Density variations

The Duri core measurements show that the density of dry samples ranges from 1.54-1.67 g/cc. Assuming a grain density of 2.67 g/cc, and an average porosity of 35%, a 100% water saturated sample has a density of about 1.95 g/cc and does not vary with temperature. A partially water saturated sample with 10% initial gas saturation has a density of about 1.92 g/cc. The density of Duri oil varies with temperature linearly from 0.92 g/cc at 80 $^{\circ}$F to 0.83 g/cc at 350 $^{\circ}$F. A sample with 50% oil, 40% water and 10% gas has a density of about 1.90 g/cc at 100 $^{\circ}$F, and a density of 1.89 g/cc at 250 $^{\circ}$F. A sample with 10% oil and 90% gas (steam) at 350 $^{\circ}$F has a density of about 1.63 g/cc. As far as seismic impedance changes are concerned, the only case of interest is that of the steam zone, where density will decrease about 15% compared to initial reservoir conditions. All other scenarios cause negligible density changes, as described above.

 

Vptemp
Figure 11 P-wave velocity as a function of temperature and overburden pressure for three saturated samples from the upper P, lower P, and K formations (after Wang and Cates, 1994).

 

Vpsg
Figure 12 P-wave velocity as a function of gas saturation for a saturated sample at differential pressures of 200, 350 and 500 psia (after Wang and Cates, 1994).