It emphasizes on the research of effects of thin layer and fissure on the full waveform is acoustic well logging by using the numerical simulation in the improved pressure-velocity finite difference (PV-FD) method. Array acoustic wave train records are numerically simulated for many sorts of asymmetrical horizontal layers around boreholes. And the variable density pattern of the really measured acoustic waveforms recorded by moving well logging tool is also simulatingly calculated and drawn. Being amplified (through the limitation to Stoneley wave's amplitude), the propagation of different types of waves through interface or layer is finely described.

A pressure-velocity finite-difference (PV-FD) method is presented for simulating the transient acoustic field of the acoustic logging problem with horizontal multilayer elastic solid or two-phase media formation. In this method, the pressure and velocity are, respectively, chosen as the variables to describe the motion of media inside and outside the borehole. The boundary conditions for pressure and velocity at borehole wall are given in cylindrical coordinate, and they are treated by conservation integral method. The PV-FD method has some advantages, especially for solving the acoustic logging problem. The treatment of singular point source is more simpler. Inner-boundary equations at the borehole wall established with pressure and velocity is of advantage for calculating stability. The absorbing effect of the artificial boundaries can be got improvement. By comparing with the results of Fourier transform under the circumstance of the homogeneous formation outside the borehole, and simulating the acoustic pressure field with the horizontal-layered elastic solid formation, the effectiveness and accuracy of this method has been examined.

The acoustic wave field excited by a pulsed point source in a fluid-felled borehole surrounded by horizontal multiple-layered media is solved by the send-analytical method. The general reflected matrix between layers is found with the mode solutions so that field of every horizontal region is expressed by the general reflected matrix.The formal solutions of n-layered formation are obtained.Numerival calculation is made on three-layered medial out of borehole. The correct display of head wave arrival is got.The effect of the thin layer on the head wave arrival and amplitude is discussed.The work in this paper make it is possible to investigate the ability to divided layer longitudinally in acoustic logging.