Belfast is the latest sizeable high value-add coal project under Exxaro’s stewardship in Mpumalanga. The project area, some 10km south-west of the town of Belfast, is accessed via the N4 national road. The new Belfast mine is an important thermal coal resource for Mpumalanga, and has an expected life of mine of 17 years (for the first phase).
Construction started in November 2017, and first coal production is expected early in 2020. The mine is scheduled to produce A-grade steam coal for the export market, as well as middlings products of thermal coal for local consumption.
A two-stage, 500tph dense medium separation (DMS) plant will be established to enhance processing and preparation of coal produced at the site, and will include a fines DMS and filter section.
From 1967 to 1983, 78 boreholes were sunk. Of these, 43% were drilled by the Fuel Research Institute of South Africa (FRI) and Trans-Natal Steenkoolkorporasie Beperk (TNS). Eyesizwe Mining conducted drilling between 2001 and 2003 and Exxaro Resources’ drilling campaign started in 2008. To date, 153 boreholes have been drilled on the farms Zoekop 426JS, Leeuwbank 427JS and Blyvooruitzicht 383JT.
The exploration resource drilling undertaken by Exxaro has been vertically oriented diamond and percussion (structure) drilling using conventional equipment and TNW (60mm) or NQ (47,6mm) core size. The boreholes were logged and sampled by Exxaro geologists and logging was undertaken using Exxaro standard codes reflecting the lithology and sedimentary structures. Textures of the lithologies observed are based on the sphericity of the grains; sorting; maturity; cement type; vertical variations in grain sizes (grading); and mineral inclusions (sulphides, oxides and carbonates). Sampling was based on a combination of physical appearance of the coal and logging results. The coal was analysed at the Bureau Veritas Group. The latest internal and external audits were conducted in 2016.
The project area is in the Witbank coalfield and consists of four regionally correlated seams and a local seam. In some areas, seam 4 (S4) is weathered away. The seams are generally divided by an upward coarsening cycle of basal carbonaceous mudstone, carbonaceous siltstone, fine-grained sandstone and medium to coarse-grained sandstone. The parting between seam 3 (S3) and seam 2 (S2) consists of two sedimentary cycles. The top cycle is a 2 to 3m upward fining cycle, followed by a 4 to 6m upwards coarsening cycle. The strata in which the coal seam occurs consist predominantly of fine, medium and coarse-grained sandstone with subordinate mudstone, shale, siltstone and carbonaceous shale. Seam 2, the most prominent of the coal seams, varies in thickness from 1,0m to 4,33m with an average thickness of 2,83m. In the northern part of farm Zoekop 426 JS, the seam has been split into no 2 seam and no 2U seam. The seams are separated by clastic parting, which consist of an upward fining cycle 0,44m to 4,27m of basal, medium to coarse-grained sandstone.
Evaluation of the Belfast project began in 2007 and several resource estimates have been generated to date. Initial studies focused on data integrity and a complete database validation of the then GBIS database, sourced from Eyesizwe, was completed in 2007 before a geological model comprising Eyesizwe-only boreholes were compiled in 2008. Subsequent geological models (25m x 25m grid size), all compiled in Minex geological modelling software and using the Minex growth algorithm, entailed updates with validated Exxaro boreholes and model refinements based on technical integrity (last model, 2012). Coal quality compositing is undertaken in Minex on a weighted average basis.
Resource classification is based on SANS 10320:2004 guidelines. The primary criteria are the number of boreholes intersecting a coal seam(s) within a specified area and the confidence in projecting the coal quality across each seam, based on analysis of core samples from individual borehole intersections. Borehole density (points of physical and applicable quality observations), coal quality continuity and geological structure are considered to outline the various resource categories. Criteria for estimating mineable tonnes in-situ (MTIS) include visually determined coal thickness and quality continuity, a 1,0m thickness cut-off, and a 5% geological loss.
Airborne geophysics (aeromagnetic survey) and ground geophysics (magnetic and electromagnetic) have been undertaken at different times since inception to support the geological structural interpretation.
Geotechnical studies focused on the considerations required for mining as well as constructing infrastructure. The studies centered around proposed pit areas and entailed drilling five un-orientated cored diamond boreholes that were geotechnically logged and material submitted for physical analysis. A comprehensive hydrogeological study included hydro-census and groundwater quality analysis.
Reasonable prospects for eventual economic extraction
All criteria (table 24) have been considered for resources inside and outside the LoMP, the latter supported by a concept study. Environmental approvals and additional land acquisitions for phase 2 (area to the north of the current LoMP) can be reasonably demonstrated within the context of existing approvals and local, regional and national legislation.
The 2012 geological model was used for the Belfast bankable feasibility study, together with a geotechnical report dated 2012 (Belfast feasibility study: geotechnical investigation). The geological data was used as supplied and no compositing was necessary in terms of plying. The data was aggregated and averaged from the smaller geological grid sizes of 25m x 25m to the mining blocks that are orientated to the mining direction and 45m x 45m in size.
The reserve model is a replica of the resource model, but with added modifying factors. The level of investigation for the Belfast reserve is a completed and approved feasibility study. The modifying factors used are:
- Mining method: Modified benching with doze-over stripmining
- Geotechnical: For high-wall stability, soft material is mined at least one strip ahead of hard and coal-mining activities
- Geohydrological: The pit floor was considered to minimise water handling in the pit face
- Mining limits: The following mining limits were applied to the resource model:
• Economic cut-off
• Farm boundary cut-off – only farms bought for phase 1 of the project were considered
• Tenure and licence approvals
• Seam thickness – only seams with a thickness of over 1m were considered
• Environmentally sensitive areas such as waterways and wetlands.
- A factor of 5% was applied to ROM as a mining loss. The quality of coal was considered not to be affected by the mining loss
- A contamination factor of 0,1m of floor (footwall) was added onto the ROM and qualities duly adjusted. The assumption was for a CV of 0MJ/kg and ash of 100%
- The plant is designed to make a primary export product and a secondary local thermal product. A slimes loss of 6% and plant efficiency factor of 94,5% were applied to calculate the resultant product.
Total reserves are expected to be depleted within 17 years, whereas the allowable period under the mining right is 30 years. It should be noted that there are resources falling outside the reserve due to various factors that could increase the LoMP. An amount of 0,5Mt inferred resources was considered for the LoMP but not converted to reserves. Proved reserves are derived from the measured resource category. Northern-located measured and indicated resources have not been converted to reserves due to outstanding surface-purchasing agreements.
We do not know of any pertinent risks or other material conditions that may impact on the company’s ability to mine or explore, including technical, environmental, social, economic, political and other key risks.
A number of operational excellence initiatives are under way to prepare for the mining operation. One of these is implementing a concise exploration plan that will start in early 2018 at a cost of some R3 million. It aims to optimise the two box-cut areas and first five years of production. Exploration activities will produce high-resolution information on overburden characterisation (enhance slope stability and mineability), coal qualities, seam structure (optimise boxcut boundaries) and small-scale weathering and geological structural information. A number of the holes will be used to enhance the groundwater monitoring and management plan. Holes will be downhole geophysically logged to confirm depth and enhance seam correlations. As mining begins, we plan to conduct detailed continuous geology reconciliations to refine predictive measures and enhance future mining and coal processing outputs. Geological data capture and data management will be conducted in a new centralised geological database for optimised data security and accessibility.