CA2161347C - Fluid composition meter - Google Patents

Fluid composition meter Download PDF

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Publication number
CA2161347C
CA2161347C CA002161347A CA2161347A CA2161347C CA 2161347 C CA2161347 C CA 2161347C CA 002161347 A CA002161347 A CA 002161347A CA 2161347 A CA2161347 A CA 2161347A CA 2161347 C CA2161347 C CA 2161347C
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Canada
Prior art keywords
conduit
radiation
solid state
wall
fluid
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Expired - Lifetime
Application number
CA002161347A
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French (fr)
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CA2161347A1 (en
Inventor
Alexander Meijnhart Scheers
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Shell Canada Ltd
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Shell Canada Ltd
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Priority claimed from PCT/EP1994/001320 external-priority patent/WO1994025859A1/en
Publication of CA2161347A1 publication Critical patent/CA2161347A1/en
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Publication of CA2161347C publication Critical patent/CA2161347C/en
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/02Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material
    • G01N23/06Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and measuring the absorption
    • G01N23/12Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and measuring the absorption the material being a flowing fluid or a flowing granular solid

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  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)
  • Measurement Of Radiation (AREA)

Abstract

An apparatus for measuring a composition of a fluid flowing through a flowlines is provided, the apparatus comprising a conduit (1) suitable to be connected to the flowline so that a stream of the fluid flows through the conduit, a radioactive source (15) arranged in a manner that radiation from the source passes through die stream of fluid and through a wall of the conduit, a detector (17) for detecting radiation passing through said stream and through said wall, and means to generate a signal representative of the radiation detected by the detector. In one aspect of the invention the wall of the conduit (1) comprises a fibre reinforced resin. In another aspect of the invention the detector (17) comprises a solid state detector cooled by a Peltier element (21).

Description

21b1341 FLUID COMPOSITION METER
The invention relates to an apparatus for measuring a composition of a fluid flowing through a flowline. When a multi-component fluid is transported through a flowline to a processing facility, it is generally required to measure the composition of the fluid either at a location along the flowline or at the upstream end thereof. In the oil and gas industry, wellbore fluids can be transported from an onshore or offshore wellhead through a flowline to a processing facility where the different components of the fluid are separated from each other. The wellbore fluids can include oil, gas and water in fractions which can vary in time and can be different for different wells producing from the same subsurface reservoir. Measurement of fluid composition directly at the wellheads or further downstream where streams from different wells are joined enables specific reservoir characteristics to be updated during the producing lifetime of the reservoir, and allows timely corrective measures to be taken if necessary.
European patent No. 269 432 discloses an apparatus for measuring a composition of a fluid flowing through a flowline, comprising a conduit suitable to be connected to the flowline in a manner that a stream of said fluid flows through a conduit, a radioactive source arranged so that radiation from the source passes through a wall of the conduit and through the stream of fluid, a radiation detector arranged so as to detect said radiation passing through the wall of the conduit and through the 2J stream of fluid, and means to generate a signal representative of said radiation detected by the detector. The amount of radiation passing through the stream of fluid and which is detected by the c'~tector provides an indication of the composition of the fluid.
The wall of the conduit through which radiation passes forms a radiation window made of beryllium, which wall is surrounded by a tubular guard provided with diametrically opposed holes for Ai~IENDcD SHEET
- 2 -passage of the radiation. A drawback of the known device is that toxic beryllium oxide will form on the surface of the beryllium wall. Furthermore, for high pressure applications a relatively thick beryllium wall is required, resulting in a significant attenuation of radiation in the beryllium wall and a corresponding reduction of accuracy of the composition measurement.
It is an object of the present invention to provide an apparatus for measuring a fluid composition of a stream of multi-component fluid, which overcomes the drawbacks of the prior art apparatus.
It is another object of the invention to provide an apparatus for measuring a fluid composition of a stream of multi-component fluid, which apparatus is compact and provides accurate measurements.
In accordance with the present invention the apparatus for measuring a composition of a stream of fluid flowing through a flowline is characterized in that the detector comprises a solid state detector configuration with at least two detection surfaces and a filter which is located between the radiation source and a first of said detection surfaces.
In general, the efficiency of a solid state detector decreases with increasing radiation energy level. If for example an Americium (Am-241) radiation source is used which radiates at a low energy level of 18 KeV and at a high energy level of 60 KeV, 2J the detector efficiency at the low energy radiation level is about 50-60$, while the detector efficiency at the high energy radiation level is about 5$. In the apparatus according to the invention the efficiency of the detector is improved by providing a solid state detector configuration with at least two radiation detecting surfaces, whereby a filter is located between the radiation source and a first of said detecting surfaces.
Preferably, the filter substantially prevents the low energy radiation to pass therethrough, and substantially allows the high energy level radiation to pass therethrough. Thereby it is A~~lrwuC~ SHLL I
- 3 -achieved that the low energy level portion of the radiation passing through the fluid mixture and the wall of the conduit is substantially detected by a second of said two detecting surfaces.
Furthermore, the high energy level portion of the radiation which passes through the fluid mixture and the wall of the conduit is substantially detected by said first detecting surface at an increased efficiency since by the arrangement of the filter the count-rate for the high energy level portion is significantly increased. Preferably the filter comprises Copper.
It is to be understood that in the context of the present invention the term solid state detector refers to a semiconductor diode detector, for example as described in publication ISBN 0-471-49545-x entitled "Radiation detection and measurement", chapter 11. Such a detector is compact and has a high resolution in the energy range between 15-100 keV which is suitable for the measurement. The resolution and efficiency of the semiconductor diode detector can be increased by providing the detector with cooling means which maintain the temperature of the detector between 0-15 °C, or preferably between 5-10 °C.
A suitable cooling means forms a Peltier element since such element is compact, whereby the compactness of the apparatus is even enhanced when the detector is directly attached to the Peltier element.
It is preferred that the wall of the conduit comprises a 2J fibre reinforced resin. It has been found that the wall of fibre reinforced resin forms an adequate radiation window with low radiation absorption, while such a wall allows relatively high internal pressures to be applied. Furthermore, in the absence of beryllium there is no danger that beryllium oxide will form, and future problems of disposing beryllium are eliminated.
Absorption of radiation in the conduit wall is particularly 1-ow when the wall is reinforced with carbon fibres. In view thereof it is preferred that the wall comprises a relatively high percentage of carbon fibres, for example between 50-70~ wt carbon 3~ fibres.
A~'m~~::lL~ .:_i
- 4 -A suitable matrix material to be applied for the wall forms a polyether resin, such as an epoxy resin.
The composition of the fluid flowing through the flowline is determined from the signal representing the radiation detected by the detector according to the invention in accordance with the following method:
The absorption of gamma rays in matter is described by the following equation:
I (e) = I (e) .exp(-~(e) .h, where I (e) - initial intensity of the gamma rays at energy e;

I(e) - intensity of the gamma rays after absorption at energy e;
~(e) - linear absorption coefficient at energy e;
h = thickness of material.
Given an oil/water/gas mixture in a pipe of internal diameter d and wall thickness t, the following equations can be derived for two energy levels e1 and e2:
I (e1) = I (e1) .exp.(-N.mix(el) .d) .exp(-~tpipe(el) .2t) and I(e2) - I (e2).exp(yix(e2).d).exp(-~pipe(e2).2t), where ~mix(el) _ ~oil(el)~xoil + ~water(el)~°~water + ugas(el).~cgas and ~x(e2) _ ~oi1(e2).°~oil + ~water(e2).°~water +
~gas(e2)~°~gas The symbol oc refers to the volume fraction of the subscripted phase; the sum of all the three fractions should be equal to 1:
°~oil + °~water + °~gas = 1 if the absorption coefficients for oil, water and gas are measured in separate calibration procedure, then, by measuring the radiation absorption through a pipeline filled with oil, water and ,, _~
~G

21b1347 - 4a -gas, at two gamma-ray energy levels e1 and e2 the three fractions °~oil~ °~water and ocgas can be determined using the above equations.
It is observed that the International Journal of Applied Radiation and Isotopes, Vol. 34, No. 1, January 1982, discloses on pages 309-331 that a solid state detector which is cooled by a Peltier element can be used in an apparatus for on-stream analysis of metalliferous ore slurries, that European patent specification No. 0 187 460 discloses the use of several gamma ray detectors for measuring the composition of a multiphases fluid stream in a flowline along several chords and that European patent specification 0 236 623 discloses the use of a single radiation detector together with a differential pressure gauge in a multiphase flowmeter.
1J The invention will now be described by way of example in more detail with reference to the drawings in which:
- 5 -Fig. 1 shows schematically a longitudinal cross-section of the apparatus according to the invention;
Fig. 2 shows cross-section 2-2 of the apparatus of Fig. 1;
The apparatus of Figs. 1 and 2 includes a steel conduit 1 having a central part 3 of reduced internal diameter. A carbon fibre reinforced epoxy (CFRE) cylinder 5 is located in a recess 7 provided at the inside of the central part 3 of the conduit 1. The wall of the central part 3 of the conduit 1 is provided with four ooeninqs 10, 11, 12, 13, whereby openings 11, 12, 13 are arranged opposite opening 10 and at spaced intervals along the circumference of the conduit 1. Each opening 10, 11, 12, 13 extends from the outer surface of the conduit 1 to the outer surface of the CFRE cylinder 5.
An X-ray or gamma-ray radiation source 15 is located in opening 10 which forms a collimator for the source 15. Three solid state detectors 16, 17, 18 are located in openings 11, 12, 13 respectively, which openings 11, 12, 13 form respective collimators for the detectors 16, 17, 18 so that the latter can detect radiation from the source 15. The detectors 16, 17, 18 are attached to respective Peltier elements 20, 21, 22 which serve to maintain the temperature of the detectors 16, 17, 18 between 5-10 °C. An electronic processor Inot shown) is linked to the detectors 16, 17, 18 to receive and process signals representing the radiation detected by the detectors 16, 17, 18.
The radioactive source 15 is selected such that suitable energy levels e1 and e2 are emitted so that ~oil~ °~water and ocgas can be solved using the above equations.
A differential pressure meter 29 is connected to a pressure tap 26 located at the inner surface of the conduit 1 adjacent the central part 3 thereof, and to a pressure tap 28 located at the inner surface of the central part 3 of the conduit 1.
The conduit 1 is at both ends provided with flanges 30, 32 to connect the conduit 1 to a flowline (not shown) for transporting fluid containing oil, water and gas produced from a wellbore in an earth formation.

WO 94/25859 21 b 13 4 l PCT/EP94/01320
- 6 -During normal operation of the apparatus shown in Figs. 1 and 2, the conduit 1 is connected to the flowline and a stream of fluid containing oil, water and gas produced from the wellbore flows through the conduit 1. X-ray or gamma-ray radiation emitted by radiation source 15 passes through the wall of the carbon fibre reinforced cylinder 5 and through the stream of fluid towards the detectors 16, 17, 18, whereby the radiation is partly absorbed by the wall of the CFRE cylinder 5 and by the stream of fluid. Thus, the radiation emitted by the source 15 is attenuated by the wall of the CFRE cylinder 15 and by the stream of fluid. The attenuated radiation is detected by the detectors 16, 17, 18 and signals representing the attenuated radiation are received by the electronic processor which determines the composition of the fluid using the above equations. Furthermore, the differential pressure meter 29 provides signals representing the flow rate of the fluid mixture, so that the flowrates of the individual fluid components can be calculated.
Application of several detectors at circumferentially spaced locations around the conduit has the advantage, compared to applying only one detector, that the count-rate is thereby increased and that the homogeneity of the fluid can be checked by comparing the fluid composition as determined from the individual detectors. In the embodiment shown in Figs. 1 and 2 three detectors are applied, however less or more than three detectors can be applied in the apparatus according to the invention depending on the characteristics of the application.
A suitable material for constructing a CFRE cylinder for use in the apparatus described with reference to Figs. 1 and 2 comprises Araldit LY556 resin with HY917 hardener and DY070 hardening accelerator manufactured by Ciba Geigy, and Tenax IM-400-12000 carbon fibres manufactured by AKZO. A CFRE cylinder was constructed from this material with an internal diameter of 43 mm and a wall-thickness of 2mm, and was positioned within a steel conduit provided with one 16 mm diam opening and three 8 mm diam openings for locating the radiation source and the three detectors respectively.

A pressure test revealed that the CFRE cylinder could withstand an internal pressure of 120 MPa.
To reduce attenuation of the radiation in the wall of the conduit, in an alternative embodiment of the apparatus according to the invention at least one of the source and the detector is arranged within the conduit.
In such embodiment, it is preferred that the source is arranged within the conduit and the detector is arranged outside the conduit.
Thus the radiation passes through the wall of the conduit only once.
Suitably the source is surrounded by a sleeve located within the conduit, which sleeve preferably is arranged concentrically within the conduit.

Claims (16)

CLAIMS:
1. An apparatus for measuring a composition of a fluid flowing through a flowline, comprising a conduit suitable to be connected to the flowline in a manner that a stream of said fluid flows through the conduit, a radioactive source arranged so that radiation from the source passes through a wall of the conduit and through the stream of fluid, a radiation detector arranged so as to detect said radiation passing through the wall of the conduit and through the stream of fluid, and means to generate a signal representative of said radiation detected by the detector, characterized in that the detector comprises a solid state detector configuration which is provided with at least two radiation detection surfaces and a filter which is located between the radiation source and a first of said detection surfaces.
2. The apparatus of claim 1, wherein the filter substantially prevents the low energy radiation and allows the high energy radiation to pass therethrough.
3. The apparatus of claim 1 or 2, wherein the filter comprises copper.
4. The apparatus of claim 1, 2 or 3, wherein the solid state detector configuration is provided with cooling means so as to maintain the temperature of the solid state detector configuration between 0-15 °C.
5. The apparatus of claim 4, wherein the solid state detector configuration is provided with cooling means so as to maintain the temperature of the solid state detector configuration between 5-10 °C.
6. The apparatus of claim 4 or 5, wherein the cooling means is in the form of a Peltier element.
7. The apparatus of claim 6, wherein the detector configuration is directly attached to the Peltier elements.
8. The apparatus of any one of claims 1 to 7, wherein said flowline has along a part of its length a reduced diameter, and the apparatus further comprises means for measuring a differential pressure in the stream of fluid flowing through the part of reduced diameter.
9. The apparatus of any one of claims 1 to 8, wherein at least one of the source and the solid state detector configuration is arranged within the conduit.
10. The apparatus of claim 9, wherein the source is arranged within the conduit and the solid state detector configuration is arranged outside the conduit.
11. The apparatus of any one of claims 1 to 10, wherein the solid state detector configuration comprises a plurality of solid state detectors which are arranged at circumferentially spaced locations around the conduit.
12. The apparatus of any one of claims 1 to 11, wherein the wall of the conduit comprises a fibre reinforced resin.
13. The apparatus of claim 12, wherein the wall of the conduit comprises a carbon fibre reinforced resin.
14. The apparatus of claim 12 or 13, wherein said resin comprises a polyether resin.
15. The apparatus of claim 14, wherein said polyether resin comprises an epoxy resin.
16. The apparatus of any one of claims 11 to 14, wherein the wall of the conduit comprises a relatively high percentage of carbon fibres.
CA002161347A 1993-04-26 1994-04-25 Fluid composition meter Expired - Lifetime CA2161347C (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
EP93201196.8 1993-04-26
EP93201196 1993-04-26
PCT/EP1994/001320 WO1994025859A1 (en) 1993-04-26 1994-04-25 Fluid composition meter

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Publication Number Publication Date
CA2161347A1 CA2161347A1 (en) 1994-11-10
CA2161347C true CA2161347C (en) 2006-12-05

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