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Title: The sedimentology and reservoir characteristics of selected Upper Carboniferous sandbodies.
Author: Tester, Gillian Nicola.
ISNI:       0000 0001 3516 381X
Awarding Body: University of Keele
Current Institution: Keele University
Date of Award: 1991
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Outcrop data are increasingly used in reservoir simulation models for extrapolating well-data into interwell volumes and predicting subsurface porosity and permeability heterogeneity. This thesis has developed a method of core and outcrop description that provides quantifiable geological information for input into such models. Four Upper Carboniferous fluvio-deltaic sandbodies (two at outcrop in northern England and two in southern North Sea core) have been described using eight type lithofacies, "L1 to L8": Intraclast conglomerate; Pebbly sandstone; Large scale cross-bedded sandstone; Small scale crossbedded sandstone; Ripple cross-laminated sandstone; Heterolithic; Sandy mudstone and Yärbonaceous mudstone). These have been mapped onto photomontages of outcrops and used for core logging. Each sandbody has been subdivided into lithofacies associations, characterisable by their internal lithofacies geometries and vertical relationships. Outcrop studies have shown that sheet-like lithofacies geometries predominate in distributary channels. Previously described as a distributary channel, the Table Rocks Sandstone contains lenticular geometries and has been reinterpreted as a proximal distributary mouth bar Sandbody. Wells 44/28-2 and X represent comparatively varied alluvial/fluvial to fluvio-deltaic sequences, with sporadic primary reddening. Lengths of lithofacies units generally vary with grain size and overall depositional energy, Most mouth bar shales represent bedfarm drapes ("topset shales"), which are short (up to 4m) and relatively abundant. Fewer, longer "toeset shales", formed by amalgamation of fines at bedfarm bases, are typical in channel sandbodies. Core-plug measurements and petrographic estimates of poroperm characteristics of L1 to L8 have shown that grain size is a main control of permeability, Gridding of lithofacies maps has enabled the modelling of depositional permeability anisotropy, Each grid-square (lm by 0,5m) has been assigned a permeability "indicator" (relative value), based on its main lithofacies. L2 has been given the maximum permeability indicator, followed by L3, L4, L1 and L5. Semivariogram analysis of lateral (depositional) permeability anisotropy of a distributary channel Sandbody has shown that extrapolation of core or wireline log poroperm data would not be reliable for more than 25-30m around the borehole,
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Geology