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Fracturing of high-temperature, naturally fissured, gas-condensate reservoirs
13A 931092 Ultrasonic tomography and acoustic emission in hydraulically fractured Lac du Bonnet grey granite Falls, S D; Young, R P; Carlson, S R; Chow, T J Geophys Res V97, NB5, May 1992, P6867-6884 Two large unconfined cylinders of Lac du Bonnet granite were internally pressurised over several cycles until final failure. Ultrasonic tomography and AE data were collected during the hydrofracturing. Compressional velocities were seen to be strongly anisotropic, related to the pre-existing microcrack fabric, and increased during the course of the experiment due to fluid penetration. Velocity changes can be related to initial crack density and relative distance from the borehole. Two distinct fracture planes were delineated in one sample from analysis of AE locations.
931O96 Kaiser effect in intact rock: current status as a feasible means of evaluating thermal and mechanical loading Montoto, M; Hardy, H R Proe 7th I S R M International Congress on Rock Mechanics, Aachen, 16-20 September 1991 V1, P569-572. Publ Rotterdam: A A Balkema, 1991 An update review of studies on the Kaiser effect in geological materials is presented. Both mechanical and thermal loading have been considered. Amongst aspects investigated are effects of specimen environment, memory loss, test procedures, determination of the Kaiser stress level, and multiaxial stress states. It is indicated that the Kaiser effect provides a basis for inexpensive and convenient assessment of in situ stress in geological materials.
931093 Fracturing of high-temperature, naturally fissured, gascondensate reservoirs Cikes, M; Economides, M J SPE Prod Engng V7, N2, May 1992, P226-232
931097 Core relaxation measurements on compacted sedimentary formations (well Ba 1) Deflandre, J P; Sarda, J P Proc 33rd US Symposium on Rock Mechanics, Santa Fe, 3-5 June 1992 P49-57. Publ Rotterdam: A A Balkema, 1992
Descriptions are given of 11 fracturing treatments at depths 3300-3800m, temperatures 180-195 deg C, in naturally fractured gas condensate reservoirs. The wells in the Molve, Kalinovac, and Staff Gradac fields in Croatia are in carbonate schist, quartzite, dolomite, and carbonate rocks. Earlier results indicate the effective fracture length in naturally fractured rock is less than that expected from the well known constant height, ideal fracture geometry models which assume homogeneous isotropic media. Careful modification of fracturing fluids to match the expected in situ conditions allowed successful fracturing treatment to be carried out.
Six oriented cores (microcrystalline limestone, limestone, sandy dolomite,argillaceous/dolomitic siltstone, and silty and shaly dolomite) were recovered from depths 1223.8-1473.9m from a site at Balazuc, Ardeche, France. Anelastic strain measurements (ASR) were made on the cores, anisotropy of P and S wave velocities measured, X ray tomographic images obtained, and permeability and porosity determined. There was no evidence of microcracking during ASR. An attempt is made to interpret core relaxation in terms of site geology, petrographic properties and ASR data.
931094 Self-similar solution for deep-penetrating hydraulic fracture problem Gordeyev, Y N; Zazovsky, A F Trans Porous Media V7, N3, March 1992, P283-304
931098 Field comparison of techniques for determining the direction of hydraulic fractures Yale, D P; Strubhar, M K; El Rabaa, A W Proc 33rd US Symposium on Rock Mechanics, Santa Fe, 3-5 June 1992 P89-98. Publ Rotterdam: A A Balkema, 1992
The propagation of a vertical rectangular hydraulic fracture of constant height and highly elongated in the horizontal direction, driven by constant pressure injection of a viscous fluid which displaces the formation fluid in a piston-like manner, is analysed. The fracturing fluid is considered incompressible and strata fluid motion is governed by the equation of transient seepage flow in a porous medium. A self-similar solution to the problem is developed assuming a quasi-steady state character of fracturing fluid flow in a crack and in a stratum and locally one-dimensional fluid loss through crack surfaces. Influence of formation permeability and fracturing fluid viscosity on major characteristics of the hydraulic fracturing are assessed. 931095 Drill-back studies examine fractured, heated rock Wollenberg, H A; Flexser, S; Myer, L R Proc 1st Annual Topical Meeting on High Level Radioactive Waste Management, Las Vegas, 8-12 April 1990 V1, P603610. Publ La Grange Park: ANS/ASCE, 1990 Cores have been retrieved for examination from granitic rock where heater tests have simulated repository conditions and from holes penetrating a natural hydrothermal system in tuff. Distribution of natural uranium has been examined. Localised mobility and deposition in open fractures in the granite and in a breccia zone and fracture filling material in tuff are seen. Seismic and microstructural studies of heated and less heated rocks indicate increasing microcrack density with increasing level of thermally induced stress.
Six different techniques for determining or predicting azimuthal orientation of hydraulic fractures were tested in four wells in New Mexico: shear acoustic anisotropy measurements on oriented core; anelastic strain recovery measurements on oriented core; overcoring of fractures from microfrac tests; inspection of natural and coring induced fractures in oriented cores; borehole monitoring of fracture-related microseismicity; and borehole televiewer examination. Similar results were obtained in all cases, with only small variations between wells. Reliability, cost effectiveness, and predictive ability are discussed.
Time dependent behaviour See also: 931348 931099 Influence of cycling pore-water pressures and principal stress ratios on drained deformations in clay. Note Eigenbrod, K D; Graham, J; Burak, J P Can Geotech d V29, N2, April 1992, P326-333 Seasonal changes in groundwater levels are known to affect the rate of downward creep of clay slopes. To investigate this effect, undisturbed clay specimens were anisotropically consolidated to in-slope conditions, then pore pressures systematically cycled over periods of 4-48hr. Axial and volume strains were measured, lateral and shear strains calculated. Strain rates decreased with total time of testing. For a given elapsed
© 1993 Pergamon Press Ltd. Reproduction not permitted RMMS 30/I--G
931O96 Kaiser effect in intact rock: current status as a feasible means of evaluating thermal and mechanical loading Montoto, M; Hardy, H R Proe 7th I S R M International Congress on Rock Mechanics, Aachen, 16-20 September 1991 V1, P569-572. Publ Rotterdam: A A Balkema, 1991 An update review of studies on the Kaiser effect in geological materials is presented. Both mechanical and thermal loading have been considered. Amongst aspects investigated are effects of specimen environment, memory loss, test procedures, determination of the Kaiser stress level, and multiaxial stress states. It is indicated that the Kaiser effect provides a basis for inexpensive and convenient assessment of in situ stress in geological materials.
931093 Fracturing of high-temperature, naturally fissured, gascondensate reservoirs Cikes, M; Economides, M J SPE Prod Engng V7, N2, May 1992, P226-232
931097 Core relaxation measurements on compacted sedimentary formations (well Ba 1) Deflandre, J P; Sarda, J P Proc 33rd US Symposium on Rock Mechanics, Santa Fe, 3-5 June 1992 P49-57. Publ Rotterdam: A A Balkema, 1992
Descriptions are given of 11 fracturing treatments at depths 3300-3800m, temperatures 180-195 deg C, in naturally fractured gas condensate reservoirs. The wells in the Molve, Kalinovac, and Staff Gradac fields in Croatia are in carbonate schist, quartzite, dolomite, and carbonate rocks. Earlier results indicate the effective fracture length in naturally fractured rock is less than that expected from the well known constant height, ideal fracture geometry models which assume homogeneous isotropic media. Careful modification of fracturing fluids to match the expected in situ conditions allowed successful fracturing treatment to be carried out.
Six oriented cores (microcrystalline limestone, limestone, sandy dolomite,argillaceous/dolomitic siltstone, and silty and shaly dolomite) were recovered from depths 1223.8-1473.9m from a site at Balazuc, Ardeche, France. Anelastic strain measurements (ASR) were made on the cores, anisotropy of P and S wave velocities measured, X ray tomographic images obtained, and permeability and porosity determined. There was no evidence of microcracking during ASR. An attempt is made to interpret core relaxation in terms of site geology, petrographic properties and ASR data.
931094 Self-similar solution for deep-penetrating hydraulic fracture problem Gordeyev, Y N; Zazovsky, A F Trans Porous Media V7, N3, March 1992, P283-304
931098 Field comparison of techniques for determining the direction of hydraulic fractures Yale, D P; Strubhar, M K; El Rabaa, A W Proc 33rd US Symposium on Rock Mechanics, Santa Fe, 3-5 June 1992 P89-98. Publ Rotterdam: A A Balkema, 1992
The propagation of a vertical rectangular hydraulic fracture of constant height and highly elongated in the horizontal direction, driven by constant pressure injection of a viscous fluid which displaces the formation fluid in a piston-like manner, is analysed. The fracturing fluid is considered incompressible and strata fluid motion is governed by the equation of transient seepage flow in a porous medium. A self-similar solution to the problem is developed assuming a quasi-steady state character of fracturing fluid flow in a crack and in a stratum and locally one-dimensional fluid loss through crack surfaces. Influence of formation permeability and fracturing fluid viscosity on major characteristics of the hydraulic fracturing are assessed. 931095 Drill-back studies examine fractured, heated rock Wollenberg, H A; Flexser, S; Myer, L R Proc 1st Annual Topical Meeting on High Level Radioactive Waste Management, Las Vegas, 8-12 April 1990 V1, P603610. Publ La Grange Park: ANS/ASCE, 1990 Cores have been retrieved for examination from granitic rock where heater tests have simulated repository conditions and from holes penetrating a natural hydrothermal system in tuff. Distribution of natural uranium has been examined. Localised mobility and deposition in open fractures in the granite and in a breccia zone and fracture filling material in tuff are seen. Seismic and microstructural studies of heated and less heated rocks indicate increasing microcrack density with increasing level of thermally induced stress.
Six different techniques for determining or predicting azimuthal orientation of hydraulic fractures were tested in four wells in New Mexico: shear acoustic anisotropy measurements on oriented core; anelastic strain recovery measurements on oriented core; overcoring of fractures from microfrac tests; inspection of natural and coring induced fractures in oriented cores; borehole monitoring of fracture-related microseismicity; and borehole televiewer examination. Similar results were obtained in all cases, with only small variations between wells. Reliability, cost effectiveness, and predictive ability are discussed.
Time dependent behaviour See also: 931348 931099 Influence of cycling pore-water pressures and principal stress ratios on drained deformations in clay. Note Eigenbrod, K D; Graham, J; Burak, J P Can Geotech d V29, N2, April 1992, P326-333 Seasonal changes in groundwater levels are known to affect the rate of downward creep of clay slopes. To investigate this effect, undisturbed clay specimens were anisotropically consolidated to in-slope conditions, then pore pressures systematically cycled over periods of 4-48hr. Axial and volume strains were measured, lateral and shear strains calculated. Strain rates decreased with total time of testing. For a given elapsed
© 1993 Pergamon Press Ltd. Reproduction not permitted RMMS 30/I--G