水平井水力裂缝延伸物理模拟试验研究

试验研究水平井裂缝扩展形态,对于正确认识水平井压裂机理具有重要的意义。根据水平井模拟压裂试验的要求,对中国石油大学(北京)岩石力学试验室组建的一套大尺寸真三轴模拟试验系统进行了改造和完善。研究共进行了2组模拟压裂试验,第1组试验研究水平井方位的变化对裂缝起裂和扩展的影响,而第2组试验研究水平主应力比由原来的1.5变为2.0时裂缝起裂和扩展的情况。结果表明:水平井水力裂缝并非发生在与最小地应力垂直的方向,在水平方向的2个主应力差异小时,水平井的水力裂缝的扩展方向具有随机性;在相同物理条件下,裂缝的起裂及近井裂缝形态除了与井筒方位角有关外,还受地应力大小比值的影响。

Physical Simulation Test on Hydraulic Fracture Expansion in Horizontal Wells

Experimental study on hydraulic fracture geometry initiated from horizontal wells was important for studying mechanics of horizontal well fracturing.According to experimental requirement,the large-size triaxial simulator was reconstructed in the rock mechanics research center in China University of Petroleum.Two groups of horizontal well hydraulic fracturing experiments were conducted.The first group was observed for the influence of horizontal well azimuth on fracturing initiation and expansion,the second group was aimed to understand the fracturing initiation and propagation when the ratio of two horizontal stresses changed from 1.5 to 2.0.Laboratory observation indicates that the expansion near horizontal wells is not perpendicular to the direction of minimum horizontal stress,and is random under the condition of small difference between the two horizontal stresses,and the ratio of the two horizontal stresses also affects hydraulic fracture geometry near wellbore.