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Abstract

AAPG Bulletin, V. 88, No. 10 (October 2004), P. 1369-1390.

Copyright copy2004. The American Association of Petroleum Geologists. All rights reserved.

Integration of subsurface applications to develop a dynamic stochastic modeling workflow

T. Svanes,1 A. W. Martinius,2 J. Hegre,3 J.ndashP. Maret,4 R. Mjoslashs,5 J. C. U. Molina6

1Sincor, Avenida Francisco Solano, Centro Empresarial Sabana Grande PH, Sabana Grande, Caracas 1050, Venezuela; present address: Statoil, Forushagen, N-4035 Stavanger, Norway
2Sincor, Avenida Francisco Solano, Centro Empresarial Sabana Grande PH, Sabana Grande, Caracas 1050, Venezuela; present address: Statoil RampD, Arkitekt Ebbellsvei 10, N-7005 Trondheim, Norway; [email protected]
3Sincor, Avenida Francisco Solano, Centro Empresarial Sabana Grande PH, Sabana Grande, Caracas 1050, Venezuela; present address: Total Exploration UK PLC, 33 Cavendish Square, W1G OPW London, United Kingdom
4Sincor, Avenida Francisco Solano, Centro Empresarial Sabana Grande PH, Sabana Grande, Caracas 1050, Venezuela; present address: Total, 2 place de la Coupole, La Deacutefense 6, 92400, Courbevoie, France
5Sincor, Avenida Francisco Solano, Centro Empresarial Sabana Grande PH, Sabana Grande, Caracas 1050, Venezuela; present address: Statoil, Forus Vest, N-4035 Stavanger, Norway
6Sincor, Avenida Francisco Solano, Centro Empresarial Sabana Grande PH, Sabana Grande, Caracas 1050, Venezuela

AUTHORS

Tarald Svanes is discipline leader in subsurface uncertainty treatment at Statoil. Since 1990, he has worked with integrated, three-dimensional reservoir modeling and flow simulation, applying advanced geostatistical techniques. Currently, one of his main focuses is to reduce uncertainty in field prognoses by integrating production data into the reservoir characterization process. Svanes holds an M.S. degree in physics from the Norwegian Technical Institute in Trondheim. At Statoil, he has worked with various aspects of reservoir technology, ranging from research to operational field management, both in the North Sea and internationally.

Allard W. Martinius has an M.Sc. degree from the University of Utrecht and a Ph.D. from Delft University. He joined Statoil in 1996 and spent his first three years at the research center in Trondheim, working on reservoir characterization and modeling of heterolithic tidal res ervoirs. He subsequently joined Sincor in Venezuela as a field development geologist. He returned to Statoil's research center in 2002 to lead a reservoir and uncertainty modeling research group. His main interests are in siliciclastic sedimentology, stratigraphy, reservoir characterization, and geomodeling.

JoAnn Hegre received an M.Sc. degree from Tulane University (U.S.A.). She is currently head of geological research at Total's Geoscience Research Center in London. She has specialized in the field of geomodeling and reservoir characterization for the past seven years. Before taking up this position, she spent three years at Sincor, where she was in charge of geomodeling and volume calculations.

Jean-Pierre Maret joined Total in 1982 and worked as field geologist and team leader at the head office in Paris until 1993. During that period, he spent two years in Abu Dhabi and four years in Buenos Aires. Subsequently, he became exploration manager for Total Myanmar in Yangon, where he spent four years; after which, he was in charge of field evaluation studies and exploration coordinator for southeast Asia. Recently, he worked for two years in Venezuela on the Sincor field, where he was responsible for the geology and geophysics studies and operations. Maret is currently the coordinator for the Americas for Total.

Rune Mjoslashs is lead geologist for the Snorre field, northern North Sea, which he joined in 2002. Prior to that, he was seconded to the Sincor field in Venezuela as senior sedimentologist in the full-field evaluation team. He has been with Statoil since 1991 and has worked as exploration and production geologist on various technical evaluation projects. His main interest is in sedimentology and genetic stratigraphy. From 1997 to 1999, he was Statoil's advisor in sedimentology. Rune has a Cand. Scient. degree from the University of Bergen. After obtaining his degree, he worked for two years as exploration geologist for Norsk Hydro and subsequently, four years as scientist at Rogaland Research Institute. He has published articles on sedimentology, diagenesis, and sequence stratigraphy both for petroleum exploration and production purposes.

Juan Carlos Ustaacuteriz Molina, a petroleum engineer from the Universidad Central de Venezuela, obtained his degree in 1994. Since then, he has worked for Mares de Venezuela (MARAVEN) and Petroacuteleos de Venezuela S. A. (PDVSA) in operations and reservoir simulation. In 1998, he started to work for Pennzoil in western Venezuela as a geomodeler and joined Sincrudos de Oriente (SINCOR) as geomodeler in 2000.

ACKNOWLEDGMENTS

The authors acknowledge Sincor and the shareholders of Sincor (Total, PDVSA, and Statoil) for permission to publish this paper. We thank our colleagues J. Casas, G. Cha, L. de Pazzis, M. Exposito, M. Grausem, R. Krigsvoll, M. Levret, A. Linjordet, X. Mathieu, J. Peralta, and D. Soubeyrand for their enthusiastic support, discussions, and data analysis. Palynoflora analysis was carried out by E. Gonzalez-Guzman. A. Fajardo, J. L. Rubiano (Instituto Colombiano del Petroacuteleo) and T. Cross (Strategic Stratigraphy Inc.) carried out the Salt Wash outcrop analog study. Discussions with O. Lia (Statoil RampD) on the application of seismic data to condition stochastic models are gratefully acknowledged. The manuscript benefited from critical reviews by A. C. MacDonald (Roxar) and P. S. Ringrose (Statoil) and two anonymous AAPG Bulletin reviewers. AAPG Bulletin editors J. Lorenz and R. Erickson are thanked for their careful and constructive editing.

ABSTRACT

Building stochastic models in a preproduction phase of field development is crucial for accurate horizontal well positioning in the Sincor field (Orinoco heavy-oil belt, Venezuela), formed by highly permeable unconsolidated fluvial and deltaic sands of the Oficina Formation and containing low-gravity oil (average 8.3deg API). A multidisciplinary approach to drill the initial approximately 250 horizontal production wells has proven useful to field management. Geomodeling is used to evaluate well pattern development plans; calculate full-field production percentile profiles; and evaluate uncertainties in water production, well production potential, and cluster performance. Data from vertical observation wells (full well-logging suite) and deviated wells (to investigate the stratigraphy away from the vertical well) are used to characterize reservoir architecture. Three-dimensional seismic data, including seismic data inverted into acoustic impedance, are used to construct structure maps and shale probability maps. The integrated and interpreted information is used to position horizontal wells deterministically in a cluster-type (group of wells radiating out from a central point in a 3.2 times 1.6-km [2 times 1-mi] production area) development pattern and serves as input to stochastic reservoir models that are conditioned to vertical well observations and the shale probability maps. Ten realizations are used to estimate the uncertainty range of net-to-gross in the proposed horizontal well trajectories. To ensure a stable model, the average of these 10 realizations is used as a trend to generate one stochastic petrophysical model that is subsequently used for flow simulation. Based on the results, and in combination with the confidence in the interpreted geological data (for example, distribution of areas with a net sand thickness above a minimum), proposed horizontal wells are accepted or rejected.

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