New potential hydrocarbon source-rocks in the Lower Eocene Metlaoui Formation (Central-Northern Tunisia, Northern Africa)

Significant quantities of organic matter accumulated and were preserved in central-northern Tunisia during the Ypresian (Early Eocene). The organic geochemical characterization of the organic-rich facies of the Ypresian Metlaoui Formation (Ousselat and Es-Sfeïa sections) shows their significant potential as source rocks and increases interest in the Central-Northern Tunisia oil play. The TOC content in these rocks ranges from 0.09 to 3.71% suggesting their petroleum potential, whereas their T max fluctuates from 429 to 439°C. These values and the predominance of the hetero compounds (NSO; 2-95%) point to low organic matter maturation. The diverse maturity levels reported for these organic-rich rocks never reached the conventional oil window peak stage and resulted from their different locations within the basin. The HI values and the high saturate concentrations (1-91%) compared to aromatics (1-33%), as well as the predominance of short-chain n-alkanes centered atn-C18 and n-C20 are indicative of unequivocal type-II kerogen. The fluctuation of the pristane/phytane ratio (0.97-2.53) records changes of the basin redox conditions, which mainly evolved around the sub-oxic range

New potential hydrocarbon source-rocks in the Lower Eocene Metlaoui Formation (Central-Northern Tunisia, Northern Africa)

Significant quantities of organic matter accumulated and were preserved in central-northern Tunisia during the Ypresian (Early Eocene). The organic geochemical characterization of the organic-rich facies of the Ypresian Metlaoui Formation (Ousselat and Es-Sfeïa sections) shows their significant potential as source rocks and increases interest in the Central-Northern Tunisia oil play. The TOC content in these rocks ranges from 0.09 to 3.71% suggesting their petroleum potential, whereas their T max fluctuates from 429 to 439°C. These values and the predominance of the hetero compounds (NSO; 2-95%) point to low organic matter maturation. The diverse maturity levels reported for these organic-rich rocks never reached the conventional oil window peak stage and resulted from their different locations within the basin. The HI values and the high saturate concentrations (1-91%) compared to aromatics (1-33%), as well as the predominance of short-chain n-alkanes centered atn-C18 and n-C20 are indicative of unequivocal type-II kerogen. The fluctuation of the pristane/phytane ratio (0.97-2.53) records changes of the basin redox conditions, which mainly evolved around the sub-oxic range

Identification of nonlinear viscoelastic model

International audienceElastomers are widely used in several engineering applications such as aerospace, automotive and civil engineering applications thanks to their ability to undergoing high strains and strain rates in large temperature range. Several models have been developed in the literature to investigate those nonlinearities. In this work we expose a nonlinear viscoelastic model at finite strain for rubber-like materials based upon the theory of irreversible thermodynamic and the time strain superposition principle. The identification of several model's parameters is highlighted. A systematic identification procedure is used. First, we start by the identification of the shear relaxation module using relaxation tests at low levels of deformation and the identification tools in Abaqus software, then we identify the hyperelastic potential using equilibrium data of simple extension and pure shear experiment and a constrained linear least square minimization with Matlab software, finally we identify the reduced time function using monotonic tests of simple extension for different strain rates and the discretization of the behaviour law. The capacity of the model to predict the behaviour of the material is illustrated via the Cauchy stress relative error

On the nonlinear viscoelastic behavior of rubber-like materials: Constitutive description and identification

International audienceThe main concern of this paper is the development of a fully three dimensional viscoelastic model at finite strain to describe nonfactorizable behavior of rubber-like materials within the framework of rational thermodynamics and internal state variable approach such that the second law of thermody-namics in the form of Clausius-Duhem inequality is satisfied. The nonfactor-izable aspect of the behavior is introduced via a strain dependent relaxation times. The model is applied to describe the response of the isotropic Pip-kin multi-integral viscoelastic model and the BIIR material, several parameters involved are then identified using quasi-static and dynamic experiments thanks to a least-square minimization procedure performed with Matlab software. The proposed model is able to reproduce quasi-static experimental response and show an ability to predict the dynamic response of nonfactor-izable rubber-like materials in a wide range of strain

MODELING AND IDENTIFICATION OF A CLASS OF HYPERVISCOELASTIC MATERIAL BEHAVIOR

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Investigation of the nonlinear hyper-viscoelastic behavior of elastomers at finite strain: implementation and numerical validation

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