U.S. patent application number 16/792772 was filed with the patent office on 2020-06-11 for method and apparatus for characterizing inorganic scale formation conditions employing a microfludic device.
The applicant listed for this patent is SCHLUMBERGER TECHNOLOGY CORPORATION. Invention is credited to Cedric Floquet, Shahnawaz Molla, Farshid Mostowfi.
Application Number | 20200179922 16/792772 |
Document ID | / |
Family ID | 55304434 |
Filed Date | 2020-06-11 |
United States Patent
Application |
20200179922 |
Kind Code |
A1 |
Molla; Shahnawaz ; et
al. |
June 11, 2020 |
METHOD AND APPARATUS FOR CHARACTERIZING INORGANIC SCALE FORMATION
CONDITIONS EMPLOYING A MICROFLUDIC DEVICE
Abstract
A test method and apparatus employs a microfluidic device to
characterize properties of a fluid. The microfluidic device has an
inlet port, an outlet port, and a microchannel as part of a fluid
path between the inlet port and the outlet port. While a fluid is
introduced into the microchannel, the fluid temperature is
maintained while the fluid pressure in the microchannel is varied
to characterize the properties of the fluid in the microchannel.
The properties of the fluid can relate to a scale onset condition
of the fluid at the pressure of the flow through the microchannel.
In one aspect, fluid pressure in the microchannel is maintained
while the fluid temperature is varied to characterize the
properties of the fluid. In another aspect, flow rate of the fluid
through the microchannel is varied while the fluid temperature is
maintained to characterize the properties of the fluid in the
microchannel.
Inventors: |
Molla; Shahnawaz;
(Watertown, MA) ; Mostowfi; Farshid; (Lexington,
MA) ; Floquet; Cedric; (Cambridge, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SCHLUMBERGER TECHNOLOGY CORPORATION |
Sugar Land |
TX |
US |
|
|
Family ID: |
55304434 |
Appl. No.: |
16/792772 |
Filed: |
February 17, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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15503305 |
Feb 10, 2017 |
10569267 |
|
|
PCT/US2014/050538 |
Aug 11, 2014 |
|
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16792772 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C09K 8/92 20130101; G01N
33/2835 20130101; B01L 3/5027 20130101; B01L 2200/146 20130101;
B01L 2300/1822 20130101; C02F 5/08 20130101; B01L 7/52 20130101;
C09K 8/536 20130101; B01L 2200/147 20130101 |
International
Class: |
B01L 3/00 20060101
B01L003/00; C09K 8/92 20060101 C09K008/92; C09K 8/536 20060101
C09K008/536; C02F 5/08 20060101 C02F005/08; B01L 7/00 20060101
B01L007/00 |
Claims
1. A test method for characterizing properties of a fluid,
comprising: providing a microfluidic device having at least an
inlet port, an outlet port, and a microchannel as part of a fluid
path between the first inlet port and the outlet port; generating a
flow of the fluid through the microchannel at a variable flow rate;
maintaining a temperature of the fluid flowing through the
microchannel; measuring and recording a pressure difference of the
fluid across the microchannel and an average pressure of the fluid
between an inlet and an outlet of the microchannel; evaluating or
analyzing the pressure difference while the flow rate is varied to
determine whether the fluid in the microchannel flowing through the
microchannel exhibits characteristics indicative of the presence of
scale formation.
2. A test method according to claim 1, wherein evaluating or
analyzing the pressure difference includes determining if the
pressure difference varies linearly with the flow rate, wherein, if
it is determined that the pressure difference varies linearly with
the flow rate, then it is further determined that the fluid in the
microchannel does not exhibit characteristics indicative of the
presence of scale formation, and if it is determined that the
pressure difference varies non-linearly with the flow rate, then it
is further determined that the fluid in the microchannel does
exhibit characteristics indicative of the presence of scale
formation.
3. A test method according to claim 2, further comprising
identifying a scale onset pressure where scale begins to form as
the average pressure recorded at a transition point where the
pressure difference transitions between varying linearly and
non-linearly with the flow rate and between varying non-linearly
and linearly with the flow rate.
4. A test method according to claim 3, wherein the fluid includes
at least one of a reservoir fluid, a scale inhibitor, water, and a
gas.
5. A test method for characterizing properties of a fluid,
comprising: providing a microfluidic device having at least an
inlet port, an outlet port, and a microchannel as part of a fluid
path between the first inlet port and the outlet port; introducing
the fluid into the microchannel; maintaining a constant pressure to
the fluid in the microchannel; measuring and recording pressure and
temperature of the fluid in the microchannel; adjusting the
temperature of the fluid in the microchannel; evaluating the fluid
while the temperature of the fluid is adjusted; characterizing
properties of the fluid in the microchannel based on the evaluation
of the fluid.
6. A test method according to claim 5, wherein the properties of
the fluid relate to the scale onset formation condition of the
fluid at the applied pressure and a scale onset temperature.
7. A test method according to claim 6, further comprising repeating
adjusting the temperature of the fluid in the microchannel,
evaluating the fluid while the temperature of the fluid is
adjusted, and characterizing properties of the fluid in the
microchannel based on the evaluation of the fluid until the scale
onset formation condition occurs.
8. A test method according to claim 7, further comprising capturing
images of the fluid in the microchannel.
9. A test method according to claim 8, wherein evaluating the fluid
includes analyzing the captured images in order to determine
whether such images include information that indicates the presence
of scale formation in the fluid in the microchannel.
10. A test method according to claim 9, wherein the fluid
introduced into the microchannel includes at least one of a
reservoir fluid, a scale inhibitor, water, and a gas.
11. A test apparatus for characterizing properties of a fluid,
comprising: a microfluidic device having at least an inlet port, an
outlet port, and a microchannel as part of a fluid path between the
first inlet port and the outlet port; a temperature-controlled
surface that is thermally-coupled to the microfluidic device and
configured to maintain a temperature of the microchannel of the
microfluidic device; at least one temperature sensor for measuring
a temperature characteristic of the microchannel of the
microfluidic device; and means for introducing the fluid into the
microchannel; a pressure sensor configured to measure pressure of
the fluid in the microchannel; means for adjusting the pressure of
the fluid in the microchannel while the temperature characteristic
is maintained for evaluation of the fluid while the pressure is
adjusted to characterize properties of the fluid in the
microchannel based on the evaluation of the fluid.
12. A test apparatus according to claim 11, further comprising a
light source and camera configured to capture images of the
microchannel of the microfluidic device and fluid in the
microchannel.
13. A test apparatus according to claim 12, further comprising:
means for evaluating or analyzing the images captured by the camera
in order to determine whether such images include information that
indicates the presence of scale formation in the fluid that flows
through the microchannel of the microfluidic device at a respective
adjusted pressure; and wherein the means for adjusting the fluid
pressure is constructed to iteratively adjust the fluid pressure
and the means for evaluating or analyzing the images is constructed
to iteratively evaluate the images captured by the camera of the
fluid in the microchannel corresponding to each iterative
adjustment of the fluid pressure.
14. A test apparatus for characterizing properties of a fluid,
comprising: a microfluidic device having at least an inlet port, an
outlet port, and a microchannel as part of a fluid path between the
first inlet port and the outlet port; means for generating a flow
of the fluid through the microchannel at a variable flow rate; a
temperature-controlled surface that is thermally-coupled to the
microfluidic device and configured to maintain a temperature of the
microchannel of the microfluidic device; an inlet pressure sensor
configured to measure an inlet pressure of the fluid at the inlet
of the microchannel; an outlet pressure sensor configured to
measure an outlet pressure of the fluid at the outlet of the
microchannel; measurement and recording means for measuring and
recording a pressure difference between the inlet and outlet
pressures and measuring and recording an average of the inlet and
outlet pressures; means for evaluating or analyzing the pressure
difference while the flow rate is varied to determine whether the
fluid in the microchannel flowing through the microchannel exhibits
characteristics indicative of the presence of scale formation.
15. A test apparatus according to claim 14, wherein the means for
evaluating or analyzing the pressure difference determine if the
pressure difference varies linearly with the flow rate, wherein, if
it is determined that the pressure difference varies linearly with
the flow rate, then it is further determined that the fluid in the
microchannel does not exhibit characteristics indicative of the
presence of scale formation, and if it is determined that the
pressure difference varies non-linearly with the flow rate, then it
is further determined that the fluid in the microchannel does
exhibit characteristics indicative of the presence of scale
formation.
16. A test method according to claim 15, wherein the means for
evaluating or analyzing the pressure difference identify a scale
onset pressure, where scale begins to form, as the average pressure
recorded at a transition point where the pressure difference
transitions between varying linearly and non-linearly with the flow
rate and between varying non-linearly and linearly with the flow
rate.
17. A test apparatus for characterizing properties of a fluid,
comprising: a microfluidic device having at least an inlet port, an
outlet port, and a microchannel as part of a fluid path between the
first inlet port and the outlet port; means for introducing the
fluid into the microchannel; means for maintaining a constant
pressure of the fluid in the microchannel; a temperature-controlled
surface that is thermally-coupled to the microfluidic device and
configured to adjust a temperature of the microchannel of the
microfluidic device; a pressure sensor configured to measure the
pressure of fluid in the microchannel; a temperature sensor
configured to measure the temperature of fluid in the microchannel;
and means for evaluating the fluid while the temperature of the
fluid is adjusted.
18. A test apparatus according to claim 17, wherein the properties
of the fluid relate to the scale onset formation condition of the
fluid at the applied pressure and a scale onset temperature.
19. A test apparatus according to claim 18, wherein the means for
evaluating the fluid include a light source and camera configured
to capture images of the microchannel of the microfluidic device
and fluid in the microchannel.
20. A test method according to claim 19, further comprising means
for characterizing properties of the fluid in the microchannel
based on the evaluation of the fluid, the means constructed to
determine, responsive to analyzing the captured images, whether the
images include information that indicates the presence of scale
formation in the fluid in the microchannel.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 15/503305, filed Aug. 11, 2014 and entitled "METHOD AND
APPARATUS FOR CHARACTERIZING INORGANIC SCALE FORMATION CONDITIONS
EMPLOYING A MICROFLUIDIC DEVICE" which is incorporated herein by
reference in its entirety.
BACKGROUND
Field
[0002] The present application relates to the detection of the
formation of inorganic scale and in particular, but not
exclusively, to the measurement of pressures and corresponding
temperatures at which inorganic scale is found to form.
Related Art
[0003] Inorganic scale (or scale) is a deposit or coating formed on
the surface of metal, rock, or other material. Scale can be caused
by precipitation due to a chemical reaction with the surface of
such materials, by precipitation caused by chemical reactions in
the fluid, by a change in pressure or temperature, and by a change
in the composition of the fluid. Common scales are calcium
carbonate, calcium sulfate, barium sulfate, strontium sulfate, iron
sulfide, iron oxides, iron carbonate, the various silicates and
phosphates and oxides, or any of a number of compounds insoluble or
slightly soluble in water.
[0004] Scale formation is of interest in the petroleum industry,
particularly with respect to producing, transporting, and
processing of natural gas and petroleum fluids. In the case of oil
and gas wells, scale may occur on wellbore tubulars and components
as the saturation of produced water is affected by changing
temperature and pressure conditions in the production conduit. In
severe conditions, scale creates a significant restriction, or even
a plug, in the wellbore tubulars. For example, damage due to
inorganic scale formation in a well, formation, or reservoir during
water injection at high pressure and high temperature (HPHT)
conditions is a challenge to the petroleum industry. Scale removal
is a common well intervention operation, with a wide range of
mechanical, chemical, and scale inhibitor treatment options
available. However, remediation and cleaning of water scales costs
the petroleum industry millions of dollars each year.
[0005] At present, no standard laboratory test is available to
accurately detect and measure the scale onset condition at
reservoir conditions (which is often at high pressure and high
temperature). Although, the thermodynamic models for scale
prediction are well known and reliable, these models require very
accurate composition of the water samples at reservoir conditions
as primary input. However, acquiring a representative sample of the
formation water to measure composition with a high degree of
accuracy is a significant challenge; specifically when the sample
must be transported to the laboratory in a pressurized container.
Quite often the sample integrity is compromised due to changes in
pressure and temperature as well as compositional variation during
transportation. Hence, it is important to measure the scale
formation condition of the sample immediately after the sample is
collected, for example at the wellsite.
SUMMARY
[0006] This summary is provided to introduce a selection of
concepts that are further described below in the detailed
description. This summary is not intended to identify key or
essential features of the claimed subject matter, nor is it
intended to be used as an aid in limiting the scope of the claimed
subject matter.
[0007] Illustrative embodiments of the present disclosure are
directed to a test method and a test apparatus that employs a
microfluidic device to characterize properties of a fluid. The test
method and apparatus are useful in studying the effects of
different formation injection additives on the particular reservoir
fluid for different flow pressures and/or additive concentrations
as desired. Such operations can be used to optimize a strategy for
reservoir fluid production and/or transportation that minimizes the
formation of scale during these processes.
[0008] In a first aspect, a test method is described for
characterizing properties of a fluid. A microfluidic device is
provided having at least an inlet port, an outlet port, and a
microchannel as part of a fluid path between the inlet port and the
outlet port. The fluid is introduced into the microchannel and the
fluid is maintained at a constant temperature in the microchannel.
The fluid is evaluated while the pressure of the fluid in the
microchannel is adjusted. A property of the fluid in the
microchannel is characterized based on the evaluation of the fluid.
The property of the fluid may relate to a scale onset pressure,
which is the pressure of the fluid when scale begins to form. The
adjustment of the pressure, the evaluation of the fluid, and the
fluid characterization may be repeated until a scale onset
formation condition occurs.
[0009] Also, in one embodiment, images of the fluid in the
microchannel may be captured. The evaluation of the fluid may
include an analysis of the captured images in order to determine
whether such images include information that indicates the presence
of scale formation in the fluid in the microchannel.
[0010] In a second aspect, a test method is described for
characterizing properties of a fluid. A microfluidic device is
provided having at least an inlet port, an outlet port, and a
microchannel as part of a fluid path between the inlet port and the
outlet port. A flow of the fluid is generated through the
microchannel at a variable flow rate and a temperature of the fluid
flowing through the microchannel is maintained. A pressure
difference of the fluid across the microchannel and an average
pressure of the fluid between an inlet and an outlet of the
microchannel are measured and recorded. The pressure difference is
evaluated or analyzed while the flow rate is varied to determine
whether the fluid in the microchannel flowing through the
microchannel exhibits characteristics indicative of the presence of
scale formation.
[0011] In one embodiment, the evaluation or analysis of the
pressure difference includes determining if the pressure difference
varies linearly with the flow rate, wherein, if it is determined
that the pressure difference varies linearly with the flow rate,
then it is further determined that the fluid in the microchannel
does not exhibit characteristics indicative of the presence of
scale formation, and if it is determined that the pressure
difference varies non-linearly with the flow rate, then it is
further determined that the fluid in the microchannel does exhibit
characteristics indicative of the presence of scale formation.
[0012] In one embodiment, scale onset pressure is identified as the
average pressure recorded at a transition point where the pressure
difference transitions between varying linearly and non-linearly
with the flow rate and between varying non-linearly and linearly
with the flow rate. The fluid includes at least one of a reservoir
fluid, a scale inhibitor, water, and a gas.
[0013] According to a third aspect, a test apparatus is described
for characterizing properties of a fluid. The apparatus includes a
microfluidic device having at least an inlet port, an outlet port,
and a microchannel as part of a fluid path between the inlet port
and the outlet port. The apparatus also includes a
temperature-controlled surface that is thermally-coupled to the
microfluidic device and configured to maintain a temperature of the
microchannel of the microfluidic device. Also, the apparatus
includes at least one temperature sensor for measuring a
temperature characteristic of the microchannel of the microfluidic
device. Further the apparatus includes means for introducing the
fluid into the microchannel, and a pressure sensor configured to
measure pressure of the fluid in the microchannel. In addition, the
apparatus includes means for adjusting the pressure of the fluid in
the microchannel while the temperature characteristic is maintained
for evaluation of the fluid while the pressure is adjusted to
characterize properties of the fluid in the microchannel based on
the evaluation of the fluid.
[0014] In one embodiment, the apparatus includes a light source and
camera configured to capture images of the microchannel of the
microfluidic device and fluid in the microchannel. Also, in one
embodiment, the test apparatus includes means for evaluating or
analyzing the images captured by the camera in order to determine
whether such images include information that indicates the presence
of scale formation in the fluid that flows through the microchannel
of the microfluidic device at a respective adjusted pressure. The
means for adjusting the fluid pressure is constructed to
iteratively adjust the fluid pressure and the means for evaluating
or analyzing the images is constructed to iteratively evaluate the
images captured by the camera of the fluid in the microchannel
corresponding to each iterative adjustment of the fluid
pressure.
[0015] In a fourth aspect, a test apparatus is described for
characterizing properties of a fluid. The apparatus includes a
microfluidic device having at least an inlet port, an outlet port,
and a microchannel as part of a fluid path between the inlet port
and the outlet port. The apparatus includes means for generating a
flow of the fluid through the microchannel at a variable flow rate.
Also, the apparatus includes a temperature-controlled surface that
is thermally-coupled to the microfluidic device and configured to
maintain a temperature of the microchannel of the microfluidic
device. The apparatus includes an inlet pressure sensor configured
to measure an inlet pressure of the fluid at the inlet of the
microchannel, and an outlet pressure sensor configured to measure
an outlet pressure of the fluid at the outlet of the microchannel.
Further, the apparatus includes measurement and recording means for
measuring and recording a pressure difference between the inlet and
outlet pressures and measuring and recording an average of the
inlet and outlet pressures. In addition, the apparatus includes
means for evaluating or analyzing the pressure difference while the
flow rate is varied to determine whether the fluid in the
microchannel flowing through the microchannel exhibits
characteristics indicative of the presence of scale formation.
[0016] In one embodiment, the means for evaluating or analyzing
determine if the pressure difference varies linearly with the flow
rate, wherein, if it is determined that the pressure difference
varies linearly with the flow rate, then it is further determined
that the fluid in the microchannel does not exhibit characteristics
indicative of the presence of scale formation, and if it is
determined that the pressure difference varies non-linearly with
the flow rate, then it is further determined that the fluid in the
microchannel does exhibit characteristics indicative of the
presence of scale formation. Also, in one embodiment, the means for
evaluating or analyzing identify a scale onset pressure, where
scale begins to form, as the average pressure recorded at a
transition point where the pressure difference transitions between
varying linearly and non-linearly with the flow rate and between
varying non-linearly and linearly with the flow rate.
[0017] In a fifth aspect, a test method is described for
characterizing properties of a fluid. A microfluidic device is
provided having at least an inlet port, an outlet port, and a
microchannel as part of a fluid path between the inlet port and the
outlet port. The fluid is introduced into the microchannel and the
fluid in the microchannel is maintained at a constant pressure. The
pressure and temperature of the fluid in the microchannel are
measured and recorded. Properties of the fluid in the microchannel
are characterized based on evaluation of the fluid while the
temperature of the fluid in the microchannel is adjusted. The
properties of the fluid may relate to the scale onset temperature,
which is the temperature when scale begins to form. The adjustment
of the temperature, the evaluation of the fluid, and the
characterization of the properties of the fluid may be repeated
until the scale onset formation condition occurs.
[0018] In one embodiment, images of the fluid in the microchannel
are captured. Evaluation of the fluid may include an analysis of
the captured images in order to determine whether such images
include information that indicates the presence of scale formation
in the fluid in the microchannel.
[0019] In a sixth aspect, a test apparatus is described for
characterizing properties of a fluid. The apparatus includes a
microfluidic device having at least an inlet port, an outlet port,
and a microchannel as part of a fluid path between the inlet port
and the outlet port. The apparatus includes means for introducing
the fluid into the microchannel, means for maintaining a constant
pressure of the fluid in the microchannel, and a
temperature-controlled surface that is thermally-coupled to the
microfluidic device and configured to adjust a temperature of the
microchannel of the microfluidic device. Also, the apparatus
includes a pressure sensor configured to measure the pressure of
fluid in the microchannel, a temperature sensor constructed to
measure the temperature of fluid in the microchannel, and means for
evaluating properties of the fluid while the temperature of the
fluid is adjusted. In one embodiment, properties of the fluid
relate to scale onset temperature.
[0020] Also, in one embodiment, the test apparatus can include a
light source and camera configured to capture images of the
microchannel of the microfluidic device and fluid in the
microchannel. Further, the test apparatus may include means for
characterizing properties of the fluid in the microchannel based on
the evaluation of the fluid, the means constructed to determine,
responsive to analyzing the captured images, whether the images
include information that indicates the presence of scale formation
in the fluid in the microchannel.
[0021] The fluid introduced into the microchannel can include at
least one of a reservoir fluid, a scale inhibitor, a water-based
fluid (such as seawater, freshwater, or steam), and a gas.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a schematic diagram of a test apparatus according
to an embodiment of the present disclosure.
[0023] FIG. 2 is a schematic top view of another embodiment of a
microfluidic device that can be used as part of the test apparatus
of FIG. 1.
[0024] FIG. 3 is a schematic cross-sectional view of an embodiment
of the microfluidic device of FIG. 1 or FIG. 2 in conjunction with
a temperature-controlled heating-cooling surface that is placed in
thermal contact with the microfluidic device.
[0025] FIG. 4 is a schematic diagram showing scale deposited inside
the microchannel of the microfluidic device of FIG. 1 during
operation of the test apparatus.
[0026] FIG. 5 is a flow chart describing a sequence of test
operations carried out by the test apparatus of FIG. 1 to
characterize properties related to scale onset formation conditions
of fluid that flows through the microchannel of the microfluidic
device.
[0027] FIG. 6 is a flow chart describing a sequence of test
operations carried out by the test apparatus of FIG. 1 to
characterize properties related to scale onset formation conditions
of fluid that flows through the microchannel of the microfluidic
device.
[0028] FIG. 7 is a flow chart describing another sequence of test
operations carried out by the test apparatus of FIG. 1 to
characterize properties related to scale onset formation conditions
of fluid that flows through the microchannel of the microfluidic
device.
[0029] FIG. 8 is a schematic diagram of a test apparatus according
to an embodiment of the present disclosure, where a fluid that
includes a reservoir fluid component and possibly an additive flows
through the microchannel of the microfluidic device during
operation of the test apparatus. In this case, the test apparatus
can be used to characterize properties related to scale onset
formation conditions of the fluid that flows through the
microchannel of the microfluidic device.
DETAILED DESCRIPTION
[0030] Illustrative embodiments of the present disclosure are
described below. In the interest of clarity, not all features of an
actual implementation are described in this specification. It will
be appreciated that in the development of any such actual
embodiment numerous implementation-specific decisions must be made
to achieve the developer's specific goals, such as compliance with
system-related and business-related constraints, which will vary
from one implementation to another. Moreover, it will be
appreciated that such a development effort might be complex and
time-consuming but would nevertheless be a routine undertaking for
those of ordinary skill in the art having the benefit of this
disclosure. Further, like reference numbers and designations in the
various drawings indicate like elements.
[0031] For the purposes of this disclosure, the term "reservoir
fluid" means a fluid stored in or transmitted from a subsurface
body of permeable rock. Thus "reservoir fluid" may include, without
limitation, hydrocarbon fluids, saline fluids such as saline water,
as well as other formation water, and other fluids such as carbon
dioxide in a supercritical phase.
[0032] Moreover, for the purposes of this disclosure, the term
"microfluidic device" means a device having a fluid-carrying
channel exhibiting a width within a range of tens to hundreds of
micrometers, but exhibiting a length that is many times longer than
the width of the channel. Similarly the term "microchannel" means a
fluid-carrying channel exhibiting a width within a range of tens to
hundreds of micrometers. Although many of the microchannels
described herein are of rectangular cross-section due to the
practicalities of fabrication techniques, the cross-section of a
microchannel can be of any shape, including round, oval, ellipsoid,
square, etc.
[0033] A microfluidic device employs one or more microchannels
(capillaries) where the surface area in contact with fluid flowing
in the microchannel is relatively large compared to the volume of
the fluid flowing through the microchannel. As a result, the heat
transfer between the sample and its surroundings is rapid and the
temperature of the fluid in the microchannel can be changed
rapidly. Also, due to the small dimensions of the microchannel, the
sample volume required in the microfluidic device amounts to a few
micro-liters of liquid. For example, the size of a microchannel's
cross-section is on the order of the length scale of reservoir
pores (10 to 100 microns).
[0034] Therefore, the testing methods and apparatus described
herein utilize a microfluidic device for rapid and accurate
detection of scale formed in a fluid sample flowing through the
microfluidic device, the temperature of which can be precisely
controlled and maintained. The pressure-driven flow of the fluid
sample in the microfluidic device is monitored using pressure
sensors to identify properties of the scale formation condition (or
the scale redissolution condition).
[0035] As shown in FIG. 1, a test apparatus 100 includes a
microfluidic device 101 that includes a first inlet port 103, a
second inlet port 105, and an outlet port 107. The microfluidic
device 101 also includes an internal mixing section 109 (which can
be a t-junction as shown) that is fluidly coupled to both the first
inlet port 103 and the second inlet port 105 as well as to a
microchannel 111 that extends between the mixing section 109 and
the outlet port 107. The mixing section 109 can be of various forms
and shapes, such as the active and passive mixers commonly used in
microfluidic applications. The mixing section 109 can also be
external to the microfluidic device 101. In the embodiment shown in
FIG. 1, the microchannel 111 can form a serpentine pattern, thus
allowing the microchannel 111 to extend a significant length but
occupy a relatively small area. For example, the length of the
serpentine pattern can be 1.7 meters. In another embodiment shown
in FIG. 2, the microchannel 111 can extend in a linear manner
between the mixing section 109 and the outlet port 107. In both the
serpentine and straight microchannel configurations, the
microchannel 111 has a uniform rectangular cross-section, which, in
one embodiment, has a width of about 100 micrometers and a height
of about 50 micrometers. However, other geometric shapes and
dimensions could also be used. The microfluidic devices can be made
from BOROFLOAT.RTM. glass (available from SCHOTT North America,
Inc. of Louisville, Ky., USA) and silicon using standard
micro-fabrication processes.
[0036] In one embodiment shown in FIG. 3, the mixing section 109
and the microchannel 111 of the microfluidic device 101 can be
defined by etching the planar surface of a first substrate 122. The
first substrate 122 can be made of silicon (e.g., a conventional
silicon-on-insulator wafer) or other suitable material. A second
substrate 153 can be sealably bonded to the planar surface of the
first substrate 122 that has been etched to form the mixing section
109 and the microchannel 111. The bonding can employ an anodic
bonding method after careful cleaning of the bonding surfaces of
the first and second substrates 122, 153. The first substrate 122
or the second substrate 153 can define the first and second inlet
ports 103, 105 and the outlet port 107 that are in fluid
communication with the mixing section 109 and the microchannel 111.
The second substrate 153 can be made of glass, such as borosilicate
glass (such as BOROFLOAT.RTM. glass) or other suitable material.
The flow paths of the mixing section 109 and the microchannel 111
can have uniform rectangular cross-sections formed in the first
substrate as shown in FIG. 3. In one example, such rectangular
cross-sections have a width (W) of 100 .mu.m and a height (H) of 50
.mu.m. However, the cross-sections can have other geometric shapes
as desired.
[0037] The microfluidic device 101 can be supported by (or
otherwise thermally coupled to) a temperature-controlled
cooling/heating surface 135 that provides for temperature control
of the microfluidic device 101 (including the microchannel 111
therein) independent of the temperature of the rest of the
apparatus.
[0038] Turning back to FIG. 1, the test apparatus 100 also includes
an electrically-controlled reservoir and pump 113 that are loaded
with a quantity of the reservoir fluid sample that contains one or
more components that can precipitate out as scale. The reservoir
and pump 113 have an outlet that is fluidly coupled to an
electrically-controlled valve 115. The reservoir and pump 113 and
the valve 115 are operated to introduce the reservoir fluid (for
example, at or near a constant flow rate) into the first inlet port
103 of the microfluidic device 101. A pressure sensor 117 (such as
the Sensotreme sensor available from Sensotreme GmbH of Ramsen,
Switzerland) is disposed within the supply line 119 between the
valve 115 and the first inlet port 103 in order to monitor the
pressure of the fluid sample in the supply line 119. The reservoir
and pump 113 can be an electrically-controlled syringe pump, such
as the ISCO 65D pump available from Teledyne Technologies Inc. of
Lincoln, Nebr., USA. The supply line 119 can include an in-line
filter that removes particulate matter that could potentially clog
the microchannel 111 of the microfluidic device 101. The reservoir
and pump 113, the valve 115, and the supply line 119 can all
operate at or near ambient temperature.
[0039] The test apparatus 100 also includes an
electrically-controlled reservoir and pump 121 that are loaded with
a quantity of liquid or possibly a gas. The liquid or gas can be a
water-based fluid (such as produced water, flowback water, connate
(formation) water, cross-linkers, gelling agents, fluid loss
additives, thermal stabilizers, breakers, biocides, stabilizers,
surfactants, clay controllers, scale inhibitors, fracturing polymer
solutions, seawater, fresh water, steam, injection gas, brine
solution as completion fluid, or fracturing fluid which may be
acid-based fluids or multiphase fluids (emulsions, foams,
energized)) that can be used to stimulate production of the
reservoir fluid loaded into the reservoir and pump 113. The
reservoir and pump 121 have an outlet that is fluidly coupled to an
electrically-controlled valve 123. The reservoir and pump 121 and
the valve 123 are operated to introduce the liquid or gas (for
example, at or near a constant flow rate) into the second inlet
port 105 of the microfluidic device 101. A pressure sensor 125
(such as a Sensotreme sensor) is disposed within the supply line
127 between the valve 123 and the second inlet port 105 in order to
monitor the pressure of the test sample fluid in the supply line
127. The reservoir and pump 121 can be an electrically-controlled
syringe pump, such as the ISCO 65D pump. The supply line 127 can
include an in-line filter that removes particulate matter that
could potentially clog the microchannel 111 of the microfluidic
device 101. The reservoir and pump 121, the valve 123, and the
supply line 127 can all operate at or near ambient temperature.
[0040] An optional pressure sensor 155 (such as a Sensotreme
sensor) is fluidly connected between the mixing section 109 and the
microchannel 111 in order to monitor the pressure of fluid entering
the microchannel 111. While the fluid pressure at the inlet of the
microchannel 111 can be directly obtained using pressure sensor
155, such a pressure measurement may also be obtained using a
combination of pressure measurements obtained using sensors 117 and
125. For example, instead of using sensor 155 to measure the fluid
pressure at the inlet of the microchannel 111, it is possible to
approximate the inlet pressure using the average of the pressures
obtained using sensors 117 and 125.
[0041] The outlet port 107 of the microfluidic device 101 is
fluidly coupled to a collection chamber with a pump 129. The pump
129 can be controlled to apply a back pressure to the microchannel
107 to maintain a constant pressure at the inlet 109 of the
microchannel 111. A pressure sensor 131 (such as a Sensotreme
sensor) is disposed within an outlet line 133 between the outlet
port 107 and the pump 129 in order to monitor the pressure of the
fluid flowing in the outlet line 133.
[0042] Temperature sensors 137 and 139 are connected to
microchannel 111. Sensor 137 is connected upstream of sensor 139.
The temperature sensors 137 and 139 can be used to monitor the
temperature of the microchannel 111 of the microfluidic device 101.
The temperature sensors 137 and 139 can be thermocouples, such as
the Omega 5TC-TT-K 40-36 thermocouple available from Omega
Engineering Inc. of Laval, Quebec, Canada. The
temperature-controlled cooling/heating surface 135 (FIG. 3) can be
used to control the temperature of specific sections of the
microchannel 111 instead of the entire microfluidic device 101. In
this case, the temperature sensors 137 and 139 can be used to
measure the temperature gradient along the sections of the
microchannel 111 for control of the temperature gradient by
cooling/heating surface 135. The temperature-controlled
cooling/heating surface 135 can be a thermo-electric plate, such as
a TEC model TC-36-25 RS485, available from TE Technology, Inc. of
Traverse City, Mich., USA.
[0043] A light source 141 and a camera 143 can be arranged to
capture high-resolution images of the microchannel 111 of the
microfluidic device 101 in order to detect the presence (or
absence) of scale in the microchannel 111 as described below.
[0044] The test apparatus 100 also includes a controller and/or
computer processing system 145 that includes control logic that
interfaces to the electrically-controlled reservoir and pumps 113
and 121 and pump 129 via wired or wireless signal paths
therebetween for control of the operation of the pumps 113, 121,
and 129 that interfaces to the electrically-controlled valves 115
and 123 via wired or wireless signal paths therebetween for control
of the operation of the valves 115 and 123, that interfaces to the
temperature-controlled cooling/heating surface 135 via wired or
wireless signal paths therebetween in order to provide for
temperature control of the microfluidic device 101 (or the
microchannel 111 or portions thereof), that interfaces to the
pressure sensors 117, 125, 131, and 155 via wired or wireless
signal paths therebetween for pressure measurements and recordation
of such pressure measurements during operation of the test
apparatus 100, and that interfaces to the temperature sensors 137
and 139 via wired or wireless signal paths therebetween for
temperature measurements and recordation of such temperature
measurements during operation of the test apparatus 100. The
controller and/or computer processing system 145 can also interface
to the light source 141 and/or to the camera 143 via wired or
wireless signal paths therebetween in order to capture high
resolution images of the microchannel 111 and for recordation of
such high resolution images and possibly display of such high
resolution images during operation of the test apparatus 100. The
control logic of the controller and/or computer processing system
145 (which can be embodied in software that is loaded from
persistent memory and executed in the computing platform of the
computer processing system 145) is configured to control the
different parts of the test apparatus 100 to carry out a sequence
of operations (workflow) that characterizes properties related to
scale formation conditions (such as the scale formation temperature
and pressure) of the fluid that is introduced into the microchannel
111 of the microfluidic device 101 as described below. The control
logic can be configured by user input or a testing script or other
suitable data structure, which is used to configure the controller
or the computer processing system 145 in order to carry out control
operations that are part of the workflow as described herein. For
example, the user input or the testing script or other suitable
data structure can specify parameters (such as pressures, flow
rates, temperatures, etc.) for such control operations of the
workflow.
[0045] An embodiment of a workflow is illustrated in the flow chart
of FIG. 5. At 500 the workflow begins and it is assumed that the
reservoir and pump 113 are filled with a sufficient quantity of the
reservoir fluid sample that contains dissolved scaling chemical
species and the reservoir and pump 121 are filled with a sufficient
quantity of liquid or gas. The liquid or gas is a fluid to be
injected into the petroleum reservoir or added to the produced
fluid to test compatibility with the reservoir fluid and/or its
effectiveness in preventing or reducing scale formation. For
example, in a mitigation scenario, the type and relative
concentration of the fluid can mimic a production environment in
cases where a defined problem is arising. In a prevention scenario,
prior analysis of the reservoir fluids and conditions indicate the
type and formation path of potential scaling. A bespoke fluid would
be prepared and its effectiveness tested, most likely in an
iterative process. In some tests only the reservoir fluid sample
from reservoir 113 is tested for scale onset and no liquid or gas
is injected by pump 121.
[0046] At 501 the test apparatus is initialized so that reservoir
and pump 113 and the corresponding valve 115 are controlled to
introduce the reservoir fluid into the inlet port 103 of the
microfluidic device 101 while the reservoir and pump 121 and the
corresponding valve 123 are controlled to introduce the liquid or
gas into the inlet port 105 of the microfluidic device 101. The
pumping rates for the pumps 113 and 121 are configured such that
the reservoir fluid and the liquid or gas are supplied to the inlet
ports 103 and 105 at a fixed proportion. That is, the flow rates
for the reservoir fluid and the liquid or gas establish the
relative volume ratio of reservoir fluid to liquid or gas for the
test. The flow rates, and thus the resultant relative volume ratios
of reservoir fluid to liquid or gas, can be varied over multiple
iterations of the test as desired.
[0047] The reservoir fluid and liquid or gas supplied to the inlet
ports 103 and 105 are co-flowing fluids that flow to the mixing
section 109 of the microfluidic device 101. The reservoir fluid and
the liquid or gas are mixed in the mixing section 109 and can exit
the mixing section 109 as a homogeneous fluid mixture. Due to the
large surface-to-volume ratio of the microchannel 111, the flow of
the mixture through the microchannel 111 exhibits excellent mass
transfer between the co-flowing fluids. The mixture exits the
microchannel 111 and flows out the outlet port 107 of the
microfluidic device 101 to the collection chamber and pump 129 via
the outlet line 133. The collection chamber and pump 129 is
controlled to regulate a pressure of the mixture in the
microchannel 111 to a pressure that varies during operations in 505
and 507.
[0048] In 503, the temperature of the fluid flow through the
microchannel 111 is maintained at the reservoir temperature TR.
Also, the inlet pressure P.sub.4 of the fluid is initially
maintained at or close to reservoir pressure PR and is regulated by
the collection chamber and pump 129. The reservoir pressure
condition, at the reservoir temperature, is above the scale onset
pressure.
[0049] The workflow carries out a sequence of operations in 505 and
507 that vary the pressure of the mixture in the microchannel 111
in order to determine properties related to the scale onset
formation condition for the mixture. In each of 505 and 507, the
temperature of the mixture in the microchannel 111 is controlled by
maintaining the temperature of the microchannel 111 via temperature
control of the temperature-controlled cooling/heating surface 135.
The temperature is maintained substantially constant near the
reservoir temperature, T.sub.R. As mentioned earlier, temperature
equilibration in the microchannel 111 can be achieved quickly due
to the availability of a relatively large surface area as well as
relatively small fluid volume of the microchannel 111. During the
operation of 505 and 507, pressures P.sub.1, P.sub.2, P.sub.3, and
P.sub.4 are measured, respectively, by the pressure sensors 117,
125, 131, and 155 and recorded by the computer processing system
145, and temperatures T.sub.1 and T.sub.2 are measured by the
temperature sensors 137 and 139 and recorded by the computer
processing system 145. Such pressures and temperatures can also be
displayed on a graph relative to time for user evaluation, if
desired. Such pressures and temperatures can also be stored in the
memory system of the computer processing system 145 for automated
data analysis if desired.
[0050] In 505, after a time period where the inlet pressure P.sub.4
reaches a steady state value, and the temperatures T.sub.1 and
T.sub.2 reach steady state values near the reservoir temperature
TR, the flow of the mixture stops, valves 115 and 123 are closed,
and a fixed volume of the mixture is isolated in the microchannel
111. The static pressure of the mixture in the
temperature-controlled section of the microchannel 111, as measured
by P.sub.3, is reduced in a discrete step, Pstep, by action of the
collection chamber and pump 129. The pressure step, Pstep, selected
may be based on an approximation based on a theoretical model of
scale formation or prior testing with the test apparatus. Also, the
pressure step, Pstep, can be any numerical amount that is not
related to modeling or empirical testing.
[0051] In 507, the microchannel 111 is visually monitored with the
camera 143 based on real time image analysis. FIG. 4 is a schematic
representation of scale formed in the microchannel 111. The light
source 141 and the camera 143 can be used to capture one or more
high resolution images of the microchannel 111 as part of the
evaluation of 507. Such image(s) can be displayed by the computer
processing system 145 for evaluation by the operator/user to
ascertain if scale is present in the image(s). Precipitates of
scale will crystalize on the microchannel 111 surfaces if the
reduced pressure is below the scale onset pressure. If the visual
check of the microchannel 111 does not indicate scale formation (NO
at 507), then the pressure is reduced again by Pstep at 505 and the
microchannel 111 is checked again at 507. If the visual check of
the microchannel 111 indicates that scale is formed (YES at 507),
then testing ends at 509. The pressure in the microchannel 111
during the iteration of 505 and 507 when scale is indicated (YES at
507) corresponds to the scale onset pressure at the temperature in
the microchannel 111, which in the example mentioned above, is at
the reservoir temperature TR.
[0052] Note that the evaluation of 507 can be carried out by visual
interpretation of the images of the microchannel 111 by an
operator/user. For fully-automated and semi-automated
implementations of the workflow, such evaluation can also involve
image processing of the image(s) of the microchannel 111 that is
carried out by the computer processing system 145 in order to
detect the presence (or absence) of scale in the microchannel
111.
[0053] The workflow shown in FIG. 5 can be repeated multiple times
using different Pstep values in order to determine the scale onset
pressure. It will be appreciated that larger Pstep values may
reduce the number of iterations of 505 and 507 before determining
the scale onset pressure, while smaller Pstep values may increase
the number of iterations of 505 and 507 before determining the
scale onset pressure. Moreover, it will be appreciated that larger
Pstep values may yield a determination of scale onset pressure that
is less accurate than if smaller Pstep values are used. Thus, there
may be a tradeoff in the workflow between duration of the testing
and accuracy of the result in that smaller Pstep increments may
require more iterations and, thus, a longer workflow, while
providing a more accurate determination of the scale onset
pressure, whereas larger Pstep increments may require less
iterations and, thus, a shorter workflow, while providing a less
accurate (rough estimate) determination of the scale onset
pressure. Also, the workflow can be repeated multiple times with
different volume ratios of the reservoir fluid to the liquid or gas
in order to determine the scale onset pressure of the fluid flow
for the different ratios.
[0054] Another embodiment of a workflow is illustrated in the flow
chart of FIG. 6. At 602 the workflow begins and it is assumed that
the reservoir and pump 113 are filled with a sufficient quantity of
the reservoir fluid sample that contains dissolved scaling chemical
species and the reservoir and pump 121 are filled with a sufficient
quantity of the liquid or gas to be tested.
[0055] At 604 the test apparatus is initialized so that reservoir
and pump 113 and the corresponding valve 115 are controlled to
introduce the reservoir fluid into the inlet port 103 of the
microfluidic device 101 while the reservoir and pump 121 and the
corresponding valve 123 are controlled to introduce the liquid or
gas into the inlet port 105 of the microfluidic device 101. During
the operation of 604, pressures P.sub.1, P.sub.2, P.sub.3, and
P.sub.4 are measured, respectively, by the pressure sensors 117,
125, 131, and 155 and recorded by the computer processing system
145, and temperatures T.sub.1 and T.sub.2 are measured by the
temperature sensors 137 and 139 and recorded by the computer
processing system 145. Such pressures and temperatures can also be
displayed on a graph relative to time for user evaluation, if
desired. Such pressures and temperatures can also be stored in the
memory system of the computer processing system 145 for automated
data analysis if desired.
[0056] The pumping rates for the pumps 113 and 121 are configured
such that the reservoir fluid and the liquid or gas are supplied to
the inlet ports 103 and 105 in a fixed proportion. That is, the
flow rates for the reservoir fluid and the liquid or gas establish
the relative volume ratio of reservoir fluid to liquid or gas for
the test. The flow rates, and thus the resultant relative volume
ratios of reservoir fluid to liquid or gas, can be varied over
multiple iterations of the test as desired. The reservoir fluid and
liquid or gas that are supplied to the inlet ports 103 and 105 are
co-flowing fluids that flow to the mixing section 109 of the
microfluidic device 101, which can form a homogeneous mixture. The
resultant fluid mixture of the reservoir fluid and the liquid or
gas flows through the microchannel 111 of the microfluidic device
101. Due to the large surface-to-volume ratio of the microchannel
111, the flow through the microchannel 111 exhibits excellent mass
transfer between the co-flowing fluids. The fluid mixture exits the
microchannel 111 and flows out the outlet port 107 of the
microfluidic device 101 to the collection chamber and pump 129 via
the outlet line 133. The collection chamber and pump 129 are
controlled to regulate (such as by applying a back pressure) the
pressure of the mixture in microchannel 111.
[0057] At 606, the temperature of the mixture in the microchannel
is regulated to be at or close to the reservoir temperature
T.sub.R, while the inlet pressure P.sub.4 of the mixture is
regulated to be at or close to the reservoir pressure P.sub.R.
[0058] A sequence of operations in 608 and 610 checks whether scale
is formed at various fluid temperatures while the fluid pressure of
the mixture is maintained at reservoir pressure. More specifically,
the temperature of the fluid in the microchannel 111 is iteratively
decreased in order to determine properties related to the scale
onset formation temperature at the reservoir pressure for the fluid
mixture in the microchannel 111. In each of the 608 and 610, the
temperature of the bulk or mixed fluid flow in the microchannel 111
is controlled via temperature control of the temperature-controlled
cooling/heating surface 135. As mentioned earlier, temperature
equilibration in the microchannel 111 can be achieved quickly due
to the availability of large surface area as well as small fluid
volume of the microchannel 111.
[0059] In 608, after a time period where the inlet pressure P.sub.4
reaches a steady state value, and the temperatures T.sub.1 and
T.sub.2 reach steady state values near the reservoir temperature
T.sub.R, the flow of the mixture stops, valves 115 and 123 are
closed, and a resulting fixed volume of the fluid is isolated in
the microchannel 111. The pressure of the fixed volume of fluid in
the microchannel 111 (as measured by any of pressure sensors 117,
125, 131, and 155 since pressure is static) is maintained by
control of the collection chamber and pump 129. While the fluid
pressure in microchannel 111 is maintained constant, the
temperature of the fluid in microchannel 111 is decreased by a
predetermined amount (Tstep) by control of the
temperature-controlled cooling/heating surface 135. The temperature
step, Tstep, selected may be based on an approximation informed by
a theoretical model of scale formation or prior testing with the
test apparatus. Also, the temperature step, Tstep, can be any
numerical amount that is not related to modeling or empirical
testing.
[0060] In 610, the microchannel 111 is visually monitored with the
camera 143 based on real time image analysis. FIG. 4 is a schematic
representation of scale formed in the microchannel 111. The light
source 141 and the camera 143 can be used to capture one or more
high resolution images of the microchannel 111 as part of the
evaluation of 610. Such image(s) can be displayed by the computer
processing system 145 for evaluation by the operator/user to
ascertain if scale is present in the image(s). Precipitates of
scale will crystalize on the microchannel 111 surfaces if the
reduced temperature is below the scale onset temperature. If the
visual check of the microchannel 111 does not indicate scale
formation (NO at 610), the temperature is reduced again by Tstep at
608 and the microchannel 111 is checked again at 610. If the visual
check of the microchannel 111 indicates that scale is formed (YES
at 610), testing ends at 612. The temperature in microchannel 111,
which can be approximated to be the average of T.sub.1 and T.sub.2,
during the iteration of 608 and 610 when scale is indicated (YES at
610) corresponds to the scale onset temperature at the pressure in
the microchannel 111, which in the example mentioned above, is at
the reservoir pressure.
[0061] Note that the evaluation of 610 can be carried out by visual
interpretation of the images of the microchannel 111 by an
operator/user. For fully-automated and semi-automated
implementations of the workflow, such evaluation can also involve
image processing of the image(s) of the microchannel 111 that is
carried out by the computer processing system 145 in order to
detect the presence (or absence) of scale in microchannel 111.
[0062] Note that the workflow shown in FIG. 6 can be repeated
multiple times using different Tstep values in order to determine
the scale onset temperature. It will be appreciated that larger
Tstep values may reduce the number of iterations of 608 and 610
before determining the scale onset temperature, while smaller Tstep
values may increase the number of iterations of 608 and 610 before
determining the scale onset temperature. Moreover, it will be
appreciated that larger Tstep values may yield a determination of
scale onset temperature that is less accurate than if smaller Tstep
values are used. Thus, there may be a tradeoff in the workflow
between duration of the testing and accuracy of the result in that
smaller Tstep increments may require more iterations and, thus, a
longer workflow, while providing a more accurate determination of
the scale onset temperature, whereas larger Tstep increments may
require fewer iterations and, thus, a shorter workflow, while
providing a less accurate (rough estimate) determination of the
scale onset temperature. Also, the workflow can be repeated
multiple times with different volume ratios of the reservoir fluid
to the liquid or gas in order to determine the scale onset
temperature of the fluid flow for the different ratios.
[0063] In the workflows described with respect to FIGS. 5 and 6,
the flow of the fluid mixture in the microchannel 111 is static
while the respective test parameter (i.e., pressure or temperature)
is iteratively changed. It will be appreciated, however, that in
alternate workflows the fluid mixture introduced into the
microchannel is flowing at a predetermined flow rate while the
respective test parameter is iteratively changed.
[0064] Another embodiment of a workflow is illustrated in the flow
chart of FIG. 7. The workflow begins at 700. It is assumed that the
reservoir and pump 113 are filled with a sufficient quantity of
reservoir fluid that contains dissolved scaling chemical species
and the reservoir and pump 121 are filled with a sufficient
quantity of liquid or gas to be tested. At 701 the reservoir and
pump 113 and the corresponding valve 115 are controlled to
introduce reservoir fluid into the inlet port 103 of the
microfluidic device 101 while the reservoir and pump 121 and the
corresponding valve 123 are controlled to introduce liquid or gas
into the inlet port 105 of the microfluidic device 101. The pumping
rates for the pumps 113 and 121 are configured such that the
reservoir fluid and liquid or gas are supplied to the inlet ports
103 and 105 at constant flow rates. The flow rates for the
reservoir fluid and liquid or gas establish the relative volume
ratio of reservoir fluid to liquid or gas for the test. The flow
rates and thus the resultant relative volume ratios of reservoir
fluid to liquid or gas can be varied over multiple iterations of
the test as desired. The reservoir fluid and liquid or gas that are
supplied to the inlet ports 103 and 105 flow to the mixing section
109 of the microfluidic device 101, where the fluids mix to form a
fluid mixture that exits mixing section 109. Due to the large
surface-to-volume ratio of the microchannel 111, the mixture
flowing through the microchannel 111 exhibits excellent mass
transfer between the co-flowing fluids. The mixture exits the
microchannel 111 and flows out the outlet port 107 of the
microfluidic device 101 to the collection chamber and pump 129 via
the outlet line 133.
[0065] Concurrent with the operations of 701, the workflow carries
out a sequence of operations in 705 and 707 that vary the
volumetric flow rate of the fluid flow through the microchannel 111
in order to determine properties related to the scale onset
formation condition for the flow through the microchannel 111. In
each of 705 and 707, the temperature of the mixture through the
microchannel 111 is maintained at the reservoir temperature TR via
temperature control of the temperature-controlled cooling/heating
surface 135. As mentioned earlier, temperature equilibration in the
microchannel 111 can be achieved quickly due to the availability of
large surface area as well as small fluid volume of the
microchannel 111. During the operation of 705 and 707, pressures
P.sub.1, P.sub.2, P.sub.3, and P.sub.4 are measured by the pressure
sensors 117, 125, 131, and 155 and recorded by the computer
processing system 145, and temperatures T.sub.1 and T.sub.2 are
measured by the temperature sensors 137 and 139 and recorded by the
computer processing system 145. Such pressures and temperatures can
also be displayed on a graph relative to time for user evaluation,
if desired. Such pressures and temperatures can also be stored in
the memory system of the computer processing system 145 for
automated data analysis if desired.
[0066] In 703, the temperature of the mixture through the
microchannel 111 is regulated such that it is maintained at the
reservoir temperature T.sub.R. The flow rate of the mixture is
initially set high to establish a high inlet pressure P.sub.4 close
to reservoir pressure, where the scaling chemical species is
dissolved. Thus, the high average pressure value at the reservoir
temperature T.sub.R is well above the scale onset pressure for the
constant flow conditions in the microchannel 111. After a time
period where the inlet pressure P.sub.4 reaches a steady state
value near the reservoir pressure P.sub.R, and the temperatures
T.sub.1 and T.sub.2 reach steady state values near the reservoir
temperature T.sub.R, at 705, the flow rate of the mixture is
reduced in stepwise fashion. The mixture flow rate is reduced by a
step, Qstep, by reducing the respective flow rates of the reservoir
fluid and the liquid or gas supplied to the inlet ports 103 and 105
at the mixing ratio set for the testing.
[0067] In a fully developed laminar flow through a circular
channel, the pressure drop for driving the liquid at a specified
flow rate can be calculated by using the Hagen-Poiseuille equation
as follows:
.DELTA. p = 128 .mu. L QL .pi. D h 4 ( 1 ) ##EQU00001## [0068]
where .mu.L is the liquid viscosity, [0069] Q is the average
volumetric flow rate through the channel, [0070] L is the total
channel length, and [0071] D.sub.h (=4.times.cross-section/wetted
perimeter) is the hydraulic diameter of the channel.
[0072] For a constant flow in a fixed-length channel, the pressure
drop scales linearly with viscosity. However, the channel diameter
can have a larger influence (fourth power of D.sub.h) on the
pressure drop. Therefore, a small variation in a channel
cross-section or viscosity can be easily detected by monitoring the
pressure drop. It should be noted that the surface-to-volume ratio
varies as D.sub.h.sup.-1. Thus, the pressure drop required for a
constant flow in the microchannel 111 is expected to be
considerably higher (based on Eq. 1) when scale forms inside the
microchannel 111 than in the case of simple fluid flow. The flow of
the fluid carrying precipitated scale is analogous to the flow of
particle suspensions, where the effective viscosity in the flow
increases due to the presence of solid particles. Additionally, the
deposition of scale on the internal surface of the microchannel 111
also reduces the hydraulic diameter. Both of these two effects
contribute to an increase in the pressure drop in the microchannel
111 to maintain the volumetric flow.
[0073] Equation (1) can also be rewritten as follows:
.DELTA.p=KQ (2) [0074] where K is a flow characteristic represented
by:
[0074] K = 128 L .mu. L .pi. D h 4 ( 3 ) ##EQU00002## [0075] where
.mu..sub.L is the liquid viscosity, [0076] L is the total channel
length, and [0077] D.sub.h (=4.times.cross-section/wetted
perimeter) is the hydraulic diameter of the channel. Thus, the
inlet pressure P.sub.4 can be represented as:
[0077] P.sub.4=P.sub.3+KQ (4)
[0078] When the flow characteristic K is constant, the pressure
drop, and thus the inlet pressure P.sub.4, vary linearly with Q. K
is assumed to be constant when scale has not formed and the
viscosity and hydraulic diameter are not affected by scale
formation. Therefore, in the absence of scale formation occurring,
the pressure drop and the inlet pressure P.sub.4 are expected to
vary linearly with the flow characteristic K. Specifically, if the
inlet pressure P.sub.4 is plotted against flow rate Q while K is
constant, the inlet pressure P.sub.4 would be represented by a
straight line having a slope K and offset of P.sub.3. However, if
scale begins to form as the volumetric flow rate is changed by
Qstep, then the value of the flow characteristic K would begin to
deviate from the value of K before scale began to form. Such a
change in the value of the flow characteristic K may be attributed
to a change in viscosity of the fluid due to scale precipitate
formation and/or a change in the hydraulic diameter due to scale
formation on the microchannel. Thus, when scale begins to form in
the flowing fluid and/or on the microchannel 111, the pressure
P.sub.4 would not lie on the straight line mentioned above in the
case where the flow characteristic K is constant. Therefore, it is
possible to denote the scale onset pressure P.sub.4 by comparing an
expected pressure drop (assuming a linear relationship between
pressure drop and volumetric flow rate when K is constant) for each
Qstep increment with the actual pressure drop measured for each
Qstep increment. When the actual pressure drop measured deviates
significantly from the expected pressure drop, the deviation can be
attributed to scale formation and the inlet pressure P.sub.4 at
that formation condition can be taken to correspond to the scale
onset pressure.
[0079] Specifically, the pressure difference P.sub.4-P.sub.3 at 707
is compared to the expected pressure difference P.sub.4-P.sub.3
under the steady state conditions as recorded in 703. Such
comparisons provide an indication of scale formation in the
microchannel 111. For example, if the pressure difference
P.sub.4-P.sub.3 varies non-linearly with the volumetric flow rate
(i.e., the pressure drop is larger than the pressure drop that
would be expected after Qstep assuming no change in viscosity and
hydraulic diameter), the non-linearity can be an indication that
the viscosity and/or the hydraulic diameter D.sub.h has changed,
which in turn can be taken to indicate that scale has formed
causing the additional increase in the pressure differentials
indicate higher flow resistance in the microchannel 111 caused by
scale formation.
[0080] In 707, the pressure drop in microchannel 111 is compared to
the expected pressure drop across the microchannel 111 based upon
the flow characteristic obtained when scale is not precipitated
from the mixture. If the pressure drop increased abruptly, then it
is an indication that the scale onset pressure (corresponding to
the reduced flow rate) has been reached (YES at 707). The magnitude
of the abrupt change in pressure drop depends on the
characteristics of the fluid sample, such as the amount and type of
scale formed at onset, used in the test. However, in microchannels
with small hydraulic diameter D.sub.h, the change in pressure drop
will be noticeably different after the formation of scale. If the
scale onset pressure has been reached, then the inlet pressure
P.sub.4 at the flow rate set in 707 is recorded in the computer
processing system 145 as the scale onset pressure and the workflow
ends at 709. However, if the pressure drop did not increase
abruptly, then it is an indication that the scale onset pressure
has not been reached (NO at 707) and, therefore, the workflow
proceeds back to 705 where the bulk flow rate of the mixed flow is
reduced again in stepwise fashion.
[0081] Note that the evaluation of 707 can be carried out by visual
interpretation of the pressure data and/or images of the
microchannel 111 by the operator/user. For fully-automated and
semi-automated implementations of the workflow, such evaluation can
also involve signal processing of the pressure data for P.sub.1,
P.sub.2, P.sub.3, and P.sub.4 that is carried out by the computer
processing system 145 in order to derive an indication of scale
formation and/or can involve image processing of the image(s) of
the microchannel 111 that is carried out by the computer processing
system 145 in order to detect the presence (or absence) of scale in
the microchannel 111.
[0082] The workflow shown in FIG. 7 can be repeated multiple times
using different Qstep values in order to determine the scale onset
pressure. It will be appreciated that larger Qstep values may
reduce the number of iterations of 705 and 707 before determining
the scale onset pressure, while smaller Qstep values may increase
the number of iterations of 705 and 707 before determining the
scale onset pressure. Moreover, it will be appreciated that larger
Qstep values may yield a determination of scale onset pressure that
is less accurate than if smaller Qstep values are used. Thus, there
may be a tradeoff in the workflow between duration of the testing
and accuracy of the result in that smaller Qstep increments may
require more iterations and, thus, a longer workflow, while
providing a more accurate determination of the scale onset
pressure, whereas larger Qstep increments may require less
iterations and, thus, a shorter workflow, while providing a less
accurate (rough estimate) determination of the scale onset
pressure. Also, the workflow can be repeated multiple times with
different volume ratios of the reservoir fluid and liquid or gas to
be tested in order to determine the scale onset pressure of the
fluid flow for the different reservoir fluid-test fluid volume
ratios.
[0083] The test apparatus 100 (and the workflows of FIGS. 5, 6, and
7) as described herein can readily be adapted as depicted in FIG. 8
to characterize properties of scale formation for a reservoir fluid
sample. FIG. 8 shows the test apparatus 100 of FIG. 1 modified with
the addition of an additional reservoir and pump 150, a
corresponding valve 151, and a pressure sensor 157, which are
connected to the apparatus 100 between the mixing section 109 and
the microchannel 111. The test apparatus 100 also includes the
controller and/or computer processing system 145 that includes
control logic that interfaces to the electrically-controlled
reservoir and pumps 113, 121, and 150 via wired or wireless signal
paths therebetween for control of the operation of the pumps 113,
121, and 150, that interfaces to the electrically-controlled valves
115, 123, and 151 via wired or wireless signal paths therebetween
for control of the operation of the valves 115, 123, and 151, that
interfaces to the temperature-controlled cooling/heating surface
135 via wired or wireless signal paths therebetween in order to
provide for temperature control of the microfluidic device 101 (or
the microchannel 111 or portions thereof), that interfaces to the
pressure sensors 117, 125, 131, 155, and 157 via wired or wireless
signal paths therebetween for pressure measurements and recordation
of such pressure measurements during operation of the test
apparatus 100, and that interfaces to the temperature sensors 137
and 139 via wired or wireless signal paths therebetween for
temperature measurements and recordation of such temperature
measurements during operation of the test apparatus 100. The
controller and/or computer processing system 145 can also interface
to the light source 141 and/or to the camera 143 via wired or
wireless signal paths therebetween in order to capture high
resolution images of the microchannel 111 and recordation of such
high resolution images and possibly display of such high resolution
images during operation of the test apparatus 100. The control
logic of the controller and/or computer processing system 145
(which can be embodied in software that is loaded from persistent
memory and executed in the computing platform of the computer
processing system 145) is configured to control the different parts
of the test apparatus 100 to carry out a sequence of operations
(workflow) that characterizes properties related to scale formation
condition (such as scale formation temperature and pressure) of the
fluid that is introduced into the microchannel 111 of the
microfluidic device 101 as described hereinabove. The control logic
can be configured by user input or a testing script or other
suitable data structure, which is used to configure the controller
or the computer processing system 145 in order to carry out control
operations that are part of the workflow as described herein. For
example, the user input or the testing script or other suitable
data structure can specify parameters (such as pressures, flow
rates, temperatures, etc.) for such control operations of the
workflow.
[0084] The remainder of the test apparatus 100 described above in
connection with FIG. 1 is constructed and operates as described
hereinabove and will not be repeated for the sake of brevity. The
reservoir and pump 150 can optionally be filled with a sufficient
quantity of an additive, such as a scale inhibitor (that inhibits
formation of scale when mixed with the reservoir fluid). In this
case, the reservoir and pump 113 and the corresponding valve 115
are controlled to introduce the reservoir fluid into the inlet port
103 of the microfluidic device 101, the reservoir and pump 121 and
the corresponding valve 123 are optionally controlled to introduce
a fluid (liquid or gas) into the inlet port 105 of the microfluidic
device 101, and the reservoir and pump 150 and the corresponding
valve 151 are optionally controlled to introduce the additive into
the inlet port 105 of the microfluidic device 101. Thus, the
construction of test apparatus 100 permits at least three fluids
from the respective reservoir and pumps 113, 121, and 150 to be
premixed according to a predetermined mixture ratio before entering
the microchannel 111. The pumping rates for the pumps 113, 121, and
150 are configured such that the respective fluids are supplied at
constant flow rates.
[0085] The workflow processes described hereinabove with respect to
FIGS. 5, 6, and 7 can also be carried out using the modified test
apparatus 100 shown in FIG. 8 to determine the scale onset pressure
for various mixtures of reservoir fluid, fluids (such as liquid or
gas), and scale inhibitors.
[0086] For example, the flow rates and, thus, the resultant
relative volume ratios of reservoir fluid and scale inhibitor can
be varied over multiple iterations of the test in order to study
scale onset pressure for different flow pressures and/or scale
inhibitor concentrations as desired. Similarly, the multiple
iterations of the tests can be repeated with different scale
inhibitors in order to study the effects of different scale
inhibitors on the particular reservoir fluid sample at different
pressures and/or scale inhibitor concentrations, as desired. The
results of such test workflow operations can be used to optimize a
strategy for reservoir fluid production and/or transportation that
minimizes the formation of scale during these processes.
[0087] The test apparatus and the workflow as described herein may
provide some advantages. The apparatus and workflow described
herein can rapidly determine scale onset conditions. Also, the test
apparatus and workflow are suitable for a wellsite environment. The
apparatus and workflow exhibit excellent repeatability in the
determination of scale onset conditions. The data obtained using
the apparatus and workflow described herein is high quality data,
and is comparable to conventional pressure-volume-temperature (PVT)
laboratory measurements. Additionally, the apparatus and workflow
described herein do not require large sample volumes and can be
automated to a large extent, making them somewhat operator
independent. Moreover, the apparatus and workflow described herein
are suitable for testing and screening additives and scale
inhibitors.
[0088] There have been described and illustrated herein several
embodiments of test apparatus and method that employs a
microfluidic device to characterize properties of scale formation
of a fluid. While particular embodiments of the invention have been
described, it is not intended that the invention be limited
thereto, as it is intended that the invention be as broad in scope
as the art will allow and that the specification be read likewise.
It will therefore be appreciated by those skilled in the art that
yet other modifications could be made to the provided invention
without deviating from its scope as claimed.
* * * * *