The Process Simulation And The Technology Optimization Of Multi-stage Solid-liquid Propellant Composite Explosive Fracturing

Now HEGF technology has a range of application,but the factors of the single-stage propellant's high burning rate,short pressure holding time have seriously restrict the formation of cracks in the scale and complexity.Thus,people proposed a multistage burning rate of solid propellant and liquid propellant complex explosion fracturing technology,but the work has stalled as the research method of liquid movement in column and wellbore crack propagation mathematical and physical model in the explosion process can't be found.Therefore,the paper just starts from the mechanism,then describes the novel charging structure,mechanism and advantage to the relatively traditional explosive fracturing technology of the multistage solid-liquid propellant explosive fracturing technology in detail.And it analyzed the effect of multistage propellant on the whole process of fracturing in detail.Then,on the basis of the solid propellant combustion model,the liquid propellant combustion model,which consists the burning equation,gas equation,the mass conservation equation and energy conservation equation is established and got a numerical solution,which can simulate the propellant burning loading process in different charge.Then,assuming that the propagation of the blasting energy in the fluid column is in the form of stress wave,the high pressure gas and liquid column is full interface contact and stress wave,the reflected wave will superpose,and the energy will dissipate in the communication process,the blasting stress superposition and liquid column motion model which consists the mass conservation equation,momentum conservation equation and energy conservation equation is established.Thereby,in consideration of crack propagation criteria,crack propagation resistance along the way,the contact area of fracture system and matrix increasing,the simplified explosive fracture extending dynamic model is established.And then,on the basis of the three established models,and linking up by the Bernoulli's equation and swelling pressure wave propagation equation,the unified multi-stage solid-liquid composite explosive fracturing stress superposition and crack propagation dynamics model is founded.Basing on the coupling model,initial and boundary conditions,the model is numerically solved and the fracturing application software is developed,which can quantitatively simulate the sensitivity effect of the number of pulses,liquid column height under the blasting point,charge combination of propellant,perforation diameter and perforation density to the fracture consequent.And the simulation results shows that in ensuring the safety of the casing and formation,the fracture can get a better effect by reducing the height of liquid column under the blasting point,increasing the number of pulses,perforation diameter and perforation density,and adjusting the charge combination of propellant in order to optimize and balance the peak pressure,loading rate,holding pressure time and energy efficiency.Then,taking the actual formation parameters as example,the paper established the physical and mathematical analytical model which can quantitatively analyze the effect of the explosion induce pre-existing cracks to the original ground stress field,and then,programming solved the model.The simulation result shows that the existing of the explosive fracturing cracks will promote the ground stress field redistribution near the well,which is conducive to the subsequent loading gunpowder forming branch cracks,and the changed stress field will promote fracture crossing and cutting during extension,which create conditions for the follow-volume hydraulic fracturing forming a large-scale complex fracture network.Finally,taking the actual well for example,optimized and designed the process parameters,which promoted the application of the technology.