Earth, Atmospheric, and Planetary Sciences - Master's degree
http://hdl.handle.net/1721.1/7656
Mon, 22 Jan 2018 20:00:45 GMT2018-01-22T20:00:45ZDetection and identification of converted modes and source independent converted phase imaging : Groningen, The Netherlands
http://hdl.handle.net/1721.1/111718
Detection and identification of converted modes and source independent converted phase imaging : Groningen, The Netherlands
AlJishi, Ali Fuad
Passive seismic monitoring waveform data collected at the Groningen gas field contain many interesting events besides direct P- and S-arrivals. We begin by summarizing the station distribution at Groningen over time and discuss the earthquake catalog. We examine the converted arrivals in order to understand their nature. A combination of move-out analysis, raytracing and finite-difference simulations has revealed that the data contain converted phases from two shallow interfaces. We discuss the possibility of using the Source Independent Converted Phase Imaging method to image the position in the subsurface where these phases have been generated. We examine the limitations of that method for imaging the position of shallow interfaces such as the ones at Groningen. The station spacing required to apply the imaging method to the data is shown to correlate well with the estimated Fresnel Zone dimension for the interface depth and data frequency. By using a kinematic version of the Source Independent Converted Phase Imaging Condition, we can map those interfaces. The positions of the interfaces are shown to correlate well with the positions inferred by other means.
Thesis: S.M., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2017.; Cataloged from PDF version of thesis. Page 196 blank.; Includes bibliographical references (pages 130-134).
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/1721.1/1117182017-01-01T00:00:00ZOn relative permeability : a new approach to two-phase fluid flow in porous media
http://hdl.handle.net/1721.1/111717
On relative permeability : a new approach to two-phase fluid flow in porous media
Albarghouty, Lubna Khalid
Being valid for single-phase flow, Darcy's law is adapted to two-phase flow through the standard approach of relative permeability, in which permeability, rather than being a unique property of the porous medium, becomes a joint property of the porous medium and each fluid phase. The goal of this study is to find a proper, alternate approach to relative permeability that can describe two-phase flow in porous media while maintaining sound physical concepts, specifically that of a unique permeability exclusive to the porous medium. The suggested approach uses the concept of an average viscosity of the two-phase fluid mixture. Viscosity, the only fluid-characterizing term in Darcy's law, should -at least partially- explain two-phase flow behavior by becoming the two-phase flow property that varies with the saturation ratio of the two fluid phases. Three common mathematical averages are tested as potential viscosity averages. Aspects of two-phase flow in pipes are then considered to see whether two-phase flow behavior in porous media can be attributed to the fluid mixture alone. Total flow rate of the two-phase fluid mixture is modeled by using the fluid mixture average viscosity in Darcy's law. Using two-phase flow data from Oak et al. (1990a, 1990b), the harmonic average weighted by the reduced fluid saturations represents the average viscosity of liquid-gas mixtures in steady-state flow in imbibition. Extracting flow rates of the individual phases from the total flow rate of the fluid mixture is the next, but crucial, step that determines whether the average viscosity approach can replace that of relative permeability in solving common reservoir engineering problems. Liquid-liquid flow in both drainage and imbibition, and liquid-gas flow in drainage are not represented by a simple viscosity average, which indicates the need for further study into more complex viscosity averages.
Thesis: S.M. in Geophysics, Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2017.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 115-116).
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/1721.1/1117172017-01-01T00:00:00ZOn the relationship between compressional wave velocity of saturated porous rocks and density : theory and application
http://hdl.handle.net/1721.1/108912
On the relationship between compressional wave velocity of saturated porous rocks and density : theory and application
AL Ismail, Marwah I
Understanding the velocity of the compressional waves travelling through rocks is essential for the purposes of applied geophysics in such areas as groundwater and hydrocarbon exploration. The wave velocity is defined theoretically by the Newton-Laplace equation, which relates the wave velocity, V, to the square root of the ratio of the rock's elastic modulus, M, and its density, [rho] (Bourvie et al., 1987). Therefore, the equation indicates that the velocity is inversely proportional to density. However, the in-situ field measurements and laboratory experiments of compressional wave velocity through different rocks show otherwise. In other words, the velocity is directly proportional to approximately the 4th power of density as stated by Gardner (Gardner et al., 1974). This thesis investigates the inconsistency between theory and observations regarding the relationship between velocity and density of saturated porous rocks. The inconsistency is clarified by deriving a new expression for the elastic modulus, M, using Wyllie's time average equation and the Newton-Laplace equation. The new derived expression of the elastic modulus, M, provides dependence of M on density to approximately the 9th power. In addition, Gardner's equation is modified to accurately obtain the velocity over the entire range of densities (from 1.00 g/cm³ to around 3.00 g/cm³) and porosity (from 0% to 100%). The end of this thesis is an application of the previous outcomes with real data sets, where the results validate the derived expression of the elastic modulus as well as the generalized form of Gardner's equation.
Thesis: S.M., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2017.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 97-98).
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/1721.1/1089122017-01-01T00:00:00ZCryogenic deformation of two comet and asteroid analogs under varying conditions of saturation
http://hdl.handle.net/1721.1/107110
Cryogenic deformation of two comet and asteroid analogs under varying conditions of saturation
Atkinson, Jared William Graham
Sample retrieval from extraterrestrial bodies and in situ resource utilization (ISRU) activities have been identified as some of the most important scientific endeavors of the coming decade. With the failure of Rosetta's Philae lander to penetrate the surface of comet 67P and obtain a sample due to the high compressive strength of the surface, it is becoming obvious that knowledge of the mechanical properties of materials that might be encountered in such environments and under such conditions is critical to future mission success. Two comet/asteroid analogs (Indiana limestone and Bishop tuff), selected based on their contrasting mechanical properties and porosities, were tested under constant displacement to failure (in most cases) at extraterrestrial conditions of cryogenic temperatures (295 K down to 77 K) and light confining pressures (1 to 5 MPa). The compressive strength of both materials was determined under varied conditions of saturation, from oven-dried (~0% water content) to fully saturated, and both brittle and ductile behavior was observed. The saturated limestone increased in strength from -30 MPa (at 295 K) to >200 MPa (at 77 K), while the Bishop tuff increased in strength from 13 MPa at 295 K to 165 MPa at 150 K. Additional experiments demonstrated that thermal cycling reduces the compressive strength of limestone, while an increase in confining pressure from 5 MPa to 30 MPa at 200 K significantly increases the strength (from 62 MPa to 85 MPa respectively) of saturated tuff. The results of this study will be useful to future sample retrieval missions or ISRU maneuvers. The large increase in compressive strength of these saturated materials at cryogenic temperatures means that future missions will need to prepare technology that has the energetic and mechanical capability to penetrate very hard substrates as they are likely to encounter.
Thesis: S.M. in Planetary Sciences, Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2016.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 65-70).
Fri, 01 Jan 2016 00:00:00 GMThttp://hdl.handle.net/1721.1/1071102016-01-01T00:00:00Z