Interpreting well test measurements

• US 8,620,636 B2
• Filed: 02/13/2007
• Issued: 12/31/2013
• Est. Priority Date: 08/25/2005
• Status: Active Grant

• Current Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Original Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Inventors: Zhan, Lang, Kuchuk, Fikri J., Filas, James G., Kannan, Dhandayuthapani
• Primary Examiner(s): Kim, Eunhee
• Application Number:
  US11/674,449
• Publication Number:
  US 20070162235A1
• Time in Patent Office: 2,513 Days
• Field of Search: 703/1, 703/10, 703/9, 700/282, 702/6
• US Class Current: 703/10
• CPC Class Codes: E21B 49/00 Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
• CPC Class Codes: E21B 49/008 by injection test; by analysing pressure variations in an injection or production test, e.g. for estimating the skin factor measuring pressure E21B47/06
• CPC Class Codes: E21B 49/081 with down-hole means for trapping a fluid sample E21B49/10 takes precedence
• CPC Class Codes: E21B 49/087 Well testing, e.g. testing for reservoir productivity or formation parameters
• CPC Class Codes: E21B 49/088 combined with sampling
• CPC Class Codes: G01V 1/40 specially adapted for well-logging

Abstract

Based on measurements that are obtained from a well test, a pressure in the well is modeled as a function of at least a skin effect factor that varies with time. The results of the modeling may be used to estimate at least one well parameter, such as a formation parameter and/or a well pressure, as examples.

Claims

1. A method comprising:

based on measurements obtained in a well during a dynamic fluid flow, modeling a pressure in the well as a function of at least a skin effect factor that varies with time; and

performing a test in the well to obtain the measurements, wherein performing the test comprises closing off a surge chamber in response to a downhole parameter measured in connection with the test.

2. The method of claim 1, further comprising:

using the results of the modeling to estimate at least one well parameter.

3. The method of claim 2, wherein said at least one well parameter comprises parameters selected from a group consisting essentially of a formation parameter and a well pressure.

4. The method of claim 1, further comprising:

performing a test in the well to obtain the measurements during a surge fluid flow entering the well due to an under-balanced pressure differential between the wellbore and the formation.

5. The method of claim 1, further comprising:

performing a test in the well to obtain the measurements during a time in which wellbore fluid is forced into the formation due to an over-balanced pressure differential between the wellbore and formation.

6. The method of claim 1, further comprising:

performing a test to obtain the measurements during a clean up operation in the well.

7. The method of claim 1, wherein the act of modeling the pressure comprises:

determining a sandface flow rate history associated with a test in which the measurements were obtained; and

generating a model for the sandface flow rate which corresponds to the sandface flow rate history.

8. The method of claim 7, further comprising:

calculating the flow history from pressure measurements made during the test.

9. The method of claim 7, further comprising:

measuring the sandface flow rate history directly from a flow meter device.

10. The method of claim 7, further comprising:

calibrating the flow history based on a produced volume of well fluid during the test.

11. The method of claim 1, wherein the act of modeling the pressure comprises:

modeling the pressure based on a flow rate that varies with time.

12. The method of claim 11, further comprising:

determining a model for flow rate history, comprising;

using at least one of single and piecewise functions.

13. The method of claim 12, wherein the function comprises at least one of the following:

a linear function, an exponential function, a polynomial function, a hyperbolic function and a parabolic function.

14. The method of claim 1, wherein the act of modeling the pressure comprises:

determining a skin effect factor history associated with a test in which the measurements were obtained; and

generating a model for the skin history factor which corresponds to the skin factor history.

15. The method of claim 14, wherein the act of determining the skin factor history comprises:

calculating the skin factor history based on a flow rate history and an estimated permeability.

16. The method of claim 1, wherein the modeled pressure comprises pressures at the corresponding locations of the measurements.

17. The method of claim 1, wherein the measurements comprise at least one of pressure measurements and temperature measurements.

18. The method of claim 1, further comprising:

generating a model for a skin factor history, comprising;

using at least one of single and multiple piecewise elementary functions.

19. The method of claim 18, wherein the function comprises at least one of the following:

a linear function, an exponential function, a polynomial function, a hyperbolic function and a parabolic function.