Temperature cycling and its effect on mechanical behaviours of highporosity chalks

Temperature history can have a significant effect on the strength of water-saturated chalk.In this study,hydrostatic stress cycles are applied to understand the mechanical response of chalk samples exposed to temperature cycling between each stress cycle,compared to the samples tested at a constant temperature.The total accumulated strain during a stress cycle and the irreversible strain are reported.Chalk samples from Kansas (USA) and Mons (Belgium),with different degrees of induration (i.e.amount of contact cementation),were used.The samples were saturated with equilibrated water (polar) and nonpolar Isopar H oil to quantify water weakening.All samples tested during 10 stress cycles with varying temperature (i.e.temperature cycled in between each stress cycle) accumulated more strain than those tested at constant temperatures.All the stress cycles were performed at 30 ℃.The two chalk types behaved similarly when saturated with Isopar H oil,but differently when saturated with water.When saturated with water,the stronger Kansas chalk accumulated more total strain and more irreversible strain within each stress cycle than the weaker Mons chalk.

WELL-POSEDNESS OF A COMPRESSIBLE GAS-LIQUID MODEL FOR DEEPWATER OIL WELL OPERATIONS

The main purpose of this paper is two-fold： （i） to generalize an existence result for a compressible gas-liquid model with a friction term recently published by Friis and Evje [SIAM J. Appl. Math., 71 （2011）, pp. 2014-2047]; （ii） to derive a uniqueness result for the same model. A main ingredient in the existence part is the observation that we can consider weaker assumptions on the initial liquid and gas mass, and still obtain an existence result. Compared to the above mentioned work, we rely on a more refined application of the estimates provided by the basic energy estimate. Concerning the uniqueness result, we borrow ideas from Fang and Zhang [Nonlinear Anal. TMA, 58 （2004）, pp. 719-731] and derive a stability result under appropriate constraints on parameters that determine rate of decay toward zero at the boundary for gas and liquid masses, and growth rate of masses associated with the friction term and viscous coefficient.

Behavioural Responses of <i>Crangon crangon</i>(Crustacea, Decapoda) to Reduced Seawater pH Following Simulated Leakage from Sub-Sea Geological Storage

Carbon capture and storage (CCS) in sub-sea geological formations is being developed and promoted to mitigate CO2 discharges to the atmosphere from point sources such as power stations. There remain some questions on the risks associated with the possible loss of gas from storage and the environmental harm this could pose to marine organisms associated with the sea bed in these regions. This study investigated the effect of exposing the common shrimp (Crangon crangon) to reduced pH conditions and presents the results of stepwise pH-reductions (0.2 pH units from pH 7 down to pH 6). Behaviour was monitored continuously throughout 8 hours of exposure. In three subsequent experiments we could show a consistent and repeatable behavioural response pattern consisting of immediate avoidance reactions expressed as “shooting behaviour” following each pH-reduction every hour. The animals responded in a rapid manner to the shifts at all pH values, suggesting that these animals are sensitive to even relatively small changes. The results indicate that repeated acute pH-stress caused by CO2-leakage from carbon storage sites might affect the behaviour and subsequent fitness of natural populations of common shrimps. Changes in behaviour are likely to lead to increased predation on these animals and migration away from affected areas.

A Numerical Study of Characteristic Slow-Transient Behavior of a Compressible 2D Gas-Liquid Two-Fluid Model

The purpose of this paper is to gain some insight into the characteristic behavior of a general compressible two-fluid gas-liquid model in 2D by using numerical computations.Main focus is on mass transport phenomena.Relatively few numerical results in higher dimensions can be found in the literature for this two-fluid model,in particular,for cases where mass transport dynamics are essential.We focus on natural extensions to 2D of known 1D benchmark test cases,like water faucet and gas-liquid separation,previously employed by many researchers for the purpose of testing various numerical schemes.For the numerical investigations,the WIMF discretization method introduced in[SIAM J.Sci.Comput.26(2005),1449]is applied,in combination with a standard dimensional splitting approach.Highly complicated flow patterns are observed reflecting the balance between acceleration forces,gravity,interfacial forces,and pressure gradients.An essential ingredient in these results is the appearance of single-phase regions in combination with mixture regions(dispersed flow).Solutions are calculated and shown from early times until a steady state is reached.Grid refinement studies are included to demonstrate that the obtained solutions are not grid-sensitive.