- Email: [email protected]
Laboratory investigation of acoustic emission and elastic wave velocity changes during rock failure under triaxial stresses
152A 903171 Laboratory investigation of acoustic emission and elastic wave velocity changes during rock failure under triaxial stresses Sammonds, P R: Ayling, M R; Meredith, PG: Murrell, SA F: Jones, C Proc International Symposium on Rock at Great Depth, Pau. 28-31 August 1989 VI, P233-240. Publ Rotterdam: ,4 A Balkema, 1989 15mm diameter samples of Darley Dale sandstone were subjected to triaxial compression tests at room temperature and confining pressures up to 200MPa. Changes in P- and S-wave velocities and rate and amplitude distribution of acoustic emission events with deformation were studied. Wave velocities initially increased during closure of pre-existing cracks and pores, then decreased during dilatant microcracking. Acoustic emission event rate was initially low but increased rapidly up to failure. The seismic b-value, which characterises amplitude distribution of seismic events, decreased prior to brittle failure.
903172 Acoustic compressional wave velocity and dilatancy in triaxially stressed rock Jones, C; Murrell, S A F Proc International Symposium on Rack at Great Depth, Pau, 28-31 August 1989 Vl. P241-247. Publ Rotter&tin." A A Balkema, 1989 Tests on limestone and sandstone rock under triaxial compression with measurement of P wave velocity are described. Under hydrostatic pressure, closure of pre-existing cracks and pores causes increase in Vp. Additional uniaxial compression under triaxial stress shows increase in Vp until dilatant cracking occurs. At low confining pressure, Vp decreases until a steady value, which is maintained till fracture. At higher confining pressure, cataclastic flow occurs with dilatant cracking until high strains, with consequent reduction of Vp. At higher temperatures, plastic flow dominates and there is no evidence of dilatancy. Pore fluid flows associated with di!atancy cause changes in Vp in saturated rocks.
903 ! 73 Effect of confining pressure on intrinsic damping of sonic frequency waves: laboratory methods and some results in nonargillaceous rocks (in French) Lucet, N; Zinszner, B Proc International Symposium on Rock at Great Depth, Pau, 28-31 August 1989 VI, P257-264. Publ Rotterdam: A A Balkema. 1989 Although intrinsic damping of acoustic waves is recognised as important in interpretation of field tests using acoustic techniques, most published data concern rocks tested without confining pressure. An apparatus has been developed which allows measurements to be made at confining pressures up to 45MPa and in the frequency range 2-20kHz. Results from large numbers of specimens are presented. Effective pressure has a marked effect on damping. For saturated, non-argillaceous rocks, intrinsic damping falls with confining pressure to become almost negligible at pressure found in petroleum reservoirs.
903174 Shear-wave birefringence and directional permeability in fractured rock King, M S; Xu, S Proc International Symposium on Rock at Great Depth, Pau, 28-31 August 1989 V1. P265-272. Publ Rotterdam: ~4 .4 Balkema. 1989 Elastic wave propagation and permeability were measured on a slate before cracking and after oriented cracks were induced. P and S wave velocities, having particle motion parallel to and perpendicular to the sets of cracks, were determined concurrently with permeability measured in the same direction. Velocity and permeability changed markedly with each loading cycle. A near linear relation is seen between velocity of S waves polarised perpendicular to the cracks and permeability. This indicates a possibility of monitoring permeability of reservoir rocks using seismic data. 903175 Acoustic measurements on artificial rock van Baaren, J P; Heller, H K J; Visser, R Proc International Symposium on Rock at Great Depth, Pau, 28-31 August 1989 VI. P283-290. Publ Rotterdam: ,4 ,4 Balkema. 1989 Tests were carried out on an artificial reservoir rock in a borehole simulator. The data acquisition system, the triaxial cell system which can simulate reservoir conditions to 4000m depth, and the laboratory procedure to produce artificial sandstones by cementing loose grains together at grain contacts are described. Acoustic measurements made in the rock are presented, and results compared to predictions of a theoretical model developed to describe the received signals. 903176 High temperature triaxial apparatus for acoustic measurements Murrell, S A F: Meredith, PG; Sammonds, P R; Ayling, M R; Jones, C Proc International Symposium on Rock at Great Depth, Pau, 28-31 August 1989 VI, P291-296. Publ Rotterdam: A ,4 Balkema. 1989 A triaxial cell is described which can achieve crustal confining pressure (1000MPa) and sample temperatures up to 1000 deg C. Rock samples of 10-20ram diameter can be tested under servo controlled and pore pressure conditions. The velocity of IMHz acoustic waves along the axis of the specimen can bc measured, together with simultaneous measurement of acoustic emission. 903177 Effects of in situ stress relaxation on velocity anisotropy of ultrasonic P and S waves in rock core samples (In French) Rasolofosaon, P N J; Zinszner, B Proc International Symposium on Rock at Great Depth, Pau, 28-31 August 1989 VI. P305-312. Publ Rotterdam." ,4 ,4 Balkema. 1989 In situ stress direction is useful information in studying petroleum reservoirs. A core based method has been developed to determine stress directions from the directions of relaxation microcracking, deduced from measurement of acoustic anisotropy. Anisotropy of ultrasonic P wave velocity and birefringence of shear waves were determined on two sets of samples, one from depth, the other near surface, which are otherwise similar. If relaxation microfissures are likely, then determination of principal in situ stress direction is possible.
(' 1990 Pergamon Press plc. Reproduction not permitted
903172 Acoustic compressional wave velocity and dilatancy in triaxially stressed rock Jones, C; Murrell, S A F Proc International Symposium on Rack at Great Depth, Pau, 28-31 August 1989 Vl. P241-247. Publ Rotter&tin." A A Balkema, 1989 Tests on limestone and sandstone rock under triaxial compression with measurement of P wave velocity are described. Under hydrostatic pressure, closure of pre-existing cracks and pores causes increase in Vp. Additional uniaxial compression under triaxial stress shows increase in Vp until dilatant cracking occurs. At low confining pressure, Vp decreases until a steady value, which is maintained till fracture. At higher confining pressure, cataclastic flow occurs with dilatant cracking until high strains, with consequent reduction of Vp. At higher temperatures, plastic flow dominates and there is no evidence of dilatancy. Pore fluid flows associated with di!atancy cause changes in Vp in saturated rocks.
903 ! 73 Effect of confining pressure on intrinsic damping of sonic frequency waves: laboratory methods and some results in nonargillaceous rocks (in French) Lucet, N; Zinszner, B Proc International Symposium on Rock at Great Depth, Pau, 28-31 August 1989 VI, P257-264. Publ Rotterdam: A A Balkema. 1989 Although intrinsic damping of acoustic waves is recognised as important in interpretation of field tests using acoustic techniques, most published data concern rocks tested without confining pressure. An apparatus has been developed which allows measurements to be made at confining pressures up to 45MPa and in the frequency range 2-20kHz. Results from large numbers of specimens are presented. Effective pressure has a marked effect on damping. For saturated, non-argillaceous rocks, intrinsic damping falls with confining pressure to become almost negligible at pressure found in petroleum reservoirs.
903174 Shear-wave birefringence and directional permeability in fractured rock King, M S; Xu, S Proc International Symposium on Rock at Great Depth, Pau, 28-31 August 1989 V1. P265-272. Publ Rotterdam: ~4 .4 Balkema. 1989 Elastic wave propagation and permeability were measured on a slate before cracking and after oriented cracks were induced. P and S wave velocities, having particle motion parallel to and perpendicular to the sets of cracks, were determined concurrently with permeability measured in the same direction. Velocity and permeability changed markedly with each loading cycle. A near linear relation is seen between velocity of S waves polarised perpendicular to the cracks and permeability. This indicates a possibility of monitoring permeability of reservoir rocks using seismic data. 903175 Acoustic measurements on artificial rock van Baaren, J P; Heller, H K J; Visser, R Proc International Symposium on Rock at Great Depth, Pau, 28-31 August 1989 VI. P283-290. Publ Rotterdam: ,4 ,4 Balkema. 1989 Tests were carried out on an artificial reservoir rock in a borehole simulator. The data acquisition system, the triaxial cell system which can simulate reservoir conditions to 4000m depth, and the laboratory procedure to produce artificial sandstones by cementing loose grains together at grain contacts are described. Acoustic measurements made in the rock are presented, and results compared to predictions of a theoretical model developed to describe the received signals. 903176 High temperature triaxial apparatus for acoustic measurements Murrell, S A F: Meredith, PG; Sammonds, P R; Ayling, M R; Jones, C Proc International Symposium on Rock at Great Depth, Pau, 28-31 August 1989 VI, P291-296. Publ Rotterdam: A ,4 Balkema. 1989 A triaxial cell is described which can achieve crustal confining pressure (1000MPa) and sample temperatures up to 1000 deg C. Rock samples of 10-20ram diameter can be tested under servo controlled and pore pressure conditions. The velocity of IMHz acoustic waves along the axis of the specimen can bc measured, together with simultaneous measurement of acoustic emission. 903177 Effects of in situ stress relaxation on velocity anisotropy of ultrasonic P and S waves in rock core samples (In French) Rasolofosaon, P N J; Zinszner, B Proc International Symposium on Rock at Great Depth, Pau, 28-31 August 1989 VI. P305-312. Publ Rotterdam." ,4 ,4 Balkema. 1989 In situ stress direction is useful information in studying petroleum reservoirs. A core based method has been developed to determine stress directions from the directions of relaxation microcracking, deduced from measurement of acoustic anisotropy. Anisotropy of ultrasonic P wave velocity and birefringence of shear waves were determined on two sets of samples, one from depth, the other near surface, which are otherwise similar. If relaxation microfissures are likely, then determination of principal in situ stress direction is possible.
(' 1990 Pergamon Press plc. Reproduction not permitted