The effects of porosity and permeability changes on simulated supercritical CO2 migration front in tight glutenite under different effective confining pressures from 1.5 MPa to 21.5 MPa

Abstract

AbstractDepending on rock pore compressibility, a change in effective confining pressure (ECP) can have a significant influence on supercritical CO2 (SC‐CO2) migration characteristics in natural reservoirs. In this study, a tight glutenite sample was used to conduct porosity/permeability measurements under different ECPs of 1.5, 5.5, 9.5, 13.5, 17.5 and 21.5 MPa. Then a SC‐CO2 drainage core flooding experiment, which was monitored using nuclear magnetic resonance (NMR) technique, was conducted at an ECP of 5.5 MPa. Measurement results show that the porosity and permeability of the sample were comparatively low (at an ECP of 1.5 MPa, 8.3% and 2.4 mD, respectively). With increasing ECP, the porosity/permeability decreased rapidly initially then more slowly at the larger ECP value. NMR results shows that SC‐CO2 preferentially displaced water creating flow channels inside the sample. At SC‐CO2 breakthrough, the average residual water saturation was 69.86%. Following breakthrough, SC‐CO2 continued to displace the water creating more substantial flow channels until they were sufficient to transport the SC‐CO2 at the fixed flow rate, resulting in a residual water saturation of 42.72%. A two‐dimensional computational model was then established based on these experimental results to simulate the fluid behaviors at an ECP of 5.5 MPa, and then the model was extended to different ECP values ranging from 1.5 to 21.5 MPa. Numerical simulation results show that SC‐CO2 displaced water in an inverted triangle‐like shape. Under different ECPs of 1.5, 5.5, 9.5, 13.5, 17.5 and 21.5 MPa, the simulated breakthrough times were 36.8, 44.6, 54.8, 56.4, 59.0 and 59.4 mins with an average SC‐CO2 saturation of 13.18, 16.71, 18.71, 19.72, 21.99 and 22.19%, respectively. SC‐CO2 breakthrough occurred quicker for lower ECP values resulting in a smaller SC‐CO2 saturation. Likewise, with larger ECP value, SC‐CO2 breakthrough occurred later, and a higher SC‐CO2 saturation was seen. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.