煤岩压裂复杂缝网与简单裂缝转换规律研究

Regularity conversion research about complex networks and simple seam cracks on coal rock fracturing

煤层水力压裂增加人工裂缝是煤层气井增产的一项重要技术措施,研究压裂裂缝扩展行为,分析裂缝扩展规律对于现场施工形成高效裂缝具有重要意义。采取大尺寸煤岩样利用岩石力学真三轴仪器,通过加载不同的应力进行实验,结果表明:在煤岩水力压裂过程中,应力差值越小,越容易形成复杂裂缝,裂缝的方向和形态比较复杂多变,轨迹难以预测;应力差值越大,其形成的裂缝越容易预测,方向和形态较为简单,轨迹容易得出。此外,裂缝走势还要受到地层煤岩的天然裂缝、强度、渗透率等因素的影响,这些因素共同制约着压裂裂缝形态的转换。

Hydraulic fracturing of coal seams to increase artificial fractures is an important technical measure to increaseproduction of coal seam gas wells, Researching on fracture propagation behavior and analyzing of crack propagation lawmake great significance for the formation of efficient cracks in the construction site. Using the large sample size of coaland rock mechanics true triaxial apparatus to experiment with different stress load shows that ： In the process of hydraulicfracturing of coal and rock, the smaller difference between the stress, the more likely the formation of complexfractures, more unpredictable and complex fracture orientation and morphology of relatively; the greater differencebetween the stress, the more predictable in the formation of cracks, the direction and shape is simple, easy to draw thetrack. Furthermore, the cracks＇ trend are also affected by the naturally fractured coal and rock formations, thestrength, permeability and other factors, these factors restrict the fracture morphology of conversion.