Common Wisdom on Gas Behavior Is Called Into Question

John Kozicz of Transocean speaks during an OTC panel discussion about managing natural gas in marine risers. Paul Sonnemann of Safekick is to his right, and Robert Ziegler of RZI Deepwater is the third person from the right.

The prospect of natural gas in a riser commonly summons up a vision of a deadly, fast-rising bubble exploding on to the floor of a drilling rig. But comments by consultants on an OTC panel argued that it is a poor description of how gas behaves in a deepwater riser.

Research and experience indicate that the movement of a volume of gas is not nearly as fast or unified in a mud-filled deepwater riser as widely assumed. A trip up a mile-long riser can take hours during which the gas disperses like carbonation in a can of cola. For most of the trip it is in a liquid form.

“A major problem is that many people focus on riser gas velocity, rather than behavior caused by gas that may not actually be ‘rising’ at all, but is nonetheless ‘expanding,’” said Paul Sonnemann, vice president of technology for Safekick. While gas is capable of expanding in an almost explosive fashion if it is released into the air, he said this can be “delayed by either slow migration, or by dispersion of the gas in a long fluid column.”

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Common Wisdom on Gas Behavior Is Called Into Question

Stephen Rassenfoss, JPT Emerging Technology Senior Editor

01 August 2015

Volume: 67 | Issue: 8

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