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Characterization of acoustic emission waveforms produced by rock during mode I and mode II crack propagation
140A 903074 Altered-stress fracturing Warpinski, N R: Branagan. P T J Pet Teclmol ~ 1 , N9. Sept 1989, P990-997
In some reservoirs, stress distribution is unfavourable for effective stimulation. For these cases, the concept of altered stress fracturing is introduced, where a hydraulic fracture at one well is reorientated by another at a nearly well. A field test is described in which stress changes of 1.7-2. ! MPa were measured at on offset well 37m away during treatment of a production well. Finite element reservoir analysis shows that altered stress fracturing is a valid concept and can lead to increased well production equivalent to much longer conventional hydraulic fractures. 903075 Impact of inducing fractures at Prudhoe Bay Williams, D B; Sherrard, D W: Lin. C Y J Pet Technol V41. NIO, Oct 1989, P1096-1101 Step rate tests at Prudhoe Bay water-injection wells showed that injecting cold seawater into the Ivishak reservoir at 93 deg C resulted in significant reduction of formation fracture gradient. This caused concern for waterflood management. A variety of simulation studies was used to identify fracture initiation pressures, and quantify the magnitude of fracturing and its effects on flood performance and oil production rates. Potentially negative effects are minimal, but benefits include accelerated oil production. An injection pressure limit above the thermally reduced formation fracture gradient has been adopted. 903076 Numerical study of violent rock failure by stick-slip on joints Zou, D; Miller, H D S: Kaiser. P K Min Sci Technol V9, N3. Nor 1989. P241-251 Violent rock failure has become a serious problem in deep hard rock mines in Canada. One cause, stick slip during shear along a stress induced fracture or natural geological discontinuity, is modelled mathematically. Conditions for violent rock failure are determined: high loading rate. high normal stress. and shear stress exceeding shear strength. Transition from stable sliding to stick slip is examined. Case studies investigate violent shear failure and violent failure of a rock specimen under compression. 903077 Coalbed methane - 4. Warrior basin drilling, stimulation covered Lambert, S W: Graves, S L: Jones, A H Oil Gas J 1/87. A'46, 13 Not" 1989, P87-92 Practices developed in the Black Warrior basin, Alabama, are reported. Drilling problems are encountered in the first 30m of strip mine rubble, which results in loss of circulation and alignment difficulties, and in regions of high water inflow. The reservoirs are of low permeability and operate at low pressure, and hydraulic fracturing treatments are appropriately designed. A typical fracture treatment of a well is illustrated, including variation of net pressure and fracture growth with time. 903078 Coalbed methane - 6. Western basins dictate varied operations Logan. T L Oil Gas J 1/87, N49, 4 Dec 1989, P35-39
Drilling, completion, and stimulation techniques used in Colorado and New Mexico are guided by reservoir characteristics such as permeability, saturation and pressure, and geological
characteristics such as coal rank.thickness, and natural fractures. Comparisons between water and gas geochemistry for coal bed and neighbouring sandstone reservoirs are presented. Open hole completion techniques are illustrated: early ope~l hole, open hole cavity, and cased hole fracture stimulated. Hydraulic fracturing stimulation and fracture geometry achieved are described.
903079 Brittle fracture criterion and experimental research in rock under mixed-mode loads Li Zhenzi; Li Liyun; Sun Zongqi Proc International Symposium on Modern .Alining Technology, Taian. October 1988 [395-402. Pttbl Taian: Shandong Institute of Mining and Technology. 1988
The relative accuracy of maximum stress, minimum strain, and maximum energy release fracture criteria has been examined using results from 3- and 4-point bending tests. A new equivalent circumferential strain criterion for mixed mode fracture initiation is proposed, which is well supported by experimental data.
903080 Characterization of acoustic emission waveforms produced by rock during mode I and mode !! crack propagation Glaser, S D; Nelson, P P Proc International Symposium on Rock at Great Depth, Pau. 28-31 August 1989 VI, P249-256. Publ Rotterdam: ,4 A Balkema. 1989
Large specimens approximately 0.6m by 0.3m by 0.3m were prepared. Chevron notch specimens were loaded in four point bending (mode I) and simple straight-edge notch beam specimens using the loading configuration of lngraffea (mode iI). Acoustic emission was monitored during fracture propagation. Equipment developed and signal processing techniques are described. Preliminary results from granite and dolostonc are presented. Similarity between sets of results suggests a similarity of internal mechanism during crack propagation in different rocks.
Time dependent behaviour See also." 903245. 903438
90308 i Effect of water on the rheology of experimentally deformed quartzite Koch, P S; Christie. J M; Ord, A; George, R P J Geophys Res V94. NBIO. Oct 1989, PI3975-13996
Empirical creep laws were determined for Simpson quartzite tested over the temperature range 750-900 deg C, 1.0-1.25 GPa confining pressure, at a range of strain rates. A Griggs-Blacic apparatus was used. As received (dry) specimens and those with water added via dehydration of a talc confining medium were tested. Constants of the creep laws were evaluated. Dry specimens were 1.5-2.5 times as strong as wet specimens under similar conditions. Recrystallisation was well developed in wet specimens only. Microstructures indicated recover.-, at flow stress below 500MPa. Deformation mechanisms are discussed.
1990 Pergamon Press pie. Reproduction not permitted
In some reservoirs, stress distribution is unfavourable for effective stimulation. For these cases, the concept of altered stress fracturing is introduced, where a hydraulic fracture at one well is reorientated by another at a nearly well. A field test is described in which stress changes of 1.7-2. ! MPa were measured at on offset well 37m away during treatment of a production well. Finite element reservoir analysis shows that altered stress fracturing is a valid concept and can lead to increased well production equivalent to much longer conventional hydraulic fractures. 903075 Impact of inducing fractures at Prudhoe Bay Williams, D B; Sherrard, D W: Lin. C Y J Pet Technol V41. NIO, Oct 1989, P1096-1101 Step rate tests at Prudhoe Bay water-injection wells showed that injecting cold seawater into the Ivishak reservoir at 93 deg C resulted in significant reduction of formation fracture gradient. This caused concern for waterflood management. A variety of simulation studies was used to identify fracture initiation pressures, and quantify the magnitude of fracturing and its effects on flood performance and oil production rates. Potentially negative effects are minimal, but benefits include accelerated oil production. An injection pressure limit above the thermally reduced formation fracture gradient has been adopted. 903076 Numerical study of violent rock failure by stick-slip on joints Zou, D; Miller, H D S: Kaiser. P K Min Sci Technol V9, N3. Nor 1989. P241-251 Violent rock failure has become a serious problem in deep hard rock mines in Canada. One cause, stick slip during shear along a stress induced fracture or natural geological discontinuity, is modelled mathematically. Conditions for violent rock failure are determined: high loading rate. high normal stress. and shear stress exceeding shear strength. Transition from stable sliding to stick slip is examined. Case studies investigate violent shear failure and violent failure of a rock specimen under compression. 903077 Coalbed methane - 4. Warrior basin drilling, stimulation covered Lambert, S W: Graves, S L: Jones, A H Oil Gas J 1/87. A'46, 13 Not" 1989, P87-92 Practices developed in the Black Warrior basin, Alabama, are reported. Drilling problems are encountered in the first 30m of strip mine rubble, which results in loss of circulation and alignment difficulties, and in regions of high water inflow. The reservoirs are of low permeability and operate at low pressure, and hydraulic fracturing treatments are appropriately designed. A typical fracture treatment of a well is illustrated, including variation of net pressure and fracture growth with time. 903078 Coalbed methane - 6. Western basins dictate varied operations Logan. T L Oil Gas J 1/87, N49, 4 Dec 1989, P35-39
Drilling, completion, and stimulation techniques used in Colorado and New Mexico are guided by reservoir characteristics such as permeability, saturation and pressure, and geological
characteristics such as coal rank.thickness, and natural fractures. Comparisons between water and gas geochemistry for coal bed and neighbouring sandstone reservoirs are presented. Open hole completion techniques are illustrated: early ope~l hole, open hole cavity, and cased hole fracture stimulated. Hydraulic fracturing stimulation and fracture geometry achieved are described.
903079 Brittle fracture criterion and experimental research in rock under mixed-mode loads Li Zhenzi; Li Liyun; Sun Zongqi Proc International Symposium on Modern .Alining Technology, Taian. October 1988 [395-402. Pttbl Taian: Shandong Institute of Mining and Technology. 1988
The relative accuracy of maximum stress, minimum strain, and maximum energy release fracture criteria has been examined using results from 3- and 4-point bending tests. A new equivalent circumferential strain criterion for mixed mode fracture initiation is proposed, which is well supported by experimental data.
903080 Characterization of acoustic emission waveforms produced by rock during mode I and mode !! crack propagation Glaser, S D; Nelson, P P Proc International Symposium on Rock at Great Depth, Pau. 28-31 August 1989 VI, P249-256. Publ Rotterdam: ,4 A Balkema. 1989
Large specimens approximately 0.6m by 0.3m by 0.3m were prepared. Chevron notch specimens were loaded in four point bending (mode I) and simple straight-edge notch beam specimens using the loading configuration of lngraffea (mode iI). Acoustic emission was monitored during fracture propagation. Equipment developed and signal processing techniques are described. Preliminary results from granite and dolostonc are presented. Similarity between sets of results suggests a similarity of internal mechanism during crack propagation in different rocks.
Time dependent behaviour See also." 903245. 903438
90308 i Effect of water on the rheology of experimentally deformed quartzite Koch, P S; Christie. J M; Ord, A; George, R P J Geophys Res V94. NBIO. Oct 1989, PI3975-13996
Empirical creep laws were determined for Simpson quartzite tested over the temperature range 750-900 deg C, 1.0-1.25 GPa confining pressure, at a range of strain rates. A Griggs-Blacic apparatus was used. As received (dry) specimens and those with water added via dehydration of a talc confining medium were tested. Constants of the creep laws were evaluated. Dry specimens were 1.5-2.5 times as strong as wet specimens under similar conditions. Recrystallisation was well developed in wet specimens only. Microstructures indicated recover.-, at flow stress below 500MPa. Deformation mechanisms are discussed.
1990 Pergamon Press pie. Reproduction not permitted