A downhole gas separator for methane production from geopressured aquifers

The downhole gas separator is a semipermeable device that produces methane gas from solution in brine by a diffusion process. It is in the form of a 6 in (15·2 cm) diameter, 1000 ft (303 m) long cylinder located downhole near the brine/methane-producing formation. As brine flows upward past the separator, 90 percent of the brine methane is extracted while 60 percent and 19 percent of the brine carbon dioxide and hydrogen sulfide, respectively, are extracted. The preferential extraction of methane over carbon dioxide and hydrogen sulfide, achieves a purification of the product gas. Subsequently, the brine flows further upward and into a shallower disposal reservoir penetrated by the same wellbore; surface brine handling is entirely eliminated. The separator is assembled at the wellhead from one hundred 10 ft (3 m) long segments in the fashion of a production string. Because of operations at near bottomhole pressures, maintenance requirements due to calcite scale are reduced substantially over surface-type equipment.