M. Strutt

Soil Gas as a Monitoring Tool of Deep Geological Sequestration of Carbon Dioxide: Preliminary Results from the Encana EOR Project in Weyburn, Saskatchewan (Canada)

Publisher Summary Carbon dioxide injection into the EnCana (formerly Pan Canadian) oil reservoir, located south of Weyburn, Saskatchewan, Canada, is being undertaken for enhanced oil recovery (EOR) purposes, while at the same time, the site is being studied for the feasibility of environmental sequestration of this gas. The systematic measurement of soil gas concentration and gas flux at locations above the Phase 1A injection site provides data to construct a baseline of near surface soil gas geochemistry. Data for CO2, CO2 flux, O2, CH4, radon (222Rn), thoron (Tn or radioisotope 22°Rn), and helium, along with other permanent gases, sulphur species, and light hydrocarbons are being collected at yearly intervals for a period of three years, while radon is also being continuously monitored for seasonal and diurnal variations using in situ probes. The Istituto Nazionale di Geofisica e Vulcanologia (INGV) CO2 flux survey measured all 360 points, whereas the initial URS soil gas survey measured 217 points for Rn and Tn, 291 points for field gas chromatography, and 292 sites for laboratory measured gases. The BGS soil gas sampling program completed the southern third of the grid except for 16 sampling sites in the southeast comer that could not be sampled due to a late harvest. The British Geological Survey (BGS), Bureau de Recherches Grologiques et Minieres (BRGM) and INGV also completed gas measurements along 4 profiles. The profiles were defined from anomalies detected during the initial grid sampling, in conjunction with structural data for the immediate area. Natural background levels and concentration distributions have been established for the measured soil gases, and by comparing these results with future data sets, it will be possible to estimate CO2 storage integrity for the reservoir rocks.

Imaging a growing lava dome with a portable radar

The tiny Caribbean island of Montserrat has been in a state of crisis since the Soufriere Hills Volcano (SHV) began its current eruption in July 1995. With its main town, Plymouth, destroyed by pyroclastic flows in 1997, the islanders who have remained have had to rebuild their society on the northern half of the island under varying degrees of threat from the volcano to the south. During this time, the Montserrat government continues to receive advice on the volcanic hazards from the Montserrat Volcano Observatory (MVO). The continuing eruption has provided a wealth of research opportunities for many international groups who sought to study the growth and repeated partial destruction of a Peleean andesitic lava dome. There have been three episodes of dome growth: November 1995 through March 1998, November 1999 through July 2003, and August 2005 to present. Pyroclastic flows and explosions have been the main source of hazard.The pyroclastic flows have been generated mainly by gravitational collapse of the lava dome, but also by collapse of explosive ash columns. The dome collapses tend to occur from the area of the dome where new lava is being added. Similarly collapses are more likely when the rate of lava extrusion varies. Also, the propensity of explosive evacuation of the magma in the conduit is partly controlled by the magma supply rate, with high rates favoring explosions.

Soil gas as a monitoring tool of deep geological sequestration of carbon dioxide: Results from the three year Monitoring of the Encana Eor Project, Weyburn, Saskatchewan (Canada)

Publisher Summary As part of the IEA Weybum CO2 Monitoring and Storage Project, preliminary baseline soil gas data was collected in the summer and autumn of 2001 above the injection area of the EnCana Enhanced Oil Recovery project at the Weybum oilfield in south Saskatchewan. The 2001 data was presented at GHGT-6 in Kyoto. In the autumns of 2002 and 2003, further in situ monitoring of CO2, CO2 flux, O2, CH4, radon (222Rn), and thoron (220Rn) was carried out. Soil gas samples were also collected for the laboratory analysis of helium, permanent gases, sulfur species, and light hydrocarbons. All sampling was repeated over the same 360 point sampling grid and more detailed profiles for both follow-up years. Marked changes in CO2 levels (especially flux) for each of the three-year datasets indicated changes in surface conditions. The radon and thoron data was found to be similar for the three years, but appeared to vary in response to drift composition and seasonal effects, rather than migration from a deep source.