Chapter 10 Buoyancy-Driven Fracture and Magma Transport through the Lithosphere: Models and Experiments

Heimpel, Moritz; Olson, Peter

doi:10.1016/s0074-6142(09)60098-x

Cited by 62 publications

(116 citation statements)

References 31 publications

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“…Thus, p o is the pressure available to drive the fracture walls open at a particular point. The term "overpressure" in the sense used here is well-established in the technical literature (Heimpel and Olson, 1994;Bonafede and Rivalta, 1999a,b). However, p o is also referred to as driving pressure or driving stress (Pollard and Segall, 1987;Vermilye and Scholz, 1995;Dahm et al, 2010), or as net pressure (Valko and Economides, 1995).…”

Section: Fluid Overpressure Of Hydrofracturesmentioning

confidence: 99%

Effects of mechanical layering on hydrofracture emplacement and fluid transport in reservoirs

2013

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Fractures generated by internal fluid pressure, for example, dykes, mineral veins, many joints and man-made hydraulic fractures, are referred to as hydrofractures. Together with shear fractures, they contribute significantly to the permeability of fluid reservoirs such as those of petroleum, geothermal water, and groundwater. Analytical and numerical models show that-in homogeneous host rocks-any significant overpressure in hydrofractures theoretically generates very high crack tip tensile stresses. Consequently, overpressured hydrofractures should propagate and help to form interconnected fracture systems that would then contribute to the permeability of fluid reservoirs. Field observations, however, show that in heterogeneous and anisotropic, e.g., layered, rocks many hydrofractures become arrested or offset at layer contacts and do not form vertically interconnected networks. The most important factors that contribute to hydrofracture arrest are discontinuities (including contacts), stiffness changes between layers, and stress barriers, where the local stress field is unfavorable to hydrofracture propagation. A necessary condition for a hydrofracture to propagate to the surface is that the stress field along its potential path is everywhere favorable to extension-fracture formation so that the probability of hydrofracture arrest is minimized. Mechanical layering and the resulting heterogeneous stress field largely control whether evolving hydrofractures become confined to single layers (stratabound fractures) or not (non-stratabound fractures) and, therefore, if a vertically interconnected fracture system forms. Non-stratabound hydrofractures may propagate through many layers and generate interconnected fracture systems. Such systems commonly reach the percolation threshold and largely control the overall permeability of the fluid reservoirs within which they develop.

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Section: Fluid Overpressure Of Hydrofracturesmentioning

confidence: 99%

Effects of mechanical layering on hydrofracture emplacement and fluid transport in reservoirs

2013

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“…After an initial phase of growth in both horizontal and vertical directions, the vertical propagation due to buoyancy became predominant and a constant vertical velocity was established (as shown by Heimpel and Olson [1994]). In some cases a subtle increase of velocity occurred close to the surface, which has been interpreted in terms of an interaction with the free surface boundary condition at the upper surface by Rivalta et al [2005].…”

Section: Isothermal Experimentsmentioning

confidence: 99%

“…The two points that fall above the 1:1 line correspond to the lowest flux of injection for each of the two different fluids (experiments 4 and 6, respectively oil and heptane). As is the case in previously published work [e.g., Heimpel and Olson, 1994], we used different fluids to obtain varying amounts of buoyancy (see Table 1), some of which are hydrophobic (oils and heptane). The effect of the surface energy for experiments involving hydrophobic fluid Table 1): (left) smooth boundary between the fluid and the elastic medium, and how the thicker head can be identified by its stronger color; (right) photoelastic fringes that help visualize the geometry and intensity of the stress field around the head region.…”

Section: Isothermal Experimentsmentioning

confidence: 99%

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Effect of solidification on a propagating dike

Taisne

Tait

2011

J. Geophys. Res.

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[1] Magma migration through the brittle crust from depth occurs by the propagation of hydraulic fractures or dikes. Volcanic eruptions occur at the last stage if and when a propagating dike reaches the surface. Dike propagation involves complex physics because of several processes that are simultaneously occurring such as viscous flow of magma, rock fracture, elastic deformation of the host rock, and potentially large changes of the physical properties of the magma (crystallization, degassing, solidification, etc.). Currently the most practical way in the field or in terms of field measurements to follow the migration of magma before it reaches the surface is the analysis of the seismicity generated; nevertheless, a physical model that quantitatively relates the flux of magma in the dike to the seismicity is lacking. We present here laboratory experiments involving propagation of a fluid-filled crack such that the fluid solidifies upon contact with the cold elastic host. We show that this can lead to a way of estimating the flux of the injection as a function of the surface creation rate. The latter is shown to be a more reliable gauge of magma flux than the upward propagating velocity. In the geologic application of a propagating dike, the rate of creation of surface area may be related to the rate of release of seismic energy. Although this latter relation needs further work to be quantitatively reliable, our new model nevertheless indicates how a new general framework can be constructed.

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“…In those experiments, for which the strength of the gelatin was greatly reduced, crack velocities were observed to be two orders of magnitude greater than in experiments carried out with virgin gelatin but nonetheless were still lower by at least three orders of magnitude than velocity predicted by a Poiseuille flow, hence highlighting the role of the strength of gelatin. More recently, Heimpel and Olson [1994] put forward a new model for the propagation of cracks of constant volume, proposing notably that their speed might be limited by the transmission of information on the crack shape by elastic waves.…”

Section: Introductionmentioning

confidence: 99%

The propagation of a buoyant liquid‐filled fissure from a source under constant pressure: An experimental approach

2002

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[1] We study the propagation of a buoyant liquid-filled fissure from a reservoir under constant pressure within the framework of linear elastic fracture mechanics. We conducted laboratory experiments by injecting aqueous solutions into gelatin solid: an analogue for elastic and brittle crustal rocks. Fissure velocity and injection rate of liquid were measured rather than being imposed. Our experimental results allow evaluation of how the different driving and resistive pressures evolved during fissure propagation and highlight the influence of the fracture resistance of the host solid. In an initial transient propagation regime, elastic pressure generated by the fissure is balanced by the fracture pressure; the fissure propagates radially with decreasing velocity and increasing injection rate, controlled by the source conditions. Subsequently, buoyancy overcomes the source pressure as the driving force, and vertical steady state propagation is established. The fissure develops a bulbous head and propagation is controlled by the balance in this head, between buoyancy pressure and fracture pressure. Even after this transition, the constant values of velocity, flux, and strain energy release rate reflect the source conditions. Our model suggests that greater horizontal dyke cross section reflects larger source pressure and that mafic dykes propagating from shallow magma chambers are unlikely to attain steady state. Moreover, our experiments place constraints on the mechanics of time-dependent failure of the solid as a process that resists fissure propagation: propagation velocity scales with the square of the height of the fissure head, and fracture toughness of rocks would be length scale dependent rather than a material property.

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Chapter 10 Buoyancy-Driven Fracture and Magma Transport through the Lithosphere: Models and Experiments

Cited by 62 publications

References 31 publications

Effects of mechanical layering on hydrofracture emplacement and fluid transport in reservoirs

Effects of mechanical layering on hydrofracture emplacement and fluid transport in reservoirs

Effect of solidification on a propagating dike

The propagation of a buoyant liquid‐filled fissure from a source under constant pressure: An experimental approach

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