Flow regime determination and flow measurement in multiphase flow pipelines

• US 5,708,211 A
• Filed: 01/17/1997
• Issued: 01/13/1998
• Est. Priority Date: 05/28/1996
• Status: Expired due to Fees

• Current Assignee: Ohio University
• Original Assignee: Ohio University
• Inventors: Wilkens, Robert Joseph, Jepson, William Paul, Maley, Jeffrey Joseph
• Primary Examiner(s): Chilcot, Richard
• Assistant Examiner(s): Noori, Max H.
• Application Number:
  US08/785,478
• Time in Patent Office: 361 Days
• Field of Search: 73/861.04, 73/861.42, 73/861.43, 73/861.44, 73/861.45
• US Class Current: 73/861.04
• CPC Class Codes: F17D 1/005 for a two-phase gas-liquid flow
• CPC Class Codes: G01F 1/36 the pressure or differential pressure being created by the use of flow constriction
• CPC Class Codes: G01F 1/708 Measuring the time taken to traverse a fixed distance
• CPC Class Codes: G01F 1/74 Devices for measuring flow of a fluid or flow of a fluent solid material in suspension in another fluid

Abstract

A predetermined multiphase flow anomaly, for example, a plug, a slug, or a pseudo-slug, in a pipeline may be identified by identifying an analysis pipe section containing a multiphase fluid flow, measuring a first differential pressure at a first pair of pressure measuring points positioned along the analysis pipe section, measuring a second differential pressure at a second pair of pressure measuring points positioned along the analysis pipe section, identifying a primary drop in the first differential pressure and a secondary drop in the second differential pressure, measuring a time delay between initiation of the primary pressure drop and initiation of the secondary pressure drop, and determining as a function of the time delay whether the primary pressure drop corresponds to a predetermined multiphase flow anomaly moving through the pipe analysis section.

Claims

1. A method of identifying a predetermined multiphase flow anomaly in a pipe comprising the steps of:

identifying an analysis pipe section, said analysis pipe section containing a multiphase fluid flow;

measuring a first differential pressure at a first pair of pressure measuring points positioned along said analysis pipe section, said first pair of pressure measuring points including a primary upstream measuring point and a primary downstream measuring point separated by a primary pipe distance;

measuring a second differential pressure at a second pair of pressure measuring points positioned along said analysis pipe section, said second pair of pressure measuring points including a secondary upstream measuring point and a secondary downstream measuring point separated by a secondary pipe distance;

identifying a primary drop in said first differential pressure;

identifying a secondary drop in said second differential pressure;

measuring a time delay between initiation of said primary pressure drop and initiation of said secondary pressure drop; and

determining as a function of said time delay whether said primary pressure drop corresponds to said predetermined multiphase flow anomaly moving through the pipe analysis section.

2. A method of analyzing a fluid flow as claimed in claim 1, wherein said step of identifying a primary drop in said first differential pressure comprises plotting a primary differential pressure trace as a function of time and locating said primary pressure drop along said primary differential pressure trace.

3. A method of analyzing a fluid flow as claimed in claim 2 wherein said primary pressure drop is characterized by a pressure drop of at least approximately 1500 Pa.

4. A method of analyzing a fluid flow as claimed in claim 1, wherein said step of identifying a secondary drop in said second differential pressure comprises plotting a secondary differential pressure trace as a function of time and locating said secondary pressure drop along said secondary differential pressure trace.

5. A method of analyzing a fluid flow as claimed in claim 4 wherein said secondary pressure drop is characterized by a pressure drop of at least approximately 150 Pa.

6. A method of analyzing a fluid flow as claimed in claim 1 wherein said step of measuring a time delay comprises (i) plotting a primary differential pressure trace as a function of time and locating said primary pressure drop along said primary differential pressure trace, (ii) superimposing a secondary differential pressure trace on said primary differential pressure trace and locating said secondary pressure drop along said secondary differential pressure trace, and (iii) measuring a time delay distance between said primary pressure drop and said secondary pressure drop.

7. A method of analyzing a fluid flow as claimed in claim 1 wherein said step of determining whether said primary pressure drop corresponds to said predetermined flow anomaly comprises comparing said time delay with a characteristic anomaly time delay.

8. A method of analyzing a fluid flow as claimed in claim 7 wherein said characteristic anomaly time delay corresponds to a propagational velocity of said predetermined anomaly in said pipe.

9. A method of analyzing a fluid flow as claimed in claim 8 wherein said predetermined anomaly is a slug and said propagational velocity is approximately 1.2 times a mixture velocity of said fluid.

10. A method of analyzing a fluid flow as claimed in claim 8 wherein said predetermined anomaly is a pseudo-slug and said propagational velocity is approximately 1.1 times a mixture velocity of said fluid.

11. A method of analyzing a fluid flow as claimed in claim 1 wherein said predetermined anomaly is selected from the group consisting of a plug, a slug, and a pseudo-slug.

12. A method of analyzing a fluid flow as claimed in claim 1 wherein said primary upstream measuring point and said secondary upstream measuring point are positioned at distinct locations along said pipe.

13. A method of analyzing a fluid flow as claimed in claim 1 wherein said primary downstream measuring point and said secondary downstream measuring point are positioned at distinct locations along said pipe.

14. A method of analyzing a fluid flow as claimed in claim 1 wherein said primary pipe distance is greater than said secondary pipe distance.

15. A method of analyzing a fluid flow as claimed in claim 14 wherein said primary pipe distance is approximately 132 cm and said secondary pipe distance is approximately 10 cm.

16. A method of analyzing a fluid flow as claimed in claim 1 wherein said predetermined flow anomaly has a probable characteristic anomaly length and said primary pipe distance is greater than said probable characteristic anomaly length.

17. A method of analyzing a fluid flow as claimed in claim 1 wherein a pair of said predetermined flow anomalies are spaced apart by a probable anomaly spacing and said primary pipe distance is less than said probable anomaly spacing.

18. A method of analyzing a fluid flow as claimed in claim 1 wherein said second pair of pressure measuring points are positioned between said first pair of pressure measuring points.

19. An apparatus for identifying a predetermined flow anomaly in a pipe comprising:

an analysis pipe section;

a first pair of pressure measuring points provided in said analysis section and including a primary upstream measuring point and a primary downstream measuring point separated by a primary pipe distance;

a first differential pressure transducer coupled to said first pair of pressure measuring points;

a second pair of pressure measuring points provided in said analysis section and including a secondary upstream measuring point and a secondary downstream measuring point separated by a secondary pipe distance;

a second differential pressure transducer coupled to said second pair of pressure measuring points; and

a differential pressure output port coupled to said first and second differential pressure transducers and operative to produce an output from which a primary drop in said first differential pressure, a secondary pressure drop in said second differential pressure, and a time delay between initiation of said primary pressure drop and initiation of said secondary pressure drop are identifiable so as to enable determination of the presence of said predetermined flow anomaly.

20. An apparatus for identifying a predetermined flow anomaly as claimed in claim 19 wherein said primary upstream measuring point and said secondary upstream measuring point are positioned at distinct locations along said pipe.

21. An apparatus for identifying a predetermined flow anomaly as claimed in claim 19 wherein said primary downstream measuring point and said secondary downstream measuring point are positioned at distinct locations along said pipe.

22. An apparatus for identifying a predetermined flow anomaly as claimed in claim 19 wherein said primary pipe distance is greater than said secondary pipe distance.

23. An apparatus for identifying a predetermined flow anomaly as claimed in claim 22 wherein said primary pipe distance is approximately 132 cm and said secondary pipe distance is approximately 10 cm.

24. An apparatus for identifying a predetermined flow anomaly as claimed in claim 19 wherein said predetermined flow anomaly has a probable characteristic anomaly length and said primary pipe distance is greater than said probable characteristic anomaly length.

25. An apparatus for identifying a predetermined flow anomaly as claimed in claim 19 wherein a pair of said predetermined flow anomalies are spaced apart by a probable anomaly spacing and said primary pipe distance is less than said probable anomaly spacing.

26. An apparatus for identifying a predetermined flow anomaly as claimed in claim 19 wherein said second pair of pressure measuring points are positioned between said first pair of pressure measuring points.

27. An apparatus for identifying a predetermined flow anomaly as claimed in claim 19 wherein said predetermined anomaly is selected from the group consisting of a plug, a slug, and a pseudo-slug.

28. A method of identifying a predetermined multiphase flow anomaly in a pipe comprising the steps of:

identifying an analysis pipe section, said analysis pipe section containing a multiphase fluid flow;

measuring a first differential pressure over time at a first pair of pressure measuring points positioned along said analysis pipe section, said first pair of pressure measuring points including a primary upstream measuring point and a primary downstream measuring point separated by a primary pipe distance;

measuring a second differential pressure over time at a second pair of pressure measuring points positioned along said analysis pipe section, said second pair of pressure measuring points including a secondary upstream measuring point and a secondary downstream measuring point separated by a secondary pipe distance;

determining whether regular amplitude variations exist in said first pressure measurement over time and said second pressure measurement over time;

determining whether said existent regular amplitude variations include at least a first regular amplitude variation in said first pressure measurement having an absolute magnitude greater than a first minimum pressure differential;

determining whether said existent regular amplitude variations include at least a second regular amplitude variation in said second pressure measurement having an absolute magnitude greater than a second minimum pressure differential;

identifying a primary starting point of said first regular amplitude variation;

identifying a secondary starting point of said second regular amplitude variation; and

determining the nature of a predetermined multiphase flow anomaly moving through the pipe analysis section as a function of a time difference between said secondary starting point and said primary starting point.

29. A method of identifying a predetermined multiphase flow anomaly in a pipe as claimed in claim 28 wherein the nature of predetermined multiphase flow is determined as a function of the flow velocity of said anomaly, and wherein the flow velocity of said anomaly is a function of the time difference between said primary starting point and said secondary starting point.

30. A method of identifying a predetermined multiphase flow anomaly in a pipe as claimed in claim 29 comprising the step of indicating slug flow where the flow velocity of said anomaly is approximately 1.2 times a collective superficial velocity of the multiphase flow.

31. A method of identifying a predetermined multiphase flow anomaly in a pipe as claimed in claim 29 comprising the step of indicating pseudo-slug flow where the flow velocity of said anomaly is less than approximately 1.2 times a collective superficial velocity of the multiphase flow.

32. A method of identifying a predetermined multiphase flow anomaly in a pipe as claimed in claim 28 comprising the step of indicating plug flow where said existent regular amplitude variations do not include at least a first regular amplitude variation in said first pressure measurement having an absolute magnitude greater than a first minimum pressure differential and at least a second regular amplitude variation in said second pressure measurement having an absolute magnitude greater than a second minimum pressure differential.

33. A method of identifying a predetermined multiphase flow anomaly in a pipe as claimed in claim 28 comprising the step of indicating stratified/annular flow where no regular amplitude variations exist in said first pressure measurement over time and said second pressure measurement over time.