Merit Pila Coal Basin, Malaysia – Geology and Coal Petrology

P. Osvald1), I. Sýkorová2)

1) PT Transasia Resources, Plaza Mutiara Lt 18 Suite 1802, Jln. Lingkar Mega Kuningan12950 Jakarta, Indonesia

2) Institute of Rock Structure and Mechanics AS CR, V Holešovičkách 41, 182 09 Prague, Czech Republic

Geological aspects and character of sedimentary setting relation of coal seams in Miocene Merit Pila Basin, based on geological exploration, stratigraphy and structural development of deposit supported by rank, petrographical and chemical composition of coal.

The proven reserves about 170.3 Mt were identified.Coal is used in Sejingkat Power Corporation power plant at Kuching.

Fig. 1 Geological map of the Merit Pila basin (after GPS)

Fig. 2 Cafter Kirk 1957, Wolfenden 1960, modified by Osvald 2006

Stratigraphy of the Merit Pila Basin (Liaw 1987; Dorani 1990)

Recent geological exploration and studies indicate gentle structural unconformity in Merit Pila Basin.

The Lower Sandstone and the Upper Coal Zone dip to the south under 15 – 17 degrees and overlaying unites dips under 8 – 12 degrees. This indicates syn-sedimentary subsidence.

The unconformity is developed in whole basin extend but for area in the vicinity of the Boundary Fault at southern boundary of the basin, because complicated fold structure induced by movement along theBoundary Fault prevents observation of unconformity

Unit Thickness (m) Description Upper Sandstone 100 - 200 Sandstone and shale claystone Upper Coal Zone 150 - 200 Sandstone and claystone, 4 – 5 coal seams Middle Shale-Sandstone

100 - 150 Sandstone, claystone and shale claystone, irregullar coal lenses

Lower Coal Zone 200 - 300 Sandstone and claystone, conglomerate to 10 m, 18 coal seams

Lower Sandstone 100 - 150 10 – 20 m basal sandstone, conglomerate

Geological Map of Merit Part of the Merit Pila Coalfield

Stratigraphy of the Lower Coal ZoneLower Coal Zone

Description Seams

Sub -Unit 5 Changes of claystone and siltstone Thickness: Merit part 5-44m, Tebulan part 5-65m

G,Gx, H, I1, I2, J-Merit K-Beradai G, H, I1 - Tebulan

Sub -Unit 4 Claystone – conglomerate – sandstone Thickness: Merit part 27-44m, Tebulan part 43-63m

E, Ex, F, Fx

Sub -Unit 3 Claystone (sandstone) Thickness: Merit part 47-59m, Tebulan part 59-72m Beradai (bore LYBD02-03)

C, D, Dx C

Sub -Unit 2 Sandstone Thickness: Merit part 26-57m, Tebulan part 44-68m

Bx

Sub -Unit 1 Base of LCZ, claystone, shale claystone Thickness: Merit part 34-48m, Tebulan part 50-61m

A1, A2, B1, B2

Stratigraphy of the Upper Coal Zone (Liawa 1995)

Stratigraphy of the Upper Coal Zone (Ward 1978)

Description Seams Lower Coal Zone Sandstone, shale claystone , claystone μA1, μA2, μB, μC1, μC2,

μD, μE1, μE2, μF, μH

Lower Coal Zone Description Seams

Unit C Sandstone, shale claystone μH Unit B Sandstone, siltstone - Unit A Claystone, sandstone μB, μD

PALEOGRAPHY OF THE MERIT PILA BASIN

The Lower Sandstone is interpreting as alluvial fan transiting to braided river based on position, structural and textural features. The presence of coalified logs and their orientation in eastwest to southwest direction indicates environment of braided river in tropical rain forest.

Palynological study (Konzalová 2001, Konzalová 2005) proved significant sea influence especially in the Lower Coal Zone and Middle Shale-Sandstone unit.

Base of the Lower Coal Zone sub-unit 1 (Dorani 1990 and Liaw 1987) is interpreted based on recent field observation as a coastal plain with mangrove vegetation.

The transition to sandstones of subunit 2 reflects higher dynamics of sedimentary environment and sandstone body, cross bedding and structure suggest alluvial sediments of distributary channel.

The subunit 3 is interpreted as coastal plain with mangrove forest, which deposition was interrupted by major event of uplift in southwest of basin. This uplift is responsible for development of conglomerate beds of subunit 4 and for structural unconformity of the Merit Pila basin.

Later sediments of subunit 5 and Middle Shale-Sandstone unit are interpreted as coastal plain intersected by distributary channels.

Paleoenvironment of the Upper Coal Zone in Belawie Mujan mine is mangrove swamp, which was affected by distributary channels and their flood plains in the western and eastern part of the pit.

METHODS AND SAMPLESRank - light reflectance Maceral compositionProximate analysis (A, S, Qs, V)Ultimate analysis (C, H, N, S, O)Trace element (INAA)Composition of ash (SiO2, Al2O3, Fe2O3, CaO, MgO, Na2O,

K2O, TiO2, MnO, P2O5, SO3)

Sample location Belawie Mujan andMerith South

Sample location Beradai

CB

E230

231

229

μB

μC

μC

Sample location Tebulan Sample location Long Hill

C B

CC

SAMPLES FROM UPPER AND LOWER COAL ZONEBBC = bright bandedcoal, DBC = dull brightcoal, DC dull coal, BB = bright bands

Coal Zone No sample

Seam Code Macropetpgraphic Characteristics

1- Merit S.block μD -SF DBC 5 – Merit S. block μD -SR DC 3 –Belawie Mujan μD – SF DC, trace resinite 15 – Belawie Mujan μD -SR DC 4 – boundary M-BM μC -SF DBC 2 – boundary M-BM μC - SR DBC, resinite 6 – Merit S.block μC - SF DC 7- Merit S.block μC – SR DBC 235- Bela. Mujan b. μB - SF DBC 234 – Bela. Mujan b μB - SR DBC 236 – Bela. Mujan b μB - SR DBC 237 – Bela. Mujan b μB - SF DBC

UPPER COAL ZONE

238 – Bela. Mujan b μB - SR DBC Sub – Unit 5 - - - Sub - Unit 4 232 – Beradai E. pit E - S BBC

14. – Long Hill US D - S BBC 230-Beradai b. C1 - S BBC 231-Beradai b C - S DBC 229- Beradai b C - S DBC 16. TWC - Tebulan C - S BBC

Sub - Unit 3

13. Long Hill US C - MS DBC Sub - Unit 2 - - -

233-PO1 B2 - S BBC 10. Long Hill LS B1 - SF BBC 11. Long Hill LS B1 - SF BBC 12. Long Hill LS B1 - SF BBC 8. . Long Hill LS B1 - MBS DC with BB

LOWER COAL ZONE

Sub -Unit 1

9. . Long Hill LS B1 - SR DC

PROXIMATE ANALYSIS

ULTIMATE ANALYSISSeam Cdaf (%) Hdaf (%) Sodaf (MJ.kg-1) Ndaf (%) Odaf (%) μD 69.7 – 75.1 5.1 – 6.2 0.23 – 0.30 1.0 – 1.4 17.5 – 23.4μC 69.4 – 70.2 4.6 – 5.4 0.20 – 0.30 1.4 – 1.7 22.8 – 23.1μB 69.4 – 71.7 4.6 – 4.9 0.11 – 0.18 1.2 – 1.7 22.7 – 24.3E 73.1 6.3 0.06 0.8 19.71 D 65.2 5.6 0.40 1.4 27.4 C 68.9 – 72.9 4.5 – 5.1 0.09 – 0.25 1.5 – 1.7 22.0 – 24.3B 69.1 – 72.8 4.5 – 5.0 0.20 – 0.21 1.6 – 1.7 21.6 – 24.1

Seam Ad (%) Std (%) Qs

daf (MJ.kg-1) Vdaf (%) μD 3.1 – 7.8 0.20 – 0.22 26.4 – 27.7 41.9 – 42.5 μC 2.6 - 41.4 0.20 – 0.22 26.9 – 27.9 48.5 – 51.9 μB 2.1 – 12.1 0.10 – 0.17 28.0 – 28.6 48.2 – 55.1 E 2.3 0.06 31.2 61.5 D 42.9 0.23 25.5 53.5 C 2.6 – 29.6 0.05 – 0.23 28.0 – 28.5 45.5 – 50.6 B 0.9 - 14.3 0.2 – 0.23 27.0 – 29.1 45.3 – 47.8

Petrographic composition

Pe trographic composition

0% 20% 40% 60% 80% 100%

μD - 1 μD –2μD –3

μD –15μC – 4μC - 2μC - 6μC – 7

μB - 235μB - 234μB - 236μB - 237μB - 237

E - 232D - 14C - 230C -231

C - 229C - 16C - 13

B - 233B - 10B - 11B - 12

B – 8B - 9

huminiteliptiniteinertiniteminerals

Ulminit, suberinite and corpohuminite

Densinite with liptinite maceralsUlminite

Resinite

Suberinite and corpohuhimitebetween ulminite and macrinite

Resinite and funginite

RANK, MACERAL CHARACTERISTICSMaceral contents (vol.%) Seam Ro (%)

> 30 30 – 10 10 – 1 < 1

μD 0.41 – 0.43 U D Ch, G, Su, Re, Cu, Ma, Fg, Sp, Smf, Min, A, Bi

T, Fl, Ex, F, Id,

μC 0.41 – 0.44 U, D, (Min)

D, Min Re, Su, Ch, Cu,Ma, Min, Smf, G, A, Ld, Fg,

Sp, Fl, Ex, Bi, F,

μB 0.43 – 0.47 U, D D, (Min) Ch, Su, Re, G, Cu, A, Min, Sp, Fl, Ex, Ld, Bi, F

E 0.42 U D Re, Su, Ld, Ch, Min, G, Bi, Fg, Fl, Smf, M

A, Sp, Ex, F, Id

D 0.43 Min U, D Ch, G, Cu, Fl, Su, Re, Fg, Smf A, Sp, Ex, F, IdC 0.44 – 0.45 U D(Min) Su, Cu, Re, Ch, G, (Min), Fg,

Ma, Ld, A, I, S, Ex,

B

0.42 – 0.48 U, D D Min, Ch, Cu, Re, Min, Fg, Ma, A, G, Su, Sp, Fl, Id

Gelification index and Tissue preservation index Vegetation index and Ground water index

GI/TPI

1

10

100

0 0,5 1 1,5 2 2,5 3

TPI

GI

uCuBEDCBuD

GWI/VI

0

1

2

0 1 2 3 4

VI

GW

I

uDuCuBEDCB

MINERALS

Clay minerals and liptodetrinite

Clay minerals > quartz, carbonates >>> pyrite

TRACE ELEMENTS

Coal Zone

SiO2 Al2O3 Fe2O3 CaO MgO K2O TiO2

Upper 35.0 – 60.1 16.2 –26.5 2.9 - 8.9 2.4 - 10.6 2.0 – 5.6 1.2 –3.7 0.9 – 1.2 Lower 33.0 – 38.5 22.8 – 30.3 2.5 – 15.6 5.6 – 6.5 2.1 – 3.0 1.2 - 1.8 0.8 – 1.2

Coal Zone

As Cu Ni Pb Rb Sr Zn

Upper 13 - 31 40 - 50 18 - 40 25 - 40 170 - 200 250 - 360 20 - 50 Lower 7 - 15 35 - 44 5 – 70 10 -35 85 - 110 90 -120 20 - 40

CONCLUSIONS

The stratigraphical units and coal seams of the Tertiary Merit Pila Basin were characterized.

Coal in Merit Pila Basin is low rank - subbituminous coal which is rich in huminite. It contains variable amount of liptinite, mineral matter and little inertinite.

The origin of the seams of Lower and Upper Coal Zone is related to mangrove swamps and forest. The wet depositional conditions, changes in herbaceous and woody material were documented by the maceral composition and application of TPI-GI and GWI-VI diagrams.

By comparing the rank and maceral composition of coal from Merit Pila Basin to the properties of low rank coal from South/East Asia (Hutton et al. 1994; Wan Hasiah, O. Bachir, 2001; Amijaya, Littke 2005) many similarities were found. On the other hand the studied coal is characterized by low sulfur content and increased ash content from 0.9 % to 42.9 %

According to record of the study, the low rank coal from Merit Pila Basin is a suitable raw material for energy generation and non-energy utilization.

REFERENCES

Amija H., Littke R., 2005. Microfacies and depositional environment of Tertiary Tanjung Enimlow rank coal, South Sumatra Basin, Indonesia. International Journal of Coal Geology, 61, 197-221.

Dorani et al. (1993): Evaluation of the Coal Resources of Tebulan Block, Merit Pila Coal Field Sarawak, 21-37.

Hutton A., Herudiyanto B.D., Nas Ch. Pujobroto A., Sutarwan H., 1994. Liptinite in Indonesian Tertiary coals. Energy & Fuels, 8, 1469-1477.Konzalová M. 2001 and 2005. Reports of IGL AS CR, Prague, Czech Republic

Liaw et al. (1987): Evaluation of the Coal Resources of Merit Block, Merit Pila Coal Field Sarawak, Economic Geology Bulletin 3, 21-50.

Liaw et al. (1995): Merit Block South, Merit Pila Coal Field Sarawak, Economic Geology Bulletin 4, .17-31.

Wan Hasiah A., Bachir O., 2001. Petrographic insights into liquid hydrocarbon generating and expulsion from oil-generating coals of Sarawak, Malaysia. In: Petersen H. (ed.) Abstracts of the TSOP-ICCP Session, August 12-19, Geocenter Copenhagen, 21-28.