Formation characterization of the Lamotte Sandstone in southwestern Missouri

This research details an evaluation of the Lamotte Sandstone fundamental rock properties, in order to answer the question, Could the Lamotte Sandstone be used as a formation for CO 2 sequestration? This question is important as more stringent air quality regulations require CO2 to be sequestered in some manner, rather than be released to the atmosphere. Review of historical literature revealed that the Lamotte formation is a transgressive, upwardly fining sandstone, with up to six different lithofacies. Four coreholes were identified as available for study near the City Utilities southwest power plant in Springfield, Missouri. Corehole NS-3 was selected for study as this corehole fell on a historical cross-section and had been previously described. Visual inspection of the NS-3 core identified four sandstone zones, designated zone #1 through zone #4. These zones corresponded to the lower portion of the Bonneterre dolomite and facies #6 through facies #3 of the Lamotte. Routine core analysis of fourteen samples from the four zones revealed that zones #3 and #4 have higher porosity than zones #1 and #2. However the permeability in zones #1, #2 and #4 were lower than zone #3. The fundamental properties for zone #3 were 10.6% porosity with 139 mD maximum permeability. XRD analysis of six samples from the four zones indicated that of the clays present in the formation, most of the clay is either illite or kaolinite, with a much smaller presence of montmorillonite. SEM photographs of the samples revealed kaolinite clay structures, and pore sizes that were consistent with the porosity measured for each zone. A storage capacity calculation for the Lamotte zone #3 suggests that 21 MMscf of gas could be stored in the formation for every acre-ft of bulk reservoir rock (8 foot thickness for Zone #3 = 168 MMscf/acre). This calculation was made assuming that the connate water saturation from whole core analysis correctly represents the formation residual water saturation. This calculation also assumes no chemical reaction between the carbon dioxide and formation minerals, and any brine already in the reservoir could be evacuated or displaced. Considering all facies, the Lamotte Sandstone is thick. Well NS-3 has a reported Lamotte thickness of 132 feet. However, not all of the formation thickness has similar storage properties, as shown in this report. Some facies have low permeability which would indicate a low potential injectivity. In summary, it appears that the Lamotte Sandstone would have the capacity to store CO2 but a more comprehensive study with a greater number of samples from fresh core is advised --Abstract, pages iii-iv