--> ABSTRACT: Outcrop Studies of the Lower Cretaceous Woburn Sands (UK) for Heterolithic Tidal-Estuarine Reservoir Characterization, by Shuji Yoshida, Matthew D. Jackson, Howard D. Johnson, Ann H. Muggeridge, Richard J. Dixon, and Liz J. Jolley; #90906(2001)

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Shuji Yoshida1, Matthew D. Jackson2, Howard D. Johnson3, Ann H. Muggeridge3, Richard J. Dixon4, Liz J. Jolley5

(1) Royal Holloway, University of London, Egham, Surrey, England
(2) Imperial College, London, United Kingdom
(3) Imperial College, London, England
(4) BP, Sunbury-on-Thames, United Kingdom
(5) BP Exploration, Sunbury-on-Thames, Middlesex, England

ABSTRACT: Outcrop Studies of the Lower Cretaceous Woburn Sands (UK) for Heterolithic Tidal-Estuarine Reservoir Characterization

Tidal sandstone reservoirs host major hydrocarbon accumulations in the northern North Sea, Venezuela and elsewhere. However, their characterization and modelling are difficult. This is because they contain a complex array of sedimentary heterogeneities at various lengthscales, and predicting their production behaviour has been hampered by a lack of quantitative data on the dimensions and geometries of these heterogeneities.

We have used the well-exposed outcrops of the Lower Cretaceous Woburn Sands (UK) to characterize the small- to intermediate- (millimetre- to metre-) scale heterogeneities of tidal deposits, utilizing architectural element and sedimentary facies analyses within a sequence stratigraphic framework. The unit contains a wide range of tidal sedimentary structures, and is interpreted as macro-tidal estuary deposits. Mud drapes occur along the set boundaries and foresets of cross-stratification and burrows in various sizes. This unit also contains distinct, thin sub-horizontal, wavy, mud laminae (c. 1 - 2 mm thick or less) within the ripple cross-laminated part. Most mud drape types have log-normal length distributions within the outcrop, with periodic clustering in the vertical direction.

The Beryl Formation (Bruce field, northern North Sea) is interpreted to have been formed under the regional tectonic and depositional setting comparable to the Woburn Sands. The Beryl Formation contains abundant thin wavy mud drapes analogous to those found within the Woburn Sands. A range of quantitative outcrop data, suitable for validating and/or populating objects for the stochastic modelling of tidal reservoirs, is presented for the various facies and sand body types, including shale layer and heterolithic facies dimensions.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado