Page 92 - Well Control for Completions and Interventions

Well Construction and Completion Design 83

2.2.12 Multilateral Wells
A multilateral well is a well with one or more branches coming off the
main bore. Because of the difficultly in drilling and completing multilateral
wells, they are still relatively rare. The main reason for drilling a multilateral
well is to increase reservoir exposure. For example, in the Troll Field, Statoil
have drilled a well that uses five branches to expose 14,200 m (46,590 ft) of
producing formation. Whilst there are clear benefits to having such exten-
sive reservoir exposure from a single wellbore, the drawbacks are equally as
obvious. Multilateral wells are complex; difficult to drill and complete. Any
requirement to control production from a lateral means complex comple-
tions. The ability to carry out mechanical interventions is normally limited
to the main bore, unless very complex junctions are installed. There are also
additional well control problems associated with some multilateral wells—
for example,abullhead maybethe onlyviableoption in some wells,since
it is usually not possible to circulate below the junction (Fig. 2.13).

Figure 2.13 Multilateral completion.