Azimuthal imaging of rock fractures by incorporating single borehole radar and optical data

TL;DR

This paper introduces a joint imaging technique combining borehole radar and optical data to accurately reconstruct 3D rock fracture planes, overcoming individual limitations of each method.

Contribution

A novel joint imaging approach that integrates optical and radar data for detailed 3D fracture mapping in boreholes.

Findings

Method reliably reconstructs fracture parameters.

High-resolution imaging validated by numerical and field tests.

Effective separation of up-dip and down-dip events.

Abstract

Single borehole radar detection suffers from azimuthal ambiguity, while borehole optical tests only provide information about the borehole wall. These limitations prevent either detection method from revealing the complete spatial patterns of rock fractures on their own. In this paper, we address these challenges by proposing a joint imaging method that combines the advantages of both borehole detection methods. Geological azimuthal parameters are extracted from optical images by fitting the fracture curves to sinusoidal functions. A 2D Kirchhoff time migration is then implemented using radar common offset gather. Up-dip and down-dip events are separated by the f-k transform or z-s transform, depending on their geometric relation. The complete fracture planes, including trend, dip angle, gap width, and extension length, are finally reconstructed in 3D space by mapping the migration profile using azimuthal information from optical images. The method is proven reliable and high-resolution through both numerical tests and real field data.