Preprints
https://doi.org/10.5194/egusphere-2022-1388
https://doi.org/10.5194/egusphere-2022-1388
 
02 Jan 2023
02 Jan 2023
Status: this preprint is open for discussion.

Seismic wave modeling of fluid-saturated fractured porous rock: Including fluid pressure diffusion effects of discrete distributed large-scale fractures

Yingkai Qi1,2, Xuehua Chen1,2, Qingwei Zhao1,2, Xin Luo1, and Chunqiang Feng3 Yingkai Qi et al.
  • 1State Key Laboratory of Oil & Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu, 610059, China
  • 2Key Laboratory of Earth Exploration & Information Techniques of Ministry of Education, Chengdu University of Technology, Chengdu, 610059, China
  • 3Exploration & Development Research Institute of Henan Oilfield, Sinopec, 473000, China

Abstract. The scattered seismic waves of fractured porous rock are strongly affected by the wave-induced fluid pressure diffusion effects between the compliant fractures and the stiffer embedding background. To include these poroelastic effects in seismic modeling, we develop a numerical scheme for discrete distributed large-scale fractures embedded in fluid-saturated porous rock. Using Coates and Schoenberg’s local effective medium theory and Barbosa’s dynamic linear slip model characterized by complex-valued and frequency-dependent fracture compliances, we derive the effective viscoelastic compliances in each spatial discretized cell by superimposing the compliances of the background and the fractures. The effective governing equations of the fractured porous rock are then characterized by the derived anisotropic, complex-valued, and frequency-dependent effective compliances. We numerically solved the effective governing equations by mixed-grid stencil frequency-domain finite-difference method. The good consistency between the scattered waves off a single horizontal fracture calculated using our proposed scheme and those calculated using the poroelastic linear slip model shows that our modeling scheme can properly include the FPD effects. We also find that for a P-point source, the amplitudes of the scattered waves from a single horizontal fracture are strongly affected by the fluid stiffening effects due to fluid pressure diffusion, while for an S-point source, the scattered waves are less sensitive to fluid pressure diffusion. In the case of the conjugate fracture system, the scattered waves from the bottom of the fractured reservoir and the reflected waves from the underlying formation are attenuated and dispersed by the FPD effects for both P- and S-point sources. The proposed numerical modeling scheme can also be used to improve migration quality and the estimation of fracture mechanical characteristics in inversion.

Yingkai Qi et al.

Status: open (until 02 Mar 2023)

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Short summary
Fractures tend to dominate the mechanical and hydraulic properties of porous rock and impact the scattering characteristics of passing waves. Thus, understanding wave propagation in fractured porous rock will help to find a solution to geothermal, oil, and gas. This study takes into account the poroelastic effects of fractures in numerical modeling. Our results demonstrate the scattered waves from complex fracture system are strongly affected by the fractures for both P- and S-point sources.