Experimental determination of subcritical crack growth parameters in sedimentary rock

Holder, Jon; Olson, Jon E.; Philip, Zeno

doi:10.1029/2000gl011918

Cited by 83 publications

(53 citation statements)

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“…Another feature of the length distributions from these simulations is that the cumulative frequency is very well described by a negative exponential function. This characteristic has been shown to be theoretically predicted if fracture length is limited by crack to crack mechanical interaction (Olson et al, 2001). The cumulative frequency distribution of spacing values (Figure 5.6) shows that changing the subcritical index from n=5 to n=20 causes a significant increase in fracture spacing, changing the median value from 2 meters to almost 6 meters.…”

Section: Numerical Resultsmentioning

confidence: 99%

“…At the beginning of a simulation, the flaw with the highest stress intensity propagates first, and the magnitude of the propagation velocity contrast between the higher and lower stress intensity cracks is defined by the power-law relationship of equation 1. Previous work has shown that for very low subcritical index values (n < 10) (Olson, 1993;Holder et al, 2001;Olson et al, 2001), many cracks propagate roughly at the same time and at the same velocity. Even flaws that are initially close together relative to the layer thickness increase in length at a comparable rate, penetrating one another's propagation exclusion zones prior to the stress relief being fully developed.…”

Section: Numerical Resultsmentioning

confidence: 99%

“…Some combination of increased fluid pressure, decreased confining stress and subcritical crack propagation is sufficient to drive crack growth (Engelder and Fisher, 1996;Olson, et al, 2001). Narrow-diameter bridges of vein-fill material having crack-seal texture are incompatible with models of fracture growth that call on cements to push fracture walls apart.…”

Section: Summary Of Evidence For Fracture Opening Mechanicsmentioning

confidence: 99%

“…The purpose of this observational work is to motivate fracture pattern models having equal mechanical and diagenetic components by illustrating a widespread but little appreciated by-product of these linked processes, namely crack-seal texture and associated fracture porosity. Mechanical and chemical processes such as compaction and cement precipitation govern rock-property history and chemical processes drive subcritical crack growth (Olson et al, 2001). Important effects on fracture mechanics and fracture patterns arise from cement precipitation within growing fractures (Olson, in press).…”

Section: Diagenesis and Fractures -Observationsmentioning

confidence: 99%

“…The power-law exponent, n, can vary widely depending on environmental conditions (such as dry versus wet) and rock type. Reported values for carbonates and sandstones vary from 20 or less for tests done in water to greater than 100 under dry conditions (Atkinson and Meredith, 1987;Holder et al, 2001). …”

Section: Subcritical Crack Growthmentioning

confidence: 99%

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Advanced Technology for Predicting the Fluid Flow Attributes of Naturally Fractured Reservoirs From Quantitative Geologic Data and Modeling

Olson

Lake

Laubach

2003

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Abstract:This report summarizes the work carried out during the period of September 29, 2000 to September 28, 2001. Our goal is to establish an integrated methodology of fractured reservoir characterization and show how that can be incorporated into fluid flow simulation. We have made progress in the characterization of mineral infilling of natural fractures. The main advancement in this regard was to recognize the strong interplay between diagenetic and mechanical processes. We accomplished several firsts in documenting and quantifying these processes, including documenting the range of emergent threshold in several formations and quantifying the internal structures of crack-seal bridges in fractures. These results will be the basis for an appreciation of fracture opening and filling rates that go well beyond our original goals. Looking at geochemical modeling of fracture infilling, our theoretical analysis addressed the problem of calcite precipitation in a fracture. We have built a model for the deposition of calcite within a fracture. The diagenetic processes of dissolution and partial cementation are key controls on the creation and distribution of natural fractures within hydrocarbon reservoirs. Even with extensive data collection, fracture permeability still creates uncertainty in reservoir description and the prediction of well performance. Data on the timing and stages of diagenetic events can provide explanation as to why, when and where natural fractures will be open and permeable. We have been pursuing the fracture mechanics testing of a wide range of rocks, particularly sandstone using a key rock property test that has hitherto not been widely applied to sedimentary rocks. A major accomplishment in this first year has been to identify sample suites available in the core repository at the University of Texas that represent a wide range of diagenetic alteration and to begin to test these samples. The basis for the fluid flow simulations to be carried out in this part of the project is the adequate spatial characterization of fracture networks. Our initial focus has been on the tendency of fracture sets to cluster into highly fracture zones that are often widely separated. Our preliminary modeling work shows the extent of this clustering to be controlled by the subcritical fracture index of the material. With continued progress, we move toward an integrated fracture characterization methodology that will ultimately be applied through detailed reservoir simulation.iv Fig. 3.1. Features associated with the crack-seal mechanism. Fig. 3.2. Evidence of fracture opening mechanics. Fig. 3.3. Demonstrations of how new imaging techniques reveal mechanically significant microstructures. Fig. 3.4. Internal structure of synkinematic cement bridges. Fig. 3.5. Complex crack-seal texture within an almost completely quartz-filled macrofracture. Fig. 3.6. Limited wavelength (UV-blue) gray-scale CL image showing crack-seal texture at the bases of euhedral quartz crystals growing into a macrofracture. Fig. 3.7. Compari...

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Section: Numerical Resultsmentioning

confidence: 99%

Section: Numerical Resultsmentioning

confidence: 99%

Section: Summary Of Evidence For Fracture Opening Mechanicsmentioning

confidence: 99%

Section: Diagenesis and Fractures -Observationsmentioning

confidence: 99%

Section: Subcritical Crack Growthmentioning

confidence: 99%

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Advanced Technology for Predicting the Fluid Flow Attributes of Naturally Fractured Reservoirs From Quantitative Geologic Data and Modeling

Olson

Lake

Laubach

2003

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Brittle and semibrittle creep of Tavel limestone deformed at room temperature

et al. 2017

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Deformation and failure mode of carbonate rocks depend on the confining pressure. In this study, the mechanical behavior of a limestone with an initial porosity of 14.7% is investigated at constant stress. At confining pressures below 55 MPa, dilatancy associated with microfracturing occurs during constant stress steps, ultimately leading to failure, similar to creep in other brittle media. At confining pressures higher than 55 MPa, depending on applied differential stress, inelastic compaction occurs, accommodated by crystal plasticity and characterized by constant ultrasonic wave velocities, or dilatancy resulting from nucleation and propagation of cracks due to local stress concentrations associated with dislocation pileups, ultimately causing failure. Strain rates during secondary creep preceding dilative brittle failure are sensitive to stress, while rates during compactive creep exhibit an insensitivity to stress indicative of the operation of crystal plasticity, in agreement with elastic wave velocity evolution and microstructural observations.

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Effect of water on critical and subcritical fracture properties of Woodford shale

2017

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Subcritical fracture behavior of shales under aqueous conditions is poorly characterized despite increased relevance to oil and gas resource development and seal integrity in waste disposal and subsurface carbon sequestration. We measured subcritical fracture properties of Woodford shale in ambient air, dry CO2 gas, and deionized water by using the double‐torsion method. Compared to tests in ambient air, the presence of water reduces fracture toughness by 50%, subcritical index by 77%, and shear modulus by 27% and increases inelastic deformation. Comparison between test specimens coated with a hydrophobic agent and uncoated specimens demonstrates that the interaction of water with the bulk rock results in the reduction of fracture toughness and enhanced plastic effects, while water‐rock interaction limited to the vicinity of the propagating fracture tip by a hydrophobic specimen coating lowers subcritical index and increases fracture velocity. The observed deviation of a rate‐dependent subcritical index from the power law K‐V relations for coated specimens tested in water is attributed to a time‐dependent weakening process resulting from the interaction between water and clays in the vicinity of the fracture tip.

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Experimental determination of subcritical crack growth parameters in sedimentary rock

Cited by 83 publications

References 16 publications

Advanced Technology for Predicting the Fluid Flow Attributes of Naturally Fractured Reservoirs From Quantitative Geologic Data and Modeling

Advanced Technology for Predicting the Fluid Flow Attributes of Naturally Fractured Reservoirs From Quantitative Geologic Data and Modeling

Brittle and semibrittle creep of Tavel limestone deformed at room temperature

Effect of water on critical and subcritical fracture properties of Woodford shale

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