US20090166037A1 - Apparatus and method for sampling downhole fluids - Google Patents

Abstract

Tools and methods for downhole sample analysis are provided. An apparatus for sampling a downhole fluid includes a tool having at least one surface element wetted by a downhole fluid such as drilling fluid, return fluid or production fluids such as asphaltenic hydrocarbons. At least one surface element disposed on the tool can include a fluid-repellent material disposed on a substrate for repelling at least a portion of the downhole fluid wetting the surface element.

Description

BACKGROUNDTECHNICAL FIELD
• The present disclosure generally relates to downhole tools and in particular to systems and methods for downhole fluid sampling.
BACKGROUND INFORMATION
• Oil and gas wells have been drilled at depths ranging from a few thousand feet to as deep as five miles. A large portion of the current drilling activity involves directional drilling that includes drilling boreholes deviated from vertical by a few degrees to horizontal boreholes to increase the hydrocarbon production from earth formations.
• Information about the subterranean formations traversed by the borehole may be obtained by any number of techniques. Techniques used to obtain formation information include obtaining one or more core samples of the subterranean formations and obtaining fluid samples produced from the subterranean formations these samplings are collectively referred to herein as formation sampling. Modern fluid sampling includes various downhole tests and sometimes fluid samples are retrieved for surface laboratory testing.
• Typical downhole fluids can include drilling fluids, return fluids, and production fluids containing one or more hydrocarbons. Downhole fluids, depending on composition, temperature, and pressure, can be viscous and/or adhesive in nature. For example, production hydrocarbons can include one or more viscous and/or adhesive asphaltenic compounds, each having twenty or more carbon atoms. Surface-based fluid analyses and downhole fluid analysis are often affected due to the inability to properly purge downhole fluid samples from test cells and from instrument sensors. Fluid buildup on downhole instrument sensors can undesirably increase response time and may cause an unwanted offset in signal response.
SUMMARY
• The following presents a general summary of several aspects of the disclosure in order to provide a basic understanding of at least some aspects of the disclosure. This summary is not an extensive overview of the disclosure. It is not intended to identify key or critical elements of the disclosure or to delineate the scope of the claims. The following summary merely presents some concepts of the disclosure in a general form as a prelude to the more detailed description that follows.
• Disclosed is an apparatus for sampling a downhole fluid. The apparatus can include a tool having at least one surface element wetted by a downhole fluid, and the at least one surface element may include a fluid-repellant material disposed on a substrate for repelling some or all of the downhole fluid wetting the at least one surface element.
• An exemplary method for sampling a downhole fluid includes wetting at least one surface element of a tool with a downhole fluid the at least one surface element comprising a fluid-repellant material disposed on a substrate. The method may further include repelling some or all of the downhole fluid from the at least one surface element.
• An exemplary method for manufacturing an apparatus for sampling a downhole fluid includes disposing a fluid-repellant material on a substrate to form a surface element. The manufacturing method further includes forming at least a portion of a downhole fluid sampling tool using the surface element, the surface element being wettable by a downhole fluid during operation of the downhole fluid sampling tool.
BRIEF DESCRIPTION OF THE DRAWINGS
• For a detailed understanding of the present disclosure, reference should be made to the following detailed description of the several non-limiting embodiments, taken in conjunction with the accompanying drawings, in which like elements have been given like numerals and wherein:
• FIG. 1 schematically represents a non-limiting example of an illustrative tool for conducting a downhole operation according to one or more embodiments of the disclosure;
• FIG. 2 shows a cross-sectional view of an exemplary surface element according to one or more embodiments of the disclosure;
• FIG. 3 depicts a non-limiting example of an illustrative device cross section showing a surface element having a coated substrate according to one or more embodiments of the disclosure;
• FIG. 4 is a non-limiting elevation view of an exemplary well logging apparatus according to several embodiments of the disclosure; and
• FIG. 5 is a non-limiting elevation view of an exemplary simultaneous drilling and logging system that incorporates several aspects of the disclosure.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
• FIG. 1 schematically represents a non-limiting example of anillustrative tool100 for conducting a fluid sampling operation according to one or more embodiments of the disclosure. Thetool100 may be disposed within or about acarrier134. Thecarrier134 may be a surface-located carrier or may be used for transporting thetool100 into a well borehole. Thetool100 may include any number of devices for conducting downhole operations. The tool devices shown in the example ofFIG. 1 include aspectrometer104, and a sensor testsection including sensors118,120,122,124, and asensor interface138 and one ormore sample chambers116. Adownhole computing device128 having aprocessor130 and adata storage unit132 is shown coupled to thespectrometer104 and to the sensor section via acommunications bus136. Information processed in thecomputing device128 may be transmitted via thebus136 to other devices including, but not limited to, controllers, loggers, transmitters, or any combination thereof. Thecommunication bus136 can include one or more optical and/or one or more electrical cables as desired for a particular tool configuration. These and similar devices may be used for sampling and testing downhole fluids sampled by thetool100.
• In the non-limiting example ofFIG. 1, apump142 is in fluid communication withfluid conduits112 and one ormore ports102 for permitting downhole fluids to flow into thetool100 and through, into, and/or around the one or more devices disposed within thecarrier134. Sampled downhole fluids may be expelled from thetool100 via one ormore outlet ports114 positioned as desired on thecarrier134 and in fluid communication with thefluid conduits112. The downhole fluids may include, but are not limited to, polar and non-polar drilling fluids, return fluids, and/or formation fluids. The downhole fluids may include one or more hydrocarbon species containing twenty or more carbon atoms, for example asphaltenes having one or more viscous, high molecular weight hydrocarbons. These highly viscous, and often adhesive, downhole fluids may tend to buildup on wettedsurface elements200 of downhole and/or uphole devices and on thesurface elements300 of other devices that contact the downhole fluids during sampling or testing. Several exemplary downhole devices such as thespectrometer104,sensors118,120,122,124 and/orfluid sample chambers136 includerespective surface elements200,300 that will contact downhole fluid as depicted in the exemplary embodiment ofFIG. 1.
• Still referring toFIG. 1, the downhole fluid may flow throughfluid conduits112, to thespectrometer104. Anexemplary spectrometer104 may include alight source106, asample region108, and one ormore detectors110,111 for measuring the optical properties of downhole fluid within afluid sample region108. Thefluid sample region108 includes asurface element200 in contact with fluid in thefluid sample region108. The downhole fluid may be conveyed via thefluid conduits112 to avalve144 that may be actuated to convey the downhole fluid to a test section where asensor interface106 may be coupled to sensors, such as thesensors118,120,122, and124 mentioned above that haverespective surface elements300 contacting the downhole fluid flowing in the test section. Thesensors118,120,122,124 may include any number of sensor types. For example, sensors in the test section may include atemperature sensor118, apressure sensor120, astress sensor122, adistance sensor124 as shown or any other sensor type that may be useful in estimating downhole fluid properties. Theexemplary temperature sensor118 can include at least one temperature sensitive device, for example a thermocouple, thermistor, resistance temperature detectors (RTD), or any combination of one or more devices, suitable for converting the temperature of the fluid flowing past the sensor into one or more signals. Thepressure sensor120 can include at least one pressure sensitive device, for example a mechanical deflection sensor, strain gauge, piezoresistive semiconductor sensor, micro-electromechanical system (MEMS) sensor, vibrating element sensor, variable capacitance sensor, or any combination thereof. The one ormore stress sensors122 can include one or more acceleration and/or vibration sensors. Downhole fluid may be expelled before or after entering the test section or may be retained for later testing.
• In some embodiments, thevalve144 may be actuated to expel the downhole fluid from the tool via anoutlet port114 positioned upstream of the test section. The downhole fluid may be further conveyed via thefluid conduits112 to anoutlet port114 downstream of the test section or may be directed via avalve146 to thesampling chamber116. In some embodiments, the sampling chamber may be flushed using anothervalve148 and outlet port positioned downstream of thesampling chamber116. Thesampling chamber116 may include asurface element200 that is in contact with fluid in thesampling chamber116. Theseveral surface elements200,300 are further described below with reference toFIGS. 2 and 3.
• FIG. 2 shows a cross-sectional view of anexemplary surface element200 according to one or more embodiments of the disclosure. Asurface element200 according to several exemplary embodiments includes asubstrate210 with asurface portion205 comprising a fluid-repellent material220. Thesurface portion205 may be chemically and/or mechanically bonded to thesubstrate210. The fluid-repellent material220 may be selected to prevent the buildup and/or adhesion of thedownhole fluid215 to thesurface portion205, thereby improving the flow of thedownhole fluid215 past or along thecoated substrate210. The fluid-repellent material220 can include, but is not limited to, polytetrafluoroethylene (PTFE) compounds, fluorocarbon resins, fluoropolymers, silicone polymers, mixtures thereof and/or combinations thereof. The fluid-repellent material220 can be applied to the substrate during or after fabrication of the wetted surfaces in both thetool100 and thecarrier134 thereby providing a fluid-repellent surface portion205 on the wetted surfaces. The fluid-repellent material220 can be applied as a liquid, solid, or gas through any deposition process amenable to providing a continuous, non-porous coating on the selected wetted surfaces within thecarrier134. For example, the fluid-repellent material220 can be applied to thesubstrate210 using application techniques including, but not limited to, powder coating, spraying, immersion, electrostatic precipitation or deposition, gas phase condensation, or any combination thereof. Thesurface element200 may be incorporated as a portion of any number of the fluid-contacting surfaces described above and shown inFIG. 1. In some examples, thesurface element200 may form a portion of a sensor that contacts downhole fluids as described below with reference toFIG. 3.
• FIG. 3 depicts a non-limiting example of an illustrativedevice cross section300 showing asurface element200 having acoated substrate210 according to one or more embodiments of the disclosure. Thesubstrate210 can include any wetted internal or external surface disposed in, on, or about thetool100 and/orcarrier134. The exemplary view ofFIG. 3 shows one ormore sensors305 disposed on thesubstrate210. Thesensors305 can be in fluid and/or electrical communication with other elements, components and/or devices within thecarrier134 via one or more electrical conductors and/or fluid conduits shown schematically at310. Thesensors305 may include, but are not limited to, one or more pressure sensors, temperature sensors, optical sensors, fluorescence sensors, flow rate sensors, viscosity sensors, or any combination thereof. Thesensors305 can include one or more wavelength specific light generators and/or receivers. Where the one ormore sensors305 include optical devices such as optical sensors, wavelength specific light generators and/or receivers, the fluid-repellent material205 disposed on or about thesensor305 can be translucent and/or transparent to one or more selected light frequencies generated and/or received by the one ormore sensors305. The several sensor embodiments may be incorporated into atool100 for sampling downhole fluids as described above and shown inFIG. 1, and as mentioned, the tool may100 a surface tool or a downhole tool. Downhole tools may be conveyed via wireline or drill string as described below.
• FIG. 4 shows a non-limiting example of awell logging apparatus400 according to several embodiments of the disclosure. Thewell logging apparatus400 is shown disposed in awell borehole402 penetrating one ormore formations404 for making measurements of properties of theformations404. Theborehole402 is typically filled and/or pressurized with drilling fluid to prevent formation fluid influx.
• Atool string406 can be lowered into thewell borehole402 using one ormore cables408 that can be spooled and unspooled using a winch ordrum410. At least one of thecables408 can be an armored communications cable containing one ormore communications buses136. Thetool string406 can be in two-way communication withsurface equipment412 using thecommunications cable136, containing one or more optical fibers and/or electrical conductors, within thearmored communications cable408. As depicted inFIG. 4, thetool string406 can include one ormore tools100 as described in detail with respect toFIG. 1 above. Thetool string406 can preferably be centered within thewell borehole402 using one ormore centralizers422a,422battached to thetool string406 at axially distant locations. Thecentralizers422a,422bcan be of types well known in the art, such as bowsprings.
• Thesurface equipment412 can include one ormore telemetry systems414 for communicating control signals and data to thetool string406 and one ormore computers416. Thecomputer416 can include one ormore recorders418 for storing, plotting, and/or recording data acquired using the one or moredownhole tools100 and transmitted via thecommunications bus136 to thesurface equipment412. Circuitry for controlling and operating the one ormore tools100 can be located within thetool string406, for example within one ormore electronics cartridges424. The circuitry can be connected to the one ormore tools100 using one ormore connectors426. In several embodiments, thetool100 can incorporate one or more high-gain semiconductor devices such as one or more of the devices described herein with respect toFIG. 1,FIG. 2, and/orFIG. 3.
• FIG. 5 is an elevation view of a simultaneous drilling andlogging system500 that may incorporate non-limiting embodiments of the disclosure. A well borehole502 can be drilled into the earth under control of surface equipment including adrilling rig506. In accordance with a conventional arrangement,rig506 includes adrill string514. Thedrill string514 can be a coiled tube, jointed pipes or wired pipes as well known by those skilled in the art. In one example, a bottom hole assembly (“BHA”)550 may include one ormore tools100 such as one or more of the devices described herein with respect toFIG. 1,FIG. 2, and/orFIG. 3.
• While-drilling tools will typically include adrilling fluid526 circulated from amud pit528 through one or more mud pumps530, past one or more desurgers532, and through one or moremud supply lines534. Thedrilling fluid526 can flow through a longitudinal central bore in thedrill string514 exiting through one or more jets (not shown) disposed about the lower face of adrill bit524. Return fluid containing drilling mud, cuttings and formation fluid can be returned to the surface via theannular region538 that exists between the outer surface of thedrill string514 and the inner surface of theborehole502. Return fluid exiting theannular region538 can be directed vialine542 to themud pit528 for analysis, recovery, recycle and/or disposal.
• The system as depicted inFIG. 5 can use any conventional telemetry methods and devices for communication between the surface and one or more downhole components and/ortools100. In the embodiment shown mud pulse telemetry techniques can be used to communicate data from downhole to the surface during drilling operations. Asurface controller548 can be used for processing commands and other information used in the drilling operations.
• In one or more embodiments, adownhole drill motor536 can be included in thedrill string514 for rotating thedrill bit524. In several embodiments, the while-drilling tool100 can incorporate one or more high-gain semiconductor devices such as any of the devices described herein and shown inFIGS. 1 through 3.
• Atelemetry system552 may be located in a suitable location on thedrill string514 such as above thetool100. Thetelemetry system552 may be used to transmit and/or receive commands and/or data to thesurface controller548 using mud pulse telemetry or by other communication techniques known in the art. For example, acoustic pipe telemetry and/or wired pipe telemetry may be used.
• Thesurface controller548 can include one or more data processing systems, one or more data storage systems, one or more data recording systems, one or more data handling peripherals, or any combination thereof. Thesurface controller548 can also respond to user commands entered through a suitable man-machine interface, such as a keyboard. In one non-limiting embodiment, theBHA550 can incorporate various aspects of the disclosure, including, but not limited to, sensors and logging-while-drilling (LWD) devices to provide information about the formation, downhole drilling parameters and the mud motor.
• Several operational examples will now be described with reference to the several exemplary embodiments described above and shown inFIGS. 1-5. In one or more exemplary embodiments, theillustrative tool100 as depicted inFIG. 1 can be deployed downhole via wireline or while drilling, as described above and shown inFIG. 4 andFIG. 5. A downhole fluid can be sampled by introducing a portion of the downhole fluid into thetool100 via theinlet port102 disposed about thecarrier134. Within thetool100, the downhole fluid can be pumped using thepump142 to convey the downhole fluid through one or morefluid conduits112, to other devices in thetool100.
• In this operational example, the fluid is conveyed to thespectrometer104 where properties of the fluid within thesample region108 are estimated based upon the transmissive, refractive and/or reflective properties of the fluid within thesample region108. Fluid leaving thesample region108 may be directed to an outlet port or to a fluid test section using thevalve144 installed at the discharge of thesample region108 in thespectrometer104. The fluid contacting thesurface element200 of thesample chamber108 is repelled from the surface element by the fluidrepellent material220 forming a portion or thesurface element200. Fluid may be discharged from the tool for any number of reasons. Sometimes the fluid is discharged until the fluid content is substantially free of wellbore fluids so that fluid entering the test section is substantially pristine formation fluid. Having a fluid repellent material as a portion of the surface element helps to provide self cleaning for thesample region108. When further testing is desired, then the fluid is directed to the test section via thevalve144, to theseveral sensors118,120,122, and/or124 in the test section.
• The physical properties of the fluid in the test section, such as density, and downhole conditions such as temperature and pressure, are estimated using thesensors118,120,122,124. The fluidrepellent material220 forming a portion of thesurface element300 of the several sensors helps repel fluid from the sensor surfaces contacting the fluid. In this manner, the sensor sensitivity may be better maintained due in part to keeping the sensing surface clean of fluid residue. Fluid passing through the test section may be directed to theoutlet port114 downstream of the test section or to thefluid sample chamber116 via thefluid conduits112.
• The fluid contained within thesample chamber116 may be retained for later analysis by closing the two-way valve148 located on the discharge of thesample chamber116. Alternatively, the fluid within thesample chamber116 can be rejected from thetool100 by opening the two-way valve148, permitting the fluid within thesample chamber116 to flow through thefluid conduit112 to thedischarge port114. The fluidrepellent material220 used as a portion of the sample chamber surface element helps when flushing fluid samples from the sample chamber.
• The present disclosure is to be taken as illustrative rather than as limiting the scope or nature of the claims below. Numerous modifications and variations will become apparent to those skilled in the art after studying the disclosure, including use of equivalent functional and/or structural substitutes for elements described herein, use of equivalent functional couplings for couplings described herein, and/or use of equivalent functional actions for actions described herein. Such insubstantial variations are to be considered within the scope of the claims below.

Claims (23)

1. An apparatus for sampling a downhole fluid comprising:

a tool having at least one surface element wetted by a downhole fluid, the at least one surface element including a fluid-repellant material disposed on a substrate for repelling some or all of the downhole fluid wetting the at least one surface element.

2. The apparatus ofclaim 1, wherein the tool is wetted by the downhole fluid while deployed downhole via wireline or while drilling.

3. The apparatus ofclaim 1, wherein the tool is wetted by the downhole fluid while deployed in a surface location.

4. The apparatus ofclaim 1, further comprising one or more fluid test instruments having one or more surface elements.

5. The apparatus ofclaim 4, wherein the tool includes one or more sensors exposed to the downhole fluid.

6. The apparatus ofclaim 5, wherein the one or more sensors comprise one or more pressure sensors, temperature sensors, viscosity sensors, density sensors, optical sensors, fluorescence sensors, and flow rate sensors.

7. The apparatus ofclaim 1, wherein the tool comprises a wavelength spectrum light generator and the fluid-repellant material is transparent to at least a portion of the wavelength spectrum generated by the wavelength spectrum light generator.

8. The apparatus ofclaim 1, wherein the downhole fluid comprises one or more of a drilling fluid, a return fluid, and a formation fluid.

9. The apparatus ofclaim 1, wherein the downhole fluid comprises hydrocarbons having twenty or more carbon atoms per molecule.

10. The apparatus ofclaim 1, wherein the downhole fluid comprises one or more of a polar fluid, and non-polar fluid.

11. The apparatus ofclaim 1, wherein the fluid-repellent material comprises one or more of polytetrafluoroethylene (PTFE) compounds, fluorocarbon resins, fluoropolymers, silicone polymers, and fluorocarbon polymers.

12. The apparatus ofclaim 1, wherein the fluid-repellent material comprises a coating applied to the substrate by one or more of powder coating, spraying, immersion, and electrostatic deposition.

13. A method for sampling a downhole fluid comprising:

wetting at least one surface element of a tool with a downhole fluid the at least one surface element comprising a fluid-repellant material disposed on a substrate; and

repelling some or all of the downhole fluid from the at least one surface element.

14. The method ofclaim 13, wherein the wetting of the surface element with the downhole fluid occurs while the tool is deployed downhole via wireline or a drilling sub.

15. The method ofclaim 13, wherein wetting the at least one surface element occurs while the tool is deployed in a surface location.

16. The method ofclaim 13, wherein of a drilling fluid, a return fluid, and a formation fluid.

17. The method ofclaim 13, wherein wetting the at least one surface element includes wetting with one or more hydrocarbons having twenty or more carbon atoms per molecule.

18. The method ofclaim 13, wherein wetting the at least one surface element includes wetting with one or more polar fluids, and one or more non-polar fluids.

19. The method ofclaim 13, wherein the fluid-repellent material comprises one or more of polytetrafluoroethylene (PTFE) compounds, fluorocarbon resins, fluoropolymers, silicone polymers, and fluorocarbon polymers.

20. The method ofclaim 13, wherein the fluid-repellent material comprises a coating applied to the substrate by one or more of powder coating, spraying, immersion, and electrostatic deposition.

21. A method for manufacturing apparatus for sampling a downhole fluid comprising:

disposing a fluid-repellant material on a substrate to form a surface element;

forming at least a portion of a downhole fluid sampling tool using the surface element, the surface element being wettable by a downhole fluid during operation of the downhole fluid sampling tool.

22. The method ofclaim 21, wherein the fluid-repellent material comprises one or more of polytetrafluoroethylene (PTFE) compounds, fluorocarbon resins, fluoropolymers, silicone polymers, and fluorocarbon polymers.

23. The method ofclaim 21, wherein the fluid-repellent material comprises a coating applied to the substrate by one or more of powder coating, spraying, immersion, and electrostatic deposition.

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