Publication Date:
2005-12-01
Description:
Numerous major hydrocarbon accumulations are related to burial diagenesis in carbonate reservoirs; however, three-dimensional (3-D) modeling of such reservoirs is a major challenge. The geometries of diagenetic fronts are poorly understood, and few quantitative data on field and outcrop examples for these diagenetic zones exist. The Early Cretaceous Cogollo carbonates (Urdaneta West field, northwest Venezuela) are an example of deeply buried (〉5000 m; 〉1600 ft), diagenetically altered limestones producing from a few high-porosity streaks and fracture corridors. Reservoir “sweet spots” formed because of the interplay of structural evolution and diagenesis. Structural deformation not only generated a fracture network but also influenced primary facies distribution, circulation of diagenetic fluids, and distribution of early charged paleohighs in the reservoir. The prediction of reservoir sweet spots is of key importance for economic success in the Cogollo carbonates but constitutes a major challenge. This article outlines the genetic relationships between structural evolution and sweet-spot distribution, as well as the workflow developed to transfer these concepts into 3-D geocellular models. These 3-D models include a novel approach to fracture permeability prediction based on a geomechanical approach. The reservoir model predicts sweet spots along leached faults, which are best preserved in early charged paleohighs. The Cogollo and other reservoirs suggest that favorable structural development can generate and retain significant matrix porosity even at great depth. The workflow established and applied might help to maximize field potential in similar settings. Michael Pöppelreiter studied at the Mining University of Freiberg, Germany, the Postgraduate Research Institute of Sedimentology, United Kingdom, and the University of Tübingen, Germany, where he earned a Ph.D. in 1998. Since then, Michael has worked as a sedimentologist with Shell in Holland and is currently posted at Shell's Bellaire Technology Center in Houston to work as a reservoir geologist and three-dimensional (3-D) modeler of carbonate reservoirs. His research interests include structural control on reservoir facies distribution and integrated 3-D reservoir prediction in carbonate reservoirs.Maria Balzarini is a senior staff petrophysicist at Shell International Exploration and Production. She has held various assignments as a geologist and petrophysicist in Shell since 1981. Her experience includes exploration, production, operations, and technology support. Carbonate petrophysics and field studies are her primary areas of interest. Maria holds a B.Sc. degree in geology from the University of Massachusetts, Amherst, and an M.S. degree in geology from the University of Washington. Paulino graduated from the Universidad de Oriente in Venezuela in 1995 with a degree in geology. He joined Shell Venezuela in June 1996, where he is working as a production geologist. Paulino is posted to Shell Sakhalin, where he works as a 3-D modeler. Stephan Engel holds a Ph.D. in geology from Technische Hochschule Darmstadt, Germany. He joined Shell in 1985 and has since been working in multiple Shell-operated ventures across Europe, the Middle East, and the Americas. At present, he is leading the geoscience group of Shell Venezuela. Miguel received a B.Sc. degree from Universidad Simon Bolivar (1989) and an M.Sc. degree from the Colorado School of Mines (1999). He worked as a structural geophysicist and petrophysicist with Petroleo de Venezuela Sociedad Autonoma (PDVSA) and currently as a seismic interpreter with Shell Venezuela. Miguel's interests include structural interpretation, petrophysics, reservoir characterization, and geomechanics. Birger Hansen earned an M.Sc. degree in geology, at Århus, Denmark, and a Ph.D. in metamorphic petrology in Århus. He worked as a reservoir geologist with Statoil 1981–1985. Birger was the founder and managing director of Z&S Geology in Stavanger, Norway, and became business development manager with Baker Atlas. Since 2001, he has been working as an independent consultant, chairman of Eriksfjord, and a specialist in 3-D remodeling, borehole image log analysis and geomechanics, and wellbore stability. Xiomara holds a Ph.D. in carbonate diagenesis from McGill University in Canada and worked as a carbonate sedimentologist for PDVSA for more than 20 years. She joined Shell Venezuela in 2003 and has since been working as a senior sedimentologist for both clastics and carbonates. Jose Morell is a staff reservoir engineer at Shell International Exploration and Production. His expertise is in the modeling and simulation of integrated reservoir models and optimum field development. Jose holds a B.Sc. degree from the University of Puerto Rico and a Ph.D. from the University of Houston, both in chemical engineering. Ron Nelson has worked professionally within the oil and gas industry for 25 years, first with Amoco and later with BP Amoco. He provides technology support and applications in structural geology and fracture reservoir evaluation as an independent consultant. Ron worked as a specialist and manager in all major technical organizations of Amoco. He holds a B.S. degree in geology from Northern Illinois University and an M.Sc. degree and a Ph.D. also in geology from Texas A&M University. He has been an AAPG Distinguished Lecturer twice, a Society of Petroleum Engineers Distinguished Author, and is the author of the textbook, Geological Analysis of Naturally Fractured Reservoirs . Francisco joined Shell Venezuela S.A. in 1996 after obtaining a degree in petroleum engineering from the Colorado School of Mines. Francisco has worked in operations, contracting, and since 2000, as a reservoir engineer for the Cogollo carbonate reservoir in Lake Maracaibo and participated in multidisciplinary subsurface studies for Shell Venezuela S.A. in Rijswijk and Houston from 2002 to 2004.
Print ISSN:
0149-1423
Electronic ISSN:
1943-2674
Topics:
Geosciences
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