Numerical Simulation Of Unconventional Well Killing Technology

The research of unconventional killing technology is very important to the production safety of complex oil and gas wells.However,in the existing studies,there is still not an audio-visual understanding for wellbore flowing by unconventional killing,and the calculation results of killing models are also biased.Using FLUENT software,numerical simulations of bull heading and displacement method parts of unconventional killing technology were carried out;By simulating unconventional well control conditions and setting boundary conditions close to bull heading and displacement method,the pressure changing at wellhead and bottom hole,and the wellbore flowing could be calculated.It is recognized that the flow in the well is mainly in the form of upper liquid phase zone,middle mixture phase zone and lower gas phase zone when bull heading killing is performed.And the killing fluid mainly falls in the form of droplets and liquid membranes in the wellbore when displacement killing method is performed;Besides,the bottom hole pressure waves between the upper and lower limits and the wellhead pressure decreases to 0 in the form of zigzags.According to the observed physical phenomena and the theory of multi-phase flow in wellbore,the bull heading killing model and displacement wellbore flowing model were established.The influence rules of well killing parameters of bull heading and displacement method were simulated.In bull heading killing,on the premise of considering formation fracture pressure and maximum allowable pressure of equipment,killing fluid output,density and viscosity should be increased to improve killing efficiency.In displacement method killing,low viscosity and high density killing fluid should be selected to kill a well with low output in order to shorten killing time.Field experiments of automatic well killing system were carried out to test the reliability and applicability,and the results of numerical simulation were also verified.