Study On Near Surface Hydraulic Fracturing Simulated Test And Simulation Analysis

Hydraulic fracturing is a process of uplifting rock and soil mass and forming fracture fracture by using fluid pressure.In recent years,the application prospect of near-surface hydraulic fracturing technology near free surface has gradually attracted the interest of many scholars.Near-surface hydraulic fracturing technology plays an important role not only in controlling fracturing effect and preventing shallow pollution in horizontal well fracturing,but also in pre-inducing controllable collapse to increase production and protect the overall stability of the mine.It is also of great analytical value for the interpretation of physical phenomena in nature,such as the formation of rock caps formed by plutonic rocks and volcanic eruptions.Up to now,the application of near-surface hydraulic fracturing technology has been carried out by foreign scholars for more than ten years,while the domestic research on this technology is very little.In this paper,we will use the near surface hydraulic fracturing model test and the cohesive module in the finite element software(ABAQUS)to carry out numerical simulation to study the effects of various factors,such as the injection rate of fracturing fluid and the viscosity of fracturing fluid,on the fracture morphology.In this paper,we have absorbed the internationally recognized theory that the surface of near surface hydraulic fracturing crack is modeled as rigid plate and the upper surface is modeled as elastic film.Based on the experience of near surface hydraulic fracturing test abroad,we have improved the near surface hydraulic fracturing test bench to carry out indoor model test.In the model test,we can change the fracturing fluid by controlling the variables.The injection rate and the viscosity of the fracturing fluid were observed and recorded,and then the difference of the shape and trend of the near surface crack propagation was analyzed.In addition,the bulging test was carried out to measure the peeling strength of the films by means of the built test bench.The cohesive element of finite element ABAQUS software is used to simulate hydraulic fracturing,and the results of laboratory model test are verified by changing the displacement of fracturing fluid and the viscosity of fracturing fluid corresponding to the injection rate and the viscosity of fracturing fluid in laboratory test.In this paper,laboratory tests and numerical simulation are used to verify the effects of injection rate of fracturing fluid and viscosity of fracturing fluid on fracture propagation and morphology.When the viscosity of fracturing fluid is high,short and wide fractures will be formed;when the viscosity of fracturing fluid is low,narrow and long fractures will be formed.It has a certain guiding role for the practical application of near surface hydraulic fracturing.