- Email: [email protected]
Slip systems in calcite single crystals deformed at 300–800 deg C
13A studied. Data were obtained on buildup of bottomhole pressure before breakdown, breakdown pressure at various injection rates and stress states, post-breakdown fracture propagation, and leakoff. Information on leakoff dominated material for use in numerical models was obtained.
941O96 Experimental study of well communication by hydraulic fracturing Guo, F; Morgenstern, N R; Scott, J D lnt J Rock Mecb Min Sci V30, N3, June 1993, P203-218 Using equipment described in a companion paper, the possibility of well communication by hydraulic fracturing was examined in tests on large gypstone blocks under true triaxial stress. The angle between interwell line and direction of maximum principal stress was varied, as was ratio of principal stresses. Conditions for which communication was obtained and where fracture orientation could be predicted are discussed.
941097 Growth of a crack produced by hydraulic fracture in a poroelastic medium Gordeyev, Y N int J Rock Mech Min Sci V30, N3, June 1993, P233-238 The hydraulic fracture process in a poroelastic medium can be described by 2 sets of equations, one dealing with rock deformation and the other with fluid flow in pores and fractures. An axisymmetric/plane strain model is presented with integral formulae coupling fracture aperture with fluid pressure and leakage along fracture walls. The analysis is based on the formalism of the theory of analytic/generalised analytic functions. The exact solution is obtained for the axisymmetric steady state ideal fracture.
941098 Infiltration effects in the tensile rupture of thin walled cylinders of glass and granite: implications for the hydraulic fracturing breakdown equation Schmitt, D R; Zoback, M D lnt J Rock Mech Min Sci V30, N3, June 1993, P289-303 Experiments to examine the effects of fluid infiltration on tensile rupture of low porosity rock subject to high initial pore pressures are described. The experimental conditions are analogous to those in field hydraulic fracturing. Cylinders of glass and Westerly granite were internally pressurised at different rates and at different confining pressures. Measured failure pressures are compared to those predicted by purely elastic and Biot poroelastic formulations. Implications of results for hydraulic fracturing stress measurements in low porosity crystalline rocks are examined.
941100 Effect of loading rate on crack propagation under compressive stress in a saturated porous material Atkinson, C; Cook, J M J Geophys Res V98, NB4, April 1993, P6383-6395 A simple model is presented to describe the influence of pore fluids in a rock on the initiation and propagation of fractures. Effects of loading rate and other parameters on propagation of a tensile crack in a low permeability fluid-saturated porous material are examined. As loading rate is increased, crack growth rate is decreased as fluid pressure within the crack falls. Similar effects are seen with increasing fracture toughness or decreasing far-field pore pressure. For shale tested under laboratory limitations, replacement of tensile fractures by shear fractures is not found.
941101 Slip systems in calcite single crystals deformed at 300-800 deg C de Bresser, J H P; Spiers, C J J Geopbys Res V98, NB4, April 1993, P6397-6409 Uniaxial compression tests were carried out on calcite single crystals at constant strain rate and in the temperature range 300-800 deg C. A single strain rate cycling test was performed at 650 deg C. Axial strains of 5-16% were imposed. A three stage hardening behaviour was found. The strain rate cycling test indicated flow stress is rather insensitive to strain rate. Important high temperature slip systems have been identified for use in textural development and modelling studies.
941102 Effect of thermal regime on growth increment and spacing of contraction joints in basaltic lava De Graft, J M; Aydin, A J Geopbys Res II98, NB4, April 1993, P6411-6430 Thermal contraction cracks forming columnar joints in volcanic rocks grow incrementally towards the interior of a cooling intrusion by successive formation of new segments on the joint edges. Growth increments and spacing of joints in basaltic lava have been measured and the observations modelled using fracture mechanics principles. Joints will propagate when tensile stress at the crack tip exceeds the fracture resistance of the lava and will be arrested when the crack tip reaches hot, ductile lava with high fracture resistance. Solidification rate and thermal gradient have important influence on joint spacing.
941099 Crack development and acoustic emission in potash rock Mlakar, V; Hassan, F P; Momayez, M lnt J Rock Mech Min Sci V30, N3, June 1993, P305-319
941103 Scale invariance in stochastic fracture of rocks Siiberschmidt, V V Proc Second International Conference on Scale Effects in Rock Masses, Lisbon, 25 June 1993 P49-54. Publ Rotterdam: A A Balkema, 1993
Uniaxial compression tests with AE measurement were carried out on samples of potash rock from Saskatoon. Event history is compared to deformational features identified by optical and electron microscopy. Although the rock can be divided into classes on the basis of colour pattern, mineral ratios, and texture, it is shown that analysis of AE data collected during a complete load cycle can provide a general picture of AE behaviour. Detailed analysis of AE parameters can be used to monitor fracture propagation.
Brittle fracture of stochastic heterogeneous materials depends on the evolution and accumulation of damage and its interaction with joints, which are nonuniform in space and time. Approaches based on fractal theory are proposed to simplify description of such processes and account for scale effects, and to obtain quantitative information on spatial and temporal invariance. Analysis of load vs time-to-fracture dependence for a large range of loads confirms the scale invariance of the fracture process.
941O96 Experimental study of well communication by hydraulic fracturing Guo, F; Morgenstern, N R; Scott, J D lnt J Rock Mecb Min Sci V30, N3, June 1993, P203-218 Using equipment described in a companion paper, the possibility of well communication by hydraulic fracturing was examined in tests on large gypstone blocks under true triaxial stress. The angle between interwell line and direction of maximum principal stress was varied, as was ratio of principal stresses. Conditions for which communication was obtained and where fracture orientation could be predicted are discussed.
941097 Growth of a crack produced by hydraulic fracture in a poroelastic medium Gordeyev, Y N int J Rock Mech Min Sci V30, N3, June 1993, P233-238 The hydraulic fracture process in a poroelastic medium can be described by 2 sets of equations, one dealing with rock deformation and the other with fluid flow in pores and fractures. An axisymmetric/plane strain model is presented with integral formulae coupling fracture aperture with fluid pressure and leakage along fracture walls. The analysis is based on the formalism of the theory of analytic/generalised analytic functions. The exact solution is obtained for the axisymmetric steady state ideal fracture.
941098 Infiltration effects in the tensile rupture of thin walled cylinders of glass and granite: implications for the hydraulic fracturing breakdown equation Schmitt, D R; Zoback, M D lnt J Rock Mech Min Sci V30, N3, June 1993, P289-303 Experiments to examine the effects of fluid infiltration on tensile rupture of low porosity rock subject to high initial pore pressures are described. The experimental conditions are analogous to those in field hydraulic fracturing. Cylinders of glass and Westerly granite were internally pressurised at different rates and at different confining pressures. Measured failure pressures are compared to those predicted by purely elastic and Biot poroelastic formulations. Implications of results for hydraulic fracturing stress measurements in low porosity crystalline rocks are examined.
941100 Effect of loading rate on crack propagation under compressive stress in a saturated porous material Atkinson, C; Cook, J M J Geophys Res V98, NB4, April 1993, P6383-6395 A simple model is presented to describe the influence of pore fluids in a rock on the initiation and propagation of fractures. Effects of loading rate and other parameters on propagation of a tensile crack in a low permeability fluid-saturated porous material are examined. As loading rate is increased, crack growth rate is decreased as fluid pressure within the crack falls. Similar effects are seen with increasing fracture toughness or decreasing far-field pore pressure. For shale tested under laboratory limitations, replacement of tensile fractures by shear fractures is not found.
941101 Slip systems in calcite single crystals deformed at 300-800 deg C de Bresser, J H P; Spiers, C J J Geopbys Res V98, NB4, April 1993, P6397-6409 Uniaxial compression tests were carried out on calcite single crystals at constant strain rate and in the temperature range 300-800 deg C. A single strain rate cycling test was performed at 650 deg C. Axial strains of 5-16% were imposed. A three stage hardening behaviour was found. The strain rate cycling test indicated flow stress is rather insensitive to strain rate. Important high temperature slip systems have been identified for use in textural development and modelling studies.
941102 Effect of thermal regime on growth increment and spacing of contraction joints in basaltic lava De Graft, J M; Aydin, A J Geopbys Res II98, NB4, April 1993, P6411-6430 Thermal contraction cracks forming columnar joints in volcanic rocks grow incrementally towards the interior of a cooling intrusion by successive formation of new segments on the joint edges. Growth increments and spacing of joints in basaltic lava have been measured and the observations modelled using fracture mechanics principles. Joints will propagate when tensile stress at the crack tip exceeds the fracture resistance of the lava and will be arrested when the crack tip reaches hot, ductile lava with high fracture resistance. Solidification rate and thermal gradient have important influence on joint spacing.
941099 Crack development and acoustic emission in potash rock Mlakar, V; Hassan, F P; Momayez, M lnt J Rock Mech Min Sci V30, N3, June 1993, P305-319
941103 Scale invariance in stochastic fracture of rocks Siiberschmidt, V V Proc Second International Conference on Scale Effects in Rock Masses, Lisbon, 25 June 1993 P49-54. Publ Rotterdam: A A Balkema, 1993
Uniaxial compression tests with AE measurement were carried out on samples of potash rock from Saskatoon. Event history is compared to deformational features identified by optical and electron microscopy. Although the rock can be divided into classes on the basis of colour pattern, mineral ratios, and texture, it is shown that analysis of AE data collected during a complete load cycle can provide a general picture of AE behaviour. Detailed analysis of AE parameters can be used to monitor fracture propagation.
Brittle fracture of stochastic heterogeneous materials depends on the evolution and accumulation of damage and its interaction with joints, which are nonuniform in space and time. Approaches based on fractal theory are proposed to simplify description of such processes and account for scale effects, and to obtain quantitative information on spatial and temporal invariance. Analysis of load vs time-to-fracture dependence for a large range of loads confirms the scale invariance of the fracture process.