Physical Sciences and Mathematics Commons^™

Can Seismic Velocity Stacking Errors Result In The Low-Frequency Shadow?, Umit Serhan Inan

Dissertations, Master's Theses and Master's Reports

The low-frequency shadow is the area on reflection seismic data, underneath gas reservoirs, that exhibits anomalously low frequency. This phenomenon has been related to the highly attenuating nature of the gas reservoir, which could explain the low-frequency shadows observed underneath extremely thick reservoirs, but not the ones underneath thin reservoirs. There are several other mechanisms that could be responsible, however detailed analysis of these possible explanations is yet to be found in the literature.

The main focus of this research is to test the possible contribution of stacking of offset seismic data, namely, their mis-stacking, to the generation of the …

Experimental Study Of The Flow Of Ferrofluid In A Porous Media Under A Magnetic Field, Muskaan Khurana

Dissertations, Master's Theses and Master's Reports

This research presents results from a laboratory-scale experimental setup that was designed to visualize the behavior of ferrofluid percolation through a porous media. Ferrofluids are colloidal suspensions made of magnetic particles of a few nanometers and stabilized in carrier liquids like water or mineral oil. Ferrofluids get magnetized and align themselves in the direction of a magnetic field when a field gradient is applied.

With the help of this experiment we investigate the viability of controlling fluid flow in porous medium by a magnetic field in vicinity. The experiments show that ferrofluids can be used as a transporting media to …

Nonlinear Inversion Strategies Applied To Source Characterization And 3d Earthquake Tomography In Volcanic Environments: A Case Study At Pacaya Volcano, Guatemala, Federica Lanza

Dissertations, Master's Theses and Master's Reports

Full-waveform moment tensor inversion of volcanic seismic signals and travel-time 3D tomography of local earthquakes have been widely used to explore source processes related to magma transport as well as to image the location and size of magma storage systems. However, the inversion solutions and the associated reliability estimates are non-unique and bear intrinsic uncertainties due to simplifying assumptions about the source, inaccuracies in the velocity models, dependence on network configuration, and other a priori constraints imposed by the modeler.

This work addresses the non-uniqueness and uncertainties of the model results by introducing non-linear inversion techniques that allow sampling the …

Reservoir Estimation In The Penobscot 3d Seismic Volume Using Constrained Sparse Spike Inversion, Offshore Nova Scotia, Canada, Mengchu Xiao

Dissertations, Master's Theses and Master's Reports

The Penobscot study area is located offshore Nova Scotia, Canada. There are two wells, which penetrate the highest potentially commercial bodies in the Abenaki Formation. In order to investigate the potential for locating additional hydrocarbon reservoirs, well log data was used and the Penobscot 3D seismic dataset was analyzed using Constrained Sparse Spike Inversion. From the well log data, low GR and SP values are an indication of a permeable sand layer, which provides the target zone in this study. Impedance – porosity crossplots gave the relationship between impedance and porosity, where a low impedance sand layer is correlated with …

Comparison Of Different Seismic Filtering Techniques On Prestack Inversion For Penobscot Area-Nova Scotia, Omer Emre Uygun

Dissertations, Master's Theses and Master's Reports

The goal of this study is to compare three different type of seismic filtering according to their inversion results and their quality of data improvements. To do this bandpass filter, Inverse Q, and Radon transform are applied to the original NMO corrected pre-stack data from Nova-Scotia offshore Canada.

The seismic data used was provided as pre-stack data of generally good quality. The test for quality of data improvement comes from the results of inversion based on different types of filtering performed on the pre-stack gathers.

Bandpass filter, Inverse Q, and Radon transform are applied to the migrated prestack data, over …

Influence Of The Weathered Layer On Retrieving Body Wave Using Passive Siesmic Interferometry, Boming Wu

Dissertations, Master's Theses and Master's Reports

Passive seismic interferometry (SI) is an increasingly popular seismic method due to its cost-efficient advantage because it does not need an active source. Techniques in using SI to retrieve surface waves are relatively well established, but using SI to retrieve body waves is still under development by many authors. These geophysicists have proved that many factors, such as average duration of the natural sources, the number of natural sources that occurred during recording time, source distribution, etc., influence the quality of body waves retrieved. In this research, I focus on how to make use of the attenuation property of weathered …

Enhancement Of Margrave Deconvolution And Q Estimation In Highly Attenuating Media Using The Modified S-Transform, Adnan Djeffal

Dissertations, Master's Theses and Master's Reports

We evaluate the performance of the Margrave deconvolution and spectral ratio methods using the Gabor, S-, and modified S transforms in highly attenuating media, where the quality factor changes with depth dramatically. Our results substantiate that the modified S-transform deconvolution is more robust in terms of generating fewer artifacts and providing better estimates of reflectivities than the Gabor transform. The results also show that using the modified S-transform in the spectral ratio method produces better Q estimates than the S-transform and the Fourier transform that is conventionally used in the spectral ratio method. This improvement in the estimates of reflectivities …

Petrophysical And Empirical And Theoretical Rock Physics Modeling For The Moki Formation In Two Fields In The Taranaki Basin, New Zealand, Deniz Yener

Dissertations, Master's Theses and Master's Reports

This work consists of conventional petrophysical analysis and sonic response determination from empirical relations, rock physics modelling, and fluid substitution for six wells in the Moki formation of New Zealand’s Taranaki Basin. The project composed of three parts encompassing conventional log analysis, rock-physics modeling using empirical and theoretical approaches, and finally rock-physics modeling for shaley sands using semi-empirical adaptations to Gassmann fluid substitution. Finally, comparisons are made between results for the different wells, based on their depths and mineralogy.

The first part of this study is presented as a petrophysical analysis, including crossplot analysis, conventional 3-mineral identification approach, and determination …

Numerical Modeling Of Ambient Noise Seismic Interferometry, Simisola M. Arogundade

Dissertations, Master's Theses and Master's Reports

CO₂ sequestration involves storing CO₂ in a deep geological formation and may help to mitigate the increasing emission of carbon. To monitor the migration of injected fluid in the reservoir, seismic observations may be used to observe changes in reflection character. Conventional methods to image the subsurface, using active seismic measurements, with man-made sources, have been applied at a few test sites, and the use of passive measurements, with natural sources, has been considered as a probable cost-efficient method to monitor CO₂ migration and leakage. This numerical modeling study examines the use of seismic interferometry to retrieve …

Cave Detection Using Seismic Methods At Madison Blue Spring State Park, Madison County, Florida, Charles Breithaupt

Dissertations, Master's Theses and Master's Reports

Locating caves and quantifying their geometries has significant importance in aquifer characterization, sinkhole mitigation, and contaminant transport monitoring. Several geophysical methods have been used for cave detection with limited success, but no reliable solution has been found. New developments in seismic techniques, however, show promising results indicating that cave voids may be more accurately detected.

We evaluated the capability of several seismic techniques to detect caves by collecting new seismic data over a known conduit connected to Madison Blue Spring, in northern Florida. These analyses validated the abilities of diffracted surface waves to detect water-filled caves by viewing these data …

Comparisons Of Seismic Interferometry By Cross Correlation, Deconvolution, And Cross Coherence, Haitao Cao

Dissertations, Master's Theses and Master's Reports

Ambient noise seismic interferometry (ANSI) has been applied widely for geophysical investigations including earthquake tomography, civil engineering and seismic exploration purposes. Comparing this approach with the traditional active seismic survey, the application of ANSI is cost effective, environmentally friendly and easily repeatable. Conventional seismic interferometry by cross correlating wavefields recorded at different receivers has already obtained fruitful results.

Even though the application of seismic interferometry (SI) by cross correlation has been successful, different methods for the processing workflow such as cross coherence and deconvolution have been conducted in an effort to improve the resolution. While these three methods have been …

Reservoir Characterization Through Pre-Stack Seismic Analysis And Inversion In The Thrace Basin, Northwest Turkey, Emre Doguturk

Dissertations, Master's Theses and Master's Reports

This study analyzes hydrocarbon reservoirs by using Amplitude-Versus-Offset (AVO) analysis and different inversion methods to investigate hydrocarbon reservoir in the Thrace Basin which is located in northwest Turkey.

A 3D seismic survey containing prestack data was provided by Turkish Petroleum Corporation as true amplitude NMO corrected 3D gathers.

The quality of this land data was poor for AVO applications, and steps were taken to make it useful. Radon filtering proved to be extremely useful for this purpose. Although application of this filter affected the AVO characteristics differently depending on the parameters selected for the filter, relative AVO characteristics remained useful …

Preliminary Seismic Coda Wave Attenuation Study Of Pacaya Volcano, Guatemala, Maximilian Guettinger

Dissertations, Master's Theses and Master's Reports

Pacaya volcano is a basaltic complex in the Central American Volcanic Arc in Guatemala. Pacaya has been in an open vent condition since 1961. During January 2015 we deployed 19 short period seismometer stations on Pacaya at distances less than 1.5 kilometers from the summit. The resulting data consisted of tremor and thousands of discrete events associated with ongoing outgassing. Where possible, individual events were identified and located. They were found to be high in the edifice near the vent. We used the decaying codas of these events to model the attenuation structure of the Pacaya edifice, following the energy …