Layer | Fill | Outline |
---|
Map layers
Theme | Visible | Selectable | Appearance | Zoom Range (now: 0) |
---|
Fill | Stroke |
---|---|
Collaborating Authors
Kiel University
ABSTRACT The detection of cavities with geophysical methods is a challenging task for which a general approach has not yet been found. We have found that viscoelastic SH full-waveform inversion (FWI), focusing primarily on reflection events, is able to accurately locate the position of cavities, areas of decompacted sediments, and, more generally, seismic low-velocity anomalies down to 30 m depth. The key for a successful FWI application is the enhancement of the reflected wavefield relative to the surface wavefield. For this purpose, we apply automatic gain control normalization in the objective function. By focusing the inversion on the reflected wavefield, we determine that one can differentiate between air-filled cavities with zero shear-wave (S-wave) velocity and low-velocity zones. Additionally, we test the FWI approach on a field data set, with a known collapsed tunnel system inside a 32 m high monumental antique grave mound. The results show that the location and extent, as well as the density and S-wave velocity of the collapsed tunnel system, can be determined with sufficient accuracy by applying a 2D FWI approach to intersecting profiles, despite the 3D nature of the problem.
- Geophysics > Seismic Surveying > Seismic Processing (1.00)
- Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling > Seismic Inversion (1.00)
ABSTRACT Airborne gravity gradiometry measures several gravity gradient components unlike conventional gravimetry taking only the vertical gravity component into account. However, processing of multicomponent airborne gravity gradient (AGG) data without corrupting their internal consistency is often challenging. Therefore, we have developed an equivalent source technique to tackle this challenge. With a combination of Gauss-fast Fourier transform and the Landweber iteration, we have developed an efficient way to compute equivalent sources for AGG data. This method can handle two components simultaneously. We first examined its viability by applying this approach to a synthetic example. Afterward, we applied our method to real AGG data collected in the area of Karasjok, Norway. Our result is almost the same as the results that meet the industry standard but with great efficiency.
Advanced CFD Simulations of free-surface flows around modern sailing yachts using a newly developed openFOAM solver
Meyer, Janek (Yacht Research Unit Kiel) | Renzsch, Hannes (FluidEngineeringSolutions GmbH & Co. KG, Schleswig) | Graf, Kai (Yacht Research Unit Kiel) | Slawig, Thomas (Kiel University)
While plain vanilla OpenFOAM has strong capabilities with regards to quite a few typical CFD-tasks, some problems actually require additional bespoke solvers and numerics for efficient computation of high-quality results. One of the fields requiring these additions is the computation of large-scale free-surface flows as found e.g. in naval architecture. This holds especially for the flow around typical modern yacht hulls, often planing, sometimes with surface-piercing appendages. Particular challenges include, but are not limited to, breaking waves, sharpness of interface, numerical ventilation (aka streaking) and a wide range of flow phenomenon scales. A new OF-based application including newly implemented discretization schemes, gradient computation and rigid body motion computation is described. In the following the new code will be validated against published experimental data; the effect on accuracy, computational time and solver stability will be shown by comparison to standard OF-solvers (interFoam / interDyMFoam) and Star CCM+. The code’s capabilities to simulate complex “real-world” flows are shown on a well-known racing yacht design.
ABSTRACT Resampling of high-resolution data sets is often required for real-time applications in geosciences, e.g., interactive modeling and 3D visualization. To support interactivity and real-time computations, it is often necessary to resample the data sets to a resolution adequate to the application. Conventional resampling approaches create uniformly distributed results, which are not always the best possible solution for particular applications. I have developed a new resampling method called constrained indicator data resampling (CIDRe). This method results in irregular point distributions that are adapted to local parameter signal wavelengths of the given data. The algorithm identifies wavelength variations by analyzing gradients in the given parameter distribution. A higher point density is ensured in areas with larger gradients than in areas with smaller gradients, and thus the resulting data set shows an irregular point distribution. A synthetic data test showed that CIDRe is able to represent a data set better than conventional resampling algorithms. In a second application, CIDRe was used to reduce the number of gravity stations for interactive 3D density modeling, in which the resulting point distribution still allows accurate interactive modeling with a minimum number of data points.
Experimental Simulation Of Hydrocarbon Expulsion
Schwark, L. (Kiel University) | Stockhausen, M. (Kiel University) | Galimberti, R. (Eni SPA E&P Division) | Elias, R. (ENI E&P Division)
Abstract Laboratory studies simulating thermal maturation of source rocks to generate and expel oil/gas differ from natural conditions. Amounts and compositions of products deviate between experiments and those found in natural petroleum source, carrier and reservoir rocks. Experimental data used in numerical models simulating oil/gas generation/expulsion thus seem to require adaption, causing significant uncertainty in present petroleum systems analysis. We designed and tested a procedure to simulate laboratory generation and expulsion of hydrocarbons under conditions most similar to natural conditions. Problem identification The critical factors in combined petroleum generation and expulsion simulation studies are: the pore and kerogen network of a sediment must remain as closely as possible in its natural state, as destroyed pore-systems are unsuitable for interpretation due to artificial reaction sites and migration avenues created upon experiment; kerogen maturation must occur in the presence of water, as water acts as hydrogen donor for oil/gas formation and via hydrostatic pressure and associated flow stimulates migration of oil/gas; consequently, dry pyrolysis often used in petroleum generation experiments for kinetics calculation will not reflect near-natural oil/gas expulsion; pressure regimes applied upon experiment must mimic differentially the lithostatic and hydrostatic pressures, as lithostatic squeezing will cause collapse of clay mineral aggregates but opposes kerogen swelling in non-lithified rocks; consequently experiments under all-directional identical confining pressures are unsuitable to reflect oil/gas expulsion; the generated and then expelled oil/gas fluids must be allowed to migrate in the given pressure and permeability regime in order to avoid artificial secondary reactions, including condensation as well as cracking, hence rendering closed pyrolysis unsuitable for many petroleum expulsion studies. Exceptional cases may include tight shales, where expulsion is hindered or burial of reservoirs associated with oil to gas cracking.
- North America > United States (0.15)
- Asia > Middle East > Qatar (0.15)
- Geology > Geological Subdiscipline > Geochemistry (1.00)
- Geology > Geological Subdiscipline > Economic Geology > Petroleum Geology (0.60)
Parallel Finite-difference Modeling of Seismic Wave Scattering In 3-D Elastic Random Media
Bohlen, Thomas (Kiel University) | Müller, Tobias M. (Freie Universität Berlin) | Milkereit, Bernd (Kiel University)
Summary Three-dimensional small-scale heterogeneities cannot be resolved deterministically by seismic surveys. Nevertheless they have significant effects on seismic wave propagation. Some of these effects have been quantified numerically by 2-D elastic and 3-D acoustic modeling. Today, parallel implementation of finite difference codes makes modeling of 3-D elastic and viscoelastic smallscale structures feasible. By using the Message Passing Interface standard for the communication between processors wall clock times can be reduced and model sizes can be increased significantly. We investigate the difference of 2-D and 3-D modeled wavefields propagating through a heterogeneous reservoir. For example, scattering attenuation of the primary event, estimated by means of the spectral amplitude decay method, is compared for the 2-D and 3-D case.
SUMMARY The mineral industry is now seeking ways to optimize their exploration program by using the 3-D seismic method. The ability of this method to map volcanic contacts and 1km deep volcanogenic massive sulphide (VMS) deposit is tested in the Matagami mining camp. We show that the depth of the main exploration target can be intergarted acroos a large portion of the seimic survey area and its southwest limit defines the location of a regional fault.
- Geophysics > Seismic Surveying > Surface Seismic Acquisition (0.60)
- Geophysics > Seismic Surveying > Seismic Processing (0.40)
Summary Two vertical profile (VSP) surveys have been acquired in the vicinity of a 1 km deep VMS deposit in the Abiti subprovine of northwestern Québec. The VSP data show that P-wave velocities in the top 1km of the crust are constant at about 6300 m/s while S-wave velocities are estimated at about 3600 m/s, the sonic logging in one of the data acquired in one borehole were compared with the first VSP first break time. The agreement between the two measurements, confirms the accuracy of the velocity derived from the two methods.
ABSTRACT No preview is available for this paper.
- Geophysics > Seismic Surveying > Surface Seismic Acquisition (0.85)
- Geophysics > Seismic Surveying > Seismic Processing (0.85)
Borehole Seismic Imaging of Near-vertical Structures: A Case History
Eaton, David (Geological Survey of Canada) | Salisbury, Matt (Geological Survey of Canada) | Forsyth, David (Geological Survey of Canada) | Milkereit, Bernd (Kiel University) | Guest, Sean (Koninklijke Shell Explaortie en Produktie Laboratorium) | Schmitt, Doug (University of Alberta) | Crick, Dean (Falconbridge Ltd)
Deep boreholes This paper presents recently acquired three-component provide an alternative acquisition datum for seismic borehole seismic data from the vicinity of the giant Kidd imaging in this type of setting. At the giant Kidd Creek Cu-Creek Cu-Zn deposit in the Abitibi greenstone belt, Canada Zn deposit, the Archean volcanic stratigraphy has been (Figure 1). The data were collected to assess the potential of folded and overturned so that most units are nearly vertical.
- Research Report > New Finding (0.34)
- Research Report > Experimental Study (0.34)
- Geology > Geological Subdiscipline > Stratigraphy (0.71)
- Geology > Rock Type > Igneous Rock (0.47)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Near-well and vertical seismic profiles (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Borehole imaging and wellbore seismic (1.00)