ABSTRACT

The new production logging tool discriminates between water and hydrocarbons (oil and gas) by means of four identical probes symmetrically positioned across the wellbore. Each probe is a bubble detector that yields one of two outputs, depending on whether it ?sees? water or hydrocarbons. Because of its binary nature, the measurement readily provides water holdup, without prior knowledge of water, oil or gas densities required for the calibration of a standard gradiomanometer. Unlike the gradiomanometer, the new measurement does not have to be corrected for friction effect or well deviation. Because of its local nature, the new measurement provides an image of the distribution of segregated fluids across the wellbore. This feature can help in understanding segregated flow regimes, especially in deviated wells. The bubble count (number of dispersed fluid bubbles observed per second) is very sensitive in detecting first oil entries and individual perforation contributions. The use of the new measurement is illustrated by a field example where a leaking bottom plug was suspected to be responsible for the well?s high water cut. It unequivocally identifies the source of water production where conventional sensors would have been inconclusive and provides the justification for a workover that resulted in blocking water entries and increasing oil production by a factor of three.

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