Projet de thèse en Sciences de la Terre et de l'environnement
Sous la direction de Yves Gueguen et de Jérôme Fortin.
Thèses en préparation à Paris Sciences et Lettres en cotutelle avec l'University of Petroleum , dans le cadre de Sciences de la Terre et de l'environnement et physique de l'Univers Paris , en partenariat avec LABORATOIRE DE GEOLOGIE DE L'ECOLE NORMALE SUPERIEURE (laboratoire) et de Ecole normale supérieure (établissement de préparation de la thèse) depuis le 01-09-2016 .
Experimental and theoretical studies for reservoir rocks at different frequency bands
Attenuation and dispersion can be caused by a variety of physical phenomena. Of particular interest to exploration geophysics is inelastic attenuation and dispersion of body waves resulting from the presence of fluids in the pore space of rocks[25-26]. Understanding the effects of pore fluid on elastic properties of sedimentary rocks is important for interpreting seismic data obtained for reservoirs that contain various fluids. It is commonly accepted that the presence of fluids in the pore space of rocks causes attenuation and dispersion. Seismic waves bring out subsurface rock and fluid information in the form of travel time, reflection amplitude, and phase variations. One of the ultimate goals of exploration seismology is to delineate and map pore fluids and their type and distribution in petroleum reservoirs. To achieve this goal, seismic data has to be able to resolve the compressibility contrasts among different pore fluids in the reservoir. As a result, seismic properties of pore fluids have to be fully understood. It has been demonstrated (Batzle et al., 2006), that mobility of pore fluids in rocks, which is defined as the ratio of rock permeability to fluid viscosity, ensures fluid pressure deviations amongst the pores when a seismic wave passes. As a result the seismic properties can be significantly influenced by the ability of fluid to move within the pores. For the tight sandstones with low-mobility fluid the pore pressure can be out of equilibrium even at seismic frequencies. However, most laboratory measurements are limited to ultrasonic techniques which operate in the megahertz range. Literature on seismic-frequency laboratory measurements of the acoustic properties of reservoir rocks saturated with fluid having low mobility is relatively sparse. We will study attenuation and dispersion for water-, brine- and glycerol- saturated tight sandstones in the frequency range of 10-3 Hz to 100 Hz and analyze whether the Gassmann theory can be applicable to the rocks saturated with low-mobility fluids even within the seismic band. Furthermore, we can demonstrate the effect of fluids on elastic properties for tight sandstones and provide theoretical basis for fluid identification in tight sandstone reservoirs.