Reservoir Heterogeneity Assessment of Depleted Oil and Gas reserves
Categorization, prioritization, and selection of one or two target geologic assessment units for detailed modeling. Development of comprehensive computational models that will allow us to better understand the three-dimensional variability of reservoirs and predict the behavior of fluids within these reservoirs.
DIAL Carbon Dioxide Monitoring
Development of small, relatively low cost, low power DIfferential Absorption Lidar (DIAL) systems for probing atmospheric concentrations of CO2 above storage sites and around pipelines.
Subsurface Biofilm Barriers
Development of engineered biofilm barriers for reducing leakage of supercritical CO2 through aquitards, as well as restricting the migration of CO2 leaks which have penetrated through aquitards.
Modeling and Mapping
Reservoir Heterogeneity Assessment
Injection of CO2 into geologic formations has been practiced by the petroleum industry for enhanced oil recovery for several decades. Due to the economic incentives, established oil and gas infrastructure, and national interests in securing greater energy independence, Enhanced Oil Recovery (EOR) projects are the most likely candidates for initial large scale CO2 sequestration. However, significant hurdles to large scale sequestration must first be overcome through a significant research effort. It is not yet possible to predict with confidence storage volumes of CO2, injection efficiency of CO2, seal integrity and migration leakage pathways of CO2, and permanence of CO2 storage over geologic time periods. Many important issues dealing with geologic storage, monitoring and verification of CO2 in underground oil and gas reservoirs must be addressed. Pilot demonstrations are also needed to confirm practical considerations such as CO2 sequestration/EOR economics, project safety, CO2 stability and permanence in the subsurface environment, and public education and support for such projects.
To be effective, joint sequestration/EOR projects will involve the injection of very large volumes of CO2 in close proximity to point sources or will utilize existing oil and gas pipeline infrastructure to move CO2 from point sources to suitable injection project areas. To accomplish this it is necessary to predict reservoir storage capacity, fluid flow efficiency in the reservoir as a function of stratigraphic and structural heterogeneity, potential leakage pathways from the reservoir, and the repeatability of the process from one field to the next within a petroleum system.
To date research concerning Enhanced Oil recovery (EOR) using CO2 injection and CO2 sequestration has been primarily at two disparate scales; (1) at the pore throat to individual field scale, and (2) at very large basinwide scales based on general screening criteria. An important body of research needs to be undertaken at the intermediate scale of individual fields to assessment units such that reservoir complexity and heterogeneity is documented in a systematic way that results in knowledge that can be applied to entire producing trends, assessment units, and petroleum systems. The research then provides for repeatable sequestration targets within a given assessment unit and provides important analogs for similar assessment units nationwide.
Tremendous technological advances have been made in recent years that dramatically affect the ability to understand reservoirs at this intermediate scale. These include paradigm shifts in understanding the stratigraphy of sedimentary rocks as a function of changes in accommodation and rates of sediment supply, technological breakthroughs in the power of computer hardware and software for reservoir characterization, modeling, and simulation, and the acquisition and interpretation of three-dimensional seismic data. These advances have important implications to the study of CO2 sequestration. We can now better understand the three-dimensional variability of reservoirs and predict the behavior of fluids within these reservoirs than at any time in the past.
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DIAL Carbon Dioxide Monitoring
Dr. Repasky and Dr. Carlsten
There is clear need for sensitive methods of above ground monitoring for carbon dioxide leaks. Any such methods would also have application to monitoring Leaks in CO2 pipelines. One possible candidate is differential absorption lidar (DIAL), but because of the significant CO2 background and naturally occurring variations in atmospheric concentrations, it is desirable to leave the monitor in place for extended periods in order to get sufficient background data. This is incompatible with many current lidar systems that are very high priced and are typically only available for 1-14 days for any given measurement. MSU has pioneered the development of compact, low cost lidar systems based on diode lasers and MSU developed technology to control, shift, and tune the diode wavelength. Figure 1 illustrates the performance of a diode based lidar system developed at MSU for the measurement of water vapor. This system uses an external cavity diode laser and does not require wavelength shifting. The high resolution available makes it conceivable to detect isotopically labeled species.
Carbon dioxide has strong absorption features at 2.0μm, 2.8μm, 4.4μm, and 4.8μm. Using the strong absorption features of the carbon dioxide molecule, an optical sensor is proposed for above ground monitoring. A schematic of the proposed sensor is shown in Fig.(2). The output from a continuous wave (cw) tunable laser is reflected from a retro-reflector, passes through a narrow band filter and is incident on a photo-detector. The laser is tuned across an absorption feature of the carbon dioxide and an optical power as a function of wavelength plot is generated. The amount of light absorbed is directly related to the number of carbon dioxide molecules in the beam path. Multiple retroflectors in a circular pattern and a turning mirror laser can be used to allow measurement over a larger area. A second carbon diode sensor will be placed away from the underground storage site and will be used to monitor background changes in the atmospheric carbon dioxide concentrations.
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Mitigation: Subsurface Biofilm Barriers
Dr. Cunningham, Dr. Gerlach, Dr. Mitchell, Dr. Skidmore —For more information visit the Center for Biofilm Engineering
This component of the research project focuses on developing strategies and technologies for controlling leakage of Supercritical CO2 during geologic sequestration. This project will examine the use of engineered microbial biofilm barriers as a method for reducing permeability of confining aquitard layers in the vicinity of CO2 injection and, likewise, providing a zone of reduced permeability to mitigate further migration of CO2 leaks which have penetrated the aquitard and reached overlying strata.
Biofilm barrier technology involves the injection and subsurface transport of starved bacterial cultures followed by resuscitation with injected growth substrates. This process results in the production of copious amounts of extracellular polymer (EPS), as well as associated mineral deposits, which plugs the free pore space of the formation thereby reducing porosity and hydraulic conductivity. This zone of reduced hydraulic conductivity from a barrier which will serve as a means for controlling undesirable migration of contaminants including supercritical CO2. Attractive aspects of biofilm barrier technology for enhancing geologic CO2 sequestration include: 1) biofilm barrier construction can be achieved without excavation and therefore may be useful at sites where access to the subsurface is restricted; 2) there is no obvious depth limitation with biofilm barrier technology; and 3) once established, the biofilm barrier requires minimal maintenance for long-term operation. Biofilm barrier research results to date are reported in Mitchell et. al 2009.
Biomineralization research concept. Biofilm communities in the subsurface are also able to actively precipitate calcium carbonate minerals from the ambient Ca+2 and HCO3- in the subsurface water. However, by stimulating native subsurface microbial communities, or by adding specific microorganisms and growth media, we may be able to engineer the biomineralization process in beneficial ways. One feasible mechanism by which to generate calcium carbonate precipitation in the subsurface is by bacterial hydrolysis of urea, known as ureolysis. The CBE ZERT research team has made considerable progress toward developing the concept of engineered biofilms (in porous media) which are capable of precipitating mineral deposits (i.e. calcium carbonate) within the biofilm matrix. This concept is very attractive in that is suggests the possibility to develop a CO2 migration barrier composed of biofilm and mineral deposits which, once in place, may be very stable over long time periods. Research results on biomineralization barriers are reported in Cunningham et. al, 2008.
Biomineralization of anthropogenic CO2. Our research has also determined that ureolytic biomineralization is capable of sequestering anthropogenic CO2 for the gas phase into the mineral phase there by facilitating a method for permanent sequestration of CO2 injected into the subsurface as well as from waste streams above ground, as reported by (Mitchell, et al. 2008).
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ZERT is funded by the United States Department of Energy, under Award No. DE-FC26-04NT42262. However, any opinions, findings, conclusions, or recommendations expressed herein are those of the author(s) and do not necessarily reflect the views of the DOE.
© 2005 Montana State University