Petrophysical basis

Spatial and temporal changes in pore pressure, temperature and fluid saturation in a reservoir during steam injection can cause dramatic changes in reservoir rock properties, e.g., Ito et al. 1989, Wang and Nur 1989. Varying rock properties during steamflooding can cause seismic wavefields to be distorted and scattered throughout affected regions of the reservoir, compared to unaffected regions. For example, large seismic impedance contrasts associated with steam zones can cause seismic reflections and diffractions, which can be used to image the expanding steam front. Additionally, large seismic velocity decreases associated with heated reservoir rock may be used to map the spatial progress of thermal fronts. In principle, detecting and measuring changes in the seismic response as a function of space and time can lead to a clearer picture of the manner in which steam injection is affecting fluid flow and physical states in the reservoir, and therefore may help to optimize the reservoir production strategy.