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is low, offset (distance to main facility) is long or there are flow
assurance problems so that the gas and liquids will not stably flow
to the surface.
Product is piped back through pipelines and risers to the
surface. The main choke may be located topside [15].

Injection
Wells are also divided into production and injection wells.
The former is for production of oil and gas, injection wells is
drilled to inject gas or water into the reservoir. The purpose of
injection is to maintain overall and hydrostatic reservoir pressure
and force the oil toward the production wells. When injected water
reaches the production well, this is called injected water break
through. Special logging instruments, often based on radioactive
isotopes added to injection water, are used to detect breakthrough.
Injection wells are fundamentally the same as production
wellheads other than the direction of flow and therefore the
mounting of some directional component such as the choke.

Artificial Lift
Production wells are free flowing or lifted. A free flowing
oil well has enough downhole pressure to reach a suitable
wellhead production pressure and maintain an acceptable well-
flow. If the formation pressure is too low, and water or gas
injection cannot maintain pressure or is not suitable, then the well
must be artificially lifted.
For smaller wells, 0.7 MPa (100 PSI) wellhead pressure
with a standing column of liquid in the tubing is considered a rule-
of-thumb to allow the well to flow. Larger wells will be equipped
with artificial lift to increase production even at much higher
pressures. Some artificial lift methods are:

Rod Pumps
Beam pumping, or the sucker-rod lift method, is the oldest
and most widely used type of artificial lift for most wells. A
sucker-rod pumping system is made up of several components,
some of which operate aboveground and other parts of which

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