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In this paper, we study newly developed methods for linear elasticity on polyhedral meshes. Our emphasis is on applications of the methods to geological models. Models of subsurface, and in particular sedimentary rocks, naturally lead to general polyhedral meshes. Numerical methods which can directly handle such representation are highly desirable. Many of the numerical challenges in simulation of subsurface applications come from the lack of robustness and accuracy of numerical methods in the case of highly distorted grids. In this paper, we investigate and compare the Multi-Point Stress Approximation (MPSA) and the Virtual Element Method (VEM) with regard to grid features that are frequently seen in geological models and likely to lead to a lack of accuracy of the methods. In particular, we look at how the methods perform near the incompressible limit. This work shows that both methods are promising for flexible modeling of subsurface mechanics. 相似文献
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Geological carbon storage represents a new and substantial challenge for the subsurface geosciences. To increase understanding and make good engineering decisions, containment processes and large-scale storage operations must be simulated in a thousand year perspective. A hierarchy of models of increasing computational complexity for analysis and simulation of large-scale CO2 storage has been implemented as a separate module of the open-source Matlab Reservoir Simulation Toolbox (MRST). This paper describes a general family of two-scale models available in this module. The models consist of two-dimensional flow equations formulated in terms of effective quantities obtained from hydrostatic reconstructions of vertical pressure and saturation distributions. The corresponding formulation is fully implicit and is the first to give a mass-conservative treatment and include general (non-linearized) CO2 properties. In particular, the models account for compressibility, dissolution, and hysteresis effects in the fine-scale capillary and relative permeability functions and can be used to accurately and efficiently study the combined large-scale and long-term effects of structural, residual, and solubility trapping. 相似文献
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There has been a long-standing debate concerning how dangerous seismic surveys are with respect to marine life. Marine seismic
work today is dominated by airgun technology, where high energy is generated by a release of compressed air into the water.
The objective of the “Time coded impulse seismic technique” project is to examine whether a new low energy acoustic source
can be used for seismic purposes. If the method turns out to be successful, the low output energy and continuous operation
will make the source suitable in environmental sensitive areas. The Low level Acoustic Combustion Source (LACS) is a petrol
driven pulsed underwater acoustic source. It operates at a few meters depth, and each shot can be digitally controlled from
the surface by a computer located in the mother vessel. A presentation of the recorded LACS signal characteristics, the modulation,
the Pseudo Noise coding/decoding principles and field test results, is given. The importance of using an optimized code with
fine resolution and of using the near field recording as a correlator sequence is demonstrated. Clear correlation peaks could
then be seen from the bottom and sub bottom reflectors. 相似文献
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Structure and evolution of an obliquely sheared continental margin: Rio Muni, West Africa 总被引：4，自引：0，他引：4
Oblique-shear margins are divergent continental terrains whose breakup and early drift evolution are characterized by significant obliquity in the plate divergence vector relative to the strike of the margin. We focus on the Rio Muni margin, equatorial West Africa, where the ca. 70-km-wide Ascension Fracture Zone (AFZ) exhibits oblique–slip faulting and synrift half-graben formation that accommodated oblique extension during the period leading up to and immediately following whole lithosphere failure and continental breakup (ca. 117 Ma). Oblique extension is recorded also by strike–slip and oblique–slip fault geometry within the AFZ, and buckling of Aptian synrift rocks in response to block rotation and local transpression. Rio Muni shares basic characteristics of both rifted and transform margins, the end members of a spectrum of continental margin kinematics. At transform margins, continental breakup and the onset of oceanic spreading (drifting) are separate episodes recorded by discrete breakup and drift unconformities. Oceanic opening will proceed immediately following breakup on a rifted margin, whereas transform and oblique-shear margins may experience several tens of millennia between breakup and drift. Noncoeval breakup and drift have important consequences for the fit of the equatorial South American and African margins because, in reconstructing the configuration of conjugate continental margins at the time of their breakup, it cannot be assumed that highly segmented margins like the South Atlantic will match each other at their ocean–continent boundaries (OCBs). Well known ‘misfits’ in reconstructions of South Atlantic continental margins may be accounted for by differential timing of breakup and drifting between oblique-shear margins and their adjacent rifted segments. 相似文献
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Erminio Murano Renato Toffanin Ester Cecere Roberto Rizzo Svein Halvor Knutsen 《Marine Chemistry》1997,58(3-4)
Dried samples of the red algae Solieria filiformis and Agardhiella subulata from Mar Piccolo, Taranto, were extracted by stirring in water at 25 (Cold), 85 (Hot) and 120 (pressure) °C. For each species, six successive cold, three hot and two pressure extractions were performed and analyzed separately. Water-soluble polysaccharides were isolated after treatment with amylase, alcohol precipitation, dialysis and freeze drying. The total, starch-free yields were 27 and 24% of the dry weight for S. filiformis (SF) and A. subulata (AS), respectively. FTIR and NMR spectroscopic analysis showed that the different cold and hot water extracts had a similar structural backbone, which can be characteristic of gelling type carrageenans with a dominant iota repeating structure (DA2S-G4S). However, some irregularities were detected by NMR, which may be attributed to 6-sulphated 4-linked precursor units. The occurrence of such and other irregularities was more frequent in the SF samples, giving a possible explanation for the enhanced extractability in cold water of carrageenan polymers from this species. 相似文献
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