Suction and time effects on the behaviour of a reservoir chalk

peer reviewedOil reservoir rocks contain various immiscible fluids (oil, water and gas) and they are submitted to elevated temperatures in the oilfield. Hence, they exhibit a typical coupled behaviour where multiphysics and coupled Thermo-Hydro-Mechanical aspects are predominant. This paper presents some results from researches carried out within the PASACHALK 2 European funded collaborative research. In this research dedicated to subsidence problems in the North sea Ekofisk oilfield, the behaviour of a reservoir chalk containing two immiscible fluids (an organic non polar fluid and water) is considered within the framework of the mechanics of unsaturated soils (no temperature effects considered). In order to account for the mechanical coupled effects related to the two pore fluids, the oil-water suction was considered as an independent stress variable. The paper presents some experimental results describing the combined effect of suction and time on the isotropic compression behaviour of the chalk. A viscoelastoplastic constitutive model based on one hand on the Barcelona BBM elastoplastic model for unsaturated and on the other hand on Perzina’s approach of viscous behaviour of soils is also presented and validated against experimental evidence

Mechanical Behaviour of a Porous Chalk and Water/Chalk Interaction. Part I: Experimental Study

International audienceThis paper is the first part of a general work on the mechanical behaviour of a porous chalk and the effect of saturating fluid. It presents an experimental investigation of the behaviour of a porous chalk by taking into account the effects of saturating fluid. Two representative fluids are concerned: a wetting fluid (water) and a non-wetting fluid (oil). The laboratory-testing program includes two topics. At first, conventional hydrostatic and triaxial compression tests are carried out on samples, which are respectively saturated with water and oil. The sensitivity of chalk behaviour to saturating fluid is clearly shown. Secondly, specific water injection tests are conducted in which water is injected in chalk samples initially saturated by oil, under different hydrostatic and deviatoric stress conditions. A water induced plastic deformation is observed

Mechanical Behaviour of a Porous Chalk and Water/Chalk Interaction. Part I: Experimental Study

This paper is the first part of a general work on the mechanical behaviour of a porous chalk and the effect of saturating fluid. It presents an experimental investigation of the behaviour of a porous chalk by taking into account the effects of saturating fluid. Two representative fluids are concerned: a wetting fluid (water) and a non-wetting fluid (oil). The laboratory-testing program includes two topics. At first, conventional hydrostatic and triaxial compression tests are carried out on samples, which are respectively saturated with water and oil. The sensitivity of chalk behaviour to saturating fluid is clearly shown. Secondly, specific water injection tests are conducted in which water is injected in chalk samples initially saturated by oil, under different hydrostatic and deviatoric stress conditions. A water induced plastic deformation is observed

Mechanical Behaviour of a Porous Chalk and Water/Chalk Interaction. Part Ii: Numerical Modelling

This paper is the second part of a general work on the mechanical behaviour of a porous chalk and the effect of saturating fluid. It presents the development of an elastoplastic model with two yield surfaces to describe the chalk behaviour. The water induced plastic deformation observed experimentally is described by using an additional plastic potential, based on the behaviour jump between two material states of chalk saturated with two different fluids. A good correlation is obtained between numerical simulations and experimental data obtained in the experimental study presented in the first part

Analysis of the evolution of rock joints morphology with 2-D autocorrelation (variomaps)

International audienceWe describe the evolution of the topography of schist and granite joint replicas during schear tests. The 2-D autocorrelation maps of asperities heights, of wear and angularut are an efficient method to identify the topography anisotropy and to estimate the occured damages

Voltage Dependent Anion Channel transport calcium ions through biomimetic membranes

The mitochondrial outer membrane channel (VDAC), a central player in mitochondria and cell death, was reconstituted in polymer-supported phospholipid bilayers. Highly purified VDAC was first reconstituted in vesicles; channel properties and NADH-ferricyanide reductase activity were ascertained before deposition onto solid substrates. 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine/1,2-distearoyl-sn-glycero-3-phosphoethanolamine−poly(ethylene glycol)−N-hydroxysuccinimide mixed vesicles containing VDAC were linked onto amine-grafted surfaces (glass and gold) and disrupted to form a VDAC-containing polymer-tethered planar bilayer. Surface plasmon spectroscopy, fluorescence microscopy, and atomic force microscopy measurements ascertained the membrane thickness, fluidity, and continuity. VDAC reconstituted in bilayers efficiently transported calcium ions and was modulable by two channel blockers, 4,4‘-diisothiocyanatostilbene-2,2‘-disulfonic acid and l-glutamate. The novel setup may allow the study of the assembly of a polyprotein complex centered on VDAC and its role in mitochondrial biology, calcium fluxes, and apoptosis