Methane gas potential of coal as national alternative energy reserves in Indonesia

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1 Proceeding of ISBN nd International Conference on Sustainable Energy Engineering and Application Grand Hotel Preanger, Bandung, Indonesia October 2014 Methane gas potential of coal as national alternative energy reserves in Indonesia La Ode Marzujriban a, *, Rahmat Hidayat a a Hasanuddin University, Jl. Perintis Kemerdekaan 10, Makassar 90245, Indonesia Abstract One of alternative energy reserves which has not been developed optimally is CoalBed Methane (CBM). Until now, the mining activity only performed on the surface of the coal seam and usually focuses on exploitation of the coal itself. So it need to do a variety of identification and innovation to extract methane gas that contained therein. As a big country that has complex geological setting, Indonesia has sizeable potential of coal that estimated also have a great potential for CoalBed Methane. Therefore, it necessary to do a study to know how big the CBM reserves in order to increase energy reserves and reducing fossil fuels (oil and gas) usage that the production gradually decreased. If we compared to the energy fossil, coal are still relatively abundant. Using Analysis of various studies and literature we found that Indonesia has quite significant reserves of CoalBed Methane approximately 450 Tcf with eleven basins that has been identified even been exploited with thickness average approximately 40 meters which is the one thickest coal layer of the Earth and some reference said that it more than that. So it can be added to the inventory of Indonesia s energy reserves and if it developed, it would improve national energy tenacity. Keywords: Alternative energy; coalbed methane; energy reserves. Selection and/or peer-review under responsibility of Research Centre for Electrical Power and Mechatronics, Indonesian Institute of Sciences 1. Introduction CoalBed Methane (CBM) is a form of natural gas that is found in coal seams and extracted by drilling wells into the coal seams. Unlike extraction of conventional gas, CBM extraction requires the removal of groundwater to reduce the pressure in the coal seam, which allows CBM to flow to the surface through into the well. This water must be managed and in several states, it sometimes permitted for discharge directly or indirectly (via a publicly owned treatment works [POTW] to surface waters (EPA [9]) Wells of CBM Construction of well ordinary for any well drilling operation (include CBM well) usually follows one of two basic types: open or cased hole. In open hole type, the well was drilled but no lining material is installed, so any gas can seep out all along the well into the wellbore for removal to the surface. Then in cased hole type, a lining was installed through all or most of the wellbore. These casings need to be perforated or slotted to allow gas to enter the wellbore for removal to the surface. Open hole type, which are less expensive then perforated or slotted completions, are used more often in CBM production than in conventional oil and gas production (Fig. 1), which use open hole completion only under certain limited circumstances (NaturalGas.org [4]). * Corresponding author. Tel.: -; fax: -. address: imaniban@gmail.com Indonesian Institute of Sciences, Research Centre for Electrical Power and Mechatronics Available online at

2 96 L. O. Marzujriban and, R. Hidayat / Proceeding of ICSEEA (2014) It show how CBM well working by through CBM reservoir and it will bring the gas which still mixed by water from the coal seam and it separated between the gas and the water, so the gas can be flow into the pipeline then the water will be remove into water storage (Al-Jubori et al. [2]). The mining was done by coal miners only performed on the surface of the coal seam and focuses on the exploitation of the coal itself while the coal seams in not yet fully exploited. This is influenced by cost factors and the risk of mining activities, so it needs to be done a variety of identification and innovations to extract methane gas contained therein, known as CoalBed Methane (Kristadi et al., 2012). Major CBM reserves (dark blue) are found in Russia, the USA (Alaska alone has an estimated 1,037 Tcf), China, Australia, Canada, the UK, India, Ukraine and Kazakhstan. Of the 69 countries with the majority of coal reserves, 61% have recorded some form of CBM activity investigation, testing or production. (US DOE [8] and BP Statistical Review [3]). Fig. 1. CBM extraction from the well [2]. Figure 2. CBM reserves and activity [3, 8]. International Conference on Sustainable Energy Engineering and Application (ICSEEA) Grand Hotel Preanger, Bandung, Indonesia, October 2014

3 L. O. Marzujriban and, R. Hidayat / Proceeding of ICSEEA (2014) Data and method For complete this study, there are several data source from many references, they are: Gas Metana Batubara (Kristadi et al., 2012). Introduction to CBM Technology (Abdassah [1]). Indonesia: CBM Indicators and Basin Evaluation (Stevens [7]). Oilfield Review Summer (Al-Jubori et al. [2]). Unconventional Oil and Gas Potential in Indonesia with Special Attention to Shale gas and CoalBed Methane (R.Sukhyar and R.Fakhruddin [6]) Gas generation related to coal rank Coal rank (Fig. 3) from the formation would have significant relation to the gas generation and it depend by coal buried time that respond to increase of depth, temperature and thermal maturity that would by qualifies the coal rank then the increased volumes of methane gas (Fig. 4). The figure show how the Coal Rank would take effect to Gas Generation and it shown that the Bituminous Coal rank would give maximum value for Gas Generation (Al-Jubori et al. [2]) Indonesian CBM Based on the literature we found that there are several location that have a Coal Basins that also CBM potential in Indonesia (Fig.5), summary of typical CBM properties in Indonesia (Table 1) also several summary of Coal Basin that prospected to CBM: Fig. 3. Coal rank [1]. Fig. 4. Gas Generation as a function of coal rank [2]. Indonesian Institute of Sciences, Research Centre for Electrical Power and Mechatronics

4 98 L. O. Marzujriban and, R. Hidayat / Proceeding of ICSEEA (2014) Based on Location that shown in the map (Fig. 5) and also the coal rank (Fig. 3) and the relation with the Gas Generation (Fig. 4), there are summarize of typical CBM reservoirs properties of it (Table 1). Fig. 5. Location of Indonesian coal basins with CBM potential [7]. Table 1. Summary of typical CBM reservoir properties [7]. Table 2. Coal Bed Methane resources of Indonesia [6]. International Conference on Sustainable Energy Engineering and Application (ICSEEA) Grand Hotel Preanger, Bandung, Indonesia, October 2014

5 L. O. Marzujriban and, R. Hidayat / Proceeding of ICSEEA (2014) Based on the map (Fig. 5) and the Summary of Typical CBM Reservoirs Properties (Table 1) we have found some summarize of prospect Coal Basin that contain CBM such us: South Sumatra basin CBM resources in South Sumatra were estimated volumetrically based on coal thickness and sorption isotherm data. We mapped and high-graded an 18,800 km2 area (19% of the basin) that appears to be the most prospective area, containing thick coals at target depths of 150 to 1,500 m. We used the following reservoir parameters to compute prospective gas in place. Depth-prospective area = 18,800 km2 (4.7 MM ac) Completeable coal thickness = 36.6 m (120 ft) Ash Content = 10% Moisture Content = 7.5% Coal Density = 1,800 tons/acre-ft CO2 Content = 3% CH4 Content = 7.0 m3/t (223 Scf/ton) Using standard volumetric computation, Gas in Place (GIP) = {120 ft x (1 0.1 ash) x ( moisture) x 1,800 ton/ac-ft x ( CO2) x 223 Scf/ton x 4,704,000 acres} = 5.2 x 1012 m3 (183 Tcf) (Stevens [7]) Central Sumatra basin The 80,000-km2 Central Sumatra basin contains thick coals in the Miocene-Pliocene Upper Petani (or Korinci) Formation. Other coal-bearing units include the Early Miocene Sihapas Formation and the Eocene- Oligocene Lower Pematang Formation, but these tend to be much too deep for CBM development. Net coal thickness reaches 30 m in places, of which 15 m may be completeable in a 3-frac CBM well. Coal rank is lignite to sub-bituminous with estimated gas contents of 4.5 m3/t (145 Scf/ton) at target depths of 750 m. Just as in South Sumatra, the structural depressions contain the thickest coal deposits, yet are seldom drilled and lack data control. Much of the coal resource is deeper than 1,500 m and may have low permeability. Central Sumatra is the site of Duri steamflood, a heavy oil field which consumes about 11 million m3/day of natural gas (400MMcfd). We estimate completeable CBM resources at 1.0 x 1012 m3 (34 Tcf), based on prospective areas of 13,350 km2, 15 m completeable coal thickness, coal density of 1,800 tons per acre foot, 10% ash content, gas content of 4.5 m3/t (145 Scf/ton), and 2% CO2 (Stevens [7]). Barito Basin. It estimate completeable CBM resources of 2.9 x 1012 m3 (102 Tcf) within a 16,000-km2 high-graded area of the south- central Barito basin. This area is characterized by 30 m of completeable coal thickness, depth of approximately 800 m, vitrinite reflectance of 0.45%, gas content estimated at 4.7 m3/t (150 Scf/ton), and low ash and CO2 contents (Stevens [7]) Kutei basin Located in eastern Kalimantan, the 100,000-km2 Kutei basin is a major oil and gas producing province. Like the Barito basin, the Kutei basin has thick (up to 50 m), gas charged coal seams at optimal depth over large areas. But it also has considerable bituminous coal deposits, with some of the highest ranks in Indonesia. Gas markets and operational logistics are more established. Folding and faulting is more prevalent, with numerous tight anticlines separating broader, flat synclines. The primary CBM targets are the Lower Miocene Kamboja and the Mid-Miocene Prangat Formations of the Balikpapan Group, which has up to 50 m of net coal dispersed amongst 10 coal seams, some of which are traceable over distances of 20 km (Stevens [7]). It estimate completeable CBM resources of 1.4 x 1012 m3 (51 Tcf) within a 15,600-km2 high-graded area of the eastern Kutei basin. This area is characterized by 21m of completeable coal thickness, depth of approximately 900 m, vitrinite reflectance of 0.5%, gas content estimated at around 6.1 m3/t (195 Scf/ton), and low ash and CO 2 contents (Stevens [7]) Berau basin Located just north of the Kutei basin in eastern Kalimantan, the smaller 10,000-km 2 Berau basin is a major coalproducing area but only a minor producer of oil and gas. Miocene coal seams in the Latih Formation total up to 150 m thick, some 6-9% of total formation thickness. The Eocene Sujau Formation also contains thinner coals. Rank is sub- bituminous to high-volatile bituminous. Structure is simple, with few folds and faults. Gas markets are limited. We estimate 0.2 x 1012 m3 (8 Tcf) of completeable CBM resources within a 780-km2 high-graded area of the southern Berau basin. This area is characterized by 30 m of completeable coal thickness, average target depth of approximately 700 m, vitrinite reflectance of 0.45%, gas content estimated at around 4.5 m3/t (144 Scf/ton), and low ash and CO2 contents (Stevens [7]) North Tarakan Basin Located in northeastern Kalimantan, the 45,000-km2 North Tarakan basin includes the Tidung and Tarakan sub-basins. The basin currently has limited oil and gas production onshore. CBM targets include the Miocene Meliat and Tabul Indonesian Institute of Sciences, Research Centre for Electrical Power and Mechatronics

6 100 L. O. Marzujriban and, R. Hidayat / Proceeding of ICSEEA (2014) Formations, which contain m of sub- bituminous to bituminous coal. Thick lignite with limited CBM potential also occurs in the Pliocene-Pleistocene Tarakan and Bunyu Formations. The Tabul Formation has an estimated 15 m of completeable coal thickness, including individual seams up to 6 m thick. (Stevens [7]).We estimate 0.5 x 1012 m3 (18 Tcf) of completeable CBM resources within a 7,000-km2 high-graded area of the eastern North Tarakan basin. This area is characterized by 15 m of completeable coal thickness, average target depth of approximately 700 m, vitrinite reflectance of 0.45%, gas content estimated at around 4.5 m3/t (144 Scf/ton), and low ash and CO2 contents (Stevens [7]). Other Basins. Indonesia has other coal basins with CBM potential, but they appear less prospective than the South Sumatra, Central Sumatra, Barito, Kutei, Berau, and North (Stevens [7]). Based on research by Advance Resource International, Inc, it found that Indonesia with estimated reserves of approximately 450 Tcf scattered in eleven coal basins have a good potential to be produced as well as stimulation of the three hydraulics in CBM wells that estimated to reach an average thickness of 40 m and it is thought to be the most thick and large layer in the world as target for CBM development (Kristadi et al., 2012). 3. Result and discussion Based on the data we found that the Coal Basin in Indonesia that prospect with CBM has spreaded in several big islands leading by Kalimantan Island with five coal basin with completeable coal thickness from 15 m to 28 m, Ro from 0.45% to 0.5%, average depth 671 m to 915 m, total of high graded area 16,329 km2 and total of completeable CBM resources is Tcf. For the Sumatra Island with 4 basins has the completeable coal thickness from 12 m to 37 m, Ro from 0.4% to 0.8%,average depth 610 m to 762 m, total of high graded area 13,319 km2 and total of completeable CBM resources is Tcf. Java island with one basin has the completeable coal thickness about 6m, Ro 0.7%,average depth 1,524 m, high graded area 100 km2 and total of completeable CBM resources 0.8 Tcf. Sulawesi island with one basin has the completeable coal thickness about 6 m, Ro 0.55%,average depth 610 m, high graded area 500 km2 and total of completeable CBM resources 3.6 Tcf. From the literatures we also got the information that based several study doing by some advance researcher it found that Indonesia have the thickest and largest CBM potency with 40 m thick by using Hydraulical simulation in several CBM wells. 4. Conclusions Conclusions of this study are Indonesia has a great potency of CBM with the CBM reserves will reach about 450 Tcf with an average thickness of 40 m which is thought to be the thickest and largest CBM potential layer in the world in eleven basins that scattered in almost all major islands in Indonesia with coal rank of Ombilin Basin became the highest with Ro values reaching 0.8% and significant values were also found in other basins that expected to have high gas volume. As well as in terms of area, south Sumatra basin area is an area that most prospects with high-graded areas that reach 7,350 km2 with completable area reach about 183 Tcf of CBM resources with Ro 0.47% but another basin based on the data also have promising potential so it need to be more developed to gain national energy tenacity. Acknowledgements The authors wish to thank to the lecturers of Hasanuddin University especially in Geophysics study program that has help author to fulfill and give a lot of contribution for this study. References [1] Abdassah, D., Introduction to CoalBed Methane Technology, Bandung Institute of Technology, [2] Al-Jubori, A. et al., Oilfield Review Summer, 21, 2, [3] BP Statistical Review of World Energy, TAGING/local_assets/downloads/pdf/statist ical_review_of_world_energy_full_ review_2008.pdf. [4] Naturalgas.org, Well Completion. ompletion.asp., [5] Ojha, K. et al., International Journal of Chemical Engineering and Applications, 2, 4, [6] R.Sukhyar & R.Fakhruddin, Unconventional Oil and Gas Potential in Indonesia with Special Attention to Shale gas and CoalBed Methane, Geological Agency, [7] Stevens, S., Indonesia: CoalBed Methane Indicators and Basin Evaluation, SPE proceedings, [8] US DOE Energy Information Administration, Coalbed Methane Proved Reserves and Production, m_a_epg0_r52_bcf_a.htm, [9] US EPA, CoalBed Methane Extraction. United States, International Conference on Sustainable Energy Engineering and Application (ICSEEA) Grand Hotel Preanger, Bandung, Indonesia, October 2014