t-b A Petrophysical Study on the Influence of Effective Stress and Fluid Saturation on Acoustic Velocities in Sandstones Abbas Khaksar BSc. Mining Eng. (Tehran University) MSc. Petrol. Geol. & Geophy. (University of Adelaide) National Centre for Petroleum Geology & Geophysics Thesis submitted to the University of Adelaide in fulfillment of the requirement for the degree Doctor of Philosophy January 1999