NL2018493B1

NL2018493B1 - Orifice carrier flange

Info

Publication number: NL2018493B1
Application number: NL2018493A
Authority: NL
Inventors: Johanna Arnoldus Martens Franciscus; Atze Taede Martens Dennis
Original assignee: Shell Int Research
Priority date: 2017-03-09
Filing date: 2017-03-09
Publication date: 2018-09-21

Abstract

An orifice assembly is described that has an orifice plate arranged in a non-vertical pipe section. The non-vertical pipe-section has a flow conduit having an inner wall defining a circular cross section around a longitudinal central axis, with an internal cross sectional area through which a fluid can flow in a flow direction along the flow conduit. The orifice plate is transversely disposed in the flow conduit. The orifice plate is provided with a single orifice arranged eccentrically within the circular cross section of the flow conduit.

Description

Field of the invention

The present invention relates to an orifice carrier flange. The flange can be arranged in a pipe section. The flange can be used, for instance, with a differential pressure meter mounted on the orifice carrier flange.

Background of the invention

An orifice assembly for a differential pressure meter typically comprises an orifice plate that can be positioned in a flow conduit of a pipe section. Due to the flow restriction, a pressure differential is created across the orifice plate from which the flow rate of the fluid flowing through the flow conduit can be derived.

Emerson offers the Rosemount 405 Compact Orifice Plate as a fully integrated solution that eliminates the need for fittings, tubing, valves, adapters, manifolds and mounting brackets. Technical information about the Rosemount 405 series can be found in a product data sheet titled Rosemount 405 Compact Primary Element and dated June 2013 (document number 00813-0600-4485, Rev EC). The Rosemount 405 Compact Orifice Plate (type code P) has an orifice plate provided with a single concentric orifice mounted integrally inside an annular flange.

Alternatively, there is the Rosemount 405 Conditioning Orifice Plate (type code C) which is provided with four orifice holes, whereby pairs of holes are vertically arranged above each other. In either case, instrument valves and a transmitter connection are provided on the same flange.

Application of this type of orifice plate has been found to be problematic for multiphase flowlines. Particularly, application of this type of orifice plates in flow conduits connected to hydrocarbon wells has been found to be problematic.

Summary of the invention

In accordance with a first aspect of the present invention, there is provided an orifice carrier flange adapted to be arranged in a pipe section, said pipe section having a flow conduit having an inner wall defining a circular cross section around a longitudinal central axis, with an internal cross sectional area through which a fluid can flow in a flow direction along the flow conduit, which orifice assembly comprises an orifice plate that is transversely disposed in the flow conduit, wherein the orifice plate is provided with a single orifice within the flow conduit, wherein the single orifice has a transverse open flow area that is smaller than the internal cross sectional area and wherein the orifice plate blocks fluid flow outside of the single orifice, wherein the single orifice is arranged within the circular cross section of the flow conduit.

In an embodiment, the single orifice is arranged centrically within the circular cross section of the flow conduit.

In another embodiment, the single orifice is arranged eccentrically within the circular cross section of the flow conduit.

Where the flow conduit is horizontal and where it may contain solids such as sand, as is often the case with flow conduits connected to hydrocarbon wells, the single orifice is preferentially centered vertically below the longitudinal central axis.

Suitably, the orifice plate comprises a rim circumferencing and defining the single orifice, wherein the rim tangentially coincides with the inner wall of the flow conduit. This may include the lowest point of the inner wall of the flow conduit within the plane of the orifice plate. Suitably, the single orifice and/or the rim has a circular contour.

Alternatively, where the flowing conduit is vertical or where it does not contain solids said orifice can be located in the centre of the flowing conduit

The orifice assembly may form part of a differential pressure meter, which further comprises:

~ at least an upstream pressure port on one side of the orifice plate relative to the flow direction and at least a downstream pressure port on another side of the flow orifice plate relative to the flow direction; and

- connection means for receiving a differential pressure sensor configured to measure a pressure differential between the upstream pressure port and the downstream pressure port .

Suitably, the upstream pressure port and the downstream pressure port establish a fluid communication between the flow conduit and the differential pressure sensor .

Isolation valves may be arranged in the pressure ports, to selectively isolate the connection means from the flow conduit. These isolation valves are preferably piping-class rated, which makes the orifice assembly suitable for a wider scope of applications such as for use in flow conduits connected to hydrocarbon wells.

Preferably, the upstream pressure port and the downstream pressure port are centered above the longitudinal central axis.

Suitably, the orifice plate is mounted between two carrier rings. Said carrier rings provide a circular channel which connects to the pressure ports on the inside of the flange. The upstream carrier ring connects to the upstream pressure port. The downstream carrier ring connects to the downstream pressure port. The upstream carrier ring may also serve as the raised face contact surface of the flange assembly.

Suitably, both the upstream and the downstream sides of the orifice plate are provided with a ridge. The inside of this ridge coincides with the internal diameter of the flow conduit. The outside of this ridge coincides with the outside diameter of the orifice plate.

both provided with one or more lateral

These ridges are grooves that provide connection between either side of the orifice plate to the carrier rings and onwards to the pressure ports. The design of these ridges and grooves complies to corner tappings .

The use of place when carrier rings allows replacement of the orifice the flange is removed from the flowing conduit.

Preferably, the connection means for receiving the differential pressure sensor are provided using a separate construction. This construction provides a connection means to the pressure sensor based on either IEC 61518 or an equivalent standard.

The invention will be further illustrated hereinafter by way of example only, and with reference to the non limiting drawing.

Brief description of the drawing

Fig. 1 shows a perspective and partially cut-away view of a first embodiment of an orifice plate differential pressure meter arranged in a non-vertical pipe section;

Fig. 2 shows a perspective and partially cut-away view of a second embodiment of an orifice plate differential pressure meter arranged in a non-vertical pipe section;

Fig. 3 shows a possible application of the presently proposed orifice plate differential pressure meter.

These figures are not to scale. Identical reference numbers used in different figures refer to similar components;

Fig. 4 shows a perspective and exploded view of an embodiment of an orifice carrier flange of the present disclosure;

Fig. 5 shows a sectional side view of the orifice carrier flange of Fig. 4; and

Fig. 6 shows a detail of Fig. 5 (indicated by circle C in Fig. 5) .

Detailed description of the invention

For the purpose of this description, the term orifice plate differential pressure meter is used to specifically refer to differential pressure meters that employ an orifice assembly in accordance with the present disclosure. A differential pressure determined using such an orifice plate differential pressure meter may optionally be converted to a signal that is proportional to flow rate, if so desired. ISO 5167 contains equations that can be helpful for this purpose, or other equations can be used depending on the required accuracy.

The presently proposed orifice assembly comprises an orifice plate that is provided with a single orifice arranged eccentrically within the circular cross section of the flow conduit. In the context of the present application, the term single means exclusively one. Ic has been found that such eccentric single orifice provides a more stable flow measurement in case of sudden changes in multiphase flow (mixed flow). The single orifice may be arranged vertically above the longitudinal axis of the flow conduit, in the centre of the flow conduit or below. Preferably it is arranged below the longitudinal axis to avoid build-up of heavier constituents in the mixed flow on the upstream side of the orifice plate. Suitably, the single orifice is centered vertically below the longitudinal central axis.

The orifice plate may comprise a rim circumferencing and defining the single orifice, wherein the rim tangentially coincides with the inner wall of the flow conduit. If the single orifice is also centered vertically below the longitudinal central axis, this configuration would allow solids to pass the orifice plate. An orifice assembly that does not comprise an orifice that touches the bottom of the flow conduit vertically below the longitudinal central axis may accumulate solid debris just upstream of the orifice plate, which will affect the reliability and accuracy of flow measurements based on differential pressure.

Figure 1 shows an example embodiment of an orifice assembly that comprises an orifice plate 110 arranged in a non-vertical pipe section 120. The non-vertical pipe section 120 has pipe pieces 122 and 124 in which a flow conduit 125 is located. The flow conduit 125 has an inner wall 128 defining a circular cross section around a longitudinal central axis L. The circular cross section has an internal cross sectional area through which a fluid can flow in a flow direction along the longitudinal direction in the flow conduic 125. The orifice plate 110 is transversely disposed in the flow conduit 125.

Suitably the orifice assembly comprises an annular frame 130, which holds the orifice plate 110 in place within the annular frame 130. The annular frame 130 can suitably be clamped between two pipe flanges (132, 134), whereby one pipe flange is located on each side of the annular frame 130. The annular frame 130 may itself function as a flange that cooperates with the pipe flanges 132, 134. The pipe flanges may form, part of the nonvertical pipe section that defines the flow conduit 125. Suitably, the annular frame is traversed with through holes 135 that align with holes in the pipe flanges that enable bolt/nut assembly. Alternatively, the annular frame may have a diameter that is small enough to be held inside the bolts that project through the holes in the pipe flanges. Either way, optional gaskets may be provided between the pipe flanges (132, 134) and the annular frame 130 to effectively seal off the flow conduit from the ambient. Examples of gaskets include rubber, silicone, and metal gaskets, including O-rings and flat packers such as copper packers.

The orifice plate 110 is provided with a single orifice 115 within the flow conduit 125. An inner rim 117 circumferences the single orifice 115 and defines it. The single orifice 115 has a transverse open flow area that is smaller than the internal cross sectional area of the flow conduit 125. The remainder of the orifice plate 110 is effective to block fluid flow outside of the single orifice 115.

As can be seen in Fig. 1, the single orifice 115 is arranged eccentrically within the circular cross section of the flow conduit 125. The inner rim 117 has a circular contour. Calculation of the flow factor of the orifice plate 110, and sizing of the single orifice 115, can thus be approximated sufficiently by equations defined in ISO 5167-2. It has been found that devices having multiple orifices cannot easily be calculated using the ISO 5167-2 equations. In the embodiment as shown in Figure 1, the single orifice is centered vertically below the longitudinal central axis L. The rim 117 tangentially coincides with the inner wall 128 of the flow conduit. Preferably, the rim 117 touches the inner wall 128 of the flow conduit 125 in the lowest part of the circular cross section, i.e. vertically below the longitudinal central axis L.

In order to use the orifice plate in a differential pressure meter, an upstream pressure port 142 may be provided on one side of the orifice plate 110, relative to the flow direction, and a downstream pressure port 144 may be provided on another side of the flow orifice plate 110, relative to the flow direction. In the embodiment of Figure 1, these pressure ports 142,144 are integrated into the pipe flanges 132,134. This arrangement is referred to in ISO 5167-2 as 'flange taps' .

Figure 2 shows an alternative embodiment, wherein the pressure ports 142, 144 are integrated directly into the construction frame 130 of the orifice plate 110. This embodiment may be referred to as integrated orifice assembly. An advantage of such integrated orifice assembly is that additional equipment including isolation valves and means for connecting pressure sensors or a differential pressure sensor, and the pressure sensors or differential pressure sensors themselves, may together with the orifice form an integral differential pressure meter.

In either case, the upstream pressure port 142 and the downstream pressure port 144 are centered vertically above the longitudinal central axis L. This reduces the probability of solid particles entering the pressure ports. At the same time, the diameter of these pressure ports is as large as feasible, to reduce the chance of blockages by solids. Particularly in oil-field applications, solids m.ay be formed in stagnant fluids that cool to below solidification point of hydrates and/or waxy deposits. Integration of the pressure ports with either the pipe flanges or the constructive frame of the orifice plate facilitates keeping the stagnant fluids above the solidification point by thermal conduction to warmer fluids that are continuously refreshed in the flow conduit 125 .

Figures 4 to 8 show an alternative embodiment, wherein the orifice plate 110 is enclosed by a first carrier ring 150 and a second carrier ring 152. The correct orientation of the carrier rings 150, 152 and the orifice plate 110 can be achieved by one or more locating pins 160. The one or more pins 160 avoid locating the orifice 115 in another location than the lowest and it will also ensure the fluid flow through the orifice is in the correct direction. Respective parts, rings, and flanges can be sealed with respect to one another using seal rings 162 -- 168. The seals rings can be, for instance, O-rings 162, 164, 166. Alternatively, the seal rings can be a graphite seal 168.

The connection means for receiving the differential pressure sensor are provided using a separate 'manifold' 170. The manifold 170 may comprise, for instance, a first bolted mounting flange 172 to allow the manifold to be connected to the flange 130; a second bolted mounting flange 174 to connect a differential pressure sensor; fluid passages 176, 178 to allow fluid passage to the differential pressure sensor. In addition, the manifold may comprise one or more, for instance two isolation valves; and one or more equalisation valve (not shown).

The manifold 170 may allow a 90 degree rotation between the relative position of the entry ports on the side of the embodiment and those on the differential pressure sensor. This avoids the valves on the manifold from interfering with nearby equipment.

The orifice assembly described herein may be used in a differential pressure meter that is specifically suited for use in two-phase flow lines with potential of solids being present. Such differential pressure meter may be used to flow control oil and gas production rates from a hydrocarbon well. Examples of specific applications wherein the orifice plate differential meter may for instance be used are described in US patents 7,222,542 and 8,302,684 to Eken, whereby the orifice assemblies described herein may fulfil the function of the flow restriction described in the patents. These patents are incorporated herein by reference. An example is worked out below in more detail.

Figure 3 shows a well 1 extending from surface 3 into a subsurface formation 5. The well is provided with casing 7, and at the lower end of the well perforations 8 are arranged for receiving reservoir fluid into the well. Production tubing 10 is installed, separated by a packer 12 from the casing. The production tubing extends from its upstream end 14 to a wellhead 15 at the surface 3, and from there through a flow line 18 to downstream processing equipment 20, e.g. including a gas/liquid separator or a three-phase separator. Along the flow line a control system is arranged, comprising a controllable variable valve 30, an orifice plate differential pressure meter 50, and a controller 40 receiving input via line 46 from the orifice plate differential pressure meter 50, and having an output via line 49 for a control signal to the controllable valve 30. If desired, the orifice plate differential pressure meter 50 can also be placed upstream near the control valve 30.

Suitably, the upstream pressure port 142 and the downstream pressure port 144 establish a fluid communication between the flow conduit in flow line 18 and a differential pressure sensor 58. Such pressure sensor 58 may be provided in the form of a differential pressure transmitter. Isolation valves 52, 54 may be arranged in the pressure ports 142, 144, to selectively isolate the differential pressure sensor from the flow conduit. For certain applications, these isolation valves must be piping-class rated. In the example of Figure 4, the isolation valves 52, 54 are arranged in a manifold 56. The manifold 56 also forms the connection means on which the differential pressure sensor 58 can be mounted. The sensor interface flange is suitably compliant with IEC 61518, or any other standard that is used in the industry. The manifold 56 may also comprise an equalisation valve.

The reservoir fluid received through perforations 8 into the well normally is a multiphase fluid comprising liquid and gas, and typically also solids such as deposits, scale, sand, etc. The gas~to~liquid ratio at bottom hole conditions can depend on many factors, for example the composition of the undisturbed reservoir fluid, influx from other subsurface regions, the amount of gas dissolved in oil, and liberation of dissolved gas due to the pressure difference between the reservoir and the well. Instability in production of this multiphase fluid to surface can be observed in varying severity, also dependent on the overall production rate, tubing geometry and reservoir influx performance.

Such instabilities can be effectively controlled by manipulation of the downstream valve 30. To this end a flow parameter of the multiphase fluid is selected, which is responsive to changes in the gas/liquid ratio of the multiphase fluid at an upstream position in the well, such as at the lower end of the production tubing or at the perforations .

A suitable flow parameter is the volumetric flow rate or also the mass flow rate of the multiphase fluid. For an effective control it is not required to determine these flow rates with high accuracy but a stable control signal is needed based on relative flow rate. The orifice plate of the present invention is perfectly capable of providing this feedback signal. Most importantly, changes in the gas/liquid ratio are quickly detected.

The flow parameter is preferably measured at surface. A particularly advantageous aspect of the system shown in Figure 3, is that the flow parameter is monitored by continuously monitoring the pressure difference over the orifice plate only, without monitoring another variable in order to determine an actual gas/liquid ratio pertaining to the actual pressure difference at the flow restriction. This is advantageous since it was realized that is not needed for the present invention to install equipment for measuring data pertaining to the multiphase composition, e.g. a specific small separator for control purposes, an expensive multiphase flow merer or a gamma densitometer. In the prior art such equipment is used to determine a mass balance of the multiphase fluid, e.g. a gas mass fraction, and the changes thereof as a function of time at the location of the measurement. Using such data, accurate volumetric or mass flow rates, and changes thereof as a function of time, can be derived.

It has been realized however, that a suitable flow parameter for use as controlled, variable in the multiphase flow control can be derived from the pressure data alone, and that efficient control is obtained when the aperture of the variable valve is used as the manipulated variable. In this way a relatively simple, but effective, control loop is obtained that requires minimum hardware.

The application of the orifice assembly in the hydrocarbon flow line 18 as described above is merely an example. It will be well appreciated that the orifice assembly described herein may also be employed in other applications, such as for example in injection wells for gas, steam, or water.

The person skilled in the art will readily understand that, while the invention has been illustrated making reference to one or more a specific combinations of features and measures, many of those features and measures are functionally independent from other features and measures such that they can be equally or similarly applied independently in other embodiments or combinations .

The present invention can be carried out in various ways within the scope of the appended claims, wherein many modifications are conceivable. Features of respective embodiments may for instance be combined.

SP1879

Claims

CONCLUSIONS

A flow restriction device disposed in a non-vertically extending pipe section (120), which non-vertically extending pipe section (120) comprises a screed tube (125) with an inner wall (128) having a circular cross-section around a central longitudinal axis (L) and an internal cross-sectional area available for flowing a fluid in a flow direction along the longitudinal axis (L), which flow restriction device comprises a restriction plate (110) which is arranged transversely in the diffuser tube (125), which restriction plate (110) is provided with a single flow hole (115) that has a flow surface that is smaller than the internal cross-sectional area of the flow tube (125), and which narrowing plate (110) blocks the fluid outside the single flow hole, the single flow hole (115) ) is arranged eccentrically within the circular cross section of the flow tube (125).

The flow restriction device according to claim 1, wherein the single flow hole (115) is centered vertically below the longitudinal axis (L).

The flow restriction device according to claim 1 or 2, wherein an edge (117) is located in the restriction plate (110) around the single flow hole (115), which edge defines the single flow hole (115).

The flow restriction device according to claim 3, wherein the edge (117) around the single flow hole (115) coincides tangentially with the inner wall (128) of the flow tube (125).

The flow restriction device according to claim 4, wherein the lowest point of the inner wall (128) of the flow tube is located in the transverse plane of the restriction plate (110) where the edge (117) around the single flow hole (115) coincides tangentially with the inner wall (128) of the flow tube (125).

The flow restriction device according to any one of the preceding claims, wherein the single flow hole (115) and / or the edge (117) around the single flow hole (115) has a circular contour.

The flow restriction device according to any of the preceding claims, further comprising an annular frame (130) in which the restriction plate (110) is held in place.

A differential pressure meter comprising a flow restriction device according to any one of the preceding claims as well as:

- at least one upstream pressure port (142) located on one side of the restriction plate (110) relative to the flow direction, and at least one downstream pressure port (144) located on another side of the direction of flow the restriction plate (110) is; and

- fixing means (56) for attaching a differential pressure sensor (58), which differential pressure sensor (58) is adapted to measure a pressure difference between the upstream pressure port (142) and the downstream pressure port (144).

The differential pressure meter according to claim 8, wherein fluid communication can take place between the flow tube and the differential pressure sensor.

The differential pressure gauge according to claim 9, wherein isolation valves (52, 54) are provided in the pressure ports to enable the fluid pressure attachment means (58) to be insulated from the flow tube for liquids, if desired.

The differential pressure gauge according to claim 10, wherein the isolation valves (52, 54) are tested for use in pipelines.

The differential pressure gauge according to any of claims 8 to 11, wherein the upstream pressure port (142) and the downstream pressure port (144) are both centrally above the longitudinal axis (L).

The differential pressure meter according to any of claims 8 to 12, wherein the flow restriction device of claim

7 satisfies, and wherein the pressure ports are integrally arranged in the annular frame (130).

The differential pressure meter according to claim 13, wherein furthermore the fastening means for the differential pressure sensor (58) are integrally connected to the annular

10 frame (130) by a single construction.

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