RE: Re iow12 Oct 2018 20:31
In the event of a Portland discovery at Arreton North, that demonstrates similar reservoir parameters to the
HH-1 oil discovery, a water re-injection scheme could be implemented to provide pressure support and
improve sweep-efficiency in the field’s early productive life. It is reasonable to expect a material increment in
overall oil recovery. Based on work carried out for HH-1, the successful implementation of such a scheme
could lead to the recovery of an additional 8-12% of STOIIP, which based on current estimates of STOIIP, as
shown in Table 7.8, could be equivalent to a further 0.3 – 7.2 MMbbl of gross recoverable oil.
As the Arreton North Portland Limestone reservoir is separated from the Arreton Main reservoir by a fault,
the recoverable volumes are classified as Prospective Resources. A geological chance of success (COS)
was determined, using a Rose-style risking and taking into account that the play has been completely derisked
via the discovery made by the Arreton-2 well. Xodus considered that minor risks remain for the
undrilled prospects, specifically:
> Source: particularly maturation and volumes generated are not deemed to be a risk, given the highquality
source rock in the area and the proven charge from Arreton-2.
> Timing/Migration: while highly likely, we cannot categorical regard the presence of an effective
migration pathway into each prospect.
> Reservoir: while presence is highly likely, we cannot conclude that either it’s presence or quality is
absolute prior to drilling.
> Closure: a small risk has been placed on the reliability of the mapping, and in particular the depth
conversion.
> Containment: risked according to the presence of faults. As the prospects are undrilled, certainty
around the effectiveness of lateral seal against the faults and as such preservation from spill cannot
be guaranteed.
Based upon these criteria, risks are determined to be small and accordingly a high chance of success for
each element has been chosen. Combined, this calculates an overall COS for the Arreton North prospect of
69%