Q. Jiang et Rm. Butler, EXPERIMENTAL STUDIES ON EFFECTS OF RESERVOIR HETEROGENEITY ON THE VAPEX PROCESS, Journal of Canadian Petroleum Technology, 35(10), 1996, pp. 46-54
Citations number
6
Categorie Soggetti
Energy & Fuels","Engineering, Chemical","Engineering, Petroleum
In thermal recovery processes, heat can penetrate by conduction throug
h solids into low-permeability layers and shales. In the Vapex process
, vapour is confined to the pore spaces and its ingress into fine pore
s can be limited by capillarity. In steam processes, heat can penetrat
e relatively rapidly beyond the interface and mobilize the oil at dept
h; in Vapex, the diffusion of vapour is much slower and the thickness
of the mobilized oil is much less. Therefore, reservoir heterogeneity,
such as that created by low-permeability layers and shales, becomes m
ore important in affecting the performance of the Vapex process than w
ith SAGD because it is more difficult for the gas phase to penetrate t
he low-permeability regions. In this study, experiments were carried o
ut using a 2-D packed model to investigate the effects of low-permeabi
lity layers and lenses on Vapex. The model was packed in horizontal la
yers with two different sized sands. Crude from the Tangleflags North
field, Lloydminster, was extracted with butane. The effects of both co
ntinuous, low-permeability layers and discontinuous, low-permeability
lenses were investigated using different well configurations. The resu
lts using these models have been compared with those from uniformly pa
cked models. All experiments involving low-permeability layers gave lo
wer production rates than those involving uniformly high-permeability
packing. When the horizontal low permeability layers were continuous,
the production rate was even lower than that for a model uniformly pac
ked with the same low-permeability sand. A higher oil production rate
was found with discontinuous low-permeability lenses than with continu
ous layers. This is because the vapour chamber could rise around these
lenses to penetrate further into the high-permeability material above
; thus the oil could be drained concurrently from different heights. C
apillarity, due to interfacial tension between the oil and solvent vap
our phases, has a significant influence on the Vapex process. Its effe
cts are both beneficial, because of the increased contact area between
solvent vapour and oil, and detrimental, because of the resistance to
the rising of vapour fingers, on a pore scale, from a coarse sand lay
er into a fine sand layer. This latter effect changes the shape and gr
owth rate of the solvent chamber. A much higher residual oil saturatio
n was found in the fine sands than in the adjacent coarse sands.