Method of wellbore operations

1. A method of operating a well comprising:

obtaining data from a well test that comprises a flow velocity of production fluid flowing in tubing disposed in the well;

adding a lift fluid to the tubing;

monitoring pressure in the tubing over time and at spaced apart locations;

introducing a detectable marker fluid into the tubing at a time when conditions in the well are substantially similar to conditions in the well during the well test, detecting the presence of the marker fluid at the spaced apart locations based on the step of monitoring pressure in the tubing, estimating a reference flow velocity of the production fluid based on a distance between the spaced apart locations and a time span between when the presence of the marker fluid is detected at the spaced apart locations;

introducing into the tubing an amount of marker fluid having a density different from a density of a mixture of the production fluid and lift fluid and at a point in time after the well test was performed, detecting the presence of the marker fluid at the spaced apart locations based on the step of monitoring pressure in the tubing, and estimating a real time flow velocity of the production fluid based on a distance between the spaced apart locations and a time span between when the presence of the marker fluid is detected at the spaced apart locations;

estimating a real time flowrate of the well based on the real time flow velocity of the production fluid and volume of tubing between the spaced apart locations; and

estimating a slip coefficient based on a ratio of the flow velocity from the well test and the reference flow velocity of the production fluid, and using the slip coefficient to adjust the real time flow velocity of the production fluid.

2. The method of claim 1 , further comprising adjusting an amount of the lift fluid being added to the stream based on the step of estimating the real time flowrate.

3. The method of claim 2 , wherein the amount of the lift fluid being added to the stream is adjusted so that an amount of production fluid being produced by the well is approximately the same as a designated amount of production fluid.

4. The method of claim 1 , wherein the step of introducing the marker fluid into the tubing comprises suspending the addition of lift fluid into the tubing for a designated period of time.

5. The method of claim 1 , wherein the marker fluid comprises a slug of production fluid in the tubing.

6. A method of operating a well comprising:

obtaining flow data of the well measured during a well test performed at a point in time;

providing a marker fluid in the well that comprises a cohesive slug of production fluid;

obtaining reference flow data of the well based on monitoring the marker fluid flowing in the well under conditions in the well that were similar to conditions in the well occurring during the point in time;

obtaining real time flow data of the well based on monitoring marker fluid flowing in the well after the point in time;

estimating a slip coefficient based on a ratio of the flow velocity from the well test and the reference flow velocity of the production fluid, and using the slip coefficient to adjust the real time flow velocity of the production fluid; and

controlling a flow of production fluid from the well based on the adjusted real time flow data.

7. The method of claim 6 , further comprising adding gas lift fluid to the well.

8. The method of claim 7 , wherein the step of controlling a flow of production fluid comprises adjusting an amount of the gas lift fluid added.

9. The method of claim 8 , wherein the amount of gas lift fluid being added to the stream is adjusted based on a ratio of the well test flow data and the reference flow data.

10. The method of claim 7 , wherein the production fluid is from a formation adjacent the well.

11. The method of claim 10 , wherein flow data of the well after the point in time is estimated by, introducing the slug of production fluid into production tubing disposed in the well, tracking the progression of the slug through the production tubing by monitoring pressure at locations in the production tubing that are spaced an axial distance apart, and estimating a flow velocity of the slug based on a travel time of the slug between the locations and the axial distance.

12. The method of claim 11 , further comprising suspending gas lift addition for a period of time to introduce the slug of production fluid into the production tubing.

13. The method of claim 11 , further comprising reducing gas lift addition for a period of time to introduce the slug of production fluid into the production tubing.

14. The method of claim 11 , wherein a flowrate of production fluid in the tubing is estimated based on the flow velocity of the slug, and a volume in the tubing between the locations.

15. The method of claim 14 , wherein a density of a column of the production fluid between the locations is estimated based on a difference in pressure monitored at the locations, and wherein an estimate of constituents in the production fluid is estimated based on the density.

16. The method of claim 6 , wherein the flow data of the well measured during a well test performed at a point in time comprises a flowrate of fluid flowing through the well, an identification of the constituents making up the fluid flowing through the well, and fluid properties of the constituents.

17. A method of operating a well comprising:

obtaining data from a well test that comprises a flow velocity of production fluid flowing in tubing disposed in the well;

adding a lift fluid to the tubing;

monitoring pressure in the tubing over time and at spaced apart locations;

introducing a detectable marker fluid into the tubing at a time when conditions of the fluid flowing in the tubing are similar to conditions of the fluid flowing in the tubing during the well test, detecting the presence of the marker fluid at the spaced apart locations based on the step of monitoring pressure in the tubing, estimating a reference flow velocity of the production fluid based on a distance between the spaced apart locations and a time span between when the presence of the marker fluid is detected at the spaced apart locations;

introducing into the tubing an amount of marker fluid having a density different from a density of a mixture of the production fluid and lift fluid and at a point in time after the well test was performed, detecting the presence of the marker fluid at the spaced apart locations based on the step of monitoring pressure in the tubing, and estimating a real time flow velocity of the production fluid based on a distance between the spaced apart locations and a time span between when the presence of the marker fluid is detected at the spaced apart locations;

estimating a real time flowrate of the well based on the real time flow velocity of the production fluid and volume of tubing between the spaced apart locations; and

estimating a slip coefficient based on a ratio of the flow velocity from the well test and the reference flow velocity of the production fluid, and using the slip coefficient to adjust the real time flow velocity of the production fluid.

18. The method of claim 17 , wherein the conditions are selected from the group consisting of temperature, pressure, fluid viscosity, and combinations.

19. The method of claim 17 , further comprising adjusting the real time flowrate based on a comparison of the well test and the reference flow velocity.