Relationships Between Seismic Signals and Reservoir Properties of Tight Gas Reservoirs in Northwest Germany (Permian Rotliegend Sandstones)
Tight Gas Reservoirs in Northwest-Germany consist of aeolian and lacustrine sandstones in 3,5-5 km depth with moderate porosities but strongly varying permeabilities. Samples of comparable lithology with 10% porosity provide permeabilities in the range of 0,05-100 mD due to different mechanical compaction, mineral authigenesis and cement dissolution. These processes resulted in good and poor reservoir qualities in proximate areas. Therefore deep gas exploration is highly dependent on reservoir property information from 3D-seismic signals. In this study geophysical, petrophysical and petrological data are gained and evaluated to investigate the potential calibration of 3D-seismic signals with core and log data.
The relations between seismic and lithological properties have been investigated by triaxial measurements of travel times, image analysis of thin sections, NMR-measurements, Scanning Acoustic Microscopy and mercury-injection to derive pore parameters (e.g. aspect-ratio), compiling sedimentological features (e.g. sand-shale-interbeddings) and evaluating the influence of different water saturations on seismic signals. Until now the non linear behaviour of porosity and permeability, the clear relation between permeability and impedance and the correlation between impedance and cement types suggest a dependence of seismic signals and reservoir properties based on pore- and matrix geometries. These preliminary results correspond to pore parameters derived from image analysis of thins sections and to pore radii distributions from capillary pressure curves and NMR-measurements. We intend to visualize impedance contrasts by means of synthetic seismograms representing the extreme cases of different permeabilities.
Student Presentations
2005 AAPG International Conference and Exhibition (September 11-14, 2005) Technical Program