PRESSURE MEASUREMENT OF A RESERVOIR FLUID IN A MICROFLUIDIC DEVICE
Methods and related systems are described for measuring fluid pressure in a microchannel. A number of flexible membranes are positioned at locations along the microchannel such that pressure of the fluid in the microchannel causes a deformation of the membranes. An optical sensing system adapted and positioned to detect deformation of the membranes that thereby determine the pressure of the fluid flowing in the microchannel at a number of locations along the microchannel.
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This patent application is a continuation-in-part of International Patent Application No. PCT/IB09/50500, filed Feb. 7, 2009, which is incorporated by reference herein.
BACKGROUND OF THE INVENTION1. Field of the Invention
This patent specification relates to an apparatus and method for measuring thermo-physical properties of a reservoir fluid. More particularly, the patent specification relates to an apparatus and method for measuring pressure of a reservoir fluid flowing in a microfluidic device.
2. Description of Related Art
The measurement of reservoir fluid properties is a key step in the planning and development of a potential oilfield. It is often desirable to perform such measurements frequently on a producing well to provide an indication of the performance and behavior of the production process. Examples of such measurements are pressure, volume, and temperature measurements, often referred to as “PVT” measurements, which are instrumental in predicting complicated thermo-physical behavior of reservoir fluids. One important use of PVT measurements is the construction of an equation of state describing the state of oil in the reservoir fluid. Other properties of interest that may be determined using PVT measurements include fluid viscosity, density, chemical composition, gas-oil-ratio, and the like. Once a PVT analysis is complete, the equation of state and other parameters can be input into reservoir modeling software to predict the behavior of the oilfield formation.
Conventional PVT measurements are performed using a cylinder containing the reservoir fluid. A piston disposed in the cylinder maintains the desired pressure on the fluid, while the heights of the liquid and gaseous phases are measured using, for example, a cathetometer. International Patent Application No. PCT/IB09/50500, filed Feb. 7, 2009, discusses microfluidic technique form measuring thermo-physical properties of a reservoir fluid. The microfluidic techniques can provide certain advantages including: (1) providing a way to measure thermo-physical properties of a reservoir fluid with small amounts of reservoir fluid; (2) providing a way to perform pressure-volume-temperature analyses of a reservoir fluid in a timely fashion; and (3) providing a way to measure thermo-physical properties of a reservoir fluid using image analysis. However, in some cases the microfluidic based measurements and analysis can benefit from pressure measurement at various points along the microchannel.
Pressure sensors based on deformation of a membrane have long been developed. These membranes are usually micro-fabricated using SOI or silicone-on-insulator wafers. For example, see, U.S. Pat. Nos. 5,095,401, 5,155,061, 5,165,282, and 5,177,661, each of which is incorporated by reference herein. Numerous techniques have been used to correlate deformation of the membrane with pressure. These techniques include piezo-resistive element (see, e.g., U.S. Pat. Nos. 5,081,437, 5,172,205, and 6,843,121), optical fibers (See. e.g. U.S. Pat. Nos. 7,000,477, and 7,149,374; and U.S. Patent Publication Nos. 2005/0041905, and 2008/0175529), and capacitive sensors (See. e.g. U.S. Pat. Nos. 7,254,008, 5,470,797, and 6,945,116, and PCT Patent Publication Nos. WO 96/16319, and WO 98/23934). Each of the foregoing patents and patent publications are incorporated by reference herein.
Most of these techniques have been developed for conventional pressure sensors. Incorporating such tools inside a microchannel is either too difficult or otherwise impractical. Practical and cost effective measurement techniques for microchannels are rare. To measure pressure inside a microfluidic channel, some techniques have been described. For example, R. Baviere, F. Ayela, Meas. Sci. Technol., 15, (2004), 377, incorporated by reference herein, discusses the use of piezo-resistive elements; and M. J. Kohl, S. I. Abdel-Khalik, S. M. Jeter, D. L. Sadowski, Sensors and Actuators a-Physical, 118, (2005), 212; and M. J. Kohl, S. I. Abdel-Khalik, S. M. Jeter, D. L. Sadowski, Int. J. Heat Mass Transfer, 48, (2005), 1518, both incorporated by reference herein, discuss the use of lasers.
However, there remains a need for simple non-invasive techniques to measure pressure inside a microfluidic channel.
BRIEF SUMMARY OF THE INVENTIONAccording to embodiments, a system for measuring fluid pressure in a microchannel is provided. The system includes a microchannel adapted to carry a fluid; a first flexible member adapted and positioned such that pressure of the fluid in the microchannel causes a deformation of the first flexible member; and an optical sensing system adapted and positioned to detect deformation of the first flexible member.
The flexible member is preferably a membrane partially defining a cavity that is in fluid communication with the microchannel at a first location such that deformation of the membrane is representative of the fluid pressure in the microchannel at the first location. According to some embodiments, second and third membranes also can be provided to provide detecting of pressure at second and third locations on the microchannel.
Additionally, according to some embodiments a method for measuring fluid pressure in a microchannel is provided. The method includes providing a microchannel adapted to carry a fluid, and a first flexible member adapted and positioned such that pressure of the fluid in the microchannel causes a deformation of the first flexible member. Fluid is introduced under pressure into the microchannel, thereby causing a deformation of the first flexible member, and deformation of the first flexible member is optically detected. A value can be determined representing the pressure at a location in the microchannel based at least in part on the optically detected deformation of the first flexible member.
Further features and advantages of the invention will become more readily apparent from the following detailed description when taken in conjunction with the accompanying drawings.
The present invention is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of exemplary embodiments of the present invention, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein:
While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTSIllustrative embodiments of the invention 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 indicated like elements.
According to embodiments, systems and methods for measuring pressure of a reservoir fluid in a microfluidic device are provided. 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. Moreover, for the purposes of this disclosure, the term “microfluidic” means 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.
In
In operation, pressurized reservoir fluid is urged through entrance passageway 121, entrance well 107, and inlet 117 into microchannel 105. The reservoir fluid exits microchannel 105 through outlet 119, exit well 109, and exit passageway 123. Microchannel 105 provides substantial resistance to the flow of reservoir fluid therethrough because microchannel 105 is very small in cross-section in relation to the length of microchannel 105. When fluid flow is established between inlet 117 and outlet 119 of microchannel 105, the pressure of the reservoir fluid within microchannel 105 drops from an input pressure, e.g., reservoir pressure, at inlet 117 to an output pressure, e.g., atmospheric pressure, at outlet 119. The overall pressure drop between inlet 117 and outlet 119 depends upon the inlet pressure and the viscosity of the reservoir fluid. Fluid flow through microchannel 105 is laminar and, thus the pressure drop between inlet 117 and outlet 119 is linear when the reservoir fluid exhibits single-phase flow. For further details of microfluidic devices and method for measuring thermo-physical properties of reservoir fluid, see e.g. International Patent Application No. PCT/IB09/50500, filed Feb. 7, 2009, which is incorporated by reference herein, and in co-pending U.S. Pat. No. ______, entitled “PHASE BEHAVIOR ANAYSIS USING A MICROFLUIDIC PLATFORM,” Attorney Docket No. 117.0043 US NP, filed on even date herewith, which is incorporated by reference herein. Once the flow is established, the membrane in each cavity, such as cavity 150, deforms due to the fluid pressure and the deformation can be optically detected, as is described more fully below.
Thermo-physical properties of the reservoir fluid, such as reservoir fluid 201 of
Once a stabilized flow of reservoir fluid is established in microchannel 105, a camera 401 is used to capture snapshots of the flow, as shown in
Microfluidic device 501 further comprises a second substrate 511 defining an entrance passageway 513 and an exit passageway 515 in fluid communication with entrance well 507 and exit well 509. Second substrate 511 is made from glass, as discussed herein concerning second substrate 111 (shown in
The present invention contemplates microfluidic device 501 having any suitable size and/or shape needed for a particular implementation. In one embodiment, microfluidic device 501 exhibits an overall length A of about 80 millimeters and an overall width B of about 15 millimeters. In such an embodiment, passageways 513 and 515 are spaced apart a distance C of about 72 millimeters, cavities 558 and 550 are spaced apart a distance D of about 3 millimeters, and cavities along the serpentine section of microchannel 505, such as cavities 550 and 554 are spaced apart by a distance E of about 5 millimeters. It should be noted that microfluidic device 101 may also exhibit dimensions corresponding to microfluidic device 501. However, the scope of the present invention is not so limited.
Referring to
In
According to one embodiment, the microfluidic device 501 is mounted on a chip holder perpendicular to the main axis of the confocal sensor 1110. The sensor is also mounted on a holder that can move the sensor in two orthogonal directions using two micro-stages. In this way, the sensor 1110 can be focused, one at a time, on any of the other membranes of the other cavities located on device 501.
To calibrate membrane deformation, a series of hydrostatic tests were performed. The exit port of the microfluidic device was plugged to prevent any flow in the system. Then, the input pressure was varied from 0 psig up to 800 psig. This guaranteed a uniform hydrostatic pressure throughout the channel.
The accuracy and reliability of the described techniques is further demonstrated by the following experiment. In a microchannel where Reynolds number is extremely low, the pressure drop is linear. In other words, if a fluid is injected at a give pressure and the output pressure is atmospheric, the pressure inside the channel maintains a linear relationship with the length of the channel. In such a system, flow rate is calculated using:
where Q, ΔP, and R represent flow rate, pressure drop, and channels resistance respectively. For a rectangular microchannel R can be calculated using the teachings of D. J. Beebe, G. A. Mensing, G. M. Walker, Annual Review of Biomedical Engineering, 4, (2002), 261, which is incorporated herein by reference, namely:
where ω is the channel width and h is the channel height. The above equations show that there is a linear relationship between pressure inside the channel and the length. Therefore, it can be expected that there is a linear pressure drop along the channels.
The membranes were calibrated using the data shown in
Although many embodiments have been described herein with respect to analysis of reservoir fluids, the present invention is also applicable to the analysis of many other types of fluids. According to some embodiments analysis of one or more types of biomedical fluids is provided including but not limited to bodily fluids such as blood, urine, serum, mucus, and saliva. According to other embodiments analysis of one or more fluids is provided in relation to environmental monitoring, including by not limited to water purification, water quality, and waste water processing, and potable water and/or sea water processing and/or analysis. According to yet other embodiments, analysis of other fluid chemical compositions is provided.
Whereas many alterations and modifications of the present invention will no doubt become apparent to a person of ordinary skill in the art after having read the foregoing description, it is to be understood that the particular embodiments shown and described by way of illustration are in no way intended to be considered limiting. Further, the invention has been described with reference to particular preferred embodiments, but variations within the spirit and scope of the invention will occur to those skilled in the art. It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to exemplary embodiments, it is understood that the words, which have been used herein, are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular means, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.
Claims
1. A system for measuring fluid pressure in a microchannel comprising:
- a microchannel adapted to carry a fluid;
- a first flexible member adapted and positioned such that pressure of the fluid in the microchannel causes a deformation of the first flexible member; and
- an optical sensing system adapted and positioned to detect deformation of the first flexible member.
2. A system according to claim 1, wherein the first flexible member is a first membrane.
3. A system according to claim 2, further comprising a first cavity defined in part by the first membrane, wherein the first cavity is in fluid communication with the microchannel at a first location such that a fluid pressure within the first cavity corresponds to the fluid pressure in the microchannel at the first location, and the deformation of the first membrane is representative of the fluid pressure within the first cavity.
4. A system according to claim 3, wherein the cavity and the microchannel are defined at least in part by a first substrate.
5. A system according to claim 4, wherein the first substrate comprises silicon.
6. A system according to claim 3, further comprising:
- a second cavity defined in part by a second membrane and positioned to be in fluid communication with the microchannel at a second location such that a fluid pressure in the second cavity corresponds to the fluid pressure in the microchannel at the second location, and a deformation of the second membrane is representative of the fluid pressure within the second cavity; and
- a third cavity defined in part by a third membrane and positioned to be in fluid communication with the microchannel at a third location such that a fluid pressure in the third cavity corresponds to the fluid pressure in the microchannel at the third location and the deformation of the third membrane is representative of the fluid pressure within the third cavity.
7. A system according to claim 6, wherein the optical sensing system includes first, second and third optical sensors that are adapted and positioned to detect deformation of the first, second and third membranes respectively.
8. A system according to claim 1, wherein the microchannel exhibits a serpentine shape and a length of at least one meter.
9. A system according to claim 1, wherein the microchannel exhibits a width within a range of tens of micrometers to hundreds of micrometers.
10. A system according to claim 1, wherein the optical sensing system comprises an optical sensor, a spectrometer and a computer system.
11. A system according to claim 9, wherein the optical sensor is a confocal chromatic sensor.
12. A system according to claim 1, wherein the microchannel is part of a microfluidic apparatus for measuring thermo-physical properties of a fluid that is of a type selected from the group consisting of: reservoir fluid, biomedical fluid, and a fluid being monitored in connection with environmental monitoring.
13. A system according to claim 1, further comprising an optical sensing system adapted and positioned to detect phase states of the fluid at a plurality of locations along the microchannel.
14. A system according to claim 1 wherein the first flexible member is formed from the same material that at least partially defines the microchannel.
15. A system according to claim 14 wherein the material is silicon.
16. A method for measuring fluid pressure in a microchannel comprising:
- providing a microchannel adapted to carry a fluid, and a first flexible member adapted and positioned such that pressure of the fluid in the microchannel causes a deformation of the first flexible member;
- introducing fluid under pressure into the microchannel, thereby causing a deformation of the first flexible member; and
- optically detecting the deformation of the first flexible member.
17. A method according to claim 16, further comprising determining a value representing the pressure at a location in the microchannel based at least in part on the optically detected deformation of the first flexible member.
18. A method according to claim 16, wherein the first flexible member is a first membrane.
19. A method according to claim 17, wherein a first cavity is defined in part by the first membrane, and the first cavity is in fluid communication with the microchannel at a first location such that fluid pressure within the first cavity corresponds to the fluid pressure in the microchannel at the first location, and wherein the optically detected deformation of the first membrane is representative of the fluid pressure in the microchannel at the first location.
20. A method according to claim 19, further comprising optically detecting deformation of a second membrane and a third membrane both being adapted and positioned to deform according to fluid pressures in the microchannel at second and third locations on the microchannel respectively.
21. A method according to claim 16, wherein the microchannel exhibits a width within a range of tens of micrometers to hundreds of micrometers.
22. A method according to claim 16, wherein the deformation is detected using a confocal chromatic sensor.
23. A method according to claim 16, wherein the introduced fluid is of a type selected from the group consisting of: reservoir fluid, biomedical fluid, and a fluid being monitored in connection with environmental monitoring, and the method further comprises determining one or more thermo physical properties of the introduced fluid flowing through the microchannel.
24. A method according to claim 23, further comprising optically sensing phase states of the fluid at a plurality of locations along the microchannel.
Type: Application
Filed: Jul 31, 2009
Publication Date: Jan 21, 2010
Applicant: Schlumberger Technology Corporation (Cambridge, MA)
Inventor: Farshid Mostowfi (Edmonton)
Application Number: 12/533,292
International Classification: G01V 5/04 (20060101);