Dave Jones from the British Geological Survey (BGS) has been to In Salah, Algeria several times for field work. He has been involved in CCS since the start of the Weyburn project in 2001 and first visited In Salah in August 2004. More recently he was there in March 2009 and November/December 2009.
Harsh desert environment
Jones: ‘In Salah is a very remote site in a very hot, dry, harsh desert environment. Conditions are very difficult in summer – too hot to work in the middle of the day and constant vigilance needed to avoid dehydration. In March temperatures are much more pleasant, but we were surprised by the amount of rain! The rain even delayed our departure because the dirt airstrip at Krechba could not be used safely until it had dried out. In November-December it was actually quite cold until mid-late morning. Other challenges are dust and the hard ground conditions (outcrops and gravel) that make sampling rather difficult
The main goal of the first trip in 2004 was to find out what was possible – a kind of pilot study and a chance to get true baseline measurements as injection of CO2 was just starting. This was funded by BP prior to work for CO2ReMoVe. We found that conventional shallow gas techniques were challenging because of the very dry, permeable ground conditions, which allowed atmospheric air to dilute the shallow soil gas. However, background concentrations of gases were very low compared to more vegetated temperate sites, so any leakage could be easier to detect.
We obtained small numbers of measurements at different sites:
- the 3 injection wells
- the original discovery well for the field (KB-1)
- above the crest of the main gas reservoir
- a background site to the West (well away from the reservoir and CO2 injection).
Our recommendation was for shallow boreholes to be drilled (5-10m) to provide sites for monitoring gas below the zone of atmospheric dilution. This could be via a mix of periodic surveys (measuring gases from time to time) and continuous monitoring (with more permanently installed equipment).
Gas measurements and microbiology
In March 2009 we tested mobile laser equipment to measure near-ground atmospheric gas in conjunction with more traditional soil gas concentration and flux measurements. Also colleagues from BRGM installed some more continuous monitoring equipment – Barasol probes to measure the natural tracer gas radon and integrative samplers (activated charcoal) to collect a wider range of gases and heavy metals. These tools are still in place and we will only have data once they are recovered (in March 2010 hopefully). The open path mobile laser results show the difficulties of carrying out such measurements in such a dusty environment. The soil gas and flux measurements gave similarly low values to those in 2004, which were confirmed by laboratory analyses at the University of Rome. We are still completing working on the data.
During the Nov/Dec trip in 2009, we looked at the plant species in the area, particularly around the three injection wells, and at aspects of the soil microbiology. Soil gas measurements and fluxes were made at each site. In addition we repeated and extended the mobile laser work. Given the very low gas concentrations this provided baseline data and was a feasibility study for carrying out work in a desert environment.
That was carried both under the EU-projects CO2GeoNet and CO2ReMoVe. In CO2ReMove, BGS is involved in Monitoring Tool Development – in particular looking at the use of mobile infrared laser systems as rapid surveying methods – and monitoring near surface gases at In Salah and, hopefully, Weyburn.