Page 267 - Hydrocarbon

254 Artificial Lift

be able to shut-off either bore. The lateral can be isolated by closing the SSD. This is
achieved by slickline intervention. The original bore can be isolated by setting a plug
(by slickline again) in the tailpipe. It is also possible, and increasingly common, to
mix smart wells with multilaterals, thereby allowing for remote monitoring and
control of each lateral.

10.8. Artificial Lift

The objective of any artificial lift system is to add energy to the produced
fluids, either to accelerate or to enable production.
Some wells may simply flow more efficiently on artificial lift, others require
artificial lift to get started and will then proceed to flow on natural lift, others yet
may not flow at all on natural flow. In any of these cases, the total cost of the
artificial lift system must be offset against the gains. The total cost must include
CAPEX on the wells and facilities and the operating costs for running and
maintaining the equipment. Operating costs may be considerable, especially when
pumps have to be periodically replaced. Because artificial lift requires energy, there
is a clear link from the wells to the facilities and process engineering. Different
artificial lift systems require totally different sources of energy and the choice of an
artificial lift system may have a large effect on the surface facilities.
Artificial lift systems are mostly required later in a field’s life, when reservoir
pressures decline and therefore well productivities drop. If a situation is anticipated
where artificial lift will be required or will be cost-effective later in a field’s life, it
may be advantageous to install the artificial lift equipment up front and use it to
accelerate production, provided the increased revenues from the accelerated
production offset the cost of the earlier investment. In some other cases it may be
beneficial to install multiple artificial lift systems to cater for different wells, or to
change the artificial lift system during the life of the well to cater for the different
operating conditions. Typical examples are wells that are converted to electrical
submersible pumps (ESPs) later in life as water cut increases.
Lifting the fluids from the reservoir to surface requires energy. All reservoirs
contain energy in the form of pressure, in the compressed fluid itself and in the
rock, due to the overburden. Pressure can be artificially maintained or enhanced by
injecting gas or water into the reservoir. This is commonly known as pressure
maintenance. Artificial lift systems distinguish themselves from pressure maintenance
by adding energy to the produced fluids in the well; the energy is not transferred to
the reservoir.
The following types of artificial lift are commonly available today

Beam pump
Progressive cavity pump
Electric submersible pump (ESP)
Hydraulic submersible pump (HSP)
Jet pump
Continuous flow gas lift