Method for determining the content of at least one given gas in a drilling mud, associated device and rig

• US 20060224333A1
• Filed: 04/03/2006
• Published: 10/05/2006
• Est. Priority Date: 04/04/2005
• Status: Active Grant

• Current Assignee: Geoservices Equipements (Schlumberger NV)
• Original Assignee: Geoservices Equipements (Schlumberger NV)
• Inventors: Breviere, Jerome, Frechin, Nicolas
• Granted Patent: US 7,392,138 B2
• Time in Patent Office: Days
• US Class Current: 702/24
• 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: G01N 33/2823 Raw oil, drilling fluid or polyphasic mixtures

Abstract

The method includes the phases of measuring the quantity (q₁, q₂) of given gas in the gases extracted from a calibration sample of a calibration mud, in at least two stages for extraction under predetermined conditions; and establishing a family (310) of curves (303, 305, 309) representing the extraction, under the predetermined conditions, of the given gas from the drilling mud, on the basis of the measurements carried out. It also includes the phases of measuring the quantity (q_d1) of given gas in the gases extracted from an analysis sample of the drilling mud in an extraction stage, under the predetermined conditions; and computing the given gas content of the drilling mud on the basis of the measured quantity (q_d1) of given gas and of a curve (309) of said family (310).

Claims

1. Method for determining the content of at least one given gas in a drilling mud, and comprising a calibration step including the phases of:

(i) measuring an item of data representing the quantity of given gas in the gases extracted from a calibration sample of a calibration mud, in at least two stages for the extraction, under predetermined conditions, of the calibration sample gases; and

(ii) establishing a family of curves representing the extraction, under the predetermined conditions, of the given gas contained in the drilling mud, on the basis of the measurements carried out during the stages for the extraction of the calibration sample gases; and

at least one analysis step including the phases of;

(a) measuring an item of data representing the quantity of given gas in the gases extracted from an analysis sample of the drilling mud in a stage for the extraction, under the predetermined conditions, of the analysis sample gases; and

(b) computing the given gas content of the drilling mud, on the basis of the quantity of given gas measured in step (a) and of a curve of said family.

2. Method according to claim 1, wherein during step (i), each extraction stage includes the steps of introducing, at a given temperature, the calibration sample into a first gas extraction vessel provided with stirring means;

sampling the gases extracted from the vessel; and

during step (a), the extraction stage includes the steps of introducing, substantially at the given temperature, the analysis sample into a second vessel similar to the first vessel; and

sampling the gases extracted in the second vessel.

3. Method according to claim 2, wherein during step (i), each extraction stage includes a step for recovering the calibration sample after the step of sampling the extracted gases.

4. Method according to claim 1, wherein during step (i), the number of extraction stages is between 2 and 6.

5. Method according claim 1, wherein said family of curves comprises at least one exponential function.

6. Method according to claim 5, wherein the family of curves comprises sequences having the general formula:

q_n=q₁ exp[−

b(n−

1)] 

 

(1)

wherein n is the nth extraction stage of the extraction phase;

(q_n) is the quantity of given gas in the gases extracted during the nth extraction stage;

(q₁) is the quantity of given gas in the gases extracted during the first extraction stage; and

(b) is a parameter that is independent of the given gas content of the calibration mud and that is dependent on the characteristics of the mud and the predetermined conditions.

7. Method according to claim 1, wherein phase (b) includes the steps of identifying the curve of said family on which is located a point corresponding to the quantity of given gas measured in step (a) and in the stage for the extraction of the analysis sample;

and adding this quantity of given gas measured in step (a) to at least one quantity of given gas corresponding to a different point on said curve.

8. Method according to claim 1, wherein the drilling mud is an oil-based mud or a mud based on at least one synthetic compound.

9. Method according to claim 1, wherein the calibration mud comprises at least one portion of the drilling mud.

10. Device for determining the content of at least one given gas in a drilling mud, of the type comprising calibration means comprising first means for the extraction, under predetermined conditions, of the gas contained in a calibration sample of a calibration mud;

first means for measuring an item of data representing the quantity of at least one given gas in the gases extracted from the calibration sample, in at least two stages for extraction, under the predetermined conditions, in the first extraction means;

means for establishing a family of curves representing the extraction, under the predetermined conditions, of the given gas contained in the drilling mud, on the basis of the measurements carried out by the first measuring means;

analysis means comprising second means for the extraction, under the predetermined conditions, of the gas contained in an analysis sample of the drilling mud;

second means for measuring an item of data representing the quantity of given gas in the gases extracted from the analysis sample, in a stage for extraction, under the predetermined conditions, in the second extraction means; and

means for computing the given gas content of the drilling mud, on the basis of the quantity of given gas measured by the second measuring means and of a curve of said family.

11. Device according to claim 10, wherein the first and second extraction means each comprise at least one vessel provided with stirring means, the or each vessel comprising means for conveying mud into the vessel;

means for evacuating mud outside the vessel; and

means for sampling the gas extracted from the vessel;

said vessels having similar structures.

12. Device according to claim 11, wherein the first extraction means comprise a single vessel and means for recovering mud at the outlet of the evacuation means, which means may be connected to an inlet of the vessel.

13. Device according to claim 12, wherein the first extraction means consist of the second extraction means.

14. Device according to claim 11, wherein the first extraction means comprise at least two vessels having similar structures, the means for evacuating mud from the first vessel being connected to the means for conveying mud to the second vessel.

15. Drilling rig of the type comprising a conduit for the circulation of a drilling mud, and further comprising a device according to claim 10;

and said rig further including means for sampling mud from the circulation conduit.

16. Drilling rig according to claim 15, wherein the first and second extraction means each comprise at least one vessel provided with stirring means, the or each vessel comprising means for conveying mud into the vessel;

means for evacuating mud outside the vessel; and

means for sampling the gas extracted from the vessel;

said vessels having similar structures.

17. Drilling rig according to claim 16, wherein the first extraction means comprise a single vessel and means for recovering mud at the outlet of the evacuation means, which means may be connected to an inlet of the vessel.

18. Drilling rig according to claim 17, wherein the first extraction means consist of the second extraction means.

19. Drilling rig according to claim 15, wherein the first extraction means comprise at least two vessels having similar structures, the means for evacuating mud from the first vessel being connected to the means for conveying mud to the second vessel.