Sensors for in-situ formation fluid analysis
A downhole tool including a tube having an inner bore that receives a sample of fluid from a subterranean formation, a vibration source and a vibration receiver each at least partially coupled to the tube, and a controller coupled to the vibration source and the vibration receiver is provided. In situ measurements of thermo-physical properties including, but not limited to, fluid density/viscosity, thermal conductivity and heat capacity, and hydrocarbon molecular weight may be provided through the system. The vibrating sensor may include a sensor platform that can be incorporated into sensors purpose built to test different in situ thermo-physical properties that are technically difficult or expensive to test using typical sensors. The vibrating sensors may be modularized and incorporated as a suite of in situ downhole sensors into existing downhole fluid sampling tools, reducing the overall expense of in situ testing.
1. A downhole tool, comprising:
a tube comprising an inner bore that receives a gas phase of a sample of fluid from a subterranean formation;
a vibration source at least partially coupled to the tube;
a vibration receiver at least partially coupled to the tube;
a controller coupled to the vibration source and the vibration receiver;
a second tube comprising an inner bore that receives a liquid phase of the sample of fluid from the subterranean formation; and
a liquid-gas separator in fluid communication with the inner bore of the tube and the inner bore of the second tube.
2. The downhole tool of claim 1 , further comprising a housing in which the tube is at least partially positioned.
3. The downhole tool of claim 2 , wherein
the vibration source comprises a source magnet coupled to the tube and a source coil coupled to the housing and axially aligned with the source magnet; and
the source coil is coupled to the controller.
4. The downhole tool of claim 3 , wherein
the vibration receiver comprises a receiver magnet coupled to the tube and a receiver coil coupled to the housing and axially aligned with the receiver magnet; and
the receiver coil is coupled to the controller.
5. The downhole tool of claim 1 , wherein
the vibration source, in response to a signal from the controller, induces a vibration in the tube; and
the vibration receiver measures the lateral displacement of the tube over time during the induced vibration of the tube.
6. The downhole tool of claim 5 , wherein the controller receives the lateral displacement measurements from the vibration receiver and determines a resonant frequency of the vibration.
7. The downhole tool of claim 5 , further comprising a temperature sensor in fluid communication with the inner bore of the tube and communicably coupled to the controller.
8. The downhole tool of claim 5 , further comprising a heating element coupled to a fluid conduit in fluid communication with the inner bore of the tube.
9. A method, comprising:
obtaining a fluid sample from a subterranean formation with a downhole tool positioned within a borehole in the subterranean formation;
introducing the fluid sample into the inner bore of a tube within the downhole tool;
inducing a vibration in the tube;
measuring the induced vibration in the tube;
determining a resonant frequency of the vibration; and
determining a thermo-physical property of the fluid sample based, at least in part, on the determined resonant frequency, wherein the thermo-physical property of the fluid sample comprises at least one of density, viscosity, thermal conductivity, heat capacity, or hydrocarbon molecular weight, wherein determining the thermo-physical property of the fluid sample comprises determining the hydrocarbon molecular weight by:
separating the fluid sample into a gas phase and a liquid phase; and
determining a resonant frequency corresponding to the gas phase and a resonant frequency corresponding to the liquid phase.
10. The method of claim 9 , wherein the downhole tool comprises one of a wireline logging tool and a logging-while-drilling tool.
11. The method of claim 9 , wherein determining the resonant frequency of the vibration comprises determining a frequency-domain representation of the induced vibration measurement.
12. The method of claim 11 , wherein determining the viscosity of the fluid sample comprises determining a width of a peak in the frequency-domain representation corresponding to the determined resonant frequency.
13. The method of claim 11 , wherein determining the thermal conductivity and heat capacity of the fluid sample comprises heating the fluid sample and determining a resonant frequency shift.
14. A downhole tool, comprising
a fluid pump-out system to obtain a sample of fluid from a subterranean formation;
a sensor in fluid communication with the pump-out system to determine density and viscosity of the fluid sample;
a sensor in fluid communication with the pump-out system to determine thermal conductivity and heat capacity of the fluid sample; and
a sensor in fluid communication with the pump-out system to determine hydrocarbon molecular weight of the fluid sample;
wherein at least one of the density and viscosity sensor, the thermal conductivity and heat capacity sensor, and the hydrocarbon molecular weight sensor comprises
a tube comprising an inner bore that receives a sample of fluid from a subterranean formation;
a vibration source at least partially coupled to the tube;
a vibration receiver at least partially coupled to the tube; and
a controller coupled to the vibration source and the vibration receiver.
15. The downhole tool of claim 14 , wherein the downhole tool comprises one of a wireline logging tool and a logging-while-drilling tool.
16. The downhole tool of claim 15 , wherein the downhole tool further comprises at least one of an optical sensor tool and an ultrasonic sensor tool.
17. The downhole tool of claim 14 , wherein
the vibration source, in response to a signal from the controller, induces a vibration in the tube; and
the vibration receiver measures the lateral displacement of the tube over time during the induced vibration of the tube.
18. The downhole tool of claim 1 , further comprising:
a second vibration source at least partially coupled to the second tube; and
a second vibration receiver at least partially coupled to the tube.
19. The downhole tool of claim 14 , wherein the hydrocarbon molecular weight sensor comprises
a first tube comprising an inner bore that receives a gas phase of the sample of fluid from the subterranean formation;
a vibration source at least partially coupled to the first tube;
a vibration receiver at least partially coupled to the first tube;
a second tube comprising an inner bore that receives a liquid phase of the sample of fluid from the subterranean formation; and
a liquid-gas separator in fluid communication with the inner bore of the first tube and the inner bore of the second tube.
20. The downhole tool of claim 19 , wherein the hydrocarbon molecular weight sensor further comprises:
a second vibration source at least partially coupled to the second tube; and
a second vibration receiver at least partially coupled to the second tube.