System and method for predicting compatibility of fluids with metals

• US 7,519,481 B2
• Filed: 09/11/2006
• Issued: 04/14/2009
• Est. Priority Date: 09/11/2006
• Status: Active Grant

• Current Assignee: Tetra Technologies Incorporated
• Original Assignee: Tetra Technologies Incorporated
• Inventors: Mishra, Surendra K., Carter, Thomas S., Perrin, Glenn, McKennis, Jeffrey
• Primary Examiner(s): Barbee; Manuel L
• Application Number:
  US11/518,757
• Publication Number:
  US 20080126383A1
• Time in Patent Office: 946 Days
• Field of Search: None
• US Class Current: 702/42
• CPC Class Codes: E21B 41/02 in situ inhibition of corrosion in boreholes or wells

Abstract

A method and system for selecting fluids for compatibility with specified metals exposed to oil field environments. Metal specimens are tested for corrosion and/or cracking behavior by exposing them to fluids under stressful test conditions. The testing is conducted under variable temperature, pressure, pH, fluid density, metallurgical stress, additives, cover gases and combinations thereof. The results from the stress testing are stored in a database. The test results are evaluated using encoded logic embedded in software media. Fluid compatibility evaluation software, developed from the stress test results, is executed to determine the cracking susceptibility of metals exposed to fluids under stressful conditions. A cracking susceptibility index can be developed to provide a quantitative indicator of cracking susceptibility. Fluid recommendation reports utilize the cracking susceptibility index values to rank compatible fluids. The reports also list optional additives to be used with the fluids.

Claims

1. An accelerated method for selecting one or more compatible fluids for one or more metals exposed to the corrosive conditions present in an oil field environment, the method comprising:

contacting one or more metal specimens comprising the one or more metals with one or more test fluids under stress testing conditions simulating downhole conditions and conducted over an accelerated period of time compared to NACE standard test guidelines, the stress testing conditions comprising a stress level effective to produce both elastic and plastic deformation of the one or more metal specimens, the one or more test fluids being representative of packer fluids or completion fluids commercially used under the corrosive conditions in the oil field environment;

monitoring in real time one or more corrosion tendencies of the one or more metal specimens and producing simulated stress test data comprising pre-cracking parameters and/or cracking parameters for the one or more metal specimens; and

,

selecting fluids by matching the simulated stress test data with actual field conditions under which a completion fluid or frac fluid is compatible with one or more metals in an oil field environment.

2. The method of claim 1 wherein the accelerated period of time is 7 days or less.

3. The method of claim 1 further comprising obtaining the one or more test fluids from companies that manufacture the test fluids for use in the oil field environment wherein the test fluids comprise completion fluids and/or packer fluids.

4. The method of claim 3 further comprising using one or more test fluids having a density of from 8.3 lb/gal and 20.5 lb/gal.

5. The method of claim 1 further comprising evaluating the one or more stress test records to assign to the one or more test fluids a value along one or more indexes, the indexes comprising a range of arbitrary values representing corrosion and pre-cracking events, the one or more indexes each further comprising an arbitrary cutoff value for selecting the one or more compatible test fluids.

6. The method of claim 5 wherein:

the index is from 1 to 100; and

,

the arbitrary cutoff value is 25.

7. The method of claim 5 further comprising using one or more arbitrary cutoff values to select the one or more compatible fluids.

8. The method of claim 7 further comprising evaluating the one or more stress test records using fluid compatibility evaluation software to assign the one or more test fluids a value along the one or more indexes.

9. The method of claim 5 further comprising using the one or more stress test records to select one or more compatible fluids from among the one or more test fluids, the one or more compatible fluids being effective to minimize the risk of stress corrosion cracking along the outside of metal tubing comprising the one or more metals when exposed to the corrosive conditions present in an oil field environment.

10. The method of claim 9 wherein the stress testing conditions comprise one or more contaminants.

11. The method of claim 10 wherein the one or more contaminants comprise air, hydrogen sulphide, and/or carbon dioxide.

12. The method of claim 5 further comprising mimicking worst case downhole conditions by providing partial pressures of gases designed to mimic flow of production gases freely into the annulus of oil field tubing.

13. The method of claim 5 further comprising generating a fluid recommendation report ranking compatibility of the one or more test fluids with the one or more metals based on the one or more arbitrary cutoff values.

14. The method of claim 13 further comprising providing in the fluid recommendation report a list of one or more optional additives recommended for use with the one or more metals.

15. The method of claim 1 further comprising recommending one or more optional additives for use with the one or more fluids to be used with one or more metals.

16. The method of claim 1 further comprising:

generating a fluid recommendation report based on the one or more stress test records; and

,

using the fluid recommendation report to select the one or more compatible fluids.

17. The method of claim 16 further comprising providing in the fluid recommendation report a list of one or more optional additives recommended for use with the one or more metals.

18. The method of claim 1 further comprising evaluating the one or more stress test records using fluid compatibility evaluation software to select the one or more compatible fluids.

19. An accelerated method for selecting one or more compatible fluids for one or more metals exposed to the corrosive conditions present in an oil field environment, the method comprising:

contacting one or more metal specimens comprising the one or more metals with one or more test fluids under stress testing conditions simulating downhole conditions, the stress testing conditions comprising a stress level effective to produce both elastic and plastic deformation of the one or more metal specimens, wherein the one or more test fluids are representative of fluids commercially used in the oil field environment;

electrochemically monitoring in real time one or more corrosion tendencies of the one or more metal specimens, producing simulated stress test data for the one or more metal specimens, the simulated stress test data comprising cracking data and normalized pre-cracking data, the normalized precracking data comprising localized corrosion data, severe localized corrosion data, and/or pitting data;

evaluating the simulated stress test data to assign to the one or more test fluids one or more values along one or more indexes comprising a range of arbitrary values representing a quantitative relative susceptibility towards one or more phenomena of cracking susceptibility, cracking resistance, and/or corrosion susceptibility, thereby ranking compatibility of the one or more test fluids with the one or more metal specimens under the downhole conditions, the one or more indexes each comprising an arbitrary cutoff value for selecting the one or more compatible fluids; and

,

selecting fluids by matching the simulated stress test data with actual field conditions under which a completion fluid or frac fluid is compatible with one or more metals in an oil field environment,

selecting the one or more compatible fluids based on one or more of the arbitrary cutoff values, the one or more compatible fluids being effective to minimize the risk of stress corrosion cracking along the outside of metal tubing comprising the one or more metals when exposed to the corrosive conditions present in an oil field environment.

20. The method of claim 19 further comprising evaluating one or more well parameters and/or one or more fluid parameters to select the one or more compatible fluids.

21. The method of claim 20 further comprising using fluid compatibility evaluation software to evaluate the one or more stress test records.

22. The method of claim 21 further comprising generating a fluid recommendation report indicating the one or more compatible fluids.

23. The method of claim 22 wherein the fluid recommendation report recommends a list of one or more optional additives for use with the one or more metals.

24. The method of claim 23 further comprising using one or more test fluids having a density of from 8.3 lb/gal and 20.5 lb/gal.

25. The method of claim 24 wherein:

the one or more indexes are from 1 to 100; and

,

the cutoff value is 25.

26. A system for selecting fluids by matching the simulated test stress data with actual field conditions for use as a completion fluid or a frac fluid that is compatible with metals for downhole use, the system comprising:

an apparatus adapted to stress test one or more metal specimens, the apparatus comprising the one or more metals in contact with one or more test fluids, the apparatus being adapted to conduct stress testing over an accelerated period of time compared to NACE standard test guidelines, the apparatus being further adapted to apply a stress level effective to produce both elastic and plastic deformation of the one or more metal specimens;

a real-time automated electrochemical monitoring apparatus in electrochemical communication with the one or more metal specimens, the electrochemical monitoring apparatus being adapted to produce one or more stress test records for the one or more metal specimens;

a database adapted to store the one or more stress test records;

one or more media comprising encoded logic for evaluating the stress test records; and

,

one or more apparatus adapted to execute the encoded logic to use the one or more stress test records to rank compatibility of the one or more test fluids with the one or more metals under the downhole conditions.

27. The system of claim 26 wherein the one or more media comprises fluid compatibility evaluation software.

28. The system of claim 27 wherein the one or more media further comprises additive selection software.

29. The system of claim 28 wherein the apparatus is adapted to provide one or more contaminants during the stress testing.

30. The system of claim 29 further comprising one or more user interface screens adapted to display one or more fluid compatibility rankings and to receive one or more customer specified input values.

31. The system of claim 30 wherein the one or more customer specified input values comprise one or more well parameters and one or more fluid parameters comprising fluid density and/or one or more additives.

32. The system of claim 31 wherein the one or more well parameters comprise bottom hole temperature, hydrogen sulphide concentration, carbon dioxide concentration, and/or metallurgical grades of metals.

33. The system of claim 32 further comprising report generation software adapted to generate one or more fluid recommendation reports ranking compatibility of the one or more test fluids with the one or more metals under the downhole conditions.