Abstract

We have performed a series of rock physics measurements under various simulate confining and pore pressure and temperature states to test the seismic response of two tight reservoir samples of the sedimentary basin of the St. Lawrence Lowlands to different CO\(_2\) phases. Results show that the seismic velocity and amplitude can be used to detect the CO\(_2\) phase transition. Laboratory measurements were used to calibrate a stochastic geological model that was used to generate synthetic seimograms reproducing the response to CO\(_2\) injection in the reservoir formations. The modeled CO\(_2\) injection scenario included 15 years of injection followed by 35 years of CO\(_2\) migration. Synthetic time-lapse seismograms were produced after 5, 15 and 50 years form the start of injection. Results show that substitution of brine by CO\(_2\) is responsible of a time-delay in the seismic traces despite very low reservoir permeabilities and porosities. A comparison between a classical blocky model and our stochastic model shows that the blocky model leads to a misinterpretation of the CO\(_2\) effect on the seismic response.
Keywords: CO\(_2\), ultrasonic measurements, seismic modeling, time-lapse VSP, low porosity sandstones, CO\(_2\) injection modeling