WO2009052235A1

WO2009052235A1 - Formation sampler with cleaning capability

Info

Publication number: WO2009052235A1
Application number: PCT/US2008/080077
Authority: WO
Inventors: Robert M. Leveridge; Anthony R.H. Goodwin; Shawn David Taylor
Original assignee: Schlumberger Canada Limited; Schlumberger Technology B.V.; Prad Research And Development Limited; Services Petroliers Schlumberger; Schlumberger Holdings Limited
Priority date: 2007-10-19
Filing date: 2008-10-16
Publication date: 2009-04-23
Also published as: CA2702868A1; CA2702868C

Abstract

Sampling tools are used to extract samples of underground reservoir fluids. The extracted samples can either be analyzed down-hole or stored in a container for subsequent laboratory analyses. In either case, the fluid sample must be representative of both the chemical composition and physical properties of the formation fluid about the volume of sampling acquisition. Often, one sampling tool is used to acquire fluids from several locations within a reservoir. It is highly likely that fluid sampled at a first location in the reservoir may have adhered to the inner walls of the flow line or other hydraulic components of the sampling tool. Consequently, fluid extracted from a second location within the same reservoir may be contaminated by that remaining from the first acquisition. As a consequence, the chemical composition and physical properties determined by analyses of the second fluid may not actually be of the formation fluid but of a mixture of the first and second fluid and thus be unrepresentative of the formation fluid at that second location. Such mixing of fluids from two zones of the same reservoir may plausibly lead to wrong decisions regarding the fluid type within the reservoir. One such example regards the distinction of a fluid as a volatile oil when it is actually a gas condensate, a decision that would have catastrophic consequences on the designed and commissioned surface separator systems.

Description

Formation Sampler with Cleaning Capability

Background of the Disclosure

[0001] Sampling tools are used to extract samples of underground reservoir fluids. The extracted samples can either be analyzed down-hole or stored in a container for subsequent laboratory analyses. In either case, the fluid sample must be representative of both the chemical composition and physical properties of the formation fluid about the volume of sampling acquisition. Often, one sampling tool is used to acquire fluids from several locations within a reservoir. It is highly likely that fluid sampled at a first location in the reservoir may have adhered to the inner walls of the flow line or other hydraulic components of the sampling tool. Consequently, fluid extracted from a second location within the same reservoir may be contaminated by that remaining from the first acquisition. As a consequence, the chemical composition and physical properties determined by analyses of the second fluid may not actually be of the formation fluid but of a mixture of the first and second fluid and thus be unrepresentative of the formation fluid at that second location. Such mixing of fluids from two zones of the same reservoir may plausibly lead to wrong decisions regarding the fluid type within the reservoir. One such example regards the distinction of a fluid as a volatile oil when it is actually a gas condensate, a decision that would have catastrophic consequences on the designed and commissioned surface separator systems.

Summary of the Disclosure

[0002] The present disclosure addresses the above-described problem of cross contamination between two sampling locations with an apparatus described herein that may be used to advantage, but not exclusively, for sampling a reservoir fluid having very viscous hydrocarbons such as heavy oils.

[0003] For example, the present disclosure introduces a method of cleaning a portion of the internal tubulars that form the passage through which hydrocarbon fluid flows within a down- hole tool conveyed by any method available to the industry including cables and drill pipe. In the remainder of this application, we may refer to this as a flow line, a hydraulic circuit, and/or a portion of a hydraulic circuit, in a downhole tool. In at least one embodiment, the method comprises lowering a tool in a borehole, the tool having a flow line and/or other portion of a hydraulic circuit for facilitating formation fluid flow; cleaning at least a portion of the hydraulic circuit portion, wherein cleaning the hydraulic circuit portion comprises at least one of purging and flushing the hydraulic circuit portion with a cleaning fluid to remove contaminant from the hydraulic circuit portion; and flowing fluid from the formation through the cleaned portion of the hydraulic circuit portion. The method may further comprise heating the hydraulic circuit portion to reduce adhesion of the contaminant to a wall of the hydraulic circuit portion. The method may further comprise altering the temperature of the hydraulic circuit portion to reduce adhesion of the contaminant to the hydraulic circuit portion. The cleaning fluid may comprise at least one of a solvent, a bead loaded fluid, fluid with an additive for modifying interfacial tension, and an immiscible fluid having a viscosity that acts as a displacement fluid. The method may further comprise scraping a wall of the hydraulic circuit portion with a moveable device. The method may further comprise exposing at least one of a wall of the hydraulic circuit portion and fluid in the hydraulic circuit portion to a vibration source. The method may further comprise at least one of stretching and shortening a dimension of the hydraulic circuit portion. The hydraulic circuit portion may comprise a memory shape alloy.

[0004] The present disclosure also introduces an apparatus for cleaning a flow line and/or other portion of a hydraulic circuit in a downhole tool. In at least one embodiment, the apparatus comprises an inlet selectively coupled fluidly to a formation; a flow line and/or other portion of a hydraulic circuit fluidly coupled to the inlet; means for facilitating formation fluid flow from the inlet; means for introducing cleaning fluid into the hydraulic circuit portion; and means for PATENT DKT. NO. 20.3106NP cleaning at least a portion of the hydraulic circuit portion with the cleaning fluid. The means for facilitating formation fluid flow may include a pump and at least one flow line fluidly coupled between the inlet and the pump.

[0005] The present disclosure also introduces a method for cleaning a sensing face of a sensor of a hydraulic circuit in a downhole tool. In at least one embodiment, the method comprises lowering a tool in a borehole, the tool having a flow line and/or other portion of a hydraulic circuit for facilitating formation fluid flow; sensing a parameter of at least one of a formation fluid and a wellbore fluid with a sensor; cleaning a sensing face of the sensor disposed in the hydraulic circuit portion; and flowing fluid from the formation towards the sensor, wherein cleaning the sensing face involves purging or flushing at least a portion of the hydraulic circuit portion with a cleaning fluid.

PATENT DKT. NO. 20.3106NP

Brief Description of the Drawings

[0006] The present disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

[0007] Fig. 1 is a schematic view of apparatus according to one or more aspects of the present disclosure.

[0008] Fig. 2 is a flow-chart diagram of at least a portion of a method according to one or more aspects of the present disclosure.

[0009] Fig. 3 is a schematic view of apparatus according to one or more aspects of the present disclosure.

[0010] Fig. 4 is a schematic view of apparatus according to one or more aspects of the present disclosure.

[0011] Fig. 5 is a schematic view of apparatus according to one or more aspects of the present disclosure.

[0012] Fig. 6 is a schematic view of apparatus according to one or more aspects of the present disclosure.

PATENT DKT. NO. 20.3106NP

Detailed Description

[0013] It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. [0014] Fig. 1 is a schematic view of an embodiment of a wireline tool string 100 according to one or more aspects of the present disclosure. The tool string 100 has a power and telemetry cartridge 105 configured for communicating power and data between the tool string 100 and the surface via a cable 107. The tool string 100 comprises a heating module 110 configured for increasing the temperature of the formation F and reducing the viscosity of the formation fluid. The tool string 100 also comprises a nuclear magnetic resonance (NMR) tool 115 configured to monitor formation fluid properties related to the formation fluid viscosity. The tool string 100 also comprises a sampling tool 120 comprising a probe module having an extendable probe 122 configured to establish a fluid communication between flow lines in the tool and the borehole wall 102. Such flow lines may include a clean-up flow line 125 and a sample flow line 127. The sampling tool 120 also comprises or is coupled to one or more pump modules 130a/ 130b configured to draw fluid from the formation F into the flow lines. The sampling tool 120 further comprises or is coupled to a DFA module 135 configured to monitor the properties of the fluid in the flow lines of the sampling tool 120. The sampling tool 120 also comprises or is coupled to a sample chamber carrier 140 having one or more containers 142 configured to capture and convey fluid samples.

[0015] During formation fluid sampling, the tool string 100 is located at a point of interest in the formation F. The heating tool 110 may be operated to increase the temperature of a portion of the formation F. By subsequently moving the tool string 100 upwards to place the NMR pad PATENT DKT. NO. 20.3106NP

117 of the NMR module 115 in front of the now heated portion of the formation F, the formation heating process can be monitored using the NMR module 115. However, NMR sensors 118 of the NMR module 115 may be located in close proximity to the heat source 112 of the heating tool 110, in which case moving the tool string 100 may not be needed.

[0016] Once sufficient heating has been achieved, the probe 122 is disposed close to the heated portion of the formation F and extended toward the borehole wall 102. Fluid is drawn into the sample flow line 127 and the clean-up flow line 125 using pumps 132a/b of the pump modules 130a/b. The pressure and temperature in the flow lines may be measured with pressure (and temperature) sensors 133a/b. Fluid viscosity, density, NMR spectrum, optical spectrum, etc. may also be monitored by sensors 137a/b/c in the DFA module 135. The DFA module 135 may also be provided with sensors configured to detect particular chemical species (e.g., H2S). [0017] The measured fluid properties may then be displayed at the surface. They may be used for controlling the sampling job (sampling flow rate) and also for obtaining information about the formation fluid. If desired, a sample may be stored in one or more of the sample chambers 142 and brought up at the surface for further analysis. Once the sampling job is finished, setting pistons 123 of the sampling module 120 are retracted and the downhole tool 100 may be moved to another location of the reservoir.

[0018] It will be appreciated that, while moving the downhole tool 100 to another location of the reservoir, the formation fluid that still exists in the flow lines, connectors, valves, pumps, sensors, and another components of the tool 100 will begin to cool down. If the formation fluid is or contains heavy oil, the formation fluid viscosity will also increase as the temperature decreases, making the captured formation fluid less susceptible to removal by pumping other fluid that might, for example, occur when pumping to clean the sample by removing filtrate or drilling mud. The more viscous oil that remains in the tubular may also adhere to the walls of the hydraulic components. In the extreme case, the flowlines, sensors, and/or any other hydraulic components may even become blocked by the retained formation fluid. [0019] Additionally, when another part of the formation is tested, a fluid having different properties will enter the downhole tool 100. If the new fluid is heated, its viscosity will be lower than the cooled fluid that is still coating the hydraulic components. Therefore, the new fluid will not efficiently displace the old fluid that coats the walls of the hydraulic circuit. In some cases, the new fluid will very slowly mix with the old fluid and contaminate it. There is also the PATENT DKT. NO. 20.3106NP potential for the old cooled fluid to coat the sensors. The measurements performed by such sensors will then be biased. For example, if the measurement is dependent on the fluid within a skin depth of the sensor, if as most are, the result will reflect the old or new fluids or a mixture of both unless subsequent fluid flown in the flow-lines displaces the old fluid. Thus, drawing fluid from the bore-hole or formation for the purpose of cleaning the flow-line will be in addition to the volume required to extract the invased bore-hole fluids in the formation so that the fluid obtained is in terms of the chemical composition and physical properties representative of the formation fluid. To draw a large amount of fluid from a heavy oil formation requires energy be used to mobilize the hydrocarbon by increasing the formation temperature and owing to either the temperature control of either a resistive heater or electromagnetic source of energy. The former requires time for propagation of a thermal wave by thermal diffusivity while the latter also requires time to select the appropriate frequency for the given electrical conductivity of the formation and avoiding excessive temperature increments for particular parts of the formation. Excessive temperature increments may give rise to changes in the chemical composition by cracking and polar molecules can absorb disproportionate amounts of electromagnetic energy and result in local heating through motion that can also result in changes in the chemical composition. These processes are costly. Indeed, variations in chemical composition may result in the deposition of solids.

[0020] In order to reduce the effect of chemical composition changes, and to expedite the cleaning of a flow line and/or other portion of the hydraulic circuit of the sampling tool 120 and related components of the downhole tool 100, the method 200 depicted in Fig. 2 may be used. The method 200 allows for in-situ cleaning of at least a portion of the sampling tool 120 and other components of the downhole tool 100. After the downhole tool 100 is lowered downhole (205) and fluid is drawn from a first location in the reservoir (210), the sampling job proceeds to one or more other locations along the borehole (215). The new location is presumably but not necessarily in the same reservoir.

[0021] Testing is then performed to determine if clean-up of a flow line and/or other portion of the hydraulic circuit of the tool is desired (220). This may be achieved by a surface operator, in view of the sampling data obtained at the first location. For example, if the fluid viscosity of the fluid obtained at the first location is high at downhole conditions, a clean-up may be desired. Alternatively, mud or another known fluid (conveyed down-hole in a container) may be flowed PATENT DKT. NO. 20.3106NP in the sampling tool and the response of the sensor in the DFA module may be monitored; the properties of the fluid are known and so is the response of the sensor. If the properties measured by the sensors match the properties expected for the fluid flown in the tool (e.g., the mud properties), this may indicate that the sensing face of the sensor in the DFA module is clean. This may further indicate that the other hydraulic components of the sampling tool are clean, and that sufficient time has been employed in cleaning.

[0022] In the case a clean-up of the tool is desired, the clean-up may be initiated (225). The clean-up comprises flowing a flushing fluid through at least a portion of the downhole tool hydraulics. However, flushing may not suffice to eliminate a film of very viscous oil that may have formed on the walls of the flow lines for examples. Indeed, if the flushing fluid is less viscous than the contaminating oil, a significant volume of oil may be bypassed by the flushing fluid and may remain in the sampling tool. This contaminating oil may gradually mix with the sampled oil, modifying its chemical properties. Thus, flushing may be assisted by a viscosity reduction of the contaminating oil (with heat and/or a solvent), a mechanical action on the oil (scraping, abrasion, vibration), and/or a change of the shape of the components of the hydraulic circuit.

[0023] The method 200 may also comprise an optional step of monitoring the cleaning process (230). For example, sensors (e.g., thermocouples) may be used for measuring and controlling the temperature of the components of the tool hydraulics. The temperature may be controlled to achieve a desired limit, at which the tool components survive and at which oil remaining in the tool is expected to have a significantly reduced viscosity. Other sensors (e.g., position sensors, acoustic impedance sensors) may be used to monitor a quantity related to the efficiency of the cleaning process. Alternatively, or additionally, sensors in the DFA module may be used for monitoring a fluid property as the flushing fluid circulates in the downhole tool. When the sensor of the DFA module indicates a stable reading of a fluid property, and if this property value is close (that might be within the anticipated uncertainty of the combined measurements within an acceptable certainty or confidence interval or a predetermined value found suitable by prior practice) to the expected value for the flushing fluid, this may indicate that the clean-up can be terminated. Whether monitored or not, the clean-up is terminated in step 235, perhaps after the expiration of a predetermined time limit, for example. The sampling PATENT DKT. NO. 20.3106NP operation may continue by drawing fluid from a second location in the reservoir (240) and returning to step 220 for the next iteration of at least a portion of the method 200.

[0024] Returning to Fig. 1, the downhole tool 100 may comprise a heating element, such as a heating wire 145. The heating wire 145 is thermally coupled to the fluid drawn into the sampling tool 120. For example, the tool hydraulics are preferably made of material that conduct heat and that have a low heat capacity. The heating wire 145 may be wrapped around or partially embedded into the material from which the hydraulic lines are made.

[0025] The heating wire 145 may span from the sampling tool inlet (e.g., probe 122) to the last hydraulic component for which sample purity matters (in the illustrated example, all the way to the sample storage and possibly also transportation chambers 142). In the shown example, only the sample line 127 is shown equipped with the heating wire 145, but both additional flow lines (including clean-up flow line 125) may also be equipped with the heating wire 145 and/or other viscosity reducing device. The heating wire can be a wire of known and suitable resistance.

[0026] The heating wire 145 may be energized by an electrical current at a voltage (or voltage at a current) power source (not shown) and thus be configured to selectively deliver energy to the fluid in the hydraulic circuit for lowering its viscosity. One or more thermocouples may be used for monitoring the temperature of the hydraulic components and for controlling the heating process.

[0027] Once the tool hydraulics are hot, mud from the wellbore may be pumped and used for flushing the remaining oil that coats the tool hydraulics (the probe 122 is not extended). A property measured by one of the sensors may be monitored for confirming that the sampling tool

120 is clean (e.g., drilling mud properties are measured). Once the sampling tool 120 is clean, a new sampling operation may begin by extending the probe 122 against the formation.

[0028] Thus, by delivering heat to the oil that adheres to the hydraulic components of the tool 100, the viscosity of the oil coating the hydraulic components may be reduced. As the viscosity of the fluid is lowered, the cleaning of the hydraulic circuit by circulating a fluid (e.g. mud) is enhanced. Thereby, cross-contamination of fluid between two sampling stations may be reduced or eliminated. This, in turn, may lead to more efficient sampling operations with more accurate in-situ fluid property data, better quality samples, reduced sampling volume to achieve PATENT DKT. NO. 20.3106NP a clean sample, reduced energy needed to get a sample, and/or reduced time needed to get a representative sample, among other possible advantages.

[0029] In an alternative example, heat is not generated by the heating wire 145 as shown in Fig. 1, but by another tool component. The additional tool component may also be employed in conjunction with the heating wire 145. The additional tool component could be power electronics (electronics that transform the electrical power obtained from the wireline cable into power that is usable by, e.g., the pump motors in the tool string). The additional tool component could alternatively be a heat pump disposed in one of the tool modules, the heat pump having a cold end thermally coupled to a source (e.g., wellbore fluid, power electronics component) and a hot end thermally coupled to a heat transport device. For both of these cases, the heat is conveyed from the additional tool component to the hydraulic components in the tool string with a heat transport device. The heat transport device may be a heat pipe and/or a hydraulic circuit circulating a fluid having an appropriate thermal capacity and can circulate in the temperature range required of the system (that might be an energy transfer medium of water or butane etc.). The heat transport device may thus thermally couple the additional tool component (heat source) to the oil stuck in the tool hydraulics.

[0030] Viscosity-reducing heat may also or alternatively be provided to a flushing fluid contained in a sample bottle. One such embodiment in shown in Fig. 3. The fluid is heated and then circulated in the hydraulic circuit of the tool 300. The hot fluid transfers part of the heat to the oil that coats the wall of the hydraulic circuit. The heated oil is removed by circulating or by pulsing clean fluid in the hydraulic circuit.

[0031] The tool 300 includes a heating module 310 that includes a flushing fluid container 312 and a heater 314. A valve 301 controls fluid flow from the container 312. Fluid flowing from the valve 301 is either directed out of the tool 300 via a valve 302 or to an inter-module connector 316.

[0032] The tool 300 also includes a sampling module 320, similar to the sampling module 120 shown in Fig. 1, and including a probe 322. Fluid flowing from the inter-module connector 316 is either directed into the probe 322 and/or to another inter-module connector 324 via valves 303 and 304.

[0033] The tool 300 also includes one or more pump modules 330, similar to the pump module 130a or 130b shown in Fig. 1, and including at least one bidirectional pump 332 PATENT DKT. NO. 20.3106NP configured to draw fluid from the formation F into sample flow line 334 and/or clean-up flow line 336.

[0034] The tool 300 also includes a sample chamber carrier 340 comprising at least one sample chamber 342. For example, one of the sample chambers 342 shown in Fig. 3 receives fluid from the sample flow line 334 via valve 305. The carrier 340 may also comprise valve 306 for directing fluid flow from sample flow line 334 to out of the tool 300, and/or valve 307 for directing fluid flow from clean-up flow line 336 to out of the tool 300. The carrier 340 may also include a heater 344 proximate one or more of the sample chambers 342, and/or a heater 346 proximate one or more of the flow lines.

[0035] Note that in the tool of 300 Fig. 3, the probe 322 has an outer seal 326 and an inner seal 328. The inner seal 328 can be selectively moved in the direction indicated by the arrow and can be either in contact with the borehole wall 350 or recessed with respect to the formation wall 350 (further details of this configuration, if needed, are shown in U.S. Pat. No. 6,964,301, which is hereby incorporated by reference). The outer seal 326 is applied against the formation and the inner seal 328 may be recessed during the clean up.

[0036] In one example, valves 302, 303, and 305 are closed, and valves 301, 304, and 306 are open. By pumping down with the pump on the sample flow line 334, hot flushing fluid contained in the upper bottle 312 is routed through open valve 301 into the sealed interval by the probe 322, then into the sample flow line 334, down to the exit port associated with the valve 306. In this configuration, the sample flow line 334 is efficiently cleaned from the 322 probe to a flow line associated with the exit port.

[0037] In another example, valves 301, 303, and 306 are closed, and valves 302, 304, and 305 are opened. By pumping up with the pump 332 on the sample flow line 334, hot flushing fluid contained in a lower bottle 342 is routed through the sample flow line 334 through open valve 305, into the sealed interval by the probe 322, then into the clean up flow line 336, up to the exit port associated with the valve 302.

[0038] In another example, only a lower sample bottle 342 is provided. The probe 322 is retracted and does not seal with the wellbore wall 350 during the cleaning operation. Fluid (e.g., mud or cleaning fluid disposed in a sample bottle), is heated and circulated up towards the probe 322, where it is dumped into the wellbore. PATENT DKT. NO. 20.3106NP

[0039] The flushing fluid in any embodiment within the scope of the present disclosure may be water or any immiscible fluid of greater or lesser viscosity, or may be a liquid that is miscible with formation fluid, such as a solvent. In some cases, a polar solvent may be preferred; however, non-polar solvent may also be used. The solvent may be heated as described herein, but it is also possible to use a solvent that has not been heated.

[0040] The flushing fluid may be a liquid having an additive for facilitating the removal of the oil coating on the hydraulic circuit. For example, the fluid may comprise beads or abrasive particles. The flushing fluid may contain an additive for modifying interfacial tension. The cleaning fluid may comprises at least one of a solvent, a bead loaded fluid, fluid with an additive for modifying interfacial tension, and an immiscible fluid having a viscosity that acts as a displacement fluid. However, other cleaning fluids are also within the scope of the present disclosure.

[0041] Although heating has been discussed in detail, more generally, the temperature of formation fluid in the flow line may be altered. Thus, the flushing or purging of the flow line may be assisted by chilling the flow line. To that respect, a heat pump may be used.

[0042] Fig. 4 depicts another way for assisting the cleaning of a flow line. In the illustrated embodiment, a movable device is used for scraping the walls of the flow line. For example, a brush or a scraping plug 410 is swept along a portion of a flow line 420 of a sampling tool. The brush or scraping plug 410 may be affixed to one extremity of a flexible shaft 430. The flexible shaft 430 may extend through a seal 425, and may be wound around a drum 440 that is operatively coupled to a motor 450. As shown, the brush 410 may be disposed in a rat hole 460 while the tool is in sampling mode. However, other equivalent devices (e.g., analogous to a PIG used in natural gas transmission lines) may alternatively be used.

[0043] Fig. 5 shows yet another way for cleaning of a flow line. In the illustrated example, an auger or Archimedes screw 510 is snuggly fitted into a portion of a flow line 520 of the sampling tool. The auger 510 is coupled to a motor 550, and may extend through a seal 525.

The motor 550 may be activated for cleaning, or for sampling the oil.

[0044] Fig. 6 shows still another way for assisting the cleaning of a flow line. In the illustrated example, a flow line 620 is made of a shape memory alloy. Sampling is performed while the flow line 620 has a small diameter. When cleaning is desired, it is assisted by increasing the diameter of at least a portion 625 of the flow line 620, as indicated by the arrows PATENT DKT. NO. 20.3106NP in Fig. 6. This may be achieved by modifying the temperature of the alloy forming the flow line 620. Increasing the diameter of the flow line 620 may facilitate the removal of viscous oil from the inner walls of the flow line 620. Circulating a fluid may further evacuate any remaining oil film.

[0045] Although many embodiments may be described above in the context of a wireline apparatus, aspects of the present disclosure are also applicable or readily adaptable to while- drilling implementations, such as measurement-while-drilling (MWD) and logging-while- drilling (LWD), among others. More generally, some aspects of the present disclosure may be implemented in conjunction with any mode of conveyance of a downhole tool. Similarly, while many embodiments described above are discussed in the context of a probe tool, other tools may also be implemented with one or more aspects of the present disclosure, such as a dual packer tool. Furthermore, although a sampling tool having a guard line and a sample line has been shown, a conventional sampling tool may also be used (such as the MDT, trademark of Schlumberger).

[0046] Moreover, while the hydraulic cleaning operation has been described as taking place just before a second sampling operation, in some cases, the cleaning operation may be initiated just after a first sampling operation, or elsewhere in a reservoir sampling program. For example, the formation fluid may still be hot just after the first sampling operation, such that the cleaning of the flow line may thereby be facilitated. It should be appreciated that the cleaning processes of the present disclosure may also be used in combination. Similarly, while an open hole sampling tool has been described above, a cased hole sampling tool (e.g., a sampling tool similar to the Cased Hole Dynamics Tester, trademark of Schlumberger) may also be provided with means for cleaning hydraulic components according to one or more aspects of the present disclosure.

[0047] The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present PATENT DKT. NO. 20.3106NP disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the present disclosure.

Claims

PATENT DKT. NO. 20.3106NPWhat is claimed is:

1. A method of cleaning a portion of a hydraulic circuit in a downhole tool, comprising: lowering a tool in a borehole, the tool having a hydraulic circuit for facilitating formation fluid flow; cleaning at least a portion of the hydraulic circuit, wherein cleaning the flow line comprises at least one of purging and flushing the hydraulic circuit portion with a cleaning fluid to remove contaminant from the hydraulic circuit; and flowing fluid from the formation through the cleaned portion of the hydraulic circuit.

2. The method of claim 1 further comprising heating the hydraulic circuit portion to reduce adhesion of the contaminant to a wall of the hydraulic circuit portion.

3. The method of claim 1 further comprising altering the temperature of the hydraulic circuit portion to reduce adhesion of the contaminant to the hydraulic circuit portion.

4. The method of claim 1 wherein the cleaning fluid comprises at least one of a solvent, a bead loaded fluid, fluid with an additive for modifying interfacial tension, and an immiscible fluid having a viscosity that acts as a displacement fluid.

5. The method of claim 1 further comprising scraping a wall of the hydraulic circuit portion with a moveable device.

6. The method of claim 1 further comprising exposing at least one of a wall of the hydraulic circuit portion and fluid in the hydraulic circuit portion to a vibration source.

7. The method of claim 1 further comprising at least one of stretching and shortening a dimension of the hydraulic circuit portion.

8. The method of claim 7 wherein the hydraulic circuit portion comprises a memory shape alloy. PATENT DKT. NO. 20.3106NP

9. An apparatus for cleaning a hydraulic circuit in a downhole tool, comprising: an inlet selectively coupled fluidly to a formation; a hydraulic circuit fluidly coupled to the inlet; means for facilitating formation fluid flow from the inlet; means for introducing cleaning fluid into the hydraulic circuit; and means for cleaning at least a portion of the hydraulic circuit with the cleaning fluid.

10. The apparatus of claim 9 wherein the means for facilitating formation fluid flow includes a pump and at least one flow line fluidly coupled between the inlet and the pump.

11. The apparatus of claim 9 further comprising means for heating at least a portion of the hydraulic circuit.

12. The apparatus of claim 9 further comprising means for altering a temperature of at least a portion of the hydraulic circuit.

13. A method of cleaning a sensing face of a sensor of a hydraulic circuit in a downhole tool, comprising: lowering a tool in a borehole, the tool having a hydraulic circuit for facilitating formation fluid flow; sensing a parameter of at least one of a formation fluid and a wellbore fluid with a sensor; cleaning a sensing face of the sensor disposed in the hydraulic circuit; and flowing fluid from the formation towards the sensor, wherein cleaning the sensing face involves purging or flushing a portion of the hydraulic circuit with a cleaning fluid.

14. The method of claim 13 wherein cleaning the sensing face of the sensor includes applying heat to at least a portion of at least one of the sensor and the hydraulic circuit.

15. The method of claim 13 wherein cleaning the sensing face of the sensor includes altering a temperature of at least a portion of at least one of the sensor and the hydraulic circuit. PATENT DKT. NO. 20.3106NP

16. The method of claim 13 wherein cleaning the sensing face of the sensor includes exposing at least a portion of at least one of the sensor and the hydraulic circuit to a vibration source.