David L. Van Rooy and Fred A. Vesperman
Schlumberger Well Services, Houston, Texas
ABSTRACT
We describe a new way to calibrate FBS (Full Bore Spinner) and CFS (Continuous Flowmeter Sonde) flowmeters and to determine the total (uncorrected) fluid velocity profile. This method is designed to use more of the log data, and model the spinner response more accurately. Whereas previous methods were designed for engineers using calculators, this approach uses the computer to extract more information from the log.
In our method, we obtain the calibration by using the data in all stable flowing zones, rather than just one. The calibration lines are constrained based on the known range of spinner thresholds and slopes. Program logic rejects data that falls outside preset “unreasonable” limits, and recognizes invalid computed answers. For flexibility, the user may override the computed values for calibration slopes or intercepts.
A new method is presented for determining the total uncorrected fluid velocity from the computed slopes and intercepts. It is a general method that encompasses the two-pass overlay and slope-intercept methods and more.
Our results indicate that this method represents a significant improvement over existing automated methods, particularly for troublesome cases.