Numerical Structural Screening of a High-Pressure Sand Concentrator for Pre-Foaming Base Fluid in CO2-Foam Fracturing

Mixing a proppant-laden base fluid with high-pressure CO2 can reduce its effective sand volume fraction, thereby impairing proppant placement and fracture conductivity. This study performs a numerical structural screening of the helical guide groove in a centrifugal–filtration sand concentrator intended for the pre-foaming base-fluid line upstream of the foam generator and operating against a 105 MPa outlet backpressure. The full-scale base geometry—an inner diameter of 500 mm, a concentration-zone length of 3500 mm, and 18 slotted-screen openings—was retained, while groove depth (10–40 mm), groove width (110–150 mm), and pitch (300–700 mm) were varied sequentially in 14 factor-level evaluations (12 unique geometries). Steady-state calculations were conducted in ANSYS Fluent 2022 R1 using an Eulerian–Eulerian two-fluid framework, the RNG k–ε turbulence closure, a constant apparent liquid viscosity of 0.040 Pa·s, and a compiled UDF-based phase-selective screen condition. CO2 was not included as a separate phase. Within the investigated ranges, increasing groove depth and width increased the sand volume fraction at the concentrated-fluid outlet, whereas pitch produced a pronounced inverted-U-shaped response. The best tested geometry had a pitch of 500 mm, a width of 150 mm, and a depth of 40 mm, yielding an outlet sand volume fraction of 54.05%. This value is 3.80 percentage points higher than the lowest-performing tested configuration (50.25%), corresponding to a relative increase of 7.56%; it is also 14.05 percentage points above the inlet value of 40.00% and 4.05 percentage points above the engineering target of 50.00%. The results provide comparative numerical evidence for groove-parameter selection; independent experimental validation remains required before field application.