Abstract: Prediction of Porosity in Permian (Zechstein 2) Carbonate Rocks of Eastern Netherlands from Seismic Data
G. T. Maureau, D. H. Van Wijhe
The geologic depositional model of the Zechstein 2 carbonate development is so complex that prediction of high-porosity zones solely on geologic grounds is impossible. We describe a two-phase study of determination and prediction of these high-porosity areas from combined seismic and well data.
Phase 1, the basic feasibility study, consisted of 2 parts, a model study followed by a well log study. In both parts, acoustic impedance logs were filtered to test the feasibility of resolving porosity changes within the frequency range associated with seismic data. Based on our comprehensive model of the environment of deposition of the Zechstein evaporites, acoustic impedance logs were constructed, each log representative of a particular environment. These logs then were filtered with a suite of band-pass filters. The gross changes in porosity were easily recognized. The model study was followed by a study of acoustic impedance logs from actual downhole measurements taken from similar environments of deposition as represented in the model study. Regardless of geologic variations, t e changes in porosity were clear.
Phase 2 involved prediction and verification. An exploration well, planned to penetrate the Zechstein 2 carbonate zone, was connected to a previously drilled carbonate test by a good-quality seismic line. In the previous well, about 60 m of good porous limestone was penetrated. From the combined well and seismic data, we predicted that a very similar development could be expected in the new location. Subsequent drilling proved the presence of about 50 m of good porous carbonate rock developed in an environment of deposition similar to that in the other well. We feel that this technique has allowed us to predict reservoir porosity and will be useful in developing new structural or stratigraphic plays.
AAPG Search and Discovery Article #90961©1978 AAPG Annual Convention and Exhibition, Oklahoma City, Oklahoma