Analysis of rock physics response of gas-bearing volcanic reservoir based on three-phase poroelastic theory

Abstract

Unlike previous theories with velocity and/or elastic modulus averaging, we use a three-phase porous rock physics model developed by Santos for analyzing the seismic response of two immiscible fl uids in saturated porous media. Considering reservoir reference pressure and coupling drag of two fl uids in pores, the effects of frequency, porosity, and gas saturation on the phase velocities of the P-and S-waves are discussed in detail under fi eld conditions. The effects of porosity and gas saturation on Vp/Vs are also provided. The data for our numerical experiments are from a sample of deep volcanic rock from Daqing. The numerical results show that the frequency dispersion effect can be ignored for deep volcanic rocks with low porosity and low permeability. It is concluded that for deep volcanic rocks the effect of gas content in pores on Vp/Vs is negligible but the effect of porosity is signifi cant when there is a certain amount of water contained in the pores. The accurate estimate of lithology and porosity in this case is relatively more important.

A study of wavelet transforms applied for fracture identification and fracture density evaluation

“…Pan et al (2008) proposed the QAPF classification based on the IUGS and determined the volcanic rock mineral content using a genetic algorithm based on well logs. Wu et al (2008) analyzed the seismic response of two immiscible fluids in saturated porous media by the Santos three-phase porous rock physics model and proposed that in low-porosity and low-permeability igneous reservoirs the pressure and shear waves frequency dispersion could be ignored. Gas in the pores has little effect on the pressure and shear wave ratio but with a certain water saturation the porosity affect is signifi cant.…”