Capillary End Effects in Reservoirs with Heterogeneous Wettability

Doklady Earth Sciences - A new type of capillary end effect in oil and gas reservoirs due to heterogeneous wettability has been justified. This type of capillary end effect is not related to the...     

Modeling Iceberg Drift in the Barents Sea from Field Data

The iceberg drift model is developed and used for simulating the iceberg drift trajectory in the Barents Sea. The model is forced by hydrometeorological characteristics obtained from ship observations. Original techniques for retrieving the sea-level slope gradient and surface velocity of currents are proposed, implemented, and validated using independent data. Thus, additional data were calculated from field data in order to use the iceberg drift model with the full set of external forces. This allowed improving the iceberg trajectory simulation and assessing the contribution of all forces that affect the iceberg drift. The iceberg drift calculations demonstrate that the drift characteristics are extremely sensitive to all external effects and the model parameters; therefore, the quality of input hydrometeorological data essentially affects the simulation of real iceberg trajectories.     

Holocene climate variability as derived from alkenone sea surface temperature and coupled ocean-atmosphere model experiments

Holocene climate modes are identified by the statistical analysis of reconstructed sea surface temperatures (SSTs) from the tropical and North Atlantic regions. The leading mode of Holocene SST variability in the tropical region indicates a rapid warming from the early to mid Holocene followed by a relatively weak warming during the late Holocene. The dominant mode of the North Atlantic region SST captures the transition from relatively warm (cold) conditions in the eastern North Atlantic and the western Mediterranean Sea (the northern Red Sea) to relatively cold (warm) conditions in these regions from the early to late Holocene. This pattern of Holocene SST variability resembles the signature of the Arctic Oscillation/North Atlantic Oscillation (AO/NAO). The second mode of both tropical and North Atlantic regions captures a warming towards the mid Holocene and a subsequent cooling. The dominant modes of Holocene SST variability emphasize enhanced variability around 2300 and 1000 years. The leading mode of the coupled tropical-North Atlantic Holocene SST variability shows that an increase of tropical SST is accompanied by a decrease of SST in the eastern North Atlantic. An analogy with the instrumental period as well as the analysis of a long-term integration of a coupled ocean-atmosphere general circulation model suggest that the AO/NAO is one dominant mode of climate variability at millennial time scales.     

A social scientist's perspective on the Census of Marine Life

Over 300 natural scientists in 53 nations are taking part in the Census of Marine Life (CoML) to investigate what lived, what lives, and what will live in the oceans. The CoML is a scientific experiment that is exploring the limits of ocean science. The paper discusses the potential applications of CoML research and the mechanisms by which the potential benefits can be measured and preserved. I recommend developing and integrating policy advisory committees with the natural science activities to both maximize the benefits of the research and to avoid unintended consequences.     

Geometrical spreading factor of head waves in cased and open boreholes

Factors (coefficients) of geometrical spreading of compressional and shear head waves are calculated for an impulse multipole source of elastic oscillations in boreholes. It is shown that the length of the logging tool (i.e., the distance between the source and the nearest receiver) used for sonic measurements and the velocities of elastic waves in the medium both contribute to the factor of geometrical spreading. For a high-velocity formation (the shear wave velocity in the rock is higher than the compressional wave velocity in the fluid that fills the borehole) and a sufficiently long sonic tool with a monopole source, the coefficient of geometrical spreading is approximated by asymptotic formula 1/Z [Roever et al., 1974; Krauklis and Krauklis, 1976], where Z is the length of the tool; i.e., the amplitude of the compressional head wave decreases proportionally to the distance between the source and the receiver. In acoustically soft formations, this approximation is inapplicable even for long tools with length Z > 4 m. Waveforms in cased boreholes have a significant frequency dispersion even in case of good-quality cementing, and the factor of geometrical spreading there depends considerably on the length of the tool and the elastic properties of the rocks.     

Radio-induced activity in galaxy pairs

The close proximity of a radio-loud active galactic nucleus (AGN) can trigger star formation in nearby objects containing gas if they are hit by a radio jet emerging from the active nucleus (as is observed, for example, in the case of Minkowski’s Object). The predicted frequency of such events is modest for close pairs of galaxies—of the order of several percent of all close (with separations of the order of several tens of parsec) pairs containing a radio AGN. A statistical study of this effect is carried out using the SDSS and FIRST surveys, by searching for spatially close pairs (projected separations <150 kpc, relative radial velocities <600 km/s) containing AGNs with radio jets. The frequency of galaxies with bursts of star formation, f _SF, and active nuclei f _AGN, in pairs either containing or not containing an AGN with radio jets are evaluated as functions of the separation of the galaxies in the pair. It is concluded that (1) the predicted effect should be of the order of 5%, falling off with increasing separation between the galaxies in the pair; (2) the observed values of f _SF and f _AGN and their dependences on the galaxy separation are consistent withmodel predictions, but the large uncertainties associated with the limited size of the studied sample hinders firm conclusions about the existence of radio-induced activity in close galaxy pairs; (3) further investigations using a larger volume of observational material are required, for example, using only photometric redshifts.     

Neogene gravity folds at the Yegor’evsk phosphorite deposit

At the Yegor’evsk phosphorite deposit, the beds lie horizontally, although peculiar folds are observable locally. Close to the present-day and Neogene river valleys, the phosphorite-bearing succession and the Lower Cretaceous beds acquire an appreciable tilt toward the river valley floor. Folds occur only in those places where the river valley downcuts Oxfordian clay to a considerable depth (down to 10 m or deeper). In such cases, the plastic clay is squeezed out under the load of overlying sediments into the valley wall and is removed with water. The overlying beds subside as a strip parallel to the river valley and make up a border that is folded down.