The role of petrographic heterogeneity in controlling the geomechanical behaviour of the Rotliegend sandstone reservoirs | Sebastian Mulder

Field/Discipline

• Geology
• Geochemistry
• Geosciences/Multidisciplinary

Summary

Fluid extraction from geological formations for purposes of subsurface utilization (e.g. hydrocarbon production, hydrogen storage, geothermal energy production) leads to pore pressure drop in reservoirs. The weight of the rock layers above the reservoir is partially carried by both the reservoir pore pressure and by the reservoir rock itself. Therefore, if fluids are extracted from the subsurface, the reservoir will experience an increase in overburden load, which may lead to compression, hence compaction of the reservoir rock. One type of reservoir rock that are highly susceptible to diagenetic processes and compaction are porous sandstones. Compaction of sandstone reservoirs is directly related to the petrography of the rock, which also impacts the fluid flow within, and geochemical and geomechanical properties of the reservoir. To predict how a reservoir responds to fluid extraction, it is thus crucial to have a clear understanding of the reservoir petrography and the factors controlling its lateral variability.

The Groningen gas field, situated in the northeastern part of the Netherlands, is Europe’s largest gas field. Since its discovery in 1959, approximately 75% of its 2,800 billion cubic meters naturals gas has been produced from the Upper Permian sandstone reservoir. The ongoing gas depletion led to pressure loss within the sandstones, which resulted in reservoir compaction and associated surface subsidence and increasing seismicity. However, a detailed model for the reservoir petrography does not exist for the Groningen gas field and surrounding aquifers, where production-induced compaction is an issue of major socio-economic impact.

The main goal of the project is to provide a petrographic model of the Groningen gas field and surrounding aquifers in order to predict reservoir compaction and surface subsidence. The aim of the study is threefold, namely (1) to characterize spatial petrographic trends within the Rotliegend reservoir rock and the surrounding aquifers respective to detrital composition and diagenetic components that might have an impact on the geomechanical behaviour and reservoir compaction, (2) to provide a petrographic framework at microscale based on samples from well cores of the Groningen gas field that can be implemented as a standard dataset in future geomechanical studies and reservoir modelling and (3) to apply a Convolutional Neural Network (CNN) on thin section images to determine the importance of semi-automated identification of key petrographic parameters on large petrographic datasets. This project will contribute to our understanding of the reservoir heterogeneity of the Groningen gas field and surrounding aquifers, which can be implemented into a predictive petrographic model that improves our knowledge of subsurface response to subsurface utilisation

Supervision by

• Promotor: Prof .dr. H.A.J. (Harro) Meijer | Centre for Isotope Research (CIO), ESRIG, University of Groningen
• Co-promotor: Dr. J.M. (Johannes) Miocic | Geo Energy, ESRIG, University of Groningen.

More information and contact details can be found on the personal profile of Sebastian Mulder.