Alex van der Spek

Downhole Fiber-Optic Flowmeter: Design, Operating Principle, Testing, and Field Installations

This paper discusses the design, operating principles, flow-loop testing, and initial field installations of the worlds first all-fiber-optic flowmeter for downhole deployment. The flowmeter provides real-time measurement of the flow rate, phase fraction, pressure, and temperature. It is deployed with the production tubing and is rated to 125°C and 15,000 psi. It is fullbore, nonintrusive, electrically passive, has no moving parts, and overcomes the design limitations imposed by downhole environments. Thus, it has the potential to provide highly reliable downhole measurements. The flowmeter has been tested extensively in industrial flow loops in a wide range of conditions. Results from the testing have demonstrated the flowmeters ability to measure flow rates and water fractions in oil/water systems to within ′5% for the entire range of water cuts. These results have been validated by data from several field deployments.

Characterizing Sound Generated by Multiphase Flow

A new method for analyzing multiphase flow in wells using acoustic noise and capacitance log data is presented. Although using noise log to detect channeling is a well-established science for vertical wells, their interpretation in highly deviated and horizontal wells is difficult. Little attention has been paid to the shape of the spectra and their relationship to the multiphase flow or to their relationship to well deviation. The acoustic spectra can be decomposed into a background contribution, due to multiphase flow, and an extraneous component. Based on theoretical considerations, we explained the slope of the background spectra. The extraneous component is attributed to activities outside the casing or to fluid entries into the well. There are two steps in interpreting the noise log data. The first step uses time series analysis of capacitance data to determine the flow regime. Then the noise generated by that flow regime can be characterized since each flow regime has a unique acoustic fingerprint (due to its unique turbulence structure). The second step is to identify the extraneous fluid flow signature. Sound generated by fluid channeling and fluid entry is superimposed on the background sound, which is generated by turbulent fluid motion inside the wellbore. Therefore, the deviation from background sound spectra is assumed to be caused by other sources, such as fluid channeling. Field examples indicate that the identification and characterization of background noise makes the acoustic log interpretation a valuable source for determining fluid channeling in multiphase flow horizontal wells.