一种基于应力-应变特征的岩石脆性指数评价改进方法
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摘要
脆性指数作为岩石力学评价的重要指标之一,对准确评价岩石脆性特征具有重要意义。选取四川盆地新场气田须家河组五段的21块岩石样品,对其开展室内三轴岩石力学实验,分别模拟了样品在围压0 MPa,12 MPa,22 MPa,32 MPa下的三轴饱水力学和声学测试,基于岩石应力-应变曲线分析不同岩石脆性特征参数的差异,分别计算基于杨氏模量的脆性因子(B_(Ym))、基于泊松比的脆性因子(B_μ)、基于可恢复应变与总应变的脆性因子(B_(Rε))、基于屈服强度与抗压强度的脆性因子(B_(Rσ)),并对比、分析了现有的基于应力-应变曲线的脆性评价方法,进而综合室内岩石力学测试结果建立了脆性指数B_n与B_(Ym),B_μ,B_(Rε),B_(Rσ)的函数关系式,通过多元回归方法建立新的脆性指数模型,对岩石样品的脆性进行评价。结果表明:传统的脆性指数评价方法在区分岩石样品脆性时效果不佳;改进后的模型能够更好地区分研究区高脆性泥岩、低脆性泥岩和砂岩。该研究结果对于准确评价岩石脆性特征具有指导意义。
As one of the important indexes for rock mechanics evaluation,the evaluation of brittleness index is of great significance to rock characteristics. 21 rock samples of the fifth member of Xujiahe Formation of Xinchang Gas Field in Sichuan Basin were selected to carry out laboratory triaxial rock mechanics experiments. Triaxial saturation hydraulics and acoustic tests of samples under confining pressure of 0 MPa,12 MPa,22 MPa and 32 MPa were simulated respectively. Based on the stress-strain curve characteristics,the differences of different brittle-ness characteristic parameters were analyzed. The brittleness factors such as B_(Ym),B_μ,B_(Rε)and B_(Rσ)respectively based on Young's modulus,Poisson's ratio,recoverable strain and total strain,and yield strength and compressive strength,were calculated. The existing brittleness evaluation methods based on stress-strain curves were compared and analyzed,and the functional relationships of brittleness index B_nwith B_(Ym),B_μ,B_(Rε)and B_(Rσ)were established according to the laboratory rock mechanics test results. A new brittleness index model was established by multiple regression method to evaluate the brittleness of rock samples. The results show that the conventional brittleness index evaluation method is not effective in distinguishing brittleness of rock samples,and the improved model can better distinguish high brittle mudstone,low brittle mudstone and sandstone in the study area. The study results have guiding significance for accurately evaluating the brittleness characteristics of rocks.
As one of the important indexes for rock mechanics evaluation,the evaluation of brittleness index is of great significance to rock characteristics. 21 rock samples of the fifth member of Xujiahe Formation of Xinchang Gas Field in Sichuan Basin were selected to carry out laboratory triaxial rock mechanics experiments. Triaxial saturation hydraulics and acoustic tests of samples under confining pressure of 0 MPa,12 MPa,22 MPa and 32 MPa were simulated respectively. Based on the stress-strain curve characteristics,the differences of different brittle-ness characteristic parameters were analyzed. The brittleness factors such as B_(Ym),B_μ,B_(Rε)and B_(Rσ)respectively based on Young's modulus,Poisson's ratio,recoverable strain and total strain,and yield strength and compressive strength,were calculated. The existing brittleness evaluation methods based on stress-strain curves were compared and analyzed,and the functional relationships of brittleness index B_nwith B_(Ym),B_μ,B_(Rε)and B_(Rσ)were established according to the laboratory rock mechanics test results. A new brittleness index model was established by multiple regression method to evaluate the brittleness of rock samples. The results show that the conventional brittleness index evaluation method is not effective in distinguishing brittleness of rock samples,and the improved model can better distinguish high brittle mudstone,low brittle mudstone and sandstone in the study area. The study results have guiding significance for accurately evaluating the brittleness characteristics of rocks.
引文
[1]李庆辉,陈勉,金衍,等.页岩气储层岩石力学特性及脆性评价.石油钻探技术,2012,40(4):17-22.LI Q H,CHEN M,JIN Y,et al. Rock mechanical properties and brittleness evaluation of shale gas reservoir. Petroleum Drilling Techniques,2012,40(4):17-22.
[2] ALTINDAG R. The evaluation of rock brittleness concept on rotary blast hole drills. The South African Institute of Mining and Metallurgy,1980,17(5):1048-1055.
[3]廖东良,肖立志,张元春.基于矿物组分与断裂韧度的页岩地层脆性指数评价模型.石油钻探技术,2014,42(4):37-41.LIAO D L,XIAO L Z,ZHANG Y C. Evaluation model for shale brittleness index based on mineral content and fracture toughness. Petroleum Drilling Techniques,2014,42(4):37-41.
[4]王跃鹏,刘向君,梁利喜.页岩力学特性的层理效应及脆性预测.岩性油气藏,2018,30(4):149-160.WANG Y P,LIU X J,LIANG L X. Influences of bedding planes on mechanical properties and prediction method of brittleness index in shale. Lithologic Reservoirs,2018,30(4):149-160.
[5]王鹏,纪友亮,潘仁芳,等.页岩脆性的综合评价方法:以四川盆地W区下志留统龙马溪组为例.天然气工业,2013,33(12):48-53.WANG P,JI Y L,PAN R F,et al. A comprehensive evaluation methodology of shale brittleness:a case study from lower Silurian Longmaxi in block W,Sichuan Basin. Natural Gas Industry,2013,33(12):48-53.
[6]李庆辉,陈勉,金衍,等.页岩脆性的室内评价方法及改进.岩石力学与工程学报,2012,31(8):1680-1685.LI Q H,CHEN M,JIN Y,et al. Indoor evaluation method for shale brittleness and improvement. Chinese Journal of Rock Mechanics and Engineering,2012,31(8):1680-1685.
[7]张杰,张超馍,张占松,等.基于应力-应变曲线形态的致密气储层脆性研究.岩性油气藏,2017,29(3):126-131.ZHANG J,ZHANG C M,ZHANG Z S,et al. Brittleness of tight gas reservoirs based on stress-strain curves. Lithologic Reservoirs,2017,29(3):126-131.
[8]翟文宝,李军,周英操,等.基于测井资料的页岩储层可压裂性评价新方法.岩性油气藏,2018,30(3):112-123.ZHAI W B,LI J,ZHOU Y C,et al. New evaluation method of shale reservoir fracability based on logging data. Lithologic Reservoirs,2018,30(3):112-123.
[9]张昊天,周文,曹茜,等.基于应力-应变模型的脆塑性测井评价.测井技术,2018,42(3):331-337.ZHANG H T,ZHOU W,CAO Q,et al. Log evaluation method of the brittle-plastic parameters based on stress-strain model.Well Logging Technology,2018,42(3):331-337.
[10] JARVIE D M,HILL R J,RUBLE T E,et al. Unconventional shale-gas systems:The Mississippian Barnett Shale of northcentral Texas as one model for thermogenic shale-gas assessment. AAPG Bulletin,2007,91(4):475-499.
[11] BOWKER K A. Recent development of the Barnett shale play,Fort Worth Basin. Search&Discovery,2003,6(2):12-20.
[12]边会媛,王飞,张永浩,等.储层条件下致密砂岩动静态弹性力学参数实验研究.岩石力学与工程学报,2015,34(增刊1):3045-3054.BIAN H Y,WANG F,ZHANG Y H,et al. Experimental study of dynamic and static elastic parameters of tight sandstones under reservoir conditions. Chinese Journal of Rock Mechanics and Engineering,2015,34(Suppl 1):3045-3054.
[13]张晨晨,王玉满,董大忠,等.四川盆地五峰组—龙马溪组页岩脆性评价与“甜点层”预测.天然气工业,2016,36(9):51-ZHANG C C,WANG Y M,DONG D Z,et al. Evaluation of the Wufeng-Longmaxi shale brittleness and prediction of“sweet spot layers”in the Sichuan Basin. Natural Gas Industry,2016,36(9):51-60.
[14] CAO Q,ZHOU W,DENG H C,et al. Classification and controlling factors of organic pores in continental shale gas reservoirs based on laboratory experimental results. Journal of Natural Gas Science and Engineering,2015,27:1381-1388.
[15] ZHANG S L,YAN J P,HU Q H,et al. Integrated NMR and FESEM methods for pore structure characterization of Shahejie shale from the Dongying Depression,Bohai Bay Basin. Marine and Petroleum Geology,2019,100:85-94.
[16]闫建平,崔志鹏,耿斌,等.四川盆地龙马溪组与大安寨段泥页岩差异性分析.岩性油气藏,2016,28(4):16-23.YAN J P,CUI Z P,GENG B,et al. Differences of shale between Longmaxi Formation and Da'anzhai member in Sichuan Basin. Lithologic Reservoirs,2016,28(4):16-23.
[17]闫建平,言语,司马立强,等.泥页岩储层裂缝特征及其与“五性”之间的关系.岩性油气藏,2015,27(3):87-93.YAN J P,YAN Y,SIMA L Q,et al. Relationship between fracture characteristics and“five-property”of shale reservoir. Lithologic Reservoirs,2015,27(3):87-93.
[18]杨宝刚,潘仁芳,赵丹,等.四川盆地长宁示范区龙马溪组页岩岩石力学特性及脆性评价.地质科技情报,2015,34(4):183-188.YANG B G,PAN R F,ZHAO D,et al. Mechanical properties and brittleness evaluation of Longmaxi shale rock of Changning demonstration area in Sichuan Basin. Geological Science and Technology Information,2015,34(4):183-188.
[19]姚军,孙海,黄朝琴,等.页岩气藏开发中的关键力学问题.中国科学:物理学力学天文学,2013,43(12):1527-1547.YAO J,SUN H,HUANG Z Q,et al. Key mechanical problems in the development of shale gas reservoirs. Scientia Sinica Physica,Mechanica&Astronomica,2013,43(12):1527-1547.
[20]王绳祖.岩石的脆性-延性转变及塑性流动网络.地球物理学进展,1993,8(4):25-37.WANG S Z. Brittle-ductile transition and plastic-flow networks rocks. Progress in Geophysics,1993,8(4):25-37.
[21]张小龙,张同伟,李艳芳,等.页岩气勘探和开发进展综述.岩性油气藏,2013,25(2):116-122.ZHANG X L,ZHANG T W,LI Y F,et al. Research advance in exploration and development of shale gas. Lithologic Reservoirs,2013,25(2):116-122.
[22]赵万春,马云朋,王婷婷,等.不同脆性岩石的声发射特征.岩性油气藏,2017,29(4):124-130.ZHAO W C,MA Y P,WANG T T,et al. Acoustic emission characteristics of rocks with different brittleness. Lithologic Reservoirs,2017,29(4):124-130.
[23] HUCKA V,DAS B. Brittleness determination of rocks by different methods. International Journal of Rock Mechanics and Mining Sciences&Geomechanics Abstracts,1974,11(10):389-392.
[24] HAJIABDOLMAJID V,KAISER P. Brittleness of rock and stability assessment in hard rock tunneling. Tunneling and Underground Space Technology,2003,18(1):35-48.
[25] BISHOPA W,GREENG E,GARGAV K,et al. A new ring shear apparatus and its application to the measurement of residual strength. Geotechnique,1971,21(4):273-328.
[26] GRIESER W V,BRAY J M. Identification of production potential in unconventional reservoirs. SPE 106623,2007.
[2] ALTINDAG R. The evaluation of rock brittleness concept on rotary blast hole drills. The South African Institute of Mining and Metallurgy,1980,17(5):1048-1055.
[3]廖东良,肖立志,张元春.基于矿物组分与断裂韧度的页岩地层脆性指数评价模型.石油钻探技术,2014,42(4):37-41.LIAO D L,XIAO L Z,ZHANG Y C. Evaluation model for shale brittleness index based on mineral content and fracture toughness. Petroleum Drilling Techniques,2014,42(4):37-41.
[4]王跃鹏,刘向君,梁利喜.页岩力学特性的层理效应及脆性预测.岩性油气藏,2018,30(4):149-160.WANG Y P,LIU X J,LIANG L X. Influences of bedding planes on mechanical properties and prediction method of brittleness index in shale. Lithologic Reservoirs,2018,30(4):149-160.
[5]王鹏,纪友亮,潘仁芳,等.页岩脆性的综合评价方法:以四川盆地W区下志留统龙马溪组为例.天然气工业,2013,33(12):48-53.WANG P,JI Y L,PAN R F,et al. A comprehensive evaluation methodology of shale brittleness:a case study from lower Silurian Longmaxi in block W,Sichuan Basin. Natural Gas Industry,2013,33(12):48-53.
[6]李庆辉,陈勉,金衍,等.页岩脆性的室内评价方法及改进.岩石力学与工程学报,2012,31(8):1680-1685.LI Q H,CHEN M,JIN Y,et al. Indoor evaluation method for shale brittleness and improvement. Chinese Journal of Rock Mechanics and Engineering,2012,31(8):1680-1685.
[7]张杰,张超馍,张占松,等.基于应力-应变曲线形态的致密气储层脆性研究.岩性油气藏,2017,29(3):126-131.ZHANG J,ZHANG C M,ZHANG Z S,et al. Brittleness of tight gas reservoirs based on stress-strain curves. Lithologic Reservoirs,2017,29(3):126-131.
[8]翟文宝,李军,周英操,等.基于测井资料的页岩储层可压裂性评价新方法.岩性油气藏,2018,30(3):112-123.ZHAI W B,LI J,ZHOU Y C,et al. New evaluation method of shale reservoir fracability based on logging data. Lithologic Reservoirs,2018,30(3):112-123.
[9]张昊天,周文,曹茜,等.基于应力-应变模型的脆塑性测井评价.测井技术,2018,42(3):331-337.ZHANG H T,ZHOU W,CAO Q,et al. Log evaluation method of the brittle-plastic parameters based on stress-strain model.Well Logging Technology,2018,42(3):331-337.
[10] JARVIE D M,HILL R J,RUBLE T E,et al. Unconventional shale-gas systems:The Mississippian Barnett Shale of northcentral Texas as one model for thermogenic shale-gas assessment. AAPG Bulletin,2007,91(4):475-499.
[11] BOWKER K A. Recent development of the Barnett shale play,Fort Worth Basin. Search&Discovery,2003,6(2):12-20.
[12]边会媛,王飞,张永浩,等.储层条件下致密砂岩动静态弹性力学参数实验研究.岩石力学与工程学报,2015,34(增刊1):3045-3054.BIAN H Y,WANG F,ZHANG Y H,et al. Experimental study of dynamic and static elastic parameters of tight sandstones under reservoir conditions. Chinese Journal of Rock Mechanics and Engineering,2015,34(Suppl 1):3045-3054.
[13]张晨晨,王玉满,董大忠,等.四川盆地五峰组—龙马溪组页岩脆性评价与“甜点层”预测.天然气工业,2016,36(9):51-ZHANG C C,WANG Y M,DONG D Z,et al. Evaluation of the Wufeng-Longmaxi shale brittleness and prediction of“sweet spot layers”in the Sichuan Basin. Natural Gas Industry,2016,36(9):51-60.
[14] CAO Q,ZHOU W,DENG H C,et al. Classification and controlling factors of organic pores in continental shale gas reservoirs based on laboratory experimental results. Journal of Natural Gas Science and Engineering,2015,27:1381-1388.
[15] ZHANG S L,YAN J P,HU Q H,et al. Integrated NMR and FESEM methods for pore structure characterization of Shahejie shale from the Dongying Depression,Bohai Bay Basin. Marine and Petroleum Geology,2019,100:85-94.
[16]闫建平,崔志鹏,耿斌,等.四川盆地龙马溪组与大安寨段泥页岩差异性分析.岩性油气藏,2016,28(4):16-23.YAN J P,CUI Z P,GENG B,et al. Differences of shale between Longmaxi Formation and Da'anzhai member in Sichuan Basin. Lithologic Reservoirs,2016,28(4):16-23.
[17]闫建平,言语,司马立强,等.泥页岩储层裂缝特征及其与“五性”之间的关系.岩性油气藏,2015,27(3):87-93.YAN J P,YAN Y,SIMA L Q,et al. Relationship between fracture characteristics and“five-property”of shale reservoir. Lithologic Reservoirs,2015,27(3):87-93.
[18]杨宝刚,潘仁芳,赵丹,等.四川盆地长宁示范区龙马溪组页岩岩石力学特性及脆性评价.地质科技情报,2015,34(4):183-188.YANG B G,PAN R F,ZHAO D,et al. Mechanical properties and brittleness evaluation of Longmaxi shale rock of Changning demonstration area in Sichuan Basin. Geological Science and Technology Information,2015,34(4):183-188.
[19]姚军,孙海,黄朝琴,等.页岩气藏开发中的关键力学问题.中国科学:物理学力学天文学,2013,43(12):1527-1547.YAO J,SUN H,HUANG Z Q,et al. Key mechanical problems in the development of shale gas reservoirs. Scientia Sinica Physica,Mechanica&Astronomica,2013,43(12):1527-1547.
[20]王绳祖.岩石的脆性-延性转变及塑性流动网络.地球物理学进展,1993,8(4):25-37.WANG S Z. Brittle-ductile transition and plastic-flow networks rocks. Progress in Geophysics,1993,8(4):25-37.
[21]张小龙,张同伟,李艳芳,等.页岩气勘探和开发进展综述.岩性油气藏,2013,25(2):116-122.ZHANG X L,ZHANG T W,LI Y F,et al. Research advance in exploration and development of shale gas. Lithologic Reservoirs,2013,25(2):116-122.
[22]赵万春,马云朋,王婷婷,等.不同脆性岩石的声发射特征.岩性油气藏,2017,29(4):124-130.ZHAO W C,MA Y P,WANG T T,et al. Acoustic emission characteristics of rocks with different brittleness. Lithologic Reservoirs,2017,29(4):124-130.
[23] HUCKA V,DAS B. Brittleness determination of rocks by different methods. International Journal of Rock Mechanics and Mining Sciences&Geomechanics Abstracts,1974,11(10):389-392.
[24] HAJIABDOLMAJID V,KAISER P. Brittleness of rock and stability assessment in hard rock tunneling. Tunneling and Underground Space Technology,2003,18(1):35-48.
[25] BISHOPA W,GREENG E,GARGAV K,et al. A new ring shear apparatus and its application to the measurement of residual strength. Geotechnique,1971,21(4):273-328.
[26] GRIESER W V,BRAY J M. Identification of production potential in unconventional reservoirs. SPE 106623,2007.