eProcess has developed a proprietary multiphase model for sizing and predicting operation of the wellhead screen filter. The approach of the model is provided as follows, however key parameters are not listed to protect the confidentiality.

Pressure Drop and Fluid Throughput

• Use a modified Darcy-Weisbach equation with multiphase assumptions
• Divide the WSF into sub-regions, e.g., inlet, body, screen, annulus, outlet, etc.
• Calculate superficial and mixture velocities at each sub-region
• Calculate friction pressure loss at each sub-region
• Very the mesh size and gas-liquid rates to generate pressure drop curve

Separation Size and Collection Efficiency

• Very simple partition/collection model
• Calculate total mass flow of particles in inlet stream
• Distribute inlet mass flow into particle size range “bucket”
• All particles larger than screen mesh are captured and all particles smaller are passed through
• Sum all buckets larger than screen mesh to get collection mass and efficiency
• Sum all buckets smaller than screen mesh to get outlet mass flow rate

Multiphase Model

• Use mixing rules for fluid properties
• Calculate multiphase pressure drop. The limiting design factor is multiphase velocity through apertures or screen burst differential pressure.
• Calculate total solids collection efficiency. The key assumptions are level plug filling of screen cylinder mesh (not mesh blinding) and non-damaged screen with equal aperture size.
• Also assumes vertical screen operation
• Will be limited at high oil viscosity (upper boundary not known)

 References:

1. Rawlins, C.H., “Sand Management Methodologies for Sustained Facilities Operations”, Oil & Gas Facilities, Vol. 2, No. 5, October 2013, pp. 27-34. https://doi.org/10.2118/1013-0027-OGF

Next week I will cover WSF performance curve from the multiphase model and design factors.