INDOOR EVALUATION METHOD FOR SHALE BRITTLENESS AND IMPROVEMENT
LI Qinghui1，2，CHEN Mian1，JIN Yan1，WANG F P2，HOU Bing1，ZHANG Baowei1
(1. School of Petroleum Engineering，China University of Petroleum，Beijing 102249，China；
2. Bureau of Economic Geology，University of Texas，Austin 78758，USA)
Abstract：Brittleness of gas shale reservoir is of vital significance to testing and evaluating the brittleness of shale. In view of this，through literature investigation and lab tests，20 kinds of basic methods for testing brittleness，including methods based on strength，hardness and ruggedness are summarized，focusing on discussing testing theory and lab method for shale brittleness based on complete stress-strain characteristics. Considering brittleness fracture mechanism and fracture feature，brittleness of shale is defined as a synthetic characteristic of material，affected by its heterogeneity and external testing environment. To identify brittleness of shale，complete stress-strain curve consisted of pre-peak and post-peak parts should both be considered. To improve the accuracy of brittleness evaluation，complete stress-strain testing in underground environment should be simulated. Capacity for resisting inelastic deformation before rupture and losing rate of bearing capacity after rupture are the main mechanical performance of brittleness. To improve the evaluation accuracy，existing mechanical testing schemes are also modified. Meanwhile，brittleness characteristics of black shale from South China is tested through true triaxial rock mechanics tests and then evaluated using improved methods.
[1] WANG F P，REED R M. Pore networks and fluid flow in gas shales[R]. SPE 124253，2009.
[2] 李庆辉，陈 勉，FRED P W，等. 工程因素对页岩气产量的影响——以北美Haynesville页岩气藏为例[J]. 天然气工业，2012，32(4)：54–59.(LI Qinghui，CHEN Mian，FRED P W，et al. Influences of engineering factors on shale gas production—take the Haynesville shale gas reservoir in North America for example[J]. Journal of Natural Gas Industry，2012，32(4)：54–59.(in Chinese))
[3] MATT B，BILL G. Special techniques tap shale gas[J]. Exploration and Production in Hart Energy，2007，80(3)：89–93.
[4] MORLEY A. Strength of materials[M]. London：Longman Green，1944：71–72.
[5] HETENY M. Handbook of experimental stress analysis[M]. New York：John Wiley，1966：23–25.
[6] RAMSAY J G. Folding and fracturing of rocks[M]. London：McGraw-Hill，1967：44–47.
[7] OBERT L，DUVALL W I. Rock mechanics and the design of structures in rock[M]. New York：John Wiley，1967：78–82.
[8] JESSE V H. Glossary of geology and related sciences[M]. Washington D. C.：American Geological Institute，1960：99–102.
[9] HUCKA V，DAS B. Brittleness determination of rocks by different methods[J]. International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts，1974，11(10)：389–392.
[10] 苏国韶，冯夏庭. 基于粒子群优化算法的高地应力条件下硬岩本构模型的参数辨识[J]. 岩石力学与工程学报，2005，24(17)：3 029–3 034.(SU Guoshao，FENG Xiating. Parameter identification of constitutive model for hard rock under high in-situ stress condition using particle swarm optimization algorithm[J]. Chinese Journal of Rock Mechanics and Engineering，2005，24(17)：3 029–3 034.(in Chinese))
[11] DAVID G，JOHN H. Rock deformation：a symposium[M]. New York：Waverly Press，1960：66–67.
[12] HOBBS B E，MEANS W D，WILLIAMS P F. An outline of structural geology[M]. New York：John Wiley and Sons Press，1976：69–70.
[13] 朱志澄. 构造地质学[M]. 武汉：中国地质大学出版社，2004：41–42.(ZHU Zhicheng. Structural geology[M]. Wuhan：China University of Geology Press，2004：41–42.(in Chinese))
[14] 陈 颙，黄庭芳. 岩石物理学[M]. 北京：北京大学出版社，2001：10–12.(CHEN Yong，HUANG Tingfang. Rock physics[M]. Beijing：Peking University Press，2001：10–12.(in Chinese))
[15] BISHOP A W. Progressive failure with special reference to the mechanism causing it[M]. Oslo：Proceedings of the Geotechnical Conference，1967：142–150.
[16] HAJIABDOLMAJID V，KAISER P. Brittleness of rock and stability assessment in hard rock tunneling[J]. Tunnelling and Underground Space Technology，2003，18(1)：35–48.
[17] LAWN B R，MARSHALL D B. Hardness，toughness and brittleness：an indentation analysis[J]. Journal of American Ceramic Society，1979，62(7/8)：347–350.
[18] ANDREEV G E. Brittle failure of rock materials：test results and constitutive models[M]. Netherlands：A. A. Balkema Press，1995：123–127.
[19] QUINN J B，QUINN G D. Indentation brittleness of ceramics：a fresh approach[J]. Journal of Materials Science，1997，32(16)：4 331–
4 346.
[20] PROTODYAKONOV M M. Mechanical properties and drill-ability of rocks[C]// Proceedings of the 5th Symposium on Rock Mechanics. Twin Cities，USA：University of Minnesota Press，1963：103–118.
[21] HONDA H，SANADA Y. Hardness of coal[J]. Fuel，1956，35：451.
[22] ALTINDAG R. The correlation of speci?c energy with rock brittleness concept on rock cutting[J]. Journal of the South African Institute of Mining and Metallurgy，2003，103(3)：163–171.
[23] COPUR H，BILGIN N，TUNCDEMIR H，et al. A set of indices based on indentation test for assessment of rock cutting performance and rock properties[J]. Journal of the South African Institute of Mining and Metallurgy，2003，103(9)：589–600.
[24] YAGIZ S. An investigation on the relationship between rock strength and brittleness[C]// Proceedings of the 59th Geological Congress of Turkey. Ankara，Turkey：MTA General Directory Press，2006：352.
[25] RICKMAN R，MULLEN M，PETRE 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.
[26] 金 衍，陈 勉，张旭东. 天然裂缝地层斜井水力裂缝起裂压力模型研究[J]. 石油学报，2006，27(5)：124–126.(JIN Yan，CHEN Mian，ZHANG Xudong. Hydraulic fracturing initiation pressure models for directional wells in naturally fractured formation[J]. Acta Petrolei Sinica，2006，27(5)：124–126.(in Chinese))
[27] 金 衍，陈 勉，周 健，等. 岩性突变体对水力裂缝延伸影响的实验研究[J]. 石油学报，2008，29(2)：300–303.(JIN Yan，CHEN Mian，ZHOU Jian，et al. Experimental study on the effects of salutatory barrier on hydraulic fracture propagation of cement blocks[J]. Acta Petrolei Sinica，2008，29(2)：300–303.(in Chinese))
[28] 金 衍，陈 勉，张旭东. 利用测井资料预测深部地层岩石断裂韧性[J]. 岩石力学与工程学报，2001，20(4)：454–456.(JIN Yan，CHEN Mian，ZHANG Xudong. Determination of fracture toughness for deep well rock with geophysical logging data[J]. Chinese Journal of Rock Mechanics and Engineering，2001，20(4)：454–456.(in Chinese))
2012, Vol. 31 
