rate and fluid mixture phase fractions. Nucleonic fraction metering can be based on Gamma ray attenuation, measuring mass fractions of phases when the fluid mixture passes through the Venturi throat. Readings from these different sensors are combined into a flow computer of the MPFM.
[0004] The MPFM flow computer uses algorithms developed by the device manufacturer to calculate flow rates of oil, gas, and water based on the sensor readings of the MPFM. The flow computer requires certain parameters (importantly, fluid properties of gas, oil, and water phases) as inputs to calibrate the algorithms, so that the flow computer can provide accurate flow rate calculations. For example, gas, oil, and water phase properties such as density can be used to convert mass flow rates of each phase to volumetric flow rates at line (i.e., operating) and standard conditions. Fluid properties, such as density (particularly of gas and oil) can change considerably over time. As such, the phase properties and their relationship to operating conditions (e.g., temperature and pressure) are input to the MPFM. These fluidproperties of the different phases are modeled to generate lookup tables of the fluid properties with respect to operating conditions, and the lookup table is then input to the MPFM flow computer for calibrating the MPFM.
[0005] It is now recognized that a need exists for systems and methods to measure fluid properties of three-phase fluid at operating conditions in a time efficient manner to generate lookup tables for an MPFM.SUMMARY
[0006] A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below.
[0007] In accordance with aspects of the disclosure, a method for measuring fluid properties of different phases in a three-phase fluid flowing at line conditions includes: directing the three- phase fluid at a full flow rate through a multiphase flow meter (MPFM) section, the MPFM section having an MPFM located along a vertical pipe section; halting the flow of three-phase fluid through the MPFM section to trap the three-phase fluid in the MPFM section; allowing the three-phase fluid trapped in the MPFM section to separate into a gas portion, an oil portion, and a water portion in the vertical pipe section; measuring a fluid property of the gas portion via a sensor in the MPFM; directing additional three-phase fluid through the MPFM section at a reduced flow rate less than the full flow rate such that the gas portion, oil portion, and water portion each move upward within the vertical pipe section; halting the reduced flow of three- phase fluid through the MPFM section after a gas / oil interface passes a sensing location in the MPFM; and measuring the fluid property of the oil portion via the sensor in the MPFM.
[0008] In accordance with other aspects of the disclosure, a system includes: a vertical pipe section; a multiphase flow meter (MPFM) located along the vertical pipe section; an inlet horizontal pipe section coupled to a lower end of the vertical pipe section; an outlet horizontal pipe section coupled to an upper end of the vertical pipe section; an inlet valve disposed along the inlet horizontal pipe section; an outlet valve disposed along the outlet horizontal pipe section; a first bypass flowline connecting the inlet horizontal pipe section on an upstream side of the inlet valve to the inlet horizontal pipe section on a downstream side of the inlet valve; a second bypass flowline connecting the outlet horizontal pipe section on an upstream side of the outlet valve to the outlet horizontal pipe section on a downstream side of the outlet valve; afirst bypass valve disposed along the first bypass flowline, the first bypass valve having a flow area smaller than the inlet valve; and a second bypass valve disposed along the second bypass flowline, the second bypass valve having a flow area smaller than the outlet valve.BRIEF DESCRIPTION OF DRAWINGS
[0009] The drawings illustrate only example embodiments and are therefore not to be considered limiting in scope, as the example embodiments may admit to other equally effective embodiments. The elements and features shown in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the example embodiments. Additionally, certain dimensions or positions may be exaggerated to help visually convey such principles. In the drawings, reference numerals designate like or corresponding, but not necessarily identical, elements.
[0010] FIG. l is a front view of a multiphase flow meter (MPFM) system, in accordance with one or more aspects of the present disclosure.
[0011] FIG. 2 is a front view of another MPFM system, in accordance with one or more aspects of the present disclosure.
[0012] FIG. 3 is a process flow diagram illustrating a method for measuring fluid properties of different phases in a three-phase fluid flowing at line conditions, in accordance with one or more aspects of the present disclosure.
[0013] FIG. 4 is a schematic diagram illustrating a basis of design in a fluid flow simulation, in accordance with one or more aspects of the present disclosure.
[0014] FIG. 5 is a plot illustrating steady state liquid hold-up profiles in a simulated MPFM section, in accordance with one or more aspects of the present disclosure.
[0015] FIG. 6 is a plot illustrating liquid hold-up profiles in the MPFM section during shut-in, in accordance with one or more aspects of the present disclosure.
[0016] FIG. 7 is a plot illustrating water accumulation in the MPFM section over time during liquid accumulation within the MPFM section, in accordance with one or more aspects of the present disclosure.
[0017] FIG. 8 is a plot illustrating shut-in liquid hold-up profiles in the MPFM section after the liquid accumulation of FIG. 7, in accordance with one or more aspects of the present disclosure.DETAILED DESCRIPTION OF THE INVENTION
[0018] The present disclosure is directed to systems and methods for measuring fluid properties of three-phase fluid at operating conditions for the self-calibration of multiphase flow meters (MPFMs).
[0019] Fluid properties of different phases (gas, oil, and water) of a three-phase fluid are measured for modeling purposes to generate lookup table(s) of the fluid properties with respect to operating conditions (different temperatures and pressures). These lookup tables are then input into a flow computer of a MPFM to calibrate the algorithms used by the MPFM to provide three-phase flow metering. The fluid properties may include, for example, a fluid density.
[0020] Conventionally, the fluid properties are measured in a pressure-volume-temperature (PVT) laboratory using samples that were previously collected in the field (e.g., downhole samples and / or separator samples). Later, lookup tables are generated from the phase-specific fluid property measurements and loaded into the MPFM flow computer. Unfortunately, the fluid property of phases (gas, oil, and water) passing through the MPFM may not be readily available, particularly when using the MPFM for exploration / appraisal well testing. In this case, some nominal values (i.e., from an analogue well) for phase properties may be used. Then, once fluid samples collected in the field are analyzed in the PVT laboratory, the fluid properties of phases are updated in the MPFM flow computer. This sampling / analysis process can take several months, particularly if the samples are shipped out of the country for analysis. Furthermore, as a reservoir is put on production, produced fluid properties (mainly gas and oil) can change with pressure depletion. This means the fluid properties in the MPFM should be updated to reduce errors in the flow metering of the MPFM. Another round of fluid sampling and analysis is then performed to re-measure the fluid properties and update the MPFM fluid model. It is now recognized that the amount of time involved in conventional MPFM calibration processes is undesirable, as it can reduce the accuracy of the MPFM measurements for extended periods of time while waiting for PVT laboratory results.
[0021] The disclosed methods and systems overcome the deficiencies associated with conventional MPFM calibration. The disclosed methods and systems enable the measurement of fluid properties of individual phases at line (operating) conditions using the MPFM in the field. This eliminates the need for sample collection and transportation to a remote laboratory for fluid property measurements. Such capabilities may allow for self-calibration of the MPFM.
[0022] The disclosed systems include an MPFM skid with a configuration of valves that enables different phases to fill the MPFM at different times. This allows fluid properties (e.g., density) of each phase to be measured at line conditions using a sensor in the MPFM.
[0023] The use of the terms "about", “approximately”, and similar terms applies to all numeric values, whether or not explicitly indicated. These terms generally refer to a range of numbers that one of ordinary skill in the art would consider as a reasonable amount of deviation to the recited numeric values (i.e., having the equivalent function or result). For example, this term may be construed as including a deviation of ±10 percent of the given numeric value provided such a deviation does not alter the end function or result of the value. Therefore, a value of about 1% may be construed to be a range from 0.9% to 1.1%. Furthermore, a range may be construed to include the start and the end of the range. For example, a range of 10% to 20% (i.e., range of 10%-20%) includes 10% and also includes 20%, and includes percentages in between 10% and 20%, unless explicitly stated otherwise herein. Similarly, a range of between 10% and 20% (i.e., range between 10% - 20%) includes 10% and also includes 20%, and includes percentages in between 10% and 20%, unless explicitly stated otherwise herein.
[0024] Turning now to the drawings, FIG. 1 illustrates an example MPFM system 100. The MPFM system 100 includes a skid 102 supporting multiple pipe sections and valves used to selectively divert three-phase fluid flow into an MPFM section 103 and / or bypass the MPFM section 103. The MPFM section 103 may be located along a flow path coupling a well (e.g., oil and / or gas production well) to a separator (e.g., production separator) used to separate the three-phase fluid into its constituent parts.
[0025] As illustrated, the MPFM system 100 may include a vertical pipe section 104, an MPFM 106 located along the vertical pipe section 104, an inlet horizontal pipe section 108 coupled to a lower end of the vertical pipe section 104, and an outlet horizontal pipe section 110 coupled to an upper end of the vertical pipe section 104. The inlet horizontal pipe section 108 may couple the MPFM system 100 to a well upstream of the MPFM system 100, and the outlet horizontal pipe section 110 may couple the MPFM system 100 to a separator downstream of the MPFM system 100. An inlet valve 112 is disposed along the inlet horizontal pipe section 108, and an outlet valve 114 is disposed along the outlet horizontal pipe section 110. In addition, the MPFM system 100 may include a bypass pipe section 116 with a bypass valve 118 disposed thereon. The bypass pipe section 116 connects the inlet horizontal pipe section 108 at a position upstream of the inlet valve 112 to the outlet horizontal pipe section 110 at a position downstream of the outlet valve 114.
[0026] As shown, the MPFM section 103 includes the vertical pipe section 104 with the MPFM 106, the inlet valve 112 and the inlet horizontal pipe section 108 downstream of the inlet valve 112, and the outlet valve 114 and the outlet horizontal pipe section 110 upstream of the outlet valve 114. The inlet valve 112 may control the flow of three-phase fluid into the MPFM section 103, and the outlet valve 114 may control the flow of three-phase fluid out of the MPFM section 103. For example, when valve 118 is closed and both the inlet valve 112 and the outlet valve 114 are opened, either fully or partially, three-phase fluid is able to flow through the MPFM section 103 (e.g., from the inlet horizontal pipe section 108 to the vertical pipe section 104 to the outlet horizontal pipe section 110). When both the inlet valve 112 and the outlet valve 114 are closed, a portion of three-phase fluid is held within the MPFM section 103. The vertical pipe section 104 may be used to isolate the three phases of fluid when the fluid is held within the MPFM section 103. When both the inlet valve 112 and the outlet valve 114 are closed, the bypass valve 118 may be opened (e.g., fully opened) to enable three-phase fluid to continue flowing from the upstream portion of the inlet horizontal pipe section 108 to the downstream portion of the outlet horizontal pipe section 110.
[0027] It should be noted that FIG. 1 is an example, and other numbers, shapes, sizes, and relative arrangements of the horizontal and vertical pipe sections and valves may be used in other embodiments without departing from the scope of the present disclosure. Any desired pipe diameter may be used for the different pipe sections, and any desired pipe length may be used for the different pipe sections.
[0028] The MPFM 106 may include a flow meter (not shown) and a flow computer (not shown) used to perform calculations on measurements taken by the flow meter to determine gas, oil, and water volume flow rates (e.g., mass flow, velocity, volume flow) of the fluid passing through the MPFM 106. The volume flow rates for each phase are determined through built- in algorithms in the flow computer using measured phase fractions / velocities.
[0029] The MPFM 106 may also include at least one sensor 120 (or group of sensors) configured to measure one or more fluid properties (e.g., density, conductivity, capacitance, salinity, permittivity, nuclear magnetic resonance, dynamic pressure, etc.) of the three-phase fluid in the MPFM section 103. The at least one sensor 120 may include, for example, a permittivity sensor, a Gamma-spectroscopy sensor, an electrical sensor (e.g., impedance sensor, capacitance sensor), an optical sensor, an acoustic sensor, or a combination thereof to detect one or more fluid properties of the three-phase fluid. The sensor(s) 120 of the MPFM 106 may be aligned with a sensing window 122 within the vertical pipe section 104. For example, this sensing window 122 may be a portion of the vertical pipe section 104immediately upstream of the throat of a Venturi flow meter in the MPFM 106. For the sensor(s) 120 of the MPFM 106 to capture fluid properties of a particular phase of the three-phase fluid, the desired phase of the fluid has to cover the sensing window 122. The sensor(s) 120 can measure one or more fluid properties of any particular phase of the fluid as long as the phase is stagnant within this sensing window 122. The design of the MPFM system 100 allows for the positioning of individual fluid phases within the sensing window 122 at different times for the in-line measurement of fluid properties (e.g., density) of the gas, oil, and water phases of the three-phase fluid.
[0030] The MPFM 106 and / or the MPFM section 103 may further include additional sensors (not shown), such as those for measuring a static pressure (e.g. a differential pressure sensor) and / or static temperature of the three-phase fluid in the MPFM 106. These sensor measurements may be provided to the flow computer where they are input to algorithms to determine volume flow rates of gas, oil, and water.
[0031] As illustrated, the inlet valve 112 and the outlet valve 114 may be the same size. This enables a pressure-balanced flow of three-phase fluid through the MPFM section 103 when the valves 112 and 114 are fully opened. The bypass valve 118 may also be the same size as the inlet and outlet valves 112 and 114. The valves 112 and 114 may be ball valves, although other types of valves could be used in other embodiments. The bypass valve 118 may be the same or a different type of valve as the inlet and outlet valves 112 and 114. In the MPFM system lOO ofFIG. 1, the inlet valve 112 and the outlet valve 114 may each be configured to be variably opened. This enables the inlet and outlet valves 112 and 114 to act as control valves that can change the flow rate of three-phase fluid into and out of the MPFM section 103.
[0032] In some embodiments, the MPFM system 100 may also include a selectively openable drain 124 coupled to the inlet horizontal pipe section 108 on the downstream side of the inlet valve 112. Opening this drain 124 may help to adjust a vertical position of an oil / water interface of the three-phase fluid in the vertical pipe section 104.
[0033] Certain functions of the MPFM system 100 will now be described. To bypass the MPFM section 103, the inlet valve 112 and outlet valve 114 may both be closed and the bypass valve 118 may be opened. This represents a normal operating condition of the MPFM system 100. To divert the three-phase fluid (gas, oil, and water) to the MPFM section 103, valves 112 and 114 can be opened while bypass valve 118 is closed. The inlet valve 112 and the outlet valve 114 may both be fully opened to direct the three-phase fluid at a full flow rate through the MPFM section 103. In this position, the MPFM 106 can measure the flow rates of the three phases (gas, oil, water) while the fluid flows through the MPFM section 103. While the three-phase fluid is flowing through the MPFM section 103, three-phase fluid fills the vertical pipe section 104 and the parts of the horizontal pipe sections 108 and 110 between the inlet and outlet valves 112 and 114.
[0034] Once the full flow of three-phase fluid is moving through the MPFM section 103, the inlet and outlet valves 112 and 114 may be closed and the bypass valve 118 opened to stop the three-phase fluid from moving through the MPFM section 103. Upon closing the inlet and outlet valves 112 and 114 and opening the bypass valve 118 (normal operating conditions), three-phase fluid at line conditions is trapped in the MPFM section 103 of the system 100 (between valves 112 and 114). The three-phase fluid that is left in the vertical pipe section 104 will then separate in the vertical direction (due to gravity), separating into gas on top, oil in the middle, and water at the bottom. Due to this gravity segregation, the top of the MPFM section 103 (e.g., the outlet horizontal pipe section 110 upstream of the outlet valve 114 and the vertical pipe section 104) may fill with gas, whereas liquid (oil and water) slumps to the bottom part of the MPFM section 103 (e.g., the inlet horizontal pipe section 108 downstream of the inlet valve 112). If gas has already filled the MPFM 106, the MPFM 106 can measure the fluid property (e.g., density) of the gas phase at line conditions via the sensor(s) 120. In some embodiments, e.g., at low gas volume fraction, some liquid may need to be drained from the MPFM section 103 for the gas to fill the MPFM 106, at which point the MPFM 106 can then measure the fluid property of the gas phase via sensor(s) 120.
[0035] To measure the density of the oil phase, an operator may partially open the inlet valve 112 and partially open the outlet valve 114 to direct additional three-phase fluid through the MPFM section 103 at a reduced flow rate (i.e., less than the full flow rate). For example, the inlet and outlet valves 114 may be cracked open (e.g., 5% opening, 1 wheel turn, etc.) to let the additional three-phase fluid move into the MPFM section 103. The inlet and outlet valves 112 and 114 may be partially opened by the same or substantially the same amount. The partially opened inlet valve 112 allows additional fluid (particularly the liquid portions of the three- phase fluid) to enter the MPFM section 103. The partially opened outlet valve 114 allows balancing of the pressure in the MPFM section 103 (so that the MPFM section 103 remains at line conditions) via movement of gas through the outlet valve 114. At this stage, the bypass valve 118 may remain fully open. The inlet and outlet valves 112 and 114 may be opened less than 10%, or less than 5%, or less than 2% at this stage.
[0036] Partially opening the inlet and outlet valves 112 and 114 in this manner allows for a small amount of the fluid stream (primarily liquid) to be fed into the vertical pipe section 104, thereby pushing the gas, oil, and water phases further up the vertical pipe section 104. Oncethe three-phase flow enters the MPFM section 103, due to gravity segregation, the gas phase travels to the top of the MPFM section 103 while liquid (oil and water) accumulates at the bottom of the MPFM section 103. After a certain time (e.g., 1 hour), the gas / oil interface of the three-phase fluid passes through the MPFM 106 such that the sensing window 122 is filled with oil at line conditions. As described in greater detail below, opening a drain 124 may be used to further adjust the vertical position of the gas / oil and oil / water interfaces. Gas, oil, and water have different fluid property (e.g., density) ranges. As such, it is possible to tell, based on the measurement(s) of the sensor(s) 120, which phase is currently located in the sensing window 122. Taking continuous measurements of the fluid property via the MPFM 106 during the upward movement of the gas, oil, and water portions of the three-phase fluid through the vertical pipe section 104, and displaying the continuous measurements on a user interface, enables an operator to see when the fluid property (and thus the fluid in the sensing window 122) switches from the gas phase to the oil phase.
[0037] After the gas / oil interface passes the MPFM 106, a little more additional three-phase fluid may be directed through the MPFM section 103, and additional sensor measurements taken, to confirm that the oil phase is now within the sensing window 122. At this point, both inlet and outlet valves 112 and 114 may be closed. After a period, the gas, oil, and water phases will fully separate in the vertical pipe section 104. Then, the sensor(s) 120 of the MPFM 106 can measure the fluid property of the oil phase at line conditions.
[0038] In some wells, the volume of oil is much smaller than the volume of water. As such, it may be difficult to precisely place the oil phase within the sensing window 122 using only the inlet and outlet valves 112 and 114. An approach to manage the oil / water interface can be to periodically drain water off the bottom of the MPFM section 103, enabling additional oil to accumulate within the vertical pipe section 104. The drain 124 may be selectively opened and closed to fine tune the positioning of the oil / water interface so that the oil phase is stagnant within the sensing window 122 for fluid property measurements.
[0039] The process can then be repeated to move the oil / water interface until it passes the MPFM 106 and fills the sensing window 122 with water for the fluid property measurement. For example, to measure a fluid property of the water phase, an operator may partially open the inlet valve 112 and partially open the outlet valve 114 to direct additional three-phase fluid through the MPFM section 103 at a reduced flow rate (i.e., less than the full flow rate). The partial opening of the valves 112 and 114 and resulting reduced flow rate may be the same as or different than what was used to position the oil phase in the sensing window 122. The inlet and outlet valves 112 and 114 may be partially opened by the same or substantially the sameamount. Again, the bypass valve 118 may remain fully open. The inlet and outlet valves 112 and 114 may be opened less than 10%, or less than 5%, or less than 2% at this stage.
[0040] Partially opening the inlet and outlet valves 112 and 114 pushes the gas, oil, and water phases further up the vertical pipe section 104. After a certain time (e.g., 1 hour, depending on the opening of the valves), the oil / water interface of the three-phase fluid passes through the MPFM 106 such that the sensing window 122 is filled with water at line conditions. Taking continuous measurements of the fluid property via the MPFM 106 during the upward movement of the gas, oil, and water portions of the three-phase fluid, and displaying the continuous measurements on a user interface, enables an operator to see when the fluid property measurement switches from the oil phase to the water phase.
[0041] After the oil / water interface passes the MPFM 106, a little more fluid may be directed through the MPFM section 103, and additional sensor measurements taken, to confirm that the water phase is now within the sensing window 122. At this point, both inlet and outlet valves 112 and 114 may be closed. After a period, the gas, oil, and water phases will fully separate in the vertical pipe section 104. Then, the sensor(s) 120 of the MPFM 106 can measure the fluid property of the water phase at line conditions.
[0042] FIG. 2 illustrates another example MPFM system 200. The MPFM system 200 includes the skid 102, the MPFM section 103, the vertical pipe section 104, the MPFM 106, the inlet horizontal pipe section 108, the outlet horizontal pipe section 110, the inlet valve 112, the outlet valve 114, the bypass pipe section 116, the bypass valve 118, the sensor(s) 120, and the sensor window 122 as described at length above with reference to FIG. 1. These components may have the same or similar structures and functions as described above with reference to FIG. 1.
[0043] It should be noted that the inlet and outlet valves 112 and 114 in FIG. 2 need not be variably openable valves (i.e., control valves) but could simply be valves that can be transitioned between fully opened and fully closed. Although, having the inlet and outlet valves 112 and 114 be variably openable may provide increased flexibility to the system.
[0044] As illustrated, the MPFM system 200 includes a first bypass flowline 202 connecting the inlet horizontal pipe section 108 on an upstream side of the inlet valve 112 to the inlet horizontal pipe section 108 on a downstream side of the inlet valve 112. A first bypass valve 204 is disposed along the first bypass flowline 202, as shown. The MPFM system 200 also includes a second bypass flowline 206 connecting the outlet horizontal pipe section 110 on an upstream side of the outlet valve 114 to the outlet horizontal pipe section 110 on a downstream side of the outlet valve 114. A second bypass valve 208 is disposed along the second bypass flowline 206, as shown. The bypass valves 204 and 208 have flow areas that are smaller thanthose of the inlet valve 112 and the outlet valve 114. Thus, the fully opened bypass valves 204 and 208 may provide a reduced flow (e.g., less than 10%, or less than 5%, or less than 2% of the full flow rate through the inlet / outlet valves) of three-phase fluid through the MPFM section 103 when the inlet and outlet valves 112 and 114 are closed.
[0045] Although shown as separate from the drain 124, the first bypass flowline 202 in other embodiments may connect the drain 124 to a location upstream of the inlet valve 112. In some embodiments, the upstream portion of the second bypass flowline 206 may be connected to the upper part of the vertical pipe section 104 (e.g., where a drain might otherwise be located) rather than the outlet horizontal pipe section 110.
[0046] The two bypass valves 204 and 208 may be the same size. When the bypass valves 204 and 208 are opened, liquid is encouraged to enter the bottom of the MPFM section 103 and gas is encouraged to exit the MPFM section 103, thus enabling the MPFM section 103 to accumulate liquid faster after measuring the gas fluid properties. Instead of having to turn the main inlet and outlet valves 112 and 114 by a precise amount (e.g., 5% of fully opened), the bypass flowlines 202 and 206 allow an operator to simply open the bypass valves 204 and 208 so that the flow rate going in around the inlet valve 112 and leaving around the outlet valve 114 is known. This provides greater precision and offers improved control in the process of filling the vertical pipe section with additional liquid, since the bypass valves 204 and 208 are smaller (e.g., the bypass piping size could be 14 of the skid piping size) than the inlet / outlet valves 112 and 114. In addition, using the bypass flowlines and valves may make the process for measuring gas, oil, and water properties easier to implement from an operations perspective (fully opening a smaller valve vs. partially opening a larger valve). However, using the larger inlet / outlet valves 112 and 114 may provide greater flexibility for the flow rate of additional fluid being introduced if those valves can be variably opened.
[0047] As illustrated, the first bypass valve 204 intersects the inlet horizontal pipe section 108 at a bottom edge of the pipe section 108 on both the upstream side of the inlet valve 112 and the downstream side of the inlet valve 112. This may encourage additional liquid (oil and water) to move into the MPFM section 103, as compared to gas, helping the column of water / oil / gas to move upwards more quickly in the vertical pipe section 104.
[0048] As illustrated, the second bypass valve 208 intersects the outlet horizontal pipe section 110 at a top edge of the pipe section 110 on both the upstream side of the outlet valve 114 and the downstream side of the outlet valve 114. This may encourage additional gas to move out of the MPFM section 103, as compared to liquids, helping the column of water / oil / gas to moveupwards more quickly in the vertical pipe section 104. In addition, the second bypass flowline 206 and bypass valve 208 can provide pressure equalization for the gas property measurements.
[0049] FIG. 3 illustrates a method 300 for measuring fluid properties of different phases in a three-phase fluid flowing at line conditions. It should be noted that the method 300 shown in FIG. 3 is merely an example and other embodiments may include additional steps not shown, have one or more illustrated steps removed, or have certain illustrated steps performed in different orders than shown, without departing from the scope of the present disclosure. Certain steps may be performed by an MPFM system (e.g., as shown in FIGS. 1 or 2), while other steps may be performed by an external computer communicatively coupled to sensor(s) of the MPFM system.
[0050] At block 302, the method 300 includes directing three-phase fluid at a full flow rate through a multiphase flow meter (MPFM) section, the MPFM section having a MPFM located along a vertical pipe section. In particular, the method 300 may include fully opening an inlet valve of the MPFM section and fully opening an outlet valve of the MPFM section to direct the three-phase fluid at the full flow rate through the MPFM section. At block 304, the method 300 includes halting the flow of three-phase fluid through the MPFM section to trap the three- phase fluid in the MPFM section. At block 306, the method 300 includes allowing the three- phase fluid trapped in the MPFM section to separate into a gas portion, an oil portion, and a water portion in the vertical pipe section. At block 308, the method 300 includes measuring a fluid property of the gas portion via a sensor in the MPFM. Block 308 provides the fluid property measurement for the gas phase at line conditions.
[0051] At block 310, the method 300 includes directing additional three-phase fluid through the MPFM section at a reduced flow rate less than the full flow rate such that the gas portion, oil portion, and water portion each move upward within the vertical pipe section. In some embodiments (e.g., using the system 100 of FIG. 1), this may involve partially opening the inlet valve of the MPFM and partially opening the outlet valve of the MPFM to direct the additional three-phase fluid through the MPFM section at the reduced flow rate. In other embodiments (e.g., using the system 200 of FIG. 2), block 310 may involve opening an inlet bypass valve along a first flowline that bypasses the inlet valve and opening an outlet bypass valve along a second flowline that bypasses the outlet valve to direct the additional three-phase fluid through the MPFM section at the reduced flow rate. In either case, the method 300 may include balancing a pressure of the MPFM section via movement of gas through or around the outlet valve while directing the additional three-phase fluid through the MPFM section. The method 300 may include taking continuous measurements of the fluid property via the MPFMduring the upward movement (block 310) of the gas portion, oil portion, and water portion through the vertical pipe section. Such continuous measurements of the fluid property may be displayed on a user interface (e.g., of the MPFM flow computer or an external computer) during the upward movement (block 310) of the gas portion, oil portion, and water portion through the vertical pipe section. In some embodiments, the method 300 may include opening a drain located downstream of the inlet valve to adjust a vertical position of an oil / water interface in the vertical pipe section during or after the upward movement (block 310) of the gas, oil, and water portions through the vertical pipe section.
[0052] At block 312, the method 300 includes halting the reduced flow of three-phase fluid through the MPFM section after a gas / oil interface passes a sensing location in the MPFM. The halting (block 312) of the reduced fluid flow may be performed in response to certain measurements of the fluid property (e.g., that were displayed to an operator via the user interface) indicating that the oil phase now fills the sensing window of the fluid property sensor in the MPFM. In other embodiments, the halting (block 318) of the reduced fluid flow may be in response to the passing of a pre-selected time (e.g., one hour), after which the fluid phase in front of the sensing window may or may not be confirmed by fluid property measurements. At block 314, the method 300 includes measuring the fluid property of the oil portion via the sensor in the MPFM. The method 300 may include closing the inlet valve and the outlet valve, e.g., to halt (block 312) the reduced fluid flow, before measuring the fluid property of the oil portion. Block 314 provides the fluid property measurement for the oil phase at line conditions.
[0053] At block 316, after measuring (block 314) the fluid property of the oil portion, the method 300 may include directing additional three-phase fluid through the MPFM section at a reduced flow rate less than the full flow rate such that the gas portion, oil portion, and water portion each move upward within the vertical pipe section. In some embodiments (e.g., using the system 100 of FIG. 1), this may involve partially opening the inlet valve of the MPFM and partially opening the outlet valve of the MPFM. In other embodiments (e.g., using the system 200 of FIG. 2), this may involve opening an inlet bypass valve along a first flowline that bypasses the inlet valve and opening an outlet bypass valve along a second flowline that bypasses the outlet valve. In either case, the method 300 may include balancing a pressure of the MPFM section via movement of gas through or around the outlet valve while directing the additional three-phase fluid through the MPFM section. Again, the method 300 may include taking continuous measurements of the fluid property via the MPFM during the upward movement (block 316) of the gas portion, oil portion, and water portion through the vertical pipe section. Such continuous measurements of the fluid property may be displayed on a userinterface (e.g., of the MPFM flow computer or an external computer) during the upward movement (block 316) of the gas portion, oil portion, and water portion through the vertical pipe section.
[0054] At block 318, the method 300 may include halting the reduced flow of three-phase fluid through the MPFM section after an oil / water interface passes the sensing location in the MPFM. The halting (block 318) of the reduced fluid flow may be performed in response to certain measurements of the fluid property (e.g., that were displayed to an operator via the user interface) indicating that the water phase now fills the sensing window of a fluid property sensor in the MPFM. In other embodiments, the halting (block 318) of the reduced fluid flow may be in response to the passing of a pre-selected time, after which the fluid phase in front of the sensing window may or may not be confirmed by fluid property measurements. At block 320, the method 300 may include measuring the fluid property of the water portion via the sensor in the MPFM. The method 300 may include closing the inlet valve and the outlet valve, e.g., to halt (block 318) the reduced fluid flow, before measuring the fluid property of the water portion. Block 320 provides the fluid property measurement for the water phase at line conditions.
[0055] At block 322, the method 300 may include generating lookup tables based on the measured fluid properties of the gas portion, oil portion, and water portion from blocks 308, 314, and 320, respectively. This step may be performed by a computer external to the MPFM system. The lookup tables may then be input into the MPFM flow computer to calibrate the MPFM. At block 324, the method 300 may include providing three-phase flow metering of the three-phase fluid via the calibrated MPFM based on the lookup tables.
[0056] FIGS. 4-8 detail a simulation that was performed to demonstrate the feasibility of filling the MPFM with the liquid phases through the controlled opening of the inlet and outlet valves (e.g., using the system of FIG. 1). Similar results would be expected from the controlled opening of bypass valves directing a reduced three-phase fluid flow around the inlet and outlet valves (e.g., using the system of FIG. 2).
[0057] The basis of the simulation design is shown in FIG. 4. A three-phase transient flow model with component tracking (compositional model) was performed. FIG. 4 shows the schematic of the MPFM skid built in the simulation and details the flow and fluid properties.
[0058] The design constraints of the simulation were as follows:
[0059] Outlet pressure = 200 psia
[0060] Flow rate = 200 blpd at 50% wc
[0061] Inlet temperature = 100F
[0062] Ambient temperature = 50F
[0063] Piping ID = 4 inch
[0064] Piping roughness = 0.00197 inch
[0065] Piping insulation = None
[0066] Composition = Methane / decane mixture (see table at the right)
[0067] Oil density = 732 kg / mA3 at STP
[0068] GOR = 455 scf / stb
[0069] The modeling procedure was as follows:
[0070] Flow at 200 blpd with connection valve closed
[0071] Open connection valve and close MPFM valves
[0072] Let MPFM piping reach ambient condition
[0073] Crack open MPFM valves at 1% open, leaving connection valve open
[0074] Close MPFM valves and let MPFM piping reach ambient condition
[0075] FIG. 5 illustrates a steady state hold-up profile of the MPFM section (e.g., 103) as generated by the model of FIG. 4. This steady state hold-up profile represents the liquid profile in the MPFM section (e.g., 103) of the skid when the inlet and outlet valves (e.g., 112 and 114) are fully open and the bypass valve (e.g., 118) is closed. The pipeline length along the X-axis represents the different pipe sections (inlet horizontal (e.g., 108), vertical (e.g., 104), and outlet horizontal (e.g., 110)) of the MPFM system. In the simulation, the inlet valve (e.g., 112) is located at the 3 ft location along the X-axis, while the outlet valve (e.g., 114) is located at the 15 ft location along the X-axis. As shown in FIG. 5, at steady state conditions approximately 70% of the vertical pipe section is filled with liquid (about half water), and the horizontal pipe sections have less liquid.
[0076] FIG. 6 illustrates a shut-in hold-up profile of the MPFM section (e.g., 103) as generated by the model of FIG. 4. This shut-in hold-up profile represents the liquid profile in the MPFM section (e.g., 103) of the skid when the inlet and outlet valves (e.g., 112 and 114) are closed and the bypass valve (e.g., 118) is open. Again, the pipeline length along the X-axis represents the different pipe sections of the MPFM section. As shown in FIG. 6, the vertical pipe section (e.g., 104) drains off liquid during shut-in while some liquid becomes trapped in the horizontal pipe sections (e.g., 108 and 110). Before liquid accumulation, there is almost entirely gas present in the vertical pipe section. The inlet horizontal pipe section (e.g., 108) has about 50% liquid hold-up downstream of the inlet valve (e.g., 112) with half of that being water.
[0077] FIG. 7 illustrates an accumulation of water phase taking place in the vertical MPFM section when the inlet and outlet valves (e.g., 112 and 114) are cracked open (and the bypassvalve 118 remains open) providing a reduced flow of three-phase fluid through the MPFM section. As shown in FIG. 7, the valves (e.g., 112 and 114) are closed again after one hour. As shown, the oil / water interface is moving up as more liquid is added to the system via the cracked open valves. This indicates that the water volume does increase in the MPFM section for the one hour that the inlet and outlet valves are open, moving the gas / oil interface further upwards to pass the sensing window in the MPFM. Note the total volume of one six foot section is about 0.09 bbl.
[0078] FIG. 8 illustrates a shut-in hold-up profile of the MPFM section (e.g., 103) generated by the simulation after the liquid accumulation shown in FIG. 7. This shut-in hold-up profile represents the liquid profile in the MPFM section (e.g., 103) of the skid when the inlet and outlet valves (e.g., 112 and 114) are again closed and the bypass valve (e.g., 118) remains open after the liquid accumulation. Again, the pipeline length along the X-axis represents the different pipe sections of the MPFM section. As shown in FIG. 8, the window of oil is preceding the window of water. This demonstrates that, after the liquid accumulation, the vertical pipe section (e.g., 104) is full of liquid with the oil / water interface slightly below the assumed MPFM location at 3 ft into the vertical pipe section (i.e., 9 ft along the X-axis).
[0079] The simulation and results of FIGS. 4-8 demonstrate that following certain steps outlined in FIG. 3 allows for liquid accumulation within the vertical pipe section of the MPFM system. As such, the disclosed MPFM systems and calibration methods may be used to provide self-calibration of an MPFM by measuring fluid properties of gas, oil, and water at line conditions at the location of the MPFM, not at an external PVT laboratory.
[0080] It will be understood that various modifications may be made to the embodiments disclosed herein. Therefore, the above description should not be construed as limiting, but merely as exemplifications of example embodiments. For example, the functions described above and implemented as the best mode for operating the present invention are for illustration purposes only. Other arrangements and methods may be implemented by those skilled in the art without departing from the scope and spirit of this invention. Moreover, those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.
Claims
CLAIMSWhat is claimed is:
1. A method for measuring fluid properties of different phases in a three-phase fluid flowing at line conditions, the method comprising: directing the three-phase fluid at a full flow rate through a multiphase flow meter (MPFM) section, the MPFM section having an MPFM located along a vertical pipe section; halting the flow of three-phase fluid through the MPFM section to trap the three-phase fluid in the MPFM section; allowing the three-phase fluid trapped in the MPFM section to separate into a gas portion, an oil portion, and a water portion in the vertical pipe section; measuring a fluid property of the gas portion via a sensor in the MPFM; directing additional three-phase fluid through the MPFM section at a reduced flow rate less than the full flow rate such that the gas portion, oil portion, and water portion each move upward within the vertical pipe section; halting the reduced flow of three-phase fluid through the MPFM section after a gas / oil interface passes a sensing location in the MPFM; and measuring the fluid property of the oil portion via the sensor in the MPFM.
2. The method of claim 1, further comprising: after measuring the fluid property of the oil portion, directing additional three-phase fluid through the MPFM section at the reduced flow rate such that the gas portion, oil portion, and water portion each move upward within the vertical pipe section; halting the reduced flow of three-phase fluid through the MPFM section after an oil / water interface passes the sensing location in the MPFM; and measuring the fluid property of the water portion via the sensor in the MPFM.
3. The method of claim 1, further comprising: generating lookup tables based on the measured fluid properties of the gas portion, oil portion, and water portion; and providing three-phase flow metering of the three-phase fluid via the MPFM based on the lookup tables.
4. The method of claim 1, further comprising: fully opening an inlet valve of the MPFM section and fully opening an outlet valve of the MPFM section to direct the three-phase fluid at the full flow rate through the MPFM section, wherein: the inlet valve is disposed along an inlet horizontal pipe section coupled to a lower end of the vertical pipe section, and the outlet valve is disposed along an outlet horizontal pipe section coupled to an upper end of the vertical pipe section.
5. The method of claim 4, further comprising partially opening the inlet valve of the MPFM and partially opening the outlet valve of the MPFM to direct the additional three-phase fluid through the MPFM section at the reduced flow rate.
6. The method of claim 4, further comprising opening an inlet bypass valve along a first flowline that bypasses the inlet valve and opening an outlet bypass valve along a second flowline that bypasses the outlet valve to direct the additional three-phase fluid through the MPFM section at the reduced flow rate.
7. The method of claim 4, further comprising opening a drain located downstream of the inlet valve to adjust a vertical position of an oil / water interface in the vertical pipe section.
8. The method of claim 4, further comprising balancing a pressure of the MPFM section via movement of gas through or around the outlet valve while directing the additional three- phase fluid through the MPFM section.
9. The method of claim 4, further comprising closing the inlet valve and the outlet valve before measuring the fluid property of the oil portion.
10. The method of claim 4, further comprising: closing a bypass valve along a bypass pipe section while directing the three-phase fluid at the full flow rate through the MPFM section, the bypass pipe section coupling an upstream side of the inlet horizontal pipe section to a downstream side of the outlet horizontal pipe section;opening the bypass valve while halting the flow of three-phase fluid through the MPFM section; and keeping the bypass valve open while directing the additional three-phase fluid through the MPFM section at the reduced flow rate.
11. The method of claim 1, further comprising measuring the fluid property of the gas portion after at least a pre-selected time after halting the flow of three-phase fluid through the MPFM section.
12. The method of claim 1, further comprising taking continuous measurements of the fluid property via the MPFM during the upward movement of the gas portion, oil portion, and water portion through the vertical pipe section.
13. The method of claim 12, wherein the continuous measurements of the fluid property are displayed on a user interface during the upward movement of the gas portion, oil portion, and water portion through the vertical pipe section.
14. A system, comprising: a vertical pipe section; a multiphase flow meter (MPFM) located along the vertical pipe section; an inlet horizontal pipe section coupled to a lower end of the vertical pipe section; an outlet horizontal pipe section coupled to an upper end of the vertical pipe section; an inlet valve disposed along the inlet horizontal pipe section; an outlet valve disposed along the outlet horizontal pipe section; a first bypass flowline connecting the inlet horizontal pipe section on an upstream side of the inlet valve to the inlet horizontal pipe section on a downstream side of the inlet valve; a second bypass flowline connecting the outlet horizontal pipe section on an upstream side of the outlet valve to the outlet horizontal pipe section on a downstream side of the outlet valve; a first bypass valve disposed along the first bypass flowline, the first bypass valve having a flow area smaller than the inlet valve; and a second bypass valve disposed along the second bypass flowline, the second bypass valve having a flow area smaller than the outlet valve.
15. The system of claim 14, wherein the inlet valve and the outlet valve are the same size.
16. The system of claim 14, wherein the first bypass valve and the second bypass valve are the same size.
17. The system of claim 14, wherein the first bypass valve intersects the inlet horizontal pipe section at a bottom edge of the inlet horizontal pipe section on both the upstream side of the inlet valve and the downstream side of the inlet valve.
18. The system of claim 14, wherein the second bypass valve intersects the outlet horizontal pipe section at a top edge of the outlet horizontal pipe section on both the upstream side of the outlet valve and the downstream side of the outlet valve.
19. The system of claim 14, further comprising a selectively openable drain coupled to the inlet horizontal pipe section on the downstream side of the inlet valve.
20. The system of claim 14, wherein the inlet valve and the outlet valve are configured to be variably opened.
21. The system of claim 14, wherein the inlet valve and the outlet valve are ball valves.
22. The system of claim 14, wherein the MPFM comprises a permittivity sensor, a Gammaspectroscopy sensor, an electrical sensor, an optical sensor, a differential pressure sensor, an acoustic sensor, or a combination thereof.