Theses and Dissertations at Montana State University (MSU)
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Item A fiber optic array for the detection of sub-surface carbon dioxide at carbon sequestration sites(Montana State University - Bozeman, College of Engineering, 2014) Soukup, Benjamin John; Chairperson, Graduate Committee: Kevin S. RepaskyA fiber sensor array for sub-surface CO 2 concentrations measurements was developed for monitoring geologic carbon sequestration sites. The fiber sensor array uses a temperature-tunable distributed feedback (DFB) laser outputting a nominal wavelength of 2.004 microns. Light from this DFB laser is directed to one of the four probes via an in-line 1x4 fiber optic switch. Each of the probes is placed underground and utilizes filters that allow only soil gas to enter the probe. Light from the DFB laser interacts with CO 2 within the probe before being directed back through the switch. The DFB laser is tuned across two CO 2 absorption features where a transmission measurement is made, allowing the CO 2 concentration to be retrieved. This process is repeated for each probe, allowing CO 2 concentration measurements to be made as a function of time for each probe. The fiber sensor array was deployed for fifty-eight days at the Zero Emission Research Technology (ZERT) field site and for a twenty-eight day period at the Kevin Dome geologic carbon sequestration site. Background measurements indicate the instrument can monitor background levels as low as 1,000 parts per million (ppm). During a thirty-four day sub-surface CO 2 release, elevated CO 2 concentrations were readily detected by each of the four probes with values ranging to over 60,000 ppm.Item Carbon dioxide sequestration monitoring and verification via laser based detection system in the 2 micron band(Montana State University - Bozeman, College of Engineering, 2008) Humphries, Seth David; Chairperson, Graduate Committee: Kevin S. RepaskyCarbon Dioxide (CO 2) is a known contributor to the green house gas effect. Emissions of CO 2 are rising as the global demand for inexpensive energy is placated through the consumption and combustion of fossil fuels. Carbon capture and sequestration (CCS) may provide a method to prevent CO 2 from being exhausted to the atmosphere. The carbon may be captured after fossil fuel combustion in a power plant and then stored in a long term facility such as a deep geologic feature. The ability to verify the integrity of carbon storage at a location is key to the success of all CCS projects. A laser-based instrument has been built and tested at Montana State University (MSU) to measure CO 2 concentrations above a carbon storage location. The CO 2 Detection by Differential Absorption (CODDA) Instrument uses a temperature-tunable distributed feedback (DFB) laser diode that is capable of accessing a spectral region, 2.0027 to 2.0042 microns, that contains three CO 2 absorption lines and a water vapor absorption line. This instrument laser is aimed over an open-air, two-way path of about 100 m, allowing measurements of CO 2 concentrations to be made directly above a carbon dioxide release test site. The performance of the instrument for carbon sequestration site monitoring is studied using a newly developed CO 2 controlled release facility. The field and CO 2 releases are managed by the Zero Emissions Research Technology (ZERT) group at MSU. Two test injections were carried out through vertical wells simulating seepage up well paths. Three test injections were done as CO 2 escaped up through a slotted horizontal pipe simulating seepage up through geologic fault zones. The results from these 5 separate controlled release experiments over the course of three summers show that the CODDA Instrument is clearly capable of verifying the integrity of full-scale CO 2 storage operations.