U31A-0001
Integration of Multiresolution Data using Geostatistics, Stratigraphy, and Seismic Inversions to Build Realistic Flow Simulation Models
Flow models commonly require high-resolution (~ 1 m vertical) grids of properties. Seismic data are areally dense, but their vertical resolution (~ 10 m) may be too coarse for flow models. We propose two methods to downscale seismic data to flow models. Both methods combine stochastic seismic inversion (for interval sum constraints), geologic modeling (for stratigraphic frameworks), rock physics (to interrelate acoustic and flow properties), and geostatistics (for spatial correlation); both methods also match well data. Stochastic ensembles of geomodels capture variability in a Bayesian framework. A Markov Chain Monte Carlo downscaling algorithm provides downscaled models for net thickness, gross thickness, and porosity. The fine- scale models have nonuniform stratigraphy with rich layer truncation or "pinchout" behavior. The cascading method uses realizations from a stochastic seismic inversion as exact constraints. Many seismic inversion realizations are used to sample seismic uncertainty; each is downscaled: thus, the workflow cascades. The constraints propagate rock physics and covariances into the flow model. This problem is challenging because seismic constraints confine sampling to a constraint hypersurface. The inexact constraint method uses means and variances estimated from an ensemble of seismic inversions. The downscaled models weight well and seismic data by their covariances. Each geomodel appropriately but only approximately matches all data, avoiding overtuning to inexact data. Because of pinchouts, the likelihood is nonlinear (but piecewise linear), complicating sampling and motivating use of auxiliary variables for this difficult configurational problem. Both downscaling methods are demonstrated for an oil field in offshore West Australia. Cornerpoint flow models are constructed, and screening and simulation studies are discussed. Three-dimensional flow simulations illustrate stratigraphic variability and flow behavior: prior models for geologic continuity are statistically significant and stochastic fluctuations, although smaller, are not negligible.
U31A-0002
Using 3D Geospatial Models to Improve Outcrop Analog Studies: an Example Using Crevasse Splay and Point Bar Outcrops, Upper Cretaceous, NW Colorado
The use of outcrop data as analogs for subsurface reservoirs presents challenges to the user in comparing scales as well as sedimentary body volumetrics. It is difficult to accurately estimate volumes of sedimentary bodies in outcrop if one is dealing with 2D maps and measured sections. The application of 3D geospatial models to outcrop settings helps address inherent unknowns associated with discontinuous 3D outcrops. Crevasse splay bodies are likely effective reservoirs in many thick tight-gas fluvial successions, yet they are incompletely recognized and lack the same level of dimensional data as point bars and channelbelts. A 200-ft thick vertical succession of strata within a 160-acre outcrop area within the nonmarine part of the Upper Cretaceous, lower Iles Formation, north of Rangely, Colorado, shows the dramatic differences between crevasse-splay and point-bar bodies. The outcrop contains an upward stratigraphic change from isolated, stacked crevasse channel/splay sandstone bodies to those of isolated, paired point bars within a laterally migrating 1500-ft wide, sinuous meanderbelt. A largely deterministic 3-D model of the outcrop shows critical differences in shape, facies architecture, areal distribution, and rock volume between crevasse splays and point bars. It also shows a lack of vertical and lateral connectivity among four crevasse-splay and four point-bar bodies. All sandstone bodies show similar "average" statistics: they contain the same types and gross proportions of grain sizes and facies classified by sedimentary structures, with high net-to-gross sandstone (over 90%), similar gross rock volumes (1000 to 1500 acre-ft), and average thicknesses (about 18 ft). However, the map-view dimensions, geometries, internal facies architecture and proportions are completely different due to dissimilar, yet linked, depositional processes. In addition, individual point bars are in poor lateral communication within the meanderbelt, whereas individual crevasse- splay bodies are laterally widespread and internally more contiguous. The overall geometry and connectivity of these bodies has critical implications when considering whether well downspacing is taping into new reserves or simply draining existing reserves faster.
U31A-0003
Using Earthquake Data to map Faults in 3-D: Applications and Results
Knowledge of the 3-D shape of active faults is of fundamental importance in many fields, from earthquake hazards, to oil exploration, to regional tectonics and seismotectonics. We have developed techniques in 3-D fault modeling whose applications range from models of single fault surfaces or small groups of faults, which can be used in earthquake hazards evaluation, to regional tectonic models. An example of how these techniques can be applied to the imaging of individual structures is that of the Northridge thrust in southern California. We were able to determine the 3-D geometry of the fault that generated the M 6.8, 1994 Northridge earthquake from the aftershocks of this event. It was also possible to determine the geometry of several nearby faults, some of which were previously unknown and are capable of producing damaging earthquakes. Complex fault networks can be modeled too, and the interactions between faults studied in detail. An example of this is the San Andreas fault system near San Gorgonio Pass in southern California. At San Gorgonio Pass we imaged the fault network using over 43,000 relocated small earthquakes. We then applied our knowledge of the network geometry to examine possible earthquake triggering scenarios in order to determine the likelihood of a major rupture of the San Andreas fault from the Salton Sea Los Angeles. A study of the 3-D structure of the crust in central Taiwan, where the M 7.6, 1999 Chi-Chi earthquake produced a large number of aftershocks, is an example of modeling applied to regional tectonics, and mountain building in particular. We imaged for the first time the large detachment beneath Taiwan. This detachment had been postulated by several authors, but never seen directly before, thus its exact geometry was unknown. Most faults capable of producing major earthquakes are connected to this detachment at depth. The results obtained from 3- D imaging allowed us a new test of critical-taper wedge mechanics, and suggest that the shape of the detachment controls the reversal of topographic slope across Taiwan.
U31A-0004
Integrating Data From NASA Missions Into NOAA's Pacific Region Integrated Climatology Information Products (PRICIP) Project
Hurricanes, typhoons, and cyclones are devastating to coastal areas throughout the world, especially in the Pacific Region. The strong winds, heavy rains, and high seas elements that accompany tropical storm events are of interest to researchers and forecasters alike. In a recent collaboration, NASA DEVELOP interns have teamed up with NOAA researchers to enhance their ongoing Pacific Region Integrated Climatology Products (PRICIP) project by integrating NASA mission data products. The PRICIP project will eventually become an interactive decision support tool that will assist decision makers in mitigating and recovering from natural hazards eventually reducing coastal vulnerability. DEVELOP's contribution to this ongoing project included creating hindcasts for three past extreme storm events using data from instruments on four NASA missions, QuikSCAT, TRMM, Jason-1, and Aqua. The hindcasts were in the form of interactive geovisualizations, and highlighted the strong winds, heavy rains, and high sea storm elements that were of interest to NOAA researchers. These interactive geovisualizations will contribute directly to NOAA's PRICIP decision support tool, and as they will be placed on NOAA's web portal, they will be accessible to researchers and the public through a web browser.
U31A-0005
Glacial Features in the Western Gulf of Maine Inferred From High Resolution Bathymetric Data
Multibeam sonar surveys in the last decade have revealed submerged glacial features in the western Gulf of Maine (e.g., Valentine et al., 2003). Here we examine high-resolution multibeam bathymetric data acquired in 2001 and 2005 over Jeffreys Ledge to infer the origin of previously unrecognized small-scale marine glacial features. Ridges as high as 5 m appear throughout the length of Jeffreys Ledge in water depths of ~50 m. Bottom photographs of these features show boulders of up to 50 cm diameter in a flat sandy bottom devoid of finer material. These ridges are probably recessional moraines that have been reworked during lower relative sea level (~55 m below modern sea level). The moraine-like features imply stabilization of an ice margin along the length of Jeffreys Ledge. The central portion of Jeffreys Ledge also contains asymmetrical dune forms with a relief of 1-6 m and along-crest orientations trending NW-SE. These dunes may have formed during megaflood events with water flow toward the southwest. Streamlined bathymetric features with a relief of ~8 m and lengths up to 700 m occur east of Jeffreys Ledge. These features have similar dimensions but different orientations (N-S), as compared to southeast-oriented drumlins identified south of Cape Ann by Oldale et al. (1994). Dissimilar orientations of these drumlins are consistent with the lobate shape of the ice sheet and probable local ice flow directions. Numerous iceberg scours were observed in the basins east of Stellwagen Bank and Jeffreys Ledge with varying widths (50-300 m), scour depths (1-5 m) and lengths (3-10 km). Two dominant orientations of iceberg scours (E- W and N-S) were identified. Additional data such as seismic profiles, bottom photographs and bottom samples will further define the origin of these small-scale glacial features. Oldale, R.N., Knebel, H.J., Bothner, M.H., 1994, Geomorphology 9, 301-309. Valentine, P., Unger, T., Baker, J., 2003, U.S. Geological Survey Geologic Investigations Series Map I-2676C, scale 1:60,000.
U31A-0006
Joint and Interactive Interpretation of Crustal Data in Two and Three Dimensions
An approach for integrated interpretation of crustal seismic, gravity, and other data was developed. The approach is based on a 3D interactive visualization interface included in a broad-range geophysical data processing system. The advanced interactive capability makes crustal seismic interpretation streamlined, efficient, robust, and also enjoyable. The currently available tools cover most of the traditional crustal data analysis, from ellipsoidal-Earth geometry, travel-time and horizon picking, processing seismic records and travel times, creation of starting velocity models, ray tracing, and tomography to generation of 1D, 2D, and 3D seismic waveform synthetics, migration, and gravity modeling. New tools can be readily added to the system, including by using its web collaboration capabilities. For the first time, the data analysis can be carried out in the true, 3D geometry of the datasets, on precise geo-reference base maps, simultaneously in multiple crossing lines, and in combination with other data. http://seisweb.usask.ca/SIA
U31A-0007
Flexible Software Architecture for Visualization and Seismic Data Analysis
Research in the field of seismology requires software and signal processing utilities for seismogram manipulation and analysis. Seismologists and data analysts often encounter a major problem in the use of any particular software application specific to seismic data analysis: the tuning of commands and windows to the specific waveforms and hot key combinations so as to fit their familiar informational environment. The ability to modify the user's interface independently from the developer requires an adaptive code structure. An adaptive code structure also allows for expansion of software capabilities such as new signal processing modules and implementation of more efficient algorithms. Our approach is to use a flexible "open" architecture for development of geophysical software. This report presents an integrated solution for organizing a logical software architecture based on the Unix version of the Geotool software implemented on the Microsoft NET 2.0 platform. Selection of this platform greatly expands the variety and number of computers that can implement the software, including laptops that can be utilized in field conditions. It also facilitates implementation of communication functions for seismic data requests from remote databases through the Internet. The main principle of the new architecture for Geotool is that scientists should be able to add new routines for digital waveform analysis via software plug-ins that utilize the basic Geotool display for GUI interaction. The use of plug-ins allows the efficient integration of diverse signal-processing software, including software still in preliminary development, into an organized platform without changing the fundamental structure of that platform itself. An analyst's use of Geotool is tracked via a metadata file so that future studies can reconstruct, and alter, the original signal processing operations. The work has been completed in the framework of a joint Russian- American project.