Abstract
An experimental study on bubble (slug) rise inside a pipe filled with static liquid and bull heading of a gas flow with a liquid flow is presented. The bubble rise velocity (BRV) was measured inside a pipe with different inclinations and is compared with two well-known models. The static tests have been performed with three different liquids: water, CaCl brine mixture, and non-Newtonian fluid (Xanvis™). A model is proposed, based on the drift flux method, to predict the bubble rise velocity. Dynamic well killing (or top kill) is also examined, whereby a continuous gas flow is suppressed with a counter current liquid flow. Flow tests at different angles from vertical were undertaken to investigate the effect of inclination on the liquid flow rate needed to bullhead the gas flow. A simple empirical model based on the results is proposed to predict the results in actual wells.
Highlights
A blowout is defined as an uncontrolled flow of formation fluids from a wellhead or wellbore
An experimental study on bubble rise inside a pipe filled with static liquid and bull heading of a gas flow with a liquid flow is presented
Gas may be released as individual bubbles or slugs when there is not enough flow to initiate a continuous stream of gas or a continuous stream when the gas flow is sufficient
Summary
A blowout is defined as an uncontrolled flow of formation fluids from a wellhead or wellbore. We started our measurements using a vertical pipe and increased the angle by 15° increments up to 75° The results for these tests are compared to models from Wallis (1969) and Carew et al (1995) for the inclination effect on the static bubble rise velocity. If the viscosity number is large a simple model from Wallis (1969) is kl 1⁄4 0:345ð1 À eð3:37ÀEo=10Þ ð11Þ This governs the BRV for smaller diameter pipes where surface tension effects become important. The first series tests showed that the dynamic kill velocity and static BRV are both similar functions of inclination angle, with the maximum liquid flow to kill a flowing gas wellbeing maximum at an inclination angle around 60°.
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