Thesis (Ph. D.)--Johns Hopkins University, 1923. / Cover title. Vita. Bibliography: p. 21-22.

The aim of this study was to investigate the dynamic collapse of composite shells in a constant external pressure water environment that is representative of a naval underwater structure. Laminated carbon/epoxy composite shells with diameters of 1.735 in., wall thickness of 0.041 in, length-to-diameter ratios ranging for 2.8 to 12 and [55/-55/(90)3/-55/55] layup were collapsed in a custom pressure testing facility that provided a constant pressure water environment. Buckling was sudden, dynamic, led to failure and fragmentation of the shells; the whole event lasted only a couple of ms. The dynamic collapse of the shells was recorded using high-speed digital imaging and dynamic pressure sensors synchronized with the camera were used to monitor the emanating pressure waves. All shells buckled in mode 2 at pressure levels predicted by models adopted. Collapse led to a localization zone in the central section of the shells, approximately spanning on a 4D length for the longer ones, and shorter for the shorter shells. A single axial crack developed in the collapsing section, which propagated 2 to 4 diameters depending on the length of the specimen. The axial crack was located on the extrados for long shells, and on the intrados for shorter ones. Helical cracks initiated from the tips of the axial crack, propagated outwards, and were responsible for the collapse and fragmentation of the two outer sections. The receding walls of the central localizing zone caused a dynamic drop in pressure that lasted until the inward motion was arrested by contact. This was followed by a sharp, short duration positive pressure pulse associated with an outward expansion wave. The pressure pulse varied to some degree around the circumference with the highest peak occurring opposite the initial crack. The final result of such dynamic events was catastrophic failure and fragmentation of the shell into small shreds. / text

Wave dissipation was previously investigated intensively in the frequency domain, in which the dissipation of waves is described as attenuation of pressure pulse decay with respect to the frequency or harmonics. In this thesis, wave dissipation, including decay of pressure pulse, peak of wave intensity and wave energy, is investigated in the time domain using wave intensity analysis (WIA). Wave intensity analysis benefits to this research in several aspects including: 1) WIA allows for wave dissipation investigated in the time domain; 2) WIA does not make any assumptions about the tube's wall non-linearity and the analysis takes into account the effects of the vessel's wall viscoelastic properties, convective, frictional effects and fluid viscosity; 3) WIA offers a technique (separation) to study wave dissipation in one direction whilst taking into account the effect of reflections from the opposite direction; 4) The physical meaning of wave intensity provides a convenient method to study the dissipation of energy carried by the waves along flexible tubes. In this research, it is found that the degree of dissipation in flexible tube were not only affected by the mechanical properties of the wall property and viscosity of liquid but also by the other factors including initial pressure and pumping speed of piston as well as direction of wave in relation to direction of flow. Also an new technique to separate waves into forward and backward directions only using diameter and velocity might potentially be used to separate the waves in both directions non-invasively based on the non-invasive measurement of diameter (wall movement) available.

The steady flow method (SFM), most commonly used for permeability measurement in the laboratory, is not applicable for tight rocks, higher rank coals and coals under highly stressed condition because of the difficulty in measuring steady-state gas flowrates resulting from the tight rock structure of. However, accurate estimation of permeability of highly stressed coals is pivotal in coalbed methane (CBM) operations in order to precisely and effectively model and project long-term gas production. A fast and accurate permeability measurement technique is, therefore, required to investigate gas flow behavior of CBM reservoirs. The pulse-decay method (PDM) of permeability measurement is believed to be better suited for low-permeability rocks. In this study, application of the currently used pulse-decay laboratory permeability measurement techniques for highly stressed coals were evaluated. Considering the limitations of these techniques in permeability measurement of unconventional gas reservoirs, such as coal and gas shales, the conventional PDM was optimized by adjusting the experimental apparatus and procedures. Furthermore, the applicability of an optimized PDM was verified numerically and experimentally. This dissertation is composed of five chapters. To complete the research objectives as discussed above, it is necessary to have a profound understanding of the basic theories, such as, gas storage mechanism, gas migration, and permeability evolution during gas depletion in coalbed reservoirs. In Chapter 1, a brief discussion regarding the basic knowledge of reservoir properties and transport mechanisms is presented. The chapter also provides the appropriate background and rationale for the theoretical and experimental work conducted in this study. Chapter 2 presents the transient pressure-decay technique in permeability measurement of highly stressed coals and verifies the validity of Brace et al.’s solution (1968) by comparing it with Dicker and Smits’s solution (1988) and Cui et al.’s solution. The differences between these three solutions are discussed in detail. Based on the established permeability trends from these different solutions, a persuasive suggestion is presented for selection of the best alternative when testing coal permeability. Furthermore, permeability is regarded as a coupled parameter, resulting from the combined effects of mechanical compression and “matrix shrinkage” caused by desorption of gas. To isolate the role of gas desorption from the coupled result, a series of experiments were carried out under constant effective stress condition and a stress-dependent permeability trend was established. Chapter 3 proposes an optimized experimental design in order to improve the accuracy of the calculated permeability for sorptive rocks. In order to verify the optimized design theoretically, a modified mathematical model is presented and describes the one-dimensional fluid flow in porous media by a partial differential equation. The numerical solutions of the model are presented graphically to evaluate the fluid flow behavior in porous media. Finally, the validity of Brace et al.’s solution when testing sorptive rocks, without the need of consideration on the compressive storage and sorption effect, is elucidated. Chapter 4 demonstrates the efficiency and applicability of the optimized PDM through its direct application to experimental work designed to establish the permeability trend under best replicated in situ conditions. In this chapter, CO2 was used as the test fluid to profile and characterize the pulse decay plots due to its higher affinity towards coal than methane, and then establish the stress-dependent-permeability trend for highly-stressed CBM reservoirs. In this chapter, Brace et al.’s solution was also verified by comparing the laboratory data and computer simulated results obtained from the optimized mathematical model proposed in Chapter 3. The experimental work demonstrates that the optimized technique can be used for permeability tests of sorptive rocks without the need to carry out additional experimental work required to measure rock porosities and sorption isotherms. Finally, a summary and future research perspectives are presented in Chapter 5.

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The Pressure Impulse test-rig uses the principal energetic advantages of displacementcontrolled systems versus valve-controlled systems. The use of digital-control technology enables a high dynamic in the pressure curve, according to the requirements of ISO6605. Accumulators, along with inertia, make energy recovery possible, as well as, enabling the compression energy to be re-used. As a result of this, there is a drastic reduction in operating costs. A simulation of the system before starting the project allows the development risks to be calculated and the physically achievable performance limits to be shown.

Student Number :9900127Y - MSc (Eng) dissertation - Faculty of Engineering and the Built Environment / Arterial pulse wave analysis studies the wave shape of the blood pressure pulse. The pulse wave provides more information than the extreme systolic and dia- stolic pressures, measured with a cuff sphygmomanometer. The aim of the research is to investigate the design issues in a pulse wave analysis system, and to compare these to a commercially available system. The system was compared and validated by measuring the pulse wave at the radial artery (wrist) using the non-invasive technique of arterial tonometry. The design conformed to the IEC-601 safety standard to ensure patient safety. The data was compared against the data from the commercial system and analysis was performed in the time and frequency domain. The performance of the design suggests that, in some respects, the design was comparable to the commer- cial system, however, a number of performance characteristics fell short of the commercial system. Suggestions have been made to address these problems in further research.

The Intergovernmental Panel on Climate Change (2001) reports that increased anthropogenic greenhouse gas (GHG) emissions, of which carbon dioxide (CO2) is the main component, have caused the Earths temperature to rise. Therefore, it is necessary to find ways to reduce GHG emissions and to deal with the emissions that continue to be produced. Carbon capture and storage (CCS) is one method that is being considered to deal with GHG emissions, specifically CO2 emissions. The basic idea behind CCS is that CO2 is captured from a point source, such as a power plant, and is then transported to a storage site (e.g., an oil or gas reservoir), where it is subsequently stored. The International Energy Agency Greenhouse Gas Programme (IEA GHG) began a CO2 geological sequestration pilot project in 2000 in Weyburn, Saskatchewan as part of an enhanced oil recovery project operatedby Cenovus (formerly EnCana) in the Weyburn Field (White et al. 2004). The research presented in this thesis evaluates the sealing potential of the Lea Park Formation in the Weyburn Field by determining its permeability and CO2 breakthrough pressure. In this context, breakthrough pressure describes the differential pressure between a wetting phase (e.g., formation brine) and a non-wetting phase (e.g., CO2) that is sufficient to enable the non-wetting phase to form a connected flow system across a given volume of porous medium (e.g., a rock sample). A new system for measuring the permeability and CO2 breakthrough pressure of shales was developed in this research. The development effort included extensive trouble-shooting and, ultimately, the development of sample preparation and testing procedures. The new system was used to conduct permeability and CO2 breakthrough pressure tests on shale samples from the Lea Park Formation (i.e., Lea Park shale) and the Colorado Group (i.e., Colorado shale). Permeability results for samples from the Lea Park shale ranged from 14 to 35 nd (1410-21 to 3510-21 m2), and between eight and 46 nd (810-21 to 4610-21 m2) for the Colorado shale. A CO2 breakthrough pressure for the Lea Park shale was determined to be 0.02 MPa, while values of 0.02 and 2.7 MPa were measured for the Colorado shale. The CO2 breakthrough pressure test results indicate that the Lea Park shale will not withstand large pressures before allowing CO2 to flow through it. However, the permeabilities are extremely low; hence the rate of flow would be low. In other words, the low permeability of the Lea Park shale will be the controlling factor in terms of the rate of potential CO2 leakage through it. Calculations based on the properties measured in this research suggest that the time required for CO2 to flow from the base to the top of the Lea Park Formation would be on the order of ten thousand years. Based on diffusion coefficients published for other shales, calculations suggest that CO2 leakage via chemical diffusion would be several times slower leakage via hydraulically-driven flow.

The Intergovernmental Panel on Climate Change (2001) reports that increased anthropogenic greenhouse gas (GHG) emissions, of which carbon dioxide (CO2) is the main component, have caused the Earths temperature to rise. Therefore, it is necessary to find ways to reduce GHG emissions and to deal with the emissions that continue to be produced. Carbon capture and storage (CCS) is one method that is being considered to deal with GHG emissions, specifically CO2 emissions. The basic idea behind CCS is that CO2 is captured from a point source, such as a power plant, and is then transported to a storage site (e.g., an oil or gas reservoir), where it is subsequently stored. The International Energy Agency Greenhouse Gas Programme (IEA GHG) began a CO2 geological sequestration pilot project in 2000 in Weyburn, Saskatchewan as part of an enhanced oil recovery project operatedby Cenovus (formerly EnCana) in the Weyburn Field (White et al. 2004). The research presented in this thesis evaluates the sealing potential of the Lea Park Formation in the Weyburn Field by determining its permeability and CO2 breakthrough pressure. In this context, breakthrough pressure describes the differential pressure between a wetting phase (e.g., formation brine) and a non-wetting phase (e.g., CO2) that is sufficient to enable the non-wetting phase to form a connected flow system across a given volume of porous medium (e.g., a rock sample). A new system for measuring the permeability and CO2 breakthrough pressure of shales was developed in this research. The development effort included extensive trouble-shooting and, ultimately, the development of sample preparation and testing procedures. The new system was used to conduct permeability and CO2 breakthrough pressure tests on shale samples from the Lea Park Formation (i.e., Lea Park shale) and the Colorado Group (i.e., Colorado shale). Permeability results for samples from the Lea Park shale ranged from 14 to 35 nd (1410-21 to 3510-21 m2), and between eight and 46 nd (810-21 to 4610-21 m2) for the Colorado shale. A CO2 breakthrough pressure for the Lea Park shale was determined to be 0.02 MPa, while values of 0.02 and 2.7 MPa were measured for the Colorado shale. The CO2 breakthrough pressure test results indicate that the Lea Park shale will not withstand large pressures before allowing CO2 to flow through it. However, the permeabilities are extremely low; hence the rate of flow would be low. In other words, the low permeability of the Lea Park shale will be the controlling factor in terms of the rate of potential CO2 leakage through it. Calculations based on the properties measured in this research suggest that the time required for CO2 to flow from the base to the top of the Lea Park Formation would be on the order of ten thousand years. Based on diffusion coefficients published for other shales, calculations suggest that CO2 leakage via chemical diffusion would be several times slower leakage via hydraulically-driven flow.

The Pressure Impulse test-rig uses the principal energetic advantages of displacementcontrolled systems versus valve-controlled systems. The use of digital-control technology enables a high dynamic in the pressure curve, according to the requirements of ISO6605. Accumulators, along with inertia, make energy recovery possible, as well as, enabling the compression energy to be re-used. As a result of this, there is a drastic reduction in operating costs. A simulation of the system before starting the project allows the development risks to be calculated and the physically achievable performance limits to be shown.