Study On Fracture Distribution Of Shale Gas Reservoir Based On Acoustic Finite Element Method

With the large consumption of conventional energy resources,the unconventional resources represented by shale gas have been paid more attention all over the world.The fracture is a direct flow channel of shale gas resources,so it is very urgent to study the characteristics of reservoir fractures.Sonic logging technology is an important way to study the characteristics of reservoir fractures,but there is still a lot of space in the specific research methods and content.In this paper,the methods of solving rock mechanical parameters and the anisotropic properties by acoustic logging data were analyzed.In addition,the rock mechanics parameters and distribution were calculated.In this paper,based on the theory of acoustic wave propagation,the influence of rock mechanics parameters on acoustic wave propagation was studied by finite element method.The propagation of acoustic waves in anisotropic shale formations shows that the acoustic signal travels farther in the direction of greater elastic modulus,and the angle is 45 degrees between the position of maximum amplitude and the axis of symmetry.With the increase of anisotropy index,the ovality of the signal amplitude distribution is higher in the model.The propagation path of reflected wave was analyzed theoretically,and the formula for calculating the receiving time of reflection wave is obtained in this paper.The acoustic wave propagation in borehole and formation was studied and the results show that when the crack angle is 15 degrees and 30 degrees,the time of reflection wave is basically the same as that of theoretical calculation.When the crack angle is 45 degrees,the receiving time of the reflected wave is obviously delayed,so that it is very important to select the appropriate measuring points for the high angle fractures.The study on the general shape crack shows that the location and shape of the crack can be effectively deduced by the receiving time of the reflected wave.This paper studied the propagation of reflected acoustic waves when the reservoir fractures is filled with different media,which provides a new way for the identification of crack properties.