SwRI builds test rig for supercritical CO₂ well tools

At Southwest Research Institute’s new test rig, real downhole equipment is exposed to the same unusual form of carbon dioxide it may encounter beneath the ground. The system pumps supercritical CO₂ through components used in carbon capture, utilization and storage (CCUS), rather than relying only on water or air as stand-ins.

The distinction begins at roughly 87.8°F (31°C) and about 74 bar. Above those thresholds, CO₂ crosses its critical point and becomes a supercritical fluid, with liquid-like density but the ability to flow and penetrate somewhat like a gas. Small changes in pressure and temperature can also sharply alter its density, viscosity and other properties.

That matters for valves, screens and flow-control devices in a storage well. These components determine where and how quickly CO₂ enters a rock formation and help prevent unwanted fluids from moving through the well. SwRI’s rig measures pressure loss at constrictions such as valves, as well as flow rates and vibration, while helping assess long-term reliability. Jacqueline Manders, an assistant program manager in SwRI’s Thermofluids Section, said earlier testing with representative fluids “doesn’t really match how supercritical CO₂ behaves at depth.”

The physical tests are paired with a detailed 3D computer model. This computational fluid-dynamics approach divides the flow passages into many small regions and calculates velocity, pressure, turbulence and temperature. According to SwRI research engineer Raouf Tajik, the models also account for CO₂ property changes, heat transfer and flow turbulence; comparing predictions with test results is intended to validate the simulations.

In practical terms, the capability gives equipment designers a more realistic way to identify pressure drops, forces, vibration, erosion and control behavior before tools are used in a CCUS well. A model that matches the rig’s measurements could then examine other operating conditions without requiring a separate physical test for every case.