Modeling Thin Inclusions in Poroelastic Medium by Line Discontinuities

Germanovich, L. N.; Chanpura, Rajesh A.

doi:10.1007/978-94-017-0081-8_17

Cited by 6 publications

(10 citation statements)

References 17 publications

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“…This is a general type of spatiotemporal distribution due, for example, to the pore pressure diffusion from a point (line) source in the fault plane [e.g., Carslaw and Jaeger, 1959]. Such a situation can be envisioned if a borehole is drilled along the fault plane (orthogonal cross-section of which is shown in Figure 1a) and fluid is injected into the borehole to trigger an earthquake in more controllable conditions than it would happen otherwise [Garagash et al, 2009;Germanovich et al, 2010Germanovich et al, , 2011. Examples of the injection scenarios, for which the pressure along the fault is described by (7) include fluid injection into the fault zone characterized by negligible transverse permeability, under a constant overpressure Dp,…”

Section: Fault Slip Due To Pore Pressure Loadingmentioning

confidence: 99%

“…Other simplifying assumptions of this work include neglecting the effect of poroelastic changes of the background stress level [e.g., Segall , 1989; Rudnicki , 1999; Germanovich and Chanpura , 2002], as well as the effect of inelastic changes of gouge porosity and permeability with the slip [ Rice , 1992; Segall and Rice , 1995; Garagash and Rudnicki , 2003, and references therein].…”

Section: Introductionmentioning

confidence: 99%

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Nucleation and arrest of dynamic slip on a pressurized fault

2012

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[1] Elevated pore pressure can lead to reactivation of slip on pre-existing fractures and faults when the static Coulomb failure is reached locally. As the pressurized region spreads diffusively, slip can accumulate quasi-statically (paced by the pore fluid diffusion) or dynamically. In this work, we consider a prestressed fault with a locally peaked, diffusively spreading pore pressure field to study (1) conditions leading to the escalation of slip and nucleation of dynamic rupture and (2) rupture run-out distance before it is arrested. Nucleation appears in this model when the fault friction decreases from its peak value with slip, while arrest of dynamic propagation is imminent on aseismic faults (i.e., such that prestress t b is less than the residual fault strength t r at ambient conditions). When fluid overpressure is a small-to-moderate fraction of the ambient value of normal effective stress (and prestress is large enough for fault slip to be activated by overpressure), dynamic rupture always nucleates, and the nucleation length increases with decreasing prestress practically independently of the overpressure value. Transition from the ultimately unstable (t b > t r ) to the ultimately stable (t b < t r ) fault loading is marked by a strong increase of the nucleation length (∝1/(t b À t r ) 2 ) as t b approaches t r from above. For aseismic faults (t b < t r ), no dynamic rupture is nucleated at large fluid overpressures for all but the smallest values of prestress. The largest run-out distances of dynamic slip on aseismic faults correspond to overpressure/prestress just sufficient for slip activation. In such cases, the dynamically accumulated slip can lead to enhanced, dynamic fault weakening, resulting in a sustained dynamic rupture and generating a large earthquake. This is consistent with field observations when the largest injection-induced seismicity occurred after fluid injection ended.

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Section: Fault Slip Due To Pore Pressure Loadingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Nucleation and arrest of dynamic slip on a pressurized fault

2012

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“…Nonlinear expressions for displacement resulting from large changes in effective stress are available but equation will be adequate for the ranges of stress change caused by most pumping tests. Note that relation (7) represents a particular case of the Winkler condition [e.g., Klarbring , ; Movchan and Movchan , ], which is asymptotically accurate for a thin, soft poroelastic layer [ Germanovich and Chanpura , ].…”

Section: Conceptual Modelmentioning

confidence: 99%

Reverse water‐level change during interference slug tests in fractured rock

Slack

Murdoch

Germanovich

et al. 2013

Water Resources Research

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[1] Reverse water-level responses in monitoring wells are widely known during pumping tests, where they are recognized as the Noordbergum or Rhade effects, and a similar response was observed in many of the 100þ interference slug tests conducted at a well field near Clemson, South Carolina. The reverse water-level effect is characterized by a drop in pressure head by 1 cm to several centimeters and it occurs in the first 10-100 s of the test. The reverse response is followed by a rise and fall of pressure head that is typical of slug-in tests. The reverse water-level response is highly repeatable, and it increases when the pressure used to create the slug test is increased. A conceptual model recognizes that opening displacement of the fracture wall can cause a pressure drop, even when the pressure increases in the wellbore. The conceptual model is supported by a closed-form, analytical solution and a numerical model that couple fluid pressure and deformation in a fracture. Characteristics of the reverse water-level response are sensitive to properties of the fracture system and enveloping formation. Parameter estimation methods can be used to invert theoretical analyses and use the reverse response to improve the characterization of fractured rock aquifers.

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“…It is well known that manipulations of subsurface fluids during waste disposal or petroleum recovery can significantly change in situ stresses due to the poroelastic effect (e.g. Segall et al 1994;Germanovich & Chanpura 2001). This has caused problems, by reactivating faults and inducing seismicity (Healy et al 1968;Segall et al 1994;Germanovich & Chanpura 2006), yet the same principle could be beneficial to the SIRGE process.…”

Section: (B) Poroelastic Preconditioningmentioning

confidence: 99%

Injection of solids to lift coastal areas

Germanovich

Murdoch

2010

Proc. R. Soc. A.

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Catastrophic flooding in coastal areas is an ongoing problem that may be aggravated by projected sea-level rise. We present a method of flood protection called SIRGE (solid injection for raising ground elevation), where the ground surface is raised by injecting sediment-laden slurry into hydraulic fractures at shallow depths. The injection process is repeated at adjacent locations to create a network of sub-horizontal, overlapping injections of solid material (hydraulic fractures). We argue that injecting sediment over large lateral distances would cause a lasting surface uplift that scales with the thickness of injected sediment at depth. We support this concept by an analysis showing that, in contrast to hydraulic fractures in petroleum reservoirs, hydraulic fractures in soft, shallow formations would typically grow in the toughness-dominated regime. It appears that the SIRGE process could be implemented to lift ground elevations in places such as Venice or New Orleans. Experimental and geological examples indicate that hydraulic fractures of suitable orientation and size can be created in areas with appropriate in situ stresses.

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Modeling Thin Inclusions in Poroelastic Medium by Line Discontinuities

Cited by 6 publications

References 17 publications

Nucleation and arrest of dynamic slip on a pressurized fault

Nucleation and arrest of dynamic slip on a pressurized fault

Reverse water‐level change during interference slug tests in fractured rock

Injection of solids to lift coastal areas

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