褐煤断裂特征半圆弯曲试验研究——以内蒙古胜利煤田为例  

Experimental investigation on fracture behavior of lignite and its fracturing significance:taking Shengli Coalfield as an example

作　　者：陈立超 王生维 张典坤[2] CHEN Lichao;WANG Shengwei;ZHANG Diankun(School of Mining Technology,Inner Mongolia University of Technology,Hohhot 010051,China;State Key Laboratory of Coal and CBM Co-mining,Jinneng Holding Group,Jincheng 048204,China;Faculty of Earth Resources,China University of Geosciences,Wuhan 430074,China)

机构地区：[1]内蒙古工业大学矿业学院,内蒙古呼和浩特010051 [2]煤与煤层气共采国家重点实验室,山西晋城048204 [3]中国地质大学(武汉)资源学院,湖北武汉430074

出　　处：《煤炭科学技术》2023年第5期63-71,共9页Coal Science and Technology

基　　金：国家科技重大专项专题资助项目(2016ZX05067001-007);内蒙古自治区科技计划资助项目(2020GG0317);山西省煤层气联合研究基金资助项目(2016012007)。

摘　　要：褐煤不同方位上断裂力学性质各向异性对储层体积压裂裂缝缝网形成具有重要控制,为探究层面方位对内蒙古胜利煤田褐煤断裂行为特征的影响,利用三点弯曲加载试验对层面角θ分别为90°、60°、45°、30°及divider(切分)5种内蒙古胜利煤田6煤组褐煤半圆弯曲试样静态断裂行为开展研究,结果表明:①层面角θ为90°、60°、45°、30°及divider(切分)情况下,胜利煤田6煤组褐煤Ⅰ型断裂韧度K_(IC)分别为0.045、0.058、0.073、0.084及0.096 MPa·m0.5,整体上切口切分层面型试样断裂韧度高于切口平行层面型试样,且对于切口平行层面型试样而言,随着层面角的减小断裂韧度有递增的趋势,研究区褐煤断裂力学性质具有强烈的各向异性特征;②加载位移−载荷关系显示,层面角θ分别为90°、60°、45°、30°及divider(切分)5种褐煤半圆弯曲试样三点弯加载下其断裂过程均经历孔裂隙缺陷压实阶段、线弹性压缩形变储能阶段、临界断裂破坏阶段以及断后的载荷卸载四大阶段,且全部试样断裂后期载荷迅速卸载表明煤岩断裂形式均为脆性断裂,煤岩具有较高的断裂速率,储层适于开展大规模体积压裂;③层面角θ分别为90°、60°、45°、30°及divider(切分)5种褐煤半圆弯曲试样三点弯加载过程断裂能Γ分别为64.38、80.49、112.50、146.66、及355 J/m^(2),divider(切分)褐煤试样断裂能远大于切口平行层面型褐煤试样,同等条件下沿切分褐煤层面方向造缝耗能高,压裂裂缝延展规模受限;④试验还发现,三点弯加载下研究区褐煤半圆弯曲试样断裂模式主要有拉张断裂和剪切断裂两种形式,褐煤试样的断裂路径受控于外载方向和煤岩层面方位间的空间关系,当层面角θ在45°~60°时试样断裂裂缝的曲折程度最高,在煤层气储层压裂中最易形成裂缝缝网;⑤基于褐煤断裂力学各向异性,认为内蒙古胜利褐煤储层采取水平�The anisotropy of fracture properties at different bedding orientations of lignite plays an important role in controlling the formation of fracture network of reservoir racturing.The static fracture behavior of the lignite semi-circular bending specimens of the 6 coal group in the Shengli coalfield,Inner Mongolia,is studied.The results show that:①Bedding When the angleθis 90°,60°,45°,30°and divider,the mode I fracture toughness K_(IC) of lignite of Shengli coalfield is 0.045,0.058,0.073,0.084 and 0.096 MPa·m0.5,respectively.on the whole,the fracture toughness of the sample with the notch-cut layered surface is much higher than that of the notch-parallel beddingsurface sample,and for the notch-parallel bedding-surface sample,the There is an increasing trend with decreasing fracture toughness,and the fracture properties of lignite in the study area have strong anisotropic characteristics;②The displacement-load curves shows that the fracture process of the five lignite semi-circular bending samples under three-point bending loading includes:the compaction stage of pores and cracks,the linear elastic compression deformation energy storage stage,the critical fracture failure stage,and the load unloading stage after fracture.The large stage,and the rapid load unloading of the above samples in the later stage of fracture indicates that the material fracture forms are brittle fractures,the coal has a large fracture rate,and the reservoir is suitable for large-scale volume fracturing;③The fracture energyΓof five kinds of lignite semi-circular bending samples with the bedding angleθis 90°,60°,45°,30°and dividing during three-point bending loading process is 64.38,80.49,112.50,146.66,and 355.00 J/m^(2),respectively.The fracture energy of the sample with the notch-cut layered surface in the whole process is much larger than that of the lignite sample of the incision-parallel bedding plane.Under the same conditions,the energy consumption of fracturing along the bedding direction of the split lignite is high,

关 键 词：褐煤 层面方位 断裂力学 各向异性 压裂裂缝曲折度 内蒙古胜利煤田 

分 类 号：TE32[石油与天然气工程—油气田开发工程] TU45[建筑科学—岩土工程]