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A testing schedule
North Slope methane hydrate production testing anticipated in 2021-22
Alan Bailey Petroleum News
Permit applications filed with the Alaska Department of Natural Resources in conjunction with a project aimed at testing the long-term production of natural gas from methane hydrates on the North Slope indicate that the plan is to complete the drilling of wells for the project in the winter of 2021-22. That would be followed by the production testing program in 2021 or 2022.
ASRC Energy Services has applied to the Alaska Department of Natural Resources for a couple of permits for some preparatory work associated with the testing. The Department of Energy’s National Energy Technology Laboratory formed a partnership with Japan Oil, Gas and Metals National Corp., the U.S. Geological Survey and Petrotechnical Resources of Alaska to establish the testing project, referred to as the Alaska Methane Hydrate Project. As previously reported in Petroleum News, in December and January the partnership drilled a well from an existing gravel pad in the western part of the Prudhoe Bay unit, to evaluate methane hydrate resources at the site. BP operated the drilling project.
Two additional wells Assuming the resources prove workable for the testing, the plan is to drill two additional wells: a methane hydrate production well and a monitoring well, for determining the subsurface response to the production. The well that has already been drilled would become a second monitoring well. It now appears that the further drilling should happen next winter.
One of ASRC’s permit applications is for the installation of a downhole temperature monitoring system for the well that has already been drilled. The second application seeks permission for off road travel, to install equipment for monitoring any surface subsidence that may occur as a consequence of subsurface gas production from hydrates.
Potential natural gas resource Methane hydrate is a solid in which molecules of methane, the primary component of natural gas, are concentrated inside a lattice of water molecules. Huge quantities of the material, which remains stable within a certain range of relatively high pressures and low temperatures, are known to exist around the base of the permafrost under the North Slope. Gas can be released from hydrates through some combination of elevating the temperature or reducing the pressure of the hydrate resource. Although there have been demonstrations of short-term hydrate production, no one has yet conducted a sustained, long-term production test.
Given the existence of extensive oil and gas infrastructure on the North Slope and given the fact that the hydrates are on land rather than subsea the Slope is thought to be a particularly suitable location for methane hydrate testing.
Excellent reservoirs According to the NETL’s latest Fire in the Ice publication, the well that was completed in January penetrated two highly saturated hydrate-bearing reservoirs. The deeper of these reservoirs consists of very fine-grained sand to coarse silt, with methane hydrate saturation levels ranging from 65% to 80% in the upper 40 feet of the reservoir unit. The shallower unit is also an outstanding methane hydrate reservoir, similar to the lower reservoir. The deeper reservoir, close to the base of the zone in which hydrates remain stable, appears particularly suitable for production testing. And the shallower reservoir could provide further opportunities for investigating scientific and well design issues, along with follow-on production testing, the NETL publication says.
Initial work Although the plans for the methane hydrate testing indicate that the testing will not start until at least 2021, the two ASRC Energy permit applications indicate the need to start some preliminary work, well ahead of that testing.
The surface subsidence monitoring involves placing GPS equipment at a series of predetermined locations around the test site, according to a plan filed with the application for an off-road travel permit. Following installation, the research team will use the equipment to set baseline elevation measurements, against which any future subsidence can be determined. Measurements will be conducted monthly up to the time when the production testing starts, but with weekly surveys carried out during the first month of measuring. Surveying will continue during the anticipated 12 months of production testing. A further 12 months of surface elevation measurements will continue after the testing ends.
Installation of the temperature monitoring system involves placing a Connex container holding a battery bank and wind-powered generator for powering the system a few feet west of the well house of the well that has already been drilled. Fiber optic cabling used for the temperature monitoring has already been installed in the well, the plan says.
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