1. INTRODUCTION Seismic methods involving techniques of surface seismic, sonic well-logging, vertical seismic profiling (VSP) and others, are among the primary tools in petroleum industrial, used both for reservoir characterization and for production monitoring. The seismic parameters of interest are intrinsic velocities and attenuation. Many studies have been conducted on changes in wave velocities associated with oil production [1, 2, 3, 4]. The experimental determination of attenuation is more difficult than the measurement of velocities [5, 6]. So there is very limited data in this area. Moreover, we need a massive set of robust laboratory measurements of the wave velocities and attenuations under various conditions of temperature, pore pressure, and fluid saturation to determine rock properties changes resulting from oil production. The purpose of this paper is to present data showing the pore fluids, pressure and temperature dependences of both P-wave and S-wave velocities and attenuations in poorly cemented porous sandstone. Ultrasonic measurements have been carried out. The important effect of pore fluid viscosity in glycerol-saturated samples and some dispersion mechanisms are discussed. 2. MATERIAL DESCRIPTIONS Cylindrical reconstituted samples are prepared from Fontainebleau sand, composed of mono-crystalline quartz sub-spherical grains [7]. This sand is moderately well sorted with a mean grain size of 250 microns (coarse grain). In order to reconstitute the sample, sand is poured in a stainless steel mould. Then a silicate solution is flood through precipitating silica on the contacts between grains. After several cycles of silicate solution flooding and oven-drying, the samples present a weak cementation. Samples have a porosity from 37 % to 40 % (deduced from results of Tomography scanner, MicroTomography scanner, Purcell tests and from weight measurements) and a high permeability of about 3 to 4.10 -12 m² (3 to 4 ARMA 11-578 Acoustic properties of poorly cemented sandstones under temperature and stress Doan, D.H. and Nauroy, J.F. IFP Energies nouvelles, 1-4 Av. du Bois Préau, 92852 Rueil-Malmaison Cedex, France Delage, P. and Tang, A.M. Ecole des Ponts ParisTech, 6-8 Av. Blaise Pascal, F-77455 Marne la Vallée Cedex 2, France Mainguy, M. TOTAL Office EB-181 CSTJF, Av. Larribau 64018 Pau Cedex, France Copyright 2011 ARMA, American Rock Mechanics Association This paper was prepared for presentation at the 45 th US Rock Mechanics / Geomechanics Symposium held in San Francisco, CA, June 26–29, 2011. This paper was selected for presentation at the symposium by an ARMA Technical Program Committee based on a technical and critical review of the paper by a minimum of two technical reviewers. The material, as presented, does not necessarily reflect any position of ARMA, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of ARMA is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgement of where and by whom the paper was presented. ABSTRACT: Most of thermal heavy oil recovery methods entails changes of pore fluid, pressure and temperature (pore fluid viscosity) which in turn induce complex changes in the elastic properties of reservoirs (in general, unconsolidated or weakly consolidated reservoirs). In this paper, laboratory measurements of velocities and attenuations at different conditions of temperature and stress were performed on weakly consolidated reconstituted sandstones saturated with various fluids (air, water and glycerol). The reconstituted sandstones are representative models of weakly cemented sandstone reservoirs with porous and highly permeable nature. The experimental results demonstrate the strong impact of different pore fluids on the compressional and shear wave velocities and attenuations. The influence of temperature and pressure and also wave dispersion mechanisms are discussed.