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Smart Wells and Techniques for Reservoir Monitoring 273

schedules. They found that by systematically optimizing the ICV setting in
injector and producer wells, the ultimate oil recovery was improved 3% by
reducing water injection by 8%, and economic value (NPV) was improved
2.3 times, compared with conventional completions.

7.7.1 Control Modes

The “best way” to optimize smart wells depends strongly on a company’s
philosophy of reservoir management. When controlling the choke size,
the oil industry refers to this as reactive and proactive operations (Jansen,
2001; Kharghoria et al., 2002). With increasing use of 4D seismic, passive
control is also another type of choke control. These three control modes
are summarized and distinguished below.
• Reactive control. If the GOR or water cut (wc%) exceeds its target max-
imum allowable production during a period of time, the ICVs are con-
trolled to reduce GOR or wc%, or at least to prevent further increase in
wc% until the target is reached. The philosophy is based purely on obser-
vation and reaction; if something happens, then the ICVs are changed. It
is the most frequently used control method. However, because of the
restriction, this control often results in poor oil-sweep efficiency, and
in certain regions of the reservoir, the oil could be bypassed and not dra-
ined well (Essen et al., 2010). In this control, the essential toolkits or soft-
ware may be well surveillance, production monitoring, and nodal
analysis.
• Proactive control. On the basis of the prediction of the GOR or wc% pro-
duction profile, the value of ICV settings are anticipated and set up
before the water or gas breakthrough occurs at the well. It is believed
that the gas or water flooding (either from injection or gas cap/aquifer)
is still away from the wellbore at some distance between the wellbore and
the reservoir. The philosophy is based on trusted reservoir data or a
physics-based reservoir model (i.e., 3D numerical simulator or 1D ana-
lytical application). If the reservoir is very well characterized in terms of
fluid-rock properties and the 3D numerical model can capture the main
heterogeneities, then proactive control can maximize the oil-sweep effi-
ciency. However, this control is sometimes found to be impractical com-
pared with reactive control, because of the time it takes to run the batch
process and integrating geological and reservoir data.
• Passive control. 4D time-lapsed seismic processes a seismic signal to inter-
pret the signal attributes and to capture water movement during water