三轴加载下煤岩脉冲水力压裂扩缝机制研究

发布时间：2018-05-08 02:27

本文选题：脉冲水力压裂 + 脉冲频率　；参考：《岩土力学》2017年04期

【摘要】：为了研究煤岩脉冲水力压裂扩缝机制,利用三轴加载脉冲水力压裂试验系统,分别从改变脉冲频率和压裂液黏度两个方面对煤岩进行了水力压裂室内试验。试验结果表明:脉冲压力和声发射对压裂过程的响应情况可将煤岩脉冲水力压裂扩缝过程分为零散萌生、均匀扩展、突变贯通和破裂终止4个阶段,其中声发射定位点空间展布的平均速率在均匀扩展和突变贯通阶段较零散萌生阶段分别提高了4.6倍和9.6倍;声发射b值曲线的趋势显示,均匀扩展阶段煤岩内部以小尺度的微裂纹破裂为主,突变扩展阶段煤岩内部出现了较大尺度主裂缝扩展,并且部分b值曲线呈现出山脊线状与阶梯状相结合的特点;在达到最佳压裂脉冲频率前,高频脉冲压力作用的煤岩,扩缝过程的均匀扩展阶段和突变贯穿阶段的延续时间比低频对应的延续时间短;随着压裂液黏度增高,扩缝过程均匀扩展阶段的延续时间呈缩短趋势,但突变贯穿阶段的延续时间却有增长的趋势。
[Abstract]:In order to study the fracture expansion mechanism of coal and rock pulse hydraulic fracturing, hydraulic fracturing laboratory tests of coal and rock were carried out by using triaxial loading pulse hydraulic fracturing test system from two aspects of changing pulse frequency and fracturing fluid viscosity. The experimental results show that the pulse pressure and acoustic emission response to the fracturing process can be divided into four stages: scattered initiation, uniform expansion, sudden transfixion and fracture termination. Among them, the average rate of the spatial distribution of the acoustic emission positioning point is 4.6 times and 9.6 times higher than that of the scattered initiation stage in the uniform expansion and sudden transition stage, respectively, and the trend of the b value curve of acoustic emission is shown. In the homogeneous spreading stage, the microcracks in coal and rock are mainly small scale cracks, and in the sudden spreading stage there are large scale main cracks in the coal and rock, and some b value curves show the characteristics of the combination of ridge line and step shape. Before the optimum fracturing pulse frequency is reached, the extending time of the uniform spreading stage and the sudden break through stage of the fracture expansion process is shorter than that of the low frequency corresponding to the fracturing fluid under high frequency pulse pressure, and with the increase of the fracturing fluid viscosity, The extension time of the uniform spreading stage in the process of joint expansion is shortened, but the duration of the sudden change is increasing.
【作者单位】：中南大学有色金属成矿预测与地质环境监测教育部重点实验室;中南大学地球科学与信息物理学院;湖南科技大学页岩气资源利用湖南省重点实验室;
【基金】：国家自然科学基金项目(No.41302124) 页岩气资源利用湖南省重点实验室开放基金(No.E21425) 中南大学中央高校基本科研业务费专项资金资助项目(No.2016zzts433)~~
【分类号】：TD315

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