Sensitivity of the impact of geological uncertainty on production from faulted and unfaulted shallow marine oil reservoirs - objectives and methods.

Manzocchi T.¹, Carter J. N.², Skorstad A.³, Fjellvoll B.³, Stephen K. D.⁴, Howell J.⁵, Matthews J. D.², Walsh J. J.¹, Nepveu M.⁶, Bos C.⁶, Cole J.⁷, Egberts P.⁶, Flint S.⁸, Hern C.⁹, Holden L.², Hovland H.¹⁰, Jackson H.⁷, Kolbjørnsen O.³, MacDonald A.¹⁰, Nell P.A.R.¹¹, Onyeagoro K.⁹, Strand J.¹, Syversveen A. R.³, Tchistiakov A.⁶, Yang C.⁴, Yielding G.¹¹ & Zimmerman R.²

1 - Fault Analysis Group, School of Geological Sciences, University College Dublin, Belfield, Dublin.
2 - Department of Earth Science and Engineering, Imperial College, London SW7 2BP, UK.
3 - Norwegian Computing Centre, PO Box 114 Blindern, N-0314 Oslo, Norway.
4 - Institute of Petroleum Engineering, Heriot-Watt University, Edinburgh EH9 9NX, UK.
5 - Department of Earth Sciences / Centre for Integrated Petroleum Research, University of Bergen, Allegt. N-5007 Bergen, Norway.
6 - The Netherlands Institute of Applied Geoscience –TNO, P.O. Box 80015, 3508 TA, Utrecht, Netherlands.
7 - BG International, Thames Valley Park, Reading, Berkshire RG6 1PT, UK.
8 - Sequence Stratigraphy Group, Department of Earth and Ocean Sciences, University of Liverpool , Liverpool L69 3GP, UK.
9 - Shell International Exploration and Production, Volmerlaan 8, Postbus 60, 2280 AB, Rijswijk, The Netherlands.
10 - Roxar Software Solutions, 165 Skoyen, Karenslyst Alle 11, 0212 Oslo, Norway.
11 - Badley Geoscience, North Beck House, North Beck Lane, Hundleby, Spilsby, Lincolnshire, PE23 5NB, UK.

Abstract - Estimates of recovery from oil fields are often found to be significantly in error, and the multidisciplinary SAIGUP modelling project has focused on the problem by assessing the influence of geological factors on production in a large suite of synthetic shallow-marine reservoir models. Over 400 progradational shallow-marine reservoirs, ranging from comparatively simple, parallel, wavedominated shorelines through to laterally heterogeneous, lobate, river-dominated systems with abundant low-angle clinoforms, were generated as a function of sedimentological input conditioned to natural data. These sedimentological models were combined with structural models sharing a common overall form but consisting of three different fault systems with variable fault density and fault permeability characteristics and a common unfaulted end-member. Different sets of relative permeability functions applied on a facies-by-facies basis were calculated as a function of different lamina-scale properties and upscaling algorithms to establish the uncertainty in production introduced through the upscaling process. Different fault-related upscaling assumptions were also included in some models. A waterflood production mechanism was simulated using up to five different sets of well locations, resulting in simulated production behaviour for over 35000 full-field reservoir models. The model reservoirs are typical of many North Sea examples, with total production ranging from c. 15*10⁶ m³ to 35*10⁶ m³, and recovery factors of between 30% and 55%. A variety of analytical methods were applied. Formal statistical methods quantified the relative influences of individual input parameters and parameter combinations on production measures. Various measures of reservoir heterogeneity were tested for their ability to discriminate reservoir performance. This paper gives a summary of the modelling and analyses described in more detail in the remainder of this thematic set of papers.

Petroleum Geoscience, 14, 3-15.

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