LOW-FREQUENCY VISCOSITY, DENSITY, AND VISCOELASTICITY SENSOR FOR DOWNHOLE APPLICATIONS
Disclosed is an apparatus for estimating a property of a fluid downhole. The apparatus includes a carrier configured to be conveyed through a borehole penetrating the earth. A cantilever is disposed at the carrier and configured to move in the fluid upon receiving a stimulus. An actuator is disposed at the cantilever and configured to provide the stimulus at a frequency less than a lowest resonant frequency of the cantilever. A sensor is disposed at the cantilever and configured to sense a strain imposed on the cantilever due to movement of the cantilever in the fluid in order to estimate the property.
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This application claims the benefit of Provisional Application No. 61/491,409, entitled “LOW-FREQUENCY VISCOSITY, DENSITY, AND VISCOELASTICITY SENSOR FOR DOWNHOLE APPLICATIONS”, filed May 31, 2011, which is incorporated herein by reference in its entirety.
BACKGROUNDIn geophysical industries such as for hydrocarbon exploration and production, geothermal energy, and carbon sequestration, it is important to characterize fluids deep in the earth. Boreholes are drilled into the earth in order to access these fluids. Borehole tools are then conveyed through the boreholes to perform measurements on downhole fluids. Typically, very high pressures and temperatures are encountered by the tools when they are disposed in a downhole environment.
Physical properties such as density, viscosity, and viscoelasticity of downhole fluids are important to know when performing measurements on particle and polymer laden fluid as in fracking fluid as well as in some drilling muds. It is also important to know the density and viscosity of reservoir fluids at the pressure and temperature of the reservoir in order to determine the permeability and flow characteristics of the reservoir. It would be well received in the drilling industry if a sensor would be developed to measure physical properties of downhole fluids at ambient conditions.
BRIEF SUMMARYDisclosed is an apparatus for estimating a property of a fluid downhole. The apparatus includes a carrier configured to be conveyed through a borehole penetrating the earth. A cantilever is disposed at the carrier and configured to move in the fluid upon receiving a stimulus force. An actuator is disposed at the cantilever and configured to provide the stimulus force at a frequency less than a lowest resonant frequency of the cantilever. A sensor is disposed at the cantilever and configured to sense a strain imposed on the cantilever due to movement of the cantilever in the fluid in order to estimate the property.
Also disclosed is a method for estimating a property of a fluid downhole. The method includes conveying a carrier through a borehole penetrating the earth and moving a cantilever disposed at the carrier in the fluid with an actuator at a frequency less than a lowest resonant frequency of the cantilever. The method further includes sensing a strain imposed on the cantilever due to movement of the cantilever in the fluid using a sensor in order to estimate the property.
Further disclosed is a non-transitory computer-readable medium having computer-executable instructions for estimating a property of a fluid downhole by implementing a method that includes: moving a cantilever in the fluid with an actuator at a frequency less than a lowest resonant frequency of the cantilever, the cantilever being disposed at the carrier configured to be conveyed through a borehole penetrating the earth; and sensing a strain imposed on the cantilever due to movement of the cantilever in the fluid using a sensor in order to estimate the property.
The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:
A detailed description of one or more embodiments of the disclosed apparatus and method presented herein by way of exemplification and not limitation with reference to the Figures.
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The actuator 21 can be built integral to the cantilever 20 or the actuator 21 can be attached to the cantilever 20 such as by an adhesive. In one or more embodiments, the actuator 21 includes materials that can provide a moving force responsive to a stimulus applied to the materials. Non-limiting embodiments of materials for the actuator 21 include electrically conductive materials, magnetic materials, piezoelectric materials, joule heating materials, magnetostrictive and photostrictive materials. With a conductive material, an electric current flowing through the conductive material can interact with a magnetic field to cause the cantilever 20 to move. With a magnetic material, varying the intensity of an external magnetic field, such as by varying a magnetizing current through an electromagnet, can cause the cantilever 20 to move in relation to the magnitude of the magnetizing current. With a piezoelectric material, applying a voltage to that material can cause the cantilever 20 to move. With a magnetostrictive material, varying an intensity of a magnetic field in that material can cause the cantilever 20 to move. With a photostrictive material, applying light to that material can cause the cantilever 20 to move. It can be appreciated that the various materials used for the actuator 21 can be built integral to (i.e., within) the cantilever 20 or they can be deposited in one or more layers on the cantilever 20.
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In one or more embodiments, the sensor 24 is a resistance strain gauge in which a resistance of the strain gauge is related to the strain experienced by the strain gauge. In one or more embodiments of the resistive strain gauge, as the cantilever 20 flexes, the resistance material of the strain gauge either compresses decreasing total resistance or stretches increasing the total resistance. Hence, a change of resistance of this strain gauge is related to a change in the measured strain and displacement or movement of the cantilever 20. In one or more embodiments, the sensor 24 is a magnetostrictive strain gauge, which uses a magnetostrictive material to sense strain. The magnetostrictive material has a magnetization that is related to the strain experienced by that material. Thus, in one or more embodiments, a coil can have a voltage induced in it by a changing magnetic field of the magnetostrictive material (related to the changing strain) as the cantilever 20 moves back and forth. As with the actuator 21, it can be appreciated that the sensor 24 can be built into the cantilever 20, such as with solid-state electronic fabrication techniques, or attached post-fabrication such as with an adhesive.
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As noted above, movement or deflection of the cantilever 20 can be related to a physical property of the fluid of interest. Generally, measurement of the movement or deflection of the cantilever 20 as a function of time is made with respect to the stimulus force applied by the actuator 21. That is, displacement of the cantilever 20 over time is measured with respect to the stimulus applied by the actuator 21 in order to determine a damping factor of the cantilever 20 caused by the fluid of interest. Movement of the cantilever 20 can include the effects of bulk movement of the fluid and shearing of the fluid. The bulk movement is related to the density of the fluid and the shearing is related to the viscosity of the fluid. It can be appreciated that the sizes of the holes 25 and 26 can be selected or tuned to predominantly measure density or viscosity. Smaller holes result in a larger cross-sectional area of the cantilever 20 for predominantly measuring density. Larger holes result in a smaller cross-sectional area of the cantilever 20 for predominantly measuring viscosity. It can also be appreciated that the size of the holes 25 and 26 can be selected to provide a balance between measurements of density and viscosity. It can also be appreciated that holes 25 and 26 provide insulation between the various materials used for the actuator 21 on the various bridge elements.
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Once measurements of the fluid of interest are performed using the cantilever 20, the resulting strain measurements of the cantilever 20 are used to estimate a physical property of the fluid of interest. Disclosed are at least two methods to estimate the physical property from the strain measurements. In one method, the instrument 7 is calibrated in a laboratory using samples of expected downhole fluids having known physical properties such as density, viscosity, and viscoelasticity. Hence, a measured response of the instrument 7 can be compared to the calibrated responses of the laboratory samples to estimate the physical properties. In another method, the strain measurements are input into mathematical relationships that use basic principles to relate the strain measurements to the physical properties.
One example of mathematical relationships relating a strain measurement to density is now presented where ε represents the strain measured by the sensor 24 where the sensor 24 is a resistive strain gauge.
where ΔR is the change in resistance caused by strain,
RG is the resistance of the undeformed sensor 24, and GF is the gauge factor.
where τ is the shear stress exerted by the fluid (Pa),
μ is the fluid viscosity—a constant of proportionality (Pa·s), and
is the velocity gradient perpendicular to the direction of shear, or equivalently the strain rate (s−1).
The shear stress is calculated from the measured strain using τ=ε/Aplate
where Aplate is the area of the cantilever 20 moving in the fluid of interest, assuming a pure shear motion. The estimation of viscosity above is for a Newtonian fluid (temperature and pressure effects are neglected). For non-Newtonian (viscoelastic) fluids, the stress is given by a tensor and various models such as Kelvin-Voigt are used to estimate visco elastic properties.
In one or more embodiments, the cantilever 20 can be actuated at two or more different frequencies that provide for measuring the viscosity of the fluid of interest at two different shear rates. By measuring the viscosity at two or more different shear rates, the fluid of interest can be identified and the viscoelasticity determined.
In one or more embodiments, the actuation force or stimulus force applied by the actuator 21 to the cantilever 20 is controlled to maintain the strain measured by the sensor 24 at a constant value. The constant value of strain relates to maintaining the cantilever 20 in a constant position after deflection in the fluid. A change in the current, voltage, magnetic field, or other actuation parameter or stimulus signal necessary to maintain the constant value of strain is then proportional to the damping effect of the fluid of interest and can be used to derive the viscosity and density of the fluid. A feedback control circuit 40 as illustrated in
It can be appreciated that solid-state components such as the cantilever 20, the actuator 21, the sensor 24 and the electronic device 23 enable the instrument 7 to function in the high temperature and pressure environment experienced downhole.
In support of the teachings herein, various analysis components may be used, including a digital and/or an analog system. For example, the downhole electronics 8, the surface computer processing 9, the electronic device 23 or the feedback control circuit 40 may include the digital and/or analog system. The system may have components such as a processor, storage media, memory, input, output, communications link (wired, wireless, pulsed mud, optical or other), user interfaces, software programs, signal processors (digital or analog) and other such components (such as resistors, capacitors, inductors and others) to provide for operation and analyses of the apparatus and methods disclosed herein in any of several manners well-appreciated in the art. It is considered that these teachings may be, but need not be, implemented in conjunction with a set of computer executable instructions stored on a non-transitory computer readable medium, including memory (ROMs, RAMs), optical (CD-ROMs), or magnetic (disks, hard drives), or any other type that when executed causes a computer to implement the method of the present invention. These instructions may provide for equipment operation, control, data collection and analysis, data and analysis presentation and other functions deemed relevant by a system designer, owner, user or other such personnel, in addition to the functions described in this disclosure.
Further, various other components may be included and called upon for providing for aspects of the teachings herein. For example, a power supply (e.g., at least one of a generator, a remote supply and a battery), cooling component, heating component, magnet, electromagnet, sensor, electrode, transmitter, receiver, transceiver, antenna, controller, optical unit, electrical unit or electromechanical unit may be included in support of the various aspects discussed herein or in support of other functions beyond this disclosure.
The term “carrier” as used herein means any device, device component, combination of devices, media and/or member that may be used to convey, house, support or otherwise facilitate the use of another device, device component, combination of devices, media and/or member. Other exemplary non-limiting carriers include drill strings of the coiled tube type, of the jointed pipe type and any combination or portion thereof. Other carrier examples include casing pipes, wirelines, wireline sondes, slickline sondes, drop shots, bottom-hole-assemblies, drill string inserts, modules, internal housings and substrate portions thereof.
Elements of the embodiments have been introduced with either the articles “a” or “an.” The articles are intended to mean that there are one or more of the elements. The terms “including” and “having” are intended to be inclusive such that there may be additional elements other than the elements listed. The conjunction “or” when used with a list of at least two terms is intended to mean any term or combination of terms. The terms “first,” “second” and “third” are used to distinguish elements and are not used to denote a particular order. The term “couple” relates to a first component being coupled to a second component either directly or indirectly through an intermediate component. The term “disposed at” relates to a first component being disposed in or on a second component.
It will be recognized that the various components or technologies may provide certain necessary or beneficial functionality or features. Accordingly, these functions and features as may be needed in support of the appended claims and variations thereof, are recognized as being inherently included as a part of the teachings herein and a part of the invention disclosed.
While the invention has been described with reference to exemplary embodiments, it will be understood that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications will be appreciated to adapt a particular instrument, situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims
1. An apparatus for estimating a property of a fluid downhole, the apparatus comprising:
- a carrier configured to be conveyed through a borehole penetrating the earth;
- a cantilever disposed at the carrier and configured to move in the fluid upon receiving a stimulus force;
- an actuator disposed at the cantilever and configured to provide the stimulus force at a frequency less than a lowest resonant frequency of the cantilever; and
- a sensor disposed at the cantilever and configured to sense a strain imposed on the cantilever due to movement of the cantilever in the fluid in order to estimate the property.
2. The apparatus according to claim 1, wherein the property comprises at least one of density, viscosity, and visco elasticity.
3. The apparatus according to claim 1, wherein the frequency is zero Hertz.
4. The apparatus according to claim 3, further comprising a feedback control circuit configured to receive the strain as input and to control a signal to the actuator to maintain the strain at a constant value wherein a change in magnitude of the signal necessary to maintain the strain at the constant value is used to derive viscosity or density of the fluid.
5. The apparatus according to claim 1, wherein the cantilever and a base supporting the cantilever is formed from a substrate.
6. The apparatus according to claim 1, wherein the cantilever defines a first hole and a second hole with a center bridge element disposed between the holes, the cantilever further defining a first side bridge element adjacent to the first hole and a second side bridge element adjacent to the second hole, the first, second, and center bridge elements extending from a base to a distal end of the cantilever.
7. The apparatus according to claim 6, wherein the sensor is disposed at the center bridge element.
8. The apparatus according to claim 6, wherein sensor comprises a first sensor disposed at the first side bridge element, a second sensor disposed at the second side bridge element, and a third sensor disposed at the center bridge element.
9. The apparatus according to claim 6, wherein the actuator comprises a conductive element extending from the first side bridge element to the second side bridge element and configured to conduct current to interact with a magnetic field in order to move the cantilever.
10. The apparatus according to claim 6, wherein the actuator comprises a layer of magnetic material extending from the first side bridge element to the second side bridge element and configured to interact with a magnetic field in order to move the cantilever.
11. The apparatus according to claim 1, wherein the actuator comprises at least one of a piezoelectric material, a conductive material, a magnetostrictive material, and a photostrictive material.
12. The apparatus according to claim 11, wherein the conductive material is configured to conduct current that interacts with a magnetic field to move the cantilever.
13. The apparatus according to claim 12, wherein the actuator further comprises a source of the magnetic field configured to interact with a current or magnetic material disposed at the cantilever in order to move the cantilever.
14. The apparatus according to claim 1, further comprising an electronic device coupled to the actuator and configured to actuate the actuator at the frequency less than the lowest resonant frequency of the cantilever.
15. The apparatus according to claim 14, wherein the electronic device is configured to provide at least one of a voltage, a current, and light to actuate the actuator.
16. The apparatus according to claim 1, wherein the sensor comprises a strain gauge.
17. The apparatus according to claim 16, where in the strain gauge uses a change in resistance or a magnetostrictive effect to measure the strain.
18. The apparatus according to claim 1, wherein the carrier comprises at least one of a wireline, a slickline, a drillstring, and coiled tubing.
19. A method for estimating a property of a fluid downhole, the method comprising:
- conveying a carrier through a borehole penetrating the earth;
- moving a cantilever in the fluid with an actuator at a frequency less than a lowest resonant frequency of the cantilever, the cantilever being disposed at the carrier; and
- sensing a strain imposed on the cantilever due to movement of the cantilever in the fluid using a sensor in order to estimate the property.
20. The method according to claim 19, wherein the property comprises at least one of density, viscosity, and viscoelasticity.
21. The method according to claim 19, wherein sensing comprises measuring the strain as a function of time with respect to a stimulus applied to the cantilever by the actuator.
22. The method according to claim 19, wherein the frequency comprises a first frequency and a second frequency and the strain comprises a first strain corresponding to movement of the cantilever at the first frequency and a second strain corresponding to movement of the cantilever at the second frequency, the first strain and the second strain being used to identify the fluid and to estimate viscoelasticity of the fluid.
23. A non-transitory computer-readable medium comprising computer-executable instructions for estimating a property of a fluid downhole by implementing a method comprising:
- moving a cantilever in the fluid with an actuator at a frequency less than a lowest resonant frequency of the cantilever, the cantilever being disposed at the carrier configured to be conveyed through a borehole penetrating the earth; and
- sensing a strain imposed on the cantilever due to movement of the cantilever in the fluid using a sensor in order to estimate the property.
Type: Application
Filed: May 8, 2012
Publication Date: Dec 6, 2012
Applicant: BAKER HUGHES INCORPORATED (Houston, TX)
Inventor: Sunil Kumar (Celle)
Application Number: 13/466,216