A determination of the geometry and connectivity of reservoir units within the Statfjord Formation, United Kingdom/Norway Statfjord oil field

Hoddinott, Paul M. (2006) A determination of the geometry and connectivity of reservoir units within the Statfjord Formation, United Kingdom/Norway Statfjord oil field. (MSc(R) thesis), Kingston University, .

Abstract

Determining the distribution of ancient fluvial sediments provides many challenging questions to geologists and reservoir engineers who need to understand the hydrocarbon-bearing reservoirs these sediments fonn. The fluvial reservoirs of the late Triassic to early Jurassic Statfjord Fonnation within the giant Statfjord oil field provide a classic example of the complexities of mapping fluvial channel sandstones. The geometry and connectivity of these reservoir sandstones are difficult to determine using traditional mapping techniques and stochastic techniques may produce a broad range of outcomes that do not always relate to the original data that have been collected over the field. Conventional mapping techniques make use of traditional stratigraphic correlation methods based on users' interpretations of wireline data that may be subjective and based on the individual geologist's ideas and experience. This study provides a critique of the effectiveness of such geological correlations and compares and contrasts these methods with an objective computer-program based technique known as 'Slotting'. A diverse series of relatively simple and effective techniques including mapping of net sandstone to gross succession thickness, lithology transition analysis, dipmeter study of sandstone foreset directions, and interpretation of acoustic impedance seismic have been followed. These methods are directly applicable to the geological data available and closely integrate the original wellbore and seismic data. Finally a predictive statistical modelling procedure relating wireline data with lithology type has been conducted to determine sandstone distribution in uncored wells. The statistical model has proved to be helpful in providing statistics on sandstone bodies over the field area and this has assisted in a better understanding of the fluvial depositional environment. These results have been used to establish how the interacting allogenic factors of base level, eustatic and climate change have contributed in influencing fluvial sedimentary architecture.

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