Poroelastic experiments on COx claystone: Insight from the Biot's coefficient measurement with water

• Published in: Engineering geology Vol. 300; p. 106580
• Main Authors: Wang, Chuanrui, Gay, Nicolas, Talandier, Jean, Skoczylas, Frédéric
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-04-2022; Elsevier
• Subjects: Biot's coefficient; COx claystone; Engineering Sciences; Mechanics; Poro-mechanical couplings; Terzaghi's material; Transverse isotropy; Transverse isotropy; Poro-mechanical couplings; COx claystone; Biot's coefficient; Terzaghi's material
• ISSN: 0013-7952; 1872-6917
• DOI: 10.1016/j.enggeo.2022.106580

This paper focuses on Biot's coefficient measurement of saturated COx claystone. The tests were systematically conducted to provide clarification on its value as the available literature indicates quite erratic results from 0.26 to 1. The difficulty of this work mainly lies in the time that is necessary to stabilize each loading step (confining pressure and/or pore pressure) and also in sample preparation. Two main results were obtained: 1) Whatever the initial conditions were (confining pressure Pc amplitude, hydric state, damaged or not…), all samples exhibited a significant anisotropic swelling during the first water injection; 2) even being a transversely isotropic rock, its Biot's tensor is (quasi) isotropic thus leading to a unique coefficient “b” which is very close to 1. Such results are consistent with what was observed with gas as being the fluid to control pore pressure in partially saturated samples.
•Poro-mechanical tests on COx claystone samples, focused on Biot's tensor component measurements, were performed with water.•Significant anisotropic swelling was observed on every sample after the first water injection.•The measured Biot's tensor with water is isotropic with a unique component ‘b’.•COx claystone still behaves as a Terzaghi's material (b≈1) at a saturated state.•Consistency of these results was observed with results obtained with gas being the pore fluid.