It is important to discuss the effect of permeability on recovery of oil from compacted sand reservoir through experimental results.
In Japan, there are many reservoirs which will end up with much residual oil because of their low permeabilities.
In our laboratory of early time, simple reservoir models made by packing silica sand in glass columns were used. In these columns, the recoveries were nearly 100% by microemulsion slugs possibly due to the reason that their permeabilities were about few darcy. Therefore it was found difficult to judge the effects of only microemulsion slugs on the recovery of oil in the columns.
On the other hand in natural reservoirs, sand strata are compressed by overburden pressure depending on their depth and their permeabilities are often much lower than those of the cores brought up to surface.
From these aspects, in this experiment, the relation between permeability and recovery was discussed by using the apparatus which was able to reduce the permeability of sand pack column by applying hydraulic
compression as large as overburden stress.
The contents of this paper are as follows.
1) The relation between permeability and confining pressure of sand pack column.
2) The influence recovery of oil in the compressed sand pack column by variation of viscosity of brine and polymer solutions.
3) The relation between permeability and recovery by water, polymer solution and microemulsion slug flooding.
The results of the experiments are summarized as follows.
1) Viscosity of displacement solution made much influence on recovery efficiency in reservoir model.
The most excellent result was shown when viscosity of polymer solution was same as that of crude oil.
2) It was better to keep the injection pressure as small as possible. When it was large, the fingering phenomenon appeared and the recovery was reduced.
3) The recovery efficiency was reduced by permeability reduction in every flooding.
4) In microemulsion flood, the recovery was about 100% in few darcy reservoir model, but it was about 80% in an artificial reservoir model of 100 milli-darcy.
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