Method and system for calculating shale full-angle anisotropic brittleness index

Abstract

Disclosed are a method and system for calculating a shale full-angle anisotropic brittleness index. The method comprises the following steps of calculating a VTI medium stiffness matrix coefficient; calculating a full-angle longitudinal wave speed, a full-angle fast transverse wave speed and a full-angle slow transverse wave speed; calculating a full-angle Poisson's ratio and a full-angle Young'smodulus; calculating an anisotropic brittleness index of a full-angle full-wave field; calculating a crack fracture adjustment factor of the full-angle full-wave field; calculating a brittleness indexafter calculation of the crack fracture adjustment factor of the full-angle full-wave field. According to the method, the brittleness index is calculated according to the crack fracture adjustment factor, and the angle and position of a maximum brittleness index can be found more accurately, so that calculation of the brittleness index is better in accordance with the mechanical principle and thereality.

Description

technical field [0001] The invention relates to the field of geophysical exploration, and more specifically, to a method and system for calculating the full-angle anisotropy brittleness index of shale by using multi-wave data. Background technique [0002] Due to the distribution characteristics of shale clay components and the existence of fractures, shale has obvious anisotropy characteristics. Anisotropic features are evident on both ultrasonic and seismic frequency scales. Studying the anisotropic characteristics of shale is a key issue in shale reservoir evaluation. The introduction of accurate anisotropy parameters can improve the accuracy of shale reservoir evaluation. Ignoring anisotropy will lead to errors in petrophysical analysis, interpretation of seismic data processing, and hydraulic fracturing calculations. Sayer and Vernik et al. studied the influence of shale organic carbon content (TOC) on seismic waves of shale reservoirs. Yarali defines brittleness as...

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Problems solved by technology

However, the evaluation methods for shale fracturability ignore the effects of anisotropy parameters and fracturing mechanics parameters, resulting in partial distortion and errors in the fracturability of shale gas reservoirs evaluated by elastic parameters, for example: High Young's modulus often represents high brittleness, but at the same time requires greater hydraulic fracturing pressure for fracture opening and fracturing, and due to the existence of anisotropy, the fracturing properties of shale at different angles are different; the Rickman method does not Consider fracturing mechanics parameters and anisotropy parameters

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