Phase behavior and physical properties of petroleum reservoir fluids from acoustic measurements

An ultrasonic apparatus for measurements of the speed of sound in liquids and compressed gases has been constructed. The instrument has been tested in measurements on both water and a bottom-hole live reservoir crude oil sample. The speed of sound in the oil sample was measured at three temperatures between 335 and 402 K at pressures up to 70 MPa. Measurements made along an isotherm, starting in the single-phase region and proceeding with decreasing pressure, were shown to lead to a precise determination of the bubble point of the fluid. The prospects for obtaining the fluid density from sound speed measurements are discussed. We also describe the possibility of determining the oil viscosity from measurements of the sound absorption made with the same ultrasonic cell.