1. A method of removing oxygen from a drilling fluid, the method comprising: pumping the drilling fluid into a first inlet of a mixer, the drilling fluid flowing into the mixer from the first inlet in a first direction; pumping a gas including nitrogen into a second inlet of the mixer to mix the gas with the drilling fluid, the gas flowing into the mixer from the second inlet in a second direction substantially opposite from the first direction, thereby permitting mass transfer of the oxygen from the drilling fluid to the gas to produce a deoxygenated drilling fluid; and discharging the deoxygenated drilling fluid from an outlet of the mixer.

2. The method of claim 1, further comprising collecting the deoxygenated drilling fluid discharged from the outlet of the mixer in a container.

3. The method of claim 1 or 2, wherein the mixer includes a portion with structured packing configured to increase a surface area of the drilling fluid.

4. The method of claim 3, wherein the portion with structured packing has a length of at least about two meters.

5. The method of claim 3, wherein the portion with structured packing has a length of at least about five meters.

6. The method of any one of claims 1-5, wherein the mixer is a column.

7. The method of any one of claims 1-6, wherein pumping the drilling fluid includes using a centrifugal pump.

8. The method of any one of claims 1-7, further comprising regulating a flow rate of the drilling fluid before the drilling fluid enters the first inlet.

AMENDED SHEET (ARTICLE 19) 9. The method of claim 8, wherein the flow rate of the drilling fluid is about 40 m³/h to about 3.400 m³/h.

10. The method of any one of claims 1-9, further comprising regulating a pressure of the gas before the gas enters the second inlet.

11. The method of any one of claims 1-10, further comprising regulating a flow rate of the gas before the gas enters the second inlet.

12. The method of claim 11, wherein the flow rate of the gas is about 50 Nm³/h to about 500 Nm³/h.

13. The method of any one of claims 1-12, further comprising heating the gas to be greater than about 20 °C, thereby improving mass transfer efficiency.

14. The method of any one of claims 1-13, further comprising measuring an oxygen level in the drilling fluid or the deoxygenated drilling fluid.

15. The method of claim 14, wherein measuring the oxygen level includes using an optical sensor.

16. The method of any one of claims 1-15, wherein the drilling fluid is drilling mud.

17. The method of any one of claims 1-16, wherein the gas includes at least 99% nitrogen by volume.

18. The method of any one of claims 1-17, wherein the method removes at least about 90% oxygen from the drilling fluid.

19. The method of any one of claims 1-18, wherein the method removes at least about 95% oxygen from the drilling fluid.

AMENDED SHEET (ARTICLE 19) 20. The method of any one of claims 1-19, wherein the deoxygenated drilling fluid includes less than about 20 parts per billion (ppb) oxygen.

21. A method of decreasing corrosion on a drilling equipment, the method comprising: pumping a drilling fluid into a first inlet of a mixer, the drilling fluid flowing into the mixer from the first inlet in a first direction; pumping a gas including nitrogen into a second inlet of the mixer to mix the gas with the drilling fluid, the gas flowing into the mixer from the second inlet in a second direction substantially opposite from the first direction, thereby permitting mass transfer of the oxygen from the drilling fluid to the gas to produce a deoxygenated drilling fluid; discharging the deoxygenated drilling fluid from an outlet of the mixer; and contacting the deoxygenated drilling fluid with the drilling equipment during drilling operation.

22. The method of claim 21, wherein the drilling equipment is a drill string, a riser, or a blowout preventer.

23. A method of decreasing corrosion on a drilling equipment, the method comprising contacting a deoxygenated drilling fluid with the drilling equipment during drilling operation, wherein the deoxygenated drilling fluid is produced by: pumping a drilling fluid into a first inlet of a mixer, the drilling fluid flowing in a first direction; and pumping a gas including nitrogen into a second inlet of the mixer to mix the gas with the drilling fluid, the second inlet being downstream of the drilling fluid, the gas flowing in an opposite direction from the first direction, thereby permitting mass transfer of the oxygen from the drilling fluid to the gas to produce the deoxygenated drilling fluid.

24. The method of claim 23, wherein the drilling equipment is a drill string, a riser, or a blowout preventer.

AMENDED SHEET (ARTICLE 19) 25. The method of any one of the preceding claims, wherein: the drilling fluid is pumped at a first volume flow rate; the gas is pumped at a second volume flow rate; and the ratio of the second to the first volume flow rate is at least one.

26. The method of claim 25, wherein the ratio of the second to the first volume flow rate is greater than two.

27. The method of any one of claims 1-24, wherein: the drilling fluid is pumped at a first volume flow rate; the gas is pumped at a second volume flow rate; and the ratio of the second to the first volume flow rate is selected such that the deoxygenated drilling fluid has an oxygen level below a target threshold.

AMENDED SHEET (ARTICLE 19)