Method for predicting longitudinal wave velocity and attenuation of partially saturated hole fractured medium

Abstract

The invention discloses a method for predicting the longitudinal wave velocity and attenuation of a fractured medium of a partially saturated hole. The method comprises the following steps: acquiring ultrasonic experimental data of saturated rocks under different pressures; obtaining structural characteristic parameters of the partially saturated pore fissure medium; obtaining the internal fracture porosity of the rock; deducing a dry bulk modulus and a shear modulus of the pore fissure medium; deriving a bulk modulus and a shear modulus of the partially saturated pore fissure medium; fitting to obtain a characteristic jet flow length; and predicting the longitudinal wave velocity and attenuation of the fractured medium of the partially saturated hole. The model provided by the invention considers the common influence of the plaque saturation effect and the jet flow effect, and compared with a jet flow model, the longitudinal wave speed and attenuation result calculated by the plaque saturation-jet flow model are superior to the calculation result of the jet flow model, and the prediction method fully considers fluid flow mechanisms under different scales, so that the prediction accuracy is improved. And an important basis is provided for the prediction of the partially saturated hole fracture reservoir.

Description

technical field [0001] The invention relates to the field of seismic rock physics, in particular to a method for predicting the velocity and attenuation of longitudinal waves in partially saturated porous media. Background technique [0002] Partially saturated rock means that the pore space contains multiple immiscible fluids, and this immiscible feature makes one fluid distributed in another fluid in a patchy manner. When elastic waves propagate in partially saturated rocks, there will be relative displacements between pore fluids and solids, that is, fluid flow phenomenon. This phenomenon is the main cause of elastic dispersion and attenuation (Winker, 1985; Gist, 1994; Zhao Haibo et al., 2010; Ba Jing et al., 2013; Sun et al., 2014; Cheng et al., 2019). In the actual formation, due to the difference in rock pressure, fluid content and pore structure, the dispersion and attenuation of elastic wave velocity caused by fluid flow are very different. In addition, in the act...

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Problems solved by technology

However, Li et al. (2018) did not analyze the influence of pressure and saturation on the dispersion and attenuation of elastic wave velocity

At present, the existing theoretical models have achieved good results in describing the phenomenon of fluid flow at a single scale. However, in reality, rocks are affected by the comprehensive effects of fluid flow at multiple scales. Therefore, it is necessary to establish a more accurate reflection of the actual formation. A Multiscale Theoretical Model of Elastic Wave Velocity and Attenuation

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