Locating and measuring low volume gas entries is a critical problem in many Devonian Shale wells in the Appalachian Basin, since many of the small gas entries are below the resolution of conventional geophysical logging tools.

The Low Volume / High Resolution Flowmeter (HRFM) is an extremely sensitive flow measurement tool consisting of three basic parts. The lowest part of the tool contains the sensor section which is comprised of a pressure transducer and a tracer gas reservoir positioned below a tracer gas detector; the central section contains the gamma ray detector for lithology correlation in both open and cased holes; and the upper part of the tool contains the casing collar locator for cased hole referencing.

Flowrate is determined by injecting a tracer gas into the gas flow. The dilution of the tracer gas is then measured at a downstream detector. The mass flow is therefore determined by this method ratherthan the velocity of the gas in the wellbore as measured by conventional production logging spinner surveys. Therefore, the HRFM can measure a full spectrum of flow rates independent of variables which may affect other conventional production logging equipment including gas composition, inclination of the wellbore, temperature, size of tool, irregular borehole diameters and large variations in gas flow rates from different pay zones in the well.

The HRFM is capable of being stacked with other geophysical tools for both open and cased hole operations in vertical and horizontal wells.

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