AAPG Bulletin; January 2006; v. 90; no. 1;
p. 61-89; DOI: 10.1306/03080504124
© 2006 American Association of Petroleum Geologists (AAPG)
An unusual, muddy, epeiric carbonate reservoir: The Lower Muschelkalk (Middle Triassic) of the Netherlands
Ravi Borkhataria1,
Thomas Aigner2 and
Koos J. C. P. Pipping3
1 University of Tübingen, Institute for Geosciences, Sedimentary Geology, Germany; present address: Shell Exploration and Production International, P.O. Box 60, NL-2280 AB Rijswijk, Netherlands;
ravi.borkhataria{at}shell.com
2 University of Tübingen, Institute for Geosciences, Sedimentary Geology, Sigwartstrasse 10, D-72076, Tübingen, Germany;
thomas.aigner{at}uni-tuebingen.de
3 Shell Exploration and Production Europe (Nederlandse Aardolie Maatschappij B.V.), P.O. Box 28000, NL-9400 HH Assen, Netherlands;
koos.pipping{at}shell.com
Ravi Borkhataria studied geology at the University of Darmstadt, Germany, and received his Ph.D. from the University of Tübingen, Germany, in 2004, carrying out a multiyear, discipline-bridging reservoir-characterization project for Nederlandse Aardolie Maatschappij B.V. (NAM)/Shell. He is currently working as a geologist in the Shell Carbonate Team in Rijswijk, Netherlands. His research interests include evolution of carbonate-evaporite basins and stratigraphic reservoir prediction in carbonate systems.Thomas Aigner studied geology at the universities of Stuttgart, Tübingen, Reading, and Miami and received his Ph.D. in 1985. He then worked for 6 years as an exploration geologist with Shell Research. Since 1991, he has been a professor of sedimentary geology at the University of Tübingen. He heads a research group of applied sedimentary geology, focusing on carbonate reservoir characterization and outcrop analog studies. He was an AAPG European Distinguished Lecturer in 1996.
Koos Pipping is currently the senior geologist of the Schoonebeek oil-field redevelopment team with NAM. He graduated with an M.Sc. degree in geology from Leiden University, Netherlands, and joined Shell in 1980. He worked as a geologist and petrophysicist in multidisciplinary production and exploration teams in the Netherlands and Malaysia. Until recently, he was responsible for the geological aspects of onshore gas fields (including the Groningen field) producing from Carboniferous and Permian–Triassic carbonate and siliciclastic reservoirs.
The mud-dominated Lower Muschelkalk carbonates (Middle Triassic) are a unique reservoir currently producing gas in the Dutch De Wijk field. Numerous gas shows scattered over the Netherlands onshore and offshore suggest further, currently unrecognized potential. This study complements an extensive subsurface data set with selected outcrop information to localize missed opportunities and evaluates the factors controlling the development of this unusual reservoir type. The muddy carbonates are deposits of a storm-dominated, epeiric carbonate ramp with negligible depositional gradient. Different marlstone, dolomudstone, and lime mudstone facies types reflect the low-energy coastal-plain to inner ramp and higher energy midramp to proximal outer ramp depositional environments. The best reservoir facies is recognized in distal inner ramp algal dolomudstones (porosity up to 24% and permeability up to 32 md). Because of the variable intensity of early, facies-related diagenesis, the reservoir quality of dolomudstones decreases markedly in landward and seaward direction from the distal inner ramp. The stacking of decimeter- to meter-thick reservoirs is reflected by a fourfold hierarchy of depositional cycles that can largely be recognized with conventional wire-line logs. High-resolution outcrop and subsurface correlations reveal that stacks of thin-bedded reservoir units most probably pinch out within a few kilometers, and that their lateral continuity should not be overestimated despite the epeiric layer-cake setting. Local reservoir occurrences are commonly situated above paleohighs of tectonic or halokinetic origin. Not only the reduced thickness of the Lower Muschelkalk above these paleohighs, but also the presence and lateral extent of local reservoirs, might be detected with seismic data. The general facies and reservoir patterns exemplified by the Lower Muschelkalk may also be of use for reservoir prediction in similar epeiric settings elsewhere, for instance, in the Middle East.
Copyright © 2009 by American Association of Petroleum Geologists (AAPG)
