Browsing by Subject "resolution"
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Item High-Resolution Characterization of Reservoir Heterogeneity and Connectivity in Clastic Environments(2011-10-21) Hull, Thomas FrederickThis study developed new concepts and interpretative methods for mapping reservoir heterogeneity and connectivity of a fault controlled Wilcox clastic reservoir in Texas, USA. The application of high-resolution seismic enhancement in this study allows for better delineation of subsurface geologic features, detailed mapping of reservoir heterogeneities and more accurate identification of depositional, structural, and stratigraphic characteristics that control reservoir connectivity and fluid flow. Seismic enhancement in this study pertains to amplitude preserving neural network implementation of the Volterra integral equation of the first kind from a plane-wave solution of poro-viscoelasticity (Sun, et al., 2003). This enhancement amounts to an advanced spiked deconvolution of post-stack seismic data that broadened the dominant seismic frequency from 16Hz for the conventional seismic to 65Hz for the enhanced seismic. Bed resolution is improved from 175ft to 45ft and fault offset resolution is improved from 80ft to 20ft. High-resolution seismic interpretation was validated through synthetic seismograms, stratigraphic surface comparisons, and most importantly using a comprehensive model-based knowledge of regional tectonics and depositional environments. Stratigraphic features that were not resolvable in conventional seismic data can now be interpreted using the enhanced seismic data. An Upper Wilcox reservoir was identified as a transgressive sheet sand overlaying a progradational deltaic seismic facies. An Upper Middle Wilcox reservoir was identified as a probable lobate gravity flow, and a Middle Wilcox reservoir was identified as a transgressive sheet sand with over and underlying progradational deltaic seismic facies. Geobody extraction from seismic inversion volumes delineates reservoir compartments and flow units. Reservoir connectivity analysis performed on the Middle Wilcox reservoir determined the probable drainage area for a producing well by comparing estimates of compartmentalized hydrocarbon volumes with production information. The methodology developed could help extract connected geobodies defined by sand, porosity, permeability, and hydrocarbon indicators, to map in detail the internal structure of produced reservoir and to locate new development prospects. Enhanced seismic may thus enable us to find bypassed hydrocarbons and to provide better methods for improving recovery in the studied and other mature fields.Item Potential impacts of vertical cable seismic: modeling, resolution and multiple attenuation(Texas A&M University, 2004-09-30) Wilson, Ryan JustinVertical cable seismic methods are becoming more relevant as we require high quality and high resolution seismic data in both land and marine environments. Our goal in this thesis is to demonstrate the impacts of vertical cable surveying in these areas. Vertical cable methods have been applied to the marine environment with encouraging results. Data quality is similar to that of traditional towed-streamer data, without the long, cumbersome towed-streamers which are difficult to maneuver in congested areas. The current marine vertical cable processing schemes tend to use primaries and receiver ghosts of primaries for imaging. Therefore, we demonstrate the ability of the current multiple attenuation algorithms developed by Ikelle (2001) to preserve either primaries or the receiver ghosts of primaries. As we focus on land acquisition, we discover that vertical cable surveying can overcome many of the traditional problems of land seismics. In fact, our investigations lead us to believe that problems such as ground roll, guided waves and statics can be avoided almost entirely using vertical cable acquisition methods. Furthermore, land vertical surveying is naturally suited for multi-component acquisition and time-lapse surveying. To fully analyze the applicability of vertical cable surveys in marine and land environments, we also investigate the problem of cable spacing and sampling within each cable. We compare the resolution of vertical cable data and horizontal data by calculating the maximum angular coverage of each acquisition geometry and measuring the occurrence of each angle within this coverage, such that more occurrences means better resolution. From our investigations, we find that by using vertical cables of no more than 500 m in length at 500 m intervals, we can acquire higher resolution seismic data relative to horizontal surface methods for an image point, horizontal reflector or a dipping reflector. The key tool used in these investigations is fully elastic finite-difference modeling. We chose this technique based on its ability to properly and accurately model the full wavefield through complex models, all the while preserving amplitudes and the phase of reflected, diffracted and converted wavefields.