Wave Propagation in Fractured-Porous Media with Different Percolation Length of Fracture Systems
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Wave Propagation in Fractured-Porous Media with Different Percolation Length of Fracture Systems M. A. Novikov1* , V. V. Lisitsa2** , and Ya. V. Bazaikin1*** (Submitted by Vl. V. Voevodin) 1
Sobolev Institute of Mathematics of Siberian Branch of the Russian Academy of Sciences, Novosibirsk, 630090 Russia 2 A. A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia Received April 16, 2020; revised April 20, 2020; accepted April 21, 2020
Abstract—We present a numerical investigation of the fracture connectivity effect on attenuation of seismic waves propagating in fractured porous fluid-saturated media. We design an algorithm for statistical modeling to generate fracture systems with prescribed percolation length. Generated statistical realizations of the fractured systems are then analyzed to evaluate the fracture-cluster length-scale. After that for all statistical realizations we simulated wave propagation observing formation of the wave-induced fluid flows. We show that fracture-to-background fluid flows are secretive to the branch size. Thus, in the case of permeable background, seismic attenuation is affected by the branch length; i.e., attenuation increases with the increase of the branches length. If the permeability of the background material is low, no fracture-to-background wave-induced fluid flows appear, whereas strong fracture-to-fracture fluid flows may take place. However, fracture-tofracture fluid flows are local and depend only on the parameters of the individual fractures and their intersections. As a result, the effect of the fracture-to-fracture fluid flows on seismic attenuation is relatively low, even smaller than the attenuation due to scattering. DOI: 10.1134/S1995080220080144 Keywords and phrases: wave-induced fluid flow, fracture connectivity, seismic modeling, seismic attenuation, porous media.
1. INTRODUCTION Estimation of fluid mobility and reservoir transport properties is one of the most challenging topics of exploration seismology and petrophysics. Recent studies address the investigation of the wave-induced fluid flows (WIFF). These flows are due to local pressure gradients during seismic wave propagation in fractured-porous media [1–3]. Usually, two types of WIFF are considered. The first type includes the fluid flows between the host rock and fractures (fracture-to-background WIFF, FB-WIFF). Second WIFF type appears locally between interconnected fractures (fracture-to-fracture fluid flow, FF-WIFF). The FB-WIFFs appear if a low-frequency (long wavelength) wave propagations. In this case, the wave period is high enough for flow to form, even in the media with quite low permeability. The intensity of FB-WIFF and, as a result, its impact on seismic signal is governed mostly by a compressibility contrast between the host rock and fracture-filling material [1, 2, 4]. High-frequency signals propagation causes FF-WIFF, which is generally defined by fracture-filling material properties and also local fracture connectivity [2–5]. Unfortunately, th
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