Seismic Reflection for Hardrock Mineral Exploration: Lessons from Numerical Modeling

Abstract

The seismic reflection technique is an essential tool that is extensively applied in hydrocarbon exploration and development, but in hardrock mining and mineral exploration its use has been restricted. Ore bodies present quite elusive targets, in that they are often of limited lateral extent, have steep boundaries and complex shape, lie within high velocity undifferentiated rock and are characterized by small reflection signatures. Additional complications are that they occur at relatively shallow depth and the weak diffracted signals from the mineralization are frequently masked by many overlapping and interfering arrivals, especially mode conversions and reverberations within the weathered surface layer. Conventional CDP (common depth point) reflection profiling and even pre-stack migration reflection approaches do not favor the imaging of such structures.We have undertaken numerical model studies to determine the response of ore bodies and related geological structures (contacts, intrusions) with a view to detection and recognition on actual seismic sections. One type of modeling performed is 3-D acoustic, based on the Kirchhoff integral, to highlight the influence of out-of-plane reflections and the complicated diffraction patterns produced. The other type of modeling is full 2-D finite difference time-domain elastic simulation to not only study the reflection behavior of steeply dipping structures, but also to investigate the influence of mode conversions and to identify the most troublesome forms of noise. It is clear that ore bodies and associated geology present detectable targets, but the high velocity contrast at the base of weathering produces strong surface waves and reverberations which obscure the events of interest. The modeling can help in designing field layouts, which require long apertures and close detector spacing to image steep dips and avoid spatial aliasing problems. The classes of models investigated are quite limited, but the results nevertheless serve to illustrate the difficulties.

An introduction to seismic diffraction

“…Diffraction at edges and at localized disruptions of geological horizons represent more common causes and the amplitude behavior is often more complicated (e.g. Greenhalgh and Manukyan, 2013). However, from a wavefront perspective, i.e.…”

Prediction of tunneling hazardous geological zones using the active seismic approach

“…In this paper, we used Kirchhoff integral migration to image the HGZs ahead of the tunnel faces, and the imaging is performed based on the interval velocity model (Liu and Palacharla 2011). Although Kirchhoff migration based on ray tracing has many advantages, its imaging capabilities are limited in complex media (Greenhalgh and Manukyan 2013;Vardy and Henstock 2010).…”

Real-Time Recognition and Feature Extraction of Stratum Images Based on Deep Learning

“…With the development of industry and science and technology, the role of stratum image recognition and feature extraction in geological exploration, resource prospecting, and mining has become increasingly prominent [1][2][3][4]. Especially in the extraction of oil and natural gas, accurately identifying and predicting the distribution and properties of strata are crucial for optimizing resource extraction strategies and improving safety [5,6]. Traditional methods for stratum image recognition largely depend on human experience and inefficient manual operations, limiting work efficiency and potentially leading to high error rates [7][8][9][10][11].…”