The Finite-difference Simulation Of The Porous Cylindrical Pipe Simulating Source And Formation Of Axis-asymmetry Transverse Isotropy Medium

Acoustic well logging is one of the important well logging methods in oil well logging. It can be used to explore the site and the character of oil and gas by continuing record and instant acoustic source pulse which is excitated in the well and affected by formation . It is a important basis to make sure the attribute and parameter of the formation.The mechanic of excitation of borehole acoustic wave is closely interrelated to the characteristics of the formation and the system of the borehole's geometric composition . It involves different types of medium, for example , quasielastic medium, elastic medium, Biot solid and anisotropic medium. The acoustic field's propagation is also interrelated to the source of the acoustic, so it is involved different types of the source, such as point source, cylinder source, and asymmetrical source, so on.. As the need of the explore the oil and gas of the complex formation and the improvement of the exact explain, it has been more and more important to search in the theory of acoustic well logging and method of explain in complicated borehole environment. Apply the pure numerical method–finite-different method to solve the borehole acoustic wave, which is one of the important and effective means in the forward research of the acoustic well logging.In this paper, the research work is about the system of small opening cylindrical tube acoustic type which is around of bad-distributed Biot solid medium propagate the acoustic field, which is used the two-dimension acoustic pressure and velocity finite-different(PV-FD) method. And use a three-dimensional sv-fd method to simulate the acoustic fall waveform of the axial asymmetry transverse isotropy formation, which is propagate by the dipole source.Firstly, to simulate the mass steel tubes is strewn at random distribution which are used by realize system of well logging, we use the small opening cylindrical tube type in this paper. In the condition of the medium that out of the borehole is bad distribution Biot medium build the formula of PV-FD, firstly, the benefits to use this method is the acoustic pressure is a scalar quantity, it just needs one portion, but the displacement is a vector, it needs two portions with two-dimension question; secondly, it is considered easily to deal with the source; thirdly, because of the displacement quantity of the vertical directions isn't restrict each other, it leads the calculation of the difference is instability,. So import the acoustical pressure to describe the fluid, the inside boundary condition is easily to deal and the calculation is stable. In the premise of validating the method's correct, research the effect of hole cylindrical tube's porosity to the waveform, it can be seen in the result that when the porosity becomes bigger, the longitudinal mode wave is well controlled which radiates along the cylindrical tube, it incamates the hole's effect in fact well logging acoustic system and prove the hole cylindrical tube's feasibility. When there is horizontal delamination outside of the well, the full wave can incamate the wave's refection on the interface clearly, and it can also be used presumed the horizontal layer's position and thickness by the full wave.Secondly, complete the three-dimension stress-velocity finite-difference simulation of the condition that the symmetry axis of transverse isotropy medium tilted intersect with the axis of well. Solve some key questions such as educe the matrix of three dimension space elastic quantity which is related to azimuth, build the equation of SV-FD in cylindrical reference frame, deal with the origin's singularity in fluid well, and so on. In condition of the axis of the medium is horizontal with that of well (vertical transverse isotropy medium) contrasts with discrete wave number method's result, validate the correct of the method of SV-FD. Calculate when angle is 0°,45°,60°,90°, the data of across dipole well logging, through the contract of the each data in the same angle, it can be seen clearly of the fission of the transverse wave, and the fission becomes bigger with the angle's augment, when the medium's axis is upright with the axis of well (horizontal transverse isotropy medium), the fission of transverse wave is the most obvious. The fast and slowly velocity of transverse wave that distill of full wave is same to calculate by theoty. Calculate the data of across dipole well logging in incline formation, afford the basis of improved word, so it has important significance.