Fugitive emissions of methane from abandoned, decommissioned oil and gas wells.

This study considered the fugitive emissions of methane (CH4) from former oil and gas exploration and production wells drilled to exploit conventional hydrocarbon reservoirs onshore in the UK. This study selected from the 66% of all onshore wells in the UK which appeared to be properly decommissioned (abandoned) that came from 4 different basins and were between 8 and 79 years old. The soil gas above each well was analysed and assessed relative to a nearby control site of similar land use and soil type. The results showed that of the 102 wells considered 30% had soil gas CH4 at the soil surface that was significantly greater than their respective control. Conversely, 39% of well sites had significant lower surface soil gas CH4 concentrations than their respective control. We interpret elevated soil gas CH4 concentrations to be the result of well integrity failure, but do not know the source of the gas nor the route to the surface. Where elevated CH4 was detected it appears to have occurred within a decade of it being drilled. The flux of CH4 from wells was 364 ± 677 kg CO2eq/well/year with a 27% chance that the well would have a negative flux to the atmosphere independent of well age. This flux is low relative to the activity commonly used on decommissioned well sites (e.g. sheep grazing), however, fluxes from wells that have not been appropriately decommissioned would be expected to be higher.

A novel extractionless hplc fluorescence method for the determination of glyburide in the human plasma: application to a bioequivalence study.

PURPOSE: To develop a simple, sensitive and rapid HPLC fluorescence method with single step sample preparation for the determination of glyburide in the human plasma. METHODS: Glyburide and ketoconazole (internal standard) were extracted from the 0.5 mL plasma by addition of 0.5 mL acetonitrile and 50 microL CuSO(4) solution (5% w/v in water). The separation was achieved on the Kingsorb 3 microm, C8 reverse phase column at ambient temperature with a mobile phase consisted of 45% buffer solution (0.05 M NH(4)H(2)P(4)), 40% acetonitrile and 15% methanol adjusted to pH 5.7 by diluted ammonia solution. A fluorescence detector was set at 235 nm excitation wavelength and 354 nm emission wavelengths to monitor eluted components. RESULTS: The internal standard and glyburide eluted at about 6.7 and 9.6 min, respectively at the flow rate of 1 mL/min. The regression equation was established for every calibration curves (5 ng/mL to 400 ng/mL), which resulted in the correlation coefficient of 0.99 or greater. The absolute recovery ranged from 94.32 to 98.12% and the relative recovery ranged from 91.12 to 97.15%. The intraday coefficient of variation (CV) ranged from of 6.52 to 12.35% and interday varied from 6.21 to 16.07%. The limit of quantitation (LOQ) of glyburide was set to five ng/mL. CONCLUSION: This simple, rapid and sensitive method is suitable for pharmacokinetic, bioavailability and biequivalence studies.