COAL BED METHANE POTENCY
MAKALAH ILMIAH
COAL BED METHANE POTENCY
OF TANJUNG FORMATION IN TANAH BUMBU
SOUTH KALIMANTAN
Oleh :
David P. Simatupang,1 Deddy Amarullah 2
Pusat Sumber Daya Geologi
Jl. Soekarno Hatta No. 444 Bandung
ABSTRACT
Coal deposits distributes widely in Indonesia, mainly in Sumatera and Kalimantan. These deposits
become an indication for a huge quantity of coal-bed methane (CBM) potency. As an environmentally
friendly source of energy, CBM could be one of Indonesia's future energy sources. Centre for Geological
Resources (CGR) started the exploration for this energy since 2005, while the study was conducted in
2008 at Tanjung Formation in Tanah Bumbu Area, South Kalimantan.
CSAT-1 well was drilled to provide CBM resources and deep coal mine potency data for Tanjung
Formation (Eocene) in Asem-asem Basin. This well went through 10 coal seams with three main seam,
which is E seam at 212.34-213.30 m depth, I seam at 261.93-264.20 m, and J seam at 270.20-275.35 m
depth. Calorific value from this three main seam categorized as high rank coal, vary from 6197-6745
cal/gram (adb), with total moisture between 4.51-7.11 %, adb.
Total coal resources used for CBM resources quantification is 112,733,226 tons (between 300 to 1000
meters depth). Based on desorption test and gas chromatograph measurement from samples at various
depth from three main seams, those coal gives methane resources estimation about 430 MSCF, with
methane content vary between 1.2 - 6.6 cu-ft/ton of coal.
Keywords: Tanjung Formation, Tanah Bumbu, CBM, methane content.
SARI
Endapan batubara tersebar luas di Indonesia, terutama di Pulau Sumatera dan Kalimantan. Endapan ini
menjadi indikasi besarnya potensi coal-bed methane (CBM). Sebagai salah satu sumber energy yang
ramah lingkungan, CBM dapat menjadi salah satu sumber energi bagi Indonesia dimasa yang akan
datang. Pusat Sumber Daya Geologi (PSDG) telah mulai melakukan eksplorasi sumber energi ini sejak
tahun 2005, dimana pada tahun 2008 dilakukan di Formasi Tanjung di Daerah Tanah Bumbu, Kalimantan
Selatan
Pemboran sumur CSAT-1 dilakukan untuk memberikan data sumber daya CBM dan data potensi
tambang dalam untuk Formasi Tanjung yang berumur Eosen di Cekungan Asem-asem. Sumur tersebut
menembus 10 lapisan batubara, dengan tiga diantaranya sebagai lapisan utama, yaitu lapisan E pada
kedalaman 212,34 - 213,30 m, lapisan I pada kedalaman 261,93-264,20 m, dan lapisan J pada 270,20 275,35 m. Nilai kalori dari ketiga lapisan utama ini dikategorikan sebagai batubara rank tinggi, dengan
variasi dari 6197 - 6745 cal/gram (adb), dengan total moisture antara 4,51 - 7,11 %, adb
Total sumber daya batubara yang digunakan untuk penghitungan sumber daya CBM adalah 112.733.226
ton (yang berada di kedalaman antara 300 hingga 1000 meter). Berdasarkan desorption test dan
pengukuran gas chromatography terhadap sampel batubara pada berbagai kedalaman di ketiga seam
utama, batubara tersebut memberikan sumber daya metana sekitar 420 MSCF dengan kandungan
metana yang bervariasi antara 1,2 6,6 cu-ft/ton batubara.
Kata Kunci: Formasi Tanjung, Tanah Bumbu, CBM, kandungan metana.
INTRODUCTION
Coal deposits are distributed widely in
Indonesia, mainly in Sumatera and Kalimantan
islands, which is utilized mostly for power plant.
The other energy resource from coal deposits
that environmentally clean is the saturated gas
within the coal which is known as coal-bed
Diterima tanggal 04 Pebruari 2010
Revisi tanggal 24 Maret 2010
methane (CBM). Some advantages of CBM are
can make underground mining saver, provide
cleaner & environmentally friendly source of
energy and can be easily transported with
pipeline network for national and regional supply.
As a government institution with fossil
energy exploration duty, Centre for Geological
Buletin Sumber Daya Geologi Volume 5 Nomor 2 - 2010
1
MAKALAH ILMIAH
Resources (CGR) has been carried out CBM
exploration since 2005. Some exploration drilling
has conducted in several basins in order to
provide CBM and deep coal mine resources
potency data. The latest exploration drilling
commenced in 2008 at Tanah Bumbu area, in
purpose to measure the methane content of
Tanjung Formation.
Coal deposits of Tanjung Formation in
Tanah Bumbu area is believed as one of potential
coal bearing that have significant methane
content. The Eocene Tanjung Formation is
included into Asem-Asem Basin (E. Rustandi et
al., 1995; N. Sikumbang et al., 1994).
Administratively, the study area is within to Tanah
Bumbu Regency, South Kalimantan Province.
METHODOLOGY
CBM exploration in Tanah Bumbu Area
drilled CSAT-1 well, this location selected based
on geological mapping, to get samples from
several coal seams in Tanjung Formation. After
core descript, the coal was packed into canisters
and sealed due to prevent leakage. After leak
test, the canister was ready for desorption test.
Desorption test measurement was made in
periodical time intervals by vent out the gas until
there are none gas come out from canister. After
desorption test finished, coal from canister was
crushed to get the residual gas that still trap
inside. Gas samples from each canister tested
with Gas Chromatograph (GC) to get the
compositional data. Finally, the crushed coal was
sent to laboratory for coal quality measurements.
Coal resources for gas content
measurement calculated at depth interval 3001000 meters and only for three main seams with
an assumption that the methane can be produced
efficiently in that depth interval and in thick coal
seams.
Figure 1. Tanah Bumbu Study Area in Tectonic Framework of Barito Basin (Satyana & Silitonga)
2
Buletin Sumber Daya Geologi Volume 5 Nomor 2 - 2010
MAKALAH ILMIAH
southeastwardly. Target in this study is Tanjung
Formation coal.
Ten coal seams were found through
exploration drilling activity in Tanjung Formation
at the study area. The upper seam depth was
located at 185.80 - 186.40 m and the lowest seam
was at 284.45 - 284.90 m. The thickest coal seam
at 270.20 - 275.35 m and the thinnest coal seam
found at 194.54 - 194.74 m depth. Complete coal
seams data from drilling result are listed in Table 1
Coal resources of Tanjung Formation were
calculated separately in two Blocks. Block I is for
depth between 300-500 m and Blok II for 5001000 m. This resource calculation based on coal
spread as far as 3000 meter along strike. Total
coal resources are 112,733,226 tons (Table 2).
Based on the thickness, gas content was
measured from 3 (E, I, & J) out of ten coal seams.
This is due to an assumption that only thick
seams have possibility to produce significant
gas..
GEOLOGY AND COAL DEPOSIT RESULT
Tanah Bumbu area is part of Asem-Asem
Basin, located in the south eastern Kalimantan.
Asem-Asem Basin is part of Barito Basin that
separated by Meratus Montains (N. Sikumbang,
1986; A.H. Satyana and P.D. Silitonga, 1994).
According to E. Rustandi et al., (1995), Tertiary
stratigraphy of Asem-Asem Basin begins by
Eocene age Tanjung Formation as coal
measures, conformably overlain by OligoMiocene Berai Formation, which predominantly
consist of limestone. The Middle Miocene
Warukin Formation that also coal measures, lay
conformably above Berai Formation. The upper
formation is Mio-Pliocene Dahor Formation,
which predominantly consist of coarse
sandstone, laid unconformably above Warukin
Formation. The structural configuration in Tanah
Bumbu area classified as simple structures with
dip of bedding generally ranging between 10-20o
Table 1. Coal seams of CSAT-1
Seam
A*
B
E* +
F
G
H
I* +
J* +
K
L
D e p th (m )
F rom
1 8 5 .8 0
1 9 4 .5 4
2 1 2 .3 4
2 3 7 .1 0
2 5 0 .3 0
2 6 0 .8 0
2 6 1 .9 3
2 7 0 .2 0
2 7 7 .4 0
2 8 4 .4 5
To
1 8 6 .4 0
1 9 4 .7 4
2 1 3 .3 0
2 3 7 .5 0
2 5 0 .7 0
2 6 1 .3 0
2 6 4 .2 0
2 7 5 .3 5
2 7 7 .9 0
2 8 4 .9 0
T h ic k n e s s (m )
0 .6 0
0 .2 0
0 .9 6
0 .4 0
0 .4 0
0 .5 0
2 .2 7
5 .0 5
0 .5 0
0 .4 5
* = coal seam analysed
+= gas content calculated
Table 1. Coal seams of CSAT-1
S eam
E
I
J
D ep th (m eter)
F rom
To
21 2.3 4 21 3.3
26 1.9 3 26 4.2
27 0.2 27 5.3 5
T h ick
(m eter)
0.96
2.27
5.05
T otal
C o al R esou rces (Ton )
30 0-50 0 m
50 0-10 00 m
3,734 ,434
9,336 ,085
8,830 ,380
22 ,07 5,95 1
19 ,64 4,67 9
49 ,111,697
32 ,20 9,49 3
80 ,52 3,73 3
Buletin Sumber Daya Geologi Volume 5 Nomor 2 - 2010
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MAKALAH ILMIAH
Table 3. Coal Quality
A nalysis
U nit
B asis
M oisture
Volatile M atter
Fixed Carbon
A sh
Total Sulphur
C alorific Value
%
%
%
%
%
cal/gr
adb
adb
adb
adb
adb
adb
C oal Seam
E
I
4.51
7.11
45.63
42.35
36.8
44.04
12.88
6.50
0.58
0.27
6605
6745
A
6.86
45.22
46.43
1.49
0.35
7252
J
4.72
42.00
37.66
15.62
3.27
6197
Table 4. Canisters Properties
C oal
S eam
No
C a n iste r
A
B
1
2
3
4
5
9
6
7
8
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
E
F
G
H
I
J
K
L
4
D e p th
F rom
To
m e te r
m e te r
1 8 5 .8 0 1 8 6 .4 0
1 9 4 .5 4 1 9 4 .7 4
2 1 2 .3 4 2 1 2 .8 4
2 1 2 .8 4 2 1 3 .3 0
2 3 7 .1 0 2 3 7 .5 0
2 5 0 .3 0 2 5 0 .7 0
2 6 0 .8 0 2 6 1 .3 0
2 6 1 .9 3 2 6 2 .4 0
2 6 2 .4 0 2 6 2 .7 0
2 6 2 .7 0 2 6 3 .2 0
2 6 3 .2 0 2 6 3 .7 0
2 6 3 .7 0 2 6 4 .2 0
2 7 0 .2 0 2 7 0 .6 0
2 7 0 .6 0 2 7 1 .0 0
2 7 1 .0 0 2 7 1 .3 5
2 7 1 .4 0 2 7 1 .7 0
2 7 1 .7 0 2 7 2 .3 5
2 7 2 .4 0 2 7 3 .0 0
2 7 3 .0 0 2 7 3 .5 0
2 7 3 .5 0 2 7 4 .1 0
2 7 4 .1 0 2 7 4 .7 0
2 7 4 .7 0 2 7 5 .3 5
2 7 7 .4 0 2 7 7 .7 0
2 7 7 .7 0 2 7 7 .9 0
2 8 4 .4 5 2 8 4 .9 0
Buletin Sumber Daya Geologi Volume 5 Nomor 2 - 2010
C o re
L e n g th
m e te r
0 .6 0
0 .2 0
0 .9 4
0 .4 0
0 .4 0
0 .5 0
2 .2 7
5 .1 5
0 .5 0
0 .4 5
C oal
W e ig h t
gram
714
345
1098
895
970
910
1041
1096
342
1089
832
968
904
921
814
792
1286
11 8 5
1 0 11
11 3 0
1097
1608
572
458
1251
MAKALAH ILMIAH
Table 5. Result of Q1, Q2, Q3 and Total Gas in Canisters
C oal
S ea m
E
I
J
No
C a n ister
3
4
7
8
10
11
12
13
14
15
16
17
18
19
20
21
22
G a s Vo lu m e (cc )
Q1
Q2
Q3
3 7 .3 7
4 2 9 .0 0
6 4 1 .0 6
2 .8 9
1 5 9 .0 0
5 2 2 .5 4
2 5 .4 5 1 ,0 8 2 .0 0
8 9 5 .7 2
4 2 .2 8
3 2 0 .0 0
1 6 3 .4 8
4 3 .9 3 1 ,1 2 4 .0 0
8 9 0 .0 0
9 7 .4 6
9 7 0 .0 0
6 2 0 .3 3
5 7 .4 0 1 ,1 7 0 .0 0
7 9 1 .11
1 6 .5 9
1 8 2 .2 0
3 4 4 .8 4
8 1 .3 1
7 0 6 .5 0
4 4 3 .3 7
2 4 .1 2
6 1 0 .0 0
3 9 1 .8 6
2 3 .2 0
7 3 2 .2 5
3 8 1 .2 7
4 1 .6 3
6 3 8 .7 5 1 ,1 5 2 .7 8
2 1 .5 2
9 7 5 .0 0
5 7 0 .4 5
4 1 .4 1
7 6 4 .0 0
4 8 6 .6 9
6 .2 2 1 ,0 3 4 .5 0
5 4 3 .9 8
4 1 .4 1
5 4 1 .0 0
8 7 6 .9 6
1 5 3 .9 7 1 ,3 5 0 .7 5
7 7 4 .0 8
To ta l
G a s (cc )
11 0 7 .4 3
6 8 4 .4 3
2 0 0 3 .1 7
5 2 5 .7 6
2 0 5 7 .9 3
1 6 8 7 .7 9
2 0 1 8 .5 1
5 4 3 .6 3
1 2 3 1 .1 8
1 0 2 5 .9 7
11 3 6 .7 2
1 8 3 3 .1 6
1 5 6 6 .9 7
1 2 9 2 .1 0
1 5 8 4 .7 0
1 4 5 9 .3 7
2 2 7 8 .8 0
Figure 3. Samples of Graphic between Q1 vs. time, from Canister #7
Buletin Sumber Daya Geologi Volume 5 Nomor 2 - 2010
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MAKALAH ILMIAH
Table 6. Gas Content Measurement and Fraction of Gas
Coal
Seam
No
Canister
3
4
7
8
10
11
12
13
14
15
16
17
18
19
20
21
22
E
I
J
Total
G as
cc
1107.43
684.43
2003.17
525.76
2057.93
1687.79
2018.51
543.63
1231.18
1025.97
1136.72
1833.16
1566.97
1292.10
1584.70
1459.37
2278.80
G as Volum e in
Coal
cc/gr cuft/ton
1.0086
35.62
0.7647
27.01
1.8277
64.55
1.5373
54.29
1.8897
66.74
2.0286
71.64
2.0852
73.64
0.6014
21.24
1.3368
47.21
1.2604
44.51
1.4353
50.69
1.4255
50.34
1.3223
46.70
1.2780
45.13
1.4024
49.52
1.3303
46.98
1.4172
50.05
G as Content in Coal (Fraction)
O2
N2
CH 4
CO 2
cuft/ton cuft/ton cuft/ton cuft/ton
3.6573 18.2516
0.0121
2.2651
3.5794 14.8956
0.0058
1.2778
2.3970 35.9139
0.0150
6.3385
9.6355 38.3305
0.0071
2.5308
4.5037 41.7418
0.0141
6.6111
9.4078 46.9187
0.0117
5.7831
7.3502 43.3877
0.0113
6.3239
2.6405 12.5711
0.0128
1.2050
6.2204 32.6490
0.0104
3.3124
5.6481 26.8427
0.0135
3.0150
7.3908 35.7570
0.0110
3.6491
3.1419 30.3629
0.0113
4.4334
3.4558 27.3055
0.0136
3.6900
7.3315 31.2744
0.0116
2.7987
2.5622 29.4525
0.0158
4.3588
4.3333 26.6224
0.0126
3.4011
1.3812 23.4727
0.0154
5.3357
Table 7. Average Methane Content for each Seam
Seam
E
I
J
Average M et h ane
C o n te n t (c u ft/to n )
1 .8 2 1 7 3 3
4 .9 5 9 8 8 9
3 .6 8 6 6 6 3
Table 8. Total Methane between 300-500 meters depth
S eam
E
I
J
C oal R esou rces
(Ton )
3,734,434
8,830,380
19,644,679
Average M eth an e
C onten t (cuft/ton)
1.821733
4.959889
3.686663
S u b Total
Total M eth an e
(cu ft)
6,803,141.654
43,797,704.63
72,423,311.22
123,024,157.5
Table 9. Total Methane between 500-1000 meters depth
S eam
E
I
J
6
C oal R esou rces
(Ton )
9,336,085
22,075,951
49,111,697
Average M eth an e
C onten t (cuft/ton)
1.821733
4.959889
3.686663
S u b Total
Buletin Sumber Daya Geologi Volume 5 Nomor 2 - 2010
Total M eth an e
(cu ft)
17,007,854.14
109,494,266.53
181,058,276.20
307,560,396.86
MAKALAH ILMIAH
Quality of coal from laboratory result show
that range of calorific value (adb) is between 6197
- 7252 cal/gr, total sulphur (adb) 0.27 - 3.27 %,
and ash content (adb) 1.49 - 15.62 %. Complete
coal quality data are listed in Table 3. This result
classified in SNI (Indonesian National Standard)
as high rank coal.
Gas Content Measurement
Since the gas was trapped inside coal cleats
and matrix, special methods to calculate gas
content have to be applied. This study measured
the gas content directly by collect the fresh coal
from core barrel and sealed it in canisters. The
gas was vent out from the canister in periodical of
time and the volume is measured and labelled as
Q2. From this Q2 data series, the lost gas volume
(Q1) was calculated by extrapolate the Q2 vs.
time graphic to initial time (first gas came out from
the coal). The gas that still saturated in coal push
out by crushed the coal; volume of the gas from
crusher chamber is measures to get the Q3. The
total gas in a bulk of coal calculates by summation
Q1, Q2 & Q3. A sample graphic of Q2 is presented
in Figure 3.
Canisters that were used in this study made
from PVC with HQ diameter and 60 cm length.
Properties of canister after filled with coal are
presented in Table 4. The coloured seam (E, I and
J) is the seam which gas volume was included in
resources potency calculations.
Q2 measurement graphic is vary for each
seam, there were some canisters that continuing
to produce gas (after 8 month) when others were
stop earlier and crushed to get the Q3. Some Q3
calculation in Table 5 generated by used Q3
data's from other canisters in the same coal
seam. This study is still in progress until there is
no gas came out from the coal.
The produced gas samples were collected
and analysed with GC in CGR mobile laboratory
(Figure 4). Further, the gas content data then
converted in to cubic-feet and presented in Table
6. Average methane content for each coal seams
(Table 7) and coal resources (Table 2) was used
to determine the coal bed methane content at
Tanjung Formation in Tanah Bumbu area (Table 8
and Table 9).
Total methane content of Tanjung Formation
in Tanah Bumbu Area between 300 to 1000
meters depth is 430,584,554.36 cu-ft (~430
MSCF).
cuft/ton, with the highest average methane
content 4.95 cuft/ton at I seam. This is caused by
sample depth which only 212.34 - 275.35 m. At
this depth, methane probably still going up
through overburden and release to atmosphere,
besides the meteoric water might still can reach
the coal seams. We believe that methane content
will increase if drilling reaches deeper coal seam.
This result can take as a minimum methane
content of the Tanjung Formation.
The deepest point of CSAT-1 drilling was
284.90 m, however in this study the methane
content measurement calculated for coal is at
300-1000 m depth. This calculation based on
assumption that 300 to 1000 meter is the sweet
spot for methane accumulation. As mention
above, shallow coal will give lower methane
content, while for coal deeper than 1000 m, the
cleat volume and permeability will significantly
decrease by the overburden pressure. Ideally, we
collect coal samples deeper than 300 m, but
drilling equipment limitation push us to make this
result as minimum methane content, not the
average methane content for Tanjung Formation.
Hopefully, in the future we can drill deeper and
collect more representative samples for this
formation.
With only one well, it is challenging to
evaluate the data for basin or even formation
scale that is why we restricted our study to some
thick coal seams from Tanjung Formation at
Tanah Bumbu area. For a detail prospection it is
better to have some drilling wells to get more data
and to be used as production/dewatering wells.
But, for CGR that have task to provide primary
data for the next exploration stage, this data can
give minimum estimation for methane content in
Tanjung Formation.
CONCLUSION
CGR as government institution provide
resource potency data in Tanjung Formation for
further follow-up. In Tanah Bumbu Area, South
Kalimantan, CGR drilled CSAT-1 to find methane
content in Eocene Tanjung Formation. Based on
the three main coal seam from exploration well,
the average methane content vary from 1.82 to
4.95 cu-ft per tons, whereas the total reach up to
430 MSCF of methane.
DISCUSSION
430 MSCF methane result is seems small
for production scale, but we should consider this
result is only for small part of the Tanjung
Formation's coal. The desorption test
measurement only reach its maximum at 6.3
Buletin Sumber Daya Geologi Volume 5 Nomor 2 - 2010
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MAKALAH ILMIAH
REFERENCES
Rustandi, E., Nila, E. S., Sanyoto, P. & Margono, U. 1995. Peta Geologi Lembar Kotabaru Kalimantan,
P3G.
Satyana, A. H & Silitonga, P. D. 1994. Tectonic Reversal in East Barito Basin, South Kalimantan:
Consideration of the Type of Inversion Structures and Petroleum System Significance. Proceedings
of the Indonesian 22nd Annual Convention.
Sikumbang N. 1986. Geology and Tectonics of Pre Tertiary Rocks in Meratus Mountains, South East
Kalimantan, Indonesia. Ph.D Thesis University of London.
Sikumbang, N. & Heryanto, R. 1994. Peta Geologi Lembar Banjarmasin, Kalimantan, P3G.
Tim Pemboran Tanah Bumbu. 2008. Laporan Pemboran Dalam dan Pengukuran Gas dalam Lapisan
Batubara Daerah Tanah Bumbu Provinsi Kalimantan Selatan, Pusat Sumber Daya Geologi
8
Buletin Sumber Daya Geologi Volume 5 Nomor 2 - 2010
COAL BED METHANE POTENCY
OF TANJUNG FORMATION IN TANAH BUMBU
SOUTH KALIMANTAN
Oleh :
David P. Simatupang,1 Deddy Amarullah 2
Pusat Sumber Daya Geologi
Jl. Soekarno Hatta No. 444 Bandung
ABSTRACT
Coal deposits distributes widely in Indonesia, mainly in Sumatera and Kalimantan. These deposits
become an indication for a huge quantity of coal-bed methane (CBM) potency. As an environmentally
friendly source of energy, CBM could be one of Indonesia's future energy sources. Centre for Geological
Resources (CGR) started the exploration for this energy since 2005, while the study was conducted in
2008 at Tanjung Formation in Tanah Bumbu Area, South Kalimantan.
CSAT-1 well was drilled to provide CBM resources and deep coal mine potency data for Tanjung
Formation (Eocene) in Asem-asem Basin. This well went through 10 coal seams with three main seam,
which is E seam at 212.34-213.30 m depth, I seam at 261.93-264.20 m, and J seam at 270.20-275.35 m
depth. Calorific value from this three main seam categorized as high rank coal, vary from 6197-6745
cal/gram (adb), with total moisture between 4.51-7.11 %, adb.
Total coal resources used for CBM resources quantification is 112,733,226 tons (between 300 to 1000
meters depth). Based on desorption test and gas chromatograph measurement from samples at various
depth from three main seams, those coal gives methane resources estimation about 430 MSCF, with
methane content vary between 1.2 - 6.6 cu-ft/ton of coal.
Keywords: Tanjung Formation, Tanah Bumbu, CBM, methane content.
SARI
Endapan batubara tersebar luas di Indonesia, terutama di Pulau Sumatera dan Kalimantan. Endapan ini
menjadi indikasi besarnya potensi coal-bed methane (CBM). Sebagai salah satu sumber energy yang
ramah lingkungan, CBM dapat menjadi salah satu sumber energi bagi Indonesia dimasa yang akan
datang. Pusat Sumber Daya Geologi (PSDG) telah mulai melakukan eksplorasi sumber energi ini sejak
tahun 2005, dimana pada tahun 2008 dilakukan di Formasi Tanjung di Daerah Tanah Bumbu, Kalimantan
Selatan
Pemboran sumur CSAT-1 dilakukan untuk memberikan data sumber daya CBM dan data potensi
tambang dalam untuk Formasi Tanjung yang berumur Eosen di Cekungan Asem-asem. Sumur tersebut
menembus 10 lapisan batubara, dengan tiga diantaranya sebagai lapisan utama, yaitu lapisan E pada
kedalaman 212,34 - 213,30 m, lapisan I pada kedalaman 261,93-264,20 m, dan lapisan J pada 270,20 275,35 m. Nilai kalori dari ketiga lapisan utama ini dikategorikan sebagai batubara rank tinggi, dengan
variasi dari 6197 - 6745 cal/gram (adb), dengan total moisture antara 4,51 - 7,11 %, adb
Total sumber daya batubara yang digunakan untuk penghitungan sumber daya CBM adalah 112.733.226
ton (yang berada di kedalaman antara 300 hingga 1000 meter). Berdasarkan desorption test dan
pengukuran gas chromatography terhadap sampel batubara pada berbagai kedalaman di ketiga seam
utama, batubara tersebut memberikan sumber daya metana sekitar 420 MSCF dengan kandungan
metana yang bervariasi antara 1,2 6,6 cu-ft/ton batubara.
Kata Kunci: Formasi Tanjung, Tanah Bumbu, CBM, kandungan metana.
INTRODUCTION
Coal deposits are distributed widely in
Indonesia, mainly in Sumatera and Kalimantan
islands, which is utilized mostly for power plant.
The other energy resource from coal deposits
that environmentally clean is the saturated gas
within the coal which is known as coal-bed
Diterima tanggal 04 Pebruari 2010
Revisi tanggal 24 Maret 2010
methane (CBM). Some advantages of CBM are
can make underground mining saver, provide
cleaner & environmentally friendly source of
energy and can be easily transported with
pipeline network for national and regional supply.
As a government institution with fossil
energy exploration duty, Centre for Geological
Buletin Sumber Daya Geologi Volume 5 Nomor 2 - 2010
1
MAKALAH ILMIAH
Resources (CGR) has been carried out CBM
exploration since 2005. Some exploration drilling
has conducted in several basins in order to
provide CBM and deep coal mine resources
potency data. The latest exploration drilling
commenced in 2008 at Tanah Bumbu area, in
purpose to measure the methane content of
Tanjung Formation.
Coal deposits of Tanjung Formation in
Tanah Bumbu area is believed as one of potential
coal bearing that have significant methane
content. The Eocene Tanjung Formation is
included into Asem-Asem Basin (E. Rustandi et
al., 1995; N. Sikumbang et al., 1994).
Administratively, the study area is within to Tanah
Bumbu Regency, South Kalimantan Province.
METHODOLOGY
CBM exploration in Tanah Bumbu Area
drilled CSAT-1 well, this location selected based
on geological mapping, to get samples from
several coal seams in Tanjung Formation. After
core descript, the coal was packed into canisters
and sealed due to prevent leakage. After leak
test, the canister was ready for desorption test.
Desorption test measurement was made in
periodical time intervals by vent out the gas until
there are none gas come out from canister. After
desorption test finished, coal from canister was
crushed to get the residual gas that still trap
inside. Gas samples from each canister tested
with Gas Chromatograph (GC) to get the
compositional data. Finally, the crushed coal was
sent to laboratory for coal quality measurements.
Coal resources for gas content
measurement calculated at depth interval 3001000 meters and only for three main seams with
an assumption that the methane can be produced
efficiently in that depth interval and in thick coal
seams.
Figure 1. Tanah Bumbu Study Area in Tectonic Framework of Barito Basin (Satyana & Silitonga)
2
Buletin Sumber Daya Geologi Volume 5 Nomor 2 - 2010
MAKALAH ILMIAH
southeastwardly. Target in this study is Tanjung
Formation coal.
Ten coal seams were found through
exploration drilling activity in Tanjung Formation
at the study area. The upper seam depth was
located at 185.80 - 186.40 m and the lowest seam
was at 284.45 - 284.90 m. The thickest coal seam
at 270.20 - 275.35 m and the thinnest coal seam
found at 194.54 - 194.74 m depth. Complete coal
seams data from drilling result are listed in Table 1
Coal resources of Tanjung Formation were
calculated separately in two Blocks. Block I is for
depth between 300-500 m and Blok II for 5001000 m. This resource calculation based on coal
spread as far as 3000 meter along strike. Total
coal resources are 112,733,226 tons (Table 2).
Based on the thickness, gas content was
measured from 3 (E, I, & J) out of ten coal seams.
This is due to an assumption that only thick
seams have possibility to produce significant
gas..
GEOLOGY AND COAL DEPOSIT RESULT
Tanah Bumbu area is part of Asem-Asem
Basin, located in the south eastern Kalimantan.
Asem-Asem Basin is part of Barito Basin that
separated by Meratus Montains (N. Sikumbang,
1986; A.H. Satyana and P.D. Silitonga, 1994).
According to E. Rustandi et al., (1995), Tertiary
stratigraphy of Asem-Asem Basin begins by
Eocene age Tanjung Formation as coal
measures, conformably overlain by OligoMiocene Berai Formation, which predominantly
consist of limestone. The Middle Miocene
Warukin Formation that also coal measures, lay
conformably above Berai Formation. The upper
formation is Mio-Pliocene Dahor Formation,
which predominantly consist of coarse
sandstone, laid unconformably above Warukin
Formation. The structural configuration in Tanah
Bumbu area classified as simple structures with
dip of bedding generally ranging between 10-20o
Table 1. Coal seams of CSAT-1
Seam
A*
B
E* +
F
G
H
I* +
J* +
K
L
D e p th (m )
F rom
1 8 5 .8 0
1 9 4 .5 4
2 1 2 .3 4
2 3 7 .1 0
2 5 0 .3 0
2 6 0 .8 0
2 6 1 .9 3
2 7 0 .2 0
2 7 7 .4 0
2 8 4 .4 5
To
1 8 6 .4 0
1 9 4 .7 4
2 1 3 .3 0
2 3 7 .5 0
2 5 0 .7 0
2 6 1 .3 0
2 6 4 .2 0
2 7 5 .3 5
2 7 7 .9 0
2 8 4 .9 0
T h ic k n e s s (m )
0 .6 0
0 .2 0
0 .9 6
0 .4 0
0 .4 0
0 .5 0
2 .2 7
5 .0 5
0 .5 0
0 .4 5
* = coal seam analysed
+= gas content calculated
Table 1. Coal seams of CSAT-1
S eam
E
I
J
D ep th (m eter)
F rom
To
21 2.3 4 21 3.3
26 1.9 3 26 4.2
27 0.2 27 5.3 5
T h ick
(m eter)
0.96
2.27
5.05
T otal
C o al R esou rces (Ton )
30 0-50 0 m
50 0-10 00 m
3,734 ,434
9,336 ,085
8,830 ,380
22 ,07 5,95 1
19 ,64 4,67 9
49 ,111,697
32 ,20 9,49 3
80 ,52 3,73 3
Buletin Sumber Daya Geologi Volume 5 Nomor 2 - 2010
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MAKALAH ILMIAH
Table 3. Coal Quality
A nalysis
U nit
B asis
M oisture
Volatile M atter
Fixed Carbon
A sh
Total Sulphur
C alorific Value
%
%
%
%
%
cal/gr
adb
adb
adb
adb
adb
adb
C oal Seam
E
I
4.51
7.11
45.63
42.35
36.8
44.04
12.88
6.50
0.58
0.27
6605
6745
A
6.86
45.22
46.43
1.49
0.35
7252
J
4.72
42.00
37.66
15.62
3.27
6197
Table 4. Canisters Properties
C oal
S eam
No
C a n iste r
A
B
1
2
3
4
5
9
6
7
8
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
E
F
G
H
I
J
K
L
4
D e p th
F rom
To
m e te r
m e te r
1 8 5 .8 0 1 8 6 .4 0
1 9 4 .5 4 1 9 4 .7 4
2 1 2 .3 4 2 1 2 .8 4
2 1 2 .8 4 2 1 3 .3 0
2 3 7 .1 0 2 3 7 .5 0
2 5 0 .3 0 2 5 0 .7 0
2 6 0 .8 0 2 6 1 .3 0
2 6 1 .9 3 2 6 2 .4 0
2 6 2 .4 0 2 6 2 .7 0
2 6 2 .7 0 2 6 3 .2 0
2 6 3 .2 0 2 6 3 .7 0
2 6 3 .7 0 2 6 4 .2 0
2 7 0 .2 0 2 7 0 .6 0
2 7 0 .6 0 2 7 1 .0 0
2 7 1 .0 0 2 7 1 .3 5
2 7 1 .4 0 2 7 1 .7 0
2 7 1 .7 0 2 7 2 .3 5
2 7 2 .4 0 2 7 3 .0 0
2 7 3 .0 0 2 7 3 .5 0
2 7 3 .5 0 2 7 4 .1 0
2 7 4 .1 0 2 7 4 .7 0
2 7 4 .7 0 2 7 5 .3 5
2 7 7 .4 0 2 7 7 .7 0
2 7 7 .7 0 2 7 7 .9 0
2 8 4 .4 5 2 8 4 .9 0
Buletin Sumber Daya Geologi Volume 5 Nomor 2 - 2010
C o re
L e n g th
m e te r
0 .6 0
0 .2 0
0 .9 4
0 .4 0
0 .4 0
0 .5 0
2 .2 7
5 .1 5
0 .5 0
0 .4 5
C oal
W e ig h t
gram
714
345
1098
895
970
910
1041
1096
342
1089
832
968
904
921
814
792
1286
11 8 5
1 0 11
11 3 0
1097
1608
572
458
1251
MAKALAH ILMIAH
Table 5. Result of Q1, Q2, Q3 and Total Gas in Canisters
C oal
S ea m
E
I
J
No
C a n ister
3
4
7
8
10
11
12
13
14
15
16
17
18
19
20
21
22
G a s Vo lu m e (cc )
Q1
Q2
Q3
3 7 .3 7
4 2 9 .0 0
6 4 1 .0 6
2 .8 9
1 5 9 .0 0
5 2 2 .5 4
2 5 .4 5 1 ,0 8 2 .0 0
8 9 5 .7 2
4 2 .2 8
3 2 0 .0 0
1 6 3 .4 8
4 3 .9 3 1 ,1 2 4 .0 0
8 9 0 .0 0
9 7 .4 6
9 7 0 .0 0
6 2 0 .3 3
5 7 .4 0 1 ,1 7 0 .0 0
7 9 1 .11
1 6 .5 9
1 8 2 .2 0
3 4 4 .8 4
8 1 .3 1
7 0 6 .5 0
4 4 3 .3 7
2 4 .1 2
6 1 0 .0 0
3 9 1 .8 6
2 3 .2 0
7 3 2 .2 5
3 8 1 .2 7
4 1 .6 3
6 3 8 .7 5 1 ,1 5 2 .7 8
2 1 .5 2
9 7 5 .0 0
5 7 0 .4 5
4 1 .4 1
7 6 4 .0 0
4 8 6 .6 9
6 .2 2 1 ,0 3 4 .5 0
5 4 3 .9 8
4 1 .4 1
5 4 1 .0 0
8 7 6 .9 6
1 5 3 .9 7 1 ,3 5 0 .7 5
7 7 4 .0 8
To ta l
G a s (cc )
11 0 7 .4 3
6 8 4 .4 3
2 0 0 3 .1 7
5 2 5 .7 6
2 0 5 7 .9 3
1 6 8 7 .7 9
2 0 1 8 .5 1
5 4 3 .6 3
1 2 3 1 .1 8
1 0 2 5 .9 7
11 3 6 .7 2
1 8 3 3 .1 6
1 5 6 6 .9 7
1 2 9 2 .1 0
1 5 8 4 .7 0
1 4 5 9 .3 7
2 2 7 8 .8 0
Figure 3. Samples of Graphic between Q1 vs. time, from Canister #7
Buletin Sumber Daya Geologi Volume 5 Nomor 2 - 2010
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MAKALAH ILMIAH
Table 6. Gas Content Measurement and Fraction of Gas
Coal
Seam
No
Canister
3
4
7
8
10
11
12
13
14
15
16
17
18
19
20
21
22
E
I
J
Total
G as
cc
1107.43
684.43
2003.17
525.76
2057.93
1687.79
2018.51
543.63
1231.18
1025.97
1136.72
1833.16
1566.97
1292.10
1584.70
1459.37
2278.80
G as Volum e in
Coal
cc/gr cuft/ton
1.0086
35.62
0.7647
27.01
1.8277
64.55
1.5373
54.29
1.8897
66.74
2.0286
71.64
2.0852
73.64
0.6014
21.24
1.3368
47.21
1.2604
44.51
1.4353
50.69
1.4255
50.34
1.3223
46.70
1.2780
45.13
1.4024
49.52
1.3303
46.98
1.4172
50.05
G as Content in Coal (Fraction)
O2
N2
CH 4
CO 2
cuft/ton cuft/ton cuft/ton cuft/ton
3.6573 18.2516
0.0121
2.2651
3.5794 14.8956
0.0058
1.2778
2.3970 35.9139
0.0150
6.3385
9.6355 38.3305
0.0071
2.5308
4.5037 41.7418
0.0141
6.6111
9.4078 46.9187
0.0117
5.7831
7.3502 43.3877
0.0113
6.3239
2.6405 12.5711
0.0128
1.2050
6.2204 32.6490
0.0104
3.3124
5.6481 26.8427
0.0135
3.0150
7.3908 35.7570
0.0110
3.6491
3.1419 30.3629
0.0113
4.4334
3.4558 27.3055
0.0136
3.6900
7.3315 31.2744
0.0116
2.7987
2.5622 29.4525
0.0158
4.3588
4.3333 26.6224
0.0126
3.4011
1.3812 23.4727
0.0154
5.3357
Table 7. Average Methane Content for each Seam
Seam
E
I
J
Average M et h ane
C o n te n t (c u ft/to n )
1 .8 2 1 7 3 3
4 .9 5 9 8 8 9
3 .6 8 6 6 6 3
Table 8. Total Methane between 300-500 meters depth
S eam
E
I
J
C oal R esou rces
(Ton )
3,734,434
8,830,380
19,644,679
Average M eth an e
C onten t (cuft/ton)
1.821733
4.959889
3.686663
S u b Total
Total M eth an e
(cu ft)
6,803,141.654
43,797,704.63
72,423,311.22
123,024,157.5
Table 9. Total Methane between 500-1000 meters depth
S eam
E
I
J
6
C oal R esou rces
(Ton )
9,336,085
22,075,951
49,111,697
Average M eth an e
C onten t (cuft/ton)
1.821733
4.959889
3.686663
S u b Total
Buletin Sumber Daya Geologi Volume 5 Nomor 2 - 2010
Total M eth an e
(cu ft)
17,007,854.14
109,494,266.53
181,058,276.20
307,560,396.86
MAKALAH ILMIAH
Quality of coal from laboratory result show
that range of calorific value (adb) is between 6197
- 7252 cal/gr, total sulphur (adb) 0.27 - 3.27 %,
and ash content (adb) 1.49 - 15.62 %. Complete
coal quality data are listed in Table 3. This result
classified in SNI (Indonesian National Standard)
as high rank coal.
Gas Content Measurement
Since the gas was trapped inside coal cleats
and matrix, special methods to calculate gas
content have to be applied. This study measured
the gas content directly by collect the fresh coal
from core barrel and sealed it in canisters. The
gas was vent out from the canister in periodical of
time and the volume is measured and labelled as
Q2. From this Q2 data series, the lost gas volume
(Q1) was calculated by extrapolate the Q2 vs.
time graphic to initial time (first gas came out from
the coal). The gas that still saturated in coal push
out by crushed the coal; volume of the gas from
crusher chamber is measures to get the Q3. The
total gas in a bulk of coal calculates by summation
Q1, Q2 & Q3. A sample graphic of Q2 is presented
in Figure 3.
Canisters that were used in this study made
from PVC with HQ diameter and 60 cm length.
Properties of canister after filled with coal are
presented in Table 4. The coloured seam (E, I and
J) is the seam which gas volume was included in
resources potency calculations.
Q2 measurement graphic is vary for each
seam, there were some canisters that continuing
to produce gas (after 8 month) when others were
stop earlier and crushed to get the Q3. Some Q3
calculation in Table 5 generated by used Q3
data's from other canisters in the same coal
seam. This study is still in progress until there is
no gas came out from the coal.
The produced gas samples were collected
and analysed with GC in CGR mobile laboratory
(Figure 4). Further, the gas content data then
converted in to cubic-feet and presented in Table
6. Average methane content for each coal seams
(Table 7) and coal resources (Table 2) was used
to determine the coal bed methane content at
Tanjung Formation in Tanah Bumbu area (Table 8
and Table 9).
Total methane content of Tanjung Formation
in Tanah Bumbu Area between 300 to 1000
meters depth is 430,584,554.36 cu-ft (~430
MSCF).
cuft/ton, with the highest average methane
content 4.95 cuft/ton at I seam. This is caused by
sample depth which only 212.34 - 275.35 m. At
this depth, methane probably still going up
through overburden and release to atmosphere,
besides the meteoric water might still can reach
the coal seams. We believe that methane content
will increase if drilling reaches deeper coal seam.
This result can take as a minimum methane
content of the Tanjung Formation.
The deepest point of CSAT-1 drilling was
284.90 m, however in this study the methane
content measurement calculated for coal is at
300-1000 m depth. This calculation based on
assumption that 300 to 1000 meter is the sweet
spot for methane accumulation. As mention
above, shallow coal will give lower methane
content, while for coal deeper than 1000 m, the
cleat volume and permeability will significantly
decrease by the overburden pressure. Ideally, we
collect coal samples deeper than 300 m, but
drilling equipment limitation push us to make this
result as minimum methane content, not the
average methane content for Tanjung Formation.
Hopefully, in the future we can drill deeper and
collect more representative samples for this
formation.
With only one well, it is challenging to
evaluate the data for basin or even formation
scale that is why we restricted our study to some
thick coal seams from Tanjung Formation at
Tanah Bumbu area. For a detail prospection it is
better to have some drilling wells to get more data
and to be used as production/dewatering wells.
But, for CGR that have task to provide primary
data for the next exploration stage, this data can
give minimum estimation for methane content in
Tanjung Formation.
CONCLUSION
CGR as government institution provide
resource potency data in Tanjung Formation for
further follow-up. In Tanah Bumbu Area, South
Kalimantan, CGR drilled CSAT-1 to find methane
content in Eocene Tanjung Formation. Based on
the three main coal seam from exploration well,
the average methane content vary from 1.82 to
4.95 cu-ft per tons, whereas the total reach up to
430 MSCF of methane.
DISCUSSION
430 MSCF methane result is seems small
for production scale, but we should consider this
result is only for small part of the Tanjung
Formation's coal. The desorption test
measurement only reach its maximum at 6.3
Buletin Sumber Daya Geologi Volume 5 Nomor 2 - 2010
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MAKALAH ILMIAH
REFERENCES
Rustandi, E., Nila, E. S., Sanyoto, P. & Margono, U. 1995. Peta Geologi Lembar Kotabaru Kalimantan,
P3G.
Satyana, A. H & Silitonga, P. D. 1994. Tectonic Reversal in East Barito Basin, South Kalimantan:
Consideration of the Type of Inversion Structures and Petroleum System Significance. Proceedings
of the Indonesian 22nd Annual Convention.
Sikumbang N. 1986. Geology and Tectonics of Pre Tertiary Rocks in Meratus Mountains, South East
Kalimantan, Indonesia. Ph.D Thesis University of London.
Sikumbang, N. & Heryanto, R. 1994. Peta Geologi Lembar Banjarmasin, Kalimantan, P3G.
Tim Pemboran Tanah Bumbu. 2008. Laporan Pemboran Dalam dan Pengukuran Gas dalam Lapisan
Batubara Daerah Tanah Bumbu Provinsi Kalimantan Selatan, Pusat Sumber Daya Geologi
8
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