煤岩层理对水力压裂裂纹扩展影响试验研究

Experimental Study on the Influence of Coal Bedding on Crack Propagation of Hydraulic Fracturing

摘要: 水力压裂是煤层气开采的有效手段，储层增透效果取决于裂纹扩展距离与形态复杂程度，而两者又受到层理的影响。为深入研究层理对压裂效果的影响，按照层理与压裂的方位(垂直和平行)，开展压裂试验，利用非金属超声探测仪和声发射对压裂过程中进行监测，从裂纹扩展形态、缝宽、渗透流量等方面对压裂效果进行综合评价。试验结果显示，垂直层理方位压裂效果明显优于平行层理方位压裂，裂纹扩展延伸长度最长，整体呈“人”字型，最大、小缝宽之比为24，过水断面渗透流量k = 7.50 × 10⁻⁴ cm³/s，分别为平行层理方位压裂的3倍、219.15%，建议在垂直层理方向上合理的布置压裂井，有利于提高煤层气储层的渗透性。

Abstract: Hydraulic fracturing is an effective means of coalbed methane mining, and the permeability enhancement effect depends on the crack propagation distance and morphological complexity, which are also affected by the bedding Angle. In order to further study the effect of bedding Angle on fracturing, related fracturing tests were carried out according to the orientation of bedding and fracturing (vertical and parallel), non-metallic ultrasonic detector and acoustic emission were used to monitor the fracturing process, and the fracturing effect was comprehensively evaluated from the aspects of crack growth form, crack width and permeability flow rate. The test results show that the vertical bedding azimuth-oriented fracturing effect is significantly better than that of parallel bedding azimuth-oriented fracturing. The crack propagation and extension length is the longest, the overall shape is “human”, the ratio of the maximum and small crack widths is 24, and the seepage flow rate of the through water section k = 7.50 × 10⁻⁴ cm³/s, which are 3 times and 219.15% of the parallel bedding azimuth-oriented fracturing effect, respectively. It is suggested that rational placement of fracturing Wells in vertical bedding direction is conducive to improving the permeability of coalbed methane reservoir.