OA10580A - Gas lift flow control device - Google Patents
Gas lift flow control device Download PDFInfo
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- OA10580A OA10580A OA60825A OA60825A OA10580A OA 10580 A OA10580 A OA 10580A OA 60825 A OA60825 A OA 60825A OA 60825 A OA60825 A OA 60825A OA 10580 A OA10580 A OA 10580A
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- 238000004519 manufacturing process Methods 0.000 claims abstract description 63
- 238000002347 injection Methods 0.000 claims description 85
- 239000007924 injection Substances 0.000 claims description 85
- 239000012530 fluid Substances 0.000 claims description 43
- 238000000034 method Methods 0.000 claims description 14
- 230000003247 decreasing effect Effects 0.000 claims description 7
- 239000007789 gas Substances 0.000 description 261
- 230000007423 decrease Effects 0.000 description 13
- 238000011144 upstream manufacturing Methods 0.000 description 13
- 230000015572 biosynthetic process Effects 0.000 description 11
- 238000005755 formation reaction Methods 0.000 description 11
- 239000007788 liquid Substances 0.000 description 9
- 230000000694 effects Effects 0.000 description 8
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- 230000001276 controlling effect Effects 0.000 description 5
- 239000000203 mixture Substances 0.000 description 4
- 239000003208 petroleum Substances 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 230000006835 compression Effects 0.000 description 3
- 238000007906 compression Methods 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
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- 238000010276 construction Methods 0.000 description 2
- 230000002706 hydrostatic effect Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 238000009491 slugging Methods 0.000 description 2
- 230000000087 stabilizing effect Effects 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 241000746181 Therates Species 0.000 description 1
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- 230000003190 augmentative effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
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- 239000002783 friction material Substances 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
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Classifications
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/12—Methods or apparatus for controlling the flow of the obtained fluid to or in wells
- E21B43/121—Lifting well fluids
- E21B43/122—Gas lift
- E21B43/123—Gas lift valves
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- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Physics & Mathematics (AREA)
- Flow Control (AREA)
- Feeding And Controlling Fuel (AREA)
- Jet Pumps And Other Pumps (AREA)
- Fluid-Driven Valves (AREA)
- Control And Safety Of Cranes (AREA)
- Separation By Low-Temperature Treatments (AREA)
- Load-Engaging Elements For Cranes (AREA)
- Control Of Steam Boilers And Waste-Gas Boilers (AREA)
- Valve-Gear Or Valve Arrangements (AREA)
- Lighters Containing Fuel (AREA)
- Chemical Vapour Deposition (AREA)
Abstract
A gas flow control device (60) for injecting gas into a downhole production string for recovering pressure and reducing frictional losses, so that critical flow can be reached at lower pressure drops and higher production pressure, includes a housing, inlet ports (54), nose end (61) with check valve (65), and outlet ports (64), and a nozzle (34) having first and second ends, and a flow path therebetween, and a Venturi having first and second ends, and a flow path therebetween. The first end of the Venturi portion is disposed adajcent to the second end of the nozzle. The Venturi flow path is coaxially aligned with the nozzle flow path to provide a continuous flow path therethrough. Such a flow control device that has a gas flow rate performance that is independent of the tubing pressure, even when the tubing pressure is as high as 80 % to 93 % of the casing pressure, can be used to increase the production rate, improve the lift efficiency, and eliminate or suppress instability in continuous-flow gas lift wells.
Description
*>10580 - 1 -
GAS LIFT FLOW CONTROL DEVICE
The présent invention relates to a gas lift flowcontrol device for injecting gas into the production stringof a subterranean well utilizing gas lift equipraent andtechniques to enhance the flow of liquids from a geological' S formation.
In producing liquids, including water, oil, andoil with entrained gas, from a geological formation, naturalpressure in the réservoir acts to lift the liquids in awellbore upwards to the surface. The réservoir pressure ÎO must exceed the hydrostatic head of the fluid in the wellbore and any back-pressure imposed by the productionfacilities at the surface for the well to produce naturally.The réservoir pressure can décliné over time, requiringartificial steps to improve lift. One commonly known
2 method of augmenting lift is to inject gas into the productionstring, or tubing, to decrease the density of the fluid, therebydecreasing the hydrostatic head to allow the réservoir pressureto act more favorably on the fluids to be lifted to the surface. 5 This gas injection is usually accomplished by forcing gas downthe annulus between the production tubing, which conductsréservoir fluids to the surface, and the casing of the well.Then the gas is constrained to flow through a gas flow controldevice at a predetermined depth into the production tubing. The 1θ gas bubbles mix with the réservoir fluids, thus reducing theoverall density of the mixture and improving lift.
Alternatively, gas and/or relatively less dense fluids fromanother formation penetrated by the wellbore can be constrained 'to flow into the production tubing to decrease the overall 15 density of the fluids to be produced from the well. Thisprocedure, commonly referred to as autolifting, uses formationfluids (gas or light hydrocarbon liquids) from another formationhaving a formation pressure greater than the formation from whichthe liquids to be lifted are produced. Thus, instead of 20 compressing gas at the surface and injecting the gas down thecasing of the well· to the flow control device, another formationhaving sufficiently higher pressure is isolated to where the gasand/or less dense fluid from the isolated formation isconstrained to flow down the annulus between the casing and theproduction tubing, through the flow control device, and into theproduction tubing, thereby reducing the overall density of themixture in the production tubing and providing lift. θ10580 3
There are two types of gas flow control devices commonlyemployed to control the injected gas into the production tubing,namely gas lift valves and orifice valves. Gas lift valves arenormally closed in a biased position whereby a movable stem is 5 forced upon a matching seat to close the gas lift valve andprevent the flow of injected gas therethrough. On the otherhand, orifice valves hâve no moving parts other than a checkvalve to prevent reverse flow therethrough. Therefore, orificevalves are simply open to flow of injection gas, but are closed 10 to flow in the opposite direction.
Gas lift valves are used as unloading valves at different locations throughout the well, and may also be used to controlthe injection of the gas at the most optimum point of injection.Orifice valves are used to control injection gas rates into the 15 production tubing at the optimum point of injection. In certainsituations, gas lift valves are sometimes considered lessdésirable because of their expense and because of theirconstruction, namely the stem and seat arrangement, obstructs gasflow. An orifice valve overcomes both of these objections, and, 20 therefore, is often employed at the optimum point of injection.The valve that is installed at the optimum point of injection iscommonly called the operating valve.
Flow instability is a common problem existing in wells whichemploy continuous-flow gas lift. Flow instability results in (1) 25 large fluctuations in the production flow rate, (2) largefluctuations in the gas injection rate, and (3) largefluctuations- in the pressure of both the tubing and casing.Understanding the influence that the gas flow control device has 0 î 058 Ο 25 4 on flow instability is crucial to understanding the présent invention.
Flow instability in a continuons-flow gas lift well can becharacterized as a cyclic process. As the gas injection rate5 through the gas flow control device begins to increase, the density of the fluid in the production tubing string decreases,which, in turn, results in more réservoir fluid entering thewellbore. This portion of the cycle continues and acceleratesuntil the pressure in the annulus drops, i.e., the supply of10 injection gas in the annulus diminishes. The pressure drop in the annulus results in a decrease in the pressure differentialacross the gas flow control device and, thus, a decrease in therate of gas injection through the gas flow control device andinto the production tubing. As a resuit of the decrease in the15 gas injection rate through the gas flow control device, the density of the fluid in the tubing string increases, causing theproduction pressure, or downstream pressure, to increase, which,in turn, results in less réservoir fluid entering the wellbore.This part of the cycle continues until the pressure in the20 annulus increases sufficiently to where the rate of gas injection through the gas flow control device once again increases.
The differential pressure across the gas flow control deviceis defined as the différence between the injection pressure andthe production pressure. The differential pressure can also belisted as a percentage of the injection pressure. In thiscontext, the injection pressure is also referred to as either theupstream or casing pressure, and the production pressure is alsoreferred to as either the tubing or downstream pressure. 010580 5
Flow instability in continuons-flow gas lift wells occurswhere the gas flow control device allows the gas injection ratethrough the device to fluctuate as a function of the production,or downstream, pressure. The gas injection rate through a prior 5 art square-edged orifice gas flow control device fluctuâtes asa the production, or downstream, pressure fluctuâtes.
Choking at the flowline downstream from the productiontubing string is the accepted industry practice that is used tolessen the effect of the above mentioned factors which cause flow 10 instability. Choking typically increases the average flowingbottom hole pressure in the tubing to be higher than desired.This, in turn, reduces the rate of fluid that is produced fromthe réservoir. To compensate for flowline choking, more gas 75 injection is required. This increase in gas injection adverselyaffects' the efficiency of the gas lift operation because of theincrease in lifting costs and the inefficient use of injection gas.
Fluctuations in the bottom hole tubing pressure cause 20 fluctuations in the rates of gas flowing through the flow controldevice; i.e., with large bottom hole tubing pressure decreases,the gas injection rate through the flow control device increases.This phenomena is largely uncontrollable and unpredictable usingexisting gas flow control devices. 25 The aforementioned fluctuations in tubing pressure may also resuit in problems at the surface. For instance, segregatedflows of oil and gas mixtures can be forced up the productiontubing to the surface, resulting in severe pressure surgesthroughout the tubing and within the surface equipment. This 6 phenomena is commonly referred to as slugging. when the segregated fluids from the well reach the production facility and enter the first stage separator, the particular instantaneous flow rate, or surge, of liquids may exceed the flow capacity of 5 the separator, causing liguid carryover into the gas lines. This j ! can lead to repeated costly shut downs and loss of revenue from i ail wells leading into that particular facility. | î
The average bottom-hole flowing pressure in the tubing *
during unstable flow is significantly higher than during stable I É 10 flow. During slugging, the bottom-hole flowing pressure in the | tubing increases due to the higher density fluid présent in the | tubing string. The pressure increase is further aggravated by | the prior art flow control device because it passes less gas as <the bottom-hole flowing pressure in the tubing increases, thereby • 15 providing less gas into the tubing.
Accordingly, there is a need to provide a gas flow control
J device which increases the production rate of, and stabilizes the l flow of production from, a continuous-flow gas lift well. ί
There is a further need to achieve improved performance with 20 both an improved orifice valve and an improved gas lift valve î that are used as gas flow control devices. ! *
There is a further need to provide a gas flow control device | t having a consistent and predictable gas injection rate. j î
There is also a need to provide a gas flow control device ! f which has a reduced sensitivity to fluctuations in tubing j pressure. €10580 7
There is still a further need to provide a gas flow controldevice whereby the lift gas injection rate can be controlled fromthe surface.
The présent invention overcomes the deficiencies of the5 prior art.
SUMMARY OF THE INVENTION
To address the above-described problems with, anddeficiencies of, the prior art, it is a primary object of theprésent invention to provide a gas flow control device through 10 which a predictable and constant gas injection rate can beestablished, and which overcomes the flow instability that < commonly occurs in gas lift wells. ; It is a further object of the présent invention to provide ‘ an improved gas flow control device whereby the gas injection ? ! 5 rates through the gas flow control device are controllable at thesurface. ï
It is a further object of the présent invention to providea method of increasing the production rate of a continuous-flowgas lift well. 20 It is a further object of the présent invention to provide a method of stabilizing the production from a continuous-flow gas ; lift well. i i It is still a further object of the présent invention to î t provide an improved gas flow control device for injecting gasÙ into a production string whereby the injection gas pressurewithin the flow control device is recovered and frictional lossesthrough the ‘gas flow control device are reduced, thereby 8 establishing critical flow at a lower differential pressureacross the gas flow control device.
It is still a further object of the présent invention toprovide a method of eliminating the effect of tubing pressure on 5 the gas injection rate through a gas flow control device utilizedin a continuous-flow gas lift well.
In an established continuous-flow gas lift System, there arefive major independent variables which affect the instability ofa well and its rate of production, namely, the tubing pressure 10 at the gas flow control device, the casing pressure at the gasflow control device, the gas injection rate through the gas flowcontrol device, the orifice geometry within the gas flow controldevice, and the propensity for, or the ability of, the formation'to produce liquids. It is a primary object of the invention to 15 provide à gas flow control device which reduces the instabilityin the continuous-flow gas lift well by minimizing the effect ofone major variable, the tubing pressure at the gas flow controldevice. Minimizing the effect of tubing pressure is achieved bymeans of controlling three of the remaining major variables, 20 namely the casing pressure, the gas injection rate, and thegeometry within the gas flow control device.
Accordingly, the gas flow control device of the présentinvention Controls the rate at which gas is injected into aproduction string and includes a housing with at least one inletport, at least one outlet port and a nozzle-Venturi orifice. Thenozzle-Venturi orifice, which may also be referred to as acircular-arc-Venturi, is a converging-diverging pathway that ismade of two parts: a nozzle portion and a Venturi tube, or Λ 580 9
Venturi portion, The nozzle portion includes first and secondends, and a flow path therebetween. The nozzle portionconverges, or is progressively restrictive, from the nozzle first 5 end to the nozzle second end. The Venturi portion includes afirst and a second end, and a flow path therebetween. The firstend of the Venturi tube, also referred to as a Venturi forsimplicity, is disposed adjacent to the second end of the nozzleportion. The Venturi portion diverges, or is progressivelylarger, between the Venturi first end and the Venturi second end.The Venturi flow path is aligned with the nozzle flow path toprovide a continuous flow path through the device. Pressurizedgas from the annulus between the casing and production tubing isconstrained to flow through the at least one inlet port, throughthe continuous flow path, through the at least one outlet port,and into the production tubing.
In a preferred embodiment of the invention, the nozzleportion of the gas flow control device includes curvilinearsidewalls extending from the nozzle first end to the nozzle- 20 second end.
In a preferred embodiment of the invention, the diameter ofthe nozzle first end is greater than the diameter of the nozzle ί second end. Further, the diameter of the Venturi first end is
I j equal to the diameter of the nozzle first end and less than the2$ diameter of the Venturi second end.
In a preferred embodiment of the invention, the crossI sectional area of the nozzle first end is greater than the cross j sectional ar'ea of the nozzle second end. The cross sectionalarea of the Venturi first end is equal to the cross sectional 10 area of the nozzle second end and less than the cross sectionalarea of the Venturi second end.
In a preferred emhodiment of the invention, the ratio of thecross sectional area of the nozzle second end to the crosssectional area of the nozzle first end is approximately 0.4.
In a preferred emhodiment of the invention, the ratio of thecross sectional area of the nozzle second end to the cross sectional area of the nozzle first end is less than- 0.4.
In a preferred emhodiment of the invention, the gas flowingthrough the gas flow control device achieves critical flow at adifférentiel pressure of less than 46% of the gas injectionpressure. Here, the differential pressure is the différencebetween the gas injection pressure and the production pressure?
In a preferred emhodiment of the invention, gas flowingthrough the gas flow control device achieves critical flow at adifferential pressure of between approximately 4% and 10% of thegas injection pressure.
In a preferred emhodiment of the invention,’the gas flowingthrough the gas flow control device achieves critical flow at adifferential pressure of between approximately 5% and 46% of thegas injection pressure.
In a preferred emhodiment of the présent invention, gasflowing through the gas flow device achieves critical flow at adifferential pressure of less than 10% of the gas injectionpressure.
In a preferred emhodiment of the invention, the nozzle portion includes curvilinear sidewalls extending from the nozzle 010580 11 first end to the nozzle second end. The sidewalls hâve a radiusof curvature greater than the diameter of the nozzle second end.
In a preferred embodiment of the invention, the nozzleportion includes curvilinear sidewalls extending from the nozzle 5 first end to the nozzle second end. The sidewalls hâve a radiusof curvature equal to about 1.5 to about 2.5 times the diameter of the nozzle second end.
In a preferred embodiment of the invention, the nozzleportion includes curvilinear sidewalls extending from the nozzle 10 first end to the nozzle second end, and the sidewalls hâve aradius of curvature equal to about 1.9 times the diameter of thenozzle second end.
In a preferred embodiment of the invention, the Venturiportion includes Venturi walls that extend from the Venturi first .15 end to the Venturi second end. The Venturi walls form an angleî of about 4 degrees to about 15 degrees with respect to the longitudinal axis of the Venturi flow path.
In a preferred embodiment of the invention, the Venturi portion includes Venturi walls extending from the Venturi firstend to the Venturi second end. The Venturi walls form an angleof about 6 degrees with respect to the longitudinal axis of theVenturi flow path.
In a preferred embodiment of the invention, the Venturiportion includes Venturi sidewalls that are circular in cross 25 section and extend from the Venturi first end to the Venturisecond. ; In accordance with the présent invention, a method of : controlling the rate of gas injected into a production tubing 12 string is provided. The tubing string is positioned within awell and concentrée to casing, forming an annulus therebetween. A gas flow control device is placed within the. well at apredetermined location, the gas flow control device comprising 5 a housing including at least one inlet port and at least oneoutlet port, and an orifice comprising a nozzle portion and aVenturi portion, the nozzle portion including a nozzle first end,a nozzle second end, and a nozzle flow path between the nozzlefirst end and the nozzle second end, the nozzle flowpath 10 converging from the first nozzle end to the second nozzle end,and the Venturi portion including a first end and a second end,and a Venturi flow path therebetween, the Venturi flow pathdiverging from the Venturi first end to the Venturi second end,the Venturi first end being disposed adjacent the nozzle second 15 end, thè Venturi flow path being aligned with the nozzle flowpath to provide a continuous flow path, the gas flow controldevice positioned for transmitting the flow of injected gas fromthe annulus into the production tubing string. Compressed gasis forced into the annulus. The compressed gas is constrained 20 to flow through the gas flow control device to mix the gas withréservoir fluids within the production tubing string, therebyreducing the density of the réservoir fluids. The pressure ofthe gas forced into the annulus is controlled with a pressurecontrol device, thereby increasing the gas injection rate through 25 the gas flow control device by increasing the pressure of the gasin the annulus, and decreasing the gas injection rate through thegas flow control device by decreasing the pressure of the gas inthe annulus. 010580 13
In accordance with the présent invention, a method isprovided for eliminating instability in a production tubingstring of a continuous-flow gas lift well. The production tubingstring is positioned within said well and concentric to casing, 5 said casing and said concentric production tubing string formingan annulus therebetween. A gas flow control device is positionedwithin said well at a predetermined location, said gas flowcontrol device comprising a housing including at least one inletport and at least one outlet port; and an orifice comprising a 10 nozzle portion and a Venturi portion; said nozzle portionincluding a nozzle first end, a nozzle second end, and a nozzleflow path between said nozzle first end and said nozzle secondend, said nozzle flowpath converging from said first nozzle endto said second nozzle end; and said Venturi portion including a 15 first end and a second end, and a Venturi flow path therebetween, I said Venturi flow path diverging from said Venturi first end to
J said Venturi second end, said Venturi first end being disposedadjacent said nozzle second end, said Venturi flow path beingaligned with said nozzle flow path to provide a continuous flow 20 path; said gas flow control device positioned for transmittingthe flow of injected gas from the annulus into the productiontubing string. Compressed gas is forced into the annulus. Thecompressed gas is constrained to flow fhrough said gas flowcontrol device to mix said gas with réservoir fluids within the 25 production tubing string, thereby reducing the density of saidréservoir fluids. The pressure of the gas forced into theannulus is controlled with a pressure control device to achievecritical flow through the gas flow control device, thereby
14 maintaining a constant gas injection rate across said gas flowcontrol device that is independent of the pressure within theproduction tubing string.
In accordance with the présent invention, a method of 5 eliminating instability in continuous-flow gas lift wells isprovided by stabilizing the gas injection rate through the gasflow control device so that the gas injection rate is independentof the typical tubing pressure fluctuations that.occur in acontinuous-flow gas lift well. θ It is conteraplated that fluids, namely both gas and liguids, can be used for the lifting of formation fluids to the surface.Accordingly, while the présent invention refers to "gas lift" and"gas flow control devices," it is contemplated that fluids,,having relatively lower density than the formation fluids to be > lifted, can be injected through the flow control device into theproduction tubing to decrease the density of the mixture toimprove lift.
The foregoing has outlined the features and technicaladvantages of the présent invention so that those skilled in the 1 art may better understand the detailed description of theinvention that follows. Features and advantages of the inventionthat are described above and hereinafter form the subject of thedaims of the invention. Those skilled in the art shouldappreciate that they may readily use the conception and thespécifie embodiment disclosed as a basis for modifying ordesigning other structures for carrying out the same purposes ofthe présent invention. 15 010580
In order that the invention may be more fullyunderstood, embodiraents thereof (and the prior art) willnow be described by way of illustration only, with referenceto the accompanying drawings, wherein: 5 FIG. 1 shows a graph which illustrâtes orifice gas injection rate performance in a typical, prior art highpressure gas lift System. The graph is a plot of gas flowrate (ordinate) and tubing pressure in psi (abscissa), wherethe casing pressure is held constant at 1600 psi. The 10 région A is the critical flow régime. FIG. 2 shows a graph which illustrâtes orifice gas injection rate performance in a typical, prior art lowpressure gas lift system. The graph is a plot of gas flowrate (ordinate) and tubing pressure in psi (abscissa), where S the casing pressure is held constant at 1000 psi. The région A is the critical flow régime. FIG. 3 shows a graph which illustrâtes the desiredgas injection rate performance in a gas flow control deviceto eliminate instability in a continuous-flow gas lift well. 20 The graph is a plot of gas flow rate (ordinate) and tubing pressure in psi (abscissa), where the casing pressure isheld constant at 1000 psi. The région A is the criticalflow régime. FIG. 4 illustrâtes a cross-sectional, side- 25 elevational, diagrammatic view of the environment of a gas injection control device; FIG. 5 illustrâtes a cross-sectional view of astandard orifice gas injection control device having asquare-edged orifice; FIGS. 6A and 6B illustrate a cross-sectional viewof an exemplary orifice gas flow control device of theprésent invention including a nozzle-Venturi orifice; FIG. 6C illustrâtes a cross-sectional view of anozzle-Venturi orifice assembly that is included within a 35 gas flow control device of the présent invention; FIGS. 7A and 7B illustrate a cross-sectional view 010580 - 16 - of an exemplary gas lift valve of the présent inventionincluding a nozzle-Venturi orifice; FIG. 8 shows a graph which illustrâtes the dynamicperformance of an exemplary nozzle-Venturi gas flow control 5 device of the présent invention at three separate upstream pressures, and also provides a comparison to the dynamicperformance of a prior art gas flow control device employinga square-edged orifice, shown in FIG. 2. The graph is plotsof gas injection rate (MCF/D) (ordinate) and downstream 10 pressure in psi (abscissa) at upstream pressures of 400 psi (line D), 900 psi (line E), 900 psi (line F) and 1400 psi(1ine G) . FIG. 9 shows a graph which compares a pressureprofile for a square-edged orifice housed in a prior art gas 15 flow control device and a pressure profile for an exemplary nozzle-Venturi orifice housed in a gas flow control deviceof the présent invention. In the graph, the left-handordinate is the upstream pressure in psi, and the right-handordinate is the downstream pressure in psi. The abscissa is 20 the distance. Line P is prior art and line Q is according to the invention.
To illustrate the influence of a prior art square-edged orifice used in a gas flow control device, FIG. 1shows a typical performance thereof. The casing pressure of 25 the wellbore, at the depth of gas injection through the device, is a constant 1600 psig, and the desired tubingpressure is 1450 psig. The casing pressure is defined asthe upstream pressure of. the orifice, and the tubingpressure is defined as the downstream pressure of the 30 orifice. As the tubing pressure increases, the gas injection rate through the orifice decreases. Conversely,as the tubing pressure decreases, the gas injection rate
(H 0580 17 FIG. 2 also illustrâtes the effect of the prior art orificeused in a gas flow control device. In this illustration, theprior art orifice is provided in an environment at lower casingand tubing pressures of 1000 psig and 850 psig, respectively. 5 Typically the desired pressure drop across the prior art orifice is between 100 and 200 psi. However, at pressure dropsof 150 to 200 psi, high injection pressures are required,reSulting in high gas compression costs. Where the pressure dropis under 100 psi, the gas injection rate becomes more 10 unpredictable. Thus, a pressure drop of under 100 psi is usuallynot considered due to the lack of accurate data and the potentialof designing an inefficient gas lift System. Accordingly, apressure drop in excess of 100 psi across the prior art orificeis typically desired and used as a safety factor in designing the 15 gas lift System.
As evidenced by FIGS. 1 and 2, and as known in the art, thegas injection rate through the prior art orifice continues toincrease until the tubing pressure déclinés to a value that isabout 54% of the constant casing pressure. Thereafter, the gas 20 injection rate through the orifice remains constant as the tubingpressure is lowered,. The industry properly understands thatcritical flow through the prior art square-edged orifice is t , ! established when the tubing pressure is about 54% of the casing i ! pressure. When the tubing pressure drops to the critical flow 25 régime (i.e., the tubing pressure is 54% of the casing pressure) , the gas injection rate through the orifice remains constant and independent of the tubing pressure. 18
Establishing the critical flow régime through the orificeacts to eliminate flow instability. For example, for the welloperating at a tubing pressure of 1450 psig, establishingcritical flow through the prior art, square-edged gas flow 5 control device could be established by increasing the casingpressure from 1600 psig to 2700 psig or above. However, creatingsuch a high pressure drop across the orifice is not economicallyfeasible due to the additional cost in gas compression.Furthermore, this practice is not praccical due co the increased W likelihood of mechanical problems.
It is an object of the présent invention to provide an orifice valve that seeks to reduce and effectively eliminate flowinstability under normal conditions. Specifically, it is anobject of the présent invention to provide a flow control device 15 which has the performance characteristics that are illustratedin FIG. 3, where the critical flow régime and a constantinjection rate are reached when the tubing pressure isapproximately 90%-95% or less of the casing pressure, as opposedto the industry standard of 54% for the prior art, square-edged 20 orifice. FIG. 3 is a graph which illustrâtes the desired flow rateperformance in a gas control device of the présent inventionwhere the constant casing pressure is 1000 psig. Therefore, ifthe tubing pressure déclinés below approximately 900 psig the 25 gas injection rate through the control device remains fixed.
Thus, for a typical pressure drop of 1OQ to 200 psi across the gas flow control device, a constant gas injection rate can be achieved resulting in a stabilized well and improved économies. 19
Another advantage of the orifice valve of the présentinvention is the capability of controlling the injection gas rate ! through the gas flow control device, without causing instability, i by simply controlling the surface injection pressure. Typically, S t'nis also has the effect of controlling the production rate ofthe liquids from the wellbore. Thus, by using the orifice valveof the présent invention downhole, the operator can increase the pressure of the gas at the surface to increase the injectionpressure (casing or upstream pressure) at the gas flow controlθ device, which, in turn, increases the differential pressureacross the gas flow control device and, therefore, the rate of
I • gas injection through the gas flow control device. This, in! turn, decreases the density of the fluid in the production tubingstring, which allows more fluids from the réservoir to enter theiS wellbore and be produced. Increasing the pressure of the injected gas increases the density of the gas such that, for thesame restriction in the gas flow control device, the gas injection rate is increased.
The présent invention is employed in an exemplary 20 environment·that is shown in FIG. 4. A gas lift well System 10 extends from above „ground G, where System 10 is connectéd to apressurized gas source (not shown) and to petroleum recoveryequipment (not shown), and a subterranean petroleum réservoir P. • Petroleum rises in production tubing 12. Pressurized gas is
I 2$ introduced into annulus 14, which exists between the productiontubing 12 and outer Steel casing 16. Annulus 14 is sealed at thebottom of casing 16 by a packer 18. Pressurized gas is suppliedfrom a source, such as a compressor (not shown) . The gas 01058 Ο 25 20 pressure in the annulus 14 is regulated by a pressure controldevice 9, namely either an adjustable choke or a r'egulator, atthe surface. The pressurized gas, represented by arrows 20,flows from the compressor, through the pressure control device 5 9, and through the annulus 14 into tubing 12 via a gas flow control device 22. Gas injected into production tubing 12decreases the density of petroleum rising to the surface andenables natural réservoir pressure to maintain this flow. Thepressure control device 9 is utilized at the surface to control 10 the pressure in the annulus 14, which, in turn, establishës theinjection pressure (also referred to as the casing pressure orupstream pressure) at the gas flow control device 22, thedifferential pressure across the gas flow control device, and,thus, the rate of injection through the gas flow control device 15 22.
While the pressure control device 9 is shown at the surfacein FIG. 4, it is contemplated that a pressure control device canbe installed within the annulus at a depth more proximate the gasflow control device 22. In this situation, à certain amount of 20 annulus is isolated to form a chamber for injection gas wherebythe gas to be injected is delivered to the chamber, and the gaspressure regulated by the pressure control device which, in turn,is controlled from the surface via a hydraulic or electriccontrol line.
Furthermorer a single well bore will often times intersecta number of producing formations and, for économie reasons, theseformations,' referred to as production zones, are isolated byinstalling packoff devices so that the individual zones can be 010580 21 produced independently. A plurality of tubing strings are thusemployed to produce the spécifie formations. The limitations ofthe prior art gas flow control device, namely its dynamicperformance, exacerbâtes the flow instability in well complétionswith a plurality of production tubing strings. In such a well,instability is more likely to occur in each of the individualproduction tubing strings of the gas lift system because thecommon annulus supplies the injection gas to each- gas flowcontrol device and the injection rate through each prior art gasflow control device is completely unpredictable and independent.The présent invention provides a constant gas injection rate intoeach tubing string and will, therefore, diminish the flowinstability common in wells having a plurality of productionstrings. A prior art gas flow control device 22 having a square-edgedorifice is illustrated in FIG. 5. The direction of the gas flowthrough the gas flow control device is indicated by arrows 26.Pressurized gas at injection pressure enters the prior art flowcontrol device 22 through inlets 24 and flows through a square-edged orifice 29, containing passage 29a and seal 29b. Gas thenpasses through passageway 28a of an orifice holder 28 and pastthe check valve 30. Gas is then discharged through outlet 32 atthe nose end 21, at production pressure, and passes intoproduction tubing 12 (FIG. 4) . The passage 29a and passageway28a typically hâve circular cross-sections, when consideringthose cross-sections are taken along planes perpendicular to thelongitudinal axis of the gas flow control device. 22 010580 FIGS. 6A and 6B illustrâtes an exemplary gas flow controldevice 60 of the présent invention. The gas flow control device 60 has generally the same dimensions and components as those ofthe prior art gas flow control device 22 (illustrated in FIG. 5) , 5 including a dummy tail section 62, inlet ports 54 and nose end 61 with a check valve 65 and outlet ports 64; the check valve 65includes a dart 67, a spring 69, and a check seal 71. However,the gas flow control device 60 of the présent invention includesa nozzle-Venturi orifice 34, instead of thé square-edged orifice 10 29 found in the prior art.
The direction of the gas flow through the gas flow controldevice of the présent invention is indicated by arrows. 26.Pressurized gas at injection pressure (casing pressure) entersthe inlet ports 54 and flows through the nozzle-Venturi orifice34 and past the check valve 65. The gas is then dischargedthrough the outlet ports 64, at production pressure (downstreampressure or tubing pressure), and passes into the productiontubing.
An exemplary nozzle-Venturi orifice 34 is illustrated indetail in FIG. 6C and may comprise, for example, a circular arcVenturi, and includes a nozzle portion 34a and a Venturi portion Ί. 34b. Nozzle portion 34a lies above a throat 36, and Venturiportion 34b lies below throat 36.
Nozzle portion 34a includes sidewalls 38 which offer minimal25 résistance to the flow of fluid (gas or liquid) as the fluidapproaches throat 36. Sidewalls 3 8 are progressively restrictiveto throat 36. The cross-sectional area of throat 36 is less than 23 010580 the cross-sectional area of nozzle portion 34a and Venturi portion 34b.
Sidewalls 3 8 are curved, or curvilinear, such that theslopes of tangent lines méasured at each point along the curve42 of nozzle portion 34a, slope being considered in themathematical sense, are greater at tangent points approachingthroat 36. Also, the curvature of nozzle portion 34a is suchthat there is a radius of curvature 44 which is greater than adiameter 4 6 of the throat 3 6 by a factor between 1.5 and 2.5, apreferred value being 1.9.
Below throat 36, Venturi 34b increases in cross-sectionalarea at a rate such that vertical walls 48 thereof form an angle50 to a vertical, or longitudinal, direction 52. Angle 50 lieswithin a range of four to fifteen degrees, a preferred valuebeing six degrees.
The ratio of the cross-sectional area at the diameter 46 ofthroat 36 to the cross-sectional area at the widest point ofnozzle portion 34a, as measured at the mouth 54, is egual to orless than 0.4.
Cross-sections of nozzle-Venturi orifice 34, includingcross-sections of the nozzle portion and the Venturi portion,considering those cross-sections taken along planes perpendicularto the Venturi axis, are generally represented as being circular.This is due to the expectation that manufacturing processes forforming nozzle-Venturi orifice 34, or for forming a die or moldto manufacture the same will be centered around cutting arotating piece of stock, as exemplified by a lathe operation.However, it is contemplated that other manufacturing processés 010580 24 are possible, and that other geometries for the cross-sectionsof the nozzle portion and Venturi portion are thus possible. Forexample, corresponding cross-sections of nozzle-Venturi orifice34 may be rectangular, elliptical, polygonal, hypergeometricelliptical, or even of other configurations.
Gas flowing within nozzle portion 34a of nozzle-Venturiorifice 34 flows at a high velocity and a low pressure. The gasflowing through Venturi portion 24b decreases in'velocity andincreases in pressure such that the gas exiting the valve 22 haspressure recovered with a minimal amount of energy or pressureloss.
For optimum performance, the nozzle portion 34a and theVenturi portion 34b of the nozzle-Venturi orifice 34 should bemade of low-friction materials, such as ceramics, highly polishedmetals and plastics. Thus, the frictional losses across thenozzle-Venturi are minimized. The material used in the orificevalve that was tested was made of 17-ph stainless. FIGS. 7A and 7B illustrate another preferred embodiment ofa gas flow control device of the présent invention, where anozzle-Venturi orifice is housed within an artificial lift valve,also commonly referred to as a gas lift valve. Referring now toFIGS. 7A and 7B, an exemplary artificial lift valve 200 isillustrated in detail,, which is représentative of artificial liftvalves enclosed within a side pocket mandrel included inproduction tubing. It should be understood that theconfiguration described for this artificial lift valve is forpurposes of explanation only and is not intended to limit theinvention to a particular construction of artificial lift valve. 25 010580
Althcugh the construction and general operation of artificiallift valves and their components are well known, this will bedescribed in some detail to provide background and to aid thereader in an understanding of the invention. 5 As illustrated in FIGS. 7A-7B, in a preferred embodiment of the invention the artificial lift valve 200 is made up of a valvehousing, indicated generally at 202, which is shaped and sizedto résidé within the bore 204 of a side pocket màndrel inproduction tubing. It is noted that the bore 204 of the side G pocket mandrel includes a number of generally radially outwardfacing latéral ports 206 which permit fluid communication betweenthe interior of the bore 204 and the wellbore annulus 14 (asshown in FIG. 4) . The lower portion of the bore 204 alsofeatures one or more radially inward-facing apertures (not shown) S which will permit fluid communication between the interior of thebore 204 and the flowbore within the tubing string 12 (as shownin FIG. 4) . ' Side pocket mandrel designs of this nature arewidely known.
The valve housing 202 itself includes an upper dôme sub 2082O which is threadedly connected at 210 to a bellows housing 212below. The upper end of the upper dôme sub 208 features athreaded portion 214 which permits the valve housing 202 to beengaged with a latchable member 216 (latchable portion not shown)for secure fastening of the valve 200 within the bore 204 of the 25 side pocket mandrel. The bellows housing 212 is threadedlyengaged at 218 at its lower end to a connector sub 220 which, inturn, is threadedly attached to a main valve housing 224. Thei main valve housing 224 carries an outer annular elastomeric t ' i
I 010580 26 oacking 226 which, when the valve 200 is disposed within the bore204, effects a fluid seal against the inner surface of the bore204. The main valve housing 224 also présents one or morelatéral ports 228 which permit fluid transmission through the 5 main valve housing 224. A valve seat retainer 23 0 is affixed bythreaded connection 232 to the lower end of the main valvehousing 224. A nozzle-Venturi housing 234 is threaded at 236 tothe valve seat retainer 230 and carries an outer annular packing238 about its circumference which, when the valve 200 is disposedwithin the bore 204, effects a fluid seal against'· the innersurface of the bore 204. Finally, a tapered nose piece 24 0 isthreaded at 242 to the nozzle-Venturi housing 234. A nitrogen charged chamber or "dôme" chamber 244 is locatednear the top of the valve 200. A fill valve 246 and a removable 15 threaded-main seal plug 248 are located thereabove.
Below the dôme chamber 244, a main valve assembly 250 is reciprocally disposed within a bellows chamber 252 and a mainvalve chamber 253 which is defined by the main valve housing 224 .A reduced diameter neck 254 is located at the upper portion of 20 the bellows chamber 252 and séparâtes the bellows chamber 252from the dôme chamber 244 above. The main valve assembly 250 ismade up of upper, central and lower stem sections 256, 258 and260, respectively, which are threadedly connected to each otherin an end-to-end relation as shown. The main valve assembly 250 25 also features a valve plug 262 with a downwârdly presentedspherically-shaped closure member, or bail, 264 threadedlyengaged to.the bottom of the lower stem section 260. Below the
1C 15 25 010580 27 valve plug 262, a valve seat 266 is maintained in place withinthe main valve chamber 253 by the valve seat retainer 230.
The upper stem section 256 of the main valve assembly 250is disposed through the reduced diameter neck 254 . A sériés ofsmall annuler baffles 268 circumferentially surround portions ofthe upper stem section 256 which are sized and shaped to receivesmall amounts of viscous fluid and thus, during movement of, themain valve assembly 250, serve to dampen vibration.
Within the bellows chamber 252, and generally radiallysurrounding the central stem section 258, is an accordion-likebellows 270 which will axially extend and retract within thebellows chamber 252. The bellows 270 is made of a flexible,waterproof material. A compression spring 255 is located withinthe bellows chamber above the main valve assembly 250 to limitexcessive upward travel of the main valve assembly 250 andovercompression of the bellows 270.
Two mutually opposing fluid pressure conducting passages,separated by the bellows 270, are used to control the opening andclosing of the main valve assembly 250 due to the fluid sealscreated between the bore 204 of the surrounding side pocketmandrel and packings 226 and 238. The first pressure conductingpassage, generally at 272, includes the dôme chamber 244 and thebellows chamber 252. Pressure within this first pressureconducting passage is maintained radially outside of the bellows270. The first pressure conducting passage 272 is pressurizedprior to disposai of the artificial lift valve 200 into thewellbore. The bellows chamber 252 is filled with a viscous fluiduntil the fluid covers the reduced diameter neck 254 and reaches 010580 28 ' a level 274 within the dôme chamber 244. The dôme chamber 244is then charged with nitrogen through the fill valve 246 priorto being run into the wellbore so as to provide a fluid springby removing the plug 248 and forcing nitrogen through the fill 5 valve 246 under pressure.
The second pressure conducting passage 276 includes the main valve chamber 253. Fluid and fluid pressure from the wellboreannulus 320 enters the main valve chamber via ports 228. Fluidentering the main valve chamber 253 is maintained radially within 10 the bellows 270. Résultant pressure within the second pressure conductingpassage 276 acts upon the main valve assembly 250 in counterpointto that provided by the fluid spring of the first pressureconducting passage 272. When the pressure within the second 15 pressure conducting passage 276 overcomes that provided by thefluid spring, the closure member 264 (bail) will be lifted fromthe seat 266 to permit flow of fluid entering ports 228 to flowdownward past the seat 266 and into and through the nozzle-Venturi orifice 34 defined within the nozzle-Venturi housing 234. 20 The nozzle-Venturi orifice 34 (as shown in detail in FIG. 6C)extends downward to and past a check valve assembly 280 at thelower end of the valve 200. Therefore, fluid entering thenozzle-Venturi orifice 34 downward past the valve seat 266 canmove downward through the nozzle-Venturi orifice 34, out of the 25 lower end of the valve 200 and into the lower portion of the bore204 where it may enter the production tubing string throughapertures in the mandrel below. Ο >O __... ‘-'5 010580 29 A nozzle-Venturi orifice 34 is maintained within the nozzle-Venturi housing 234 and aligned so that the gas will passdownward through the nozzle-Venturi orifice 34 and out of thelower end of the valve 200. The arrangement of the nozzle-5 Venturi is best seen by referring once again to FIG. 6C.
In a typical gas lift valve, the combination of the movablestem and seat defines a pressure-adjustable orifice and, in priorart gas lift valves, the larger the bail and seat size, the morethat the tubing pressure affects the opening and closing of thevalve. Fluctuating tubing pressures can cause the valve to openand close errâtically, causing erratic injection rates that mayfurther aggravate the fluctuating tubing pressures.Additionally, prior art gas lift valves are subject to ail of thelimitations described above that are related to pressure recoverythrough- the assembly. In comparison, a gas lift valve of theprésent invention will hâve improved pressure recovery and anincreased gas injection rate due to lower frictional lossesacross the gas lift valve, thereby increasing the efficiency ofthe gas lift System. Furthermore, the gas lift valve of theprésent invention will also be less susceptible to fluctuationsin the injection rate. In the gas lift valve of the présentinvention, a converging-diverging, or nozzle-Venturi, orificedownstream of the bail and seat will resuit in a constantpressure below the bail and seat and injection of the gas at aconstant critical flow rate which is determined by the physicalgeometry of the valve and orifice. Compared to the prior art gaslift valve, a'gas lift valve of the présent invention will hâve 30 010580 a lower differential pressure at which critical flow across thegas lift valve will occur. FIG. 8 is a graph which illustrâtes test resuit s showing thedynamic performance of an exemplary nozzle-Venturi orifice gasflow control device of the présent invention, as shown in FIGS.6A and 6B, and the dynamic performance of a conventional gas flowcontrol device having a square-edged orifice, as shown in FIG.5. A gas flow control device of the présent invention, whichincluded a nozzle-Venturi orifice 34 having a throat diameter(item 46 of · FIG. 60 of 0.332 inches, was tested at threeseparate constant upstream (injection or casing) pressures,namely 400 psi, 900 psi and 1400 psi. Further, test results ofthe dynamic performance of the injection gas flow control deviceof the présent invention having the présent nozzle-Venturiorifice-34 at a constant upstream pressure of 900 psi, which isrepresented by the curve including point A, is compared to testresults of the dynamic performance of a prior art injection gasflow control device, namely a standard orifice valve, having asquare-edged orifice 29 (as shown in FIG. 5). The test results for the prior art, square-edged orifice valve are indicated bythe curve including point B. Both of the gas flow controldevices had the same diameter of 0.322 inches, and both weretested at a. constant upstream pressure of 900 psi. The sonie(critical) flow rate régime is that portion of each curve thatis horizontal. By operating a gas injection flow control devicein the sonie 'flow régime, a stable gas lift System is achieved.It is readily appreciated that the broad fiat portion between thevertical axis and point A, representing stable performance of a 31 010580 gas flow -control device of the présent invention including anozzle-Venturi orifice 34, is much wider than the correspondingfiat portion between the vertical axis and point B, representingstable performance of a prior art gas control device, namely aconventional orifice valve including a square-edged orifice.Moreover, at similar production pressures, more gas flows througha gas flow control device with a nozzle-Venturi orifice 34 thanthrough a gas flow control device with a square-edged orificehaving the same throat size.
Listed below are the test results achieved for various-sizedflow control devices of the présent invention, namely orificevalves including certain sized nozzle-Venturi orifices, atvarious upstream (injection) pressures. The results listed arethe downstream pressures, in terms of percentages of the upstreampressure, at which critical flow across the flow control deviceswas reached, which is designated as Point A in FIG. 8.Alternatively, the resulting differential pressure at whichcritical flow across the flow control devices was reached in thetests is readily calculated as a percentage of the injectionpressure by subtracting a given downstream pressure, listed asa percentage of the injection pressure, from 100%.
Downstream Pressure As A
Percentage of Injection PressureAt Which Critical Flow Is Reached
Upstream (Injection)
Pressure (PSIG) 32 010580 400 900 1400 92.8% 92.8% 94.5% 94.5% 94.7% 94.7% 95.2% 92.8% 95.6% 93.2% 93.4% 92.3% 95.1% 90.1% 92.2% 0.204 0.266 0.314 0.326 0.332 S Orifice Throat Size In Inches (See Item 46, FIG. 60
The gas flow control device of the présent ,inventionincluding the nozzle-Venturi orifice 34 provides for a lowerpressure drop in achieving sonie, or critical, flow. Square-edged orifices typically require a pressure drop of 46 percentof upstream pressure to produce sonie velocity flow therethrough.In contrast, as illustrated by the table above, the gas controldevice of the présent invention including a nozzle-Venturiorifice typically requires less than a ten percent pressure dropof upstream pressure, and often less than 6 percent pressure dropof upstream pressure to achieve critical flow. The ability ofthe gas flow control device to achieve critical flow at such alow pressure drop causes the gas injection rate through the gasflow control device to be generally independent of the tubing 20 pressure, effectively éliminâting flow instability as described above. In addition to the gas injection rate being independentof the production tubing pressure, the gas injection rate throughthe gas flow control device can be controlled by adjusting theinjection .pressure at the surface, which acts to increase or 33 010580 decrease the pressure and the density of the injected gas in theannulus.
In order to further explain the différence in the flowperformance of a prior art gas flow control device having a S square-edged orifice and the flow performance of an exemplary gasflow control device of the présent invention having a nozzle-Venturi orifice, FIG. 9 illustrâtes the pressure profiles of eachdevice. The upper portion of.FIG. 9 shows an overlay of thecross-sectional views of the two devices taken along the flow K path of the injected gas, with the dotted line representing thea square-edged orifice and the solid line with hatchingrepresenting the nozzle-Venturi orifice. The arrow in the upperportion of FIG. 9 indicates the direction of the flow of injectedgas through the two devices. 1h The lower portion of FIG. 9 is a graph that plots the gas pressure within the devices as a function of the position of thegas as it flows through the devices. The dotted line representsthe pressure profile for the square-edged orifice of the priorart gas flow control device and the solid line represents the 20 pressure profile of the nozzle-Venturi orifice of the gas flowcontrol device of the présent invention. For an injectionpressure of 1000 psia, the sonie flow at the throat (the criticalflow régime) is established for both devices. For air flow this ! corresponds to a pressure of approximately 540 psia at the 25 throat. This flow condition resuit s in the maximum mass flowrate as indicated by points A and B in figure 8, for the nozzle-Venturi and the square-edged orifice respectively. After thethroat, where the greatest velocity and the lowest pressure 010580 25 34 occurs, the pressure increases (recovers) and the velocitydecreases in the direction of the flow. For the nozzle-Venturia maximum pressure of 900 psia is attained at the exit of thedivergent section. The pressure recovery for the square-edged 5 orifice is only slight, resulting in the exit pressure of, forexample, 600 psia. Therefore, the sonie flow for a nozzle-Venturi flow control device can be achieved at a much lowerpressure differential resulting in a higher exit or· productionpressure, as comparée to a square-edged orifice flow controldevice.
It therefore can be seen that the présent nozzle-Venturiprovides for a gas flow control device that minimizes wellinstabilities by extending the critical flow rate régime, and by,rendering lift operations independent of production pressure.The gas flow control device of the présent invention thus actsto stabilize the flow of production in the production tubing.
The gas flow control device of the présent inventionachieves critical flow, that point where any additional pressuredrop in the tubing will not resuit in an increase of flow thrqugh 20 the valve, .with a pressure drop of approximately 5% of theupstream pressure or greater. Because stable flow through thegas lift valve is established with such a minimum pressure drop,there is no need to hâve a finite control of the injection gas on the surface.
Although the présent invention and its advantages hâve beendescribed in detail, those skilled in the art should understandthat they can make various changes, substitutions and alterations .
Claims (10)
1. A gas lift valve (200) for injecting pressurized gas into a productionstring (12) comprising: a housing (202) adapted to be disposed within saidproduction string (12) and including at least one inlet port (206) and at least oneoutlet port; and an orifice (34) disposed within the housing (202) and comprisinga nozzle portion (34a) and a Venturi portion (34b); said nozzle portion (34a)including a nozzle first end, a nozzle second end, and a nozzle flow path betweensaid nozzle first end and said nozzle second end, said nozzle flow path convergingfrom said nozzle first end to said nozzle second end; and said Venturi portion(34b) including a first end and a second end, and a Venturi flow path therebetween,said Venturi flow path diverging from said Venturi first end to said Venturi secondend, said Venturi first end being disposed adjacent said nozzle second end, saidVenturi flow path being aligned with said nozzle flow path to provide a continuousflow path; whereby, during operation of said gas lift valve (200), said pressurizedgas flows into the or each inlet port (206) of said gas lift valve (200), is decreasedin pressure through said nozzle portion (34a) and increased in said pressurethrough said Venturi portion (34b), and flows out through said at least one outletport into said production string (12) with said pressure substantially recoveredthrough said gas lift valve (200).
2. A gas lift valve (200) for injecting pressurised gas into a productionstring (12), comprising: a housing (202) adapted to be disposed within saidproduction string (12) and including at least one inlet port (206) and at least oneoutlet port; and an orifice (34) disposed within the housing (202) and comprisinga nozzle portion (34a) and a Venturi portion (34b); said nozzle portion (34a)including a nozzle first end, a nozzle second end, and a nozzle flow path betweensaid nozzle first end and said nozzle second end, said nozzle flow path convergingfrom said nozzle first end to said nozzle second end; and said Venturi portion(34b) including a first end and a second end, and a Venturi flow path therebetween,said Venturi flow path diverging from said Venturi first end to said Venturi second 010580 -36- said Venturi first endbeing disposed adjacent said nozzle second end, said Venturiflow path being aligned with said nozzle flow path to provide a continuons flowpath; whereby, during an operation of said gas lift valve (200), said pressurized gasflows into said at least one inlet port (206) of said gas lift valve, is decreased in 5 pressure through said nozzle portion (34a) and increased in said pressure through said Venturi portion (34b), and flows out through said at least one outlet port intosaid production string (12) at a production pressure in said production string (12).
3. A gas lift valve (200) according to claim 1 or 2, wherein said nozzleportion (34a) includes curvilinear sidewalls (38) extending from said nozzle firstend to said nozzle second end.
4. A gas lift valve (200) according to claim 1,2 or 3, wherein in use gasflowing therethrough achieves critical flow across the valve at a differentialpressure drop across said gas lift valve (200) of between 5% and 46% of the gasinjection pressure. 15
5, A gas lift valve (200) according to any preceding claim, wherein in use gas flowing therethrough achieves critical flow across the valve at a differentialpressure drop across said gas lift valve (200) of less than 10% of the gas injectionpressure.
6. A gas lift valve (200) according to any preceding claim, further 2θ comprising a throat (36) interposed between said nozzle second end and said Venturi first end.
7. A method of controlling the rate of gas injected into a productionstring (12) positioned within a continuous-flow gas lift well drilled into theearth and lined with casing (16), said production string (12) being concentric to 25 said casing (16), said casing (16) and said concentric production string (12) forming an annulus (14) therebetween, said method comprising the steps of: 010580 -37- placing a gas flow control device (60) within said well at a predetermined location,said gas flow control device (60) comprising a housing including at least one inletport (54) and at least one outlet port (64); and an orifice (34) disposed within thehousing and comprising a nozzle portion (34a) and a Venturi portion (34b); said 5 nozzle portion (34a) including a nozzle first end, a nozzle second end, and a nozzle flow path between said nozzle first end and said nozzle second end, said nozzleflow path converging from said nozzle first end to said nozzle second end; and saidVenturi portion (34b) including a first end and a second end, and a Venturi flowpath therebetween, said Venturi flow path diverging from said Venturi first end toθ said Venturi second end, said Venturi first end being disposed adjacent said nozzle second end, said Venturi flow path being aligned with said nozzle flow path toprovide a continuous flow path; said gas flow control device (60) positioned fortransmitting the flow of injected gas from the annulus (14) into the productionstring (12), whereby a pressure of said injected gas is decreased through said 15 nozzle portion (34a) and substantially recovered through said gas flow controldevice (60) during an operation of said gas flow control device (60); forcingcompressed gas into the annulus (14); constraining the compressed gas to flowthrough said gas flow control device (60) to mix said gas with réservoir fluids within the production string (12), thereby reducing the density of said réservoir 2fl fluids; and controlling the pressure of the gas forced into the annulus (14) with apressure control device (9), thereby increasing the gas injection rate through thegas flow control device (60) by increasing the pressure of the gas in the annulus(14), and decreasing the gas injection rate through the gas flow control device (60)by decreasing the pressure of the gas in the annulus (14). 25
8. A method of eliminating instability in a production string (12) positioned within a continuous-flow gas lift well drilled into the earth and lined with casing(16) said production string (12) being concentric to said casing (16), said casing(16) and said concentric production string (12) forming an annulus (14)therebetween, said method comprising the steps of: placing a gas flow controldevice (60) within said well at a predetermined location, said gas flow control 010580 -38- device (60) comprising a housing including at least one inlet port (54) and at leastone outlet port (64); and an orifice (34) disposed within the housing andcomprising a nozzle portion (34a) and a Venturi portion (34b); said nozzle portion(34a) including a nozzle first end, a nozzle second end, and a nozzle flow path 5 between said nozzle first end and said nozzle second end, said nozzle flow path converging from said nozzle first end to said nozzle second end; and said Venturiportion (34b) including a first and a second end, and a Venturi flow paththerebetween, said Venturi flow path diverging from said Venturi first end to saidVenturi second end, said Venturi first end being disposed adjacent said nozzle θ second end, said Venturi flow path being aligned with said nozzle flow path to provide a continuous flow path; said gas flow control device (60) positioned fortransmitting the flow of injected gas from the annulus (14) into the productionstring (12), whereby a pressure of said injected gas is decreased through saidnozzle portion (34a) and substantially recovered through said gas flow control 5 device (60) during an operation of said gas flow control device (60); forcing compressed gas into the annulus (14); constraining the compressed gas to flowthrough said gas flow control device (60) to mix said gas with réservoir fluidswithin the production string (12), thereby reducing the density of said réservoirfluids; and controlling the pressure of the gas forced into the annulus (14) with a θ pressure control device (9) to achieve critical flow through the gas flow control device (60), thereby maintaining a constant gas injection rate across said gas flowcontrol device (60) that is independent of the pressure within the production string(12).
9. A method according to claim 7 or 8, wherein said gas constrained to flow through said gas flow control device (60) achieves critical flow across said gas flow ‘5 control device (60) at a differential pressure of less than 46% of the pressure within said annulus (14). 010580 - 39 -
10. A method according to claim 9, wherein said gas constrained to flowthrough said gas flow control device (60) achieves critical flow across said gas flowcontrol device (60) at a differential pressure of less than 10% of the pressure withinsaid annulus (14).
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US30166194A | 1994-09-07 | 1994-09-07 | |
| US43403795A | 1995-05-02 | 1995-05-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| OA10580A true OA10580A (en) | 2002-06-19 |
Family
ID=26972527
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| OA60825A OA10580A (en) | 1994-09-07 | 1996-05-06 | Gas lift flow control device |
Country Status (12)
| Country | Link |
|---|---|
| EP (1) | EP0752049B1 (en) |
| AT (1) | ATE197629T1 (en) |
| AU (1) | AU708875C (en) |
| BR (1) | BR9506382A (en) |
| CA (1) | CA2175928C (en) |
| DE (1) | DE69519425D1 (en) |
| MX (1) | MX9601696A (en) |
| MY (1) | MY115179A (en) |
| NO (1) | NO311449B1 (en) |
| NZ (1) | NZ292221A (en) |
| OA (1) | OA10580A (en) |
| WO (1) | WO1996007813A1 (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BR9300292A (en) | 1993-01-27 | 1994-08-16 | Petroleo Brasileiro Sa | Improvement in the case of orifice valves |
| RU2124626C1 (en) * | 1998-06-26 | 1999-01-10 | Научно-техническая ассоциация Восточной нефтяной компании | Well completion method |
| WO2002014798A1 (en) * | 2000-08-15 | 2002-02-21 | Vladislav Petrovich Starikov | Gas flow meter |
| BR0004685B1 (en) * | 2000-10-05 | 2009-01-13 | Method and device for stabilizing the production of oil wells. | |
| US7389684B2 (en) | 2005-11-03 | 2008-06-24 | Roy Jude B | Gas lift flow surveillance device |
| CN110541686B (en) * | 2018-05-28 | 2021-11-30 | 中国石油天然气股份有限公司 | One-way flow tool and tubing |
| CN111042768A (en) * | 2018-10-12 | 2020-04-21 | 中国石油化工股份有限公司 | Injection device |
| WO2021127767A1 (en) * | 2019-12-27 | 2021-07-01 | Petróleo Brasileiro S.A. - Petrobras | Concentric mandrel for intermittent gas lift with accumulation chamber |
| TW202305989A (en) | 2021-06-21 | 2023-02-01 | 荷蘭商Ａｓｍ Ｉｐ私人控股有限公司 | Apparatus for providing a gas mixture to a reaction chamber and method of using same |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB122278A (en) * | 1918-01-30 | 1919-01-23 | Robert Stirling | Improvements in Apparatus used in Air-lift Pumps. |
| US1761363A (en) * | 1927-08-26 | 1930-06-03 | Gypsy Oil Company | Apparatus for and method of flowing wells |
| US2994335A (en) * | 1957-05-20 | 1961-08-01 | Merla Tool Corp | Flow valve devices |
| US3672790A (en) * | 1971-04-15 | 1972-06-27 | Berkeley Steel Construction Co | Air lift pump |
| RO62593A (en) * | 1975-02-12 | 1977-12-15 | Inst Pentru Creatie Stintific | GASLIFT DEVICE |
-
1995
- 1995-08-25 MY MYPI95002532A patent/MY115179A/en unknown
- 1995-09-04 MX MX9601696A patent/MX9601696A/en active IP Right Grant
- 1995-09-04 DE DE69519425T patent/DE69519425D1/en not_active Expired - Lifetime
- 1995-09-04 EP EP95930623A patent/EP0752049B1/en not_active Revoked
- 1995-09-04 AU AU33942/95A patent/AU708875C/en not_active Expired
- 1995-09-04 NZ NZ292221A patent/NZ292221A/en not_active IP Right Cessation
- 1995-09-04 WO PCT/GB1995/002079 patent/WO1996007813A1/en not_active Ceased
- 1995-09-04 AT AT95930623T patent/ATE197629T1/en not_active IP Right Cessation
- 1995-09-04 BR BR9506382A patent/BR9506382A/en not_active Application Discontinuation
- 1995-09-04 CA CA002175928A patent/CA2175928C/en not_active Expired - Lifetime
-
1996
- 1996-05-06 OA OA60825A patent/OA10580A/en unknown
- 1996-05-06 NO NO19961823A patent/NO311449B1/en active IP Right Review Request
Also Published As
| Publication number | Publication date |
|---|---|
| AU708875C (en) | 2005-03-24 |
| CA2175928C (en) | 2009-07-07 |
| MX9601696A (en) | 1997-03-29 |
| CA2175928A1 (en) | 1996-03-14 |
| MY115179A (en) | 2003-04-30 |
| NO961823L (en) | 1996-07-04 |
| AU708875B2 (en) | 1999-08-12 |
| NO961823D0 (en) | 1996-05-06 |
| DE69519425D1 (en) | 2000-12-21 |
| WO1996007813A1 (en) | 1996-03-14 |
| EP0752049B1 (en) | 2000-11-15 |
| BR9506382A (en) | 1997-09-16 |
| ATE197629T1 (en) | 2000-12-15 |
| NZ292221A (en) | 1997-10-24 |
| EP0752049A1 (en) | 1997-01-08 |
| NO311449B1 (en) | 2001-11-26 |
| AU3394295A (en) | 1996-03-27 |
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