The cold production process has increased primary heavy oil production and
has been applied with commercial success in the: Lloydminster area (Alberta
, Canada). In this process, the production of sand is encouraged in order t
o form high permeability channels (wormholes) within the formation. The pro
cess depends on the formation and flow of foamy oil into the wormholes as t
hese grow away from the wellbore and into the reservoir. The formation and
growth of a wormhole was visualized using a computed tomography scanner, in
an experiment in which oil Rowed through a horizontal sandpack and out an
orifice. The only drive mechanism was the formation and expansion of methan
e bubbles within the live oil. The pressure gradient at the tip of the worm
hole was approximately 1 MPa/m when it started to develop at the orifice. T
wo conditions appear necessary for wormholes to keep growing: (1) the press
ure gradient at the tip of the wormhole must be sufficiently large to dislo
dge the sand grains, (2) the pressure gradient along the wormhole must be l
arge enough to transport the sand from the tip to the orifice. The pressure
gradient at the tip of the wormhole was 2.9 MPa/m when it reached its maxi
mum length. This suggests that, although the pressure gradient at the tip w
as sufficient for erosion to occur, the sand could not be carried along the
wormhole causing the wormhole to stop growing. The pressure depletion expe
riment suggests that wormholes can easily develop in uncemented sand in the
field since the maximum oil production rate during wormhole growth (18 cm(
3)/day) was significantly lower than in the field. The minimum pressure gra
dient (11 kPa/m) necessary for sand transport along the wormhole is importa
nt in calculating the extent of wormhole growth in the field.