Study And Analysis On Transient Model Of Perforating Process

Perforation completion is a completion method most widely used both at home and abroad.As a key step to build the passages through which oil/gas flows from reservoirs to well heads,the perforation process plays a key role in a linkage between drilling and production.During perforation,the explosives for oil perforating charge transiently detonates and produce ultra high temperature and pressure atmosphere,which compresses and damages the copper conic liner results in a deformed conic liner and formation of a particulate metal jet.Subsequently the metal jet successfully perforates the boring casing and penetrates the reservoir rocks within a short time.In this perforation process,all the stresses and responses are impossibly deduced by simple theoretical calculation or obtained by simple experiments,but they seriously influence the perforation design scheme and perforation quality assessment and analysis.Thus,it is necessary to study and analyze the transient states of all the stresses and responses during perforation.This paper focuses on brief introduction of the knowledge on the oil/gas well perforation process and research progress,investigation of metal jet formation and penetration theory during perforation,use of a lot of large software for modeling and simulation,and analysis of the transient state model for jet formation and penetration after detonation of the explosives for oil perforating charge.Good effects have been provided.This paper has the following main contents and results:(1)HYPERMESH14.0 and LS-DYNA were used for joint simulation.A 3-D modeling software PROE was used to build a geometric model for jet perforation and penetration.This model was stored as an intermediate format to introduce HYPERMESH14.0,perform trellis partition for explosive,charge,air,boring casing,rock formation,etc.,define the parameters of the materials,set the unit algorithm,define the interaction between fluids and key words between fluids and solids,set the detonation location and time,etc.,build a transient state model,solve the equations by LS-DYNA equation solver,and obtain the final results.(2)The jet formation mechanism was studied by simulation.The simulation analysis focused on transient states of metal jet and perforating charge pressure and velocity,and dynamic response of air in the jet.The mechanism of jet formation during perforation was studied and summarized.(3)The perforation process of jet was studied by simulation.The simulation focused on the transient states of perforating gun and boring casing stress in the jet.The forces on the perforating gun and boring casing were analyzed.The perforating zone was damaged due to jet penetration,but the other zones have too small stresses to reach the yield strength of the material.(4)The jet penetration through reservoir rocks was studied by simulation.The transient states of penetration stress and effective stress and dynamic response of rock were simulated.The transient stress and response during perforation were analyzed.The hollow space formed during jet penetration was uniform and well shaped.The penetration zone was greatly damaged during penetration,but the horizontal unit stresses were little influenced.Thus,jet penetration is a safe and reliable engineering means.The above simulation results complied with the experimentally obtained laws of shaped charge jet formation and penetration,indicating that this finite element model and algorithm were correct and rational,and therefore able to used to finely study the perforation mechanism,design the perforation scheme and finely assess the perforation quality.