期刊
ROCK MECHANICS AND ROCK ENGINEERING
卷 55, 期 8, 页码 4697-4715出版社
SPRINGER WIEN
DOI: 10.1007/s00603-022-02842-7
关键词
Gas reservoir compaction; Triaxial testing; Digital volume correlation; X-ray computed tomography; Strain localization; Slochteren sandstone; Groningen field
资金
- Nederlandse Aardolie Maatschappij (NAM)
- Norwegian Research Council [267775]
- [12ZV820N]
High-resolution time-lapse X-ray micro-tomography imaging allows visualization of grain-scale deformation mechanisms during triaxial deformation of reservoir rock, providing important input for developing microphysical models describing compaction of gas reservoirs.
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 mu CT) 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 degrees C, 10 MPa pore pressure, 40 MPa effective confining pressure). A total of 50 three-dimensional mu CT scans were obtained during deformation, at a spatial resolution of 6.5 mu m. 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 (< 1%), and in the approach to brittle failure at 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.
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