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Geohazards
Published in White David, Cassidy Mark, Offshore Geotechnical Engineering, 2017
The Phase 3 activities involve the final detailed integration of all of the various data sets. This is an intensive stage of any project and involves close interaction between the geologists, geotechnical engineers and owner’s representatives. During this stage, additional geophysical processing may be carried out (e.g. seismic inversion), final sub-surface soil models are developed, and soil parameters are defined for use in specialty studies such as site amplification, liquefaction and slope stability analyses. Detailed geohazard assessments are also carried out to address the distribution, severity and frequency of geohazards such as submarine slope failures, mass gravity flows, faulting, strong ground shaking, liquefaction, scour, gas hydrates and fluid expulsion. The results of the Phase 3 detailed investigations should be transmitted in a format suitable for incorporation into economic loss estimation, final siting and foundation design.
Coupling site wide CPT profiles and genetic algorithms for whole-site offshore windfarm layout optimization
Published in Guido Gottardi, Laura Tonni, Cone Penetration Testing 2022, 2022
J.A. Charles, S.M. Gourvenec, M.E. Vardy
There are emerging techniques that would potentially eliminate the issues of this interpolation step. On a site with continuous geophysical survey data and discrete CPT data, it is possible to combine seismic inversion methods with machine learning algorithms predict a synthetic CPT profile at any location on the site (Vardy et al., 2018; Sauvin et al., 2019). This technique would potentially represent a significant improvement to site wide characterization and work is actively ongoing in this area, but has not seen widespread application, and therefore the suitability of the method for different site conditions is unclear.
I
Published in Splinter Robert, Illustrated Encyclopedia of Applied and Engineering Physics, 2017
[acoustics, biomedical, geophysics, imaging, molecular, solid-state, theoretical, thermodynamics] An inversion generally refers to a process that changes sign or direction or has a discontinuity when the boundary conditions change. Inversion applies specifically to the areas of acoustics, meteorology, and molecular quantum mechanics, each in its own specific manner. The field of acoustical inversion ranges from seismologic imaging to biological imaging. In acoustics, inversions refer to the process where seismic phenomena (e.g., acoustic probing) provide reflections of the pressure wave based on geologic discontinuities. Seismic inversion can provide an indication of natural gas or oil reservoirs imbedded in rock formations. The lower density liquid or gas bordering a solid rock will provide a phase shift in the acoustic waveform. In acoustic imaging for medical applications and in nondestructive testing, the same inversion can yield mechanical information about abrupt changes in structural density, highlighting soft tissues. Inversion mode imaging for biological applications specifically provides insight in fetal fluid structures. In meteorology, inversion indicates a layered atmosphere with a temperature profile that instead of decreasing with altitude has an inversion point where the temperature is higher than at lower altitude. Inversion layers can support violet thunderstorms due to the rapid condensation. In molecular dynamics, specifically molecular vibration, an energy hierarchy can be recognized from spectroscopic analysis. The vibration process can be separated into vibrational and rotational processes. The vibrational spectral lines are in the infrared (1000 cm−1 region), while the rotational transitions are in the microwave (1 cm−1 region). The vibrational transitions are separated into an energy potential well diagram by a potential barrier around the parabolic minimum, yielding two respective minima. The microwave transitions for certain molecules can switch minima, this is referred to as inversion. The spectral profile will illustrate the switches in a representative inversion spectrum for the molecular group in question. In the molecular inversion process, the formation of “instantons” provides dominant tunneling paths derived based on the quantum dynamical Feynman path-integral. Instantons are the energy “surfaces” of unstable orbits with respect to inverted potential energy surfaces (see Figure I.27).
Sandstone reservoir modeling based on rock physics characterization for hydrocarbon resource potential in Southern Pakistan
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Muhammad Rizwan Mughal, Gulraiz Akhter
Seismic inversion is one of the advanced techniques that can enhance the accuracy of quantitative seismic data interpretation and has the ability to invert the given seismic data to any other physical property (Mangasi and Haris 2018). Post-stack seismic inversion helps to quantify reservoir elastic and petrophysical properties through the integration of seismic and well log data. The objective of performing seismic inversion is to generate the earth’s acoustic impedance cube from 3D seismic data cube at every trace location to get the optimal image of the subsurface strata (Russell and Hampson 1991). The inverted impedance models are used to derive the reservoir elastic and acoustic parameters (i.e., Lame’s parameters, P-wave and S-wave velocities, density, etc.) which all are fluid sensitive and hence help to detect the hydrocarbon-bearing strata. In addition, post-stack seismic inversion (at zero offsets) techniques transform the seismic reflection response into the acoustic impedance which indicates the intrinsic rock image associated with depositional boundaries (Gambús-Ordaz and Torres-Verdín 2008). The algorithms behind the seismic inversion spatially distribute and interpolate the acoustic parameters of wells to whole seismic volume. The widely used seismic inversion techniques facilitate the interpreters to significantly detect the hydrocarbon-bearing boundaries in the reservoir (Maurya et al. 2018).
Reliability enhancement of mixed-domain seismic inversion with bounding constraints
Published in Inverse Problems in Science and Engineering, 2019
Kun Li, Xing-Yao Yin, Zhao-Yun Zong
In geophysical prospecting field, many geophysical inversion methods have ill-conditioned problems due to the absence of sufficient field data. So their solutions may become unstable or non-unique [1–3]. Seismic inversion using seismic data of surface observations, with the geological law and field logging data as constraints, plays an important role in seismic quantitative prediction of subsurface spatial structure, elastic properties, physical properties of reservoir and pore-fluid parameters. Due to the inherent defects of sources, detectors and receiving equipment when seismic signal propagation in subsurface media, the lack of low and high frequencies leads to the band-limited support characteristic of seismic data, which bring the instability and multiple solutions of seismic inversion. Obtaining broadband frequency response and no noise interference of seismic data is more fruitful for the implementations of accurate seismic exploration. Unfortunately, geophysicists have to find some effective ways to fill the gap of lacking frequency components and for the reliability enhancement of estimation. There are mainly two feasible approaches to alleviate the thorny problem including hard constraints from well logging data or geology data, soft constraints of a priori hypothesis on model parameters (i.e. solutions of a sparse priori or minimum L2-norm length).