Fault Reactivation by Fluid Injection: Controls From Stress State and Injection Rate

Passelègue, François; Brantut, Nicolas; Mitchell, Thomas M.

doi:10.1029/2018gl080470

Cited by 96 publications

(94 citation statements)

References 53 publications

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“…We conclude that simple effective stress laws that consider a uniform pore pressure distribution in a fault of simple geometry is often not adequate for the prediction of fault reactivation in shale formations. This finding is consistent with Passelègue et al (2018) who showed at laboratory scale that a nonlocal rupture initiation criterion should be considered to describe fault reactivation because of the fluid pressure heterogeneity within the fault.…”

Section: Discussionsupporting

confidence: 92%

“…Previously, during laboratory tests on fractures without filling, Barton et al (1985) and Olsson and Barton (2001) demonstrated that the coupling between fracture shear displacement or normal closure and fracture hydraulic conductivity variations depended both on the stress conditions and on fracture surface characteristics such as the roughness. Recent laboratory results highlight that the variation in effective normal stress related to local fluid injection in a fault plane does not imply complete separation of the two sides of a fault because complex channeling effects may favor heterogeneous pore pressure variations within the fault plane controlling leakage and nonlocal rupture initiation before the Coulomb rupture criterion is exceeded (Passelègue et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Discussionsupporting

confidence: 92%

Section: Introductionmentioning

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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“…Moreover, fluid injection into a saw-cut granite sample in stress relaxation test shows that the onset of fault activation may not be predicted by equation 1 at high injection rates. This is presumably caused by a significantly heterogeneous distribution of fluid pressure on the fault plane (Noël et al, 2019;Passelègue et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Laboratory Study on Fluid‐Induced Fault Slip Behavior: The Role of Fluid Pressurization Rate

Wang

Kwiatek

Rybacki

et al. 2020

Geophysical Research Letters

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Understanding the physical mechanisms governing fluid‐induced fault slip is important for improved mitigation of seismic risks associated with large‐scale fluid injection. We conducted fluid‐induced fault slip experiments in the laboratory on critically stressed saw‐cut sandstone samples with high permeability using different fluid pressurization rates. Our experimental results demonstrate that fault slip behavior is governed by fluid pressurization rate rather than injection pressure. Slow stick‐slip episodes (peak slip velocity < 4 μm/s) are induced by fast fluid injection rate, whereas fault creep with slip velocity < 0.4 μm/s mainly occurs in response to slow fluid injection rate. Fluid‐induced fault slip may remain mechanically stable for loading stiffness larger than fault stiffness. Independent of fault slip mode, we observed dynamic frictional weakening of the artificial fault at elevated pore pressure. Our observations highlight that varying fluid injection rates may assist in reducing potential seismic hazards of field‐scale fluid injection projects.

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“…As a result, stress drop occurs due to the compression acted on the sample by actuator piston drops in response to fracture slip, and the fracture slips slows down and finally ends at a lower stress level. Later, Passelègue et al () also used a similar constant piston‐displacement control to study the distribution of pressure and effective stress in a fracture.…”

Section: Experimental Methodsmentioning

confidence: 99%

Injection‐Induced Propagation and Coalescence of Preexisting Fractures in Granite Under Triaxial Stress

Yan

Ghassemi

2019

JGR Solid Earth

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The dilatant shear slip of preexisting fractures/faults by injection at pressures below the minimum in situ stress has been recognized as an important permeability creation mechanism during reservoir stimulation. However, interconnected fracture network generation through the propagation and coalescence of preexisting fractures during shear stimulation has been rarely studied through laboratory experiments. To examine permeability enhancement through the propagation and coalescence of preexisting fractures, we conducted novel triaxial‐injection experiments under representative crustal stress conditions on cylindrical granite samples containing single or double preexisting fracture(s)/flaw(s). In the sample with a single fracture, SW‐1, new cracks propagated from the preexisting fracture due to injection. In the sample with two fractures, SW‐2, a highly conductive fracture network was created by the coalescence of newly formed cracks with preexisting fractures. As a result, the equivalent permeability of the sample was enhanced by 17 to 35 times. Both tensile wing cracks and shear and/or mixed‐mode secondary cracks were detected from the scanning electron microscope images of the tested samples. Our results suggest that in addition to dilatant shear slip, propagation and coalescence of preexisting fractures significantly contribute to reservoir permeability creation during low injection pressure stimulation in fractured rocks. Although the experiments focused on reservoir stimulation, the results have relevance to crustal permeability evolution and induced seismicity.

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Fault Reactivation by Fluid Injection: Controls From Stress State and Injection Rate

Cited by 96 publications

References 53 publications

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

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

Laboratory Study on Fluid‐Induced Fault Slip Behavior: The Role of Fluid Pressurization Rate

Injection‐Induced Propagation and Coalescence of Preexisting Fractures in Granite Under Triaxial Stress

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