COAL GEOLOGY GROUP 1980 SYMPOSIUM
PROGRESS IN COAL GEOLOGY
NSW Institute of Technology Sydney, New South Wales
26th-28th August, 1980
COAL GEOLOGY GROUP OF THE GEOLOGICAL SOCIETY OF AUSTRALIA
Chairman:
Colin Ward
Vice-Chairman:
Ian Blayden
Hon. Secretary:
Michelle Smyt h
Hon. Treasurer:
Richard Britten
Hon. Editor:
Anton Crouch
Address for
Address for other
editorial matters:
matters:
Anton Crouch McElroy Bryan and
Michelle Smyth CSIRO Fuel Geoscience
Associates Pty Ltd
Unit
P.O. Box 387
P.O. Box 136
Milsons Point
North Ryde
N.S.W.
N.S. W.
2061
2113
COAL GEOLOGY GROUP GEOLOGICAL SOCIETY OF AUSTRALIA
1980 SYMPOSIUM
PROGRESS IN COAL GEOLOGY
N,S,W, INSTITUTE OF TECHNOLOGY SYDNEY, N,S,W,
26 - 28 AUGUST 1980
PROGRAMME CHAIRMAN:
IAN BLAYDEN
l
The Coal Geology Group of the Geologica l Society of Australia gratefully acknowled ges contributi ons from the following companies towards the cost of mounting the symposium . Austen and Butta Limited BP Australia Limited Broken Hill Proprietar y Company Limited Coal and Allied Industries Limited
PROGRAMME MONDAY, 25th August, 1980 . Underground Excursion at Bellambi Colliery. TUESDAY, 26th August, 1980. 8 .00- 9.30 am
Registrati on
9 .30-1 0 .00 am
OPENING REMARKS & WELCOME Dr. R. L. Werner President, N.S.W.I.T. PROGRESS IN COAL GEOLOGY - THE NEED FOR A SYMPOSIUM P. W. Goodwin Clutha Devel opment Pty Limited
SESSION I - bLuCe Robinson, Chairman GEOPHYSICS 10.00-10.30 am HIGH RESOLUTION SEISMIC REFLECTION TECHNIQUES IN THE COAL INDUSTRY P. Harman The Broken Hill Proprietary Company Limited 10.30-11.00 am MINI-SOSIE SEISMIC PROFILING OF COAL DEPOSITS IN AUSTRALIA D. King & S. Greenhalgh Earth Resources Foundation University of Sydney
SES SION I (Cont . ) 11 .00-11.30 am
Morning Tea
ll.3'.J - 12 . 00 am
IN-SEAM SEISMIC TECII NIQJES FOR COAL EXPLORATION M. W, Asten, K. J. Grezl
& L. Leung Th e Broken Hill Proprietary Company Limited 12 .00-12.30 pm
THE USE OF RESISTIVITY IN COAL EXPLORATION R. Murdoch Murdoch Geophysics (Australia) Pty. Ltd.
12.30 - 2 . 00 pm
Lunch - Union FunctioG Rooms, Level 3
2 . 00 - 2 . 30 pm
BOLT HOLE PROBES & CORE LOGGING INSTRUMENTATION K, G. McCracken & P. J. Mathew CSIRO, Division of Mineral Physi cs
2.30- 3.30 pm
PANEL DISCUSSION
3.30- 4.00 pm
Afternoon Tea
SESSION II - Dr. Cliff McElr oy - Chairm an 4.00- 5.00 pm
KEYNOTE ADDRESS COAL - THE EIGHTIES AND BEYOND R. Auste n Chairm an & Managing Direc tor Auste n & Butta Limit ed
5.30- 8.00 pm
Cock tail Party Sydney Unive rsity Union
WEDNESDAY, 27th Augus t, 1980. SESSION III - Erni.e Wrigh t, Chairm an BOREHOLE LOGCING 9.00- 9.30 am
DEVELOPMENTS IN DOWN-HOLE LOGGING A STUDY OF THE USES AND BENEFITS OF COAL EXPLORATION LOGGING R. I. Renwi ck The Shell Company of Austr alia Limit ed
9.30- 10.00 am
COMPUTERISED PROCESSING AND PRESENTATION OF BOREHOLE DATA R. J. Hende rson & J.E. Haigh Geoex Pty. Ltd.
10.00 -10.30 am
THE APPLICATION OF GEOPHYSICAL BOREHOLE LOGGING TO COAL EXPLORATION B. J. Grove s & E. A. Bowen, Amax Iron Ore Corpo ration
SESSION III (Con t.) 10.30 -11.0 0 am Morning Tea STRUCTURAL GEOLOGY 11.00 -11.3 0 am AN INTERPRETATION OF THE MINING CONDITIONS BY GEOLOGICAL ANALYSIS AT STOCKTON BOREHOLE COLLIERY R. J. Willi ams, Coll insv ille Coal Company Pty Ltd R. I. Turn er The Broke n Hill Prop rieta ry Company Limi ted 11.30 -12.0 0 am
STATISTICAL ANALYSIS OF SPACINGS BETWEEN GEOLOGICAL DISCONTINUITIES IN COAL MINES, WITH APPLICATI ONS TO SHORT-RANGE FORECASTING OF MINING CONDITIONS J. Shep herd, J. W. Creas ey & N. I. Fishe r CSIRO, Divis ion of Mine ral Phys ics
12.00 -12.3 0 pm REGIONAL AND LOCAL VARIATIONS IN VITRINITE REFLECTANCE PATTERNS AND THEIR APPLICATION TO . STRATA CONTROL INVESTIGATIONS I. Stone Cluth a Deve lopme nt Pty. Limi ted 12.30 - 2.00 pm
Lunch
SESSION IV - Nigel R-0wlands, Chairman COMPUTER PROCESSING 2.00- 2.30 pm
COMPUTER APPLICATIONS IN COALFIELD GEOLOGY K. Robert Johnson Earth Science Computer Services
2.30- 3.00 pm
COMPUTER APPLICATION IN EXPLORATION
& PLANNING OF HUNTER VALLEY NO. 1
MINE
P. P. Wootton Coal & Allied Operatio n s Pty Limited 3.00- 3.30 pm
Afternoo n Tea
RESERVE ESTIMATES 3.30- 4.00 pm
COAL RESERVE ASSESSME NT FOR AN EXPANDING INDUSTRY 0. J. Shiels Joint Coal Board
4.00- 5.00 pm 7.30 pm
Panel Discussi on Dinner - Sydney Univers ity Union
THURSDAY, 27th August, 1980. SESSION V - Professo r Neville Stephens on, Chairman MINE GEOLOGY 9.00- 9.30 am
GEOLOGICAL INVESTIGATIONS TAHMOOR COLLltKY HOLDING, SOUTHERN 6YDNEY BASIN
P. W. Goodwin Clu tha Developm rnt Pty Limited
SESSION V (Cont.) 9.30-10.00 am
APPLICATION OF GEOLOGY IN LONGWALL MINING - A CASE HISTORY LONGWALL 202 IN BULLI SEAM AT SOUTH BULLI COLLIERY B. Agrali The Bellambi Coal Company Limited
10.00-10.30 am
THE ROLE OF GEOLOGY IN THE PLANNING & OPERATION OF OPEN STRIP COAL MINES G. Boyd Utah Development Company
10.30-11.00 am
Morning Tea
COAL ANALYSES 11.00-11.30 am
COAL SEAM SAMPLING AND ANALYTICAL PROGRAMMES H. W. Read SGS Australia Pt y. Ltd.
11.30-12.00 am
COAL RANK A. C. Cook Dept Geology, Wollongong University
12.00- 1.30 pm
Lunch
SESSION VI - John Cramsie, Chairman 1.30- 2.00 pm TECHNIQUES FOR THE DETERMINATION OF GEOMECHANICAL PARAMETERS DURING SURFACE EXPLORATION J. R. Enev·er & R. McKean CSIRO, Div. of Applied Geomechanic s
SESSION VI (Cont.) 2.00- 2.30 pm GEOLOGICAL DATA REQUIREMENTS FOR ROCK MECHANICS DESIGN OF COAL MINE ROOFS B. K. McMahon & P. J. Pells McMahon, Burgess & Yeates 2.30- 3.00 pm ENGINEERING GEOLOGY AND THE ENVIRONMENT RESTORATION AND REHABILITATION G. R. Mcllveen Departm ent of Mineral Resourc es 3.00- 3.15 pm SUMMATION & EXPRESSION OF THANKS Dr. Co lin Ward Chairman , Coal Geology Group 3.30 pm Depart for Hunter Valley from Institut e of Technolo gy FRIDAY, 29th August, 1980. 8.00 am Hunter Valley Excursio n Singleto n Area SATURDAY, 30th August, 1980. 8.00 am Hunter Valley Excursio n Newcast le Area
High Resoluti on Seismic Reflecti on Techniqu es in the Coal Industry P. Harman Seismic reflecti on techniqu es have been used in Austral ia for many years to assist in coalfiel d evaluati on. They have generall y been used to infer coal seam continu ity and to locate major faults. Field practice and data processi ng was similar to that used in early oil seismic · explora tion. Over the past three years The Broken Hill Pty. Co. Ltd. has applied seismic reflecti on techniqu es similar to those first used by the Nationa l Coal Board of Gre at Britain, with the aim of improving resoluti on and locating much smaller structur es than previously identifi ed. The approach to achievin g more confiden t definiti on of small structur es involves the use of modern seismic recordin g equipme nt and digital data processing. Field practice s are appropr iately modified by scaling down spread dimensio ns to give maximum data coverage at the shallow er depths of interes t. Source and detecto r configu ration are designed to maximise the generati on and detectio n of higher frequenc ies in the ground. Accurate static correcti ons which are applied to compens ate for variatio n in surface elevatio n and inhomog eniety in surface weathere d layers are importa nt.
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Approxi mately 100 line kilometr es of high resoluti on work has now been carried out on close-sp aced grids over Cook and Leichha rdt Collieri es ·in the Blackwa ter area, Queensla nd. Line spacing was on average 200 metres. Faults with inferred throws of as little as 4 to 5 metres have been detected at depths of 300 metres. A number of known faults have been clearly detected by the method. A clearer understa nding of sedimen tary variatio ns may also be possible . The mapping of faults and steep gradien ts in these mines has enabled confiden t planning of mineable areas and panel layout. The potentia l of the seismic reflecti on techniqu e as applied in the coal industry is still relative ly unexplo ited. The role of the method in the explora tion of suitable areas will become increasi ngly signific ant as the economic importan ce of coal changes and efficien t developm ent and exploit~ tion of reserves become a necessi ty.
- 3 Mini-S osie* Seismic Profili ng of Coal Deposi ts in Austra lia D. King & S. Greenh algh Since its introdu ction into Austra lia late in 1978, the Mini-SO SIE techniq ue has found applica tion for structu ral mapping in a number of Austra lian coal deposi ts. The techniq ue has proved capable of providi ng useful structural inform ation in all coal environ ments encoun tered. Data quality is most sensiti ve to the variab ility of near surface low veloci ty layerin g, but static correc tion proced ures are availab le which mi·tiga te the problem and enable routine produc tion of medium resolut ion process ed section s. The style of data collec tion and process ing are such that the Mini-SO SIE techniq ue is more cost-e ffectiv e, relativ e to standar d seismic techniq ues, the less the total vertica l and lateral subsurf ace coverag e require d.
*
Registe red Trade Mark, Societe Nation ale Elf Aquita ine (Produ ction).
- 4 In-Seam Seismic Techniques for Coal Exploration M.W. Asten,
K.J. Grezl
& L. Leung
A review of in-seam seismic techniques for coal exploration shows that in-seam seismic is rapidly becoming an operational tool to assist in the development of. underground coal mines. At the forefront in this work at present is the National Coal Board in the United Kingdom, who have assembled equipment and expertise to facilitate regular staging of in-seam seismic trials and who have claimed some success in detecting faults up to 500 m away from development headings in seams of 1-2m in thickness. Some Government support has been made available_ to facilitate the development of in-seam seismic techniques in Australia. Preliminary field trials at Leichhardt Colliery in Queensland have given encouraging results and are the first in an on-goin~ series of trials aimed at developing an in-seam seismic exploration system for Australia. Explosives were used to generate channelled waves within the coal seam and these were detected with high fidelity at distances of up to 340m. Propagation velocities and waveform attributes were characteristic of channel waves reported by other workers and frequency content was significantly better due to the use of broadband piezoelectric detectors.
- 5 The Use of Resistiv ity in Coal Explora tion R. Murdoch In recent years, resistiv ity has become the most used surface geophys ical techniqu e in Austral ian coal explora tion. In particu lar, the techniqu e has success fully assisted drilling in the rapid location of a number of coal deposits . It has been widely used to assist geologi sts in structur al mapping ; as a tool for locating seam subcrop and weather ing, and for' determin ing areas where coal has been destroye d by intrusio ns. Relevan t applicat ions of the techniqu e will be briefly discusse d.
Bolt Hole Probes & Core Logging Instrum entation K.G. McCrack en & P.J. Mathew A bolt hole logger and a coal borehole core logger have been develope d by the CSIRO Division of Mineral Physics as part of a major program in the applica tion of nuclear techniqu es to explora tion, mining and quality control in the mining industry . In some Austral ian undergro und coal mines, the exposed roof is incompe tent mudstone or shale, overlaid with sandston e having excellen t bolt-anc horing charact eristics . It is necessa ry therefor e to determin e whether the bolt holes have -penetra ted the sandston e stratum. The
- 6 bolt hole logger, known as 'Strata snoop' , measur es the depth o.f the mudston e and delinea tes the bounda ry between mudston e and sandsto ne. The device consis ts of a CsI gamma ray detecto r and associa ted electro nics. The mudston e is detecte d .by its high natura l gamma ray activit y due to the presenc e of trace amounts of K, U and Th. In the same geolog ical horizon , the sandsto ne, is charac terised by its relativ ely low gamma ray activit y. The 'Strata snoop' probe is 25 mm in diamet er and is provide d with a series of fibregl ass extensi on rods. Extens ive tests in undergr ound coal mines have demons trated that the instrum ent can locate the mudsto ne/sand stone interfa ce to within +5cm. A Sydney -based company has been licence d to manufa cture the instrum ent. The boreho le core logger is a portab le instrum ent for the non-de structi ve and contac tless measure ment of density and ash conten t of coal boreho le cores in 0.5 cm section s. The logger i~ based on a gamma ray atte~u ation techniq ue and consis ts of a high and a low energy gamma ray source and a NaI gamma ray detecto r and associa ted electro nics. The bore core is placed in the path of a well-co llimate d gamma ray beam from the source s, and the detecto r measur es the a t tenuati on of the gamma rays. The attenua tion suffere d by the high energy gamma r ays is a measure of the density of the bore core section . The ash conten t is derived from the attenua tion suffere d by both the high and low energy gamma rays. Labora tory measure ments on simulat ed bore cores made up of coal pallets of accura tely known ash and3 density showed an accurac y of 1% ash and 0.01 g/cm respec tively for co~ls from the same area. An example log of a boreho le core section is shown.
- 7 The radia tion sourc es are well shiel ded in the lead housi ng. The radia tion level at 60 cm from the instru ment where the opera tor stand s is comp arabl e to the natur al radio activ ity from the surro undin gs.
Deve lopme nts in Down-Hole Logg ing - A Study of the Uses and Bene fits of Coal Expl orati on Loggi ng R.I. Renw ick This paper attem pts to outli ne the many varie d uses and bene fits of wire line loggi ng as part of a coal explo ratio n progra rrnne. Wire line logs meas ure the insit u phys ical prop ertie s of all form ation s encou ntere d in a boreh ole in respo nse to the vario us acou stic, elec trica l, mec h anic a l and nucle ar meas uring probe s. As such, logs are an ideal tool for qual itativ e geolo gical inte r preta tions ; used in strat igrap hic corre latio ns, locat ion o f and accu rate thick ness deter mina tion of coal seams , litho logic al deter mination s and class ifica tion of depo sition al envir onment s. Quan titati ve inter preta tions have also been devel oped to estab lish relat ionsh ips betwe en log readi ngs and vario us coal prop ertie s: coal qual ity param eters , sand /shal e ratio s, poro sitie s, fluid conte nts and the elast ic rock prop ertie s. All proce ssing and hand ling of log data is perfo rmed by comp uter via a set of compu ter progr amme s desig ned to evalu ate coal logs; optio ns such as depth plott ing, conto uring , cross -plot ting, math emat ical calcu latio ns, stati stica l regre ssion and vario us repor t prese ntati ons are avail able.
- 8 Illus tratio ns of all the log prese ntatio ns in this paper have been produ ced from actua l coal boreh ole logs assoc iated with vario us coal explo ration areas in Queen sland and New South Wales .
Comp uteris ed Proce ssing and Prese ntatio n of Boreh ole Data J.E. Haigh & R.J. Hende rson The insta llatio n of a compu ter in l oggin gtruck for the recor ding analy sis and prese ntatio n of boreh ole data offer s many advan tages over analo g recor ding. Digit al acqui sition on to stand ard compu ter tape impro ves data banki ng and stora ge, facil itate s inter preta tion with other boreh ole inform ation and provi des a ready forma t for any fu r ther proce ssing requir emen t. By provi ding suffi cient progra mming capac ity in the field unit, vario us types of proce ssing and inter preta tion can be perfor med on-si te. Spuri ous readin gs such as sonic veloc ity cycle skipp ing can be rejec ted by softw are crite ria and boreh ole effec t corre ction s applie d imme diatel y. The deriv ation of physi cal prope rties such as densi ty, ; poros ity, etc. and the inter preta tion of ore-g rades ; index gth stren rock coal ash conte nt and yield ; bed bound ary and thick ness; and lithol ogy can be made and stored on tape. Autom atic plotti ng on-si te can then produ ce logs and table listin gs of the above deriv ed data as well as produ cing "cros s plots " of diffe rent sets of param eters. The large· r plot ting areas avail able with autom atic plott ers enabl es as many as 10
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separat e traces to be placed side by side for ready correla tion . Re - plottin g of zones of interes t at expande d scales is possibl e and gains an ~ off sets can be adjuste d automa tically to provide a neater presen tation . Header inform ation is also added automa tically . The above plottin g can be perform ed whilst the truck is movin~ to a new site, thus saving on docume ntation time. The entire sequenc e of logging operati ons can be display ed as an instruc tion set for a virtual novice to follow and checks on the op erator and the equipm ent institu ted.
The Applic ation of Geophy sical Boreho le L o ~ To Coal Explor ation B, J, Groves & E. A, Bowen Geophy sical boreho le logging has now become an integra l compon ent of many coal explor ation and evalua tion program mes in Austra lia and assists in providi ng a rapid and cost effecti ve means of assessi ng a d e posit. Tangib le advanta ges are afforde d by both con vention al analogu e and digital recordi ng of the downho le data . Analogu e recordi ng enables litholo gical identif ication , drillin g operati ons contro l, and serves as an aid in correla tion between boreho les . Digital acquis ition and re~ordi ng has recentl y become widesp read within the industr y and provide s high quality data suitabl e for comput er process ing and quanti tative interpr etation .
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Th E c urrent ttend towards mini -c omputer bas e d acquisit ion systems also enables on-site process ing and plotting of geophys ical and geologic al data. Estimate s of coal quality paramet ers such as ash content, relative density and specific energy , can be readily calculat ed from digitall y recorded data to supplem ent, but not replace, laborato ry c oal quality determin ations . Discrep ancies often exist between the laborato ry and geophys ically determin ed paramet ers due to inheren t differen ces in the methods of determi nation, and the nature and size of the sample. The geophys ical estimate s, although generall y regarded as the less reliable , are of conside rable value in determin ing quality paramet ers in programm es relying heavily on noncored borehole s. Examples from exp loration programm es in New South Wales and Queensla nd illustra te the value of d i gitally recorded geophys ical logs in increasi ng the knowledg e of the litholog y and coa l quality in each deposit . Further efforts are warrante d to improve th e resoluti on and count statisti cs of present slimline Logging so nd es and to speed the developm ent and utilisat ion of newer tools , such as sonic , focussed r e sisti v ity and ne utron activati on.
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An Interpre tation of the Mining Conditio ns by Geologi cal Analysis at Stockton Borehole Colliery
R,J. Williams & R.I. Turn e r The mining conditio ns in the Young Wallsend Seam range from fair to very difficu lt . Strata stabilit y is generall y poor and this is fundame ntally Gue to the presence of an incomp e tent stratum of tuff overlyin g the seam. The tuff has been extensiv ely deformed by tectonic events, and consequ ently provides little resistan ce to the shear stresses induced by mining. The failure pattern has been analysed on two scales. On the smaller scale of between roadway s, the variatio n in mining conditio ns is shown to depend upon the sequence of mining. The early formed roadways (heading s) deform under high lateral stresses and create a stress reli e ved zone, into which subsequ ent roadways (cut-thr oughs) are driven . On the more regional scale of between panels or areas of a panel, variatio ns in strata stabilit y result from changes in the magnitud e of the virgin stress field - in particu lar, variatio ns in the degree of stored strain energy. Geologi cal reasons for this stress heterog eneity are describe d. A good correlat ion is establis hed between the dip of the north - west striking cleat and the degree of strata stabilit y . The cleat set in itself does not affect stabilit y, but is used as an indicati on of stored strain energy.
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Kinematic and kinetic analyses are shown to be of fundamental importance in understanding the var iations in strata stability. The last tectonic event is an indicator of the direction and relative magnitude of the principal stress axes for the virgin stress field prior to mining.
Statistical Analysis of Spacings Between Geological Discontinuities in Coal Mines, with Applications to Short-Range Forecasting of Mining Conditions J. Shepherd, J.W. Creasey & N.I. Fisher Black coal seams are affected by geological discont inuities that form recognisable sets and which are characterised by the properties of orientation, shape, length, vertical continuity and spacing. Whilst the properties of orientation and length the have been quite extensively investigated, varia bility of spacings of discontinuities , especially in coal, is largely unknown. Measurements of discontinuity spacings in the coal seams of several coalfields have been made using the scan -line technique, particularly around fault zones that have resulted in deleterious min ~ng c onditions . ·r he spacings along a scan -lin e can be analysed to d istinguish between (i) segments of equally spaced d iscontinuiti e s, (ii) segments exhibiting Poisson be haviou r d nd (iii) segments containing (possibly
- 13 periodic) clusters. A substantial increase in the intensity of occurrence of discontinui ties has been found in the vicinity of fault zones. Thus timely identificati on of increased discontinuity intensity can be used to forecast approaching fault zones and associated onset of unstable roof conditions and gas outburstprone coal.
Regional and Local Variations in Vitrinite Reflectance Patterns and Their Application to Strata Control Investigatio ns I. Stone The optical indicat ing s u r fa ce of vitrinite obtained from oriented coal samples may be related to the lateral c omponen t of tectonic strain. Subsequent strain events may be recorded in the vitrinite and several strain direction peaks may commonly appear in the lateral strain 'ellipse' because of incomplete overprintin g. The strain patterns can be reco gnised for both regional and localised features. Localised variations in the regional strain field around normal faults for example, show a consistent pattern which is associated with stress build-up prior to faulting and restricted zone of stress relief and re-orientat ion after faulting. Similarly, marked changes in the vitrinite reflectance character is recognised around reverse and strike-slip faults.
- 14 Investigation of regional strain patterns in the Bulli Seam in Burragorang Valley coal mines, N.S.W. was undertaken from biaxial vitrinites with reflectances as low as 1.00%. Apar t from perturbations of strain due to local features, two areas can be delineated which have different regional strain orientations. These two areas also have different roof stability characteristics when mined, and to some extent contrast structurally . Vitrinite appears to be capable of recording strain events as recent as the uplift and unloading phase in the tectonic history of the area. Analys i s of the optical properties of vitrinites may be useful in adding to the geological information retrievable from borecores, particularly as an aid to structural interpretation in relation to an established data base.
Computer Applications in Coalfield Geo l ogy K. Robert Johnson The application of computers to the assessment of coal deposits has developed rapidly over the last five years. These developments have come about mainly from the intense coalfield exploration, the vast volume of data generated as a consequence and the resultant need to evaluate and interp ret the data. Techniques which are currently available on a commercial basis are all based on field recording of borehole lithological and analytical data , the automatic plotting of borehole and seam sections followed by the generation of contour plans of
- 15 virtuall y any desired variable . The bore data are basicall y re-assem bled to form a deposit block model by interpo lation onto a regular grid for irregula rly spaced data. By interact ing with this deposit model it is possible to determin e classifi ed reserves for specific tenns over nominate d digitise d areas (e.g. property boundar ies or mining strips). These reserve estimate s can then be interfac ed for mine producti on schedule s and equipme nt capacity studies. By the use of compute rs, complex multiple seam environm ents can be properly assessed in a reasonab le time frame with a minimum labour requirem ent. The trend for the future is an increase in the applica tion of these techniqu es in producti on environm ents fo r not only opencuts but also undergro und deposits wh i ch to date have been somewha t neglecte d. The lack of speciali sed manpower has provided the main limiting factor to the evolutio n of these exciting techniqu es. As compute r hardware improves in cost-per formanc e more organis ation will adapt these techniqu es with special adaption s to specific situatio ns in given deposits as well as an increasi ng number of service organis ations offering compute r applications for the coal industry .
- 16 Comp uter Appli cation in Explo ration & Plann ing of Hunte r Valle y No. 1 Mine P.P. Woott on Hunte r Valle y No. 1 Mine is one of two mine areas alloc ated to Coal & Allie d Indus tries Limit ed from an explo ration autho rity 15 km west of Singl eton. After scout drilli ng on 2 km centr es the poten tial of the area was realis ed, as was the size of the explo ration programme to prove this resou rce of 16 major coal seams which consi sted of varyin g comb inatio ns of 38 seam split s. At this stage it was obvio us that a massi ve amoun t of bore log and analy tical data would be gener ated by such a progra mme and that comp uteris ation was wort~ consi dering to pro~e ss this data and for the drafti ng of bore and seam sectio ns and conto ur plans . In this paper the develo pment s : in field loggi ng, data edifin g, appli catio ns in repor t produ ction, reserv e calcu lation s and reasse ssmen t of explo ration data for mine plann ing will be discu ssed.
- 17 Coal Reser ve Asses smen t for an Expan ding Indu stry O.J. Shie ls In a conte xt of rapid ly incre asing coal produ ction inova tion in reser ve asses smen t would be antic ipate d but, in New South Wales at least , there has been no dram atic chang e. There has been a chang e in the gene ral attitu de to coal reser ves from indif feren ce to inter est and even conce rn. The use of the comp uter to proce ss coal data has led to a more detai led prese ntati on of coal reser ves accor ding to more crite ria than was conv enien t in the past, but littl e other chang e. Tech nical inova tion in coal minin g and coal use will proba bly reinf orce a conce rn for deta il in reser ve prese ntati on but it can be antic ipate d that the comp uter will even tuall y shift the emph asis from _asses smen t to the avai labil ity of data for proce ssing as requi red. Reser ve asses smen t now relie s almo st entir ely on analy tical data from diamo nd drill core but the use of geop hysic al techn iques , parti cula rly down hole loggi ng and core scann ing is reduc ing this relia nce. These metho ds need to be incor porate d into the accep ted reser ve asses smen t proce ss. Where coal produ ction is expan ding known reser ves must expan d at an even grea ter rate and this raise s a probl em of how large a reser ve is requi red to suppo rt a given level of produ ction . If coal produ ction incre ases in New South Wales as antic ipate d -this probl em will have to be resol ved in the not dista nt futur e.
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In the context of nationa l resource s there is a need for 'better geologic al modellin g of the coal basins so that the ultimate coal resource can be based on sound geologi cal inferenc e rather than an extrapo lation from known areas or on sparse data.
Geologi cal Investig ations Tahmoor Colliery Holding Southern Sydney Basin P.W. Goodwin The techniqu es used in the several phases of explora tion, and assessm ent of the coal resource containe d within the Tahmoor Coll i ery Holding are describe d _along with the interpre t ative problems encount ered. This Colliery Holding , straddli ng the present boundar·y between the 50uthern and southwe stern coalfiel ds, south of Picton township , contains Bulli Coal reserves lying at depths of between 360 and 450 metres. The Bulli Coal proved to be the pr-ime explora tion 2 target in the 42.5 km area and knowledg e of its detailed geology and quality was necessar y for the planning of a 2.5 million tonne per annum mining operatio n.
An alternat ive ideal explora tion programme is presente d based on knowledg e and techniqu es derived in the coal industry since the decision was made to develop the property in early 1975.
- 19 Appli cation of Geolo gy in Longw all Mining - A Case Histo ry Longwall 202 in Bulli Seam at South Bulli Colli ery B. Agral i Longw all minin g provi des sixty to seven ty perce nt of the total produ ction at South Bulli Colli ery. It is there fore a neces sity that under groun d geolo gical work be mostl y conce ntrate d aroun d proje cted longw all block s. A very detai led mappi ng ~nd close measu remen ts carrie d out in develo pment worki ngs, toget her with an adequ ate sampl ing and subse quent analy sis and testin g of the coal seam, form the basis of the geolo gical advic e in longw all plann ing. All varia bles such as roo f li tholo gy, joint ing, seam thick ness, occur rence , s i ze and exten t of stone -rolls , exten t of igneo us intru sions and assoc iated cinde r, and coal quali ty and washabili ty data are thoro ughly inves tigate d, and their varia tion patte rns are used in determ ining the most econo mic shear ing heigh t and in predicting minin g condi tions and likely quan titati ve and quali tative varia tions of the run-o f-min e produ ct. Toget her with simil ar predi ction s formu lated for other longw all -block s and - thoug h with much less preci sion - contin uous miner panel s, this geolo gical work may allow a bette r short and long- term mine plann ing by settin g varia ble advan ce rates for vario us units and for vario us subse ct~on s of longw all block s with the ultim ate aim of settin g reliab le quali ty contr ol stand ards.
- 20 Inspec tions of the face are carried out at Yegula r interva ls during the lifetim e of the longwa ll block, and all observ ations recorde d. Ini t ial predic tions are compare d to actual conditi ons, discrep ancies are analyse d and the causes for unfores een variati ons of the dilutio n ratio are assesse d as being either geolog ical or operat ional. This analys is may eventu ally lead to a modifi cation of the bas i c predic tion method . The case history of the Longwa ll 20 2 dealt with in t his paper illustr ates the step-by -step approac h used in geolog ical foreca sts, from t he early stages of 'distri ct plannin g' to the final adoptio n of an extrac tion pattern .
The Role of Geology in the Plannin g and Operat ion of Open Strip Coal Mines G. Boyd It might be claimed that ideal open strip coal mining conditi ons are those that promote optima l use of excava tion equipm ent in handlin g the minimum amount of overbu rden for the maximum rate of coal uncove red. Howeve r, many factors frustra te this ideal, signifi cant amongs t which is the inheren t make-up of coal measure sedime nts. Specif ic but pervasi ve proper ties of the sepime nts have been analyse d in an attemp t to overcom e such operati onal problem s as mass instab ility of pitwal ls, optimi sation of blast design s, assessm ent of ground excava tion charac teristic s for deep strip mining as well as the assessm ent of ground conditi ons as might effect
- 21 baseline criteria used in feasibi lity studies of new prospec ts. Relevan t propert ies of coal measure sedimen ts include· clay mineral composi tion, nature of extent of secondar y cementa tion, attitude and orientat ion of bedding , rapidity of litholog ical layering and the geotech nical charact eristics of bedding surfaces . These propert ies in turn are related to early sedimen t diagene sis, post-de position al deformation of the sedimen t stack, extent ofloleath ering influenc es in the Tertiary and seam displace ments as a result of faults develope d at various stages in the lithog~n esis of the basin sedi~en ts. These relation ships are descri~e d collecti vely in an account of tpe approach , methodo logy and techniqu es applied to the predicti on of ground, hence operatin g conditio ns, ahead of mining.
Coal Seam Sampling and Analyti cal Prograrmnes H.W. Read Physica l sampling and laborato ry testing of coal seams is essentia l if reliable data is to be obtained from which reliable assessm ents can be made regardin g in situ coal quality variatio ns, the potentia l product, its likely markets and economic value. The type and size of samples and the range of testing and analysis undertak en on those samples will vary dependin g on the likely
- 22 mining methods and possible end uses of the product, e.·g. coking, power generatio n. Careful planning is required to ensure that suitable samples are ·o btained. If insuffici ent material is obtained for specific tests (e.g. washing or coking tests) there is a real risk that the results will be misleadin g, in which case it would be preferabl e not to obtain any samples. Conversel y, taking unnecessa rily large samples (e.g. large diameter cores) when samll samples would be adequate, leads to unnecessa ry cost. Similar reasoning should apply when consideri ng sample analysis. Bore core samples from an explorati on programme must be tested in sufficien t detail to ensure all relevant informati on is obtained. The objective of an initial regiona l explorati on progranme to quickly locate the most prospecti ve parts from a large area may be satisfied by chip sampling from non cored boreholes , augmented where possible by outcrop sampling. Detailed explorati on programme s designed to prove coal seam quality and reserves will initially require small diameter (45 IIml to 62 nun) cores for laborator y testing. Most cores will- be testE?d on an individua l ply basis to allow geologica l correlatio n of various propertie s; full section composite s may be prepared for more extensive test i ng but i t is important to appreciat e that the small amoun t of sample available will not allow acc urate predictio n of potential mine or washery produc t .
- 23 Once it is clear that the depos it has econo mic poten tial, large r cores (200 mm dia.) or test pit sampl es are requir Pn to yield suffi cient mater ial for simul ation of proba ble run of mine produ ct and detai led float /sink testin g to provi de coal washe ry desig n data. Coal sampl ing and testin g does not end with the explo ration progra mme. Subse quent minin g, washe ry and blend ing opera tions r equir e contin uing testin g: (1)
as insura nce that de signed proce dures are follow ed and the corre ct produ ct maint ained ,
(2)
to ident ify geolo gical chang es in coal seam prope rties that may or may not have been ident ified by the earli er explo ration work.
Geolo gists shoul d remem ber tha t s amplin g and analy sis can be expen sive . Sampl es shoul d only be taken and tested to satis fy defin ed requi rements and the subse quent resul ts shoul d be critic ally evalu ated, no t merel y filed and forgo tten.
- 24 Coal Rank
A.C. Cook Rank is a four letter word which is more abused than used and more cormnonly misun dersto od than used imagi native ly. The simpl icity of the concep t of· coal rank as a respon se, over time, of organi c matter to elevat ed tempe rature s, under confin ing pres s ures , underp lays the signif ic ance of other variab l es and intera ctions . Univa riate paradi gms of coal rank, such as its being the positi on in the pea t -anthr acite series , mask a great but poten tially useful compl exity. Th is compl exity makes it metho dologi cally desira ble to work in terms of assess ing rank rather than mea s uring it. Few studie s accept the underl ying multiv ariate nature of rank or use the poten tial of rank as a sensit ive indica tor of, and discri minat or betwee n, geolog ical histor y. Abus e s of the rank concep t chiefl y centre d around a failur e to distin guish type-r elated eff ect s from rank-r elated effect s. For some, r elativ el y crude, purpos es this may not matter . Misuse became more seriou s when poorly define d variab les (take whole -coal volati le matter yield as an examp l e) are transfo rmed to "rank" which then become s divo r ced from its measur ement base and is more like l y to be danger ous than usefu l. At least fifty differ ent types of measu rement s (varia bles) yield result s for coaly materi al which are sensit ive to rank and have be en used to assess rank. Few, if any, of these variab les fail to posses s some inform ation conten t unique to that variab le and to this extent none i s, in absolu te
- 25 tenns, dispensible. Operationally, some variables have a higher and more easily understood infonnation content than others. It is commonplace even in the most elegant of studies on coal rank, to consider only one variable. This leads to what I tenn the underuse of rank as opposed to abuse and misuse. The use of a plexus of variables enables chemical and physical rank to be distinguished. It also allows the definition of some aspects of tQe geological history. For example, bireflectance (Rmax - Rmin) relative to maximum reflectan~e, indicates the extent of lateral stress during coalification. Similarly a combination of reflectance, carbon content and hydrogen content, c~n be shown to give a discrimination which relates to the rate at which coalification occurred. Nor are thes e nicet i es in the _ distinction of coal rank of pu re ly scientific interest. Goking prope rti es, for e>C91I1ple, are related to the maximum reflectance of vitrinite but a partially independent correlation with bireflectance is also recognisable. Coal rank is a response to a complex set of variables and should be considered as a multidi~ensional response. An accurate fix needs a multi-variate approach.
- 26 Techniques for the Determinati on of Geomechanic al Parameters During Surface Exploration J.R. Enever & R. McKean A number of relatively simple techniques are currently under review by CSIRO Division of Applied Geomechanic s, to examine their potential for providing relevant information on geomechanical parameters during surface exploratory drilling. All of these technique s have been in existence in some form or another, but have not necessarily been widely applied to coal measure strata. The prime aim of the current work being undertaken by CSIRO is to evaluate and further develop these techniques, with the eventual aim of encouraging their widespread use by exploration geologists and/or drill crews. The techniques under review fall into three broad categories: Techniques to assess geological structure: Automatic Borehole Camera Borehole T.V. Came r a Borehole Impression Packer Techniques to determine mechanica l properties: Point Load Testing Borehole Penetrome t er Drillabilit y Monitoring Borehole Pressiome t er Techniques to investigate -stress fields: Open-hole hydraulic fractur i ng Borehole pressuremet er
- 27 Geol ogica l Dala Requ ireme nts for Rock Mech anics Desig n of Coal Mine Roofs
B,K. McMaho~ & P.J . N. Pells In our view coal mine roofs are best analy sed by the theor y of maso nry beam s. This requi res a caref ul log of th ~ roof strat a emph asisin g the varia tion in rock types and the thick ness of beds and lamin ae. Suff icien t samp les shoul d be teste d in the labor a tory to provi de the mea, and stand ard devia tion of the uncon fined comp ressiv e stren gth, Young s Modu lus, Unit Mass, stab ility under wetti ng and dryin g, for each rock type and shear stren gth of each type of beddi ng surfa ce. The resu lts are also highl y sens itive to the stres s in the roof rocks . Altho ugh point load stren g th is usefu l as an index , it is not adequ ate for desig n. In our expe rienc e the most diffi cult part of coal mine rock mech anics has been obtai ning suffi cien t geolo gical data.
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Engine ering Geology and the Environ ment Restor ation and Rehab ilitatio n G. R. Mcllvee n Environ mental plannin g for the impacts of coa l mining is as much part of mine plannin g as any other design compon ent. Plannin g rehabi litatio n i s part of this plannin g proces s. It become s, therefo re, par t of mine design; rather than a procedu re which can be postpon ed. Environ mental plannin g procedu res should aim to achieve informe d and realist ic decisio ns on rehabi litatio n, based on co-ord inated evalua tion of data on natura l system s, resourc e demand s, and likely mining develop ments. Geolog ists can contrib ute at all stages: the explor ation or plannin g stage, the assessm ent stage, and the mining or monito ring stage. Basic geolog ical data are needed for environ mental plannin g, since the structu re and compos ition of the resourc e determ ines the mining method adopted and hence the environ mental impact s. Collec ting environ mental data is done most cost effecti vely during the explor ation stage; this provide s the opport unity for effecti ve design at an early stage. Geolog ists bring a natura l science backgro und to design teams compri sed largely of engine ers. Other importa nt environ mental geolog ical aspects are: hydroge ochemi cal parame ters such as the relatio nship between the distrib ution of sulphur minera ls and water quality ; ground water quality and aquifer charac teristic s ; over- and mid-bu rden phy~i~a l Ann chemic al charac teristic s and subsequ ent behavio ur as spoil; geotec hnical aspects of longter m spoil and
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final high wall stabil ities; and the herita ge value of expose d geolog ical featur es. Geolo gical inputs at both site-s pecifi c and region al scales are also requir ed at the stage when the projec t is being assess ed prior to develo pment approv al.
e chnic al exhib itors at the sympo sium:
Au stral Explo ration Servi ces Pty Limit ed Geom etrics Inter natio nal Corp oratio n Prosp ector s Supp lies Pty Limit ed Carl Zeiss Pty Limit ed