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License P. 1292, Block 15/11a
Relinquishment Report
January 2009
_____________________________________________________________________________________________
1. General
Licence:
Round:
License Type:
Blocks:
Equity:
P.1292
23rd (2005)
Traditional
15/11a
Talisman (operator)
Work Programme:
Pre-stack depth migration; 25km2 output area from 120km2
input area. There are no outstanding work commitments for
this Block.
100%
2. Licence History
0o 12’W
0o 00’E
0o 12’E
Key
Field
58o 40’N
14/14b 14/15b
15/11b
Discovery
Prospect
0
2
4 km
14/15a
15/13b
14/14a
P. 1292
15/12b
CLAYMORE
15/13a
58o 30’N
15/16b 15/17
PIPER
15/18b
Lowlander
SCAPA
SALTIRE
HIGHLANDER
TARTAN
Iona
CHANTER
DUART
58o 20’N
15/18a
14/19s 14/20b
PETRONELLA
Figure 1: Location Map of Licence P. 1292, Block 15/11a.
Block 15/11 was first awarded in 1972 to an Occidental-led group as part of the 4th
Round multi-Block licence P.220; it was first drilled later that year when 15/11-1
targeted a large four-way dip closure but was abandoned dry. Well 15/11-2, drilled in
1973, was also abandoned as a dry hole. In 1974, the third well on the block, 15/113, was abandoned dry but encountered good oil shows in the primary Piper target.
This well also found heavy (10o API) oil in shallow Tertiary sands (2200-2800ft
TVDss). Following the discovery of the Piper and Claymore Fields, the Block was
transferred initially to Segregation Licence P.247 in 1974 and then into Segregation
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License P. 1292, Block 15/11a
Relinquishment Report
January 2009
_____________________________________________________________________________________________
Licence P.248 and finally P.250, both in 1976. The Block was partially relinquished at
the end of the initial term in 1978. Elf-Enterprise-Caledonia (EEC), which had
replaced Occidental as the operator in the UKCS following the Piper Alpha disaster in
1988, drilled well 15/11a-4 in 1990. The well encountered hydrocarbon shows. The
relinquished part of the block, 15/11b, was awarded in the 16th Round in 1995 to an
Enterprise-led group; in 1996 they drilled 15/11b-5 which was again abandoned with
oil shows. Block 15/11b was relinquished in 2001 and Block 15/11a in 2004. Block
15/11 was contested in the 23rd Round in 2005 with Block 15/11a being awarded to
Talisman 100% as a Traditional Licence, and Block 15/11b as a Promote Licence to
Iceni (100%). In 2007, Iceni was acquired by Bridge who went on to drill the 15/11b-6
well in 2008; this well failed to encounter hydrocarbons and was abandoned dry.
During 2007-8, Talisman attempted to farm-down their interest in Block 15/11a in
order to get a full or partial carry on a well to test the Deep Colonsay prospect.
Having failed to secure a partner, and unwilling to drill the prospect at 100% equity,
Block 15/11b was surrendered on November 3, 2008.
3. Exploration Activities
No new wells were drilled within Block 15/11a during the licence period. The wells
already drilled within the surrounding area are:






15/11-1
15/11-2
15/11-3
15/11a-4
15/11b-5
15/11b-6
Occidental
Occidental
Occidental
EEC
Enterprise
Bridge
1972
1973
1974
1990
1996
2008
P&A Dry
P&A Dry
P&A Oil Shows
P&A Oil Shows
P&A Oil Shows
P&A Dry
In 2001, Talisman acquired a proprietary 3D seismic survey over all of their acreage
in the Flotta Catchment Area (FCA) which included Block 15/11a. This was
processed at the time using a full Kirchoff pre-stack time migration. In 2006, Talisman
initiated a pre-stack depth migration of the full 3D dataset; numerous delays meant
that the output data were not delivered to Talisman until March 2008.
4. Prospectivity Analysis
4.1 Upper Jurassic Piper Fm
The only prospectivity recognised by Talisman at the time of application for Block
15/11a was a four-way dip closure reservoired in Upper Jurassic Piper sandstones,
informally known as Deep Colonsay (Figure 2). Seismic mapping on the latest
PreSDM dataset shows a structural closure down to at least 6400ft; well 15/11-3,
drilled within this four-way dip closure and penetrating top reservoir at 6110ft, exhibits
evidence of both live oil and tarry globular oil from sidewall core analysis with
residual saturations up to 30%. Talisman interpret these data as evidence of a former
hydrocarbon column which has subsequently been breached, at least partially. The
presence of the Deep Colonsay prospect relies on this breaching occurring discretely
along the fault which separates 15/11-3 from the crest of the mapped structure at c.
5700ft. This would give a potential unbreached residual column of 300ft to the east
of the fault.
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License P. 1292, Block 15/11a
Relinquishment Report
January 2009
_____________________________________________________________________________________________
0o 00’E
0o 02’E
0o 04’E
0o 06’E
o
58 32’N
2
0o 08’E
Zechstein faults projected up
onto BCU surface
Complete erosion of Piper
reservoir at BCU surface
58o 31’N
Piper
Sa
o
58 30’N
nd
sto
ne
er
0
ed
1 km
Se
is
m
ic
Li
ne
od
Figure 2: Top Piper Sandstone Reservoir Depth Structure
The shallow marine Piper-Sgiath sandstones are proven to be of excellent quality in
all three of the surrounding wells. In wells 15/11-1 and 15/11-3, the reservoir section
is thinned due to erosion by the Base Cretaceous unconformity (BCU). Over the crest
of the Deep Colonsay prospect, the seismic reservoir package is interpreted to
thicken to more than 400ft (Figure 3). The reservoir properties are expected to be
similar to the adjacent wells with high net to gross and porosities in excess of 20% for
the upper sand section.
15/11-2
SW
Deep Colonsay
NE
5000 ft
Top Chalk
BCU / Top Piper
7500 ft
MCU / Base Piper
Zechstein
Figure 3: Top Deep Colonsay Seismic Illustration
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License P. 1292, Block 15/11a
Relinquishment Report
January 2009
_____________________________________________________________________________________________
The Kimmeridge Clay Formation, which provides the topseal to most of the Upper
Jurassic Fields and discoveries in the Witch Ground Graben, is absent over the crest
of the Deep Colonsay prospect, as evidenced by wells 15/11-1 and 15/11-3. Instead,
the top seal relies on Upper Cretaceous chalks and marls. The viability of this top
seal has been proven over the crest of the nearby Piper Field and in the Hood
discovery in Block 15/13a.
4.2 Tertiary
Columns of viscous, heavy oil (10o API, 4089 cP) have been encountered in Eocene
sands in 15/11-3 and a number of wells adjacent to Block 15/11a at depths of around
2000-3000 ft TVDss; well 14/15-2 drillstem-tested one of these intervals and
managed to recover 3 bbl of oil to surface at an estimated rate of 10 stb/d. Despite
oil-in-place estimates of 500-1000 mmstb, these are not considered by Talisman to
be commercially viable at present due to the adverse nature of the fluids.
5. Reserves Summary
Mean
P90
P50
P10
STOIIP (mmbbls)
37
5
22
90
Reserves (mmbbls)
20
3
12
49
Talisman’s internal Peer Review process assigned a 25% geological chance of
success to the Deep Colonsay prospect. Whilst this is not an unreasonable level of
risk per se, it is almost entirely due to one factor, preservation of the hydrocarbon
trap, and is therefore considered to be unacceptable.
6. Clearance
Talisman Energy (UK) Limited, as the former operator of Block 15/11a, confirms that
the seismic data contained within this report and the interpretation thereof are
proprietary to Talisman and give permission to publish the report.
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