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Frequency domain finite element total absorption pml method for tti media

A finite element and full absorption technology, applied in the field of geophysical exploration, can solve problems such as numerical instability, increased calculation amount, and insufficient accuracy, and achieve good stability, save calculation time, and save calculation memory requirements.

Active Publication Date: 2017-11-14
CHINA UNIV OF PETROLEUM (BEIJING)
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Problems solved by technology

The existing two advanced finite element absorption boundaries are C-PML and M-PML absorption boundaries. C-PML has higher accuracy in the case of extreme incident angles, but in some extremely anisotropic media, numerical values ​​will appear. unstable
M-PML has high stability in extremely anisotropic media, but it needs to set a thicker PML absorbing layer, which greatly increases the amount of calculation, and the accuracy is not high enough if the correction factor is not optimized enough.

Method used

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  • Frequency domain finite element total absorption pml method for tti media
  • Frequency domain finite element total absorption pml method for tti media
  • Frequency domain finite element total absorption pml method for tti media

Examples

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Embodiment 1

[0093] Consider a TTI acoustic logging model whose sound source is a monopole sound source with a center frequency of 3 kHz. The formation outside the well is obtained by rotating a VTI formation by 45°, and its generalized Hooke matrix is In this problem, the absorbing boundary layer occupies only 8 mesh thicknesses, which is much smaller than the wavelength, which is a very big challenge to the numerical simulation method.

[0094] figure 1 From left to right are the wave field diagrams of the absorption boundary of M-PML, C-PML and the fully absorbing PML of the present invention. It can be seen in the figure that for this model, under the absorption boundary of M-PML and C-PML, there are very obvious boundary reflections and instability along with the propagation of the wave field. Fully absorb the PML boundary conditions, with better absorption effect and better stability.

[0095] Next, we will investigate the comparison of the absorption effect when the value of m i...

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Abstract

The invention relates to a frequency domain finite element total absorption PML method applicable to a TTI medium. A frequency domain finite element total absorption PML boundary condition is constructed, high-precision acoustic logging simulation in a TTI medium complex borehole condition is realized, a numerical simulation result in agreement with the theoretical solution is obtained, and a solid data support is provided for manufacturing of an acoustic logging instrument and evaluation on a complex oil and gas reservoir layer by using the acoustic logging data. Scaling factors of X-direction and Z-direction absorption boundaries in C-PML and scaling factors of X-direction and Z-direction absorption boundaries in M-PML are integrated to be fused to evanescent wave suppression factors and tangential attenuation factors for totally-absorbed X-direction and Z-direction absorption boundaries. The method of the invention has the beneficial effects that through constructing the total absorption PML boundary condition, advantages of the C-PML and the M-PML are considered, and the high efficiency when the frequency domain finite element PML absorption boundary solves the TTI medium is realized. Acoustic logging numerical simulation on a TTI shale formation can be carried out accurately and high efficiently, and essential theoretical basis is provided for the manufacturing of the acoustic logging instrument and development of the shale gas reservoir.

Description

technical field [0001] The invention belongs to geophysical (logging) exploration methods, in particular to the field of elastic wave numerical simulation. Background technique [0002] With the exploration and development of oil and gas fields, unconventional oil and gas resources such as shale gas have become a hot spot in exploration and development. It is of great significance to use numerical simulation to investigate the propagation law of borehole acoustic waves in shale formations for effective exploration and development of shale oil and gas, as well as for researching instrument structures and guiding instrument development and manufacturing. Among various commonly used numerical simulation methods, the finite element method has its unique advantages: high precision, adaptable to complex boundaries, conducive to the coupling of different fields, and easy to handle various types of sound sources. It plays an important role in elastic wave field simulation. Value. ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01V1/50
CPCG01V1/50G01V2210/6169
Inventor 王兵张阔马明明
Owner CHINA UNIV OF PETROLEUM (BEIJING)
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