Study of Slug Flow in Undulated Horizontal Wells

Abstract

Terrain induced slugging have become more common as the petroleum industry matures. Late-life fields, deepwater fields and marginal subsea tiebacks to existing facilities are prone to terrain induced slugging. Extended reach wellbore, including snake wells, fish-hook wells and undulated wells are relative new technologies used to drain otherwise not economically feasible hydrocarbon zones. These well trajectories are, however, prone to terrain induced slugging since they can resemble a pipeline-riser system containing low spots over large distances to accumulate large liquid slugs. Conventional methods of handling slug flow includes choking, gas injection at the riser base or installation of a slug catcher. These methods have drawbacks of reducing production rates, requiring large amounts of gas or high cost. Lately, automatic slug control based on feedback control systems can suppress the slugs, but becomes unstable when operating conditions change. This study attempts to assess the potential of a rotating device to mechanically break down liquid slugs in the gas-liquid interface and/or influence multiphase flow in any significant and beneficial way. Experiments were performed by placing the device in vertical, inclined and horizontal sections. It was seen that the device in some cases influenced the slug flow behaviour, especially in horizontal flow direction. The frequency increased while the average slug length decreased significantly over a short distance. It was further seen that the impact in vertical direction and bend sections were insignificant for the test conditions in this study.