Design And Experimental Study Of Azimuth Anisotropy Model Wells

The oil and gas reservoirs are mostly anisotropic formations.Because of the existence of the ground stress and vertical cracks in the formation,the wellbore formation is azimuthal anisotropy when acoustic logging is performed in this type of formation.In order to more accurately study the sonic propagation characteristics of such oil and gas reservoirs,it is extremely necessary to establish an azimuth anisotropy experimental model well that is identical to the actual engineering well logging environment and conduct related physical experiments.The sonic logging tool for evaluating formation anisotropy is mainly a cross-dipole sonic logging tool.At present,the development of related domestic instruments is becoming more and more mature,but experimental wells for instrument calibration have not been reported yet.Based on the theory of equivalent medium and finite difference numerical simulation results,this paper proposes a design idea of a 1:1 azimuth anisotropic model well and produces a 1:1 azimuthal anisotropic model well.The experimental test has verified the feasibility of the design idea.This paper first introduces the propagation characteristics of well boreholes in azimuthally anisotropic formations.According to the Voigt-Reuss effective medium theory,the rock and cement acoustic parameters and the effect of the percentage of volume occupied by the two on the anisotropy of the experimental model wells are calculated.The finite difference numerical simulation method was used to numerically simulate the theoretical calculation results.Based on the conclusions obtained from the two methods,the design idea of an azimuthal anisotropic model well was developed.Based on this design idea,a small-scale experimental model well was made and an orthogonal dipole acoustic wave experimental measurement was performed on the model well,which verified the feasibility of the proposed azimuthal anisotropic model well design idea.Then,under the guidance of the above-mentioned design ideas,the optimal designscheme was optimized,and a 1:1 azimuth anisotropic model well with industrial characteristics was produced in the laboratory.According to the model well production material parameters,the same numerical model as the actual well was established for numerical simulation.A series of acoustic well logging experiments was performed in the experimental well to obtain the model well's anisotropy size of 21.5% and the azimuth of160° North East.The theoretical and experimental results are consistent,indicating that the experimental wells produced in the laboratory have been successful.Finally,XMAC cross-dipole sonic logging tool was used to perform full-hole measurement in the experimental well.The results show that the design concept of the azimuth anisotropic model well proposed in this paper is effective.The model well can be used as a calibration well for cross-dipole sonic logging tools in the industry,and can provide a good experimental platform for the study of azimuthal anisotropic reservoir characteristics.