KRAFT, THOMAS, and MARTIN HOCK, BEB Erdgas und Erdol GmbH, Hannover, Germany

ABSTRACT: Reservoir Quality Units in Rotliegende Sandstones of North Germany

The major producing gas fields in the Permian Rotliegende are situated in an approximately 50 km wide, northwest-southeast-striking belt from Groningen to north Hannover. The main Rotliegende reservoirs are shoreline and dune sediments in the Wustrow, Dethlingen, and Schneverdingen sandstones and are situated at depths between 3500 and 5000 m. Porosities range from 8-18%, with permeabilities of 0.001-800 md, depicting a strong degree of reservoir heterogeneity even at field scale.

Sedimentary facies and diagenesis are recognized as the main reservoir controlling factors. Log-derived mineralogy and diagenesis can be calibrated to the cores and then extrapolated to the uncored intervals. The method is based on cluster and principal component analysis and combines the whole suite of petrographical, geochemical, and petrophysical laboratory measurements with the log data. Thereby, the diagenetic features of reservoir sandstones can be evaluated throughout the uncored intervals, and lithological variations in nonreservoir sections, fanglomerates, volcanites, and mudstones can be detected. The sedimentary environment is interpreted mainly from dipmeter. Eventually, the method also should reduce coring expenses.

From crossplots of log-derived diagenesis and facies parameters vs. permeability, porosity, or saturation, reservoir quality units can be identified and tied to seismic attributes. Mapping these units allows one to better distinguish pay areas and explain failures.

AAPG Search and Discovery Article #90990©1993 AAPG International Conference and Exhibition, The Hague, Netherlands, October 17-20, 1993.