37 research outputs found
Anisotropic permeabilities evolution of reservoir rocks under pressure: new experimental and numerical approaches
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Transport of <i>Sporosarcina pasteurii</i> in sandstone and its significance for subsurface engineering technologies
The development of microbially mediated technologies for subsurface remediation and rock engineering is steadily increasing; however, we are lacking experimental data and models to predict bacterial movement through rock matrices. Here, breakthrough curves (BTCs) were obtained to quantify the transport of the ureolytic bacterium, Sporosarcina pasteurii, through sandstone cores, as a function of core length (1.8–7.5 cm), bacterial density (4 × 10<sup>6</sup> to 9 × 10<sup>7</sup> cells/ml) and flow rate (5.8–17.5 m/s). <i>S. pasteurii</i> was easily immobilised within the homogeneous sandstone matrix (>80%) in comparison to a packed sand column (<20%; under similar experimental conditions), and percentage recovery decreased almost linearly with increasing rock core length. Moreover, a decrease in bacterial density or flow rate enhanced bacterial retention. A numerical model based on 1D advection dispersion models used for unconsolidated sand was fitted to the BTC data obtained here for sandstone. Good agreement between data and model was obtained at shorter rock core lengths (<4 cm), suggesting that physicochemical filtration processes are similar in homogeneous packed sand and sandstones at these lengths. Discrepancies were, however observed at longer core lengths and with varying flow rates, indicating that the attributes of consolidated rock might impact bacterial transport progressively more with increasing core length. Implications of these results on microbial mineralisation technologies currently being developed for sealing fluid paths in subsurface environment is discussed
Stress path dependent hydromechanical behaviour of heterogeneous carbonate rock
The influence of stress paths, representative of reservoir conditions, on the hydromechanical behavior of a moderately heterogeneous carbonate has been investigated. Multiscale structural heterogeneities, common for instance in carbonate rocks, can strongly alter the mechanical response and significantly influence the evolution of flow properties with stress. Using a triaxial cell, the permeability evolutions during compression and the effects of brittle (fracture) and plastic (pore collapse) deformations at yield, were measured. A strong scattering was observed on the mechanical response both in term of compressibility and failure threshold. Using the porosity scaling predicted by an adapted effective medium theory (based on crack growth under Hertzian contact), we have rescaled the critical pressures by the normalized porosity deviation. This procedure reduces efficiently the scattering, revealing in the framework of proportional stress path loading, a linear relation between the critical pressures and the stress path parameter through all the deformation regimes. It leads to a new formulation for the critical state envelope in the 'mean stress, deviatoric stress' diagram. The attractive feature of this new yield envelope formulation relies on the fact that only the two most common different mechanical tests 'Uniaxial Compression' and 'Hydrostatic Compression', are needed to define entirely the yield envelope. Volumic strains and normalized permeabilities are finally mapped in the stresses diagram and correlated
Apport des mesures de champs par corrélation d’images pour l’étude de la déformation de géomatériaux
International audienc
Hydromechanical behavior of heterogeneous carbonate rock under proportional triaxial loadings
International audienc
In-situ analysis of strain localization related to structural heterogeneities of carbonate rocks
The technique of Digital Image Correlation (DIC) has been applied to study the deformation of porous carbonate rocks subjected to uniaxial compression tests. The tests have been performed at two different scales: on cylinders of 10 cm high compressed with a standard press with digital images recorded by optical microscopy at a global and local scale and on smaller parallelepiped samples deformed inside a scanning electron microscope (SEM). The development of localization at different scales is thus recorded as well as the damage and compaction mechanisms in relation with the microstructural heterogeneities
In-situ analysis of strain localization related to structural heterogeneities of carbonate rocks
The technique of Digital Image Correlation (DIC) has been applied to study the
deformation of porous carbonate rocks subjected to uniaxial compression tests.
The tests have been performed at two different scales: on cylinders of 10 cm
high compressed with a standard press with digital images recorded by optical
microscopy at a global and local scale and on smaller parallelepiped samples
deformed inside a scanning electron microscope (SEM). The development of
localization at different scales is thus recorded as well as the damage and
compaction mechanisms in relation with the microstructural heterogeneities