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Wellhead Screen-Filter – General Design and Operation (B-FSM-102)


The general design of the wellhead screen-filter consists of a pressure retaining vessel and a cylindrical screen insert.

Pressure Retaining Vessel

  • Designed to contain full operating pressure
  • Built to API-6A wellhead specifications at 5K, 10K, or 15K rating
  • Will contain full shut-in pressure and no PSV is required

Cylindrical Screen Insert

  • Held inside the pressure vessel and performs the sand separation duty
  • Typically made from 316 stainless steel
  • An example design is 15 cm (6”) diameter x 3 meter length = 50 liters sand hold-up volume
  • Common separation sizes are 100-400 micron aperture widths at 50 micron intervals
  • It is a wedge-wire type with inside-to-out flow (detailed in next post)


  • The wellhead screen-filter is installed upstream of the choke as a service tool and used to remove coarse solids from flowback
  • Operating pressure drops range from 10 psi (clean) to more than 200 psi (dirty)
  • This unit can operate fully from 0-100% gas void fraction
  • Installation requires 2 x 100% units – with one in operation and one on standby
  • Sand is removed by batch discharge from the standby unit

Comparison to Multiphase Desander (same as previous post)

  • The Wellhead Screen-Filter and Wellhead Desander are both used as a service tool during well flow-back and clean-up operations
  • The WSF is not used in permanent production operations. The multiphase desander in Wellhead or Wellstream version, are commonly installed as a permanent part of facilities to deal with long-term sand production.
  • Both devices work in multiphase or liquid-only flow.
  • The WSF has infinite turndown as the separation mechanism is not pressure drop dependent. The multiphase desander has a finite (~5:1 turndown) based on the flow-pressure relationship.
  • The WSF separate solids effectively down to 100-150 microns, while the multiphase desander can separate down to 15-20 microns.
  • The WSF has a 50-60 liter solids hold-up volume before backflush, while the multiphase desander has 150-300 liter solids accumulation volume.
  • The WSF requires 2 x 100% layout to allow flushing of one unit while the other is in operation. The multiphase desander stays online at all times during operation, even during solids flushing.
  • For the multiphase desander fluid viscosity has a directly proportional relationship with separation size, while the WSF maintains separation performance at all fluid viscosities. However, both units show increase pressure drop with increasing viscosity.


  1. Rawlins, C.H., “Separating Solids First – Design and Operation of the Multiphase Desander”, paper 185658-MS presented at the SPE Western Regional Meeting, Bakersfield, CA, 23-27 April, 2017. https://doi.org/10.2118/185658-MS

Next week I will cover fluid flow patterns and particle travel of the WSF.

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