Browsing by Subject "CO2"
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Item A Comparison of Fault Detection Methods For a Transcritical Refrigeration System(2012-10-19) Janecke, Alex KarlWhen released into the atmosphere, traditional refrigerants contribute to climate change several orders of magnitude more than a corresponding amount of carbon dioxide. For that reason, an increasing amount of interest has been paid to transcritical vapor compression systems in recent years, which use carbon dioxide as a refrigerant. Vapor compression systems also impact the environment through their consumption of energy. This can be greatly increased by faulty operation. Automated techniques for detecting and diagnosing faults have been widely tested for subcritical systems, but have not been applied to transcritical systems. These methods can involve either dynamic analysis of the vapor compression cycle or a variety of algorithms based on steady state behavior. In this thesis, the viability of dynamic fault detection is tested in relation to that of static fault detection for a transcritical refrigeration system. Step tests are used to determine that transient behavior does not give additional useful information. The same tests are performed on a subcritical air-conditioner showing little value in dynamic fault detection. A static component based method of fault detection which has been applied to subcritical systems is also tested for all pairings of four faults: over/undercharge, evaporator fouling, gas cooler fouling, and compressor valve leakage. This technique allows for low cost measurement and independent detection of individual faults even when multiple faults are present. Results of this method are promising and allow distinction between faulty and fault-free behavior.Item Amine volatility in CO₂ capture(2013-05) Nguyen, Bich-Thu Ngoc; Rochelle, Gary T.This work investigates the volatilities of amine solvents used in post-combustion CO₂ capture from coal-fired power plants. Amine volatility is one of the key criteria used in screening an amine solvent for CO₂ capture: (1) amine losses up the stack can react in the atmosphere to form ozone and other toxic compounds; (2) volatility losses can result in greater solvent make-up costs; (3) high losses will require the use of bigger water wash units, and more water, to capture fugitive amines prior to venting - these translate to higher capital and operating costs; (4) volatilities need to be measured and modeled in order to develop more accurate and robust thermodynamic models. In this work, volatility is measured using a hot gas FTIR which can determine amine, water, and CO₂ in the vapor headspace above a solution. The liquid solution is speciated by NMR (Nuclear Magnetic Resonance). There are two key contributions made by this research work: (1) it serves as one of the largest sources of experimental data available for amine-water volatility; (2) it provides amine volatility for loaded systems (where CO₂ is present) which is a unique measurement not previously reported in the literature. This work studied the volatility of 20 alkanolamines in water at 0.5 - 1.1 molal (m) in water (< 1.5 mol% amine) at zero loading (no CO₂) from 40 ° - 70 °C. An empirical group contribution model was developed to correlate H[subscript 'amine'] to molecular structures of both alkylamines and alkanolamines. The model incorporated additional functional groups to account for cyclic structures and to distinguish between different types of alkyl groups based on the attached neighboring groups. This model represented the experimental H[subscript 'amine'], which spanned five orders in magnitude, to well within an order of magnitude of the measured values. The second component of this research involves upgrading the AspenPlus® v.7.3 model of MDEA-PZ-CO₂-H₂O system primarily by improving MDEA thermodynamics for MDEA-H₂O, MDEA-CO₂-H₂O, and MDEA-PZ-CO₂-H₂O. A key modification was made to include the carbonate (CO₃²⁻) species into the model chemistry set which greatly improved the fit of CO₂ solubility for MDEA-CO₂-H₂O at ultra lean loading ([alpha]) for 0.001 < [alpha] < 0.01. With MDEA-PZ-H₂O, no MDEA-PZ cross interaction parameters were needed to match the blend volatility. Ultimately, both the blend volatility, at unloaded and loaded conditions, along with speciation were adequately represented by the upgraded model. The final component of this research involves screening the volatilities of novel amines at unloaded and nominal lean loading condition from 40 ° - 70 °C (absorber operating conditions). The volatility of tertiary and hindered amines, such as MDEA and AMP, respectively, is not a strong function of loading because these amines are unable to form stable carbamates. Conversely, the volatility of mono-amines and of diamines decreases by ~3 and 5-20 times, respectively, due to a much greater extent of carbamate-forming speciation. PZ or a blend having a diamine promoted by PZ would be favorable for CO₂ capture due to the low volatility of the diamines in loaded solution. . Finally, in order of increasing degree of salting out as reflected by the increasing magnitude of the system asymmetric amine activity coefficient, 7 m MDEA < 4.8 m AMP ~ 7 m MDEA/2 m PZ < 8 m PZ < 7 m MEA.Item Analysis of Field Development Strategies of CO2 EOR/Capture Projects Using a Reservoir Simulation Economic Model(2013-05-03) Saint-Felix, MartinA model for the evaluation of CO2-EOR projects has been developed. This model includes both reservoir simulation to handle reservoir properties, fluid flow and injection and production schedules, and a numerical economic model that generates a monthly cash flow stream from the outputs of the reservoir model. This model is general enough to be used with any project and provide a solid common basis to all of them. This model was used to evaluate CO2-EOR injection and production strategies and develop an optimization workflow. Producer constraints (maximum oil and gas production rates) should be optimized first to generate a reference case. Further improvements can then be obtained by optimizing the injection starting date and the injection plateau rate. Investigation of sensitivity of CO2-EOR to the presence of an aquifer showed that CO2 injection can limit water influx in the reservoir and is beneficial to recovery, even with a strong water drive. The influence of some key parameters was evaluated: the producer should be completed in the top part of the reservoir, while the injector should be completed over the entire thickness; it is recommended but not mandatory that the injection should start as early as possible to allow for lower water cut limit. Finally, the sensitivity of the economics of the projects to some key parameters was evaluated. The most influent parameter is by far the oil price, but other parameters such as the CO2 source to field distance, the pipeline cost scenario, the CO2 source type or the CO2 market price have roughly the same influence. It is therefore possible to offset an increase of one of them by reducing another.Item Application of Polymer Gels as Conformance Control Agents for Carbon Dioxide for Floods in Carbonate Reservoirs(2012-10-15) Al Ali, Ali 1986-With the production from mature oil fields declining, the increasing demand of oil urges towards more effective recovery of the available resources. Currently, the CO2 Floods are the second most applied EOR processes in the world behind steam injection. With more than 30 years of experience gained from CO2 flooding, successful projects have showed incremental oil recovery ranging from 7 to 15 % of the oil initially in place. Despite all of the anticipated success of CO2 floods, its viscosity nature is in heterogeneous and naturally fractured reservoirs is challenging; CO2 will flow preferentially through the easiest paths resulting in early breakthrough and extraction ineffectiveness leaving zones of oil intact. This research aims at investigating gel treatments and viscosified water-alternating-gas CO2 mobility control techniques. A set of experiments have been conducted to verify the effectiveness and practicality of the proposed mobility control approaches. Our research employed an imaging technique integrating an X-Ray CT scanner with a CT friendly aluminum coreflood cell. With the integrated systems, we were able to obtain real time images when processed provide qualitative and qualitative evaluations to the coreflood. The research studies included preliminary studies of CO2 and water injection performance in fractured and unfractured cores. These experiments provided a base performance to which the performances of the mobility control attempts were compared. We have applied the same methodology in evaluation of the experimental results to both conformance control gel treatments and viscosified water-alternating-gas CO2 mobility control. The gel conformance control studies showed encouraging results in minimizing the effect of heterogeneities directing the injected CO2 to extract more oil from the low permeability zones; the gel strength was evaluated in terms of breakdown and leakoff utilizing the production data aided with CT imaging analysis. The viscosified water coupled with CO2 investigations showed great promising results proving the superiority over neat CO2 injection. This research serves as a preliminary understanding to the applicability of tested mobility control approaches providing a base to future studies in this category of research.Item Application of X-ray CT for investigating fluid flow and conformance control during CO2 injection in highly heterogeneous media(Texas A&M University, 2005-08-29) Chakravarthy, DeepakFractured reservoirs have always been considered poor candidates for enhanced oil recovery. This can be attributed to the complexities involved in understanding and predicting performance in these reservoirs. In a fractured system, the high permeability fracture forms the preferred pathway for the injected fluids, and a large amount of oil that is stored in the matrix is bypassed. Hence, a good understanding of multiphase fluid flow in fractures is required to reduce oil bypass and increase recovery from these reservoirs. This research investigates the effect of heterogeneity and injection rates on oil bypass and also the various techniques used for the improvement of sweep efficiency in heterogeneous systems. Several coreflood experiments were performed using homogeneous and heterogeneous cores and a 4th generation X-Ray CT scanner was used to visualize heterogeneity and fluid flow in the core. Porosity and saturation measurements were made during the course of the experiment. The experimental results indicate that injection rates play a very important role in affecting the recovery process, more so in the presence of fractures. At high injection rates, faster breakthrough of CO2 and higher oil bypass were observed than at low injection rates. But very low injection rates are not attractive from an economic point of view. Hence water viscosified with a polymer was injected directly into the fracture to divert CO2 flow into the matrix and delay breakthrough, similar to the WAG process. Although the breakthrough time reduced considerably, water ??leak off?? into the matrix was very high. To counter this problem, a cross-linked gel was used in the fracture for conformance control. The gel was found to overcome ??leak off?? problems and effectively divert CO2 flow into the matrix. This experimental research will serve to increase the understanding of fluid flow and conformance control methods in fractured reservoirs.Item Assessing the effect of reservoir heterogeneity on CO₂ plume migration using pressure transient analysis(2012-12) Punase, Aarti Dinesh; Srinivasan, Sanjay; BRYANT, STEVENThe ultimate success of carbon capture and storage project will be ensured only when there is a safe and effective permanent storage of CO₂ for a significant amount of time without any leakages. Credible monitoring and verification is one of the most important aspects of CO₂ sequestration. Accurate reservoir characterization is an important pre-requisite for the design, operation and economic success of processes like CO₂ sequestration. The techniques available include geophysical and geochemical monitoring as well as numerical simulations using models replicating the field. In conducting the numerical simulations, it is required to assess the reservoir heterogeneity correctly. Previous work has shown that the injection data from wells can be utilized for developing models during CO₂ sequestration to understand the spatial distribution of heterogeneities in the formation. In this research, we first understand and examine the information contained in the injection data for a wide range of reservoir models demonstrating different kinds of heterogeneities and rate fluctuations. We will confirm that the reservoir heterogeneities have an imprint on the injection pressure response and they influence CO₂ plume migration significantly. Later we show that the effect of high or low permeability features along with rate fluctuations can provide considerable information about permeability heterogeneity in the reservoir. The applicability of this observation is made using field data from In-Salah gas field from central Algeria. Thus we demonstrate the feasibility of developing an inexpensive method of modeling reservoir heterogeneity by employing readily available measurements of injection pressure and rate to track CO₂ migration. Later we describe method to find out what characteristics of the reservoir heterogeneities can be quantified using injection data (pressure and rate). The injection pressure response during CO₂ sequestration will depend strongly on reservoir, fluid and well properties. A 3-D analytical model with infinite acting boundary is developed in CMG-GEM. Compositional reservoir simulation results from CMG-GEM simulator will be obtained and combined with pressure transient analysis and optimization algorithm for the prediction of reservoir parameters. In case of multiple injection wells in a heterogeneous formation, the analysis yield spatial variations in reservoir parameter groups like transmissibility (kh), permeability to porosity ratio ([kappa]/[phi]) in different part of the reservoir. These parameter groups can subsequently be used to constrain models of reservoir thickness, permeability and porosity. Thus, we imply that multiple reservoir attributes affect migration of CO₂ plume and there is uncertainty associated with the estimation of these attributes. We present an approach to resolve some of that uncertainty using information extracted from injection well response.Item Carbon capture and storage potential contribution to mitigate climate change(2009-12) Baca, Angel Mario; Bickel, J. Eric; Duncan, Ian J.; Gutierrez, Genaro J.Carbon Capture and Storage Potential Contribution to Mitigate Climate Change By Angel Mario Baca, M.A. The University of Texas at Austin, 2009 Supervisor: Dr. Eric Bickel This thesis evaluates the potential of the Carbon Capture and Storage technologies to mitigate climate change. This work emerged from the current debate regarding when CCS technologies are going to be ready in a commercial-scale, or whether they are going to be economically viable. Geologically, the world contains enough room for storing CO2 emissions, but it is still unsolved if leakage can be controlled and monitored. This research focuses on the development of an economic model to estimate the value of CCS.. This model uses equations from the DICE (Dynamic Integrated model on Climate and the Economy). Then, it estimates what change in temperature could occur, and computes the present value of damages to the economy. Moreover, emissions are simulated using the 40 scenario emissions from the Intergovernmental Panel on Climate Change. As the main conclusion of this model, CCS has to be deployed in almost in the entire number of fossil fuel plants around the world and has to be done in the next 30 years to see CCS having an impact, otherwise it would be relatively small and not worth it. Moreover, CCS technologies are part of the components to reduce climate change, but not the main one. It is required that governments, companies, and institution focus their efforts in working collaboratively towards the enforcement of new policies and development of more technologies.Item Conversion of CO2 to Polycarbonates and Other Materials: Insights through Computational Chemistry(2014-09-25) Yeung, Andrew DThe use of carbon dioxide as a chemical feedstock for the copolymerization with epoxides to give polycarbonates, and for coupling with hydrocarbons to give carboxylic acids, was probed using computational chemistry. Metal-free systems were modeled at high levels using composite methods that give ?chemical accuracy?, whereas metal-bound systems were studied using density functional theory, benchmarked to these high-accuracy results for confidence. The thermodynamics of polymer vs. cyclic carbonate formation was calculated, and polymer is the exothermic product, whereas cyclic carbonate is the entropic product. The barriers for the metal-free carbonate and alkoxide backbiting reactions were also determined, carbonate backbiting having a higher barrier than alkoxide backbiting. The base degradation of polymers to epoxide co-monomers, and the acid- and base-catalyzed degradation of glycerol carbonate to glycidol were investigated too. Poly(cyclopentene carbonate) preferentially degrades to epoxide co-monomer instead of cyclic carbonate due to angle strain for alkoxide backbiting. Conversely, glycerol carbonate only yields glycidol instead of the isomeric 3-hydroxyoxetane because formation of the latter has a higher barrier. The (salen)Cr(III)- and (salen)Co(III)-catalyzed copolymerization reactions were studied for a variety of epoxides, and the overall displacement of a polymeric carbonate by an epoxide, followed by ring-opening, was found to be rate limiting. Chromium(III)-catalyzed systems have higher free energy barriers than cobalt(III) systems due to enthalpy, which explains why such polymerization reactions have to be run at higher temperatures. The metal-bound polymer carbonate and alkoxide backbiting reactions generally have higher barriers than when unbound, due to the terminal oxygen atoms? reduced nucleophilicity. The carboxylation of metal-hydride and metal-carbon bonds was studied for a series of trans-ML2XY complexes, and thermodynamics of carboxylation of the M-X bond are influenced by M, L, and Y, in decreasing order. Similar cis-complexes did not exhibit as clear trends. Examination of these complexes indicated that the three steps for the overall conversion of hydrocarbons to carboxylic acids (oxidative addition of hydrocarbon, carboxylation, and reductive elimination of the carboxylic acid) must be optimized in parallel for the successful direct synthesis of carboxylic acids.Item Coupling of CO_(2) and CS_(2) with Novel Oxiranes: Polycarbonate vs. Cyclic Carbonate Production(2013-07-09) Wilson, Stephanie JoPolycarbonates are a type of engineering thermoplastic that have countless uses in modern society. Currently, the major industrial production of polycarbonates involves the polycondensation of a diol and phosgene or phosgene derivative. Though there are many advantages to this process, it creates large amounts of waste and requires dangerous chemicals in order to proceed. Over the past four decades, the coupling of CO_(2) and epoxides has grown into a viable, greener alternative for the production of select polycarbonates. The byproduct of this reaction, cyclic carbonates, also have use as polar, high boiling solvents. This dissertation will be divided into three parts. First, the coupling of indene oxide and CO_(2) to form poly(indene carbonate) and cis-indene carbonate will be discussed. Poly(indene carbonate) has the highest Tg yet reported for polymers derived CO_(2) /epoxides coupling, up to 138degreeC. Polycarbonate production requires the use of (salen)Co(III) catalysts and low temperatures, though some cyclic carbonate production is still observed. Selective production of poly(indene carbonate) has been achieved through the use of bifunctional cobalt(III) complexes. The effects of temperature and cosolvent choices on polymer production will be thoroughly discussed. Though polycarbonate is the kinetic product from the coupling of CO_(2) and epoxides, the thermodynamic product is cyclic carbonate. There are six potential mechanisms that yield this undesired byproduct, though there is limited research into which pathways are the most active during polymerization reactions. Temperature-dependent kinetic studies were performed to obtain the activation parameters for the direct, polymer-free coupling of cyclopentene oxide, indene oxide, 1,2-butylene oxide, and styrene oxide with CO_(2) utilizing (salen)CrCl/nBu_(4)NCl to yield their corresponding cyclic carbonates. Additionally, the metal-free backbiting of the singly-coupled styrene oxide/CO_(2) intermediate was simulated utilizing the halohydrin 2-chloro-1-phenylethanol. Finally, the coupling of cyclopentene oxide with carbon disulfide to yield poly[thio]carbonates and cyclic [thio]carbonates utilizing (salen)CrCl/PPNX will be discussed. In each reaction, scrambling of the oxygen and sulfur atoms in both the polymeric and cyclic product is observed. Long reaction times lead to increased amounts of [thio]ether linkages and therefore polymers with lower glass transition temperatures. Insights into both the coupling and scrambling mechanisms will be presented.Item Effect of flue gas impurities on the process of injection and storage of carbon dioxide in depleted gas reservoirs(Texas A&M University, 2005-11-01) Nogueira de Mago, Marjorie CarolinaPrevious experiments - injecting pure CO2 into carbonate cores - showed that the process is a win-win technology, sequestrating CO2 while recovering a significant amount of hitherto unrecoverable natural gas that could help defray the cost of CO2 sequestration. In this thesis, I report my findings on the effect of flue gas ??impurities?? on the displacement of natural gas during CO2 sequestration, and results on unconfined compressive strength (UCS) tests to carbonate samples. In displacement experiments, corefloods were conducted at 1,500 psig and 70??C, in which flue gas was injected into an Austin chalk core containing initially methane. Two types of flue gases were injected: dehydrated flue gas with 13.574 mole% CO2 (Gas A), and treated flue gas (N2, O2 and water removed) with 99.433 mole% CO2 (Gas B). The main results of this study are as follows. First, the dispersion coefficient increases with concentration of ??impurities??. Gas A exhibits the largest dispersion coefficients, 0.18-0.25 cm2/min, compared to 0.13-0.15 cm2/min for Gas B, and 0.15 cm2/min for pure CO2. Second, recovery of methane at breakthrough is relatively high, ranging from 86% OGIP for pure CO2, 74-90% OGIP for Gas B, and 79-81% for Gas A. Lastly, injection of Gas A would sequester the least amount of CO2 as it contains about 80 mole% nitrogen. From the view point of sequestration, Gas A would be least desirable while Gas B appears to be the most desirable as separation cost would probably be cheaper than that for pure CO2 with similar gas recovery. For UCS tests, corefloods were conducted at 1,700 psig and 65??C in such a way that the cell throughput of CO2 simulates near-wellbore throughput. This was achieved through increasing the injection rate and time of injection. Corefloods were followed by porosity measurement and UCS tests. Main results are presented as follows. First, the UCS of the rock was reduced by approximately 30% of its original value as a result of the dissolution process. Second, porosity profiles of rock samples increased up to 2.5% after corefloods. UCS test results indicate that CO2 injection will cause weakening of near-wellbore formation rock.Item Excel model for electric markets : ERCOT(2016-05) Cuevas, Pedro Pablo; Dyer, James S.; Butler, John C.(Clinical associate professor); Hahn, JoeThe effects of changing regulatory and fuel-cost environments have far reaching implications on the ability of electric markets to plan and provide cheap, clean, and reliable electric grids. The current state of the art tools for modeling the regulations and fuel prices requires days to process and access to these tools is also held by a small number licensed users that must also have the training and technical ability to run the model, which limits the study of planning and electricity market design.. This thesis presents an Excel model that simulates the operations of ERCOT over the next fifteen years. Tradeoffs between accuracy, run time, cost, and model complexity will be discussed. The advantages of this model are speed and accessibility, which will allow more users to understand the major implications of policy discussions and scenarios without needing a commercial tool. The model predicts the fuel mix and average market price for 2014 with less than a 1% and 2% error respectively. For 2015, the model predicts the fuel mix with less than a 5% error. Using the current trends assumptions, the model predicts that by 2030 the energy mix will undergo significant changes. Coal generation will drop from 28% to 21%, while gas generation will decline from 48% to 46%. Renewable generation will increase with wind going from 12% to 17% and solar from 0% to 7%. The model also predicts that a carbon tax between $20 and $60 per short ton of CO2, could rise the operational and capital costs of ERCOT in present value terms until 2030 from $75 billion to $218 billion. Finally the model forecasts that the reserve margin in ERCOT will not reach the target of 13.75% in 2020 and that renewable energy addition does not affect this indicator. Even more, the reserve margin is increased when solar energy enters the market.Item Experimental and Simulation Studies to Evaluate the Improvement of Oil Recovery by Different Modes of CO2 Injection in Carbonate Reservoirs(2011-02-22) Aleidan, Ahmed Abdulaziz S.Experimental and numerical simulation studies were conducted to investigate the improvement of light oil recovery in carbonate cores during CO2 injection. The main steps in the study are as follows. First, the minimum miscibility pressure of 31?API west Texas oil and CO2 was measured using the slimtube (miscibility) apparatus. Second, miscible CO2 coreflood experiments were carried out on different modes of injection such as CGI, WF, WAG, and SWAG. Each injection mode was conducted on unfractured and fractured cores. Fractured cores included two types of fracture systems creating two shape models on the core. Also, runs were made with different salinity levels for the injected water, 0 ppm, 60,000 ppm, and 200,000 ppm. Finally, based on the experimental results, a 2-D numerical simulation model was constructed and validated. The simulation model was then extended to conduct sensitivity studies on different parameters such as permeability variations in the core, WAG ratio and slug size, and SWAG ratio. The results of this study indicate that injecting water with CO2 either simultaneously or in alternating cycles increases the oil recovery by at least 10 percent and reduces the CO2 requirements by 50 percent. The salinity of the injected water has shown a detrimental effect on oil recovery only during WAG and SWAG injections. Lowering injected water salinity, which increases the CO2 solubility in water, increases oil recovery by up to 18 percent. Unfractured cores resulted in higher recovery than all fractured ones. CGI in fractured cores resulted in very poor recovery but WAG and SWAG injections improved the oil recovery by at least 25 percent over CGI. This is because of the better conformance provided by the injected water, which decreased CO2 cycling through the fracture. CO2 injection in layered permeability arrangements showed significant decrease in oil recovery (up to 40 percent) compared to the homogenous case. For all injection modes during the layered permeability arrangements, the best oil recovery was obtained when the flow barrier is in the middle of the core. When the permeability was arranged in sequence, each injection mode showed different preference to the permeability arrangements. The WAG ratio study in the homogenous case showed that a 1:2 ratio had the highest oil recovery, but the optimum ratio was 1:1 based on the amount of injected CO2. In contrast, layered permeability arrangements showed different WAG ratio preference depending on the location of the flow barrier.Item Investigation of CO₂ seeps at the crystal geyser site using numerical modeling with geochemistry(2012-05) Kim, Eric Youngwoong; Srinivasan, Sanjay; EICHHUBL, PETERCarbon Dioxide (CO₂) sequestration requires that the injected CO₂ be permanently trapped in the subsurface and not leak from the target location. To accomplish this, it is important to understand the main mechanisms associated with CO₂ flow and transport in the subsurface once CO₂ is injected. In this work CO₂ seeps at the Crystal Geyser site were studied using modeling and simulation to determine how CO₂ geochemically reacts with formation brines and how these interactions impact the migration of CO₂. Furthermore different scenarios for CO₂ migration and seepage along the Grand Wash fault are studied and the possible outcomes for these different scenarios are documented. The GEM (Generalized Equation-of-State Model) from CMG Ltd. was used to perform the simulation studies. A 2-D model was built without geochemical reactions to mainly study the mechanism associated with dissolution of CO₂ gas. The process of CO₂ release from the brine as the fluid mixture flows up along the fault was modeled. Then, 3-D models with geochemical reactions were built for CO₂ migration corresponding to two different sources of CO₂ - deep crustal ₂ and CO₂-dissolved in groundwater. In both these cases, CO₂ reacted with the aqueous components and minerals of the formation and caused carbonate mineralization. In the case of deep crustal CO₂ source, there were vertical patterns of calcite mineralization simulated along the fault that indicated that calcite mineralization might be localized to isolated vertical flow paths due to vertical channeling of CO₂ from the crust. In the case of CO₂-dissolved groundwater flowing along the sandstone layers, calcite mineralization is spread over the entire fault surface. In this case, the groundwater flow is interrupted by the fault and there is vertical flow along the fault until a permeable sandstone layer is encountered on the other side of the fault. This vertical migration of CO₂-saturated brine causes a release in pressure and subsequent ex-solution of CO₂. As a result, modeling allowed us to establish difference in surface expression of CO₂ leakage due to two different CO₂ migrations scenarios along the fault and helped develop a scheme for selecting appropriate model for CO₂ leakage based on surface observation of travertine mounds. A key observation at the Crystal Geyser site is the lateral migration of CO₂ seep sites over time. These migrations have been confirmed by isotope studies. In this modeling study, the mechanism for migration of seep sites was studied. A model for permeability reduction due to precipitation of calcite was developed. It is shown using percolation calculations that flow re-routing due to permeability alterations can result in lateral migration of CO₂ seeps at rates comparable to those established by isotope dating.Item Investigations on the use of main group metal complexes of salen ligands as catalysts for the copolymerization of CO2 and epoxides(Texas A&M University, 2005-08-29) Billodeaux, Damon RayCurrent industrial processes for the production of polycarbonates, a thermoplastic valued for commercial applications, leave much to be desired from an environmental viewpoint. Research into alternative methods for production of polycarbonates has focused on the copolymerization of carbon dioxide and epoxides for the benefits of eliminating phosgene as a reagent, and for the economic impact of incorporating CO2 as a low cost C1 feedstock. Early work in this field focused on the use of zinc-derived catalysts, but recent studies indicate that chromium complexes of the salen (N,N-bis-(salicylidene)-1,2-ethylene diimine) family of ligands are far superior to the zinc complexes in terms of reactivity and diminishing the formation of unwanted byproducts. Concomitant to the studies of chromium salen complexes, investigations of main-group salen metal complexes were carried out. Aluminum complexes were able to produce polycarbonate in the presence of tetrabutyl ammonium salts and neutral Lewis bases. Gallium complexes were essentially inactive for generating any product. Tin(IV) complexes were active for the production of polyether, the result of homopolymerization of epoxide without CO2 insertion. Tin(II) complexes generated the monomeric cyclic carbonate product but no copolymer. An additional aspect of research relative to this field of study is the development of polymeric materials from several different epoxide monomers. The complex [hydrotris(3-phenyl-pyrazol-1-yl)borate]Cd(II) acetate was used to study the thermodynamics of the binding of a series of potential epoxide monomers to a metal center via 113Cd NMR. Activation of the epoxide by a metal center was found to not play a significant role in the ability of the complex to be subsequently ring-opened for polymerization. A final relevant area of study involved the synthesis of cadmium analogues of Fe/Zn double metal cyanide (DMC) complexes. Heterogeneous DMCs are well known in patent literature as excellent catalysts for the production of polycarbonates and cyclic carbonates from CO2 and epoxides. Previous studies on homogeneous Fe/Zn DMCs have only provided cyclic carbonate. Cd analogues of these species provide a convenient NMR handle for studies on the activity of the metal centers in presence of an epoxide and by changes to the DMC structure.Item Observations of buoyant plumes in countercurrent displacement(2011-12) Hernandez, Angelica Maria; Bryant, Steven L.; Sepehrnoori, KamyLeakage of stored bulk phase CO₂ is of particular risk to sequestration in deep saline aquifers due to the fact that when injected into typical saline aquifers, the CO₂ rich gas phase has lesser density than the aqueous phase resulting in buoyancy driven flow of the fluids. As the CO₂ migrates upward, the security of its storage depends upon the trapping mechanisms that counteract the migration. While there are a variety of trapping mechanisms the mechanism serving as motivation for this research is local capillary trapping. Local capillary trapping occurs during buoyancy-driven migration of bulk phase CO₂ within a saline aquifer (Saadatpoor, 2009). When the rising CO₂ plume encounters a region where capillary entry pressure is locally larger than average, CO₂ accumulates beneath the region. While research is continued by means of numerical simulation, research at the bench scale is needed to validate the conclusions made from simulation work. Presented is the development of a bench scale experiment whose objective is to assess local capillary trapping. The initial step in accomplishing this objective is to understand the fluid dynamics of CO₂ and brine in a saline aquifer which is categorized as two phase immiscible buoyancy driven displacement. Parameters influencing this displacement include density, viscosity, wettability and heterogeneity. A bench scale environment created to be analogous to CO₂ and brine in a saline aquifer is created in a quasi-two dimensional experimental apparatus, which allows for observation of plume migration at ambient conditions. A fluid pair analogous to supercritical CO₂ and brine is developed to mimic the density and viscosity relationship found at pressure and temperature typical of storage aquifers. The influences of viscosity ratio, density differences, porous medium wettability and heterogeneity are observed in series of experimental sequences. Three different fluid pairs with different viscosity ratios and density differences are used to assess density and viscosity influences. Porous media of varying grain size and wettability are used to assess the influence of heterogeneity and wettability. Results are qualitatively consistent with theoretical results and those from previous works.Item Potential for CO2 Sequestration and Enhanced Coalbed Methane Production, Blue Creek Field, NW Black Warrior Basin, Alabama(2011-02-22) He, TingCarbon dioxide (CO2) is a primary source of greenhouse gases. Injection of CO2 from power plants near coalbed reservoirs is a win-win method to reducing emissions of CO2 to the atmosphere. Limited studies have investigated CO2 sequestration and enhanced coalbed methane production in San Juan and Alberta basins, but reservoir modeling is needed to assess the potential of the Black Warrior basin. Alabama ranks 9th nationally in CO2 emissions from power plants; two electricity generation plants are adjacent to the Black Warrior coalbed methane fairway. This research project was a reservoir simulation study designed to evaluate the potential for CO2 sequestration and enhanced coalbed methane (ECBM) recovery in the Blue Creek Field of Black Warrior basin, Alabama. It considered the injection and production rate, the components of injected gas, coal dewatering, permeability anisotropy, various CO2 soak times, completion of multiple reservoir layers and pressure constraints at the injector and producer. The simulation study was based on a 5-spot well pattern 40-ac well spacing. Injection of 100 percent CO2 in coal seams resulted in average volumes of 0.57 Bcf of sequestered CO2 and average volumes of 0.2 Bcf of enhance methane production for the Mary Lee coal zone only, from an 80-acre 5-spot well pattern. For the entire Blue Creek field of the Black Warrior basin, if 100 percent CO2 is injected in the Pratt, Mary Lee and Black Creek coal zones, enhance methane resources recovered are estimated to be 0.3 Tcf, with a potential CO2sequestration capacity of 0.88 Tcf. The methane recovery factor is estimated to be 68.8 percent, if the three coal zones are completed but produced one by one. Approximately 700 wells may be needed in the field. For multi-layers completed wells, the permeability and pressure are important in determining the breakthrough time, methane produced and CO2 injected. Dewatering and soaking do not benefit the CO2 sequestration process but allow higher injection rates. Permeability anisotropy affects CO2 injection and enhanced methane recovery volumes of the field. I recommend a 5-spot pilot project with the maximum well BHP of 1,000 psi at the injector, minimum well BHP of 500 psi at the producer, maximum injection rate of 70 Mscf/D, and production rate of 35 Mscf/D. These technical results, with further economic evaluation, could generate significant projects for CO2 sequestration and enhance coalbed methane production in Blue Creek field, Black Warrior Basin, Alabama.Item Structural and mechanistic studies into the copolymerization of carbon dioxide and epoxides catalyzed by chromium salen complexes(Texas A&M University, 2006-08-16) Mackiewicz, Ryan MichaelThe ability to utilize cheaper starting materials in the synthesis of commercially important materials has been a goal of scientists since the advent of the chemical industry. The ideal situation would be one in which by combining the correct proportions of hydrogen, nitrogen, carbon and oxygen that virtually anything from simple sugars to complex polymers could be produced. Unfortunately, such processes are flights of fancy often reserved for movies and television shows. On a more realistic level, the utilization of simple molecules and a transition metal catalyst has been a process that industry has exploited for many years. The most easily identifiable process is that for polyolefin production, that employs homopolymerization of simple monomers such as ethylene and catalysts ranging from Ziegler-Natta to metallocene type catalysts. On a more difficult level copolymerization reactions require a delicate balance between two competing reactions and as a result these reactions have been much less successful. For over a decade now the Darensbourg Research Laboratories have focused on utilizing another simple molecule: carbon dioxide. Carbon dioxide is a cheap, inert, nontoxic starting material that appears to be an ideal monomer. Although simplistic, CO2 is also very stable and its utilization in polymerization reactions have proven to be quite complex. In order for us to facilitate these reactions we employ both a transition metal catalyst and a comonomer. Epoxides act as an effective comonomer because the thermodynamic energy gained from breaking the strained three membered epoxide ring overcomes the stability of CO2 and allows the copolymerization reaction to occur. We have demonstrated a great deal of success with this process, most of which will be mentioned throughout this report. The majority of this dissertation will detail our use of salen complexes to optimize this copolymerization process, in order to further the use of CO2 as a viable source of C1 feedstock. Herein, I will illustrate how we have obtained more than a 100 fold increase in the rate of polymer formation as well as detailed mechanistic data that will provide a basis for future catalyst design studies.Item Surfactant characterization to improve water recovery in shale gas reservoirs(2013-12) Huynh, Uyen T.; Nguyen, Quoc P.; DiCarlo, David Anthony, 1969-After a fracturing job in a shale reservoir, only a fraction of injected water is recovered. Water is trapped inside the reservoir and reduces the relative permeability of gas. By reducing the interfacial tension between water and hydrocarbon, more water can be recovered thus increasing overall gas production. By adding surfactants into the fracturing fluid, the IFT can be reduced and will help mobilize trapped water. From previous research, two types of surfactant have been identified to be CO₂ soluble. These are the ethoxylated tallow amine and ethoxylated coco amine with varying ethoxylate length. Experiments were performed to test the solubility of these surfactants in water, observe how they change the interaction between HC and water, and measure the IFT reduction between HC and water. Surfactants with more than 10 EO groups were soluble at all salinities, temperature and pH. They also form a non-typical water-in-oil emulsion at all salinities. The surfactants, Ethomeen T/25, T/30, C/15, and C/25 were used in the IFT measurements. They showed interesting trends that exhibit their hydrophilic/hydrophobic nature. These surfactants reduce the IFT between pentane and water to approximately 5 mN/m. The results show that these surfactants do reduce the IFT between water and hydrocarbon, but not as well as conventional EOR surfactants. They do have other added benefits such as being CO₂ soluble, form water in oil emulsions, and tolerant to high temperature and salinity.Item Synthesis and Characterization of Iso-Reticular Metal-Organic Frameworks and Their Applications for Gas Separations(2011-10-21) Yoo, YeonshickNanoporous metal-organic frameworks (MOFs) have attracted tremendous interest due to their potential applications in gas-storage, gas separation, gas sensing, and catalysis. MOFs consist of metal-oxygen polyhedera interconnected with a variety of organic linker molecules, resulting in tailored nanoporous materials. With a judicious choice of organic linker groups, it is possible to fine-tune size, shape, and chemical functionality of the cavities and the internal surfaces. This unique structural feature offers unprecedented opportunities in small-molecule separations as well as chiral separations and catalysis. Prototypical iso-reticular metal-organic frameworks (IRMOFs) have been extensively studied among MOFs due to the simplicity of their synthesis and the variety of their potential applications. IRMOFs are a specific series of metal-organic frameworks developed by Yaghi and his coworkers. All IRMOFs are composed of oxygen-centered Zn4O tetrahedra interconnected with dicarboxylate linkers, forming a cubic type three dimensional (3D) porous network with high surface area. Despite a great deal of research in the synthesis and characterization of MOFs, there have been relatively few reports on the development of their applications, such as the fabrication of MOF thin films and membranes for gas separations. This is mainly due to the challenges associated with relatively difficult heterogeneous nucleation (seeding) and growth of MOFs on supports, and crack formation compared to their counterparts. Thin films and membranes of MOFs have great potentials for applications in membranebased gas separations, reactors, chemical sensors, and nonlinear optical devices. In this dissertation, the fabrication of IRMOF-1 membrane using a novel seeding method and its gas diffusion properties has been demonstrated. Introduction of the new seeding method for MOFs using microwaves resulted in well inter-grown IRMOF membranes showing Knudsen type transport of small gases through its pore. The heteroepitaxial growth of one IRMOF on another produced multi-layered IRMOF membranes. In addition, postsynthetic modification (PSM) of IRMOFs created functionalized membranes with enhanced stability against water as well as reduced crack formation during membrane fabrication. Lastly, hierarchical IRMOFs with improved CO2 adsorption properties were synthesized via PSM with cyanuric chloride.Item System Design and Optimization of CO2 Storage in Deep Saline Aquifers(2012-02-14) Shamshiri, HosseinOptimization of waterflooding sweep efficiency has been widely applied in reservoir engineering to improve hydrocarbon recovery while delaying water breakthrough and minimizing the bypassed oil in reservoirs. We develop a new framework to optimize flooding sweep efficiency in geologic formations with heterogeneous properties and demonstrate its application to waterflooding and geological CO2 sequestration problems. The new method focuses on equalizing and delaying (under constant total injected volume) the breakthrough time of the injected fluid at production wells. For application to CO2 sequestration where producers may not be present, we introduce the concept of pseudo production wells that have insignificant production rates (with negligible effect on the overall flow regime) for quantification of hypothetical breakthrough curves that can be used for optimization purpose. We apply the new method to waterflooding and CO2 sequestration optimization using two heterogeneous reservoir models. We show that in water flooding experiments, the proposed method improves the sweep efficiency by delaying the field breakthrough and equalizing breakthrough times in all production wells. In this case, the optimization results in increased oil recovery and decreased water production. We apply a modified version of the proposed algorithm to geologic CO2 sequestration problems to maximize the storage capacity of aquifers by enhancing the residual and dissolution trapping. The results from applying the proposed approach to optimization of geologic CO2 storage problems illustrate the effectiveness of the algorithm in improving residual and solubility trapping by increasing the contact between available fresh brine and the injected CO2 plume through a more uniform distribution of CO2 in the aquifer.