CO2–BRINE CORE FLOODING IN SANDSTONE FROM ORDOS BASIN UNDER X-RAY CT

To understand how does the injected CO₂ migration could help increase the available storage capacity in geologic formations, this paper reports a series of experiments of core flooding. To examine the effects of CO₂ migration pathways in geologic formations, our team have developed a core flooding test of displacing water in porous media with CO₂. The samples were obtained from the Ordos Basin, all formations being used for carbon capture and storage(CCS) pilot—Shenhua CCS demonstration project, with a capacity of 100,000 tones CO2 per year, which is the first fully process of CCS in saline reservoir in China. All flooding tests in this paper were performed in the medical CT scanner facility with Hassler-style core holder and ancillary apparatus. The medical CT is capable of operating at 140KV and 400mA, has a maximum resolution in the x-y plane (perpendicular to the core length) of 0.25mm and 1 mm along the axial direction. The system with four Isco pumps and a Hassler-style core holder that was used to contain the core, while applying both axial and radial pressure to the core during flooding tests.

Experiments were performed over several weeks by injecting CO2-saturated brine through samples. At the same time the samples were scanned with a computed tomography (CT) scanner at regular intervals (0.5mm) during the course of the experiments. Injection flow rates and temperature of the system were varied for each experiment. For the first test of every sample, the helium gas as the flow constant pressure 100 psi at different flow rates (0.72ml/min, 1.48 ml/min, 2.96 ml/min ) was test. Then the brine and CO2 as the flow constant pressure 2000 psi at different flow rates (1.72ml/min, 3.43ml/min, 5.13 ml/min) was test. The constant injection pressure resulted in unstable flow patterns. For the subsequent tests a constant injection rate was set with the Isco pumps and with additional software controls to ensure the pore pressure did not exceed the confining pressure (2500 psi). As long as the injection pressure was less than the confining pressure the flow rate was constant for a constant delta pressure. When the injection pressure increased to a value close to the confining pressure the flow rate was decreased to ensure safe operations.

A review of the findings in common among the studied is presented in the final sections of this paper.