Page 158 - Handbook Of Multiphase Flow Assurance

154 5. Flow restrictions and blockages in operations

Rock consolidation can be weakened in permafrost and Arctic wells by repeated hydrate
formation and dissociation over geologic time. Hydrate expands upon formation relative to
the water volume and crushes the rock pore matrix. Also if methanol is allowed to contact
rock near perforations, it dehydrates the rock and dissolves the cement holding consolidated
particles together. Sand production may hinder gas production from natural hydrate reser-
voirs if a complete physical and chemical understanding of the historic and technological
processes is not achieved.
Sand may also get produced from regular gas wells if well drawdown is too high.

Minimum transport velocity
If the liquid flow velocity falls below 1 m/s, solids are likely to accumulate in near-
horizontal pipelines.
The following single phase Newtonian fluids transport methods are available.

Thomas (1961).
Turian et al., 1987.
Oroskar and Turian, 1980.
Wicks, 1971.
Wicks (1968) presented sand transport study in 1 and 6 in. pipes with water, kerosene and
simulated crude oil. The model is only applicable to high sand concentrations up to 0.01
volume fraction and should not be used for subsea pipeline transport where solid loading is
−8
typically below 0.01 lb/bbl or approximately 10 volume fraction. However, it may be useful
for lines which already have sand deposited.
Thomas (1961) indicates that solids are less likely to settle at Reynolds>36,000.
The work by Bbosa et al. (2017) extends the transport velocity prediction method to
non-Newtonian slurry.
Multiphase transport models were presented by.

King et al., 2001.
Al-lababidi et al., 2012.
Ibarra et al., 2014.
Yan (2010) presents results of sand transport study in multiphase 2, 3 and 4 in. pipes in-
clined from 0 to 20°.
Sand transport in vertical flow has multiple technology areas to rest on such as catalyst
fluidized bed models, drill cuttings transport.
One of the easier methods to estimate sand transport velocity is to find sand falling veloc-
ity in a fluid.
Vertical velocity in gas is a free fall velocity with gas resistance and depends on particle
drag coefficient and cross-sectional area, and on gas density.

V _ particle = 2 ( × mass _ particle× g/ densitygas× C _drag Area particcle)) 05 .
(
×
_
_
As sand particles are rough and irregularly shaped, C_drag is usually 1.15 or higher at high
Re > 100. At low flow velocities the Stokes' solution gives C_drag = 24/Re.