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

Slack, Trever Z.; Murdoch, Lawrence C.; Germanovich, L. N.; Hisz, D.

doi:10.1002/wrcr.20095

Cited by 22 publications

(18 citation statements)

References 30 publications

(42 reference statements)

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“…Among important processes taking place in fractured reservoirs, the hydromechanical (HM) coupling between pressure‐driven flow and fracture deformation has received considerable attention for at least three reasons. First, it integrates the physical behavior of the fluid and the host rock as a whole, with complex fluid‐to‐solid and solid‐to‐fluid interactions [e.g., Rice and Cleary , ; Rutqvist and Stephansson , ; Segall , ; Slack et al , ; Tsang and Witherspoon , ; Wang , ]. As an example, a rise in fluid pressure inside a fracture causes reversible deformation when the rock medium can be considered as elastic.…”

Section: Introductionmentioning

confidence: 99%

“…Hydraulic properties of fracture networks depend primarily on their structure and connectivity, which control how easily a fluid particle may find its way through a fractured rock unit [Berkowitz, 10.1002/2017JB014045 reasons. First, it integrates the physical behavior of the fluid and the host rock as a whole, with complex fluid-to-solid and solid-to-fluid interactions [e.g., Rice and Cleary, 1976;Rutqvist and Stephansson, 2003;Segall, 1992;Slack et al, 2013;Tsang and Witherspoon, 1981;Wang, 2000]. As an example, a rise in fluid pressure inside a fracture causes reversible deformation when the rock medium can be considered as elastic.…”

Section: Introductionmentioning

confidence: 99%

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Combining periodic hydraulic tests and surface tilt measurements to explore in situ fracture hydromechanics

et al. 2017

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Fractured bedrock reservoirs are of socio‐economical importance, as they may be used for storage or retrieval of fluids and energy. In particular, the hydromechanical behavior of fractures needs to be understood as it has implications on flow and governs stability issues (e.g., microseismicity). Laboratory, numerical, or field experiments have brought considerable insights to this topic. Nevertheless, in situ hydromechanical experiments are relatively uncommon, mainly because of technical and instrumental limitations. Here we present the early stage development and validation of a novel approach aiming at capturing the integrated hydromechanical behavior of natural fractures. It combines the use of surface tiltmeters to monitor the deformation associated with the periodic pressurization of fractures at depth in crystalline rocks. Periodic injection and withdrawal advantageously avoids mobilizing or extracting significant amounts of fluid, and it hinders any risk of reservoir failure. The oscillatory perturbation is intended to (1) facilitate the recognition of its signature in tilt measurements and (2) vary the hydraulic penetration depth in order to sample different volumes of the fractured bedrock around the inlet and thereby assess scale effects typical of fractured systems. By stacking tilt signals, we managed to recover small tilt amplitudes associated with pressure‐derived fracture deformation. Therewith, we distinguish differences in mechanical properties between the three tested fractures, but we show that tilt amplitudes are weakly dependent on pressure penetration depth. Using an elastic model, we obtain fracture stiffness estimates that are consistent with published data. Our results should encourage further improvement of the method.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Combining periodic hydraulic tests and surface tilt measurements to explore in situ fracture hydromechanics

et al. 2017

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“…RWFs have also been observed recently as part of hydromechanical slug testing using both an injection well and several monitoring wells in a fractured biotite gneiss (Slack et al ). The injection well was 60 m deep and the monitoring wells were located between 5.3 and 13.4 m away.…”

Section: Introductionmentioning

confidence: 88%

“…52, No. 1-Groundwater-January-February 2014 (pages 105-117) (Slack et al 2013). The injection well was 60 m deep and the monitoring wells were located between 5.3 and 13.4 m away.…”

Section: Introductionmentioning

confidence: 99%

Reverse Water‐Level Fluctuations Associated with Fracture Connectivity

et al. 2013

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Reverse water-level fluctuations (RWFs), a phenomenon in which water levels rise briefly in response to pumping, were detected in monitoring wells in a fractured siliciclastic aquifer system near a deep public supply well. The magnitude and timing of RWFs provide important information that can help interpret aquifer hydraulics near pumping wells. A RWF in a well is normally attributed to poroelastic coupling between the solid and fluid components in an aquifer system. In addition to revealing classical pumping-induced poroelastic RWFs, data from pressure transducers located at varying depths and distances from the public supply well suggest that the RWFs propagate rapidly through fractures to influence wells hundreds of meters from the pumping well. The rate and cycling frequency of pumping is an important factor in the magnitude of RWFs. The pattern of RWF propagation can be used to better define fracture connectivity in an aquifer system. Rapid, cyclic head changes due to RWFs may also serve as a mechanism for contaminant transport.

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“…We consider the Noordbergum effect and inverse‐pressure response (see recent papers by Murdoch and Germanovich [] and by Slack et al . []) to constitute such critical observations and employ our observations of the latter during pumping tests in a jointed aquifer in the testing of the developed numerical schemes.…”

Section: Introductionmentioning

confidence: 99%

A hybrid-dimensional approach for an efficient numerical modeling of the hydro-mechanics of fractures

2014

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Characterization of subsurface fluid flow requires accounting for hydro-mechanical coupling between fluid-pressure variations and rock deformation. Particularly, flow of a compressible fluid along compliant hydraulic conduits, such as joints, fractures, or faults, is strongly affected by the associated deformation of the surrounding rock. We investigated and compared two alternative numerical modeling approaches that describe the transient fluid-pressure distribution along a single deformable fracture embedded in a rock matrix. First, we analyzed the coupled hydro-mechanical problem within the framework of Biot's poroelastic equations. Second, in a hybrid-dimensional approach, deformation characteristics of the surrounding rock were combined with a one-dimensional approximation of the fluid-flow problem to account for the high aspect ratios of fractures and the associated numerical problems. A dimensional analysis of the governing equations reveals that the occurring physical phenomena strongly depend on the geometry of the hydraulic conduit and on the boundary conditions. For the analyzed geometries, hydromechanical coupling effects dominate and convection effects can be neglected. Numerical solutions for coupled hydro-mechanical phenomena were obtained and compared to field data to characterize the fractured rock in the vicinity of an injection borehole. Either approach captures convection, diffusion, and hydro-mechanical effects, yet the hybrid-dimensional approach is advantageous due to its applicability to problems involving high-aspect-ratio features. For such cases, the modeling of pumping tests by means of the hybrid-dimensional approach showed that the observed inverse-pressure responses are the result of the coupling between the fluid flow in the fracture and the rock deformation caused by fluid-pressure variations along the fracture. Storage capacity as a single parameter of a fracture is insufficient to address all aspects of the coupling.

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

Cited by 22 publications

References 30 publications

Combining periodic hydraulic tests and surface tilt measurements to explore in situ fracture hydromechanics

Combining periodic hydraulic tests and surface tilt measurements to explore in situ fracture hydromechanics

Reverse Water‐Level Fluctuations Associated with Fracture Connectivity

A hybrid-dimensional approach for an efficient numerical modeling of the hydro-mechanics of fractures

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