Economic
Production of Sandbed Methane from Ground Water
Player,
Methane can occur as a solute in ground
water, or as undissolved “free” bubbles of gas. Sand
Bed Methane is recoverable methane that occurs
dissolved in ground water in permeable layers of sandstone and loose sands.
Dissolved gas from aquifers with high enough gas water ratios (GWR) can be
economically produced by pumping ground water to the surface, recovering the
methane in separators, and returning the water to the same aquifer.
High pressures that exist at great depths
provide relatively high methane solubility in ground water aquifers. Laboratory
research data and production histories from Japanese Sand Bed Methane wells
show that dissolved methane concentrations range from about 10 cubic feet of
methane per 42 gallon barrel of water at 3,000 feet below ground, to about 30
cubic feet of methane per barrel of water at 10,000 feet below ground. Where
reservoir rocks contain unrecovered free gas from a
depleted gas field, along with dissolved gas, the GWR could be much higher. For
example the GWR in water recovered from a "blown down" gas field
could be more than 100 cubic feet per barrel.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California