Analysis of acoustic emissions recorded during a mine-by experiment in an underground research laboratory in clay shales

Amann, Florian; Gonidec, Yves Le; Senis, Montse; Gschwind, Sophie; Wassermann, J.; Nussbaum, Christophe; Sarout, Joël

doi:10.1016/j.ijrmms.2018.04.021

Cited by 15 publications

(9 citation statements)

References 22 publications

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“…At the location of our test which is roughly in the middle of the Opalinus Clay layer, the greatest uncertainty is the magnitude of σ 3 which appears low compared to the pore pressure of about 2 MPa measured away from the galleries excavation damage zone. For these reasons, other authors recently re-estimated σ 3 to higher values of 2.5-to-2.9 MPa (Amann et al 2018). In addition, the hydraulic tests allowed for a good estimate of the stress magnitude normal to the bedding, estimated to be 4.2 MPa.…”

Section: Comparison With Other Stress Tensor Estimations At Mont Terrimentioning

confidence: 99%

“…This fracture pressure value is significantly larger than the fault opening pressure of 5.43 MPa. Another reason for the lack of a vertical fracture intersecting the bedding planes and or the faultparallel-to-bedding is that several authors (Amann et al ;Thoeny 2014) showed that tensile and cohesive strengths of such structures are dramatically low, respectively ∼0.5 and 0.6 MPa, which make these planes much weaker than the intact rock.…”

Section: Effect Of Heterogeneity On Hydraulic Based Stress Measuremenmentioning

confidence: 99%

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Estimating perturbed stress from 3-D borehole displacements induced by fluid injection in fractured or faulted shales

Guglielmi

Nussbaum²,

Rutqvist

et al. 2020

Geophysical Journal International

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S U M M A R YHydrofracturing stress measurements in fractured and anisotropic shales are notoriously difficult, because opening of existing geological features tends to prevent the creation of a pure hydraulic fracture perpendicular to the least compressive principal stress. Here we show how adding 3-D borehole-displacement measurements while conducting the hydraulic injection test helps to better constrain the principal stress orientations and magnitudes. We developed a 3-D fully coupled hydromechanical numerical model to analyse the displacement, fluid pressure and injection flow-rate data measured during an injection pressure-step-rate test conducted to activate a faulted borehole interval in the Mont Terri Opalinus Clay (Switzerland). We find that injected fluids can only penetrate the fault when it is at or above the Coulomb failure pressure. Borehole displacement orientations are sensitive to a ∼15 • variation in the stress-tensor orientation and a 1 MPa stress magnitude variation. Although some dispersion occurs while rupture is propagating along the fault plane ∼4 m away from the borehole, the maximum density of displacement orientations consistently informs about the stress orientation. Thus, an extended injection step-rate approach coupled with an accurate in situ measurement of the borehole wall displacements can be used to better constrain the local stress field perturbations in fractured shales and in heterogeneous rock in general.

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Section: Comparison With Other Stress Tensor Estimations At Mont Terrimentioning

confidence: 99%

Section: Effect Of Heterogeneity On Hydraulic Based Stress Measuremenmentioning

confidence: 99%

Estimating perturbed stress from 3-D borehole displacements induced by fluid injection in fractured or faulted shales

Guglielmi

Nussbaum²,

Rutqvist

et al. 2020

Geophysical Journal International

Self Cite

View full text Add to dashboard Cite

show abstract

“…2. Comparing to the measured stress data from the site [24,25], the orientation of the stress used in the model is slightly rotated by 5 degrees for the two horizontal components (see Fig. 13a).…”

Section: Step1 -Fm1 Resultsmentioning

confidence: 99%

“…Table 2. Fault orientation and stress tensor of Mont Terri data [24,25], data used in a recent study [26] and data estimated in this study. Further development is needed to improve the model behavior.…”

Section: Step1 -Fm1 Resultsmentioning

confidence: 99%

Modelling the water injection induced fault slip and its application to in-situ stress estimation

Shiu¹,

Guglielmi

Graupner

et al. 2021

International Journal of Rock Mechanics and Mining Sciences

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“…The greatest uncertainty is the magnitude of σ 3 , which appears low compared to the pore pressure of about 2 MPa measured away from the excavation damage zone of the galleries. For these reasons, other authors recently reestimated σ 3 and reported higher values of 2.5-to-2.9 MPa (Amann et al, 2018). In addition, the hydraulic tests allowed for a good estimate of the stress magnitude normal to the bedding planes, estimated to be 4.2 MPa.…”

Section: Tectonic Setting: Geological Structures Stress Conditions mentioning

confidence: 99%

Complexity of Fault Rupture and Fluid Leakage in Shale: Insights From a Controlled Fault Activation Experiment

Guglielmi

Nussbaum²,

Jeanne

et al. 2020

JGR Solid Earth

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We observed rupture growth caused by controlled fluid injections at 340‐m depth within a fault zone in the low‐permeability Opalinus Clay in the Mont Terri Underground Research Laboratory (Switzerland). The rupture mechanisms were evaluated using measurements of the three‐component borehole wall displacements and fluid pressure in two sections of the fault zone and located horizontally 3 m apart from each other. One section was set across a secondary segment of the fault and used for stepwise fluid injection intended to trigger rupture growth. The other section was set across the principal shear zone of the fault for monitoring. After stepwise pressure increase up to 5.95 MPa at injection, rupture initiated as slip activation, followed by an overall opening of the fault planes connected to the injection. After 19 s of continued injection, displacements arrived at the monitoring point on the principal shear zone. These displacements are about 2.4 times larger than in the secondary fault segment. Overall, the displacements corresponded to a normal fault activation. About 9 s after the displacement front arrived, a strong pressure increase of 4.17 MPa was measured at the monitoring point, indicating a hydraulic connection had formed along the initially very low permeability fault planes between the injection and the monitoring points. Our analyses highlight that the fault activation is consistent with the state of stress but that injection pressure must be close to the normal stress acting on the fault for permeability to be generated and for fluid leakage to occur.

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Analysis of acoustic emissions recorded during a mine-by experiment in an underground research laboratory in clay shales

Cited by 15 publications

References 22 publications

Estimating perturbed stress from 3-D borehole displacements induced by fluid injection in fractured or faulted shales

Estimating perturbed stress from 3-D borehole displacements induced by fluid injection in fractured or faulted shales

Modelling the water injection induced fault slip and its application to in-situ stress estimation

Complexity of Fault Rupture and Fluid Leakage in Shale: Insights From a Controlled Fault Activation Experiment

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