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High-Pressure Research

Natural underground processes that generate oil and gas from coal are being reproduced by Coal Research Limited at Gracefield on equipment designed and built at Victoria University.

The aim of the three-year study by Dr Tim Moore, Dr Tony Clemens and Len Damiano is to establish the pathways by which underground processes generate methane (and other off-gases) and liquid hydrocarbons from New Zealand coals.

"The oil and gas in the Taranaki basin were probably generated from coal by such processes so it is important that we understand them as fully as possible," Clemens says. The processes are believed to occur at temperatures around 125^oC and pressures in excess of 400 atmospheres.

As lignites convert to higher-rank (bituminous) coals, varying amounts of gases and liquid hydrocarbons may form. Previous studies at Coal Research have identified certain physical and chemical attributes that appear to give some lignites good potential for releasing significant amounts of oil and gas as they mature. The aim now is to take samples of these promising lignites and subject them to the high temperatures and pressures found underground, using the equipment built at Victoria University.

The Coal Research team will be able to see to what extent they change into bituminous coals, and will determine the yield of liquid hydrocarbons and composition of the gases obtained through these processes. It is also intended to try the experiments on lignites that contain little of the oil-prone coal types and observe whether a corresponding decrease in hydrocarbons and gas yield does indeed occur. It is anticipated that experiments will run from one to four months, and changes will be modified at regular intervals throughout.

"This is thought to be the first project to use geologically realistic conditions to try and confirm the oil and gas generating potential of specific coal types. If successful it will considerably aid future petroleum exploration, utilisation and management," Clemens says.