不同围压下致密砂岩破裂过程声发射特征研究

发布时间：2018-11-12 17:14

【摘要】：揭示致密砂岩的破裂机制对致密油气储层压裂设计和压裂缝网改造具有重要的指导意义。本文采用鄂尔多斯盆地延长组长6储层致密砂岩试样,开展了不同围压下的常规三轴压缩试验,分析了围压对岩石力学性质的影响。采用声发射定位技术研究了试样破裂过程,分析了不同围压下声发射定位事件的信号特征及其时空演化序列。此外,对破裂后试样进行了CT扫描,基于CT切片图像观测了试样内部破裂特征。得到以下几点认识:(1)不同围压下,声发射时空演化差异主要表现在压密阶段。随着围压的增加,声发射事件主要发生时段后移。(2)围压对声发射特征参数累计振铃计数的影响主要表现在压密阶段,其他阶段累计振铃计数呈相似变化趋势。不同围压下均可将累计振铃计数快速增加的瞬间作为岩石即将破裂的标志。(3)随着围压的增加,岩石破裂形态趋于简单化,由拉张破裂为主的复杂形态逐渐转变为单一的剪切破裂形态。(4)CT扫描切片直观地反映了试样的破裂形态,与声发射定位所得试样整体破裂形态相吻合,并且在声发射定位的基础上进一步刻画了裂纹分布情况与各裂纹相互作用过程。采用声发射定位技术与CT扫描双重方法,研究试样破裂过程,对于深入研究岩石破裂机制具有一定的意义。
[Abstract]:It is of great significance to reveal the fracture mechanism of tight sandstone for fracturing design and fracturing network reconstruction of tight oil and gas reservoirs. In this paper, conventional triaxial compression tests under different confining pressures are carried out by using tight sandstone samples of Yanchang 6 reservoir in Ordos Basin, and the influence of confining pressure on rock mechanical properties is analyzed. The fracture process of samples was studied by acoustic emission localization technique. The signal characteristics and spatiotemporal evolution sequence of acoustic emission localization events under different confining pressures were analyzed. In addition, the fracture characteristics of the samples were observed by CT scanning based on CT slice images. The main conclusions are as follows: (1) under different confining pressures, the evolution of acoustic emission in time and space is mainly in the compaction stage. With the increase of confining pressure, the acoustic emission events are mainly moved backward. (2) the effect of confining pressure on the accumulative ringing count of acoustic emission characteristic parameters is mainly in the compaction stage, and the accumulative ringing number in other stages shows a similar change trend. Under different confining pressures, the rapid increase of accumulative ringing count can be regarded as a sign that rock is about to break. (3) with the increase of confining pressure, the fracture morphology of rock tends to be simplified. The complex morphology of tensile fracture is gradually transformed into a single shear fracture morphology. (4) the fracture morphology of the specimen is reflected intuitively by CT scanning section, which coincides with the whole fracture morphology of the specimen located by acoustic emission. On the basis of acoustic emission localization, the process of interaction between crack distribution and each crack is further described. The method of acoustic emission localization and CT scanning is used to study the fracture process of the specimen, which is of great significance for the further study of the fracture mechanism of rock.
【作者单位】：中国科学院页岩气与地质工程重点实验室中国科学院地质与地球物理研究所;中国科学院大学地球科学学院;北京石油化工学院机械工程学院;河南理工大学能源科学与工程学院;中国矿业大学(北京)力学与建筑工程学院;
【基金】：国家重点基础研究发展规划(973)项目(2015CB258501) 中国科学院战略性先导科技专项(B类)(XDB10030301) 国家自然科学基金项目(41202228)资助
【分类号】：TU45

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