页岩结构面特征及其对水力压裂的控制作用
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摘要
页岩是沉积岩中的一种,具有十分明显的层理构造。探究页岩层理结构面对其水力压裂行为的影响,对页岩气的开采具有重要意义。通过对鄂尔多斯盆地南部延长组页岩不同尺度下(米级到十微米级)沉积结构特点的分析,结合不同层理倾角条件下的大尺寸页岩试样水力压裂试验,研究了页岩结构面(层理面)的特征及其对水力压裂过程和结果的控制作用。结果表明,米级、分米级、厘米级、毫米级和10微米级等不同研究尺度下的纹层平均厚度分别为2. 26 m,2. 09 dm,1. 70 cm,1. 48 mm和11. 7μm,呈现出分形特征,且分形维数为1. 06。页岩水力压裂行为受层理结构面影响显著,主要体现在压裂前后裂缝形态对比与破裂压力两个方面。层理倾角小于30°时,页岩试样压裂前后裂缝形态对比明显,新生裂缝较多,破裂压力较大,且随着层理倾角的增大急剧减小;大于45°时,压裂前后试样的裂缝形态几乎没有改变,破裂压力较小,且随着层理倾角的增大呈现小幅度的波动;整体上不同层理面角度下页岩的破裂压力呈斜"S"型变化。试验中的裂缝扩展,水压曲线以及破裂压力随层理倾角的不同均发生变化。
Shale,a kind of sedimentary rocks,is characterized by significant bedding. The investigation of the impact of bedding planes of shale on hydraulic fracturing is of great significance for the exploitation of shale gas. The characteristics of sedimentary structures at various scales( ranging from meter to ten micron scales) of shale in the Yanchang Formation in southern Ordos Basin were analyzed,and the hydraulic fracturing tests for multi-sized shale specimens under different dip angles of bedding plane were carried out,both of which function to explain the characteristics of the bedding planes of shale and their controlling effects on hydraulic fracturing process and outcome. The results show that the average thickness of laminae is of fractal features with a fractal dimension of 1. 06,and is 2. 26 m,2. 09 dm,1. 70 cm,1. 48 mm and 11. 7μm,corresponding to meter,decimeter,centimeter,millimeter and 10-micron scales respectively. The behaviors of hydraulic fracturing are significantly influenced by the bedding planes of shale,clearly shown by the contrast of fracture geometry before and after fracturing and the fracturing pressure. When the dip angles of the bedding planes are less than 30°,the fractured shale specimen is remarkably different from its original one in fracture geometry,featuring much more artificial fractures,and higher fracturing pressure,which tends to slump as the dip angle of bedding plane increases; while when the dip angles of the shale specimens are above 45°,the fracture geometry of the shale specimens after fracturing is almost the same with that of the original specimens,featuring lower fracturing pressure which tends to fluctuate a little with the increase of the dip angle of the bedding planes. Generally,the fracturing pressures of shale under different dip angles of bedding plane fluctuates in the shape of oblique "S". Besides,the controlling effects of structural dip angles of the bedding planes on the fracture propagation,hydraulic pressure curve and fracturing pressure are also reflected in the tests.
Shale,a kind of sedimentary rocks,is characterized by significant bedding. The investigation of the impact of bedding planes of shale on hydraulic fracturing is of great significance for the exploitation of shale gas. The characteristics of sedimentary structures at various scales( ranging from meter to ten micron scales) of shale in the Yanchang Formation in southern Ordos Basin were analyzed,and the hydraulic fracturing tests for multi-sized shale specimens under different dip angles of bedding plane were carried out,both of which function to explain the characteristics of the bedding planes of shale and their controlling effects on hydraulic fracturing process and outcome. The results show that the average thickness of laminae is of fractal features with a fractal dimension of 1. 06,and is 2. 26 m,2. 09 dm,1. 70 cm,1. 48 mm and 11. 7μm,corresponding to meter,decimeter,centimeter,millimeter and 10-micron scales respectively. The behaviors of hydraulic fracturing are significantly influenced by the bedding planes of shale,clearly shown by the contrast of fracture geometry before and after fracturing and the fracturing pressure. When the dip angles of the bedding planes are less than 30°,the fractured shale specimen is remarkably different from its original one in fracture geometry,featuring much more artificial fractures,and higher fracturing pressure,which tends to slump as the dip angle of bedding plane increases; while when the dip angles of the shale specimens are above 45°,the fracture geometry of the shale specimens after fracturing is almost the same with that of the original specimens,featuring lower fracturing pressure which tends to fluctuate a little with the increase of the dip angle of the bedding planes. Generally,the fracturing pressures of shale under different dip angles of bedding plane fluctuates in the shape of oblique "S". Besides,the controlling effects of structural dip angles of the bedding planes on the fracture propagation,hydraulic pressure curve and fracturing pressure are also reflected in the tests.
引文
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[15]邹才能,张国生,杨智,等.非常规油气概念、特征、潜力及技术:兼论非常规油气地质学[J].石油勘探与开发,2013,40(4):385-399,454.Zou Caineng,Zhang Guosheng,Yang Zhi,et al. Geological concepts,characteristics,resource potential and key techniques of unconventional hydrocarbon:On unconventional petroleum geology[J]. Petroleum Exploration and Development,2013,40(4):385-399,454.
[16] Singh H,Javadpour F. Langmuir slip-Langmuir sorption permeability model of shale[J]. Fuel,2016,164:28-37.
[17]汪虎,何治亮,张永贵,等.四川盆地海相页岩储层微裂缝类型及其对储层物性影响[J].石油与天然气地质,2019,40(1):41-49.Wang Hu,He Zhiliang,Zhang Yonggui,et al. Microfracture types of marine shale reservoir of Sichuan Basin and its influence on reservoir property[J]. Oil&Gas Geology,2019,40(1):41-49.
[18] Hsu S C,Nelson P P. Characterization of eagle ford Shale[J]. Engineering Geology,2002,67(1):169-183.
[19] Miskimins J L,Barree R D. Modeling of hydraulic fracture height containment in laminated sand and shale sequences[C]∥SPE Production and Operations Symposium. Oklahoma:Society of Petroleum Engineers,2003.
[20]赵海军,马凤山,刘港,等.不同尺度岩体结构面对页岩气储层水力压裂裂缝扩展的影响[J].工程地质学报,2016,24(5):992-1007.Zhao Haijun,Ma Fengshan,Liu Gang,et al. Influence of different scales of structural planes on propagation mechanism of hydraulic fracturing[J]. Journal of Engineering Geology,2016,24(5):992-1007.
[21] Mendoza-Torres F,Díaz-Viera M A,Erdely A. Bernstein copula modeling for 2D discrete fracture network simulations[J]. Journal of Petroleum Science&Engineering,2017,156:710-720.
[22] Gong J,Rossen W R. Shape factor for dual-permeability fractured reservoir simulation:effect of non-uniform flow in 2D fracture network[J]. Fuel,2016,184:81-88.
[23] Nejadi S,Trivedi J J,Leung J. History matching and uncertainty quant ification of discrete fracture network models in fractured reservoirs[J]. Journal of Petroleum Science&Engineering,2017,152:21-32.
[24]陈尚斌,朱炎铭,王红岩,等.四川盆地南缘下志留统龙马溪组页岩气储层矿物成分特征及意义[J].石油学报,2011,32(5):775-782.Chen Shangbin,Zhu Yanming,Wang Hongyan,et al. Characteristics and significance of mineral compositions of Lower Silurian Longmaxi Formation shale gas reservoir in the southern margin of Sichuan Basin[J]. Acta Petrolei Sinica,2011,32(5):775-782.
[25] Renard F,Bernard D,Desrues J,et al. 3D imaging of fracture propagation using synchrotron X-ray microtomography[J]. Earth&Planetary Science Letters,2009,286(1):285-291.
[26] Min K S,Zhang Z N,Ghassemi A. Hydraulic fracture propagation in heterogeneous rock using the VMIB method[C]∥Proceedings,Thirty-Fifth Workshop on Geothermal Reservoir Engineering. Stanford,California:Stanford University,2010.
[2] Li L,Huang B,Li Y. Multi-scale modeling of shale laminas and fracture networks in the Yanchang Formation,Southern Ordos Basin,China[J]. Engineering Geology,2018,243:231-240.
[3] Li L,Huang B,Tan Y. Geometric heterogeneity of continental shale in theYanchang Formation,Southern Ordos Basin,China[J]. Scientific Reports,2017,7(1):6006.
[4] Hammes U,Hamlin H S. Geologic analysis of the Upper Jurassic haynesville shale in east Texas and west Louisiana[J]. AAPG Bulletin,2011,95(10):1643-1666.
[5] Slatt R M,Abousleiman Y. Merging sequence stratigraphy and geomechanics for unconventional gas shales[J]. Leading Edge,2011,30(3):274-282.
[6] Slatt R M,O’Brien N R. Pore types in the Barnett and Woodford gas shales:contribution to understanding gas storage and migration pathways in fine-grained rocks[J]. AAPG Bulletin,2011,95(12):2017-2030.
[7] Brittenham M D. Geologic analysis of the upper Jurassic Haynesville shale in East Texas and West Louisiana:discussion[J]. AAPG Bulletin,2013,97(3):525-528.
[8]师良,王香增,范柏江,等.鄂尔多斯盆地延长组砂质纹层发育特征与油气成藏[J].石油与天然气地质,2018,39(3):522-530.Shi Liang,Wang Xiangzeng,Fan Bojiang,et al. Characteristics of sandy lamination and its hydrocarbon accumulation,Yanchang Formation,Ordos Basin[J]. Oil&Gas Geology,2018,39(3):522-530.
[9] Mitchell J K,Soga K. Fundamentals of soil behavior[M]. New York:Wiley,2005:369.
[10] Favero V,Ferrari A,Laloui L. On the hydro-mechanical behaviour of remoulded and natural Opalinus clay shale[J]. Engineering Geology,2016,208:128-135.
[11] Mousavi N M,Fisher Q J. Experimental study and numerical modeling of fracture propagation in shale rocks during Brazilian disk test[J].Rock Mechanics and Rock Engineering,2018,51(6):1755-1775.
[12] Jaeger J C. Shear failure of anistropic rocks[J]. Geological Magazine,1960,97(1):65-72.
[13]涂乙,邹海燕,孟海平,等.页岩气评价标准与储层分类[J].石油与天然气地质,2014,35(1):153-158.Tu Yi,Zou Haiyan,Meng Haiping,et al. Evaluation criteria and classification of shale gas reservoirs[J]. Oil&Gas Geology,2014,35(1):153-158.
[14]贾承造,郑民,张永峰.中国非常规油气资源与勘探开发前景[J].石油勘探与开发,2012,39(2):129-136.Jia Chengzao,Zheng Min,Zhang Yongfeng. Unconventional hydrocarbon resources in China and the prospect of exploration and development[J]. Petroleum Exploration and Development,2012,39(2):129-136.
[15]邹才能,张国生,杨智,等.非常规油气概念、特征、潜力及技术:兼论非常规油气地质学[J].石油勘探与开发,2013,40(4):385-399,454.Zou Caineng,Zhang Guosheng,Yang Zhi,et al. Geological concepts,characteristics,resource potential and key techniques of unconventional hydrocarbon:On unconventional petroleum geology[J]. Petroleum Exploration and Development,2013,40(4):385-399,454.
[16] Singh H,Javadpour F. Langmuir slip-Langmuir sorption permeability model of shale[J]. Fuel,2016,164:28-37.
[17]汪虎,何治亮,张永贵,等.四川盆地海相页岩储层微裂缝类型及其对储层物性影响[J].石油与天然气地质,2019,40(1):41-49.Wang Hu,He Zhiliang,Zhang Yonggui,et al. Microfracture types of marine shale reservoir of Sichuan Basin and its influence on reservoir property[J]. Oil&Gas Geology,2019,40(1):41-49.
[18] Hsu S C,Nelson P P. Characterization of eagle ford Shale[J]. Engineering Geology,2002,67(1):169-183.
[19] Miskimins J L,Barree R D. Modeling of hydraulic fracture height containment in laminated sand and shale sequences[C]∥SPE Production and Operations Symposium. Oklahoma:Society of Petroleum Engineers,2003.
[20]赵海军,马凤山,刘港,等.不同尺度岩体结构面对页岩气储层水力压裂裂缝扩展的影响[J].工程地质学报,2016,24(5):992-1007.Zhao Haijun,Ma Fengshan,Liu Gang,et al. Influence of different scales of structural planes on propagation mechanism of hydraulic fracturing[J]. Journal of Engineering Geology,2016,24(5):992-1007.
[21] Mendoza-Torres F,Díaz-Viera M A,Erdely A. Bernstein copula modeling for 2D discrete fracture network simulations[J]. Journal of Petroleum Science&Engineering,2017,156:710-720.
[22] Gong J,Rossen W R. Shape factor for dual-permeability fractured reservoir simulation:effect of non-uniform flow in 2D fracture network[J]. Fuel,2016,184:81-88.
[23] Nejadi S,Trivedi J J,Leung J. History matching and uncertainty quant ification of discrete fracture network models in fractured reservoirs[J]. Journal of Petroleum Science&Engineering,2017,152:21-32.
[24]陈尚斌,朱炎铭,王红岩,等.四川盆地南缘下志留统龙马溪组页岩气储层矿物成分特征及意义[J].石油学报,2011,32(5):775-782.Chen Shangbin,Zhu Yanming,Wang Hongyan,et al. Characteristics and significance of mineral compositions of Lower Silurian Longmaxi Formation shale gas reservoir in the southern margin of Sichuan Basin[J]. Acta Petrolei Sinica,2011,32(5):775-782.
[25] Renard F,Bernard D,Desrues J,et al. 3D imaging of fracture propagation using synchrotron X-ray microtomography[J]. Earth&Planetary Science Letters,2009,286(1):285-291.
[26] Min K S,Zhang Z N,Ghassemi A. Hydraulic fracture propagation in heterogeneous rock using the VMIB method[C]∥Proceedings,Thirty-Fifth Workshop on Geothermal Reservoir Engineering. Stanford,California:Stanford University,2010.