Formation testing

• US 8,763,696 B2
• Filed: 01/04/2011
• Issued: 07/01/2014
• Est. Priority Date: 04/27/2010
• Status: Active Grant

• Current Assignee: Asa Equinor, Schlumberger Technology Corporation (SLB)
• Original Assignee: Schlumberger Technology Corporation (SLB)
• Inventors: Bedouet, Sylvain, Eriksen, Karre Otto
• Primary Examiner(s): ANDREWS, DAVID L
• Application Number:
  US12/983,956
• Publication Number:
  US 20110259581A1
• Time in Patent Office: 1,274 Days
• Field of Search: 175/59, 175/60, 175/206, 175/207, 175/264, 166/264
• US Class Current: 166/264
• 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 49/088 combined with sampling
• CPC Class Codes: E21B 49/10 using side-wall fluid samplers or testers

Abstract

Formation testing which may involve circulating mud in a pipe string from a mud pit through a port in the pipe string to a downhole diverter sub, wherein the pipe string is suspended in a wellbore extending into a subterranean formation, operating a downhole pump to pump formation fluid from the formation, wherein the formation fluid comprises gas, and mixing the pumped formation fluid with circulated mud such that a proportion of the pumped formation gas in the circulated mud is maintained below a threshold value.

Claims

1. A method, comprising:

initiating circulation of a mud in a pipe string from a mud pit through a surface port in the pipe string to a downhole diverter sub, wherein the pipe string is suspended in a wellbore extending into a subterranean formation;

operating a downhole pump to pump formation fluid from the subterranean formation, wherein the formation fluid contains at least one of a free gas or a dissolved gas;

mixing the formation fluid that has been pumped with the mud that has been circulated to form a mixture of formation fluid and mud such that a proportion of the at least one of the free gas or the dissolved gas in the mixture is maintained below a threshold value determined at least in part based on a gas content of the formation fluid;

performing a thermo-hydraulic simulation to predict a response of the mixture to conditions of the subterranean formation, wherein the response comprises fluid pressures of the mixture; and

adjusting the threshold value in response to determining that the fluid pressures of the mixture indicate a wellbore integrity condition.

2. The method of claim 1, further comprising:

directing the mixture of formation fluid and mud to a multiphase flow meter.

3. The method of claim 1, further comprising:

directing the mixture of formation fluid and mud through a choke manifold via at least one of a choke line and a kill line.

4. The method of claim 1, further comprising:

directing the mixture of formation fluid and mud to a surface separator configured to separate a gas portion from a liquid portion of the mixture.

5. The method of claim 1, further comprising:

measuring at least one of a phase boundary, a density and a viscosity of the formation fluid pumped from the formation.

6. The method of claim 1, further comprising:

reducing mud circulation.

7. The method of claim 6, further comprising:

monitoring build-up pressure data after reducing mud circulation.

8. The method of claim 1, comprising determining a ratio, of a pumping rate of the formation fluid to a circulation rate of the mud, as the threshold value.

9. An apparatus, comprising:

a downhole diverter sub;

a pipe string configured to be suspended in a wellbore extending into a subterranean formation, wherein the pipe string comprises a surface port configured to circulate a mud to the downhole diverter sub;

a downhole pump configured to pump formation fluid from the formation, wherein the formation fluid comprises at least one of a free gas or a dissolved gas;

a mixer configured to mix the formation fluid that has been pumped with the mud that is circulating to form a mixture of the formation fluid and the mud; and

a controller configured to;

maintain a proportion of at least one of the free gas or the dissolved gas in the mixture below a threshold value determined at least in part based on a gas content of the formation fluid;

perform a thermo-hydraulic simulation to predict a response of the mixture to conditions of the subterranean formation, wherein the response comprises fluid pressures of the mixture; and

adjust the threshold value in response to determining that the fluid pressures of the mixture indicate a wellbore integrity condition.

10. The apparatus of claim 9, wherein the mixer comprises:

a first fluid communicator configured to allow fluid communication with an annulus of the wellbore; and

a second fluid communicator configured to direct the formation fluid that has been pumped to the annulus, wherein the second fluid communicator is not disposed deeper in the wellbore than the first fluid communicator.

11. The apparatus of claim 9, comprising a formation testing device disposed deeper in the wellbore relative to the downhole diverter sub, wherein the formation testing device comprises:

first and second inflatable packers each configured to engage the wellbore proximate the subterranean formation; and

a third fluid communicator positioned between the first and second packers.

12. The apparatus of claim 11, wherein the formation testing device further comprises third and fourth inflatable packers each configured to engage the wellbore, wherein the first and second packers are positioned between the third and fourth packers.

13. The apparatus of claim 9, further comprising:

a sensor configured to sense composition data of the formation fluid pumped from the formation.

14. The apparatus of claim 9, further comprising:

a sensor configured to sense a gas-to-oil ratio of the formation fluid pumped from the formation.

15. The apparatus of claim 9, further comprising:

at least one sample chamber configured to retain a sample of the formation fluid pumped from the formation.

16. The apparatus of claim 9, wherein the downhole pump is configured to receive electrical power from at least one of a mud driven turbine housed in a downhole tool, a segmented conductive wire operatively coupled to the pipe string and an electrical cable extending within the wellbore.

17. The apparatus of claim 9, wherein the controller is configured to determine a ratio, of a pumping rate of the formation fluid to a circulation rate of the mud, as the threshold value.

18. A method, comprising:

initiating circulation of a mud in a pipe string from a mud pit through a surface port in the pipe string to a downhole diverter sub, wherein the pipe string is suspended in a wellbore extending into a subterranean formation;

operating a downhole pump to pump formation fluid from the subterranean formation, wherein the formation fluid contains at least one of a free gas or a dissolved gas;

determining a ratio, of a pumping rate of the formation fluid to a circulation rate of the mud, as a threshold value; and

mixing the formation fluid that has been pumped with the mud that has been circulated to form a mixture of formation fluid and mud such that a proportion of the at least one of the free gas or the dissolved gas in the mixture is maintained below the threshold value, wherein the ratio representing the threshold value is determined at least in part based on a gas content of the formation fluid.

19. An apparatus, comprising:

a downhole diverter sub;

a pipe string configured to be suspended in a wellbore extending into a subterranean formation, wherein the pipe string comprises a surface port configured to circulate a mud to the downhole diverter sub;

a downhole pump configured to pump formation fluid from the formation, wherein the formation fluid comprises at least one of a free gas or a dissolved gas;

a mixer configured to mix the formation fluid that has been pumped with the mud that is circulating to form a mixture of the formation fluid and the mud; and

a controller configured to;

determine a ratio, of a pumping rate of the formation fluid to a circulation rate of the mud, as a threshold value; and

maintain a proportion of at least one of the free gas or the dissolved gas in the mixture below the threshold value, wherein the ratio representing the threshold value is determined at least in part based on a gas content of the formation fluid.