Abstract：During fracture propagation driven by detonation gas in oil well，dynamic response of crack surface under the gas pressure results in fast fracturing. In order to simulate the dynamic fracture process，kinetic energy is introduced into the equation of energy balance to describe the energy relationship during fracture propagation driven by gas pressure. Here，an approximate formula educed by dimensional analysis is presented，which involves fracture velocity and loading rate，to calculate kinetic energy increment. Thus fracture velocity and length can be obtained by iterative solution of energy balance equation in every time step when loading rate is given. In the case study，the results show that when gas pressure rising rate becomes slow，the dynamic response of crack tip to crack development will become weak. So it is obvious that dynamic response greatly influences the ultimate fracture length.
