Acoustic Zoom Inc
685 St. Thomas Line
Canada A1L 3V2
Disrupt Mining 2017 Challenge (Acoustic Zoom)
Acoustic Zoom (AZ) is an advanced geophysics company established to develop new processes for mapping the character of complex geological formations at a finer scale than previously possible. AZ’s innovative seismic method comprises a key advance in imaging the Earth’s micro-structure and one that has important application to mineral deposit delineation. The Acoustic Zoom method can produce high-resolution 3D images of a mining property’s subtle geological structure, making it possible to differentiate ore-bearing features from the barren host rock, including under areas overlain by bog and thick glacial till. The specific advance achieved is the ability to identify detail beyond that possible with state-of-the-art long offset, wide-azimuth seismic, even when very high source location density and multi-fold data are acquired.
The AZ’s unique and game-changing aspect is the capture of subtle reflectors and diffractors, which have the potential to unmask finer internal structure consistent with ore-bearing veins. The value proposition is to deliver very high resolution seismic images to targeted depths through the placement of fixed, custom-designed, receiver array patterns that can be used as antennas, supporting beam-forming and focused listening in post-processing to deliver high-resolution subsurface imagery.
Unique Higher Frequencies at Depth
Acoustic Zoom® is a novel seismic technique adapted from sonar methods that enables high-resolution imaging of geological structures using advanced multi-aspect beamforming and beam-steered listening techniques.
The method employs antenna theory to implement steerable phased arrays formed by the grouping and placement of discrete seismic receivers. The higher resolutions attainable using the method are derived from a combination of the densely clustered seismic capture that supports focusing and directed listening to better detect signals in noise, coupled with energizing the site using a specially modified, high-fidelity vibroseis source, tuned to deliver higher-frequency energy sweeps, and operated in a stacked (repetitive) mode to further increase effective signal to noise
The precision of the focused, narrow-beam receiving array, combined with the vibroseis source characteristics, make possible the delivery of unprecedented signal detection yielding processed data with finer resolution cells capable of capturing the subtle variations indicating ore-bearing veins and associated features related to site’s mineral deposit formation.
The wide-angle steering and focused listening ability of the AZ array means the footprint can be smaller in size and still return data from greater lateral distances, whereas conventional seismic arrays are constrained to image only that which lies well inside the bounds of the footprint of the sensor placement area.
Compared to Conventional Seismic
In conventional seismic surveying, resolution is determined by a combination of the dominant frequency propagated to and from the reflector and by the inversion/migration algorithm(s) used to convert the time volume to a true depth volume. In contrast, the Acoustic Zoom method uses a much high-frequency seismic source capable of producing up to 250 Hz, coupled with the discrimination/focusing/steering power of the broadband receiving array, purposely arranged as antenna theory would dictate, with element spacing at half-wavelength across the frequencies of interest to achieve both increased vertical and lateral resolution. To mitigate signal loss due to frequency dependent attenuation, the sweep is both high-frequency biased and nonlinearly modulated. Coherent stacking is then employed to boost the final signal-to-noise ratio.
The above images were obtained from fluvial sandstone dataset and processed with Acoustic Zoom’s in-house software. Upper image shows constant time slice from conventional Pre-Stack Time Migration processing; Lower image from the same data set, but processed using Acoustic Zoom’s texture enhancement imaging.
A notable distinction in this method over conventional seismic methods is that each image voxel is formed in processing only by energy reflected in the direction of a specific focused listening beam. The image does not rely on the ability to use coherent energy reflected from continuous layers. AZ’s seismic texture imaging is synonymous with identifying finer localized spatial variations of the subsurface that may be associated with critical mineral rich geo-features such as buried channels, small veins, lenses, faults, fractures and pinch-outs.
Identifying and knowing the locations of these diffracting/scattering features, as provided by Acoustic Zoom, can provide a model of the deposit and support selection of specific drill targets to guide planning, increase productivity, and eliminate the need for any wide-spaced blind drilling. Selecting new target drill locations using the model becomes evidence based, ensuring all subsequent cores result in valuable data.
Acoustic Zoom data acquisition delivers a more comprehensive dataset made possible by delivering intensively-stacked high-frequency energy from a vibroseis truck deployed at several positions relative to the receiver array placement. Combined with the receiving array focusing capability, the resulting 3D image voxel is on the order of meters. This is a major differential between the Acoustic Zoom technique and that of conventional seismic imaging, which actually discriminates against diffraction energy from smaller targets. It is in these very localized, diffraction/reflections that the true character of the geology can be revealed. This is what the AZ beam-steering receiver and high frequency and fidelity source transmissions capture and image. When geological transitions are of a subtle nature such as characterized by mineral deposits with low impedance-contrast sequences, the ability to image these subtle yet complex formations and boundaries is made possible by the beam-forming and focused listening of the AZ methodology.
Complimentary to Existing Site Information
The Acoustic Zoom seismic interpretation is enhanced by the incorporation of known features of the current geological model and any existing boreholes that are available for the site and surrounding geology. If an accepted model for the site exists, then the prime focus of the AZ analysis can be directed to identifying subtle variations, diffractions and micro faulting that can identify limits to, or extensions of, the ore-bearing rock. Existing borehole information can provide a geological reference point to refine velocity models and sharpen focus for the beam-steering and listening algorithms. The resulting AZ data set would then comprise the 3D Acoustic Zoom imagery augmented by locally available supporting information.
AZ Delivers Intensity Imagery
Beam-steered algorithms focus the signal energy throughout the survey volume, identifying subtle reflectors and diffractors that combine to image the 3D structure of the geology. Acoustic Zoom seismic data products image the structure to target depth and comprise a multi-aspect analysis of the focused imagery. Visualization of the final processed AZ data volume is possible at the mine site by the client using 3D virtual reality. To support this, we are working to incorporate a 3D visualization system with GPS positional tracking for actual in-field viewing applications.
This AZ approach holds the potential for an entirely new data interaction for clients as they can “see” the derived images appearing underfoot, which may be especially valuable for mineral deposit delineation. Directly walking the ground together with viewing the site data could reveal key earth features in the AZ data that reveal the character of the underfoot mineral vein features, all in real time relative to the position of the user’s head.
This data visualization can accentuate the textural character of the site’s geology in ways not otherwise possible, showing the internal construct of the site and the nature of the reflected energy distribution. Since the data is truly 3D in nature it lends itself to being viewed in this manner.
The Acoustic Zoom seismic has the potential to characterize mineral deposits at a greater level of resolution and in a way that is unique over existing conventional methods. AZ can also provide results in a rapid operational timeline, including the collection, analysis and characterization of geology; deposit modeling and interpretation, to provide guidance that can minimize cost and risk associated with expensive drilling programs. The high-resolution of Acoustic Zoom is also key to the successful linking of seismic results and existing borehole and other survey references to provide a coherent overall picture of the site.
A property that is being assessed for development or for expansion can be surveyed by the Acoustic Zoom method in an operational window of about 15 days, once planning, preparation and mobilization have been completed. The seismic sensors employed and the vibroseis source are commercially available for rent on the competitive market, and while we have preferred vendors, any competent contractor following our defined protocols can provide the data acquisition component.
The resulting data records are QA/QCed onsite by Acoustic Zoom personnel, and equipment is then released for demobilization to take place. Since equipment can be re-deployed quickly, one mobilization can cost effectively support a multi-phased survey approach, avoiding the need to return equipment and remobilization for execution of additional data collection. Full off-site processing can be completed at AZ Inc. site in a two-to-three week window following survey completion, and initial reports can be provided to the client’s technical staff at that point.
Depending on the mine location, size of the site to be surveyed and its relative degree of remoteness for delivering and demobilizing vibroseis trucks (everything else can be hand carried), the cost of a complete Acoustic Zoom survey and reporting is in the range of $1M to $1.5M. With full planning, preparation, execution and reporting requiring a period of about 6 weeks. A typical advance notice period to schedule the mobilization of equipment is necessary and determined by market conditions (currently favourable).
The benefits of an AZ survey include having a site model that provides an estimate of the true value of the deposit and that can guide further development planning, provide an estimate of drilling required and that can collaboratively guide continued delineation drilling. Every drill core subsequently taken can be guided by and in turn will reconfirm the site model. The level of confidence achieved when an Acoustic Zoom site model guides drilling activity, and drilling results re-confirm the model, will support the quickest and most cost-effective advancement in classification to move resources from inferred to indicated, and from indicated to measured categories. This level of productivity enhancement is our goal.