A scoping study for underground extraction at Cokal Limited’s 60%-owned Bumi Barito Mineral (BBM) Coal Project in Central Kalimantan, Indonesia, has returned positive results. The study identifies potential mining blocks totalling 67 million tonnes of coking coal resources in seams D and J.
The study recommends that the project be advanced through to a pre-feasibility study.
In March 2016, Cokal reported a total resource of 266.6 million tonnes in B, C, D and J seams of which 19.5 million tonnes was in the measured category and 23.1 million tonnes was in the indicated category. These results were based on a minimum seam thickness cut-off of 0.3 metres.
The resources of these seams can be economically extracted using open-pit mining and have been classified as both measured and indicated categories within four proposed open-pits designed in the BBM East Block.
As the remaining inferred coal resources for seams D and J are considered amenable to modern underground mining extraction methods, Cokal has compiled a scoping study which outlines the concept and rationalisation of a proposed underground mine plan for the East Block.
The seam height of the D Seam averages 1.5 to 1.4 metres while J Seam varies from 1.25 to 1.3 metres. Therefore the overall mining height variation is generally from 1.25 to 1.5 metres. These seam heights are similar to those extracted at the two highest performing longwall plow operations in the world, being Bogdanka Mine in Poland and Pinnacle in the USA.
The roof predominantly consists of very hard sandstone while the immediate 1 to 2 metres of roof consists generally of a competent siltstone. This combination is ideal for extraction of the deeper resources using underground methods such as thin-seam longwall mining.
The inferred resources in the underground mine area have been confirmed as primarily coking coal from analyses conducted in an Australian laboratory.
Because of the favourable geological conditions, the scoping study has identified the potential for four large underground mining blocks utilising the longwall method of extraction of both the D and J seams.
The mine is proposed to use three continuous miner development units prior and a built-for-purpose longwall plow. The highwall punch mine configuration and shallow nature of the inferred resources means longwall output is not constrained by outbye coal clearance systems as is experienced in similar plow operations installed in existing older mines.
Sensitivity analysis indicates the underground extraction of premium quality coking coal at BBM could be highly competitive in the marketplace.