Fluvial Research Group

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The predominantly fluvial Sherwood Sandstone Group is exposed across much of Central and NWEngland and forms an important reservoir succession in the Southern North Sea and East Irish Seabasins. Representative fluvial facies vary from coarse-grained channelised conglomerates to fine-grained unconfined sheet-flood sandstones, with mud-prone facies present in places. Additionally,fluvial facies exhibit a variety of styles of interaction with aeolian, sabkha and lacustrine facies, all ofwhich has resulted in an overall succession with reservoir properties that are difficult to predict. Thisproject is developing models that characterise the various styles of stratigraphic and diageneticheterogeneity present within the Sherwood Sandstone Group in order to produce quantitative estimatesof sand-body geometry and degree of interconnectivity that can be used as input to reservoir models inan attempt to determine the reservoir behaviour of marginal 'tight gas' plays.

Analysis of basin-scale architecture has involved the recording of over 80 1D sedimentary logs fromwhich the internal stratigraphy of various formations in the Sherwood Sandstone has been established.Regional key-surface tracing has been employed to determination the nature of spatial changes inpreserved sedimentary style. The construction of 2D architectural panels has enabled the style of fluvialbehaviour to be determined such that the geometry of preserved architectural elements can be used toreconstruct the likely style of the fluvial system and the nature of the processes that acted therein. Aseries of dynamic facies models account for complex spatial and temporal complexity within the system.

Reservoir character of the Permo-Triassic Sherwood Sandstone Group, UK

Nigel Mountney

Stratigraphic architecture, Thurstaston, Wirral

No vertical exaggeration

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H e l s b y S a n d s t o n e (T h u r s t a s t o n H a r d B e d)

W I l m s l o w S a n d s t o n e F o r m a t i o n

H e l s b y S a n d s t o n e (T h u r s t a s t o n M e m b e r)

? Mid-Triassic Unconformity

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10>284

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14>28618>300

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16>32016>276

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16>340Ripple cresttrend >140

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Alton Cliff EastHolly WoodWaste Farm 2Waste Farm 1 Toothill Rock Lion Rock Little Stoney Dale Qy Main Stoney Dale Qy

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Palaeocurrent datadifficult to obtain

due to quarry marks

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Trough>000

Trough>308

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18>010

16>35514>004

14>344

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18>02416>060

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08>200

Recognition of fluvial cyclicity,Hawksmoor Formation, Needwood Basin