Gaseous hydrocarbons around an active offshore gas and oil field

Abstract

From the Abstract: “Low molecular weight hydrocarbons (LMWHs, C1-C4) were measured from the water column and sediments around an oil and gas field. No significant differences in mean methane levels were observed between platforms that were and were not discharging brine. However, in the 20-station grid, the relative standard deviations were greater and the highest individual methane and ethane concentrations were found in surface waters near the platform discharging brine. Higher methane values at all depths observed during summer coinciding with decreased ethanelethene ratios in a near-bottom nepheloid layer provided direct evidence of in situ biological production associated with increases in zooplankton and bacterial biomass in the water column. The sediment LMWHs are predominantly of thermogenic origin probably due to seepage from the subsurface, as evidenced by high levels of methane and elevated ethanelethene ratios. The LMWH input from brine discharge in the field is estimated at 283 g/day.”