基于真三轴压裂物理模拟系统的暂堵压裂裂缝扩展规律试验研究

Experimental study on crack propagation law of temporary plugging fracturing based on true triaxial fracturing physical simulation system

为探究暂堵压裂工艺对水力压裂裂缝扩展形态的影响规律,基于大尺寸真三轴水力压裂实验系统,以长×宽×高为300 mm×300 mm×300 mm的立方体人工试样为研究对象,开展了暂堵压裂水力压裂物理模拟试验。试验结果表明:1)多次暂堵能够产生明显的分支缝,有利于形成复杂裂缝,且多次暂堵后起裂压力增大,提升注入排量可使暂堵压裂形成更多的分支裂缝。2)相比于裸眼完井,射孔完井的起裂压力低,射孔角度与最大水平主应力存在较大夹角时,裂缝首先沿射孔方向延伸,后逐渐转向最大应力方向,多次暂堵能够使射孔完井产生明显的分支裂缝。3)增大注入排量,加快了井底憋压速率从而易导致出现多个起裂点,产生近井多裂缝。4)液体黏度显著影响岩石破裂压力,高黏度液体施工的破裂压力可增大1~2 MPa。

In order to explore the influence of the temporary plugging fracturing process on the fracture propagation pattern of hydraulic fracturing, based on the large-scale true triaxial hydraulic fracturing experimental system, a cube artificial sample with length×width×height of 300 mm×300 mm×300 mm was used as the research object, carried out temporary plugging fracturing hydraulic fracturing physical simulation test.The test results show that: 1)Multiple temporary plugging can produce obvious branch fractures, which is conducive to the formation of complex fractures. After multiple temporary pluggings, the initiation pressure increases.Increasing the injection displacement can make the temporary plugging fracturing form more branch cracks.2)Compared with open hole completion, the initiation pressure of perforation completion is lower.When there is a large angle between the perforation angle and the maximum horizontal principal stress, the fracture first extends along the perforation direction and then gradually turns to the maximum stress direction.Multiple temporary plugging can cause obvious branch fractures in perforation completion.3) Increasing the injection displacement speeds up the pressure holding rate at the bottom of the well, which can easily lead to multiple crack initiation points and multiple fractures near the well.4) Liquid viscosity significantly affects rock fracture pressure, and the fracture pressure of high-viscosity liquid construction can increase by 1~2 MPa.