Otway demonstration project - soil gas monitoring 2013

Abstract

The final soil gas monitoring survey for this regulatory period took place in March 2013. Soil gas monitoring surveys have been performed around the Otway Project demonstration site since 2005. It was carried out annually and mainly in summer (Feb-Mar) over a defined grid covering a study area of 4 km x 3 km (11 km2). The injection wells (CRC-1 and CRC-2) and monitoring well (Naylor-1) are located in the central south of the study area. The sampling grid covered and deliberately extended beyond the proposed migration pathways of the two CO2 injections performed so far. The purpose of the entire study was to perform baseline and assurance monitoring surveys of the soil gas composition in the Otway Project area. It focuses on CO2 and CH4 as they were the two main components of the gas mixture injected in 2008 and 2011. Advanced analytics included oxygen, nitrogen, helium and tracer (SF6 and Kr) composition analysis as well as delta13C measurements. Here we present the final (2013) dataset, a comparision with baseline data (2006-2008) is made. It shows, that a deep subsurface source (or leakage of the injected CO2 to the near surface) is not apparent in the soil gas data.