Field evaluation of the hydromechanical behavior of flat-lying fractures during slug tests

Svenson, Erik; Schweisinger, Todd; Murdoch, Lawrence C.

doi:10.1016/j.jhydrol.2008.06.004

Cited by 26 publications

(31 citation statements)

References 24 publications

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“…The term a C w is generally negligible compared to C f , and with ρ w g = 10 4 N/m 3 , we obtain S ≃10 −5 (dimensionless). This order of magnitude lies in the lower end of estimates from cross‐borehole flowmeter test performed in the area by Le Borgne et al [] but is higher than typical results from comparable hydromechanical field experiments [ Burbey et al , ; Schweisinger et al , ; Svenson et al , ].…”

Section: Results and Interpretationmentioning

confidence: 99%

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: Results and Interpretationmentioning

confidence: 99%

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

et al. 2017

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“…A pneumatic system [ Svenson et al ., ] was used to rapidly change the pressure during the slug test. Straddle packers were used to isolate individual fractures or fracture sets.…”

Section: Field Experimentsmentioning

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 plausible that even slight changes in water pressure may affect fracture aperture and well testing results, analogous to the changes observed during hydro‐fracturing. There are few attempts to evaluate the hydromechanical response of a fractured rock to a slight change in water pressure (Cappa et al 2006; Svenson et al 2008; Schweisinger et al 2011). They installed the extensometers in a packed‐off section of boreholes in highly fractured rock aquifers, and measured the axial displacements and pressures during various well tests such as slug, pulse, and pumping tests.…”

Section: Introductionmentioning

confidence: 99%

Influence of Pressure Change During Hydraulic Tests on Fracture Aperture

Ji¹,

Koh

Kuhlman

et al. 2012

Groundwater

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In a series of field experiments, we evaluate the influence of a small water pressure change on fracture aperture during a hydraulic test. An experimental borehole is instrumented at the Korea Atomic Energy Research Institute (KAERI) Underground Research Tunnel (KURT). The target fracture for testing was found from the analyses of borehole logging and hydraulic tests. A double packer system was developed and installed in the test borehole to directly observe the aperture change due to water pressure change. Using this packer system, both aperture and flow rate are directly observed under various water pressures. Results indicate a slight change in fracture hydraulic head leads to an observable change in aperture. This suggests that aperture change should be considered when analyzing hydraulic test data from a sparsely fractured rock aquifer.

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Field evaluation of the hydromechanical behavior of flat-lying fractures during slug tests

Cited by 26 publications

References 24 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 change during interference slug tests in fractured rock

Influence of Pressure Change During Hydraulic Tests on Fracture Aperture

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