En SEFI, unidos para alcanzar metas - Facultad de Ingeniería - UNAM

What is that?
It’s a pump!
Óscar R. Contreras Utrera
This lever system —conventional pumping
unit— is an artificial lift method;
it is additional equipment to the well
infrastructure, which gives additional energy
to the fluids produced by the reservoir from a
given depth
When an engineer thinks to put a well into
production it is expected to flow with its natural
energy. Because of the geology and the
processes that have given rise to the reservoir
—which is a stratigraphic trap— the hydrocarbons
are stored at high pressures and temperatures.
When drilling a well and then put it to produce
we creates a large pressure difference, where
the higher pressure is in the reservoir and the
lower is on surface. Thus fluids will satisfy the
mechanics laws and so will be transported from
downhole to surface.
However, after a certain period of time —which
varies depending on reservoir conditions and its
exploitation— the natural energy of wells is depleted
and although there are still hydrocarbons,
other methods are needed for recovery.
Their use allows us to maintain the differential
pressure required for bringing the oil, but this is
done artificially. Although they are so expensive
methods, often their application is profitable because
hydrocarbons volumes for being recoverable
will allow paying the used equipment.
If you have ever gone through a petroleum city
or you have seen film images about Texas desert,
you have probably noticed the presence of some
equipment like a hammer that moves from side
to side and possibly produce much noise. That
hammer arguably is a pump!
In fact, this equipment is a crank-balanced conventional
unit and it is a kind of artificial lift
method called sucker rod pumping. This artificial
lift method is normally seen in many places
because it is the oldest and sometimes the less
expensive.
In México, we can notice the presence of rod
pumping in Poza Rica City and around because
the wells have the necessary conditions for using
this mechanism, such as: low productivity index,
low sand production, enough pressure in
downhole, no paraffin accumulations and they
are not deviated wells or have low deviation.
However, there are other artificial lift methods
whose operating principles can be different but
their purpose is the same: raise the fluids to the
surface. It is noteworthy that each system must
be installed for specific conditions and to consider
several factors in its design: rock type, well
conditions, pressure, temperature, volume and
type of oil, etc. Also, the costs have to be evaluated
because the implemented method could be
not profitable.
Gaceta digital FI • No. 7 • Mayo, 2011
Contenido 25