Pore‐scale investigation on stress‐dependent characteristics of granular packs and the impact of pore deformation on fluid distribution

Understanding the effect of changing stress conditions on multiphase flow in porous media is of fundamental importance for many subsurface activities including enhanced oil recovery, water drawdown from aquifers, soil confinement, and geologic carbon storage. Geomechanical properties of complex porous systems are dynamically linked to flow conditions, but their feedback relationship is often oversimplified due to the difficulty of representing pore‐scale stress deformation and multiphase flow characteristics in high fidelity. In this work, we performed pore‐scale experiments of single‐ and multiphase flow through bead packs at different confining pressure conditions to elucidate compaction‐dependent characteristics of granular packs and their impact on fluid flow. A series of drainage and imbibition cycles were conducted on a water‐wet, soda‐lime glass bead pack under varying confining stress conditions. Simultaneously, X‐ray micro‐CT was used to visualize and quantify the degree of deformation and fluid distribution corresponding with each stress condition and injection cycle. Micro‐CT images were segmented using a gradient‐based method to identify fluids (e.g., oil and water), and solid phase redistribution throughout the different experimental stages. Changes in porosity, tortuosity, and specific surface area were quantified as a function of applied confining pressure. Results demonstrate varying degrees of sensitivity of these properties to confining pressure, which suggests that caution must be taken when considering scalability of these properties for practical modeling purposes. Changes in capillary number with confining pressure are attributed to the increase in pore velocity as a result of pore contraction. However, this increase in pore velocity was found to have a marginal impact on average phase trapping at different confining pressures.     

Direct inversion of Young's and Poisson impedances for fluid discrimination

Seismic inversion with prestack seismic data such as amplitude variation with offsets (AVO) inversion is an important tool in the estimation of elastic parameters for predicting lithology and discriminating fluid in conventional or unconventional hydrocarbon reservoirs. The product of Young's modulus and density (Young's impedance, YI) and the product of Poisson ratio and density (Poisson ratio impedance, PI) show great potential in lithology prediction and fluid discrimination of unconventional resources such as shale gas or oil. The high quality requirements for prestack data in density inversion render the estimation of YI and PI arduous and inaccurate with a conventional prestack inversion approach. In this study, a direct AVO inversion approach is proposed to estimate YI, PI, and density directly from P‐wave seismic data. The linearized P‐wave reflectivity approximate equation in terms of YI, PI, and density is initially derived. Five models, including four typical AVO classes, are utilized to verify the accuracy of the derived linearized P‐wave reflectivity equation in comparison with the exact P‐wave reflectivity equation and the frequently used linearized reflectivity approximate equation involving P‐ and S‐wave velocities and density. Parameter sensitivity analysis illustrates that YI and PI can reasonably be estimated from P‐wave reflectivity if a decorrelation scheme is utilized in the inversion algorithm. In addition, a pragmatic AVO inversion using a Bayesian scheme is suggested for the direct inversion of YI and PI from prestack seismic data. Synthetic and field data examples demonstrate the feasibility of the proposed inversion approach in the estimation of YI and PI and show the potential of this approach in fluid discrimination.     

Fire Events,Violence and Abandonment Scenarios in the Ancient Andes: The Final Stage of the Aguada Culture in the Ambato Valley,Northwest Argentina

Understanding how archaeological sites are abandoned is a vital part of archaeology. This paper explores abandonment as a phenomenon in a worldwide context, particularly in relation to sites with evidence of fire, and with a special focus on the South-Central Andes. I evaluate the patterns from an area of the Argentinian Andes and discuss the disappearance of the Aguada Culture, one of the central cultures in Argentinian prehistory, using evidence from the core area the Ambato Valley. I conclude that environmental factors were not the sole or determining source of stress, but rather part of a social–environmental dimension in which several factors combined to push a society into a vulnerable situation. In terms of the abandonment of the Aguada settlements in the Ambato Valley, the study shows that frequent forest fires might have played a role, but based upon the regularity of such events as seen in the sediment history, it is unlikely that these were the only factor in the process of abandonment of the valley.     

Possible rheumatoid arthritis found in the human skeleton collected from the tomb of Joseon Dynasty,Korea, dating back to the 1700s AD

We report a possible rheumatoid arthritis (RA) case found in a Korean Joseon Dynasty (1392–1910) tomb encapsulated by a lime‐soil mixture barrier (LSMB). The tomb is thought to have been constructed during the 1700s AD (1760 AD by carbon dating). In our anthropological examination, joint destruction, erosion or fusion (signs of polyarthritis) were identified mainly in the peripheral skeleton. Especially in both sides of the wrist bones, severe destruction/joint fusion possibly caused by polyarthritis was observed. A similar polyarthritis pattern also was seen in the right foot bones, even though we failed to confirm this symmetry due to the missing left foot bones. Despite these findings, signs suggestive of polyarthritis are very rarely seen in axial bones, even though bony fusions are found in the atlanto‐occipital joint or thoracic vertebrae (TV) 9–10. By the osteological signs observed in this case, the individual, a female, might have been suffering from a very late stage of RA and died in her 40s, even though other forms of chronic arthritis could not be ruled out completely. Though the current case could not provide evidence to decisively settle the debates on the antiquity of RA, our report could be a stepping stone for forthcoming studies on RA cases found in East Asian countries. Copyright © 2009 John Wiley & Sons, Ltd.     

GEOCHEMICAL ANALYSIS OF THE SEDIMENTS IN AND AROUND AN EARLY NEOLITHIC WELL NEAR BRODAU,GERMANY*

The discovery of wells of the linear pottery culture since 1990 has led to new insights on the ability and needs of humans at this time. The still small number of about 20 wells in Europe, compared to the much greater number of known settlements of this period, led to the assumption that they were built for special purposes, other than the water supply for the whole village. Investigations on the origin of archaeosediments of a more than 7000‐year‐old and 4.2 m deep well from the linear pottery culture in north‐west Saxony, Germany were carried out by geochemical analysis to improve our knowledge of the building, the usage and the decay of this wooden construction. Special emphasis was put on the material around two 10‐week‐old piglets that were intentionally deposited in the construction pit. Three major units—the sediment in the well, the infilling of the construction pit and the surrounding gravels—influenced by lateral transport of fine clay could be identified and described.     

REFINING ESTIMATES FOR THE SEASON OF SHELLFISH COLLECTION ON THE PACIFIC NORTHWEST COAST: APPLYING HIGH‐RESOLUTION STABLE OXYGEN ISOTOPE ANALYSIS AND SCLEROCHRONOLOGY

Stable oxygen isotopes from estuarine bivalve carbonate from Saxidomus gigantea were analysed combined with high‐resolution sclerochronology from modern and archaeological shells from British Columbia, Canada, to determine the seasonality of shellfish collection from the archaeological site of Namu. The combination of high‐resolution sclerochronology and a micro‐milled sampling strategy for δ¹⁸O analysis permits a precise estimate of archaeological seasonality, because seasonal freshwater influxes and changes in temperature have dual effects on the δ¹⁸O value of the shell. Sclerochronological analysis identifies the timing and duration of growth that is temporally aligned to stable oxygen isotope results, since δ¹⁸O_shell appears to be strongly influenced by seasonal inputs of very low δ¹⁸O snowmelt‐water from adjacent coastal mountain ranges. The results show that shellfish were collected year‐round at this site over a 4000‐year period, and these data combined with other zooarchaeological lines of evidence support the interpretation of year‐round occupation.     

Perchta the belly‐slitter and her kin: a view of some traditional threatening figures,threats and punishments

In the contemporary folklore of Austria, Frau Perchta (active during the twelve days of Christmas) is depicted as the rewarder of the generous and the punisher of the bad. But the punishments she inflicts, such as ripping out a person's guts and replacing them with refuse, do not seem to fit the crime. This paper links Perchta's behaviour, and that of other bogeyman figures, to their historical context. Initially Perchta was the enforcer of communal taboos, hunting down those who spun on holidays or who failed to partake sufficiently in collective feasting (a propitious act designed to ensure future plenty). However, with the growing involvement of peasant women in the market economy (particularly for textiles), Perchta's role changed to the punisher of the lazy. Yet Perchta's previous roles survive, in attenuated form, in each new incarnation.     

Some Native Legends from Central Australia

LAMPS OF ANTHROPOLOGY. By JOHN MURPHY, D.Litt., D.D., Emeritus Professor of Comparative Religion in the University of Manchester. (M.U. Press, 1943, sm. oct, pp. ix + 179.) Reviewed by J. H. Hutton.

ANTHROPOMORPHISM AND MIRACLE. By ERLAND EHNMARK (Uppsala Universitets. Arsskrift 1039:2). Uppsala, A. B. Lundequistska Bokhandeln, and Leipzig, Otto Harrassowitz. Pp. vi + 230. Reviewed by H. J. R.

YORKSHIRE HOBS. By BRUCE DICKINS. Trans. Yorkshire Dialect Society, vol. 7, part 43. Pp. 9–23. 1942. Reviewed by Wilfrid Bonsor.