体积压裂中的岩石脆性指数及其数值模拟
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摘要
为利用脆性指数指导各类岩石储层的改造工艺优选、工艺参数优化和压裂液优选,对岩石的脆性指数开展影响因素和变化规律研究。对脆性指数的表征采用能够反映岩石的破坏特征的全应力-应变曲线方法。采用数值模拟方法对可能影响岩石脆性指数的各因素开展岩石破坏全过程的模拟,从而获得不同条件下的全应力-应变曲线,并通过曲线上的关键特征点评价岩石的脆性指数,该方法具有可重复性强、不受岩心加工水平和实验设备影响等优势。研究表明:岩石颗粒尺寸、非均质性程度、砾石组分及围压等会明显影响岩石的脆性指数,随着岩石碎屑颗粒的减小、岩石均质性程度提高、砾石颗粒尺寸变小,岩石的脆性均会增强;而围压或埋深的增加,岩石的脆性会降低。根据上述影响因素和规律,为现场体积压裂设计提出了针对性建议。
In order to make full use of the brittleness index to guide the stimulating technology, parameter and fracturing fluid optimizations for each kind of the rock reservoir, the studies on the influencing factors and change laws were conducted for the rock brittleness index. The total stress-strain curve method that can show the rock damage feature was adopted to characterize the brittleness index. The numerical simulating method was used to model the whole process of the rock damage for each factor maybe influencing the rock brittleness index, and then the total stress-strain curve was obtained under the different conditions, and moreover through the key feature points on the stress-strain curve, the brittleness index of the rock was evaluated. The method possesses the following advantages: strong repeatability, not be influenced by the core process level and testing instruments and so on. The results show that the rock particle size, heterogeneity degree, gravel composition, confining pressure and so on obviously affect the brittleness index of the rock. With the decreases of the rock detrital & gravel particle sizes, and moreover with the rise of the heterogeneity degree, the brittleness index increases; while the rises of the confining pressure and buried depth, the index will decrease. According to the influencing factors and laws stated above, the directed suggestions are proposed for the SRV fracturing in the field.
In order to make full use of the brittleness index to guide the stimulating technology, parameter and fracturing fluid optimizations for each kind of the rock reservoir, the studies on the influencing factors and change laws were conducted for the rock brittleness index. The total stress-strain curve method that can show the rock damage feature was adopted to characterize the brittleness index. The numerical simulating method was used to model the whole process of the rock damage for each factor maybe influencing the rock brittleness index, and then the total stress-strain curve was obtained under the different conditions, and moreover through the key feature points on the stress-strain curve, the brittleness index of the rock was evaluated. The method possesses the following advantages: strong repeatability, not be influenced by the core process level and testing instruments and so on. The results show that the rock particle size, heterogeneity degree, gravel composition, confining pressure and so on obviously affect the brittleness index of the rock. With the decreases of the rock detrital & gravel particle sizes, and moreover with the rise of the heterogeneity degree, the brittleness index increases; while the rises of the confining pressure and buried depth, the index will decrease. According to the influencing factors and laws stated above, the directed suggestions are proposed for the SRV fracturing in the field.
引文
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[12]YARALI O,KAHRAMAN S.The drillability assessment of rocks using the different brittleness values[J].Tunnelling & Underground Space Technology,2011,26(2):406-414.
[13]金璨.砾岩储层力学性质及破裂规律研究[D].北京:中国石油大学,2017.JIN Can.Study on mechanical properties and fracture law of conglomerate reservoir[D].Beijing:China University of Petroleum,2017.
[2]王永辉,卢拥军,李永平,等.非常规储层压裂改造技术进展及应用[J].石油学报,2012,33(增刊1):149-158WANG Yonghui,LU Yongjun,LI Yongping,et al.Progress and application of hydraulic frcturing technology in unconventional reservoir[J].Acta Petrolei Sinica,2012,33(S1):148-158.
[3]JARIPATKE O A,CHONG K K,GRIESER W V,et al.A completions roadmap to shale-play development:A review of successful approaches toward shale-play stimulation in the last two decades[R].SPE130369,2010.
[4]RICKMAN R,MULLEN M J,PETRE J E,et al.A practical use of shale petrophysics for stimulation design optimization:All Shale Plays Are Not Clones of the Barnett Shale[R].SPE 115258,2008.
[5]AKINBINU V A.Relationship of brittleness and fragmentation in brittle compression[J].Engineering Geology,2017,221:82-90.
[6]HUCKA V,DAS B.Brittleness determination of rocks by different methods[J].Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts,1974,11(10):389-392.
[7]李庆辉,陈勉,金衍,等.页岩脆性的室内评价方法及改进[J].岩石力学与工程学报,2012,31(8):1680-1685.LI Qinghui,CHEN Mian,JIN Yan,et al.Indoor evaluation method for shale brittleness and improvement[J].Journal of Rock Mechanics & Engineering,2012,31(8):1680-1685.
[8]张军,艾池,李玉伟,等.基于岩石破坏全过程能量演化的脆性评价指数[J].岩石力学与工程学报,2017,36(6):1326-1340.ZHANG Jun,AI Chi,LI Yuwei,et al.Brittleness evaluation index based on energy variation in the whole process of rock failure[J].Journal of Rock Mechanics & Engineering,2017,36(6):1326-1340.
[9]周辉,孟凡震,张传庆,等.基于应力—应变曲线的岩石脆性特征定量评价方法[J].岩石力学与工程学报,2014,33(6):1114-1122.ZHOU Hui,MENG Fanzhen,ZHANG Chuanqing,et al.Quantitative evaluation of rock brittleness based on stress-strain curve[J].Chinese Journal of Rock Mechanics & Engineering,2014,33(6):1114-1122.
[10]SONG L,WANG Y,LI Y.A novel experiment method of evaluating the brittleness of rock[R].SPE 167730,2014.
[11]唐春安,王述红,傅宇方.岩石破裂过程数值试验[M].北京:科学出版社,2003.TANG Chun’an,WANG Shuhong,FU Yufang.Numerical test of rock failure[M].Beijing:Science Press,2003.
[12]YARALI O,KAHRAMAN S.The drillability assessment of rocks using the different brittleness values[J].Tunnelling & Underground Space Technology,2011,26(2):406-414.
[13]金璨.砾岩储层力学性质及破裂规律研究[D].北京:中国石油大学,2017.JIN Can.Study on mechanical properties and fracture law of conglomerate reservoir[D].Beijing:China University of Petroleum,2017.