By Kerina Taylor
Accurate coal resource modelling depends on representing geological conditions as faithfully as possible. But in structurally complex deposits, conventional modelling methods can struggle to capture the relationships between coal seams and internal waste, introducing inaccuracies that affect mine planning and grade control.
Multi-ore-percent block coding offers a targeted approach to preserving geological detail in these challenging environments, while retaining established modelling workflows elsewhere in the deposit.
The limitations of conventional seam modelling
Gridded seam models (GSM) are widely used in thermal coal resource modelling. They preserve seam geometry, align with stratigraphic interpretations, and support established resource and reserve reporting workflows.
In relatively continuous, gently dipping coal deposits, this seam-centred approach works well. However, in folded, faulted, or tectonically disturbed coalfields, including those found across Southeast Asia and Western Canada, seam continuity can break down at a scale that conventional GSM representations cannot adequately capture.
Seam splitting, interburden pinch-out, and multiple seams intersecting a single mining bench can force modellers to make artificial seam correlations or sacrifice internal-waste detail. Both can introduce errors before geological information reaches mine planning and grade control.
Preserving geological detail with multi-ore-percent coding
Multi-ore-percent block coding addresses these limitations by allowing multiple seam classifications and their volumetric proportions to be represented within a single mining-scale block.
Unlike a GSM cell, which must resolve to a single seam correlation, a multi-ore-percent block can retain primary and secondary seam codes, associated coal quality, and waste percentages. This preserves geological information that conventional seam-centred modelling might otherwise discard or misattribute.
The approach is intended to complement, rather than replace, GSMs, particularly where structural complexity makes conventional seam correlations unreliable.
Implications for dilution and reconciliation
The differences between conventional seam correlations and multi-ore-percent representations become particularly relevant at mining-block scale, where tonnage, coal quality, and internal waste directly influence operational decisions.
Preserving these characteristics within the block model can provide a more detailed representation of geological variability and support two important operational challenges: forecasting dilution before mining and understanding reconciliation variances between resource estimates, grade control, and production.
Where seam correlations must be forced through complex geology, some reconciliation discrepancies may reflect limitations in the modelling format rather than estimation uncertainty alone.
Multi-ore-percent coding offers a potential means of identifying and reducing these modelling-related discrepancies.
Applying the right approach
Not every coal deposit requires multi-ore-percent modelling. Conventional GSMs remain appropriate where geological continuity supports reliable seam correlations.
Instead, factors such as seam splitting frequency, structural disturbance, and interburden variability can help identify areas where more detailed block coding may provide value.
By applying multi-ore-percent coding selectively, mining teams may be able to improve the representation of complex coal deposits without disrupting established modelling workflows across the remainder of the resource.
Learn more about how Hexagon MinePlan supports geological modelling, resource evaluation, and mine planning to help mining teams make more informed decisions.