ORE RESERVE ESTIMATION - MineTech · PDF fileORE RESERVE ESTIMATION METHODS, MODELS AND...
16
ORE RESERVE ESTIMATION METHODS, MODELS AND REALITY Proceedings of the Symposium sponsored by The Geology Division of ClM, and held in Montreal, Quebec, May 1O-11, 1986 Edited by M. David, R. Froidevaux, A.J. Sinclair and M- Vall6e THE CANADIAN INSTITUTE OF MINING AND METALLURGY
Transcript of ORE RESERVE ESTIMATION - MineTech · PDF fileORE RESERVE ESTIMATION METHODS, MODELS AND...
ORE RESERVE ESTIMATION
METHODS, MODELS AND REALITY
P r o c e e d i n g s o f t h e S y m p o s i u m s p o n s o r e d b y
T h e G e o l o g y D i v i s i o n o f C l M ,
a n d h e l d i n M o n t r e a l , Q u e b e c , M a y 1 O - 1 1 , 1 9 8 6
E d i t e d b y M . D a v i d , R . F r o i d e v a u x , A . J . S i n c l a i r a n d M - V a l l 6 e
T H E C A N A D I A N I N S T I T U T E
O F M I N I N G A N D M E T A L L U R G Y
135
A COTTPARATIVE STUDY OF
GMSTATISTICAL AI{D COTil/ENTIONAI, HETHODS OF
ESTTilATTNG RESER\IES AND QUhLrrrIN A THIN @AL SE,AT'T
P. J. HANNON andNova Scotia Elepartmentof Mines and Erergy
ABSTRACT
This paper gives the results of acompari-son of three methods of esti-mat ing coal reserves and qual i ty (ash,
sulphur and energy content) at the nowmined out Novaco Poi.nt Aconj. opencastmine in Cape Breton, Nova Scotia. Theaccuracy in predicting the reservesand qual i ty of the in s i tu coalresources, as wel l as the accuracy inselect ing economical ly mineable coalis compared with the tonnage andqual i ty of coal actual ly mined.
The three estimation techniquescompared were:
1rc1-ygon;inver se-di s tance- squaredweighting; andkr ig ing .
The coal reserve was f i rst est i -mated using diamond dril l hole dataavailable prior to the commencement ofmining. This study found that allestimating techniques overestimatedthe tonnage; the polygon method bY
23* | the inverse-distance-squared by
26* and kriging by only 12*.A second est imate using al l
avai lable dr i l l hole data was made,and again the three methods overesti-
nated the tonnage, this time bY 1 4t '1 1 t a n d 4 t .
The accuracy in selecting econom-
ical ly mineable coal was studied in
one area. The tonnage actually minedvtas computed f rom channe I sample s
taken during the mining cycle. This\'ras comlnred to the esti'rnated tonnagepredicted by the three methods, againusing dr i l l hole data avai lable pr ior
1985 CIM SltmPosiumOre reserve est imat i -on:methods, models and real i tY.
H. G. SHERWOODTechnical- Universityof Nova Seotia
to mining and then al l avai lable dr i l l
hole data. A11 three methods indi-
cated a reasonably close approximation
of the tota1 amount of coal available
however, the indiv idual b lock est i -
mates were superior when predicted by
the inverse-distance-squared methodand k r ig ing .
The importance of a sound geolog-
ical base is emphasized. The coal is
found in the Pennsylvanian ltorien
Group Sydney t'tain ( garbour ) Seam . At
Point Aconi, the SYdneY Main Seam is
actually two seams separated by a thin
mudstone parting. The top seam is
local ly absent, e i ther because of
erosion or non dePosi t ion. The
failure to take the discontinuousnature of the top seam into account
would lead to a considerable over-
est imat ion of the coal reserve.
RESU
136
carrd inversesla m6thode geostat ist ique dekrigeage ,
Les reserves de charbon ont 6t6premidrement estj-m6es avec l-es donneesde forage qui etaient connues avant l_ecommencement de minage. Cette dtude a/trouve que toutes les methodes ontsurestime le tonnaget la methode despolygones par 23t r . la methode chargddes distances ""rrJ" inverses par 262 |et la *6thod" de krigeage parseulement 12*"
Une seconde est imat ion, ut i l isanttoutes les donnees de forage connues,/ . / -a etd fa i te o et les t ro is mdthodes ontencore surestimds les r6"*rrre=, cettef o i s p a r 1 4 * , 1 1 * , e t 4 * .
Les estimations de qualitJ ducharbon ( cendre, soufre et contenucalorif ique) indiquent un modele sem-blable, quoique les valeurs est imds etles valeurs reels sont plus pres, avec1r exceptj-on du contenu de eendre .
Lr exact i tude de la s5lect ion ducharbon economique a 6td etudiJ dansun endroit. L€ tonnage qui a 6td min6a 6t6 evalud avec les donnees desechant i l lons en voiesn pr is en coursde minage. Un comparaison entre ceresultat et les tonnages estimds parles t ro is *6thod." a 6& fai te r €n seservant des donnees de foraEes ut i l is-able avant le minage, et de toutes lesdonndes de forage ut i l isables. Lestrois mdthodes ont toutes indiqudes unapproximation raisonnable pour letonnage, mais les est imat ions desblocs indiv iduels sont rnei l leurs avecles *6thod*s des distances carr6sinverses et du krigeagre .
Lr importance drun base gSologiquesolide est appuyd. T-,e charbon se
trouve dans le groupe Morien, de I 'AgePennsylvanian, dans la couche SydneyIr{ain (havre). A Point Aconi , lacouche Sydney t{ain est en fait deux
couches, ="p.r6s Par une mince coucheargild . L6l couche en haut n I est pas
cont inue, a cause de 1t drosion ouparce que le charbon nr a pas 6t6
depose a certains endroi ts. A\ defautde faire at tent ion a ce disposi t iondiscont inu de Ia couche sup6r ieure, unsures timation considerabLe
INTRODUCTION
The purpose of this paper is toevaluate the coal reserve estimati.ontechnique used in Nova Scotia and topresent the resul ts of a detai ledcom;rarison of estimation methods f,orthe coal reserve of the Novaco PointAconi opencast coal mine "
Novaco Point Aconi mine is nearthe western edge of the Sydney coal-f ie ldr or Boularder ie Is1and, approxi-mately 18 km northwest of Sydney, NovaScot ia ( r igure 1 ) . The coa l mined isfrom the Sydney Main (Harbour) seam,one of the mineable seams of the 2000m thick r Pennsylvanian age MorienGroup.
Between 1 9BO and ear ly 1 985,875 578 tonnes of thermal coal wereshipped from the mine to the Lingangenerating station of the Nova ScotiaPower Corporation, The weighted aver-age quality of this coal over the fiveyear per iod was 24 .75 ta l Bq (1O ,642B t u / l b " ) , 4 . ' 7 9 * s u l l p h u r a n d 1 6 . 1 1 ta s h .
The original tonnage and qualitY
estimate for the rnine was 925 300tonnes of coal grading 27 .45 MJ /kg ,5 .0 t su lphur and 1 6 .4 t ash .
The close agreement between the
estimate and the actual values is
sornewhat misleading ' The original-
overall strip ratio was estimated to
b e 1 ' l . 4 : 1 ( U 3 / t o n n e c o a l ) ; h o w e v e r ,
the ac tua l ra t io was c loser to 16 :1 .
The higher strip ratio was required to
make up for thinner than expected coal
in the original Plan dr€€l o
In August of 1 983 a discussionpaper on the applicabil ity of using
geostatistics to the Sydney coalfield
was released bY CAI{I ' iET (1). Thispaper used data from the Novaco Point
Aconi pit to obtain a kriEed maP of
the coal thickness, and suggested that
the estimation technique might be use-
ful as a rnapping aid fot the geoteeh-
nical features of the coal f ie ld. The
Nova Scotia Department of l'lines and
Energy and the Technical University of
Nova Scotia ( tmqs ) undertook a com-
parative study of reserve estirnating
methods using the Novaco Point Aconi
dr i I l ho le da ta .r5*er.r"s de charbon resulterait .des
137
F i g u r e 1 .
GEOLOGICAL FRAMEI{ORK
The Novaco point Aconi reserveoccurs in the Sydney D.tain Seam, nearthe western edge of the Sydney coalbasin. The Sydney Main Seam is one ofa dozen significant coal seams in theupper part of the pennsylvanian MorienSeries of Westphalian C and D age(2 , 3 ) . F ive k i - lometers to the west ,the Pennsylvanian is in fault contaetwith the precambrian George RiverSeries and the Cape Breton ltighlands( 2) . ttre coal section dips gently tothe northeast under the AtlantieOcean.
ttre axis of ttre Boisdale anti-eline trends northeast aeross thewestern edge of the Novaco pit, but ingeneral the structure of the propertyis very simple. fhe Morien Group is
covered by 12 to 1 5 m of surf ic ia lt i l l ln the mine area.
Hacquebard and Donaldson ( 3 )reported on the environment of coal
delnsition in the Sldney Basin andeoneluded that the eoal aecumulatedfrom forest-moor and reed-moor vegeta-tion in a f lood pl-ain environment
L E G E N D
f r - I l ' , l o r i e n S e r r e s , P t y c h o c o r p u s u n r t u s t o n e { A n l h r o c o m y o r d n e )
L l f
l q r e y s c n d s i o n e o n d s h o l e , t h r n b e d s o f l r e s h w o t e r l r m e s l o n e ,I n l e r c o l o l e d r e d b e d s , w o r k o b l e c o o l s e o m s
t , * - - l M o r e n S e r i e s , L r n o p l e I s o b l r q u o z o n € : g r e y o r k o s i c q r r t o n ds o n d s t o n e , s o m e s h o l e o n c c o n g l o m e r o l e , o f e w r e d b e d s , o l e w
w o r k o b l e c o o l s s o m s
T - l Z
- l M o r r e n S e r r e s , L o n c h o p l e r r s z o n e . g r e y c o o g l o m e r o l e , o r k o s i c
I ' *
I g r r l o n d s h o l e , o l e w r e d b 0 d s , l h r n c o o l s e o m s
charaeterized by rapid subsidence andearly burial of peat beds. There rderetwo maj or rivers traversing t-his f loodplain, along with numerous snaLl-erstreams now preserved as sandstonechannels. The coals rest on a c laybed which contain the pl-ant rootsystems" The occasional coal f ie ldtree is sti l l standing upright in thecoal bed "
Conditions were not uniformacross the Basin duringr the growth ofthe vegetat ion (3); parts of the Basinwere thriving while other areas mightbe covered with mud. The higherground was Located in the western part
of the Basin (point Aconi area), and a
eommon characteristie here is that theseams split or subdivide and event-ually pinch out.
At Point Aconi the SydneY t'tain
Sean is actually two se;rns seSnratedby a thin mudstone trnrting. lrhedeposit was eut by a river during peat
deposition as evideneed by the sand-
stone channel near the eastern edge of
the mined area ( Figure 2l . Figure 3is a cross-seetion throuEh the
deposi t . Cross-bedded sands are evi-
\9 \'r ? !r \ i \ ,
\^t i l
, ?l 6IE
\ -o\<
'r$e^
)-l{?!:? *i
r M I N E S
P o i n t A e o n i l o c a t i o n r n a p e h o w i n g t h e g e n e r a lg e o l o g y , N o v a c o o p e n c a s t m i n e a n d a d j a c e n t c o a lr n i n e o p e r a t i o n s o
dent thror.lgh much of the section,indi-cating a deltaic environment.
lftre bottorn coal horizon at PointAconi has an ari ttrrnetic average thick-ness of 0.65 m as measured from dr i l lhole samples. The top seam averages( f rom dr i l l ho le samples) 0 .43 m inthickness but is only loeal ly present,generally in the eastern part of the
mine area. Where the parting is pre-
sent, the part ing var ies f rom 0.03 m
to 1.23 rrr eyr i te is common at the
top of the coal seams and in the part-
ing " tlost of the sulphur comes f rompyrite, although some couLd come from
calcium sulphate minerals lqypsum).At the Lingan Mine, Agterberg andChung (4) found that the top 25 em of
138
F i g u r e 2 . ( W e s t h a l f )
a 2.21 m section of the Harbour Searn( Sydney iltain seam ) had 3 . 7 3* sulphur 'while the remainder of the sectioncontained 2.5*. SulPhur in the toP
sect ion was der ived from pyr i te (71t) 'organics (ZZ*) and gypsum ( 7t ) . The
loroer '! .96 m of the seam containedonly pyr i te (Sgt of total sulphur) and
o r g a n i c s u l p h u r ( 4 t t ) .
The ash content of the coal- atpoint Aconi is variable r increasingfrom the niddle of the mined area to
the east and west. N€ilr the western
edgre of the mined area the ash content
approaehes 30t, as the top seam dis-
appears through pinch out or erosi-on.
The coal- from the Sydney lltain Seam isa hiqh volati le bituminous eoal wj- th
l-oj
oorl)a
td
oOorf)
UJOorf)rf
lrJ
ooo(f,
LJ
ooFro
2 500
2000 N
t 5 0 0 N
L39
oo(I)l"*
IJ
oorOf-
LrJ
oooft*
IJ
oOtO(o
Ld
ooo(o
Areo l ex ten t o f top seom
o 200 400l t t t . _ l
met res
F i g u r e 2 .
hiqh ash and hiqh sulphur, accordingto the AST!{ (5) c lassi f icat ion ofc o a L s .
I.{ININc
Itre topsoil and till were removedusing Caterpillar 627r_ tandem-poweredwheel tractor scrapers, except nearthe edge of the pit rv?rere Cat D-10dozers removed the overburden. l-tiningbegan with a down dip box-cut at theeastern edge of the property, thenmining progressed using along-strikestrips. fhe rock above ttre coal wasl iqh t ly b las ted to w i th in 0 .25 m o fthe top of the coal, using ANFO loadedinto 250 mm dianneter holes dr i l led on
2500 N
2000 N
I 5 O O N
a 5 m by 6.'l m trnttern. A Powderfactor of approximately O.2 kq AHrO/m3was used.
The rock was then removed using aBueyrus-Erie Model- 38O W walking drag-line . The dragline rernoved the rock
to within about A"2 m of the toP ofthe coal. The remaining rock was
cleared using a small dozer " {the coalwas then mined using a Caterpil lar 235excavator, )-oading into 10 t tandem-wheeled dunp trucks. The eoal \tas
taken to the on-site plant where it
$ras crushed and stacked for transport
to the Nova Scotia Power Corporationgenerat inq stat ion at L inqan.
POINIT ACONI OPEN CASTCOAL M INE
( NOVACO LIM IT ED )N T S I I . K - 8 A p r i l 1 9 8 5
T h e o u t l i n e o f t h e r m i n e d o u t a r e a s o f t h e N o v a c op i t , d r i 1 1 h o l e l o c a t i o n s a n d t o p o g r a p h i c a lf , e a t u r € s .
S C O T I A D E P A R T M E N TM I N E S A N D E N E R G Y
F i g u r e 3 .
140
A g r i d s o u t h - n o r t h rt h r o u g h t h e e a s t e r n
c r o s s s e c t i o n ( l o o k i n g w e s t )p o r t i o n o f t h e N o v a c o p i t "
AVAILABLE DATA
The or ig inal reserve est imat ionfor Novaco used information from threesets of dr i l l - hol-e data.
The Department of l l ines dri l led aser ies (5 ho les , D-Ser ies) o f ho les inthe area duri.ng the 1 960' s . A seconds e r i e s o f h o l e s ( t S h o l e s , R - S e r i e s )was dr i l led in 197 4, and the thi rdser ies o f 15 ho les was dr i l led and q
test p i ts were dug in 1979 and 1980.On1-y the holes dri l led after 1979 r"eregeophysieally 1-ogged. The averagecore recovery in the coal section rdasin the order of 80*. A further 28diamond dri 11 hoLes were dri l led i-n
1 980 and 1 981 and, in addi t ion, rotaryholes vrere dri lled through the coalprior to each blast to test for thetop of ttre coal horizon. Table 1summarizes the dril l hole data avail-able for ttre reserve estimates. The
data available for the reserve esti-nate i.s certainLy l-ess than ideal; notan uncommon situation in the miningindustryt
COAL RESERVE ESTII.{ATION PRESENTLY USEDIN NOVA SCOTIA
The Department of lt{ines and
Energy presently uses the polygonmethod to esti-mate coal reserves r Themaximum distance between obeervation
points conforms to the Classj- f icat ionfor Coal- Resources and Reserves ofCanada ( 6) . ttt is maxirnum distaneedepends upon the eharacteristics ofthe seam being evaluated: the thj-ck-ness of the se€un, the resource cate-gory, and whether or not the seam ison shore. Por the Sydney Main Seam,this distance is a maximum of 800 mfor the measured cateEoryo and 1 600 mfor the indieated category of resourcec lass i f i ca t ion .
For the point Aconi deposie, theaverage dril l- hole spaei-ng at the time
of the init ial reserve calcul-ation was
117 m; however, the range of d istancebetween drill holes ltas f,ron 50 rn to
over 600 rr o Even so r all of the coalvras elassed i.n the measured category.
COMPARJATIVE STUDY OF RESERVE ESTI},IATES
the comparison studY estirnated
the eoal reserve and qual-ity in the
area actmalLy mined, using ttre origi-nal diannond dril l data for sulphur,
ash, energy content and eoal thiekness( table 1 ) . ttre methods used \,tere the
lnlygon method, the inverse distance
squared met t rod ( r .D"s . ) , and the k r ig -
ing rnethod of geostatisties. Table 2
summarizes the results of the esti-
mates using the dr i lL hole informat ion
availabLe prior to production, and the
est imates using al-1 avai labl-e dr i l -1
[FEl overburden
tr-:1 shole
" E C s h o t e o n d s o n d s t o n e
hIl sir tsrone
IFJ ,onostone
iff=-'*#'. . : ._.\----+,':ii:Itn:: ji:ir, .,: j:L,.ti ji j j';..
iir':.i:#-I = ' l ' t oo i r i c i i on
:
illr-...ji.--]fl' **..ti. .1.,:j j,t i: i ir,.. i ;i.it:.., r a..----TF
7.2o/o Ash
4 37o S3 2 6 3 M J , / k gr!1: i . : : : . . : : : . : . : . r : : . : . j :1i : I :-F.!
:1: i :r : : : t1 : i : i i : : : , :rr j i rr j r : j j i
, j . : , : : : ; : i : . . . . : . . . . . ,. : . : . ' r i r i . . . . . : . ' . . . . . . . . ' -
N o v o S c o l i o D e o o r l m e n f o f M i n e s o n d EI : i l : J j j . :' ' . . r : .
m e l r e s
too
N o v o c o P o i n l A c o n i O p e n c o s t
C o o l M i n e
G E O L O G I C A L C R O S S - S E C T I O N
P . H o n n o n
L4L
. r o o
.o75
t r r n l.o50
.o2
.oo238
t r tn to.o2
o.o l
F i g u r e 4 .
C O A L T H I C K N E S ST O P S E A M
F I R S T H O L E S
294 44?
h ( m )
C O A L T H . I C K N E S ST O P S E A MA L L H O L E S
C O A L T H I C K N E S S
L O W E R S E A MFIRST HOLES
274 4 tO 347 684h ( m )
C O A L T H I C K N E S S
L O W E R S E A MA L L H O L E S
t47
t 3 7
I ( h )
C O A L E N E R G Y
tr(
30.
20.ooh )
t37 274 412 549
h ( m )
o.05
o.o4
o.o3
5 . O O
4 . O O
300
T t n t2.OO
l.oo
C O A L S U L P H U R
189 284 379 471 l s r z t ' + q tc '
h ( m ) h ( m )
S e m i v a r i o g r a m n o d e l s b a s e d o n t h e d r i l L h o l e d a t a
a v a i l a b l e p r i o r t o t h e p r o d u e t i o n d e e i s i o n ( f i r s t
h o l e s ) a n d o n a l l a v a i l a b l e d r i 1 1 h o l e d a t a . T h e
s e m i v a r l o g r a n s f o r a s h , e n e r g y a n d s u l p h u r a r e
b a s e d o n t h e f i r s t d r i l l h o l e s o n l y . T h e l a t e r
h o l e s w e r e n o t a s s a y e d f o r t h e e e v a r i a b l e s .
h ( m )
r37 274 412 549 686
h ( m )
r42
TABLE 1ST'UI{ARY OF NOVACO POINT ACONI OPENCAST I'IINE DRILL }IOLf, SAHPLE DATA
- - * N o t p r e s e n t
N A * i N o t a s s a Y e d
H o l e
N u n b e r
S e a m r h i ? k n e s s ( m ) .T o p I B o t t o m
I
A s h( r )
s u l p h u r( t )
E n e r g Y( l . { J / K s )
D 2 3D 2 4D 2 5D 2 6D 2 7R - 1R - 1 8R - 1 8R - 1 CR - 2R - 2 BR - 2 BR - 3R - 3R - 3 8R - 4R - 4 8R - 4 8R - 4 CR - 5R - 5R - 5 8R - 5 8R - 6R - 7R - 8R - 9 F1 - 7 9' t - 7 9
2 - 7 92 - " 1 93 - 7 94 - 7 94 - 7 95 - 7 96 - 7 97 - 7 97 - 7 9B - ' t 99 - 7 9
1 0 - 7 95 - B 06 - 8 07 - 8 08 - 8 0
1 0 - 8 01 - 8 12 - 8 13 - 8 14 - 8 15 - 8 16 - 8 17 - 8 18 - 8 19 - 8 1
1 0 - 8 11 1 - 8 1l 2 - 8 1
1 - 8 1 42 - 8 1 A3 - 8 1 44 - 8 1 A5 - 8 1 A6 - 8 1 Ag - 8 1 A9 - 8 1 4
1 O - T A' l t -TA
1 2 - T A
1 4 - T A1 5 - T A1 6 - T A1 7 - T A
_ _ r I 0 . 7 3
| 0 . 5 6
| 0 . 4 1
| 0 " 4 8I o . z a
o . 5 8 | o , s so . 6 7 |
I o . s sI o . 8 0
o . G 4 | o . r zo . G s I
I o . e zo . s 2 I
| 0 . 7 30 . 1 e I o . 2 4
| 0 . 7 e0 . 8 6 |
| 1 . 1 so . 1 6 | 0 . 9 5o . 2 7 I
I o . 2 2o . 3 4 |
I 0 . 6 7
I o . e rI o . s s
o . s 2 | o . : r| 0 . 4 3
o . 4 3 |I 0 . 5 4
0 . 2 8 |
0 " 3 6
o . a 20 . 5 8
I o . e tI o . r zI o . s s
0 . 6 1 || 0 . 7 3
I o . z oo . 2 4 | o . 7 e
| 0 . 7 0| 1 . 2 6
o . s o I o . e ao . 4 s I o . e so . 4 6 | O . 6 5
I r . z ao . 4 s I o . 6 0o . 4 s I o . e oo . 5 0 | o . 6 so . 4 0 | o . 5 0o . 4 s I o . s z0 . 3 s I 0 . 6 3o . 4 8 I 0 . 6 0
| 0 . s e
I o . s zI o . 7 oI o . z oI o . e z
o . 4 o I o . 6 so , 3 s I o . e so . 3 1 | o . z s
I o " z rI o . s 4I o . z s| 0 . 6 2I o . 8 1
I o . e sI 0 . 6 2
I o - z sI o . z oI o . e rI o . o aI 0 . 5 9
9 . 4 29 . 1 49 . 5 8
1 0 . 59 . 8 2
1 5 . O' | 1 . 2 0
8 . 9 06 . 4 07 . O O
1 5 . 98 . 4 0
1 8 . O6 . 8 0
4 5 . 5 07 . . 2
2 0 . 48 . 5 0
r 3 . 1 91 0 . 82 1 . A
5 . 91 0 . 3
9 " 1 01 1 . 71 6 . 5N A1 4 . 3
7 " 6 01 0 . 61 0 . 4
9 . 1 09 . 4 04 . 1 0
N A1 0 . 32 3 . 42 s . 21 5 . 9N AN AN AN AN AN AN AN AN AN AN AN AN AN AN AN AN AN AN AN AN AN AN AN AN AN AN AN AN A
N AN AN AN AN A
6 . 1 5 I N A * *4 . s 8 I 2 2 . 0 87 . A A I 2 2 . 0 86 . 6 o I z z . o e5 . 3 6 I 2 2 . 0 82 . 2 0 | 2 2 . 0 85 . 5 0 | 2 e . 1 s3 . 8 0 | 2 2 . o o3 , 7 o I r o " z s3 . 6 0 | 3 1 . 4 46 . e o I z o " r r3 . 5 0 | 2 9 . 1 95 . 4 0 | z t . t z3 . 3 0 | a o . e ze . 3 0 | e . r r4 . 3 0 | : z . e r
1 1 . 0 | z a . t e4 . 4 0 | : r . o o4 . 5 2 | z a . t s5 . 3 0 | 3 0 . 2 e4 . 4 0 | 2 6 . 5 ' 74 . 2 0 | 3 0 . 9 o3 . e o I z a . z os . 1 o I z s . s t6 . 2 o I 2 e . 1 39 . 0 0 | 2 8 . . 2 1N A I * o7 . 6 7 I - -4 . 1 8 |
- -7 . 9 0 | 2 e . 2 64 . 2 0 | 2 s . a 74 . 7 3 | 2 9 . 0 8G . 3 8 | z a . z e1 . 4 8 | 3 0 . 5 8N A l " o5 . 8 4 | 2 8 . 2 3B . T B I8 . 7 0 | 2 2 . e 66 . 8 6 | 2 7 . 3 1N A I * oN A l " oN A I N A
N A I * oN A I N A
N A l " oN A I N A
N A I * oN A l n nN A l n aN A I * oN A I N A
N A l " oN A l n oN A I N AN A I N AN A l n oN A I N AN A I N AN A I N AN A I N nN A l x eN A l n oN A I N AN A I N AN A l n nN A l n oN A I N AN A I N A
N AN AN AN AN A
N AN AN AN AN A
IIIIII
II
IIIII
I
tIII
II
IIIIII
II
III
III
I
L43
T A B L E 2C O M P A R I S O N O F C O A L E S T I M A T I O N M E T H O D S
N O V A C O P O I N T A C O N I D E P O S I T
l 4 e t h o d
U s i n g t h e
P o I y g o n sr . D . s .r r i g i n gA c t u a I
P o I y g o n s
I . D . S .x r i g i n gA c t u a I
P o I y g o n s
I . D . S .K r i g i n g
P o I y g o n s
r . D . s .K r i g i n g
2 5 . 5 52 5 . 9 82 5 . 9 12 4 . 7 5
2 3 . 9 42 5 . 9 12 5 . 8 92 4 . 7 5
5 . 5 04 . 5 05 . 1 94 . 7 9
T A B L E 3S T A N D A R D T Z E D D I F F E R E N C E
( E s t i n a t e d - A c t u a l x 1 0 0 )w
+
+
+++
1 5 . 9 05 . 0 58 . 3 5
2 . 3 03 . 3 48 . 1 4
+ 3 . 2 3+ 4 . 9 7+ 4 . 6 9
- 3 . 2 7+ 4 . 6 9+ 4 . 6 1
T o n n a g e( t o n n e s )
F i r s t 3 5 H o l e s
E n e r g y( M J / K q
U s i n g A 1 1 H o l e s
t ' le thod
F i r s t H o l e s
E n e r g Y( M J I K 9 )
A l t H o l e s
144
hole data. l fhre in s i tu coaL reservesand quality were estimated, then anest imated di lut ion of 5t was added.( fhis seems a reasonable amount ofdi lut ion, a l though the possibi l i tyexists that trecovery riras actually l-essthan 1 00t. There are no records ofthe actual d i lut ion. ) Since thedilution contributes to the sulphurand ash content, these were adj ustedupward 5* . The di l-ution would sub-tract f rom the energy content, so th iswas adj usted dovrrward St.
The areal extent of the discon-tinuous top seam rras p1-otted on a plani l&pr using informat ion avai lable af terthe first 35 holes and then replottedus ing a l l d r i l l ho le in fo rmat ion es t i -mated. 'Itre southern boundary of theseam ls the trace of the subcrop,while the northern boundary is the toeof the highwall-.
POLYGON }IETHOD
Tonnage and coa I qua l ity \rereestimated by weighting the centralsample value by the area of a polyEonconstructed around the central sarnpleand extendinE this half way to adj a-cent sample sites " Only that portionof the polygon coincident with thearea actually mined hras used. Thetonnage was estimated first and thenthe coaL quality \,ras determined byweighting the sample value by thetonnage. Ar r S .G" o f 1 .34 was used fo r
al l est imat ion methods"
I}WERSE DISTANCE METHOD
Blocks 1 OO m bY 1 0O m were used
with this nethod, in a manner sirnilar
to that described by Ot Brian and Weiss( ?) . Each value was estimated for a
block by considering al-l- samples with-
in a 400 m radius of the centre of the
block.
KR.IGING
For the krigi-ng estimation, seni-variograms of ttre coal- thickness, ash,
sulphur and energy were constructedusing the method of, angul"ar regulari-zation ( I ) and the method of nectang-
ul-ar regul-ar i -zat ions (9), The semj--varioEram data for the coal thi-ckness,ash, sulphur and energy content aretabulated in Table 4. Due to theirreEular sarnple data, the experi-mental semi-vaniograms displ-ay a ver l rerrat ic var iance, The data base for agood reserve est imat ion is certainl-ynon- ideaI, and at f i rst g1-ance ageostati-stical study would seem to trea fut i le exerc ise. Figure 4i l lustrates the exper imental and
theoretical variogr€lrns rThe experimental senni-vari-ograms
for the seam thi-ckness, parti-cularl-ythe semi-va.riogrram of the top seam,f i rs t ho leso su f fe rs f rom a laek o fclose spaeed samples. One way toovercome this lack of sample datamight be to assign values to thesample grid baeed on a geo}ogicalevaluation of the locati-on. Hovtever,it was decided to make do with theactual sampLe informatj-on avaj-lable.
The theoretical variogrrarn wasfound by CANI4AT program 227 5 ( 9 ) 'which searches for the semi-variogrammodel which has the best f, it with the
experimental semi-variogramr by l inearregression anal-ysis. The rel-at iveerror between the estimated andobserved values for the models aretabulated, with the best theoreticalsemi-variogrram curve having the best
f i t wi th the exper imental data,The experimental semi-vari-ograms
for sulphur, ash and energy were
construeted using these vaLues rather
than the value tirnes the seam
thickness. Actually both nethods were
tried and since ttre aecumulation did
not improve the quality of the output'
the simple value was used "
The kriging estirnation was com-
p!.eted by subdividing the deposit into
seven areas, then estimating the
seleeted vari.able in each dr€E r
Each area was in turn subdivided
into 15 sub-areas; ttre rnidpoints of
these sub-areas were used to cal-eulate
the covariance between the sample area
being evaluated "
SFLECTTON OF MINEABLE COAL
One area, bounded bY east ing 61 00
L45
T A B T E 4T H E O R E T I C A L V A R I O G R A M S U S E D F O R K R I G T N G
F i r s t 3 5 H o l e s
C o a l T h i c k n e s s , T o p S e a n , S p h e r i c a l M o d e l
v0 ( h ) = 0 . 0 2 6 + 0 . 0 1 5 ( g
z
C o a l T h i c k n e s s , L o v r e r s e a m r S p h e r i c a l M o d e l
U t r t l = 0 . 0 3 6 + o . o 2 B ( 3 ( h ) . - 1 ( h ) 3 )2 2 6 2 2 2 6 2
howevern most blocks had 7 or 8. Theresul ts of th is conpar ison are tabu-lated in Table 5.
The top seam is discontinuousover of the study area. This $rasapparent af ter the f i rst 35 holes andwas taken into aeeount for the esti-mation of the coal tonnagre.
Both the I nD. S. and kr ig ingrnethods were an improvement over thepcllygon method of estimating tonnage nThe overall results of each methodwere fairly good, although the polygonmethod did ser i -ous1y overest imate thetonnage of block 2-8, 9 and 1 0 andseriously underestimate the tonnage inb l o c k 2 r 6 . T h e I . f ) . S . a n d k r i g i n gmethods gave reasonable estimatesttrroughout the mined area.
DTSEUSSION OF RESTILTS
llhe results of the comparisonstudy appear reasonable with theexcept ion of the est imate of ash. Al lestimating methods indicated a lowerash eoal, with a higher sulphur con-tent.
this may be due to the inelusionof part ing mater ia l as di lut ion andthe removal of some of the sulphurrich coal at the top of the seam.
Both the I .D.S. and kr ig ing are animprovement over the polygon method,although the polygon method did give aclose approximation of the actualtonnage and quality v*ren all dri lLholes were considered.
The polygon method has theadvantage of simplicity; a reasonableballpark estimate can be produced inan afternoon. The method has numerousdisadvantages, the most serious beingthe faet that the entire polygon isestimated by one eentral- sample,ignoring the relationship betweensamples.
The inverse distance squared-moving average method does takeadjacent samples into considerat ion;the weighting can be adj usted byshrinking or exlnnding the radius ofthe c i rc le used for est imat ion. Thegeology and sample var iabi l i ty t rendmay be taken into aecount by using anel l ipt ical search area, wi th the
( h - ) - 1 ( h ) 3 )
2 7 8 2 2 7 A
3.ll-*[gl-
C o a l T h i c k n e s s , T o p S e a m ,
- f
I t t r l = 0 . 0 1 3 + 0 . 0 2 1 ( 3 ( h ) - 1l 2 e z t
C o a l T h i c k n e s s , L o \ , r e r S e a n , S p h e r i c a l M o d e l
S t n l = 0 " 0 2 8 + o . o o s ( 3 ( h ) - 12 4 7 4 2
S p h e r i c a l M o d e l
S u l p h u r , S p h e r i c a l l ' { o d e l
I t r t l = o . o o o + 2 . 6 4 ( 3 (2
A s h , S P h e r i c a l M o d e t
f , n 1 = o . o o o + 1 G - 4 9 ( 32
E n e r g y , S p h e r i e a l M o d e l
( h ) 3 )2 m
( h ) 3 )4 7 4
( h ) - 1 ( h ) 3 )
5 1 9 2 5 1 9
h )
3 6 0
- 1 ( h ) 3 )2 3 6 0
J[ t r , l = 1 5 . 6 0 + 3 . 4 1 2 ( 3 ( h ) - 1 ( h ) 3 )
2 5 1 . 2 2 5 ' 1 . 2
and 5700 and northing 1 8OO and 2O5O,was chosen to determine the accuraeywith which the estimation methodscouLd select mineable coal .
The area was subdivided into 20b locksr 350 m by 25 m ( f igure 5) . thetonnage of coal in each block was est-imated by the three methods and thencompared to the tonnage of each bLoekas determined from channel samplesobtained dur ing the mining cycle.
fn this ease, the polygon esti-mate was made by determininq theLength of the rnid-trnint line in eachbLock that c€lme under the inf luence ofthe drilI polygons. The length ofthis l ine was rnultiplied by thethickness assigned to the dr i l lpolygon and then the block was assign-ed the weighted average thiekness.
A total of 172 channelsamples were avai labl_e . The numberper mining bl-ock var ied f rom 4 to 1 5,
146
T A B L E
A C C U R A C Y I N S E L E C T I O N M I N E A B L E C O A L5O F
l-onEest ray in the di-rectj"on ofgreatest continuity. The eomputerprograaminq is fairly sirnple and theoutput is straiEhtforwarrl. The dis-advantage of the I " D* S * method isthat it does not take the saiuPlevariabi l i ty of the dePosit j -nto
account j-n any r igorous wd1l r The
Eeological trerrc{s are smoothed overand very l - i t t le informat ion is Eainedfrom the analYsis of the outPut "Areas of non delrcsitiorr. atre gi-ven the
average val-ue of the sampl-es within
the search cirele. When there arecLusters of samP1es, the cLusterweight tends to dominate the estirnate
within the search ci-rc le.The krigi-ng method does give the
best l inear unbiased estimate of, a
reEionatr ized var iable (8) whene there
is no signi f icant t rend to the data"
Universal kriging can be used if there
is a s ign i f iean t t rend.The use of qeostat ist ies is
l imited more by the skil l of the user
than by the method itself* The selec-
tion of the theoretical semivariogram
used to krige the variable, boundary
of the deposi t , search area si-ze and
selection of kriging rnethod all-
require ski l" ls that are acquired only
through practice. The software
systems no\c avail-able are of, coneider-
able help, but even these Progransrequire a much higher degree of skil l
than does a simple polygon estimate.
tdeally, there should be a good grid
of sample data so that a variogram
analysis can be conPleted and, of
course, aecess to good software and
reasonabl-e cornputing facil i t ies i-s
essent ia l .The extra effort and higher
degree of skil-I required to do a Eeo-
statistieal studY of a dePosit are
more than offset by the output gener-
ated by such a study" The variograms
generated by this particular study
indieate the discontinuous nature of
the coal in the top seam n and also
indicate that a regular grid wi-th
drilt holes spaced about 1 50 m apart
would have been more appropriate than
the haphazard driLl- spaeing upon whieh
the investment decision was xnade. The
estimate of the tonnage, ete. 7 show"n
T o n n e s
E s t i n a t e dF r o m
t o n n e s ( f i r s t h o l e s )
t o n n e s ( a 1 1 h o l e s )
P a n e I C h a n n e I
S a m p l e t o n n e sP o I y g o n I . D . S . x r i g i n g
1 r 1 5 0 0 6 0 06 0 0
z o q6 0 0
7 0 05 5 0
1 ' 2 4 1 0 0 3 9 0 03 6 5 0
4 5 5 04 6 5 0
5 3 0 0aeSo
1 t 3 7 1 0 0 6 8 0 06 6 o o
7 7 A A7 4 0 0
8 4 0 07 5 0 0
1 r 4 9 6 0 0 8 0 0 0666'o
8 8 0 08 4 o O
9 5 0 08 6 0 0
1 , 5 1 0 1 0 0 9 6 0 09 0 5 0
9 3 5 08 5 5 0
9 0 0 08 6 0 0
1 , 5 9 9 0 0 7 4 0 0E6'6'o
9 2 5 08 3 5 0
8 3 0 08 3 5 0
1 r 7 8 0 5 0 _e4qo8 5 0 0
8 4 5 07 4 5 0
7 4 0 06 B O O
1 t 8 7 5 5 0 e_?008 9 0 0
8 1 0 0tToo
68o j6 8 0 0
1 , 9 7 3 0 0 87o j l7 3 0 0
7 4 5 06 8 0 0
64 .006 2 0 0
1 , 1 0 4 1 5 0 4 5 0 0 .4 4 0 0
3 8 5 03 4 0 0
3 6 0 0346'0
2 , 1
2 t 2
2 , 3
6 5 0 4 6 02 5 0
5 5 05 5 0
8 0 07 0 0
5 3 0 04 B O O
4 5 0 0 2 5 0 02 5 0 0
4 0 5 03 9 5 0
2 , 4 5 4 0 0 3 1 0 03 1 0 0
4 9 0 04 8 5 0
6 1 0 05 7 5 0
2 , 5 6 7 5 0 3 8 0 03 8 0 0
6 3 5 06 3 0 0
72596 9 5 0
1 3 0 0 01 3 0 0 0
2 r 5 1 3 4 0 0 6 9 0 06t6'6'
1 2 9 p 01 2 0 0 0
2 t 7
2 , I
L t
6 8 0 0 9 2 0 07 4 0 0
6 7 0 06 1 0 0
6 2 5 06 3 0 0
7 3 0 0 1 1 2 0 q9 0 0 0
8 0 5 07 1 0 0
6 9 5 06 7 5 0
6 9 0 0 1 2 5 0 07 9 0 0
8 3 0 07 1 0 0
7 0 5 0 .7 1 5 0
2 , 1 O 5 4 0 0 1 2 0 0 0- 6 2 0 0 8 0 5 06t5o'
6 8 0 06 8 o o
T O T A L 1 2 6 4 5 0 1 2 9 6 6 0
1 1 3 9 0 0
1 2 4 9 0 01 2 o T 5 o
L47
T A B L E 5A C C U R A C Y I N S E L E C T I O N O F M I N E A B I , E C O A L
T o n n e sE s t i r n a t e d
F r o m
t o n n e s ( f i r s t h o l e s )Tfi ' i l ; ; ( al"t holes )
P a n e I C h a n n e IS a n p L e t o n n e s
p o I y g o n I . D . s , x r i g i n g
1 r 1 5 0 0 6 0 06 0 0
7 q o6 0 0
7 0 06 5 0
1 t 2 4 1 0 0 3 9 0 03 6 5 0
4 5 5 04 5 5 0
5 3 0 0a5"5 0
1 , 3 7 1 0 0 5 8 0 06 6 0 0
7 7 0 07 4 0 0
8 4 0 07 6 0 0
1 ' 4 9 5 0 0 8 0 0 06 'bso
8 8 0 08 4 0 0
9 5 0 08 6 0 0
1 , 5 1 0 1 0 0 _ 9 6 0 09 0 5 0
9 3 5 08 5 5 0
9 0 0 08 5 0 0
l r 6 9 9 0 0 7 4 0 05'eoo
9 2 5 , 08 3 5 0
8 3 0 0 .8 3 5 0
1 r 7
1 , I
8 0 5 0 9 4 0 08 6 0 0
8 4 s 0T?so
7 4 0 06-8O O
7 5 5 0 e2q_08 9 0 0
8 1 0 07 1 0 0
5 8 0 06 8 0 0
1 1 9 7 3 0 0 87 0j7 3 0 0
7 450.6 8 0 0
6 4 0 06 2 0 0
1 r 1 o 4 1 5 0 4 5 0 04 4 0 0
3 8 5 03 4 0 0
3 5 0 03 4 0 0
2 t 1
2 t 2 6 5 0 260-2 5 0
5 5 05 5 0
8 0 q7 0 0
2 ' 3 4 5 0 0 2 5 0 0t s o o
4 0 5 03 9 5 0
5 3 0 04 8 0 0
2 t 4 5 4 0 0 1_1oo3 1 0 0
4 9 0 04 8 5 0
6 1 0 05 7 5 0
2 t 5 6 7 5 0 ? 8 0 03 8 0 0
6 3 5 06 3 0 0
7 2506 9 5 0
1 3 0 0 01 3 oo5'
2 t 6 1 3 4 0 0 6 9 0 06 9 0 0
1 2 6 5 01 2 0 0 0
2 t 7 6 8 0 0 e 2o97 4 0 0
6 7 0 06 r O O
6 2 5 06 3 0 0
2 , I 7 3 0 0 1 1 2 0 0-T60o -s.q197 1 0 0
6 9 s O6 7 5 0
2 t 9 5 9 0 0 1 2 6 0 07 9 0 0
8 _ 3 0 07 1 0 0
7 0 5 . O7 1 5 0
2 t l O 6 4 0 0 1 -2ooo6 2 0 0
8 0 5 06 ? 5 0
6 8 0 06 8 0 0
T O T A L I 2 6 { 5 0 1 2 9 5 6 0t 1 3 9 0 0
1 27-9,001 1 7 5 0 0
1 2 4 9 0 01 2 0 1 5 0
Th is i s a repe t i t i on o f Tab le 5 .
lrl
o9@
148
2200 N
2 too N
2000 N
t 9 0 0 N
1800 N
t 7 0 0 N
T h i s f i g u r e s h o w s t l r " a r e a o f t h e d e p o s i t u s e d t od e t e r m i n e t h e a e c u r a c y w i t h w h i c h t h e e s t i m a t i o nm e t h o d s m i g h t s e L e c t m i n e a b l e c o a l . T h e s h a d e da r e a i n d i c a t e s t h e p r e s e n e e o f t h e t o p s e a m .
tll
oo@
lrj
C)o(\I
@
t!
o
t -(o
lrj
o(o(o
trJ
ooro
trloo<r(o
IJ
ootf)(o
F i g u r e 5 .
in Table Z are the most J- ikeLyvalues. A mining company might demanda higher confidence linit for thesevalues pr ior to invest ing mi l l ions ofdollars in the _ venture. For thisparticular study, the company couldhave been 97.5t assured of at least
593 000 tonnes af ter the f i rst 35holes had been dr i l led.
The importance of a good sampledata base must be emphasized. Aecur-ate analyses and measurements must beobtained whenever possible. Ttris ispartieularly true of low grade, low
tonnage deposits where the difference
of 1 0 or 20 cm in thickness of the
deposit might mean the difference
between prof i t and loss.In order to do a proper reserve
estimate, the deposit should besampled on a regular grid. Th€ dril lholes in the eoal horizon must be geo-physical ly logged and al l er i t ieal
analyses completed. Geological inter-pretation must be incorporated intoal l tonnage est imates, in part ieular
when computer based estimation tech-n iques sueh as the r .D .S. and k r ig ingest imates are used.
EONCLUSIONS
The estimate of coal quantity andquality at the Novaco Point Aconideposit has been cornpleted using thepolygon method, the I .D.S. movingaverage method and the kriging method
of geostat ist ics. Each method has
certain advantages and disadvantages.
The geostati stical rnethod gave the
best estinate of the overall tonnage
and €r€f ! [ ] r Both I .D.S. and the kr ig-
ing methods gave a reasonable estimate
of mineable coal in seleeted blocks.
It has been shown that each .method
relies on a grood geologrical data
base. fhis data base should include
all obtainable data and should r ds
near as possible, be on a regular
sampl ing gr id.
I49
ACKNOWLEDG14ENTS
The authors wish to thank theDepartment of hergy, Mines andResources for funding this projectunder Research Agreement Number 222,and Novaco Ltd. for permission topubl ish the resul- ts of th is study.
REFERENCES
1 ASTON, T .R.C. , D . l lacNEr l , andC. WHITE, 1983r The App l ica t ion o fGeostat ist ics to the SydneyCoalf ie ld: CANMET Discussion Paper,EMR, Ottawa
2 BELL 7 W. A. 7 1 983 , Bras d I Or Sheet,Cape Breton and Victoria Counties,Nova Scot ia : G.S.C. Map 359A
3 HACA-I 'EBARD, F.A. and J.R.DONALDSON, 1 969, Carboniferous CoalDeposition Associated with FloodPlain and Limnic Environments inNova Scot ia ! G.S.A. Spec ia l Paper114 t Errv i ronments of CoalDeposi t ion r pp 1 43-1 91
4 AGTERBERG, F.P. and C.F. CHUNG,1973, Geomathematieal Predict ion ofSulphur in Coal r New Lingan MineArea, Sydney Coalf ie ld: CIt{Bul- let in , Oet. 1973
5 American Society for Tresting andMater ia ls, 1 978, Book of ASTMStandards, part 26, Phi ladelphia
5 BIELENSTEINT H 'V ' ; L 'P ' CHRISMAS,B.A. TATOUR and T.E. TIBBETTS,'|.979, Coal Resources and Reservesof Canada: CANMET, E!lR, ottawa
7 O T B R T A N 2 D . T . A N D A . W E r S S ' 1 9 6 8 'Practical Aspects of CornputerMethods in Ore Reserve Analysis:c I M S p e c i a l r V o l 9 t p p 1 0 9 - 1 1 3
8 DAVID, M. 1977, Geostat ist ical- OreReserve Est imat ion: Elsevier,Am s terd am
9 SABOURTN, R.L. r 1982, CANMETSystem for lt l ineral ReserveErraluation: CANI,IET llining ResearchLaboratories, EMR, Ottawa
![Untitled-3 [] Details/UNFC Reserve Statement.pdfGeneral statement on mineral resource and Ore reserve estimation and reporting ... and when an analogy with known deposits 01 similar](https://static.fdocuments.us/doc/165x107/5e994f7cbbe5b11a504a30e2/untitled-3-detailsunfc-reserve-general-statement-on-mineral-resource-and-ore.jpg)
