Page 36 - Primer on Enhanced Oil Recovery

Basic physical and chemical 3

concepts

Abstract

In order to extract oil from a formation we need to be able to displace reservoir fluids
into the production well and move them to the surface. On the first place we need to have
or be able to create driving force, either utilize gravity or to have pressure differential,
which might eventually move our fluids, hopefully containing hydrocarbons, into the pro-
duction well. On the second place, for the fluid to flow it needs the interconnected chan-
nels (openings, interconnected pores) up to the production well. How fast the fluid flow
depends on its viscosity, which is an indication of the liquid “internal friction”, size and
concentration of interconnected pores and physical interactions between fluids and the
formation stone.

In order to extract oil from a formation we need to be able to displace reservoir
fluids into the production well and move them to the surface. On the first place we
need to have or be able to create driving force, either utilize gravity or to have pres-
sure differential, which might eventually move our fluids, hopefully containing
hydrocarbons, into the production well. On the second place, for the fluid to flow it
needs the interconnected channels (openings, interconnected pores) up to the pro-
duction well. How fast the fluid flow depends on its viscosity, which is an indica-
tion of the liquid “internal friction”, size and concentration of interconnected pores
and physical interactions between fluids and the formation stone. One can immedi-
ately see that the reservoir fluids flow is affected by many variables and is very
complex process. Flow analysis is not made easier by the fact that many fluids
properties depend on temperature, pressure and even speed of flow. On the top of
all mentioned, there are significant heterogeneities in the formation, which include
both spatially irregular stone and reservoir fluids properties. The useful experi-
ment to analyze the flow should account for the significant part of the above and
predict how the flow would change with the deviation of foreseeable inhomogeneity
which can be encountered during extraction process.
The painted extraction picture is so enormously complex that the full analysis is
impossible. In the past the complexity was taken into the account very lightly or
ignored at all. Nowadays, fortunately enough, having much better understanding of
basic processes and computing power, we can make some assumptions, state some
parameters as constants and neglect some processes as insignificant. In the bold
terms all this will depend how much it will cost us to reasonably understand pro-
cesses or influences of various eventualities. And now much more we can get
(hydrocarbons and profit) if we would care about everything and try our best. It
Primer on Enhanced Oil Recovery. DOI: https://doi.org/10.1016/B978-0-12-817632-0.00003-7
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