Seth David Humphries

Testing carbon sequestration site monitor instruments using a controlled carbon dioxide release facility

Two laser-based instruments for carbon sequestration site monitoring have been developed and tested at a controlled carbon dioxide (CO(2)) release facility. The first instrument uses a temperature tunable distributed feedback (DFB) diode laser capable of accessing the 2.0027-2.0042 microm spectral region that contains three CO(2) absorption lines and is used for aboveground atmospheric CO(2) concentration measurements. The second instrument also uses a temperature tunable DFB diode laser capable of accessing the 2.0032-2.0055 mum spectral region that contains five CO(2) absorption lines for underground CO(2) soil gas concentration measurements. The performance of these instruments for carbon sequestration site monitoring was studied using a newly developed controlled CO(2) release facility. A 0.3 ton CO(2)/day injection experiment was performed from 3-10 August 2007. The aboveground differential absorption instrument measured an average atmospheric CO(2) concentration of 618 parts per million (ppm) over the CO(2) injection site compared with an average background atmospheric CO(2) concentration of 448 ppm demonstrating this instruments capability for carbon sequestration site monitoring. The underground differential absorption instrument measured a CO(2) soil gas concentration of 100,000 ppm during the CO(2) injection, a factor of 25 greater than the measured background CO(2) soil gas concentration of 4000 ppm demonstrating this instruments capability for carbon sequestration site monitoring.

Differential absorption measurements of carbon dioxide using a temperature tunable distributed feedback diode laser

The design and performance of an absorption measurement instrument for monitoring carbon dioxide are presented. The instrument is based on a temperature tunable distributed feedback diode laser capable of tuning between 2.001 and 2.005μm. Within this wavelength range are 12 absorption lines for carbon dioxide and 9 absorption lines for water vapor. Initial measurements of laser transmission as a function of carbon dioxide concentration are made using a 2m long absorption cell. The measured values compare well with the expected values using the known line strength of the carbon dioxide absorption feature. Carbon dioxide measurements over a 77.5m path length made outside the laboratory show the potential for carbon dioxide concentration monitoring.