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Role of rayleigh waves in rock mechanics
3A
analysed: (i) effects of differing mechanical properties between pay zone ard barrier formations, (2) effect of in-situ stress variations and (3) effect of hydrostatic pressure gradients on fracture propagation. 791017 HYDRAULIC FRACgURE PROPAGATION IN LAYERED FORMATIONS Daneshy, A A Soc Pet Engr J, V18, N1, Feb 1978, P33-41 Unobstructed fractures were shown experimentally to propagate with a decreasing fracturing fluid pressure, which agrees with theoretical predictions. Restrictions in fracture propagation result in an increase in fluid pressure. The relative fracturability of rocks was determined by direct experiment with composite samples of both rocks under test. Layered composite samples were used to study fracture extension in layered rocks. The strength of the interface is s h ~ n theoretically to be an important factor in fracture contair~nento
79lO18 THERMAL STRESSES NEAR A HEATED FRACTURE IN TRANSVERSELY ISOTROPIC OIL SHALE Closmann, P J; Phocas, D M Soc Pet Engr J, Vl8, N1, Feb 1978, P59-74 Presents a theoretical analysis to assess the feasibility of horizontally fracturing an oil shale formation by thermally biasing urdergrourd stresses. Results indicate that stresses induced by heating from a vertical fracture tend to reduce the chances of forming horizontal fractures at the vertical fracture face. 791019 CENTRIFUGE MODELLING OF EARTHQUAKES Liu, H P; Hagman, R L Geophys Res Lett, V5, NS, May 1978, P333-336 Fracture events by simulated tectonic stress loading in a model thrust fault have been generated when the model is subjected to 50 g in a centrifuge. 791020 FORMS OF HYDRAULIC FRACTURES AS DEDUCED FRC~4 FIELD STUDIES OF SHEET INTRUSIONS Pollard, D D Proc 19th US Symposium on Rock Mechanics, Stateline, Nevada, 1-3 May 1978, V1, PI- 9 . Publ Reno: University of Nevada, 1978 It is suggested that natural sheet intrusions may be good analogues for hydraulic fractures. The geologic setting of intrusions chosen for this study is similar to that of most hydraulic fractures: they formed at depths of less than 5kin in relatively unformed sedimentary rocks. Gross and detailed forms of sheet intrusions are described and illustrated diagrammatically, and the analogy between the processes of hydraulic fracturing and sheet intrusion is developed.
791021 ANOMALOUS FRACTURE-EXTENSION PRESSURES IN GRANITE Aamodt, R L; Proe 19th US Stateline, Publ Remo:
Potter, R M Symposit~n on Rock Mechanics, Nevada, 1-3 May 1978, Vl, PIO-13. University of Nevada, 1978
Fracture-extension Pressures appreciably higher than the least principal earth stress have been observed in hydraulic fractures formed in a pair of 3 km deep bore_holes drilled in Northern
New Mexico. Experiments to find fracture direction and extension pressures at these wells are described. 791022 HYDRAULIC FRACTURE PROPAGATION AND THE INTERPRETATION OF PRESSURE-TIME RECORDS FOR IN-SITU 9TRESS DETERMINATIONS Zoback I M D; pollard, D D Proc 19th US Symposium on Rock Mechanics, Stateline, Nevada, 1-3 May 1978 , V1, P1422. Publ Reno: University of Nevada, 1978 A theoretical study of the fracture initiation and extension process which derives a 2 dimensior~l, plane strain model for fracture extension based on a consideration of the elastic deformation of a fracture and viscous fluid flow into it. The model is used in analyses of stress intensity at the fracture tip and the accuracy of in situ stress determinations from fracture initiation and growth. 791023 STATISTICAL THEORY OF FRAGMENTATION Dienes, J K Proc 19th US Symposium on Rock Mechanics, Stateline, Nevada, 1-3 May 1978 , V1, P5155. Publ Reno: University of Nevada, 1978 An initially exponential distribution of cracks that grow in size and nucleate additional cracks is analysed, leading to an expression for the statistical distribution of cracks as a function of time in closed form. The results sre used to derive a reduced modulus for the cracked material. An approach to 3-dimensional calculations of fragmentation is also discussed Auth. 791024 TRACE LENGTH BIASES IN JOINT SURVEYS Baecher, G B; Lanney, N A Proc 19th US Symposium on Rock Mechanics, Stateline, Nevada, 1-3 May 1978, V1, P5665. Publ Reno: University of N e ~ a , 1978 Discusses the statistical biases associated with inferring Joint size frc~ trace lengths, and suggests techniques for dealing with them. 791025 ROLE OF RAYLEIGH WAVES IN ROCK ~CHANICS Rossmanith, H P Proc 19th US Symposium on Rock Mechanics, Stateline, Nevada, 1-3 May !978, V1, P139143. Publ Reno: University of Nevada, 1978 Considers Rayleigh wave propagation and interaction with pre-existing cracks as well as crack initiation caused by Rayleigh waves. Results obtained by photoelastic studies in recent years are reviewed briefly. 791026 Dm±'~a~MINATION OF EFFECTIVE ELASTIC MODULUS BY COMPLIANCE CALIBRATION FOR MEASUREMENT OF FRACTURE TOUGHNESS OF ROCK Kim, K; Stout, M G Proc 19th US Symposium on Rock Mechanics, Statelina, Nevada, 1-3 May 1978 , V1, P203209. Publ Reno: University of Nevada, 1978 P
The method described consists of testing a series of rock samples with various crack lengths and comparing the compliance vs. crack length curve thus obtained with that of a material of known elastic properties. Westerly granite samples were tested using double cantilever beam and double torsion fracture toughhess sample geometries. Results are cc~pared with other methods.
analysed: (i) effects of differing mechanical properties between pay zone ard barrier formations, (2) effect of in-situ stress variations and (3) effect of hydrostatic pressure gradients on fracture propagation. 791017 HYDRAULIC FRACgURE PROPAGATION IN LAYERED FORMATIONS Daneshy, A A Soc Pet Engr J, V18, N1, Feb 1978, P33-41 Unobstructed fractures were shown experimentally to propagate with a decreasing fracturing fluid pressure, which agrees with theoretical predictions. Restrictions in fracture propagation result in an increase in fluid pressure. The relative fracturability of rocks was determined by direct experiment with composite samples of both rocks under test. Layered composite samples were used to study fracture extension in layered rocks. The strength of the interface is s h ~ n theoretically to be an important factor in fracture contair~nento
79lO18 THERMAL STRESSES NEAR A HEATED FRACTURE IN TRANSVERSELY ISOTROPIC OIL SHALE Closmann, P J; Phocas, D M Soc Pet Engr J, Vl8, N1, Feb 1978, P59-74 Presents a theoretical analysis to assess the feasibility of horizontally fracturing an oil shale formation by thermally biasing urdergrourd stresses. Results indicate that stresses induced by heating from a vertical fracture tend to reduce the chances of forming horizontal fractures at the vertical fracture face. 791019 CENTRIFUGE MODELLING OF EARTHQUAKES Liu, H P; Hagman, R L Geophys Res Lett, V5, NS, May 1978, P333-336 Fracture events by simulated tectonic stress loading in a model thrust fault have been generated when the model is subjected to 50 g in a centrifuge. 791020 FORMS OF HYDRAULIC FRACTURES AS DEDUCED FRC~4 FIELD STUDIES OF SHEET INTRUSIONS Pollard, D D Proc 19th US Symposium on Rock Mechanics, Stateline, Nevada, 1-3 May 1978, V1, PI- 9 . Publ Reno: University of Nevada, 1978 It is suggested that natural sheet intrusions may be good analogues for hydraulic fractures. The geologic setting of intrusions chosen for this study is similar to that of most hydraulic fractures: they formed at depths of less than 5kin in relatively unformed sedimentary rocks. Gross and detailed forms of sheet intrusions are described and illustrated diagrammatically, and the analogy between the processes of hydraulic fracturing and sheet intrusion is developed.
791021 ANOMALOUS FRACTURE-EXTENSION PRESSURES IN GRANITE Aamodt, R L; Proe 19th US Stateline, Publ Remo:
Potter, R M Symposit~n on Rock Mechanics, Nevada, 1-3 May 1978, Vl, PIO-13. University of Nevada, 1978
Fracture-extension Pressures appreciably higher than the least principal earth stress have been observed in hydraulic fractures formed in a pair of 3 km deep bore_holes drilled in Northern
New Mexico. Experiments to find fracture direction and extension pressures at these wells are described. 791022 HYDRAULIC FRACTURE PROPAGATION AND THE INTERPRETATION OF PRESSURE-TIME RECORDS FOR IN-SITU 9TRESS DETERMINATIONS Zoback I M D; pollard, D D Proc 19th US Symposium on Rock Mechanics, Stateline, Nevada, 1-3 May 1978 , V1, P1422. Publ Reno: University of Nevada, 1978 A theoretical study of the fracture initiation and extension process which derives a 2 dimensior~l, plane strain model for fracture extension based on a consideration of the elastic deformation of a fracture and viscous fluid flow into it. The model is used in analyses of stress intensity at the fracture tip and the accuracy of in situ stress determinations from fracture initiation and growth. 791023 STATISTICAL THEORY OF FRAGMENTATION Dienes, J K Proc 19th US Symposium on Rock Mechanics, Stateline, Nevada, 1-3 May 1978 , V1, P5155. Publ Reno: University of Nevada, 1978 An initially exponential distribution of cracks that grow in size and nucleate additional cracks is analysed, leading to an expression for the statistical distribution of cracks as a function of time in closed form. The results sre used to derive a reduced modulus for the cracked material. An approach to 3-dimensional calculations of fragmentation is also discussed Auth. 791024 TRACE LENGTH BIASES IN JOINT SURVEYS Baecher, G B; Lanney, N A Proc 19th US Symposium on Rock Mechanics, Stateline, Nevada, 1-3 May 1978, V1, P5665. Publ Reno: University of N e ~ a , 1978 Discusses the statistical biases associated with inferring Joint size frc~ trace lengths, and suggests techniques for dealing with them. 791025 ROLE OF RAYLEIGH WAVES IN ROCK ~CHANICS Rossmanith, H P Proc 19th US Symposium on Rock Mechanics, Stateline, Nevada, 1-3 May !978, V1, P139143. Publ Reno: University of Nevada, 1978 Considers Rayleigh wave propagation and interaction with pre-existing cracks as well as crack initiation caused by Rayleigh waves. Results obtained by photoelastic studies in recent years are reviewed briefly. 791026 Dm±'~a~MINATION OF EFFECTIVE ELASTIC MODULUS BY COMPLIANCE CALIBRATION FOR MEASUREMENT OF FRACTURE TOUGHNESS OF ROCK Kim, K; Stout, M G Proc 19th US Symposium on Rock Mechanics, Statelina, Nevada, 1-3 May 1978 , V1, P203209. Publ Reno: University of Nevada, 1978 P
The method described consists of testing a series of rock samples with various crack lengths and comparing the compliance vs. crack length curve thus obtained with that of a material of known elastic properties. Westerly granite samples were tested using double cantilever beam and double torsion fracture toughhess sample geometries. Results are cc~pared with other methods.