Study On Fracture Process Driven By Detonation Gas During The Complex Perforation In Oil Well

It is of great significance for scientific research and oil application to describe the fracture mechanism process of the rockmass around oil well, driven by detonation gas during the complex perforation. The main achievements in this paper can be concluded as follows:(1)Based on the flow behavior of detonation gas in oil well, a theoretic model of detonation gas flow in preliminary crack is established, by means of introduction of a pressure distribution function concluded from analytic result of gas flow along the crack.(2)The crack opening displacement is also modeled by referencing relationship between crack normal displacement and pressure along the crack in blasting model. The stress strength factor at the crack tip is deduced to estimate fracture initiation. Energy release rate obtained by J-integral at the crack tip is used to determine the crack spread velocity after fracture initiation. Coupling process between detonation gas flow and crack spread is also simulated based on the combination of the solid-fluid governing equations. As allow for rapid fracture process driven by detonation gas, kinetic energy increment is further introduced into energy conservation equation at the crack tip.(3)A dynamic fracture numerical solution of fracture process driven by detonation gas is performed. In the related software, three subprograms are set up: detonation gas flow, cracked rock dynamic response and fracture simulation, to realize numerical simulation of fracture process driven by detonation gas. And the software validity is proved by correlative test results.(4)The results from this numerical model agree with corresponding results from half-analyzed and concrete column test. Aim at the fracture length which is main factor in oil well to relate the production, several primary factors are discussed systematically by numerical test, to find out the most effective measures in oil well fracturing works.