ABSTRACT

In this paper the results of an experimental study and the first field trials are presented where gas slugs are broken into small bubbles by a passive mechanical device we call a bubble breaker. The bubble breaker can be inserted into a vertical flow with the aim of increasing the void fraction downstream of it. It can be applied in gas lifted wells or naturally producing wells with associated gas.

In an 18 m high, 72 mm diameter test facility at Shell E&P Technology in Rijswijk several bubble breaker designs have been tested under a wide range of flow conditions. Experimentally we were able to (1) postpone the transition from bubbly to slug flow and (2) break up spherical caps and slugs into finely dispersed bubbles, which are sufficiently small to prevent them from re-coalescing, even far downstream of the bubble breaker. Big gas slugs could be broken into bubbles smaller than 1 mm. The pressure drop that is required to generate these small bubbles proved to be relatively small.

In 2004, a field trial has been conducted in a gas lifted well in Central Africa. Flowing gradient measurements show that the pressure drop of the flow above the bubble breaker could indeed be reduced by installing a bubble breaker. The first trials showed a 10% increase in production.

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