Method and apparatus for liberating gases from drilling fluid

• US 9,651,481 B2
• Filed: 01/17/2014
• Issued: 05/16/2017
• Est. Priority Date: 06/17/2010
• Status: Active Grant

• Current Assignee: Pason Systems USA Corporation
• Original Assignee: Pason Systems USA Corporation
• Inventors: DeGreeve, Jason Alexander, Unrau, Sean William Lyons, van Beurden, Marceau Ernest, van Beurden, Ryan Henricus
• Primary Examiner(s): Rogers, David A
• Application Number:
  US14/157,881
• Publication Number:
  US 20140130671A1
• Time in Patent Office: 1,215 Days
• CPC Class Codes: B01D 19/0042 modifying the liquid flow B01D19/0021 takes precedence
• CPC Class Codes: B01D 19/0052 in rotating vessels, vessels containing movable parts or in which centrifugal movement is caused B01D19/0026 takes precedence
• CPC Class Codes: E21B 21/01 Arrangements for handling drilling fluids or cuttings outside the borehole, e.g. mud boxes
• CPC Class Codes: E21B 21/067 Separating gases from drilling fluids
• CPC Class Codes: E21B 49/00 Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
• CPC Class Codes: E21B 49/005 Testing the nature of borehole walls or the formation by using drilling mud or cutting data
• CPC Class Codes: E21B 49/084 with means for conveying samples through pipe to surface
• CPC Class Codes: E21B 49/0875 determining specific fluid parameters
• CPC Class Codes: G01N 2021/399 Diode laser
• CPC Class Codes: G01N 21/35 using infrared light G01N21/39 takes precedence
• CPC Class Codes: G01N 21/3504 for analysing gases, e.g. multi-gas analysis
• CPC Class Codes: G01N 21/39 using tunable lasers
• CPC Class Codes: G01N 2201/12 Circuits of general importance; Signal processing
• CPC Class Codes: G01V 8/02 Prospecting
• CPC Class Codes: G01V 8/10 Detecting, e.g. by using light barriers by reflection from the object G01S17/00

Abstract

A gas trap includes a sample enclosure, a bubbler enclosure, an agitator, and a brushless, DC motor. The sample enclosure has a liquid inlet, a gas sample outlet, and a sample enclosure wall with a sample enclosure wall portion and a shared wall portion. The bubbler enclosure has a bubbler air inlet, a bubbler air outlet, and a bubbler enclosure wall with a bubbler enclosure wall portion and the shared wall portion. The sample and bubbler enclosures are fluidly coupled through the shared wall portion so that sufficiently pressurized bubbler air entering through the bubbler air inlet maintains the drilling fluid in the sample enclosure at a level determined by the location of the bubbler air outlet when the liquid inlet and the bubbler air outlet are both submerged in the drilling fluid.

Claims

1. An apparatus for liberating gases from drilling fluid, the apparatus comprising:

a sample enclosure having a liquid inlet and a gas sample outlet;

an agitator disposed within the sample enclosure and configured to agitate drilling fluid located within the sample enclosure to liberate gases entrained in the drilling fluid so that the gases can exit through the gas sample outlet;

a brushless, DC motor rotatably coupled to the agitator to power the agitator;

a motor cover covering at least a portion of the brushless, DC motor and an explosion proof seal secured to the motor cover, the explosion proof seal permitting electrical connections to be made to the DC motor;

wherein the agitator comprises a shaft having a mixing portion shaped to facilitate agitation of the drilling fluid, and wherein the brushless DC motor comprises a stator and a rotor directly coupled to the shaft and rotatable relative to the stator in order to rotate the shaft;

further comprising a sealing portion disposed around the shaft and between the DC motor and the sample enclosure, the sealing portion comprising a first sealing element configured to prevent solid particulates from entering the brushless DC motor and a second sealing element configured to prevent liquid from entering the brushless DC motor, wherein the first sealing element is nearer to the sample enclosure than the second sealing element,

further comprising a flame path comprising a gap between the shaft and the sealing portion, the flame path acting to prevent combustible gases outside of the DC motor from igniting in the event that an explosion occurs within the DC motor.

2. An apparatus as claimed in claim 1 further comprising a bubbler enclosure having a bubbler air inlet and a bubbler air outlet, and fluidly coupled to the sample enclosure such that the sample and bubbler enclosures are equally pressurized so that sufficiently pressurized bubbler air entering through the bubbler air inlet maintains the drilling fluid in the sample enclosure at a level determined by the location of the bubbler air outlet when the liquid inlet and the bubbler air outlet are both submerged in the drilling fluid, and such that agitated drilling fluid enters the bubbler enclosure from the sample enclosure.

3. An apparatus as claimed in claim 2 further comprising:

a bubbler air conduit fluidly coupled to the bubbler air inlet to transport the pressurized bubbler air from outside of the apparatus to the bubbler enclosure; and

a heat trace thermally coupled to the bubbler air conduit.

4. An apparatus as claimed in claim 2 further comprising:

a gas sample conduit fluidly coupled to the gas sample outlet to transport the gas sample away from the sample enclosure;

a bubbler air conduit fluidly coupled to the bubbler air inlet to transport the pressurized bubbler air from outside of the apparatus to the bubbler enclosure; and

a heat trace thermally coupled to both the gas sample and bubbler air conduits.

5. An apparatus as claimed in claim 2 further comprising a gas analyzer comprising a bubbler pump fluidly coupled to an air source and configured to output the pressurized bubbler air, wherein the bubbler air inlet is fluidly coupled to the bubbler pump to receive the pressurized bubbler air.

6. An apparatus as claimed in claim 1 wherein the second sealing element comprises two seals.

7. An apparatus as claimed in claim 1 further comprising a disc disposed along the shaft to prevent the drilling fluid from entering the DC motor.

8. An apparatus as claimed in claim 1 further comprising:

a gas sample conduit fluidly coupled to the gas sample outlet to transport the gas sample away from the sample enclosure; and

a heat trace thermally coupled to the gas sample conduit.

9. An apparatus as claimed in claim 1 wherein the shaft is directly coupled to the rotor using an adhesive.

10. An apparatus as claimed in claim 1 wherein the DC motor is frameless.

11. An apparatus as claimed in claim 10 further comprising bearings located above and below the rotor, the bearings contacting the shaft to facilitate rotation of the shaft.

12. A method for liberating gases entrained in a drilling fluid, the method comprising:

submerging a liquid inlet of a sample enclosure in the drilling fluid; and

agitating the drilling fluid within the sample enclosure to liberate the gases entrained therein by using a brushless DC motor,

wherein a motor cover covers at least a portion of the brushless DC motor and an explosion proof seal is secured to the motor cover, the explosion proof seal permitting electrical connections to be made to the brushless DC motor;

wherein the brushless DC motor comprises a stator and a rotor directly coupled to a shaft extending from the brushless DC motor and rotatable relative to the stator in order to rotate the shaft, wherein rotation of the shaft results in the agitation;

sealing the DC motor using a sealing portion disposed around the shaft and between the DC motor and the sample enclosure, the sealing portion comprising a first sealing element configured to prevent solid particulates from entering the DC motor and a second sealing element configured to prevent liquid from entering the DC motor, wherein the first sealing element is nearer to the sample enclosure than the second sealing element,

wherein a flame path comprising a gap is present between the shaft and the sealing portion, the flame path acting to prevent combustible gases outside of the DC motor from igniting in the event that an explosion occurs within the DC motor.

13. A method as claimed in claim 12 further comprising:

submerging a bubbler air outlet of a bubbler enclosure in the drilling fluid, wherein the sample and bubbler enclosures are fluidly coupled together such that they are equally pressurized and such that the drilling fluid agitated in the sample enclosure enters the bubbler enclosure; and

pressurizing the sample and bubbler enclosures using pressurized bubbler air such that the drilling fluid in the sample enclosure is at a level determined by the location of the bubbler air outlet.

14. A method as claimed in claim 13 further comprising conveying the bubbler air to the bubbler enclosure using a heated bubbler air conduit.

15. A method as claimed in claim 13 further comprising conveying the gases liberated from the drilling fluid away from the sample enclosure using a gas sample conduit and conveying the bubbler air to the bubbler enclosure using a bubbler air conduit, and wherein the gas sample and bubbler air conduits are both heated.

16. A method as claimed in claim 13 further comprising generating the bubbler air by using a pump located within a gas analyzer.

17. A method as claimed in claim 12 further comprising blocking splashing drilling fluid from entering the DC motor with a disc disposed along the shaft.

18. A method as claimed in claim 12 further comprising conveying the gases liberated from the drilling fluid away from the sample enclosure using a heated gas sample conduit.

19. A method as claimed in claim 12 wherein the shaft is directly coupled to the rotor using an adhesive.

20. A method as claimed in claim 12 wherein the DC motor is frameless.

21. A method as claimed in 20 wherein bearings are located above and below the rotor, the bearings contacting the shaft to facilitate rotation of the shaft.