4D Synchrotron X-ray Imaging of Grain Scale Deformation Mechanisms in a Seismogenic Gas Reservoir Sandstone During Axial Compaction

J.F. Van Stappen*, J. A. McBeck, B. Cordonnier, R. P. J. Pijnenburg, François Renard, C. J. Spiers, S. J. T. Hangx

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Understanding the grain-scale processes leading to reservoir compaction during hydrocarbons production is crucial for enabling physics-based predictions of induced surface subsidence and seismicity hazards. However, typical laboratory experiments only allow for pre- and post-experimental microstructural investigation of deformation mechanisms. Using high-resolution time-lapse X-ray micro-tomography imaging (4D µCT) during triaxial deformation, the controlling grain-scale processes can be visualized through time and space at realistic subsurface conditions. We deformed a sample of Slochteren sandstone, the reservoir rock from the seismogenic Groningen gas field in the Netherlands. The sample was deformed beyond its yield point (axial strain > 15%) in triaxial compression at reservoir P–T-stress conditions (100 °C, 10 MPa pore pressure, 40 MPa effective confining pressure). A total of 50 three-dimensional µCT scans were obtained during deformation, at a spatial resolution of 6.5 µm. Time lapse imaging plus digital volume correlation (DVC) enabled identification of the grain-scale deformation mechanisms operating throughout the experiment, for the first time, both at small, reservoir-relevant strains ( 10%. During small-strain deformation, the sample showed compaction through grain rearrangement accommodated by inter-granular slip and normal displacements across grain boundaries, in particular, by closure of open grain boundaries or compaction of inter-granular clay films. At intermediate and large strains (> 4%), grain fracturing and pore collapse were observed, leading to sample-scale brittle failure. These observations provide key input for developing microphysical models describing compaction of the Groningen and other producing (gas) reservoirs.
Original languageEnglish
Pages (from-to)4697-4715
Number of pages19
JournalRock Mechanics and Rock Engineering
Volume55
Issue number8
DOIs
Publication statusPublished - Aug 2022

Keywords

  • Digital volume correlation
  • Gas reservoir compaction
  • Groningen field
  • Slochteren sandstone
  • Strain localization
  • Triaxial testing
  • X-ray computed tomography

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