Potential Size of
Accumulation
Houton Head Hydrocarbon Reservoir System
The Reservoir quality aeolian dune sands of the Lower Eday Sandstone at Houton Head Orphir are full of bitumen indicative of being previously full of CRUDE OIL which has rapidly lost its volatiles on exposure. This area had the potential for more than 1.5 billion barrels of oil in place (in an excellent reservoir sand).
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The mature organic rich lacustrine Laminites of the Orcadian Basin
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Aeolian and fluvial sands of the lower Eday Sandstones. Thickness is at least 80m on location and upwards of 200m on the south side of the North Scapa Fault. Porosity 14% to 25% and permeability 3mD to 2,000mD - this quality of reservoir could give high recovery factors.
Seal:
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The lateral seal is muds and flagstones of the Stromness and Rousay flagstone Formations. The top seal (cap rock) is not observed in the area. As the Eday flagstones (possible seal) outcrop to the SE and E of Houton the facies affinities are more likely to be with the north Hoy group. In Hoy there is a local unconformity on top of the lower Eday Sandstone and this is overlain by relatively impermeable cemented volcanic Ash and lava flows.
Trap:
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The Trap at Houton (Combination Trap, Fault and Anticline) is formed by the reservoir sands dipping south away from the faults and bottom sealed by the Rousay Flags.
Potential Size of Accumulation:
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With spill point adjacent to the N Scapa Fault the accumulation would cover a minimum 640acres and contain 150 MMBOIP (35 MMBO - million barrels recoverable). If the sand is 200m and there is no spill point The accumulation could be in excess of 400MMBOIP and 100 MMBO recoverable.
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The other two potential reservoirs - the northern Anticline Trap and Anticline adjacent to the N Scapa Fault could each speculatively hold in excess of 500MMBOIP.
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The potential for more than 1.5 billion barrels of oil in place (in an excellent reservoir sand) within an area of 80 sq km could make this an attractive target if located at depth offshore.