Enhanced characterization of fracture compliance heterogeneity using multiple reflections and data‐driven Green's function retrieval

Abstract

The spatial heterogeneity along a fracture is a key determinant for fracture‐associated mechanical and hydraulic properties of the subsurface. Laboratory experiments have been performed to test the applicability of the nonwelded interface representation to predict the frequency‐ and angle‐dependent elastic response of a single fracture. The observation that nonwelded interface model can represent quite well the frequency‐ and angle‐dependent reflection response of a fracture has led us to develop a new methodology for estimating the spatially heterogeneous fracture compliance from the reflection response along a fracture surface. A data‐driven approach based on Marchenko equation coupled with inverse scattering to solve the nonwelded interface boundary condition has been formulated. The approach estimates the elastic wavefield along a fracture accurately, including the multiple reflections. As an extension, it offers the possibility to estimate fracture compliance using the multiple reflections. We illustrate the concept by numerically modeling 2‐D SH waves sensing the heterogeneous tangential compliance of a fracture. The stationary phase method is applied to single and double spatial integrals to analyze the effect of source and receiver aperture on the Green's function retrieval. Our results show that the use of multiple reflections allows a better estimation of the heterogeneous fracture compliance than using primary reflections alone, especially for the far offsets on the fracture plane.

Relating Hydraulic–Electrical–Elastic Properties of Natural Rock Fractures at Elevated Stress and Associated Transient Changes of Fracture Flow

“…Although our study adopted a zero-frequency assumption for the velocity calculation, the scaling effect on velocity can be addressed by considering finite wavelengths. Because finitedifference time-domain modeling of wave fields in fractured media requires more complex assumptions, such as fracture compliance (Bakulin et al 2000;Minato and Ghose 2016;Pyrak-Nolte et al 1990), the scale dependency on velocity needs to be further explored.…”

Why Multiples Do Not Contribute to Deconvolution Imaging

“…Guo et al (2015) develop interferometric and resonant migration methods which employ information contained in multiples. Also in Marchenko imaging first results indicate that the deconvolution imaging condition can be modified such that multiples contribute to the image (Minato and Ghose, 2016;Wapenaar et al, 2017).…”

Stiffness of a Fracture from AVO Inversion Incorporating Linear Slip Boundary Condition - Experimental Investigation

“…The reproducibility of the tests is ensured. Note that, for AVO inversion, obviously only the specular reflections are used; however, the full scattered wavefield has also been recently used to predict the lateral heterogeneity in fracture compliance (Minato and Ghose, 2013;2014;2016). …”