Carbon dioxide capture and geological storage (CCGS) is an emerging technology that is increasingly being considered for reducing
greenhouse gas emissions to the atmosphere. Deep saline aquifers provide a very large capacity for CO2 storage and, unlike hydrocarbon reservoirs and coal beds, are immediately accessible and are found in all sedimentary basins.
Proper understanding of the displacement character of CO2-brine systems at in-situ conditions is essential in ascertaining CO2 injectivity, migration and trapping in the pore space as a residual gas or supercritical fluid, and in assessing the suitability
and safety of prospective CO2 storage sites. Because of lack of published data, the authors conducted a program of measuring the relative permeability
and other displacement characteristics of CO2-brine systems for sandstone, carbonate and shale formations in central Alberta in western Canada. The tested formations are
representative of the in-situ characteristics of deep saline aquifers in compacted on-shore North American sedimentary basins.
The results show that the capillary pressure, interfacial tension, relative permeability and other displacements characteristics
of CO2-brine systems depend on the in-situ conditions of pressure, temperature and water salinity, and on the pore size distribution
of the sedimentary rock. This paper presents a synthesis and interpretation of the results. 相似文献
It is well established that the Argentine passive margin is of the rifted volcanic margin type. This classification is based primarily on the presence of a buried volcanic wedge beneath the continental slope, manifested by seismic data as a seaward dipping reflector sequence (SDRS). Here, we investigate the deep structure of the Argentine volcanic margin at 44°S over 200 km from the shelf to the deep oceanic Argentine Basin. We use wide-angle reflection/refraction seismic data to perform a joint travel time inversion for refracted and reflected travel times. The resulting P-wave velocity-depth model confirms the typical volcanic margin structure. An underplated body is resolved as distinctive high seismic velocity (vp up to 7.5 km/s) feature in the lower crust in the prolongation of a seaward dipping reflector sequence. A remarkable result is that a second, isolated body of high seismic velocity (vp up to 7.3 km/s) exists landward of the first high-velocity feature. The centres of both bodies are 60 km apart. The high-velocity lower-crustal bodies likely were emplaced during transient magmatic–volcanic events accompanying the late rifting and initial drifting stages. The lateral variability of the lower crust may be an expression of a multiple rifting process in the sense that the South Atlantic rift evolved by instantaneous breakup of longer continental margin segments. These segments are confined by transfer zones that acted as rift propagation barriers. A lower-crustal reflector was detected at 3 to 5 km above the modern Moho and probably represents the lower boundary of stretched continental crust. With this finding we suggest that the continent–ocean boundary is situated 70 km more seaward than in previous interpretations. 相似文献
We present a back-propagation neural network with an input layer in the form of a tapped delay line wich can be trained effectively
on one or several well logs to recognize a particular geological marker. Subsequently, the neural network proposes locations
of this marker on other wells in the field. Another neural network, similar in architecture to the first one, performs the
same task for secondary markers using, in addition to the well logs, a depth reference function to the first marker. This
method is shown to have better performance and better discrimination than standard cross-correlation techniques. It lends
itself well for an interactive implementation on a workstation. 相似文献
Heterogeneity is present in geological sedimentary structures at all scales from pore to basin, and its distribution has an impact on transport processes such as heat and fluid flow. The rock masses at any scale need to be characterized by their effective properties at that scale, based on the individual characteristics of the heterogeneous porous medium. The effective thermal and hydraulic conductivity of sediments characterized by a stochastic distribution of heterogeneity is studied using an inverse approach based on numerical experiments. The simulations, covering a large range of conductivity contrasts, are carried out for actual core-scale cases of shale clasts in a sand matrix, and on a diagrammatic cross-section through a clastic sedimentary group at the basin scale.
The effective conductivity depends primarily on the heterogeneity fraction and on the conductivity contrast between heterogeneities and the embedding matrix, a dependency which can be described by a generalized weighted mean model. This model is better suited to estimate the effective conductivity at any scale than other models like the self-consistent, or any of the arithmetic, geometric or harmonic averages. The effective conductivity has an anisotropic character although the individual components are homogeneous and isotropic. The variation in effective conductivity is significant even for small conductivity contrasts, like in heat flow processes, and exhibits an asymptotic behaviour for large conductivity contrasts characteristic of fluid flow processes. The effective conductivity has a second-order dependence on such heterogeneity characteristics as shape, aspect ratio, orientation, and distribution. Depending on these characteristics, the bounds of effective conductivity values can be narrowed further from the extreme bounds expressed by the arithmetic and harmonic averages. 相似文献
The Lockne impact crater south of Östersund formed in the early Middle Cambrian with a diameter of 7 km. It is identified by its rim wall of crushed Precambrian basement granite, by fragments of impact melt, and by grains of shocked quartz. The exceptional preservation, in particular of the rim wall, is due to a complicated geological history, the first stage of which consisted of burial by marine sediments. This stage lasted until the Middle Ordovician, or over 50 million years. An early Caradoc lowering of the sea-level may have induced debris flows that stripped the rim wall of much of its sedimentary cover. Because normal marine sedimentation recommenced soon after this event, the structure was not seriously damaged, as it was buried again. The Caledonian orogeny emplaced an overthrust nappe as ultimate protection, which was removed by a recent erosion episode from all but the center of the structure.Structures formed by the impact of extraterrestrial bodies are very rare throughout much of Europe, because such structures are neither well preserved nor displayed in young mountain belts or sedimentary basins. However, northern Europe has several ascertained structures of this kind (Svensson &Wickman, 1965;Svensson, 1968;Bruun &Dahlman, 1982;Kala et al., 1984;Flodén et al., 1986;Wickman, 1988). Unfortunately, the hitherto known structures are either poorly preserved or hidden by younger deposits. We are reporting the discovery of a well-preserved exposed and accessible impact structure that has escaped the notice of geologists although important features of it have been described and puzzled over by generations of researchers (Wiman, 1900;Hadding, 1927;Thorslund, 1940;Lindström et al., 1983).The structure is located in the Lockne area to the south of Östersund in central Sweden. It has a diameter of 7 km and its center is near Tramsta on the northwest shore of Lake Locknesjön (Fig. 1). Its middle is covered by folded Lower to Middle Ordovician Orthoceratite Limestone with the sheared Lower Ordovician Töyen Shale at its base. This local expanse of deformed rock is the remainder after erosion of an extensive nappe of overthrust rocks emplaced during the Caledonian orogeny. The good preservation of the impact structure is due to the nappe cover, which had to be removed before erosion could attack the underlying structures.The rim of the impact crater is outlined by a wall of strongly shattered fragments of Proterozoic crystalline rocks (Fig. 2), which formed the local bedrock (Strömberg et al., 1984) at the time of impact. The rim wall is best preserved along the western part of the structure. It was referred to as »arkose-like breccia« byThorslund (1940), who interpreted it as the result of continental weathering, but the components rather show evidence of intense crushing than of weathering (Simon, 1987a). The »arkose-like breccia« does not contain components derived from the lower Palaeozoic deposits of the area. 相似文献
Summary Pre-Variscan basement in southern Poland is poorly exposed and thus known mostly from subsurface data. The availability of the latter is reviewed for terrains located between the Sudetes and the East European Platform. In these terrains the following relationships have been documented: Cadomian granitoids capped by Variscan flysch, Palaeozoic platform strata, Palaeozic folded and partly thermally altered successions, and low-grade metamorphic rocks overlain by Middle Cambrian strata. In view of their interrelationships the location of the Avalonia-Baltica suture in southeastern Poland is uncertain. 相似文献
Sediments of 56 salt lakes from Romania were studied enzymologically. The following 7 enzymatic and nonenzymatic catalytic activities have been measured: phosphatase, H2O2-splitting in nonautoclaved (catalase) and autoclaved samples, TTC reduction in nonautoclaved (dehydrogenase) and autoclaved samples, without or with glucose addition. A formula is proposed for the evaluation of the enzymatic potential of salt lake sediments or other habitats. A hierarchy of the studied lakes has been established on the basis of the enzymatic potential of their sediments expressed as enzymatic indicator. 相似文献
Can a sense of ownership over constantly changing urban places be generated through pedestrian exploration and everyday digital media practice? This paper begins with the author’s visit to the city of Adelaide, where a chance encounter – an intriguing sign painted on the wall of a city building – led to a hunt through the city for ghost signs, the remnants of old hand-painted advertisements. This spontaneous activity, combined with the online exploration and image sharing that followed, generated a renewed feeling of connection to, and ownership over, an erstwhile familiar locale. The experience is analysed through the work of theorists investigating change and belonging in modern cities including Guy Debord, Doreen Massey, Michel de Certeau, Andreas Huyssen, and Mark Crinson, as well as the contemporary growth in both politically inspired urban exploring (“Urbex” or “place hacking”) and the digital documentation and sharing of ghost signs and other urban ephemera. 相似文献