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Gas Hydrate Drilling Challenge

640 Meters of Permafrost

It’s technically challenging to drill through 640 meters of permafrost and 110 meters of gas hydrates — thermal and mechanical erosion of the borehole can result from transferring heat into the gas hydrates while drilling. Melting of the hydrates can cause slumping or possible blowouts from dissociation of the gas, water and sediments.

Image Caption

Gas Hydrate Rock

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It’s technically challenging to drill through 640 meters of permafrost and 110 meters of gas hydrates — thermal and mechanical erosion of the borehole can result from transferring heat into the gas hydrates while drilling. Melting of the hydrates can cause slumping or possible blowouts from dissociation of the gas, water and sediments.

Innovative drilling protocols, therefore, were developed for the Mallik 2002 research project — the mud was cooled to 2° Celsius, and the surface casing was insulated to reduce heat transfer into the gas hydrate zone.

The open hole logging program for Mallik 5L-38 included nuclear magnetic resonance, dipole sonic, and high resolution electrical conductivity and resistivity tools. A continuous core was cut from 885 to 1,151 meters, through the highly concentrated, main gas hydrate intervals and below a free gas interval. Downhole fibre optic temperature sensors measured in situ formation temperatures, noting changes during drilling and production tests.

Production testing at Mallik 5L-38 involved measuring gas and water flows at surface in response to depressurizing the gas hydrate reservoir. Five one-meter intervals were selected for pressure draw down experiments. Additionally, a 13-meter thick zone was perforated, enabling warm fluids to circulate into the gas hydrate reservoir for a period of seven to nine days.

Small-scale fractures were induced into the reservoir to determine the effects of fracturing on gas flow.

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