U.S. patent application number 11/572055 was filed with the patent office on 2008-12-18 for detector for distinguishing phases in a multiphase fluid mixture.
This patent application is currently assigned to SCHLUMBERGER TECHNOLOGY CORPORATION. Invention is credited to Paul Guieze, Bruno Pinguet.
Application Number | 20080307860 11/572055 |
Document ID | / |
Family ID | 34931259 |
Filed Date | 2008-12-18 |
United States Patent
Application |
20080307860 |
Kind Code |
A1 |
Guieze; Paul ; et
al. |
December 18, 2008 |
Detector for Distinguishing Phases in a Multiphase Fluid
Mixture
Abstract
A detector (1) is used distinguishing a phase from a multiphase
fluid mixture. The detector comprises: an optical probe (2) for
optically distinguishing one of the phases from the multiphase
fluid mixture, the optical probe having a tip (20) in contact with
the multiphase fluid mixture, and a detector cell (3) arranged to
be coupled to a multiphase fluid mixture flowing line (L) and to
the optical probe (2). The detector cell (1) further comprises: an
internal flowing line (4) arranged so that the phases of the
multiphase fluid mixture flowing in the internal flowing line are
driven-on by capillarity effect, and a bore (5) coupled to the
internal flowing line for positioning the optical probe in the
detector cell so that the multiphase fluid mixture flows
substantially around the tip (20) of the optical probe.
Inventors: |
Guieze; Paul; (Fontenailles,
FR) ; Pinguet; Bruno; (Bergen, NO) |
Correspondence
Address: |
SCHLUMBERGER OILFIELD SERVICES
200 GILLINGHAM LANE, MD 200-9
SUGAR LAND
TX
77478
US
|
Assignee: |
SCHLUMBERGER TECHNOLOGY
CORPORATION
Sugar Land
TX
|
Family ID: |
34931259 |
Appl. No.: |
11/572055 |
Filed: |
July 11, 2005 |
PCT Filed: |
July 11, 2005 |
PCT NO: |
PCT/EP2005/007602 |
371 Date: |
July 28, 2008 |
Current U.S.
Class: |
73/61.44 ;
73/152.29 |
Current CPC
Class: |
G01F 5/00 20130101; G01F
1/7086 20130101; G01N 33/2823 20130101; G01N 21/8507 20130101; G01F
1/74 20130101; G01N 21/431 20130101 |
Class at
Publication: |
73/61.44 ;
73/152.29 |
International
Class: |
E21B 47/00 20060101
E21B047/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 13, 2004 |
EP |
EP04291832.6 |
Claims
1. A detector for distinguishing a phase from a multiphase fluid
mixture, the detector comprising: an optical probe for optically
distinguishing one of the phases from the multiphase fluid mixture,
the optical probe having a tip in contact with the multiphase fluid
mixture, and a detector cell arranged to be coupled to a multiphase
fluid mixture flowing line (L) and to the optical probe, wherein
the detector cell further comprises: an internal flowing line
arranged so that the phases of the multiphase fluid mixture flowing
in the internal flowing line are driven-on by capillarity effect,
and a bore coupled to the internal flowing line for positioning the
optical probe in the detector cell so that the multiphase fluid
mixture flows substantially around the tip of the optical
probe.
2. A detector for distinguishing a phase from a multiphase fluid
mixture according to claim 1, wherein the internal flowing line has
an internal diameter (ID) substantially corresponding to a
capillary tube diameter.
3. A detector for distinguishing a phase from a multiphase fluid
mixture according to claim 1, wherein the internal flowing line has
an internal diameter ranging from 0.5 mm to 20 mm.
4. A detector for distinguishing a phase from a multiphase fluid
mixture according to claim 1, wherein the internal flowing line and
the bore of the detector cell forms a Y having a first, a second
and a third branch, the first and second branch being formed by the
internal flowing line and the third branch being formed by the bore
of the detector cell.
5. A detector for distinguishing a phase from a multiphase fluid
mixture according to claim 4, wherein the first and second branch
are perpendicular.
6. A detector for distinguishing a phase from a multiphase fluid
mixture according to claim 4, wherein the first and second branch
are in-line.
7. A detector for distinguishing a phase from a multiphase fluid
mixture according to claim 4, wherein the third branch is
perpendicular to the second branch.
8. A detector for distinguishing a phase from a multiphase fluid
mixture according to claim 1, wherein the optical probe is coupled
to the bore of the detector cell through a compression fitting.
9. A detector for distinguishing a phase from a multiphase fluid
mixture according to claim 1, wherein the optical probe comprises a
sapphire rod having a bi-cone shaped tip, the optical probe being
connected to an electronic module though an optical fiber.
10. A transferring arrangement, for transferring a single phase
from a sampling bottle comprising a multiphase fluid mixture to a
shipping bottle, the transferring arrangement comprising: a flow
line (L) coupling the sampling bottle to the shipping bottle, and a
pumping arrangement for transferring a fluid from the sampling
bottle to the shipping bottle, a detector for distinguishing a
phase from a multiphase fluid mixture, the detector comprising: an
optical probe for optically distinguishing one of the phases from
the part of the multiphase fluid mixture, the optical probe having
a tip in contact with the fluid transferred from the sampling
bottle to the shipping bottle, a detector cell arranged to be
coupled to the flow line (L) and to the optical probe and
comprising an internal flowing line and a bore coupled to the
internal flowing line, the bore positioning the optical probe in
the detector cell so that the part of the multiphase fluid mixture
flows substantially around the tip of the optical probe.
11. A hydrocarbon well testing arrangement, for testing a well that
produces a multiphase fluid mixture flowing though a main line, the
arrangement comprising: a derivation line coupled to the main line
for deriving a part of the multiphase fluid mixture, a detector for
distinguishing a phase from a multiphase fluid mixture, the
detector comprising: an optical probe for optically distinguishing
one of the phases from the part of the multiphase fluid mixture,
the optical probe having a tip in contact with the part of the
multiphase fluid mixture, a detector cell arranged to be coupled to
the derivation line and to the optical probe and comprising an
internal flowing line and a bore coupled to the internal flowing
line, the internal flowing line being arranged so that the phases
of the part of the multiphase fluid mixture flowing in the internal
flowing line are driven-on by capillarity effect, the bore
positioning the optical probe in the detector cell so that the part
of the multiphase fluid mixture flows substantially around the tip
of the optical probe. an acquisition device connected to the
detector.
12. A hydrocarbon well flowrate measurement arrangement, for
measuring a flowrate of a phase of a multiphase fluid mixture
flowing though a main line of a hydrocarbon well, the arrangement
comprising: a derivation line coupled to the main line for deriving
a part of the multiphase fluid mixture, at least two detectors for
distinguishing a phase from a multiphase fluid mixture, each
detector being connected in serial along the derivation line, each
detector comprising: an optical probe for optically distinguishing
one of the phases from the part of the multiphase fluid mixture,
the optical probe having a tip in contact with the part of the
multiphase fluid mixture, a detector cell arranged to be coupled to
the derivation line and to the optical probe and comprising an
internal flowing line and a bore coupled to the internal flowing
line, the internal flowing line being arranged so that the phases
of the part of the multiphase fluid mixture flowing in the internal
flowing line are driven-on by capillarity effect plugs and rings in
the internal flowing line, the bore positioning the optical probe
in the detector cell so that the part of the multiphase fluid
mixture flows substantially around the tip of the optical probe. an
acquisition device connected to the detectors, the acquisition
device: receiving from each detector a signal which level is
characteristic of the phase flowing around the tip, performing a
cross correlation of the received signals, determining a transit
time of each phase from one detector to the other, and computing a
measurement representative of the flow rate in the main line.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a detector for distinguishing a
phase from a multiphase fluid mixture. The detector comprises an
optical probe for optically distinguishing one of the phases from
the multiphase fluid mixture based on the refractive index of the
phases.
[0002] A particular application of the invention relates to the
detection of the various phases of a multiphase fluid mixture from
a hydrocarbon well. Such a multiphase fluid mixture typically
comprises three phases: an aqueous phase, a liquid hydrocarbon
phase and a gaseous hydrocarbon phase.
[0003] The invention also relates to particular applications and
arrangements of the detector to measurement in the oil
industry.
BACKGROUND OF THE INVENTION
[0004] After a hydrocarbon well has been drilled and made safe, a
well testing operation is generally carried out for a short period
of time. The well testing operation serves to characterize the
various components of the effluent flowing out of well, and to
estimate the production capacities of the well. Once the well
testing operation is finished, a well producing operation is
carried out as long as the oil produced is satisfactory in term of
quality, flowing rate, etc. . . .
[0005] At the beginning of the well testing operation, the
composition of the effluent varies considerably. The well is
initially filled with aqueous residues from the well construction
operation such as drilling fluid and completion fluid. The effluent
that is initially collected is essentially made up of water.
Subsequently, the percentage of aqueous residue decreases
gradually, and the composition of the effluent becomes enriched
with oil and with gas. Thus, the effluent is a multiphase fluid
mixture.
[0006] During the testing and producing operation, an important
concern is to identify as accurately as possible the various phases
that constitute the multiphase fluid mixture.
[0007] For distinguishing a phase from a multiphase fluid mixture,
it is known to perform visual observation of the multiphase fluid
mixture flowing through a well flowing line. A visual observation
can be performed by way of a universal fluid phase detector.
[0008] The universal fluid phase detector mainly comprises
sight-glass disposed on the well flowing line. A visual observation
can be performed through the glass directly by an operator or
recorded by a video camera for subsequent interpretation. The phase
sensing can also be performed using an optical probe based on light
attenuation. These visual observations induce complex mechanical
system and safety problems when operating at high pressure and high
temperature. Moreover, the visual observations are by nature
limited by dirty windows, wettability issues and inaccuracy or
misinterpretation from operators.
[0009] Alternatively, specific fluid detectors are known for
sensing a particular component of a phase using a specific physical
property (conductivity, specific light absorption, etc. . . . ).
These detectors are limited to one phase amongst the others.
[0010] U.S. Pat. No. 5,956,132 describes an apparatus comprising an
optical probe for discriminating between the three phases of a
moving fluid comprising gas, oil and water.
[0011] The optical probe comprises a detector block having a
sensitive zone in contact with the moving fluid. An incident light
beam injected in the detector block enables to discriminate between
the three phases by using a measurement technique based on the
reflection of light induced by the specific refractive indices of
each phase.
[0012] The apparatus, in particular the detector block is placed in
the moving three-phase fluid flowing along the oil well line. The
oil well line has an internal diameter of a few centimeters.
Because of the oil well line dimension, a plurality of detectors is
placed at different distances from the axis of the well and at
different azimuths, so as to obtain a three-dimensional image of
the phases in the flowing fluid. Besides, because of the internal
diameter of the oil well line and the position of the optical probe
in the line, wettability issues and dirt deposit on the probe are a
source of inaccuracy.
SUMMARY OF THE INVENTION
[0013] One goal of the invention is to propose a detector for
distinguishing a phase from a multiphase fluid mixture based on
optical measurement that has a better accuracy than the prior art
measurement apparatus and system.
[0014] According to the invention, a detector comprising an optical
probe coupled to a detector cell is designed in such a way that
each phase of the multiphase fluid mixture circulates around a
probe tip.
[0015] More precisely, the present invention relates to a detector
for distinguishing a phase from a multiphase fluid mixture, the
detector comprising: [0016] an optical probe for optically
distinguishing one of the phases from the multiphase fluid mixture,
the optical probe having a tip in contact with the multiphase fluid
mixture, and [0017] a detector cell arranged to be coupled to a
multiphase fluid mixture flowing line and to the optical probe.
[0018] The detector cell further comprises: [0019] an internal
flowing line arranged so that the phases of the multiphase fluid
mixture flowing in the internal flowing line are driven-on by
capillarity effect, [0020] a bore coupled to the internal flowing
line for positioning the optical probe in the detector cell so that
the multiphase fluid mixture flows substantially around the tip of
the optical probe.
[0021] The internal flowing line is dimensioned so that the phases
of the multiphase fluid mixture flowing in the internal flowing
line are driven-on by capillarity effect. Due to the capillarity
effect, the fluid mixture will either flows as plugs and rings or
as a biphasic emulsion (in case the fluid mixture is an emulsion of
water and oil, of oil and gas, etc. . . . ). The internal flowing
line has an internal diameter substantially corresponding to a
capillary tube diameter. For example, the capillary tube diameter
may range from 0.5 mm to 20 mm. However, this range typically
varies depending on the fluid mixture properties.
[0022] The optical probe is coupled to the bore of the detector
cell through a compression fitting and connected to an electronic
module though an optical fiber.
[0023] Consequently, with the detector according to the invention,
the multiphase fluid mixture is driven-on by capillarity effects
and is forced to circulate around the optical probe (typically at a
flowrate around a few cm/s, e.g. 3 cm/s to 15 cm/s). These
characteristics enable an auto-cleaning of the optical probe tip
limiting any dirt deposit on the optical probe and improving
accuracy of the whole detector.
[0024] The detector according to the invention is compact, light,
safe and accurate. The detector constitutes a compact hand-held
equipment that can be used in full autonomy or connected to an
acquisition system. The detector can withstand high-pressure
(higher than 700 bar) and high temperatures (higher than
150.degree. C.) that are expected in oil and gas field surface,
down-hole and subsea operations. The detector is advantageously
compliant with the safety regulation for being operated in
hazardous area.
[0025] In a first application, the detector according to the
invention is used as an in-line phase detector allowing sensing
gas, oil/condensate and water during sampling or bottle transfer
down-hole or in sub-sea operations. In such an application, the
detector according to the invention enables to ensure that the
sampled phase is the expected one, and enables to sense the
interface between the various phases during fluid transfer
operations from vessel to vessel (a vessel being a generic
terminology for e.g. sampler, shipping cylinder, PVT cell,
pycnometer, flash apparatus, etc. . . . ).
[0026] In this application, the detector is integrated in an
arrangement for transferring a single phase from a sampling bottle
comprising a multiphase fluid mixture to a shipping bottle. The
transferring arrangement comprises a flow line coupling the
sampling bottle to the shipping bottle, a pumping arrangement for
transferring a fluid from the sampling bottle to the shipping
bottle, and a detector according to the invention.
[0027] In a second application, the detector according to the
invention is used as an in-line phase ratios monitoring
application. In such an application, the detector according to the
invention enables to accurately measure the fractions of each phase
in the multiphase fluid mixture. This is also advantageous for
improving measurement made by other oil-water-gas fraction
measuring apparatus. In this case, the detector according to the
invention is used as a redundancy device or as a recalibration
device.
[0028] In this application, the detector is integrated in an
arrangement for testing a well that produces a multiphase fluid
mixture flowing through a main line. The arrangement comprises a
derivation line coupled to the main line for deriving a part of the
multiphase fluid mixture, a detector according to the invention and
an acquisition device connected to the detector.
[0029] In a third application, the detector according to the
invention is used as a flow rate measuring apparatus. The
arrangement for measuring a flowrate of a phase of a multiphase
fluid mixture flowing though a main line of a hydrocarbon well
comprises a derivation line coupled to the main line for deriving a
part of the multiphase fluid mixture, at least two detectors
according to the invention, each detector being connected in serial
along the derivation line and an acquisition device connected to
the detectors. The acquisition device receives from each detector a
signal which level is characteristic of the phase flowing around
the tip, performs a cross correlation of the received signals,
determines a transit time of each phase from one detector to the
other, and computes a measurement representative of the flow rate
in the main line.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] The present invention is illustrated by way of example and
not limited to the accompanying figures, in which like references
indicate similar elements:
[0031] FIG. 1 schematically illustrates a detector for
distinguishing a phase from a multiphase fluid mixture according to
the invention;
[0032] FIGS. 2.A, 2.B and 2.C schematically illustrate various
embodiments of the detector cell of the invention;
[0033] FIG. 3 schematically illustrates the preferred embodiments
of the detector cell of the invention comprising an optical
probe;
[0034] FIG. 4 schematically illustrates the known operation
principle of the optical probe;
[0035] FIG. 5 schematically illustrates a first application of the
invention, namely a stand-alone phase interface sensing
application;
[0036] FIG. 6 schematically illustrates a second application of the
invention, namely an in-line phase ratios monitoring
application;
[0037] FIG. 7 shows a typical signal over time graphic obtained in
the second application of the invention shown in FIG. 6.
DETAILED DESCRIPTION OF THE INVENTION
[0038] FIG. 1 shows a detector 1 for distinguishing a phase from a
multiphase fluid mixture. The detector comprises a detector cell 3
connected to an electronic module 10.
[0039] The detector cell 3 comprises an input connection 7 and an
output connection 8 that are connectable to a flow line (not shown)
in which the multiphase fluid mixture FM flows. Preferably, the
input 7 and output connections 8 are high-pressure connection. The
detector cell 3 further comprises an optical probe 2 coupled to an
optical fiber 11 by an optical connector 12A. The optical fiber 11
connects the optical probe 2 to the electronic module 10.
Advantageously, the optical fiber 11 is an armored optical
fiber.
[0040] The detector cell will be described in greater details here
below.
[0041] The electronic module 10 has the form of a hand-held
housing. The electronic module 10 comprises an optical connector
12B for optically connecting the module to the optical fiber 11.
The electronic module 10 further comprises a circuit board 13. The
circuit board 13 comprises electronic elements, in particular an
emitting diode 15A and detecting diode 15B, and other electronic
elements (not shown) for ensuring the functionality of the
detector.
[0042] The emitting and detecting diodes are connected to the
optical fiber 11 via an optical coupling 14. The optical coupling
14 is an optical fiber assembly having a Y shape that connects the
optical probe to both emitting and detecting diodes.
[0043] The emitting diode is advantageously a laser type diode. The
detecting diode is advantageously a photo-transistor.
[0044] The electronic module 10 also comprises a display 16, a
power switch 19, and a power supply connection 17. The electronic
module 10 may also comprise an input/output connector 18. All these
elements are connected to the circuit board 13. The circuit board
13 controls the light emission by the emitting diode 15A, the light
detection by the detecting diode 15B, the display and eventually
the signal input/output via the input/output connector 18.
[0045] The display 16 can comprise 3 LEDs, each LEDs indicating
which phase is currently in contact with the optical probe. The
display 16 can also be of a more sophisticated type, e.g. LCD
display, giving further information about the detector status,
information related to measurement performed and/or graphical
evolution of measurements versus time.
[0046] Advantageously, the electronic module 10 comprises an
internal power supply under the form of a battery (not shown) which
enables a full autonomous mode. Advantageously, in safe area
operation, the alimentation connection 17 can be used as a direct
power supply or as a battery charging input. Advantageously, the
input/output connector 18 can be designed for connection to various
peripheral (e.g. computer, printer, etc. . . . ). In particular,
the input/output connector 18 can deliver an output signal (for
example a 4 mA to 20 mA signal) for allowing the acquisition of the
detector response versus time on a computer, or any other
acquisition devices.
[0047] The electronic module is advantageously designed and built
according to safety standards for being used in explosive area.
[0048] FIGS. 2.A, 2.B and 2.C schematically illustrate various
embodiments of the detector cell of the invention. The detector
cell is represented without an optical probe for sake of
clarity.
[0049] The detector cell has substantially the form of a
parallelepiped bloc. Alternatively, the detector cell can be
incorporated in a manifold of valves.
[0050] The detector cell 3 is arranged to be coupled to the
multiphase fluid mixture flowing line (not shown) by means of input
connection 7 and output connection 8. The detector cell 3 is also
arranged to be coupled to the optical probe (not shown on FIG. 2).
Obviously, the input connection 7 and output connection 8 can be
inverted, the detector being able to perform measurements on a
fluid mixture flowing from the input connection 7 towards the
output connection 8 and vice versa.
[0051] The input connection 7 and output connection 8 of the
detector cell are designed for coupling to a flowing line having an
internal diameter similar to the typical diameter used in surface
sampling and/or PVT (Pressure Volume Temperature) laboratory
tubing. Such diameter is typically in the order of one to several
millimeters. Advantageously, the coupling between the connection
and the flowing line is made by means of high-pressure
fittings.
[0052] The detector cell further comprises an internal flowing line
4. The internal flowing line is arranged so that each phase of the
multiphase fluid mixture, penetrating into the detector cell 3 from
the flowing line through the input connection 7, flowing in the
internal flowing line 4 are driven-on by capillarity effect.
Advantageously, the internal flowing line has an internal diameter
ID substantially corresponding to a capillary tube diameter. For
example, the internal flowing line 4 has an internal diameter ID
ranging from 0.5 mm to 20 mm. However, this range can vary because
of the fluid properties. The detector cell further comprises a bore
5 coupled to the internal flowing line 4. The bore enables the
positioning of the optical probe in the detector cell.
[0053] The internal flowing line 4 and the bore 5 of the detector
cell 3 has the shape of a Y. The Y has a first branch 4A, a second
branch 4B and a third branch 4C branch, each branch being connected
to the two other branches by one extremity. The first branch 4A and
second branch 4B are constituted by the internal flowing line 4.
The third branch 4C is constituted by the bore 5.
[0054] FIG. 2.A shows a first embodiment of the detector cell
according to which the first branch 4A is perpendicular to the
second branch 4B. The third branch 4C is perpendicular to the
second branch 4B.
[0055] FIG. 2.B shows a second embodiment of the detector cell
according to which the first branch 4A and the second branch 4B are
in-line. The third branch 4C is perpendicular to the second branch
4B.
[0056] FIG. 2.C shows a third embodiment of the detector cell
according to which the first branch 4A forms an angle .alpha.
respectively to the second branch 4B. The angle .alpha. can take a
value between 90.degree. (corresponding to the first embodiment) to
180.degree. (corresponding to the second embodiment).
[0057] The third branch 4C forms an angle .beta. respectively to
the second branch 4B. The angle .beta. can take a value between
0.degree. to 360.degree.-.alpha., with some restrictions due to the
space occupied by the internal flowing line.
[0058] FIG. 3 schematically illustrates the preferred embodiments
of the detector cell of the invention comprising an optical probe.
The preferred embodiment corresponds to the first embodiment
illustrated in FIG. 2.A. The first branch 4A is perpendicular to
the second branch 4B. The third branch 4C is perpendicular to the
second branch 4B or in-line with the first branch 4A.
[0059] The optical probe 2 comprises a rod. Advantageously, the rod
made of sapphire has a bi-cone shaped tip 20. The sapphire rod is
inserted in a sleeve 2A. The sleeve 2A is advantageously made of
stainless steel. The optical probe is connected to the optical
fiber 11 through an optical connector 12B for handling light coming
into the rod and light coming back from the rod after reflection in
the tip.
[0060] The optical probe 2 is coupled to the bore 5 of the detector
cell through a compression fitting 6.
[0061] The bore 5 and the compression fitting 6 enable the
positioning of the optical probe in the detector cell so that the
multiphase fluid mixture flowing in the internal flowing line 4,
flows substantially around the tip 20 of the optical probe. The
compression fitting also ensures a good sealing between
high-pressure fluids flowing into the internal flowing line of the
detector cell and the external pressure (for example the atmosphere
pressure).
[0062] The preferred embodiment enables an efficient auto-cleaning
of the tip 20 of the optical probe rod. In particular, the risk for
the tip 20 to be subject of dirt deposit (e.g. due to heavy oil
phase) during a long time is very limited.
[0063] Advantageously, all the elements in contact with fluid
(detector cell, optical probe and fittings) are made of materials
like stainless steel and sapphire that are acknowledged being
compliant with the pressure (higher than 700 bar) and temperature
(higher than 150.degree. C.) involved, and chemically compatible
with the various components expected in the multiphase fluid
mixture.
[0064] FIG. 4 is a longitudinal section view in a part of the
optical probe that schematically illustrates the measurement
principle of the optical probe. The optical probe is described in
U.S. Pat. No. 5,956,132, which is herein incorporated by
reference.
[0065] The sapphire rod is inserted in a sleeve 2A and maintained
together by means of a bounding material 2B. The rod is
advantageously made of sapphire and the sleeve 2A of stainless
steel.
[0066] The measurement principle of the probe is based on the
differences in refractive index between water, oil and gas phases.
Typically, the optical refractive index of multiphase fluid flowing
out of a hydrocarbon well is as follows: [0067] for a gas phase (at
the atmospheric pressure), the index ranges between 1.0003 and
1.0020, [0068] for an oil phase, the index ranges between 1.40 and
1.50, [0069] for a water phase, the index ranges between 1.33 and
1.35.
[0070] The sapphire refractive index is 1.77, which ensures a
sufficient contrast with the various phase refractive indices.
[0071] The rod has a bi-cone shaped tip 20. The bi-cone shaped tip
20 comprises a sensitive zone 20A and a total reflection zone 20B.
The sensitive zone 20A and the total reflection zone 20B are
adjacent and coaxial relatively to the rod longitudinal axis. The
sensitive zone 20A forms a first angle .theta.1 (for example
100.degree.) relatively to the rod longitudinal axis, so that an
incident light beam IR is reflected when the probe tip 20 is
surrounded with gas and refracted when the probe tip is surrounded
with liquid. The total reflection zone 20B forms a second angle
.theta.2 (for example 10.degree.) relatively to the rod
longitudinal axis, in order to discriminate between oil and water.
The reflected fraction RR of the incident light beam varies as a
function of the refractive index of the phase of the multiphase
fluid mixture in which the tip is surrounded.
[0072] The optical probe 2 is connected by means of optical fiber
11 to the electronic module 10 comprising the emitting and
detection circuits. The detector provides a signal which level is
specific to the fluid phase in contact with the optical probe
tip.
[0073] When the probe is surrounded by gas, typically 36% of the
incident light beam is reflected in the sapphire tip. The reflected
light beam is detected as a high level signal by the electronic
module 10.
[0074] When the probe is surrounded by oil or gasoline, typically
more than 99% of the incident light beam is refracted in the
surrounding liquid. The reflected light beam is detected as a low
level signal (less than 1%).
[0075] When the probe is surrounded by water, typically 14% of the
incident light beam is reflected. Thus a discrimination of water
relatively to oil and gas is possible (as shown in FIG. 7
representing a typical signal evolution versus time).
[0076] FIG. 5 schematically illustrates a first application of the
invention.
[0077] Identifying phases during sampling operation is a constant
concern during oilfield operations. In effect, for economical
reasons, it is necessary to take a sample of the desired fluid
phase before any future fluid comprehensive laboratory analysis is
performed. Further, it is desirable that each sampled phase is not
polluted with another. Pollution can easily occur: [0078] because
of mass transfer downstream of a sampling valve due to pressure and
temperature change, or [0079] when the sampling is performed in a
multiphase meter that does not enable to collect a pure phase, or
[0080] during fluid transfer from a vessel to another vessel
(sampler, shipping cylinder, PVT cell, pycnometer, flash apparatus,
etc. . . . ).
[0081] For example, when using a down-hole sampling tool, it is
necessary to take a specific phase of the fluid mixture or to
monitor which phases are flowing into a sampling or shipping
bottle.
[0082] In the first application the detector of the invention is
used as a stand-alone phase interface sensing detector. Thus, it is
possible to sense the interfaces between gas, oil and water for
avoiding polluting the transferred sample with another unwanted
one. Typically, in this application, the detector is operated in
full autonomy (battery operation) and the operator uses visual
signal to differentiate between the phase.
[0083] A multiphase fluid mixture is transferred from a sampling
bottle 30 or a down hole sampler into a shipping bottle 32. The
shipping bottle is subsequently shipped to a laboratory for a
detailed analysis of the fluid properties. During such a process,
it is important to ensure that the fluid, generally the one
containing hydrocarbon, transferred into the shipping bottle is in
a single phase (gas or liquid) and to avoid transferring water.
[0084] Once the multiphase fluid mixture has settle by gravity into
a gas G, oil/condensate O and water W layer, the sampling bottle 30
is coupled to the shipping bottle 32 by means of a flow line L. The
sampling 30 and the shipping 32 bottles comprise respective pistons
31 and 33. The shipping bottle is initially filled with a hydraulic
media HM (e.g. water with glycol). During the transferring process,
a transfer pump 34 draw up the hydraulic media HM from a hydraulic
media tank 35 to the sampling bottle 30, thereby pushing the piston
31 and transferring a phase (e.g. gas G) to the shipping bottle.
The phase (e.g. gas G) flowing into the shipping bottle pushes the
piston 33, causing the hydraulic media HM to flow into a test tube
36. Advantageously, the test tube is graduated for volume
measurement.
[0085] The detector 1, in particular the detector cell 3 is
inserted into a flow line L using the high-pressure connections 7
and 8. The detector is used for sensing the interface between gas G
and liquid (condensate/oil O or water W) or between oil/condensate
and water W, in order to stop transfer before a second phase enters
the shipping bottle 32.
[0086] The first application was described by detailing a
particular transfer between a sampling and a shipping bottle.
However, the detector can be used for any transfer between any
vessel (for example PVT laboratories, pycnometer, flash apparatus,
etc. . . . ).
[0087] FIG. 6 schematically illustrates a second application of the
invention.
[0088] Measuring the phase ratios during oilfield operations is an
important concern. In particular, the accurate measurement of the
phase ratios in the main pipe is difficult to perform when one main
phase is present in the pipe (e.g. high gas volume fraction, wet
gas flow or the opposite).
[0089] In this application, the detector 1 is used for determining
the different combinations of gas, water, oil/condensate ratios at
line conditions in a flow line L, which is derived from a main flow
line (not shown). The in-line phase detector is used for the
continuous monitoring of the fluid phases flowing through the line,
by logging the signal versus time.
[0090] The detector 1, in particular the detector cell 3 is
inserted into a flow line L using the high-pressure connections 7
and 8. The detector 1, in particular the electronic module 10, is
connected to an acquisition device 41 (e.g. a computer) for
recording the signal during a flow period.
[0091] Due to the detector cell internal flowing line diameter,
wettability and capillarity effect, the phases of the multiphase
fluid mixture are flowing as plugs and rings, and the fluid is
moving at a relatively constant speed (typically a few cm/s).
Further, the optical probe material limits any wettability effect.
These conditions and properties result in a quasi square signal
having three levels corresponding respectively to gas G, water W
and oil/condensate O. FIG. 7 shows a typical signal S(V) over time
t(s) graphic obtained in the second application of the invention
illustrated in FIG. 6. Further, the signal amplitude ratio enables
to calculate the relevant volumetric fraction of each phase.
[0092] In the case of a very strong emulsion (typically oil and
water), the signal S(V) have an intermediate level between the two
possible value. An estimate based on the signal amplitude ratio
could give the relevant volumetric fraction of each phase.
[0093] In the case of a stable emulsion where the particles
(droplets) size is much smaller than the probe tip dimension, the
signal S(V) is proportional to the water-oil ratio. The detector
could be used for measuring the water-oil ratio.
[0094] The in-line phase detector could be used to calibrate,
recalibrate or compensate any instruments on line measuring
oil/condensate, gas, water or any combination fractions which could
be affected by some of the fluid properties (e.g. a dual gamma ray
measurement apparatus is affected water salinity changes) or by
ageing electronics providing a different response versus time to
any measuring or main acquisition device.
[0095] Further, it could also be used to compensate automatically
any deposits on any probe or window permanently installed
online.
[0096] In a third application (not illustrated), the detector
according to the invention is used to perform flow rate
measurements.
[0097] The detector may be coupled with an isokinetic sampling
device to give in real time the flow rate of each phase flowing in
the sampling pipe.
[0098] Further two or more detectors may be mounted in series in
order to measure a volumetric flow rate, providing that there are
more than one phase present in the flow line. The detectors are
connected to a computer or any other acquisition device which can
perform a cross correlation of the detectors signals and determine
the transit time of each phase from one detector to the other.
These data are subsequently computed to give a measurement of the
volumetric flow rate in the sampling line.
[0099] In the description made hereinbefore, particular multiphase
fluid mixture related to an effluent flowing from a hydrocarbon
well typically comprises three phases has been described. However,
it will be evident for one ordinary skilled in the art that the
invention is also applicable to other kind of multiphase fluid
mixture, for example in the chemical industry or the food
industry.
[0100] Further, examples of internal flowing line dimension were
given in the field of oil industry. However, it will be evident for
one ordinary skilled in the art that this dimension varies
depending on the fluid mixture properties and that this dimension
has to be adapted to maintain the capillarity effect in the
internal flowing line.
[0101] Finally, the term main line use in the present description
has a broad meaning, and covers line having a dimension of a few
centimeters, for example pipeline, sub-sea line, down-hole line,
sampling line, etc. . . .
[0102] The drawings and their description hereinbefore illustrate
rather than limit the invention. Any reference sign in a claim
should not be construed as limiting the claim. The word
"comprising" does not exclude the presence of other elements than
those listed in a claim. The word "a" or "an" preceding an element
does not exclude the presence of a plurality of such elements.
* * * * *