http://hdl.handle.net/1721.1/7582 http://hdl.handle.net/1721.1/33722 Induced seismicity analysis for reservoir characterization at a petroleum field in Oman Sze, Edmond Kin-Man This thesis presents the analysis and interpretation of passive seismic data collected in a 20-month monitoring period. The investigation is divided into four studies, each focusing on a different aspect of the seismic data to infer the reservoir properties. First, I applied three different methods (the iterative linearized, nonlinear grid-search, and double-difference methods) to relocate 405 microearthquakes that occurred between October 1999 and June 2001 in a producing field in Oman. A numerical technique is applied to "collapse" the relocated hypocenters and to find the simplest structural interpretation consistent with the data. Comparing the methods, the applicability of waveform correlation methods such as the double-difference in this case is limited by the relatively large number of events with dissimilar waveforms. Unlike the iterative linearized method, the nonlinear grid-search method gives the best results with the smallest average rms error of the absolute locations because it avoids the local minimum problem. (cont.) The relocated hypocenters clearly delineate nearly vertical, northeast-southwest striking faults near the crest of the field, which is consistent with the graben fault system mapped by surface geologic surveys and reflection seismic interpretations. I also performed statistical tests to estimate location errors, and found that the station geometry is the major factor that limits the accuracy of focal depths. Secondly, this thesis presents a non-linear wavelet-based approach to linear waveform inversion of high-frequency seismograms for the estimation of a point source mechanism and its time function. For earthquake mechanism inversions, it is important to stabilize the problem by reducing the number of parameters to be determined. Commonly, overlapping isosceles triangles or boxcar functions are used for the parameterization of the moment tensor rate functions (MTRFs). Here, I develop a wavelet-based strategy that allows us to construct an adaptive, problem-dependent parameterization for the MTRFs employing fractional spline wavelets. Synthetic results demonstrate that the adaptive parameterization improves the numerical approximation to the model space and therefore, allows more accurate estimations of the MTRFs. (cont.) The waveform inversion is performed in the wavelet domain and leads to a multiresolution sparse matrix representation of the inverse problem. At each resolution level a regularized least-squares solution is obtained using the conjugate gradient method. The wavelet-based waveform inversion method has been applied successfully in three real- data examples: the April 22, 2002 Au Sable Forks, New York earthquake, the September 3, 2002 Yorba Linda, California earthquakes, and 11 M>1 microearthquakes in a producing field in Oman. In the Oman field, the dominant styles of focal mechanism are left-lateral strike-slip for events with focal depths less than 1.5 km, and dip-slip along an obliquely trending fault for those with focal depths greater than 2.0 km. Thirdly, the covariance matrix method of shear-wave splitting analysis is presented. Different from conventional methods that usually analyze only two horizontal components, this method processes all three components of the seismogram simultaneously, allowing not only orientation but also dip information of fractures to be resolved. Synthetic test results show that this method is stable even for high noise level. (cont.) The method is applied to the Oman microearthquake records that display distinctive shear-wave splitting and polarization directions. From the polarizations, I estimate the predominant subsurface fracture directions and dipping angles. From the time delays of the split wave I determine the fracture density distributions in the reservoir. Finally, I examine the spatio-temporal characteristics of the microseismicity in the producing reservoir. The frequency-magnitude distribution measured by the b-value is determined using the maximum likelihood method. I found that b-values are higher for events below the deeper Shuaiba oil reservoir than those above. Also, the feasibility of monitoring the temporal change of b-values is demonstrated. The analysis of production and injection well data shows that seismicity event rates in the field all strongly correlated with gas production from the shallower Natih Formation. Microseismicity, focal mechanisms, GPS analysis, and production / injection well data all suggest the NE- SW bounding graben fault system responds elastically to the gas-production-induced stresses. Normal faulting is enhanced in the reservoirs by the compaction related stresses acting on the graben fault system. Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2005. Includes bibliographical references. Fri, 29 Oct 2004 22:58:59 GMT http://hdl.handle.net/1721.1/33703 Layer-by-layer surface manipulation and biointegration of quantum dots : assembly of nanostructured DNA delivery vehicles Jaffar, Saeeda Mahdi Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2005. Includes bibliographical references. Fri, 29 Oct 2004 22:58:59 GMT http://hdl.handle.net/1721.1/17743 Fluorescence-based detection methodologies for nitric oxide using transition metal scaffolds Hilderbrand, Scott A. (Scott Alan), 1976- Chapter 1. Fluorescence-Based Detection Methodologies for Nitric Oxide: A Review. Chapter 2. Cobalt Chemistry with Mixed Aminotroponimine Salicylaldimine Ligands: Synthesis, Characterization, and Nitric Oxide Reactivity. Chapter 3. Carboxylate-Bridged Dimetallic Complexes as Potential Nitric Oxide Sensors. Chapter 4. Dirhodium Tetracarboxylate Scaffolds as Reversible Fluorescence- Based Nitric Oxide Sensors. Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2004. MIT Institute Archives copy has p. 191-192 bound between p. 188 and p. 189. Vita. Includes bibliographical references. Wed, 29 Oct 2003 22:58:59 GMT http://hdl.handle.net/1721.1/29298 Industrial applications of photonuclear resonance excitation Chichester, David Lee, 1971- Photonuclear resonance excitation refers to a variety of photonuclear interaction processes that lead to the excitation of a nucleus from some initial state to a higher energy nuclear state. Typical excited nuclear state lifetimes are short, ranging from nanoseconds to femtoseconds or less; however, some isotopes have unusually long-lived excited nuclear energy states, or isomers. This dissertation examines the feasibility of using bremsstrahlung irradiation sources to produce isomers for industrial applications. In contrast with charged particle based isomer production, the use of high energy photons allows for the irradiation and production of isomers in bulk materials. The commercial availability of reliable, high power industrial electron accelerators means that isomer activities sufficient for industrial applications may be achieved using bremsstrahlung, in contrast with neutron based approaches where suitable neutron sources of sufficient intensity for these applications are lacking. In order to design a system for creating nuclear isomers using photons, the resonant photon absorption isomeric excitation cross section must be known. Unlike neutron absorption and scattering cross sections, comparatively little information exists for photon isomeric excitation. To address this, a theoretical model based upon statistical probability distributions of nuclear energy levels has been developed for calculating photon excitation cross sections at energies below neutron and proton binding energies; the ideal region of operation for most applications in order to minimize long term activation of materials. Isomeric excitation cross sections calculated using this technique have been compared with experimentally measured values and are found to agree to within a factor of two or better. (cont.) sing this, a general transition equation suitable for both nuclear resonance fluorescence and isomer excitation has been developed for calculating nuclear level distribution probabilities for materials undergoing photon irradiation. Experiments have been carried out using an industrial 6 MeV electron accelerator to identify obstacles related to nuclear resonance fluorescence measurements as well as measurements of the decay of short-lived isomers using scintillators in the vicinity of high intensity bremsstrahlung sources. Use of a fast switching gating circuit in combination with a pulsed accelerator was found to be a satisfactory solution for dealing with problems related to the performance of a detectors photomultiplier tube as a result of exposure to scattered radiation during the beam pulse. Calculations have been carried out to assess the performance characteristics which could be expected from industrial photonuclear resonance excitation systems, based upon a 10 MeV electron accelerator. For simple isomer production, specific activities on the order of 1 mCi/g/mA can be expected for irradiation periods sufficiently long for equilibrium to be reached. For the analysis of arsenic concentrations in environmental samples, sensitivities of 1 +/- 0.1 ppm could be achieved using accelerator currents of 50 - 100 [mu]A with irradiations times of a few minutes or less. A system designed to analyze ore traveling along a conveyor belt could be used to sort gold ore based upon a lower grade cutoff of 5 ppm using an accelerator of 10 mA ... Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2000. Includes bibliographical references (p. 187-198). Fri, 29 Oct 1999 22:58:59 GMT