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Multiphase Desander – Operating Boundaries (B-FSM094)

The following guidelines provide the operating boundaries for the multiphase desander.

Fluids and Pressure

Pressure Drop

  • Minimum 3-5 psid based on GVF
  • Maximum set at 25-75 psid for wear life
  • Will impose back pressure on artificial lift wells

Flow Conditions

  • Operation from 0-100% GVF
  • Turndown: per insert 3:1 liquid only, 5:1 multiphase, per vessel 20:1 by changing inserts

Slugging

  • Must stay within pressure drop range

Fluid Viscosity

  • Avoid oil with high liquid viscosity (>100 cP), low watercut, and low GVF

Solids and Particles

Particle Size

  • Maximum 1/3 smallest opening on insert (inlet or apex)
  • WH4: 9 mm WH10: 21 mm
  • WH6: 14 mm WH16: 34 mm
  • WH8: 18 mm WH20: 51 mm

Particle Concentration

  • Static operation based on apex flux limits
  • Example: 150 micron sand in water
  • WH4: 4000 ppmw (0.4%)
  • WH6: 6000 ppmw (0.6%)
  • WH8: 8000 ppmw (0.8%)
  • WH10: 10000 ppmw (1.0%)
  • Implementation of Apex Flux Balancing increases limit by order of magnitude
  • Accumulator volume and rate of isolation/discharge will be limiting factory at high solids concentration

Effects of Chemicals

Natural and Artificial Chemicals Present

  • Bad Chemicals – anything that increases viscosity, stabilizes emulsions, or allows oil to wet solids
  • Good Chemicals – anything that decreases viscosity, breaks emulsions, or removes oil wetting from solids
  • Flocculants will not work to “grow” particle size because shear forces break flocs

Multiphase desander application and mechanical requirements will be covered in the next article.

References

  1. Rawlins, C.H. 2017. “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.
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