Numerical Simulation Of Dynamic Underbalanced Perforating

Dynamic underbalanced perforating now has become an industry criterion of completion and perforation. The underbalance difference makes formation fluid produce an underbalance blasting backflow in the moment of perforation.The back flow washes out the residue of detonation and cleans the formation nearby the hole, so that it opens the conduit of oil. It also avoid the fluid and the solid phase in the well to enter the formation and the block effcet resulted by fluid or solid, so it protects the reservoir and improve the flow potential effeetively.The whole process of dynamic underbalanced perforating is complicated. In this paper, the study of dynamic underbalanced perforating is divided into four r components:shaped characteristics research, openings study of the rock and its constitutive characteristics, perforation depth forecasting and dynamic underbalanced perforating compacted debris cleaned with reflux study. The specific contents are as follows:(1) Shaped characteristics study:Shaped charge jet formation process is a very complex process, including detonating explosives index, explosion pressure overwhelms Liner jet and jet formation extended, in order to further study the characteristics of the jet, through numerical simulation, it gave the jet formation process, the jet velocity profile and the time variation curve of the energy emitted of the jet. The explosion maximum pressure in the calculation reach10Gpa, the maximum speed of jet head is6075m/s, the tail speed reached1986m/s, kinetic energy of the medicine type cover is6070j.(2) Openings study of the rock and its constitutive characteristics:The numerical simulation shows the effects of stress waves on the penetration of the penetration process in different variations of the boundary conditions; To study the effect of jet penetration of the target plate strength, yield strength calculations were taken to30Mpa,40Mpa and50Mpa of constitutive model simulated rock, calculating penetration depth were31.5cm,28cm and23cm, it calculated that with the increase of the yield limit, gradually reduce the jet penetration depth; Using HJC constitutive model to simulate the rock formation, by calculating different size of failure criteria and the failure strain is0.1and0.005respectively, when the failure strain is0.005, jet fast penetrate the rock (40cm), and when the failure strain is0.1, the jet penetration depth is only28cm. It shows that failure strain of the rock has a great influence on the penetration.(3) Perforation depth forecasting:Numerical simulation of jet perforating pocess is given. According to P=Z[(vj/vc)γ--1],theoretical calculations is34.2cm, but numerical simulations is30.6cm, we found that theoretical calculation result is too large relative to the simulation result for the penetration depth in the conditions of ignoring Target strength, which indicats that the strength of the target has an impact on jet penetration;(4) Dynamic underbalanced perforating compacted debris cleaned with reflux study:The calculation preliminary and exploratory studied through-hole reflow fluid impact on icleaning, numerical results show that if difference between the internal pressure of the rock and oil hole is large, then the clastic rocks will produce an instant return trend in the hole. The calculation of debris found the reflow process happened in a few milliseconds, it meeted washing requirements in dynamic underbalanced perforating.