Rock physics modelling for determination of effective elastic properties of the lower Paleozoic shale formation, North Poland

• Published in: Acta geophysica Vol. 67; no. 6; pp. 1967 - 1989
• Main Author: Wawrzyniak-Guz, Kamila
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.12.2019; Springer Nature B.V
• Subjects: Acoustic impedance; Anisotropy; Buy sell agreements; Carbonates; Cementation; Compaction; Data logging; Earth and Environmental Science; Earth Sciences; Effective medium theory; Elastic properties; Geophysics/Geodesy; Geotechnical Engineering & Applied Earth Sciences; Kerogen; Lithology; Mineral composition; Modelling; Ordovician; Organic matter; Paleozoic; Physics; Research Article - Special Issue; Rocks; Shales; Silurian; Structural Geology; Trends; Poland; Rock physics template; Baltic Basin; Elastic properties; Shale gas
• ISSN: 1895-6572; 1895-7455
• DOI: 10.1007/s11600-019-00355-6

This paper presents an application of rock physics templates constructed with the use of the granular effective medium theory and the shale model to estimate the elastic properties of the Silurian and Ordovician shale formations from the Baltic Basic, Poland. The author uses available logging data from three nearby wells and their petrophysical interpretation to distinguish various lithologies and to determine average matrix mineral composition of each lithology group, essential in further rock physics modelling. Anisotropy estimation and investigation of the relation between various petrophysical parameters precede the rock physics modelling. The logging data cross-plotted in Vp / Vs ratio–acoustic impedance domain reveals distinct compaction trend for shales, which is not followed by shales with increased organic matter and calcareous deposits. These two lithology groups present own trends, which are related to increasing kerogen and carbonate minerals contents, respectively. The trends are the subject of rock physics modelling. Granular effective medium rock physics templates are constructed for each lithology group. The rock physics analyses reveal that the elastic properties of strongly compacted shales, including shales with organic matter, might be successfully described by the lower modified Hashin–Shtrikman bound, which is useful in compaction trend modelling. Marly deposits can be modelled in a similar way to shales. The upper modified Hashin–Shtrikman bound provides a better template for carbonates as it models the cementation process. The shale model provides independent rock physics template for shales. Comparison of these two approaches shows that the granular effective medium method better describes the elastic properties of the analysed formations. The paper includes also the proposition of the final rock physics template constructed for the Silurian and the Ordovician formation from the Baltic Basin that can contribute to a better understanding of the elastic properties of the lower Paleozoic shale plays in Poland.