Geofizyczna analiza własności zbiornikowych osadów kredy w niecce mogileńskiej

Abstract

GEOPHYSICAL ANALYSIS OF RESERVOIR PROPERTIES OF CRETACEOUS DEPOSITS IN THE MOGILNO THROUGH AREA

Summary

Within reservoir rocks of the Late Mesozoic deposits in the Mogilno through, considerable perspectives as concerns oil and gas content are related to the Lower Cretaceous sandstones. Geophysical examinations made in bore holes within the Lower Cretaceous deposits of the area considered have been a basis for the determination of this formation. On the results of laboratory examinations of drill cores and of depositional waters empirical method of interpretation of borehole geophysics data have been worked out by regression analysis. This method allowed the author to determine for the Lower Cretaceous deposits, pierced by bore holes made within the Mogilno trough, the following properties:

- clay content Ci based on gamma logging;

- porosity Φ_N based on neutron-gamma logging (with regard to the influence of clay content);

- porosity Φ_R based on resistivity logging (with regard to the influence of clay content);

- saturation of porous space with bitumens Srg;

- saturation of rock with bitumens ΦSrg.

Taking into account these date one can calculate, with the aid of double Fourier series, the approximation of trends of changes in reservoir parameters from the regional point of view. For calculations and construction of maps of these trends digital computers have been used. The above examinations demonstrate that the Lower Cretaceous sandstones are, as far as their oil and gas content is concerned, very promising. Moreover, they also show trends in the perspectives of these rocks.