Title

A new production logging method for fullbore gas holdup measurements in cased wells

Document Type

Conference Proceeding

Publication Date

1-1-1996

Journal

Society of Petroleum Engineers - SPE Annual Technical Conference and Exhibition

DOI

10.2118/36562-ms

Abstract

© 1996 Society of Petroleum Engineers, Inc. The measurement of the gas holdup in a flowing cased-hole environment is a fundamentally difficult problem. Gas holdup, the estimate percent of gas in a volume of wellbore, has traditionally been computed from fluid density measurements. These estimates are inadequate for determining gas holdup in deviated or horizontal wells since the fluid density was not a fullbore measurement. A new Gas Holdup Tool (GHT (tm)) has been developed which provides a more accurate technique for obtaining gas holdup measurements directly. This 1 11/16-inch production logging tool is used to determine the volumetric fraction of gas in horizontal, deviated, and vertical cased wells, and provides a log of the gas holdup fraction (from 0% to 100%) in all flow regimes. Examples are presented for comparing homogeneous and stratified flows. The tool uses a low-energy Co-57 source and Nal detectors with a new backscatter technique to accurately measure density differences of the total fluid and gas in the borehole around the tool. This new measurement provides the gas fraction (holdup) in all flow regimes, and is not affected by the materials outside the casing. Monte Carlo modeling and experimental data over a wide range of cased-hole conditions validate empirical relationships between detector count rates and gas holdup for various casing diameters. The sensitivity of the measurement to other factors, such as pressure, salinity, and fluid type, are also investigated. The new production logging method may be used in determining points of gas and oil entry into deviated or horizontal wells and for quantitative production logging in deviated or horizontal wells with variable or unknown flow regimes.

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