Numerical Simulation And Analysis Of Rock Fragmentation By Particle Impact Drilling

At present,oil and gas resources in shallow layer are more and more deficient,but there are still oil and gas resources in deep hard layer.However,the traditional drilling technology and methods do not have satisfactory effect of drilling.The low breaking efficiency directly affects the economic benefits of drilling engineering,which seriously restrict the development of extraction of oil and gas resources in deep layer.Particle impact drilling is a new type of drilling method,which is used to break the rock mainly by particle impact,which has a strong ability to break the hard rock.Compared with the traditional drilling method,the drilling speed of PID(particle impact drilling)is higher,and it can achieve a better economic benefit.The main content is as follows:In FLUENT module in Workbench,the unified parameters are set firstly and the simulation of the accelerating process of particles in the nozzles of different shapes is carried out.The results shows that the nozzle with smooth surface called streamline has a better acceleration effect.Then the influence of the in-ellipse shaped and out-ellipse shaped nozzles on the acceleration process is studied,and the acceleration effect of out-ellipse shaped nozzle is better,but its energy conversion rate is lower.Finally,the influence of particle density on the acceleration process is studied.It is found that the larger the particle density is,the smaller the velocity of the fluid and particle is,but the change of the velocity is small.And the velocity of fluid and particle is getting larger with the volume fraction of particles increases.According to the results above,this paper selected a reasonable particle velocity to simulate the progress of impact in AUTODYN module of Workbench.The material model of this progress is RHT,and the model parameter is verified before the simulation.After the simulation of particle impact based on AUTODYN,a conclusion can be obtained that the bigger the particle density is,the larger the mass loss of rock is.During the simulation progress,the single particles,two particle and different three particles models are established respectively.And the influence of incident velocity angle and particle spacing are researched.Then the relation curve graphs describing how the angle and spacing affect the rock-breaking volume and depth are drawn.Some conclusions can be obtained by analyzing the results:1,when a single particle crush the rock with an angle of 0°?30°,the rock breaking effect is better;2,when two particles with incident angle of 0 degree crush rock,the rock breaking effect is better;3,when the three particles spacing is over 1 reference radius,rock breaking volume changes little;4,when the three particles spacing is about 1 reference radius,the particles reach the maximum depth of invasion.