2. Systematic Exploration for Coal Deposits
• Introduction:
• Systematic exploration of a coal concession is essential in lowering
the cost of exploration and ensuring that all aspects of a deposit’s
geology are understood before commitment to major capital
expenditure to develop the deposit. The coal MUST be considered
to have potential for economic recovery before commitment to
development.
• Fully understanding the geology will lead to efficient and effective
mine planning and scheduling in the longer term operation – it
starts early in the exploration process – forming the basis for the
origin of the deposit will control the exploration process.
• There are two Codes or Guidelines that can be used in determining
how to approach exploration: - Indonesian National Standard and
the JORC Code from Australia. There are other guidelines available
but it will depend on the knowledge of the exploration geologist on
which guidelines to use and how to manipulate the information in
them as to how to improve the efficiency of his exploration.
3. Systematic Exploration for Coal Deposits
• The reason for this paper is because of the spread in exploration costs between
companies currently operating in Indonesia. Lets use the a unit such as 1 million
tonne of recoverable coal (JORC Code) – that is 1 million tonne that under the
economic environment is considered to be mined economically. The range in
exploration costs for Kalimantan varies from US$4500 to over US$ 975000. In 1999
• What is the difference between the exploration practise that account for the
difference in the cost?
• The potential solution to this question is that there is a fundamental difference in
the approach to exploration and maybe a systematic approach that the geologist
can incorporate in his exploration style that will lead to minimising the cost, still
cover all the basic requirements and lead to a successful assessment of a deposit
and lead to a successful mining operation.
• What will be presented in this paper is an approach to more efficient and effective
exploration practice – it is up to the individual geologist to develop his own unique
style for investigating geological deposits and hopefully at a lower cost
4. Systematic Exploration for Coal Deposits
• In defining ways to get control of the exploration costs we will look at
two codes or guidelines – the INDONESIAN NATIONAL STANDARD and
the JORC Code.
• Indonesian National Standard:
• Generally deals with resource classification and is based on three
geological parameters:
• Sedimentary consistency: What is the extent of deposit in three
dimensions – strike, width and thickness of the seam, presence of seam
splits, in-seam partings, washouts, non deposition of the coal =>
complexity of depositional environment.
• Quality Variation: Is the quality consistent over the seam
development area or is there variation => simple to complex. How much
variation and does it require special or extended sampling systems.
• Tectonism: Is the deposit cut by faults, what is the
distance between fault sets, are the faults in single sets or are they in
multiple combinations. Realistically the complexity of the deposit will
evolve as the exploration is completed and initial exploration can be
supplemented with additional and infill drilling programs.
5. GEOLOGICAL
CONDITION
PARAMETER
SIMPLE DEPOSIT MODERATE DEPOSIT COMPLEX DEPOSIT
1 SEDIMENTATION
Continuity / Extent Thousands of metres Hundreds of meters Tens of metres
(South Banko, South Sumatera,
Satui, Senakin, South Kalimantan)
(Cerenti, Riau, Sangatta, East
Kalimantan, Rantau, South
Kalimantan)
(Ombilin, Bojongmanik, West
Java, Bengkulu)
Variation of Thickness Little variation Low to moderate variation Highly Variable
(Senakin, South Kalimantan,
Tanjung Enim, South Sumatera)
Banjarsari, South Sumatera) (Ombilin, Batulicin, South
Kalimantan)
Seam Splitting Rare Some Numerous
(Bifurcation / Coalescence) (Muara Tiga Besar, South
Sumatera, Patengas, East
Kalimantan)
(Gunung Batu Besar, South
Kalimantan)
(Sangatta, East Kalimantan)
2 QUALITY
Variation of Quality Little variation Variable Highly Variable
(West Banko, South Sumatera,
Senakin, Satui, South Kalimantan
(Air Laya, South Sumatera,
Meulaboh, Aceh)
(Air Kotok, Bengkulu)
3 TECTONIC ASPECTS
Dip / Seam Attitude Horizontal to Sub Horizontal Low to Moderate Moderate to Steeply Dipping
(Cerenti, Riau) (Upau, Tutupan, South
Kalimantan, Bengkulu)
6. Faulting (Cerenti, Riau) (Upau, Tutupan, South
Kalimantan, Bengkulu)
Folding Horizontal to Low Frequency Low to Moderate Frequency Intensely Folded
(South Bangko) (Loa Janan-Loa Kulu, East
Kalimantan.)
(Ambakiang, Warukin Fm., South
Kalimantan, Bengkulu)
Faulting None to Rare Some Frequent
(South Bangko) (Senakin, Tanjung Fm, South
Kalimantan)
(Tutupan, South Kalimantan)
Intrusion None Some Numerous
(West Senakin, South
Kalimantan)
(Suban, Bukit Kendi, Air Laya,
South Sumatera)
(North Bukit Bunian, South
Sumatera)
NB: Sub-classification within the above table is on the basis of the whole deposit
characteristics and not on a part of the deposit – Individual deposits can and do contain
simple to complex versions of all of the above however, the approach to exploration
should be on the general assessment of the deposit.
7. GEOLOGICAL
CONDITION
•CRITERIA RESOURCES
HYPOTHETHICAL INFERRED INDICATED MEASURED
•Distance (m) Probable Proven
SIMPLE •Point of Observation X 1500 1000 X
1500
1000 X
500
X 500 X 500 Deposit Specific
MODERATE •Point of Observation X 1000 500 X 1000 250 X 500 X 250 X 250 Deposit Specific
COMPLEX •Point of Observation X 400 200 X 400 100 X
200
X 100 X 100 Deposit Specific
•Estimation Error (%) – not
based on geo-statistics
Estimate 60 40 20 5 - 10
•Geological Confidence
(%)– not based on geo-
statistics
Estimate 40 60 80 > 80
JORC CODE
•First Assumption: All deposits have simple geology until proven otherwise – therefore we basically start
exploration in recconnaisence mode – wide space observation points gathering information leading into an
exploration strategy. JORC classification is related to economically feasible deposits for the current economic
situation.
•NB: Deposit Specific – Companies and more importantly exploration geologist have the right to determine the data
point spacing required at this level. The geological confidence required by the company prior to further commitment
of funds for further exploration or development will determine this spacing.
•Question on JORC – Is the deposit likely to be offered for joint development or require some funding – if the answer
is YES you need to adopt a JORC related exploration program.
8. Systematic Exploration for Coal Deposits
• Before we commence exploration we must determine the following:
• Is the company likely to ask for external financing and/or look for joint venture partner?
• If there is a remote possibility of this happening – lending institutions and venture partners usually insist on due diligence study possibly to
JORC standard.
• Therefore all exploration should be conducted with this in mind and possibly contact or get in consultants that can complete JORC assessment
or write up and sign off JORC statement. The exploration should be conducted along JORC guidelines or at least multiples of JORC
recommendations. By using multiples of JORC it is much easier to infill the drilling to achieve JORC Classification.
• Exploration planning is now possible and should consist of the following:
• Field reconnaissance – looking for outcrop – measure thickness, strike and dip – make a plan of the results.
• Exploration Drilling – this drilling can be completed using spot coring – unless the deposit consists of numerous thin coal seams and is
completed with downhole geophysics for every hole.
• Initially plan for wide spaced reconnaissance drilling based on a multiple of the JORC code – (simple geological deposit).
9. Systematic Exploration for Coal Deposits
• As soon as you have enough geological data complete a Geological Model to try and determine the
basin limits. Use insitu strip ratios for initial target/s- it may be possible using the outcrop
information to complete a preliminary geological model and use it to guide further exploration.
The model is important to work with in order to target the next most likely economic coal – ALWAYS
WORK FROM GOOD TO BAD OR UNKNOWN.
• Form a theory on how the coal formed in that location and as exploration continues adjust / modify
the depositional theory to match the real information.
• Relook at drilling plans and using strip ratio - refocus the drilling to target zone. DO NOT DEVIATE
FROM THE DRILLING PLAN – THE AIM OF THE EXERCISE IS TO GATHER AS MUCH BROARD BASED
INFORMATION TO BE ABLE IN THE NEXT PHASE TO FOCUS ENOUGH EXPLORATION TO BRING YOU
TO PRODUCTION – allow you to complete EIS, AMDAL and Feasibility Study
• Complete next phase of development drilling includes quality, geotechnical and geo-hydrology
investigation.
• And before committing to a start-up pit area Complete Loxline drilling to determine the exact start
of the initial overburden - a mistake here can lead to extensive start-up costs
• Remodel and determine most prospective start up operation area
• Using model strip ratios determine start up area and then design development drilling program for
start up operations
• NB: FOLLOW THE DRILL PLANS _ ANY VARIATION SLOWS DOWN THE TIME IT TAKES TO BECOME
OPERATIONAL AND GET A RETURN FROM THE DEPOSIT.
10. Systematic Exploration for Coal Deposits
• THINGS TO BE AWARE OF WHEN EXPLORING
• Always measure the dip of every coal seam in a drill hole.
• JORC requires the lithology is reconciled against the downhole geophysical log for the hole. So
downhole logs are a very useful piece of data and can be used to determine quality variations and
seam splits.
• At reconnaissance level investigation – touch coring is preferred together with downhole logging =>
representative quality and location of seam splits and partings.
• Loxline drilling minimises mining costs by reducing overburden removed by mining fleet
• Ensure you use the geometry of the location to get overlap of part of the boreholes adjacent to
each other (TanΩ= Opposite/Adjacent)
• Core drilling should extend a minimum of 1 metre into the floor of the coal seams.
• If possible use exploration drillholes to gather more information on geotechnical, groundwater
hydrology and maybe piezometer installation.
• Should also check all boreholes for fine grained very dark grey to black sediments for possible acid
mine drainage material containing unstable fine grained pyrite.
• Also should drill below any proposed dump area in case they contain economic coal reserves
11.
12. EXPLORATION STAGES
RECONAISSANCE PROSPECTING PRELIMINARY
EXPLORATION
DETAILED EXPLORATION
Topographic Mapping (Scale)
Geologic Mapping (Scale)
Geophysical Investigation (method)
Geohydrology Investigation
Technical Geology Investigation
Drilling
1. Number of drilling point
2. Drilling point range (m)
3. Depth range (m)
4. Incremental Strip Ratio (coal)
5. Cumulative Strip Ratio (coal)
Minimum Coal Seam Thickness *)
Dirt Parting Thickness **)
Test pit
Test ditching
Geotechnical Sampling - design
Ground water hydrology
The following table can be used to help define and control the exploration program
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16. The aim of this presentation was to illustrate the there are different approaches to
exploration and the overall exploration cost will be related to the work you complete.
However, if you define the limits of the deposit,
determine a broad scale approach to gaining the initial understanding of the deposit,
match the exploration program in line with the initial understanding of the geology,
build geological models as soon as you can and
use the models to guide your exploration
there is every chance you can reduce your exploration costs to a manageable
level.
In the process you will have collected enough data to allow the deposit to be
classified under JORC CODE and be able to complete Feasibility Study, Environmental
Impact Statement and comply with all other local requirements for a successful
mining operation
Now all you have to do is think your own exploration programs and determine WHAT
DO I HAVE TO DO TO BECOME MORE EFFICIENT and ACHEIVE ALL THE OBJECTIVES OF
THE EXPLORATION ?
