Page 425 - Hydrocarbon Exploration and Production Second Edition

412 Production De-Bottlenecking

Producer

Injector
mainly oil
gas
mainly
water and gas water
mixture
Injected volume gas gas

water

Time
Figure 17.7 Water alternating gas injection (WAG).

tendency for oil to be bypassed. As with conventional flooding, once oil has been
bypassed it is difficult to recover efficiently by further flooding.
One problem facing engineers in this situation, where the process is applied
from waterflood initiation, is how to quantify the incremental recovery resulting
from the polymer additive.

17.4. Production De-Bottlenecking

As introduced in Section 16.2, Chapter 16, bottlenecks in the process facilities
can occur at many stages in a producing field life cycle. A process facility bottleneck is
caused when any piece of equipment becomes overloaded and restricts throughput.
In the early years of a development, production will often be restricted by the capacity
of the processing facility to treat hydrocarbons. If the reservoir is performing better
than expected it may pay to increase plant capacity. If, however, it is just a temporary
production peak such a modification may not be worthwhile (Figure 17.8).
As a field matures, bottlenecks may appear in other areas, such as water treatment
or gas compression processes, and become factors limiting oil or gas production.
These issues can often be addressed both by surface and subsurface options, though
the underlying justification remains the same – the NPV of a de-bottlenecking
exercise (net cost of action vs. the increase in net revenue) must be positive.
This seems obvious, but it is not always easy to predict how a change in one part
of a processing chain will affect the process as a whole (there will always be a
bottleneck somewhere in the system). In addition, it may be difficult to estimate the
cost in terms of extra manpower and maintenance overheads, where an increase in
capacity demands additional equipment. To be able to make a decision, it is