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This thesis examines the prospect of structure H (sH) hydrate to be exploited for methane storage. The methane content in the hydrate, hydrate kinetics and conversion rates are areas of particular importance. Experiments and theory are employed at the macroscopic and molecular levels to study the relevant phenomena. sH hydrate was successfully synthesized from ice particles with full conversion achieved within a day when thermal ramping above the ice melting point was applied. It was found that a polar guest (tert-butyl methyl ether / TBME) wets ice more extensively compared to two hydrophobic guests (neo-hexane / NH and methyl-cyclohexane / MCH). TBME also has much higher solubility in water. Consequently, the system with TBME was found to exhibit the highest initial hydrate formation rate from ice particles or in water in a well stirred vessel. However, the rate with the hydrophobic guests was the fastest when the temperature exceeded the ice point. Thus, the applied temperature ramping compensated the slow kinetics below the ice point for the hydrophobic guests and allowed faster overall conversion than the polar guest. Structure, cage occupancy, composition and methane content in the hydrate were also determined by employing different techniques and the results were found to be consistent. It was found that the methane content in structure H hydrate with TBME was the smallest (103-125 v/v) whereas that with NH was 130-139 (v/v) and that with MCH was 132-142 (v/v). The methane content in structure II hydrate by using propane (C₃H₈) and tetrahydrofuran (THF) as the large guest molecule were also estimated. Optimal methane content was found at approximately 100 (v/v) for both C₃H₈ and THF systems with the large guest concentrations at 1% for C₃H₈ (10°C) and 1% for THF (room temperature). The gas content is of course lower than that for structure I hydrate (170 v/v) but one should consider the fact that the hydrate formation conditions are much lower (less than 1 MPa). Finally, MD simulations revealed for the first time the formation of defects in the cavities for the TBME/methane/water (sH hydrate) system which may affect hydrate stability and kinetics.

No description available.

This thesis examines the prospect of structure H (sH) hydrate to be exploited for methane storage. The methane content in the hydrate, hydrate kinetics and conversion rates are areas of particular importance. Experiments and theory are employed at the macroscopic and molecular levels to study the relevant phenomena. sH hydrate was successfully synthesized from ice particles with full conversion achieved within a day when thermal ramping above the ice melting point was applied. It was found that a polar guest (tert-butyl methyl ether / TBME) wets ice more extensively compared to two hydrophobic guests (neo-hexane / NH and methyl-cyclohexane / MCH). TBME also has much higher solubility in water. Consequently, the system with TBME was found to exhibit the highest initial hydrate formation rate from ice particles or in water in a well stirred vessel. However, the rate with the hydrophobic guests was the fastest when the temperature exceeded the ice point. Thus, the applied temperature ramping compensated the slow kinetics below the ice point for the hydrophobic guests and allowed faster overall conversion than the polar guest. Structure, cage occupancy, composition and methane content in the hydrate were also determined by employing different techniques and the results were found to be consistent. It was found that the methane content in structure H hydrate with TBME was the smallest (103-125 v/v) whereas that with NH was 130-139 (v/v) and that with MCH was 132-142 (v/v). The methane content in structure II hydrate by using propane (C₃H₈) and tetrahydrofuran (THF) as the large guest molecule were also estimated. Optimal methane content was found at approximately 100 (v/v) for both C₃H₈ and THF systems with the large guest concentrations at 1% for C₃H₈ (10°C) and 1% for THF (room temperature). The gas content is of course lower than that for structure I hydrate (170 v/v) but one should consider the fact that the hydrate formation conditions are much lower (less than 1 MPa). Finally, MD simulations revealed for the first time the formation of defects in the cavities for the TBME/methane/water (sH hydrate) system which may affect hydrate stability and kinetics.

This thesis examines the prospect of structure H (sH) hydrate to be exploited for methane storage. The methane content in the hydrate, hydrate kinetics and conversion rates are areas of particular importance. Experiments and theory are employed at the macroscopic and molecular levels to study the relevant phenomena. sH hydrate was successfully synthesized from ice particles with full conversion achieved within a day when thermal ramping above the ice melting point was applied. It was found that a polar guest (tert-butyl methyl ether / TBME) wets ice more extensively compared to two hydrophobic guests (neo-hexane / NH and methyl-cyclohexane / MCH). TBME also has much higher solubility in water. Consequently, the system with TBME was found to exhibit the highest initial hydrate formation rate from ice particles or in water in a well stirred vessel. However, the rate with the hydrophobic guests was the fastest when the temperature exceeded the ice point. Thus, the applied temperature ramping compensated the slow kinetics below the ice point for the hydrophobic guests and allowed faster overall conversion than the polar guest. Structure, cage occupancy, composition and methane content in the hydrate were also determined by employing different techniques and the results were found to be consistent. It was found that the methane content in structure H hydrate with TBME was the smallest (103-125 v/v) whereas that with NH was 130-139 (v/v) and that with MCH was 132-142 (v/v). The methane content in structure II hydrate by using propane (C₃H₈) and tetrahydrofuran (THF) as the large guest molecule were also estimated. Optimal methane content was found at approximately 100 (v/v) for both C₃H₈ and THF systems with the large guest concentrations at 1% for C₃H₈ (10°C) and 1% for THF (room temperature). The gas content is of course lower than that for structure I hydrate (170 v/v) but one should consider the fact that the hydrate formation conditions are much lower (less than 1 MPa). Finally, MD simulations revealed for the first time the formation of defects in the cavities for the TBME/methane/water (sH hydrate) system which may affect hydrate stability and kinetics. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

In the screening and concept selection stages of gas storage projects, many estimates are required to value competing projects and development concepts. These estimates are important because they influence which projects are selected and which concept proceeds into detailed engineering. In most cases, there is uncertainty in all of the estimates. As a result, operators are faced with the complex problem of determining the optimal design. A systematic uncertainty analysis can help operators solve this problem and make better decisions. Ideally, the uncertainty analysis is comprehensive and includes all uncertain variables, and simultaneously accounts for reservoir behavior, facility options, and economic objectives. This thesis proposes and demonstrates a workflow and an integrated optimization model for uncertainty analysis in gas storage. The optimization model is fast-solving and eliminates most constraints on the scope of the uncertainty analysis. Using this or similar workflows and models should facilitate analysis and communication of results within the project team and with other stakeholders. / text

Porous organic polymers (POPs) received great attention in recent years because of their novel properties such as permanent porosity, adjustable chemical nature, and remarkable thermal and chemical stability. These attractive features make POPs very promising candidates for use in gas separation and storage applications. In particular, CO2 capture and separation from gas mixtures by POPs have been intensively investigated in recent years because of the greenhouse nature of CO2, which is considered a leading cause for global warming. CO2 chemical absorption by amine solutions from the flue gas of coal-fired power plants suffers from several challenges such as high-energy consumption in desorption, chemical instability, volatility, and corrosive nature, limiting the widespread use of this technology. To mitigate these limitations, new adsorbents with improved CO2 capturing properties need to be designed, synthesized, and tested. Alternatively, the use of cleaner fuels such as methane can reduce CO2 release or completely eliminates it in the case of hydrogen. However, the on-board storage of methane and hydrogen for automotive applications remains a great challenge. With these considerations in mind, our research goals in this dissertation focus on the systematic design and synthesis of N-rich POPs and their use in small gas (H2 and CH4) storage as well as selective CO2 capture from gas mixtures. In particular, we have studied the effect of integrating pyrene and triazine building units into benzimidazole-linked polymers (BILPs) and covalent organic frameworks (COFs) on gas storage and separation. We have found that pyrene-based BILPs exhibit remarkable selective CO2 capturing capacities under industrial settings (VAS, PSA). However the methane and hydrogen storage capacities of BILPs were found to be only modest especially at high pressure due to their moderate surface area and pore volume. We addressed these limitations by the synthesis of a highly porous imine-linked COF (ILCOF-1), which has very high surface area and improved hydrogen and methane uptakes when compared to BILPs. We have demonstrated that the use of pyrene in BILPs and COFs can direct frameworks growth through - stacking and improve porosity and pore volume whereas the use of triazine is instrumental in improving the binding affinity of the frameworks towards CO2.

The synthesis of highly porous organic polymers with predefined porosity has attracted considerable attention due to their potential in a wide range of applications. Of particular interest in porous organic polymers is their potential use in automotive applications as well as separation processes whereby advancements could result in a reduction in carbon dioxide emissions and the production of natural gas in a more economically friendly manner. Along these pursuits, seven borazine-linked polymers (BLPs) have been synthesized through the introduction of p-phenylenediamine, 1,3,5-tris-(4-aminophenyl)benzene, benzidine, or tetra-(4-aminophenyl)methane with boron tribromide or boron trichloride followed by the thermolysis reaction of the resulting in situ adduct. All resulting polymers exist as amorphous polymers whose chemical connectivity was confirmed through FT-IR, solid state 11B and 13C NMR, and elemental analysis while thermogravimetric analysis reveals moderate thermal stabilities up to about 200°C. To assess their textural properties, all BLPs were subjected to nitrogen sorption experiments at 77 K. In all cases, the polymers possess high surface areas with chlorinated BLPs exhibiting higher values than their brominated analogues (1174-1569 m2/g versus 503-849 m2/g, respectively). Gas storage capabilities of BLPs for hydrogen, carbon dioxide, and methane were investigated as well. BLPs possess good hydrogen uptakes (0.68-1.75 wt% at 77 K) and zero-coverage isosteric heat of adsorption, Qst, (7.06-7.65 kJ/mol) as calculated by the virial method. The uptakes and heats of adsorption for carbon dioxide (51-141 mg/g at 273 K with Qst: 22.2-31.7 kJ/mol) are also attractive. BLPs do not, however, appear to exhibit significant methane storage capabilities (1.9-15.2 mg/g at 273 K with Qst: 17.1-21.7 kJ/mol). In light of such a difference in storage between carbon dioxide and methane, CO2/CH4 selectivity was calculated for each polymer according to the ideal adsorbed solution theory (IAST). Three of the polymers, BLP-1(Br), BLP-2(Br), and BLP-10(Cl), possess excellent selectivity capabilities over 20 even at low pressures for all molar ratios. Additionally, these selectivity values increase further with increasing pressure. Selectivity was also investigated for benzimidazole-linked polymers. In such systems, the CO2/N2 selectivity values reach 73 at low pressure and exhibit an increasing trend with increasing pressure.

Improving methods of hydrocarbon production and developing new techniques for the creation of natural gas storage facilities are critically important for the petroleum industry. This dissertation focuses on two key topics: (1) mechanisms of sand production from petroleum reservoirs and (2) mechanical characterization of caverns created in carbonate rock formations for natural gas storage. Sand production is the migration of solid particles together with the hydrocarbons when extracted from petroleum reservoirs. It usually occurs from wells in sandstone formations that fail in response to stress changes caused by hydrocarbon withdrawal. Sand production is generally undesirable since it causes a variety of problems ranging from significant safety risks during high-rate gas production, to the erosion of downhole equipment and surface facilities. It is widely accepted that a better understanding of the mechanics of poorly-consolidated formations is required to manage sand production; which, in turn, enables the cost effective production of gas and oil resources. In this work, a series of large-scale laboratory experiments was conducted in fully saturated, cohesionless sand layers to model the behavior of a petroleum reservoir near a wellbore. We directly observed several key characteristics of the sand production phenomenon including the formations of a stable cavity around the wellbore and a sub-radial flow channel at the upper surface of the tested layer. The flow channel is a first-order feature that appears to be a major part of the sand production mechanism. The channel cross section is orders of magnitude larger than the particle size, and once formed, the channel becomes the dominant conduit for fluid flow and particle transport. The flow channel developed in all of our experiments, and in all experiments, sand production continued from the developing channel after the cavity around the borehole stabilized. Our laboratory results constitute a well constrained data set that can be used to test and calibrate numerical models employed by the petroleum industry for predicting the sand production phenomenon. Although important for practical applications, real field cases are typically much less constrained. We used scaling considerations to develop a simple analytical model, constrained by our experimental results. We also simulated the behavior of a sand layer around a wellbore using two- and three-dimensional discrete element methods. It appears that the main sand production features observed in the laboratory experiments, can indeed be reproduced by means of discrete element modeling. Numerical results indicate that the cavity surface of repose is a key factor in the sand production mechanism. In particular, the sand particles on this surface are not significantly constrained. This lack of confinement reduces the flow velocity required to remove a particle, by many orders of magnitude. Also, the mechanism of channel development in the upper fraction of the sample can be attributed to subsidence of the formation due to lateral extension when an unconstrained cavity slope appears near the wellbore. This is substantiated by the erosion process and continued production of particles from the flow channel. The notion of the existence of this surface channel has the potential to scale up to natural reservoirs and can give insights into real-world sand production issues. It indicates a mechanism explaining why the production of particles does not cease in many petroleum reservoirs. Although the radial character of the fluid flow eventually stops sand production from the cavity near the wellbore, the production of particles still may continue from the propagating surface (interface) flow channel. The second topic of the thesis addresses factors affecting the geometry and, hence, the mechanical stability of caverns excavated in carbonate rock formations for natural gas storage. Storage facilities are required to store gas when supply exceeds demand during the winter months. In many places (such as New England or the Great Lakes region) where no salt domes are available to create gas storage caverns, it is possible to create cavities in limestone employing the acid injection method. In this method, carbonate rock is dissolved, while CO₂ and calcium chloride brine appear as products of the carbonate dissolution reactions. Driven by the density difference, CO₂ rises towards the ceiling whereas the brine sinks to the bottom of the cavern. A zone of mixed CO₂ , acid, and brine forms near the source of acid injection, whereas the brine sinks to the bottom of the cavern. Characterization of the cavern shape is required to understand stress changes during the cavity excavation, which can destabilize the cavern. It is also important to determine the location of the mixture-brine interface to select the place of acid injection. In this work, we propose to characterize the geometry of the cavern and the location of the mixture-brine interface by generating pressure waves in a pipe extending into the cavern, and measuring the reflected waves at various locations in another adjacent pipe. Conventional governing equations describe fluid transients in pipes loaded only by internal pressure (such as in the water hammer effect). To model the pressure wave propagation for realistic geometries, we derived new governing equations for pressure transients in pipes subjected to changes in both internal and external (confining) pressures. This is important because the internal pressure (used in the measurement) is changing in response to the perturbation of the external pressure when the pipe is contained in the cavern filled with fluids. If the pressure in the cavern is perturbed, the perturbation creates an internal pressure wave in the submerged pipe that has a signature of the cavern geometry. We showed that the classic equations are included in our formulation as a particular case, but they have limited validity for some practically important combinations of the controlling parameters. We linearized the governing equations and formulated appropriate boundary and initial conditions. Using a finite element method, we solved the obtained boundary value problem for a system of pipes and a cavern filled with various characteristic fluids such as aqueous acid, calcium chloride brine, and supercritical CO₂ . We found that the pressure waves of moderate amplitudes would create measurable pressure pulses in the submerged pipe. Furthermore, we determined the wavelengths required for resolving the cavern diameter from the pressure history. Our results suggest that the pressure transients technique can indeed be used for characterizing the geometry of gas storage caverns and locations of fluid interfaces in the acid injection method.