Experimental Investigation of Factors Influencing PVT Behavior in CO2-Oil-Brine System

Abstract

To clarify the driving mechanisms of carbon capture, utilization, and storage (CCUS), phase behaviors in bulk CO 2 -oil-brine system is inevitably foundational investigation. In this study, we conducted pressure-volume-temperature tests under singlevariable control in laboratory with in-situ crude oil and synthetic brine samples. First, constant composition expansion tests were designed to examine saturation pressure between CO 2 and oil phases with varied CO 2 mole concentration and temperature, respectively. Meanwhile, as a major mechanism for carbon storage, CO 2 solubility in brine and oil was then measured with changing pressures at a specific reservoir temperature. Growth of the saturation pressure was constantly detected with increasing CO 2 mole concentration and temperature, respectively. With sufficient CO 2 guaranteed during the tests, we found that CO 2 solubility in tested liquids was strengthened by the pressure increase as expected. Moreover, within the same pressure range, incremental CO 2 solubility in oil was about ten times larger than that in the brine, which indicated potentially underestimated CO 2 storage capacity in depleted oil reservoirs..