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.
Please log in to read the full article
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.