Niels Bohr Institutet > Kalender - det sker på NBI > 2010 > Master Thesis: Morten ...

Master Thesis: Morten Kanne Sørensen

 Acoustic properties of two phase saturated porous media

in the contect of sonic log invasion correction

Abstract:

Sonic logs are important tools for subterraneous resource exploration. Sonic logs measure the velocity of elastic waves in the formations penetrated during drilling. Such information is applied for fluid identification and quantification, which is of obvious interest for oil exploration. Due to shallow penetration depth, sonic logs only sample the near wellbore region.
Due to the permeable nature of especially reservoir formations, fluids necessary for drilling invade the formation replacing the original fluid affecting an altered sonic log response. To counter this effect most efficiently an adequate model of the elastic response must be formulated .
Studies involving gas-water saturated samples have shown significant hysteresis of the velocities dependent on the invasion mechanics. Within the frame work of the Biot-Gassmann theory, bounds related to the saturation fraction and invasion properties have been placed on the velocities.
Based on experimental measurements on samples prepared with two fluid phase saturations this study have addressed the relevance of these bounds to such systems. Through these measurements and subsequent modelling repetitive breaching of the bounds have been observed raising the question of the validity of the model presently applied.
Through the results obtained in the study it is suggested that further integration of the pore network characteristics into the model is required.

Supervisors: Klaus Mosegaard and Ida Lykke Fabricius