Interpreting well test measurements
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.
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.