21CXRM Phase 2 East Shetland Platform Data Package

<p>Integrated petroleum systems (PeST) studies and seep
evaluations of the East Shetland Platform and SW Approaches area of the
UKCS.  The studies were carried out as an industry collaboration as part
of the 21CXRM initiative.  The studies were completed in Q3 2018 and
remained confidential to the participant group until the 31st
Licence Round offers of award were made.  APT led the technical evaluation
team under contract to the  NSTA on behalf of the participant group.</p><p>

</p><p>The SW Approaches and East Shetland Platform are two areas
of the UKCS perceived within the industry as being relatively under
explored.  The reasons for this are many and complex but, as part of the
21CXRM initiative that seeks to support the industry in exploring
under-explored areas, this work addresses questions around the existence and
effectiveness of petroleum systems within the areas.  The evaluation
builds on earlier work providing a fully integrated, very high-quality
geochemistry and thermo-chronology dataset and basin modelling studies of the
two basins of interest. Additionally, appropriate biomarker studies allow
age-diagnostic assessment of any oils sampled allowing oil-source correlations
to be attempted.</p><p>

</p><p>East Shetland Platform:</p><p>

</p><ul>
 <li><span style=''>Analysis of Devonian
     source rocks suggests that oil-prone Middle and potentially Lower Devonian
     source rocks, albeit with relatively modest TOC, exist across the study
     area.</span></li>
 <li><span style=''>Geochemically at least
     two Palaeozoic oil families have been identified, both of which can
     seemingly be differentiated from Kimmeridge Clay Formation sourced oils.</span></li>
 <li><span style=''>The highest risk
     associated with play models in this area which utilise an intra-platform
     Devonian source rock is related to its maturity timing, with the most
     pessimistic scenarios being of pre-Jurassic hydrocarbon expulsion.</span></li>
 <li><span style=''>The eastern portion of
     the Crawford-Skipper Basin is prospective, if material source rocks exist
     in the Devonian sequence.</span></li>
 <li><span style=''>The geochemistry of the
     oil stains characterised in this study in Quad 9 are suggestive of the
     presence of oils not related to the KCF system and lends credence to the
     potential for Palaeozoic source plays in this area.</span></li></ul><div>

<p>SW Approaches:</p>

<ul>
 <li><span style=''>Material source rocks in
     the Early Jurassic are proven to exist; the oil shows reported have
     largely been proven    and typed to Early Jurassic source
     rocks.</span></li>
 <li><span style=''>Some of these shows
     occur in Triassic stratigraphy, suggesting some complex migration paths
     are operating, at least locally.</span></li>
 <li><span style=''>Basin modelling suggests
     the principal sensitivity to the volumes generated is the location of the
     source rock with the Lower Jurassic stratigraphy (reflecting its
     thickness); with an order of magnitude difference in volumes for modelling
     at the uppermost versus lowermost Lower Jurassic.</span></li>
 <li><span style=''>Many of the wells
     drilled in the vicinity of the kitchens mapped in this study were either
     targeted at base Cretaceous closures (e.g. 73/12-1) or apparently failed
     to target any genuine trapping feature (e.g. most wells in the South
     Celtic Sea) potentially reflecting the vintage of these wells, which were
     drilled on 2D data. There seem to be few valid tests of the potential
     petroleum system(s).</span></li>
 <li><span style=''>Basins in the area are
     likely be challenged by an absence of reservoir. Where penetrated the
     Triassic is comprised of thick intervals of mudstone, non-reservoir
     limestones and claystones (e.g. 93/2-2). No locations have been mapped
     that would set up a geometry comparable to that at Wytch Farm, where the
     Purbeck monocline places Triassic reservoir sands above mature Liassic
     source rocks.</span></li>
 <li><span style=''>The Paleozoic potential
     to the North of the Cornubia Massive is very poorly constrained and
     warrants further analysis.</span></li></ul></div>

Tags: Exploration, NSTA, Operators, Petroleum Systems
Organization: North Sea Transition Authority