Analogues, especially outcrop analogues, have played a central role in improving understanding of subsurface reservoir architectures. Analogues provide important information on geobody size, geometry and potential connectivity. The historical application of outcrop analogues for understanding geobody distributions in reservoirs is reviewed, from the pioneering work of the 1960s to the high-tech virtual outcrop methodologies of today. Four key types of analogue data are identified: hard data, which describe the dimensions and geometry of the geobody; soft data, which describe the conceptual relationships between different geobody types; training images, which record the dimensions, proportions and spatial relationship; and analogue production data, which are taken from direct subsurface production analogues. The use of these different data types at different stages of the geomodelling workflow is discussed and the potential sources of error considered. Finally, a review of geobody and analogue studies in different clastic environments is discussed with reference to selected previous work and the range of papers in the current volume.Over the last 30 years, computer-based, geocellular models have become a routinely used tool for understanding subsurface reservoirs (Budding & Inglin 1981; review in Keogh et al. 2007). Such models are typically built to aid field development and reservoir management business decisions, but also serve the purpose of integrating disparate scales and types of subsurface data, and visualizing complex three-dimensional (3D) distributions of rocks and fluids. Since the application of early modelling tools, to the present day, it has been common practice to supplement sparse subsurface datasets (e.g. wells and seismic) with data and concepts derived from reservoir analogues. The intention of this process is to generate more accurate representations of the subsurface than would otherwise be possible. Considerable effort has been expended in recent years by industry and academia on the description of reservoir analogues for this purpose. This paper examines the challenges inherent in selection and application of appropriate analogue data, particularly quantitative datasets, during construction of geological models.The most commonly used type of analogue is the outcrop, where information on geometric data that are limited in the subsurface is more readily available in cliff sections. Analogues may also include subsurface data but this is less common. This aspect is considered briefly in this review. The perspective on the application of analogues as discussed here is with regard to sedimentology and stratigraphy applied to hydrocarbon reservoir analysis, and the insights that 3D facies models bring to the distribution of petrophysical properties that control hydrocarbon flow. The discussion is based on clastic systems, but many of the aspects described are equally as applicable to carbonates, although they are not discussed explicitly here. Other branches of subsurface modelling, no...

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A thin sequence of in situ fossiliferous gravels and silts overlain by a glacigenic bed is described from a temporary exposure in a working silica sand quarry. The sequence directly overlies unweathered Mercia Mudstone. Locally the bedrock surface forms a shallow palaeovalley some 15 m deep and almost 1 km wide. The sequence in question lies close to the valley axis. The silts, pollen, plant macrofossils, Mollusca. Coleoptera. and Ostracoda assemblages each suggest a similar environment of sedimentation: a shallow pool within a treeless open landscape. Much of the bedrock within the working quarry appears to be draped by the Oakwood till and this unit is co-extensive with the glacigenic sediments over' the silts and gravels. In parts at least. the till has been subject to redeposition and its upper surface has scattered ventifacts. Above this wind-deflation horizon lies the Chelford Sands Formation, in the middle of which is the Chelford Interstadial stratotype. the Farm Wood member. The biota preserved in the gravels and silts suggest a stadia1 prior to the Early Devensian Chelford Interstadial. This is the first unambiguous stratigraphic evidence from Cheshire of a glacial event antedating the Chelford Interstadial.KEY WORDS Cheshire Plain Early Devensian Oakwood till Stadia1 biota Pre-Chelford interstadial

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SPE Members Abstract Detailed reservoir characterisation and modelling has been an active area of petroleum technology development for several years now, but incorporating and scaling up these geologic models into fluid flow and production simulations is a major challenge. The objective of this study is to properly incorporate all relevant levels geological heterogeneity identified in a detailed outcrop reservoir description into a flow simulation of an hypothetical reservoir. We apply the "geopseudo" upscaling methodology to the geological description of a shallow marine sequence exposed in the Book Cliffs. The study identifies which features are important for field-scale fluid flow and recovery for a waterflood. A cross section waterflood flow simulation, using the geopseudo upscaling technique, was carried out on an interpreted cross-sectional panel through a portion of the Book Cliffs outcrop in Utah. The section consists of the following lithofacies: Undifferentiated Upper Shoreface deposits, Hummocky Cross Stratified sands, the Swaley Cross Stratified sands, Fluvio-Tidal Channel Sandstones and two units of Heterolithics. A grid block size of 10 metres by 1 metre was used, with two stages of upscaling to account for the effects of small-scale heterogeneities. The thin beds of shales were accounted for using vertical and horizontal transmissibility multipliers between grid blocks. Sensitivity runs were carried out to assess the relative contribution of different geological parameters to the waterflood performance. Introduction The geopseudo method is an approach to multiphase fluid flow upscaling which attempts to incorporate successive scales of geological heterogeneity into effective flow functions, The scales used in this upscaling methods are based on the inherent geological hierarchy in sedimentary and sequence stratigraphic systems (lamina, laminaset, bed, bedset, parasequence, etc.). Pseudofunctions are generated at each scale (e.g. laminaset pseudos) and are then incorporated into models at the next scale (e.g. bedform pseudos), and so on, until the full-field model is reached. In this manner, the effects of small scale sedimentary structure may be systematically incorporated into the "pseudo" flow functions (the geopseudos) for the grid blocks in the full-field model. The effects of numerical dispersion and grid block size are also taken into account and corrected for in this method. The lack of petrophysical and geological data for assigning to 3D oil field models is a familiar problem, so that geological inference and geostatistical approaches are required to fill the model volume. Understanding which features and parameters have the greatest influence on, say. a waterflood of an oilfield is critical to this process, and is a vital stage for correctly modelling and predicting reservoir performance. We show here just how a detailed reservoir outcrop analogue can be used to assess the influence of geological heterogeneities on a field-scale waterflood model, using this geopseudo method. The objective of the study is to identify which features in the rock section affect waterflood performance for a typical waterflood, taking proper account of capillary, gravity and viscous forces. We have modelled a 45 metre thick and 1370 metre long cross-section (comprising two parasequences and one incised valley fill unit), and have, as yet, ignored possible effects of the third dimension. Geological Background Geological and petrophysical data were collected from the Cretaceous Blackhawk Formation, where it forms part of the extensive outcrop of the Book Cliffs of eastern Utah (Figure 1). This wave dominated succession forms a potential analogue for many Western Interior Basin and North Sea Brent Province reservoirs. The Blackhawk Formation developed during the eastward progradation of a broad alluvial plain into the Western Interior Basin during the Late Cretaceous. P. 845