Characterizing Flow Through Perforations Using Ultrasonic Doppler

by
Muhammad Razi, MSE

University of Texas at Austin, 1994
Supervisor: Dr. Steven L. Morriss

The objective of this study is to determine the feasibility of using an ultrasonic Doppler measurement to determine the velocity of fluid flow from perforations into a wellbore. Since the diameter of perforations can be estimated with reasonable accuracy, flow rate from a perforation can be determined. Preliminary work has been conducted using single phase flow (water) into a water-filled 6" I.D pipe. Continuous ultrasound waves are propagating across the well bore from a distance of one focal length (10 cm) of the transducer. Present emphasis is on comparison of reflected waveforms at different flow rates. Time domain samples of the Doppler signal are transformed into the frequency domain using a Fast Fourier Transform. This transform gives us a Doppler frequency distribution due to the fluid jet coming out of the perforation. This frequency distribution is converted into the velocity distribution, which in turn gives information about flow rate. Comparison of the calculated flow rates with actual flow rates is quite encouraging, and it appears that it is possible to determine flow rate from each perforation. This approach to the determination of downhole flow rate promises to be the solution to a long-standing measurement problem, and could have significant economic impact in the petroleum industry

Note: Please see SPE 29544 for more comprehensive study.

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