Effects of pore fluid properties at high pressure and temperature on seismic response Joel Walls*, Rock Solid Images and Jack Dvorkin, Rock Solid Images and Stanford University Summary We use software from the National Institute of Standards and Testing (NIST) to assess the adiabatic bulk modulus and density of natural gas and brine at pressures up to 200 MPa and temperatures up to 200o C. The calculations are based on equations of state which are calibrated and verified by many experimental measurements. The results indicate that as pressure increases from the normal range of 20 to 50 MPa to the very high range of 150 to 200 MPa, the bulk modulus of methane may increase tenfold, from about 0.1 to about 1.0 GPa. The latter values are comparable to those for oil. For heavier hydrocarbon gases (ethane, propane, butane, and their mixtures) the modulus will be even higher.
