339 research outputs found
Lithofacies uncertainty modeling in a siliciclastic reservoir setting by incorporating geological contacts and seismic information
Deterministic modeling lonely provides a unique boundary layout, depending on the geological interpretation or interpolation
from the hard available data. Changing the interpreter’s attitude or interpolation parameters leads to displacing the
location of these borders. In contrary, probabilistic modeling of geological domains such as lithofacies is a critical aspect
to providing information to take proper decision in the case of evaluation of oil reservoirs parameters, that is, applicable
for quantification of uncertainty along the boundaries. These stochastic modeling manifests itself dramatically beyond this
occasion. Conventional approaches of probabilistic modeling (object and pixel-based) mostly suffers from consideration
of contact knowledge on the simulated domains. Plurigaussian simulation algorithm, in contrast, allows reproducing the
complex transitions among the lithofacies domains and has found wide acceptance for modeling petroleum reservoirs.
Stationary assumption for this framework has implications on the homogeneous characterization of the lithofacies. In this
case, the proportion is assumed constant and the covariance function as a typical feature of spatial continuity depends only
on the Euclidean distances between two points. But, whenever there exists a heterogeneity phenomenon in the region, this
assumption does not urge model to generate the desired variability of the underlying proportion of facies over the domain.
Geophysical attributes as a secondary variable in this place, plays an important role for generation of the realistic contact
relationship between the simulated categories. In this paper, a hierarchical plurigaussian simulation approach is used to construct
multiple realizations of lithofacies by incorporating the acoustic impedance as soft data through an oil reservoir in Iran.This research was funded by the National Elites Foundation of Iran in collaboration with research Institute Petroleum of Industry in Iran under the project number of 9265005
X-ray emission from the Sombrero galaxy: discrete sources
We present a study of discrete X-ray sources in and around the
bulge-dominated, massive Sa galaxy, Sombrero (M104), based on new and archival
Chandra observations with a total exposure of ~200 ks. With a detection limit
of L_X = 1E37 erg/s and a field of view covering a galactocentric radius of ~30
kpc (11.5 arcminute), 383 sources are detected. Cross-correlation with Spitler
et al.'s catalogue of Sombrero globular clusters (GCs) identified from HST/ACS
observations reveals 41 X-rays sources in GCs, presumably low-mass X-ray
binaries (LMXBs). We quantify the differential luminosity functions (LFs) for
both the detected GC and field LMXBs, whose power-low indices (~1.1 for the
GC-LF and ~1.6 for field-LF) are consistent with previous studies for
elliptical galaxies. With precise sky positions of the GCs without a detected
X-ray source, we further quantify, through a fluctuation analysis, the GC LF at
fainter luminosities down to 1E35 erg/s. The derived index rules out a
faint-end slope flatter than 1.1 at a 2 sigma significance, contrary to recent
findings in several elliptical galaxies and the bulge of M31. On the other
hand, the 2-6 keV unresolved emission places a tight constraint on the field
LF, implying a flattened index of ~1.0 below 1E37 erg/s. We also detect 101
sources in the halo of Sombrero. The presence of these sources cannot be
interpreted as galactic LMXBs whose spatial distribution empirically follows
the starlight. Their number is also higher than the expected number of cosmic
AGNs (52+/-11 [1 sigma]) whose surface density is constrained by deep X-ray
surveys. We suggest that either the cosmic X-ray background is unusually high
in the direction of Sombrero, or a distinct population of X-ray sources is
present in the halo of Sombrero.Comment: 11 figures, 5 tables, ApJ in pres
Performance of the CMS Cathode Strip Chambers with Cosmic Rays
The Cathode Strip Chambers (CSCs) constitute the primary muon tracking device
in the CMS endcaps. Their performance has been evaluated using data taken
during a cosmic ray run in fall 2008. Measured noise levels are low, with the
number of noisy channels well below 1%. Coordinate resolution was measured for
all types of chambers, and fall in the range 47 microns to 243 microns. The
efficiencies for local charged track triggers, for hit and for segments
reconstruction were measured, and are above 99%. The timing resolution per
layer is approximately 5 ns
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