Choke performance in high-rate gas condensate wells under subcritical flow condition

Abstract

Flow through a surface choke can be described as either critical or subcritical. Most of the correlations available to petroleum engineers are for critical flow but in a lot of high rate gas/condensate wells subcritical flow occurs in large choke sizes. Field data of 15 high rate wells producing from 10 gas condensate reservoirs located in Iran were used to extend two main approaches for high rate wells: a plotting technique proposed by Al-Attar to describe the subcritical flow behavior of gas condensates through wellhead chokes and a general Gilbert-type formula obtained by nonlinear regression of data points for high rate gas condensate wells. The present study extends the work of Al-Attar for high rate gas condensate wells flowing through different large choke sizes between 40/64 and 192/64 in. under subcritical flow conditions, in order to develop individual empirical correlations to be applied to predict gas flow rates under a wide range of flow conditions usually encountered during the flow of gas condensates through wellhead chokes in high rate wells .Also, a new Gilbert-type correlation was generated for high rate Iranian gas condensate wells using nonlinear regression based on the same data points. A comparison between these two approaches is done with five different errors parameters. According to five different errors analysis, the results of gas flow rates calculated by the general formula were compared with those calculated by the individual choke size formulae, and the latter were found to be more accurate. The results of this study could be considered in the design and implementation of deliverability tests, pressure transient tests, well control, and long-term well production of high rate gas condensates wells.