Periodic Wellbore-Water Accumulation and Off-Take

Abstract

Reliable representations of the accumulation and release of water from oil and condensate wellbores remain elusive due to the complexity of this random phenomenon. In this paper, spectral analysis is applied to strings of oilwell production rates to estimate the optimum flow regime and consequently predict its performance. The temporal rates of growth of fluid production are also calculated from wave theory. The dominant peaks of the spectral density curves calculated from flow-rate data correspond with calculated periods of the most unstable oscillation frequency of the instability theory. Observed well water-cut fluctuations, during fluid rate measurements, may therefore be explained by the periodic accumulation and off-take of water from the region around the wellbore. The frequency distribution of field data fluctuation is therefore used to identify the source of fluctuation generated by the flow mechanism. The present study reveals further information on the mechanism of production rate fluctuations and surging.