Gas Holdup Imaging Identifies Complex Gas-Liquid Flow Regimes and Introduces a New Velocity Measurement In a Long, Cased Hole, Horizontal, Production Well

摘要

Gas holdup probes run in a producing horizontal well onthe Norwegian continental shelf are used to identify downholeflow regimes and compute the velocity of gas inintermittent flow.The observed flow regimes are compared with thepredictions of a number of gas-liquid flow correlations. Thetheory and quality of velocity correlations are discussed.IntroductionA number of horizontal gas-liquid flow models exist andare routinely used to predict the down hole flow regime thatwill be encountered under normal production and loggingoperations. As these models tend to be derived from, orvalidated by, surface observations at relatively low pressuresand low gas densities it would be reassuring to test or validatethese models under real down-hole conditions.The identification of correct flow regime is important forthe production log interpretation, as it dictates which slipmodel to use. In particular the ability to distinguish dispersedbubble flow from the other flow regimes is important as slipeffects are believed to be negligible in dispersed bubble flow.Similarly the stratified and intermittent flow regimes mayhave quite different slip velocities.Traditional global measurements of nuclear density or asingle dielectric sensor cannot directly see the downhole flowregime. Only the recent introduction of distributed gas holdupprobes in production logging toolstrings permits the downholeflow regime to be imaged and determined.This technique was applied to a North Sea well producingsaturated oil and gas from a 1400 m horizontal. The well iscompleted with a 7” cemented and perforated liner. In thisexample, due to the happy conjunction of an undulating wellpath and a steadily increasing flow rate, the productionlogging sensors can see stratified flow, intermittent flow, andbubble flow. This, almost textbook, collection of flow regimesis tested against a number of models to see how well themodels agree with this particular reality.As the local probes are not only distributed radially aroundthe borehole, but also separated axially, the delay betweenholdup disturbances (in intermittent flow regimes) as theytravel from one tool to another can be converted into avelocity. This has been performed and a gasvelocity computed.