Study of hydraulic fracture growth behavior in heterogeneous tight sandstone formations using CT scanning and acoustic emission monitoring
|
摘要
Tortuous hydraulic fractures(HFs) are likely to be created in heterogeneous formations such as conglomerates, which may cause sand plugging, ultimately resulting in poor stimulation efficiency. This study aims to explore HF growth behavior in conglomerate through laboratory fracturing experiments under true tri-axial stresses combined with computed tomography scanning and acoustic emission(AE) monitoring. The effects of gravel size, horizontal differential stress, and AE focal mechanisms were examined. Especially, the injection pressure and the AE response features during HF initiation and propagation in conglomerate were analyzed. Simple HFs with narrow microfractures are created in conglomerate when the gravels are considerably smaller than the specimen, whereas complex fractures are created when the gravels are similar in size to the specimen, even under high horizontal differential stresses. Breakdown pressure and AE rates are high when a HF is initiated from the high-strength gravel. A large pressure decline after the breakdown may indicate the creation of a planar and wide HF. Analyzing the focal mechanism indicates that the shear mechanism generally dominates with an increase in the HF complexity. Tensile events are likely to occur during HF initiation and are located around the wellbore. Shear events occur mainly around the nonplanar and complex matrix/gravel interfaces.
Tortuous hydraulic fractures(HFs) are likely to be created in heterogeneous formations such as conglomerates, which may cause sand plugging, ultimately resulting in poor stimulation efficiency. This study aims to explore HF growth behavior in conglomerate through laboratory fracturing experiments under true tri-axial stresses combined with computed tomography scanning and acoustic emission(AE) monitoring. The effects of gravel size, horizontal differential stress, and AE focal mechanisms were examined. Especially, the injection pressure and the AE response features during HF initiation and propagation in conglomerate were analyzed. Simple HFs with narrow microfractures are created in conglomerate when the gravels are considerably smaller than the specimen, whereas complex fractures are created when the gravels are similar in size to the specimen, even under high horizontal differential stresses. Breakdown pressure and AE rates are high when a HF is initiated from the high-strength gravel. A large pressure decline after the breakdown may indicate the creation of a planar and wide HF. Analyzing the focal mechanism indicates that the shear mechanism generally dominates with an increase in the HF complexity. Tensile events are likely to occur during HF initiation and are located around the wellbore. Shear events occur mainly around the nonplanar and complex matrix/gravel interfaces.
Tortuous hydraulic fractures(HFs) are likely to be created in heterogeneous formations such as conglomerates, which may cause sand plugging, ultimately resulting in poor stimulation efficiency. This study aims to explore HF growth behavior in conglomerate through laboratory fracturing experiments under true tri-axial stresses combined with computed tomography scanning and acoustic emission(AE) monitoring. The effects of gravel size, horizontal differential stress, and AE focal mechanisms were examined. Especially, the injection pressure and the AE response features during HF initiation and propagation in conglomerate were analyzed. Simple HFs with narrow microfractures are created in conglomerate when the gravels are considerably smaller than the specimen, whereas complex fractures are created when the gravels are similar in size to the specimen, even under high horizontal differential stresses. Breakdown pressure and AE rates are high when a HF is initiated from the high-strength gravel. A large pressure decline after the breakdown may indicate the creation of a planar and wide HF. Analyzing the focal mechanism indicates that the shear mechanism generally dominates with an increase in the HF complexity. Tensile events are likely to occur during HF initiation and are located around the wellbore. Shear events occur mainly around the nonplanar and complex matrix/gravel interfaces.
引文
Bennour Z,Ishida T,Nagaya Y,Chen Y,Nara Y,Chen Q,et al. Crack extension in hydraulic fracturing of shale cores using viscous oil,water, and liquid carbon dioxide. Rock Mech Rock Eng.2015;48:1463-73. https://doi.org/10.1007/s00603-015-0774-2.
Frash L, Gutierrez M, Hampton J. Scale model simulation of hydraulic fracturing for EGS reservoir creation using a heated true-triaxial apparatus. In:ISRM international conference for effective and sustainable hydraulic fracturing. International Society for Rock Mechanics; 2013.
Hampton J, Frash L, Gutierrez M. Investigation of laboratory hydraulic fracture source mechanisms using acoustic emission.In:47th U.S. rock mechanics/geomechanics symposium. American Rock Mechanics Association; 2013.
Hu X, Wu K, Song X, Yu W, Tang J, Li G, et al. A new model for simulating particle transport in a low-viscosity fluid for fluiddriven fracturing. AIChE J. 2018a. https://doi.org/10.1002/aic.16183.
Hu X, Wu K, Li G, Tang J, Shen Z. Effect of proppant addition schedule on the proppant distribution in a straight fracture for slickwater treatment. J Pet Sci Eng. 2018b;167:110-9. https://doi.org/10.1016/j.petrol.2018.03.081.
Ju Y, Yang Y, Chen J, Liu P, Dai T, Guo Y, et al. 3D reconstruction of low-permeability heterogeneous glutenites and numerical simulation of hydraulic fracturing behavior. Chin Sci Bull.2016a;61:82-93.
Ju Y, Liu P, Chen JL, Yang YM, Ranjith PG. CDEM-based analysis of the 3D initiation and propagation of hydrofracturing cracks in heterogeneous glutenites. J Nat Gas Sci Eng. 2016b;35:614-23.https://doi.org/10.1016/j.jngse.2016.09.011.
Lei XL, Nishizawa O, Kusunose K, Satoh T. Fractal structure of the hypocenter distributions and focal mechanism solutions of acoustic emission in two granites of different grain sizes.J Phys Earth. 1992;40(6):617-34. https://doi.org/10.4294/jpe1952.40.617.
Lei XL, Kusunose K, Rao MVMS, Nishizawa O, Satoh T. Quasistatic fault growth and cracking in homogeneous brittle rock under triaxial compression using acoustic emission monitoring.J Geophys Res. 2001;105(B3):6127-39. https://doi.org/10.1029/1999JB900385.
Li LC, Li G, Meng QM, Wang H, Wang Z. Numerical simulation of propagation of hydraulic fractures in glutenite formation. Chin J Rock Soil Mech. 2013;34(5):1501-7.
Li N, Zhang SC, Zou YS, Ma XF, Wu S, Zhang YN. Experimental analysis of hydraulic fracture growth and acoustic emission response in a layered formation. Rock Mech Rock Eng.2018a;51(4):1047-62. https://doi.org/10.1007/s00603-017-1383-z.
Li N, Zhang SC, Zou YS, Ma XF, Zhang ZP, Li SH, et al. Accoustic emission response of laboratory hydraulic fracturing in layered shale. Rock Mech Rock Eng. 2018b; 51(11):3394-406. https://doi.org/10.1007/s00603-018-1547-5.
Lockner D, Byerlee JD. Hydrofracture in Weber sandstone at high confining pressure and differential stress. J Geophys Res Atmos.1977;82(14):2018-26. https://doi.org/10.1029/JB082i014p02018.
Ma XF, Zou YS, Li N, Chen M, Zhang YN, Liu ZZ. Experimental study on the mechanism of hydraulic fracture growth in a glutenite reservoir. J Struct Geol. 2017;97:37-47. https://doi.org/10.1016/j.jsg.2017.02.012.
Matsunaga I, Kobayashi H, Sasaki S, Ishida T. Studying hydraulic fracturing mechanism by laboratory experiments with acoustic emission monitoring. Intern J Rock Mech Min Sci Geomech Abstr. 1993;30(7):909-12. https://doi.org/10.1016/0148-9062(93)90043-D.
Meng QM, Zhang SC, Guo XM, Chen XH, Zhang Y. A primary investigation on propagation mechanism for hydraulic fractures in glutenite formation. J Oil Gas Technol. 2010;32(4):119-23.
Mogi K. Earthquakes and fractures. Tectonophysics. 1967;5(1):35-55.https://doi.org/10.1016/0040-1951(67)90043-1.
Molenda M, Stockhert F, Brenne S, Alber M. Acoustic emission monitoring of laboratory scale hydraulic fracturing experiments.In:49th US rock mechanics/geomechanics symposium. American Rock Mechanics Association; 2015.
Stanchits S, Vinciguerra S, Dresen G. Ultrasonic velocities, acoustic emission characteristics and crack damage of basalt and granite.Pure appl Geophys. 2006; 163(5):975-94. https://doi.org/10.1007/s00024-006-0059-5.
Stanchits S, Surdi A, Edelman E, Suarez-Rivera R. Acoustic emission and ultrasonic transmission monitoring of hydraulic fracture propagation in heterogeneous rock samples. In:46th US rock mechanics/geomechanics symposium. American Rock Mechanics Association; 2012.
Stanchits S, Burghardt J, Surdi A. Hydraulic fracturing of heterogeneous rock monitored by acoustic emission. Rock Mech Rock Eng. 2015;48(6):2513-27. https://doi.org/10.1007/s00603-015-0848-1.
Talebi S, Cornet FH. Analysis of microseismicity induced by a fluid injection in a granite rock mass. Geophys Res Lett.1987;14:227-30. https://doi.org/10.1029/GL014i003p00227.
Tang J, Wu K, Zeng B, Huang H, Hu X, Guo X, et al. Investigate effects of weak bedding interfaces on fracture geometry in unconventional reservoirs. J Petrol Sci Eng. 2018a; 165:992-1009. https://doi.org/10.1016/j.petrol.2017.11.037.
Tang J, Wu K, Li Y, Hu X, Liu Q, Ehlig-Economides C. Numerical investigation of the Interactions between hydraulic fracture and bedding planes with non-orthogonal approach angle. Eng Frac Mech. 2018b;200:1-16. https://doi.org/10.1016/j.engfracmech.2018.07.010.
Yashwanth C, Camilo M, Carl S, Chandra R. An experimental investigation into hydraulic fracture propagation under different applied stresses in tight sands using acoustic emissions. J Pet Sci Eng. 2013;108:151-61. https://doi.org/10.1016/j.petrol.2013.01.002.
Zoback MD, Rummel F, Jung R, Raleigh CB. Laboratory hydraulic fracturing experiments in intact and pre-fractured rock. Int J Rock Mech Min Sci Geophys Abstr. 1977;14(2):49-58. https://doi.org/10.1016/0148-9062(77)90196-6.
Zou YS,Zhang SC, Zhou T, Zhou X,Guo TK. Experimental investigation into hydraulic fracture network propagation in gas shales using CT scanning technology. Rock Mech Rock Eng.2016;49:33-45. https://doi.org/10.1007/s00603-015-0720-3.
Zou YS, Ma XF, Zhou T, Li N, Chen M, Li SH, et al. Hydraulic fracture growth in a layered formation based on fracturing experiments and discrete element modeling. Rock Mech Rock Eng.2017;50:2381-95. https://doi.org/10.1007/s00603-017-1241-z.
Frash L, Gutierrez M, Hampton J. Scale model simulation of hydraulic fracturing for EGS reservoir creation using a heated true-triaxial apparatus. In:ISRM international conference for effective and sustainable hydraulic fracturing. International Society for Rock Mechanics; 2013.
Hampton J, Frash L, Gutierrez M. Investigation of laboratory hydraulic fracture source mechanisms using acoustic emission.In:47th U.S. rock mechanics/geomechanics symposium. American Rock Mechanics Association; 2013.
Hu X, Wu K, Song X, Yu W, Tang J, Li G, et al. A new model for simulating particle transport in a low-viscosity fluid for fluiddriven fracturing. AIChE J. 2018a. https://doi.org/10.1002/aic.16183.
Hu X, Wu K, Li G, Tang J, Shen Z. Effect of proppant addition schedule on the proppant distribution in a straight fracture for slickwater treatment. J Pet Sci Eng. 2018b;167:110-9. https://doi.org/10.1016/j.petrol.2018.03.081.
Ju Y, Yang Y, Chen J, Liu P, Dai T, Guo Y, et al. 3D reconstruction of low-permeability heterogeneous glutenites and numerical simulation of hydraulic fracturing behavior. Chin Sci Bull.2016a;61:82-93.
Ju Y, Liu P, Chen JL, Yang YM, Ranjith PG. CDEM-based analysis of the 3D initiation and propagation of hydrofracturing cracks in heterogeneous glutenites. J Nat Gas Sci Eng. 2016b;35:614-23.https://doi.org/10.1016/j.jngse.2016.09.011.
Lei XL, Nishizawa O, Kusunose K, Satoh T. Fractal structure of the hypocenter distributions and focal mechanism solutions of acoustic emission in two granites of different grain sizes.J Phys Earth. 1992;40(6):617-34. https://doi.org/10.4294/jpe1952.40.617.
Lei XL, Kusunose K, Rao MVMS, Nishizawa O, Satoh T. Quasistatic fault growth and cracking in homogeneous brittle rock under triaxial compression using acoustic emission monitoring.J Geophys Res. 2001;105(B3):6127-39. https://doi.org/10.1029/1999JB900385.
Li LC, Li G, Meng QM, Wang H, Wang Z. Numerical simulation of propagation of hydraulic fractures in glutenite formation. Chin J Rock Soil Mech. 2013;34(5):1501-7.
Li N, Zhang SC, Zou YS, Ma XF, Wu S, Zhang YN. Experimental analysis of hydraulic fracture growth and acoustic emission response in a layered formation. Rock Mech Rock Eng.2018a;51(4):1047-62. https://doi.org/10.1007/s00603-017-1383-z.
Li N, Zhang SC, Zou YS, Ma XF, Zhang ZP, Li SH, et al. Accoustic emission response of laboratory hydraulic fracturing in layered shale. Rock Mech Rock Eng. 2018b; 51(11):3394-406. https://doi.org/10.1007/s00603-018-1547-5.
Lockner D, Byerlee JD. Hydrofracture in Weber sandstone at high confining pressure and differential stress. J Geophys Res Atmos.1977;82(14):2018-26. https://doi.org/10.1029/JB082i014p02018.
Ma XF, Zou YS, Li N, Chen M, Zhang YN, Liu ZZ. Experimental study on the mechanism of hydraulic fracture growth in a glutenite reservoir. J Struct Geol. 2017;97:37-47. https://doi.org/10.1016/j.jsg.2017.02.012.
Matsunaga I, Kobayashi H, Sasaki S, Ishida T. Studying hydraulic fracturing mechanism by laboratory experiments with acoustic emission monitoring. Intern J Rock Mech Min Sci Geomech Abstr. 1993;30(7):909-12. https://doi.org/10.1016/0148-9062(93)90043-D.
Meng QM, Zhang SC, Guo XM, Chen XH, Zhang Y. A primary investigation on propagation mechanism for hydraulic fractures in glutenite formation. J Oil Gas Technol. 2010;32(4):119-23.
Mogi K. Earthquakes and fractures. Tectonophysics. 1967;5(1):35-55.https://doi.org/10.1016/0040-1951(67)90043-1.
Molenda M, Stockhert F, Brenne S, Alber M. Acoustic emission monitoring of laboratory scale hydraulic fracturing experiments.In:49th US rock mechanics/geomechanics symposium. American Rock Mechanics Association; 2015.
Stanchits S, Vinciguerra S, Dresen G. Ultrasonic velocities, acoustic emission characteristics and crack damage of basalt and granite.Pure appl Geophys. 2006; 163(5):975-94. https://doi.org/10.1007/s00024-006-0059-5.
Stanchits S, Surdi A, Edelman E, Suarez-Rivera R. Acoustic emission and ultrasonic transmission monitoring of hydraulic fracture propagation in heterogeneous rock samples. In:46th US rock mechanics/geomechanics symposium. American Rock Mechanics Association; 2012.
Stanchits S, Burghardt J, Surdi A. Hydraulic fracturing of heterogeneous rock monitored by acoustic emission. Rock Mech Rock Eng. 2015;48(6):2513-27. https://doi.org/10.1007/s00603-015-0848-1.
Talebi S, Cornet FH. Analysis of microseismicity induced by a fluid injection in a granite rock mass. Geophys Res Lett.1987;14:227-30. https://doi.org/10.1029/GL014i003p00227.
Tang J, Wu K, Zeng B, Huang H, Hu X, Guo X, et al. Investigate effects of weak bedding interfaces on fracture geometry in unconventional reservoirs. J Petrol Sci Eng. 2018a; 165:992-1009. https://doi.org/10.1016/j.petrol.2017.11.037.
Tang J, Wu K, Li Y, Hu X, Liu Q, Ehlig-Economides C. Numerical investigation of the Interactions between hydraulic fracture and bedding planes with non-orthogonal approach angle. Eng Frac Mech. 2018b;200:1-16. https://doi.org/10.1016/j.engfracmech.2018.07.010.
Yashwanth C, Camilo M, Carl S, Chandra R. An experimental investigation into hydraulic fracture propagation under different applied stresses in tight sands using acoustic emissions. J Pet Sci Eng. 2013;108:151-61. https://doi.org/10.1016/j.petrol.2013.01.002.
Zoback MD, Rummel F, Jung R, Raleigh CB. Laboratory hydraulic fracturing experiments in intact and pre-fractured rock. Int J Rock Mech Min Sci Geophys Abstr. 1977;14(2):49-58. https://doi.org/10.1016/0148-9062(77)90196-6.
Zou YS,Zhang SC, Zhou T, Zhou X,Guo TK. Experimental investigation into hydraulic fracture network propagation in gas shales using CT scanning technology. Rock Mech Rock Eng.2016;49:33-45. https://doi.org/10.1007/s00603-015-0720-3.
Zou YS, Ma XF, Zhou T, Li N, Chen M, Li SH, et al. Hydraulic fracture growth in a layered formation based on fracturing experiments and discrete element modeling. Rock Mech Rock Eng.2017;50:2381-95. https://doi.org/10.1007/s00603-017-1241-z.