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
- 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.