Bero.it (J.M.C.); [email protected] (L.Z.); [email protected] (C.R.) Exploration and Development Analysis Institute of PetroChina Changqing Oilfield Corporation, Xi’an 710018, China; [email protected] National Institute of Oceanography and Applied Geophysics–OGS, Geophysics, 34010 Trieste, Italy College of Mathematics and Statistics, Zhoukou Normal University, Zhoukou 466001, China Gossypin Autophagy Correspondence: [email protected]: Elastic wave propagation in partially saturated reservoir rocks induces fluid flow in multi-scale pore spaces, top to wave anelasticity (velocity dispersion and attenuation). The propagation traits cannot be described by a single-scale flow-induced dissipation mechanism. To overcome this difficulty, we combine the White patchy-saturation theory plus the squirt flow model to receive a new anelasticity theory for wave propagation. We look at a tight sandstone Qingyang location, Ordos Basin, and execute ultrasonic measurements at partial saturation and various confining pressures, where the rock properties are obtained at full-gas saturation. The comparison in between the experimental data along with the theoretical benefits yields a relatively very good agreement, indicating the efficacy from the new theory. Key phrases: partial saturation; patchy saturation; squirt flow; P-wave velocity dispersion and attenuation; anelasticity; ultrasonic measurementsCitation: Wu, C.; Ba, J.; Zhong, X.; Carcione, J.M.; Zhang, L.; Ruan, C. A brand new Anelasticity Model for Wave Propagation in Partially Saturated Rocks. Energies 2021, 14, 7619. 10.3390/ en14227619 Academic Editor: Eugen Rusu Received: 5 October 2021 Accepted: six November 2021 Published: 15 November1. Introduction Seismic waves induce fluid flow and anelasticity (the wave-velocity dispersion and dissipation aspect) in rocks saturated with immiscible fluids [1]. The level of anelasticity is determined by the in situ stress, fluid content material and sort, and pore structure. This topic is hugely relevant to petroleum exploration and production. WIFF (wave-induced fluid flow) occurs at Dodecyl gallate Autophagy several spatial scales that will be categorized as macroscopic, mesoscopic, and microscopic [9]. The initial is the wavelength-scale equilibration approach occurring between the peaks and troughs of a P-wave, although the mesoscopic length is a lot bigger than the typical pore size but smaller sized than the wavelength. The microscopic scale is in the very same order of magnitude because the pore and grain sizes. The macroscopic mechanism has been discussed by Biot [102] and is typically known as the Biot relaxation peak (generally at kHz dominant frequencies). The basic assumptions are that the rock frame is homogeneous and isotropic, along with the relative motion amongst the grains plus the pore fluid is governed by Darcy’s law. Nearby fluid flow on meso- and micro-scales are neglected, and consequently, the Biot peak cannot clarify the observed wave anelasticity at all frequencies [13]. Partial saturation results in fluid heterogeneity at the mesoscopic scale as well as the stress difference involving fluid phases causes wave dissipation at low frequencies [9,149]. White [20] proposed the very first patchy-saturation model (the White model, spherical pockets). Dutta and Od[21] reformulated this model by using the Biot theory, although Johnson [22] generalized it to patches of arbitrary geometry by using a branch function. Liu et al. [23] analyzed the effect from the fluid properties. Furthermore, dissimilar pores, with distinct shapes (micro-fractures and intergranular pore.
