Data assimilation in reservoir modeling often involves model variables that are multimodal, such as porosity and permeability. Well established data assimilation methods such as ensemble Kalman filter and ensemble smoother approaches, are based on Gaussian assumptions that are not applicable to multimodal random variables. The selection ensemble smoother is introduced as an alternative to traditional ensemble methods. In the proposed method, the prior distribution of the model variables, for example the porosity field, is a selection-Gaussian distribution, which allows modeling of the multimodal behavior of the posterior ensemble. The proposed approach is applied for validation on a two-dimensional synthetic channelized reservoir. In the application, an unknown reservoir model of porosity and permeability is estimated from the measured data. Seismic and production data are assumed to be repeatedly measured in time and the reservoir model is updated every time new data are assimilated. The example shows that the selection ensemble Kalman model improves the characterisation of the bimodality of the model parameters compared to the results of the ensemble smoother.
The central-western and the eastern Southern Alps are separated by the triangular shaped Adige embayment, which belongs to stable Adria and was the site of pelagic sedimentation from the Tithonian through Maastrichtian. The first part of this study presents paleomagnetic results from the Tithonian–Cenomanian Biancone and Turonian–Maastrichtian Scaglia Rossa formations sampled at 33 geographically distributed and biostratigraphically dated localities.The new and high quality paleomagnetic results from the Adige embayment are then combined with coeval paleomagnetic directions from autochthonous Istria (Márton et al., 2008), which also belongs to stable Adria. The combined data set (which for the Late Albian–Maastrichtian time period is constructed similarly to the synthetic African curve by Besse and Courtillot, 2002, 2003) reveals an important tectonic event (Late Aptian–Early Albian) characterized by 20° CCW rotation and sedimentary hiatus.Comparison between paleomagnetic declinations/inclinations expected in an African framework (i.e. with the assumption that Adria is still an African promontory) leads to the following conclusions. The time-distributed Tithonian and Berriasian (150–135 Ma) paleomagnetic directions exhibit the “African hairpin” with an inclination minimum and a sudden change from CW to CCW rotation at 145 Ma. Concerning the younger ages, the declinations for Adria continue to follow the African trend of CCW rotation till the end of Cretaceous. However, the Tithonian–Maastrichtian declination curve for stable Adria is displaced by 10° from the “African” curve as a result of two rotations. The first, an about 20° CW rotation of Adria with respect to Africa took place between the Maastrichtian and the mid-Eocene. During this time the orientation of Adria remained the same, while Africa continued its CCW rotation. The younger rotation (30°CCW) changed the orientation of Adria relative to Africa as well as to the present North. 相似文献
The Le Castella marine terrace is the smallest and youngest terrace of the Crotone area (southern Italy), and formed after a rapid marine ingression due to a glacio-eustatic rise outpacing the regional uplift of the area. The most prominent feature of the terrace deposits is a seaward-accreting clinoform about 10 m thick, inferred to be formed during forced regressive conditions. This prograding body is mostly composed of bioclastic material, and shows an internal complexity consisting of alternating oblique and sigmoid elementary units inferred to be produced mainly by changes of accommodation development. Foreset avalancing was due to sediment accumulation by gravity-flow processes, while topsets were characterized by the migration of medium- to large-scale dunes showing a unimodal palaeocurrent pattern, oblique with respect to the dip direction of the large-scale clinoform foresets. The Le Castella clinoform starts to develop from a topographic step on the basement due to tectonics, which also controlled the palaeoshoreline trend.The recognized stratigraphic and facies architectures, the palaeocurrent pattern, and the inferred palaeogeographic setting during deposition, all suggest that the Le Castella clinoform is an example of spit system attached to the mainland and accreted due to longshore transport. The present example contributes to establish criteria allowing the recognition of ancient spit systems, which still are poorly known and rarely documented in the pre-Quaternary geological record. 相似文献
The Monte Orfano Conglomerate (MOC), exposed in the foothills of the Southern Alps (northern Italy), is one of the few outcrops
of sediments documenting the Cenozoic tectonic evolution of the Alpine retrowedge. Calcareous nannofossil biostratigraphy
allowed us to constrain the upper part of the MOC, formerly attributed to the Early-Middle Miocene in the type-locality, to
the earliest Miocene (Neogene part of the NN1 nannofossil zone). A likely latest Oligocene age is therefore suggested for
the bulk of the underlying conglomerates, whose base is not exposed. Deposition of the MOC can be placed within the post-collisional
tectonic uplift of the Alps, documented in the Lake Como area by the Como Conglomerate (CC) at the base of the Gonfolite Lombarda
Group, and supports the correlation with Upper Oligocene clastic sediments cropping out further to the East, in the Lake Garda
and in the Veneto-Friuli areas (“molassa”). The remarkable difference in petrographic composition between the western (CC) and eastern (MOC) clastics deposited in
the Alpine retro-foreland basin highlights the synchronous tectonic activity of two structural domains involving different
crustal levels. Whilst the bulk of the CC, that straddles the Oligocene/Miocene boundary, records largely the tectonic exhumation
of the Alpine axial chain crystalline complexes, the coeval MOC consists of detritus derived from the superficial crustal
section (Triassic to Paleogene sedimentary rocks) of the Alpine retrowedge and constrains the onset of the post-collisional
deformation phase of the Southern Alps as not younger than the Late Oligocene. 相似文献
This is the first hydro-geochemical investigation carried out on the Roccamonfina Volcanic Complex groundwaters. The chemistry
of Roccamonfina waters is defined by water–rock and water–rock–gas interactions. In fact, interactions between rocks of the
first eruptive high-K formations and circulating groundwaters are recognized by high K concentrations. On the other hand,
inverse concentration of calcium versus alkali metals is related to two different rock interactions occurring in different
areas of the volcano: (a) within the caldera where groundwaters flow within latite and pyroclastic formations releasing calcium,
and (b) similarly at the base of the volcano where groundwaters flowing from surrounding carbonates got strongly enriched
in Ca. These geochemical processes are also associated with K (SE of caldera) and Mg/Ca (in sites located at the NE base of
the volcano) decrease. Completely different dynamics occurs at Riardo groundwaters (SE). Here waters are the result of a mix
between the Roccamonfina deep aquifer and the carbonate aquifer of the Riardo plain. Rich-CO2 emissions make these waters strongly mineralized. Minor elements show a similar geochemical behavior of major ions and are
crucial defining interactions processes. The evolution of Roccamonfina groundwaters is also evident along the simultaneous
enrichment of Ba, Sr, and Ca. Ba increase is the result of deep local carbonate alteration enhanced by CO2 emissions and, the lower Sr/Ca ratio, from 10 to 2 (ppb/ppm), is also due to the same process. In the light of our results
the Roccamonfina aquifer can be schematically divided into two main reservoirs: (a) a superficial aquifer which basically
follows the volcanic structure morphology and tectonics and (b) a deeper reservoir, originating within the oldest Roccamonfina
volcano ultra potassic lavas and then flowing into the carbonate aquifers of the neighboring plain. Eventually, the chemistry
of the Roccamonfina aquifer does not show any specific and visible pollution, contrary to what happens in the volcano surrounding
plains. In fact, only 14% of the samples we collected (206) show a NO3 content >30 mg/l. These sites are all located at the base of the volcano, near the plain. 相似文献
The Fore-Alps of western Veneto and Trentino regions belong to the central Southern Alps (NE Italy), in which there is little evidence of very fresh surface ruptures or surface faulting. This does not seem to match historical data about earthquakes, some of which have been very intense. The strong influence of the inherited structures makes it difficult to detect a direct link between morphotectonic features and present-day stress fields.In the present study, four areas (Orsara, Scandole, Naole and Soran) with surface faulting and surface rupture features were examined, and models of morphotectonic evolution are discussed. In the Lessini Mountains, the Orsara graben and Scandole ridge show examples of surface faulting and surface rupture, respectively, reactivating Paleogene normal faults and fractures. Within the Orsara graben, rocky bluffs displace the previous morphological features. The bluffs are some decimetres to some metres high and are practically devoid of evidence of either physical or chemical weathering; on the slopes above them are steep areas which may be interpreted as the remnants of previous strongly weathered bluffs. The Scandole ridge has many trenches, some with rocky walls, which may be the result of several episodes of morphotectonic rupture.In the Giudicarie Belt, the Naole and Mt. Soran surface faulting landforms are details within large frontal culmination walls of Neogene thrusts. The Naole ridge corresponds to the southeastern sector of Monte Baldo. Here, inside a fault angle valley, a sinuous scarp originating from surface faulting marks the base of the fault scarp slope. Ridge splitting is the expression of the backward migration of separation niches due to slope tectonics, also evidenced on the slope by several terrace-like features and by a lower belt of very thick slope breccias. On Mt. Soran, in the Gruppo di Brenta massif, the surface faulting scarp faces uphill, giving rise to a trench-like feature. Downvalley of the scarp, there is the niche of a large landslide dated to 3 kyears B.P.All these landforms are consistent with slope tectonic movements caused by intense earthquakes. Whereas the morphostructures in the Lessini Mountains are the result of responses by sensitive structures, the Naole and Mt. Soran features express the evolution of frontal culmination walls of thrusts, with clear evidence of present-day tectonic activity.On the basis of the weathering of the scarps and associated features, the relative seismotectonic episodes probably occurred between the Bronze and Middle Ages. 相似文献
A novel mechanism of stream development in coastal wetlands was observed in the form of interaction between the burrowing crab (Chasmagnathus granulata) and groundwater seepage. This process may eventually be further promoted by the predatory action of the white croaker fish (Micropogon opercularis). These so-called crab streams occur on the banks of major tidal channels in a salt marsh of the Bahía Blanca Estuary (Argentina). As the tide recedes, water is retained in the crab burrows on the marsh surface. The presence of lateral burrows produced by crab recruits promotes subterranean piping flow driven by the hydraulic head in the vertical burrow. Groundwater generally seeps along the tidal channel banks but is particularly prominent and concentrated where crab burrows perforate the banks. Where predatory attacks by the croaker fish enlarge the burrow mouths, the drainage rills become wider and deeper because more seeping water is collected in the shallow crater from where it is funnelled into the developing streams. The crab stream is then produced by water draining from the crab burrow mouth, acting initially by cut-back erosion and followed by forward erosion of the relatively unconsolidated muddy sediments. 相似文献
The Italian volcano, Vesuvius, erupted explosively in AD 79. Sanidine from pumice collected at Casti Amanti in Pompeii and Villa Poppea in Oplontis yielded a weighted-mean 40Ar/39Ar age of 1925±66 years in 2004 (1σ uncertainty) from incremental-heating experiments of eight aliquants of sanidine. This is the calendar age of the eruption. Our results together with the work of Renne et al. (1997) and Renne and Min (1998) demonstrate the validity of the 40Ar/39Ar method to reconstruct the recent eruptive history of young, active volcanoes. 相似文献