Muaraenim Formation Research Articles

Evolution of Sequence Stratigraphy and Paleogeography, Case Study: M2 Member of the Muara Enim Formation

Sequence stratigraphy related to accommodation space as an area of potential sediment accumulation that is influenced by fluctuations in sea level and subsidence of the basin floor. Paleogeography, on the other hand, is the study of physical geographic features and their evolution throughout geological periods. The aim of this work is to shed light on the relationship between paleogeographic evolution and sequence stratigraphy, as well as coal accumulation in the South Sumatra Basin. The method used are geophysical logs and cores analysis to determine the system tracts, types of system tracts, and stratigraphic sequences, lithofacies and sedimentary facies analysis, paleogeographic analysis using modified single-factor and multi-factor and them mapped using IDW as a geostatistical method. The results indicate that the study area comprises four system tracts, namely TST-1, HST-1, TST-2 and HST-2. In TST-1 and TST-2, the rate of peat formation is balanced with the rate of accommodation space formation, resulting in continuous and very thick coal accumulation. In HST-1 and HST-2, the rate of accommodation space formation exceeds the rate of peat formation, leading to continuous coal accumulation that is quite thick to very thick. Sequence 1 consists of lagoon and tidal/mouth/distal bar paleogeographic unit with sand/shale ratio range 0.217 to 0.247. Sequence 2 consists of lagoon paleogeographic units with sand/shale ratio range 0.046 to 0.05.

Transgression patterns of Muara Enim Formation at Tanjung Agung Village based on stratigraphic data measurements

Abstract Muara Enim Formation is one of the formations which is composed in the South Sumatra Basin in the Late Miocene Epoch. It has a specific lithology which shows how the conditions of the depositional environment were the formation was deposited. The purpose of this research is to determine the pattern of transgression and regression of Muara Enim Formation. Transgression and regression patterns are used to determine how the shoreline moves. It is caused by the supply of sediment material. The finer sediment material is deposited and the smoother the movement of the material towards the land, showing the indication of transgression, and vice versa. This research uses analytical-interpretative as the method, which is using the result of sampling analysis and then interpreting how the pattern of transgression and regression are changed. This method is used to determine the physical properties of the lithology composing the Muara Enim Formation. Based on field observations on the Air Enim River, it is known that the Muara Enim Formation is composed of lithology dominated by fine grain size (claystone) to medium grain size (tuffaceous sandstone) with thin coal in several locations. Based on field outcrop (surface data) it is known that the claystone lithology is thickened to a younger layer (about 2.5 m thickness) with massive sedimentary structure. It is interpreted that the Muara Enim Formation was deposited in a transgression pattern in a depositional phase which was influenced by sediment supply factors and weak depositional currents.

CHARACTERISTICS, RANKING, AND POTENTIAL OF COAL ON SEAM H AND SEAM H2

Coal is a complex solid object consisting of several chemical elements and comes from plants that are deposited in a basin. The South Sumatra Basin is a basin with the presence of the Muara Enim Formation which is known as a coal-bearing formation. In this research, secondary data was used in the form of proximate analysis, ultimate analysis, and combustion properties analysis results in determining the characteristics, ranking, and potential of coal in the research area. Based on ASTM D 388 – 05 classification, coal in seam H has a Subbituminous B Coal ranking, while seam H2 has a Subbituminous A Coal rating. Based on the parameters in assessing the coal potential use for coal-fired power plants according to Thomas, 2013 in Suhat, et al., 2020, coal in seam H and seam H2 does not support the utilizations, but solutions can be carried out in the form of rewashing sample, coal drying, and coal blending.

GEOLOGICAL INTERPRETATION OF 2D GRAVITY MODELING IN TULUNG SELAPAN AREA AND SURROUNDINGS, SOUTH SUMATRA BASIN

The South Sumatra Basin is a prolific oil and gas basin. The Tulung Selapan area, which is to the east and part of the South Sumatra Basin, is considered to have hydrocarbon potential. Several sub-basins, including the South Palembang and the North Palembang sub-basins, exist in the region. One of the geophysical methods for determining the presence of sedimentary sub-basins, structural patterns, and bedrock is the gravity method. The purpose of this study is to determine the structural pattern and interpret the subsurface geological model of the Tulung Selapan area using 2D modeling. The complete Bouguer anomaly (CBA) reveals circular and relatively northwest-southeast trending patterns, ranging from +33 mGal to +62 mGal. 2D gravity forward modeling results in eight successive rock layers. From top to bottom, the uppermost layer is swamp sediment with a mass density of 2.1 g/cm3, followed successively by the sedimentary rocks of the Kasai Formation (2.28 g/cm3), the Muara Enim Formation (2.32 g/cm3), the Air Benakat Formation (2.39 g/cm3), the Gumai Formation (2.3 g/cm3), the Baturaja Formation (2.48 g/cm3), and lastly a layer with a density of 2.7 g/cm3, which represents the bedrock. Due to the limited depth of 2800 m in 2D forward modeling, it is unable to identify the source and reservoir rocks. The seal rock (caprock) is interpreted to be shale from the Gumai Formation at an average depth of 1.53 km. Based on Second Vertical Derivative (SVD) analysis, 2D modeling identifies the presence of geological structures with normal faults.

EVALUATION OF COAL DISTRIBUTION FOR ALTERNATIVE ENERGY USING SEISMIC SPECTRAL DECOMPOSITION

Indonesia is the largest coal producer in the world, and Sumatera is one of the contributors to Indonesia's coal production. Coal is generally widely used for industrial fuel or power plants with production directly on the surface. The technology to develop coal into alternative energy sources (Coal Bed Methane (CBM) & Underground Coal Gasification (UCG)) began to develop with various production methods in the earth without having to be exploited directly. To apply this production method, it is necessary to analyze the distribution of coal below the earth's surface. The research area is located in the South Sumatera Basin with coal targets in the Muara Enim Formation. The data consists of 3D seismic data and well data as validation. From the well data, it was identified that there was coal in two zones, with an average thickness in Zone A reaching 6 meters while in Zone B the average thickness reaching 11 meters. The results of the amplitude spectrum analysis from the seismic data, obtained three dominant frequency trends from seismic data, 26 Hz, 42 Hz, and 58 Hz. By using the calculation of ¼ wavelength, the frequency that matches the thickness of the coal is 58 Hz for Zone A and 42 Hz for Zone B coal layer. Seismic amplitudes are then separated based on their frequency using the Spectral Decomposition method, and the distribution of coal is validated with existing well data.

Modelling and Estimation of Coal Resources Using Circular Method in Beringin Makmur II Area, North Musi Rawas Regency

The Muaraenim Formation is a coal-bearing formation located in the South Sumatra Basin. The research location is in the Beringin Makmur 2 area, North Musi Rawas Regency, which is included in the Airbenakat and Muaraenim Formations. The aim of this research is to do 2-dimensional and/or 3-dimensional modeling in the research area to determine the feasibility of the mining process. The feasibility test of a coal seam body will be used as a study for the next stage, namely resource estimation. The method for calculating coal resources is the USG circularS method based on drill log data. The following data is needed, such as drilling data for 64 drill points, regional geological data and survey data at the research location or mining business permit (IUP) location. Then an analysis will be carried out so that 3D subsurface modeling and calculation of coal resources can be continued. Based on the research results, it was found that there were 3 coal seams with updip in the north direction and downdip in the south direction N1800E - N1820E. In the research area, synclines were found that affected the distribution of coal. Interpretation of the 3D model is obtained from the correlation between drilling data and survey data. The results of the calculation using the USGS circular method, the estimated tonnage of inferred resources is 91,840,000 tons, indicated resources are 55,330,000 tons, measured resources are 235,870,000 tons so that the overall estimate of the coal seams is 383,040,000 million tons/ton.

The Role of Inertinite Characteristics and Coal Porosity of Seam A-1 of Muara Enim Formation in West Merapi, Lahat, South Sumatera, Indonesia

Coal contains a complex network of nano-, meso-, and a macro-pore can store fluids and allow fluids to flow through it. Nanoporosity in coal is primarily a result of molecules that have aromatic molecular structures and have been preserved in coal. Most adsorbate compounds, including gases, are stored here. The study area is located in South Sumatera, West Merapi Area, Lahat Regency. Geologically, the area in South Sumatra Basin belongs to the Middle-Late Miocene Muara Enim Formation. Using the ply-by-ply method, coal samples were taken directly from Seam-A in the coal mine walls outcrop, based on macroscopically determinable lithotype information. During laboratory analyses, coal is microscopically analyzed to determine the amount of porosity, permeability, and vitrinite reflectance. The purpose of this study is to investigate the change in composition and characteristics of inertinite macerals when the porosity value is varied.. Vitrinite content is between 91.00-92.80 %; liptinite 0.90-3.40%; inertinite 3.70-4.80%; mineral matter 0.7%-1.8%. Withh a vitrinite reflectance average of 0.34-0.36%, the variation in composition is an indication of changes in plant communities or coal facies. It is generally classified as sub-bituminous coal (ASTM). Porosity value of seam A upper is 1.9% and seam A lower 1.51%, permeability value seam A upper is 70.1 mD and seam A lower 27.1%. Composition of mineral matter in seam A upper is 0.8% and seam A lower 1.7%. The increasing number of inertinite pore is followed by lower porosity value. The inertinite maceral is predominantly aromatic with a high level of cross-linking, and exhibits a high level of aromatization and condensation. They have the highest carbon and the lowest oxygen hydrogen content. A coal maceral's porosity is composed of void spaces, such as open cell lumens preserved in semifusinite and sclerotinite. The porosity of cleats is the percentage of volume in relation to volume of coal, and the porosity of permeability. In coal, semifusinite has extensive interconnected pores that can form significant conduits for fluid flow.

ON GOING COALBED METHANE (CBM) DEVELOPMENT IN THE SOUTH SUMATRA BASIN

Coalbed methane (CBM) is going to be an important facet of the nation’s energy mix. It is expected to contribute in importance energy back up for the future. CBM is natural gas, a clean-burning energy source that is reservoired in a coal seam. CBM is formed during the coal maturation process and may in a free or adsorbed state in coal seams in adjacent formations. CBM is dominantly methane but lesser concentrations of carbon dioxide and nitrogen, compare to conventional natural gas. However, in most cases, CBM is of sufficient quality for sale directly into natural gas transmission lines with a limited amount of moisture removal.CBM as natural gas has numerous benefits to include direct selling, well suited as city gas, electricity generation, boiler fuel, transportation fuel, and for many types of chemical industries feed. Beside CBM replaces coal to be greatly reduces the production of acid rain and other forms of air pollution, the development of CBM has benefitial for coal miners. It can contribute to improved mining safety as well as it can help reduce construction costs.CBM is probably one of the promising alternative fuel energy resources in Indonesia that its presence is actual and comparable with the existing coal resources in any potential basin. Unlike some well in developed countries where commercialization of methane production from coal seam has been developed, coals direct mined in Indonesia seem to be more attractive and preferable technique to supply the consumer demand of energy. This is because coal mines serve direct products, less complicated technology, low exploration risks, easy recovery, relatively low cost but quick yields and already have wide market. Consequently, people have overlooked the existence of consisting huge potential methane gas in coals.However, petroleum exploration data throughout Indonesia suggest that increasing coal rank occurs rapidly with depth in many basins and that gas kicks are almost common associated with some coal seams below 200 m depth. In addition, world CBM exploration now has shifted towards lower rank settings (i.e, vitrinite reflectance between 0.3% and 0.6% Ro). In Indonesia, thick coals generally are found at greater depth, higher in rank and therefore are expected to be more productive (Saghafi and Hadiyanto, 2000).LEMIGAS is currently conducting a drilling program to study the feasibility of CBM production in South Sumatra. The domain of the work is in the Muaraenim Formation (Upper – Middle Palembang). The coal sequences were deposited during Late Miocene. We believe that a big effort is extremely essential to establish the reserve and economic potential of CBM in South Sumatra to later extent to Indonesia.

Coal Geometry Modeling and Resources Estimation in Darmo and Surrounding Area, Muara Enim, South Sumatra

This research is located in Darmo, Muara Enim, South Sumatra, while in geological spatial it is located in the Muaraenim Anticlinorium zone. The purpose of this study is to build coal geometry model and calculating coal resources estimation in the study area. The methods applied in this study include field observations, laboratory analysis and studio analysis. Coal geometry modeling is doing by krigging method, as well as the calculation of coal resources using the circular method. The results obtained from this study are in the form of stratigraphic sequence of the youngest namely the Kasai Formation and the Muaraenim Formation. Geometry of coal seams in the study area has a thickness that is quite varied from 0.5 meters - 12.8 meters, in general is continuous, has the characteristics of the roof and floor in the form of sandy coal and muddy coal and interburden in the form of sandstone and claystone. The form of coal seams in the study area is included in the classification of horseback, fault and fold. Estimated coal resources in the study area consist of inferred resources 74677959 m3 or equivalent to 104549142 tons, indicated resources 69043012 m3 or 96660216 tons and measured resources 68041837 m3 or 95258571 tons which is a calculation of estimated coal resources from seam A, seam B, seam C and seamless C and seam D.

Quality of coal seam D of Muara Enim Formation, Central Palembang Subbasin

Coal seam D belongs to Muara Enim Formation in Central Palembang Subbasin, South Sumatera Basin, which ages of Middle Miocene to Late Miocene. This study aims to determine the quality of the coal, especially sulphur content and form, ash content and composition, and trace elements of heavy metals. Those are important to know as a reference in suitability in the use of this coal. Methods of analysis is proximate, total of sulphur, form of sulphur, SEM-EDS, ash composition, and trace element. The coal is categorized as low rank coal or lignite with a very low total sulphur max 0.25%, dominated by the organic sulphur formed during the peatification and coalification process (syngenetic). The coal has a safe ash composition. It shows from a very low metal oxide content that causes slagging and fouling at low temperatures process. Likewise, the trace element content of the coal such as chromium (Cr), cadmium (Cd), manganese (Mn), lead (Pb), nickel (Ni) is still far below the threshold for trace element content in coal.

Coal Characterization of South Sumatera Basin using the Unsupervised Machine Learning Method

South Sumatra Basin is one of the sedimentary basins in Indonesia which has coal bearing formation, coal-bearing formations are rock formations that have coal layers in its area. Numerous coal proximate data (free moisture, total moisture, moisture, inherent moisture, ash content, fixed carbon, sulfur content) and ultimate data (carbon (C), hydrogen (H), oxygen (O), nitrogen (N) have been collected in this basin. This study aims to determine the characterization of coal in the South Sumatra Basin based on the proximate data and ultimate data using the unsupervised machine learning methods. The machine learning method has several basic concepts, namely being able to predict data by studying several patterns and factors that have been trained in a short amount of time. The study able to cluster coal in the basin into two cluster of coals with striking difference. The distribution of the two coal clusters in the South Sumatra Basin possibly influenced by the age of the formation in the South Sumatra Basin. In the first cluster, it is distributed in the older Airbenakat Formation and Muaraenim Formation, while in the second cluster it is scattered in the younger Muaraenim Formation and the Kasai Formation. The formation ages of the youngest are the Kasai Formation, the Muaraenim Formation, and the Airbenakat Formation.

Study of Ash and Total Moisture Effects on Calorific Value in Coal Seam at West Banko Field, PT. Bukit Asam, Tbk., Tanjung Enim, South Sumatra

In the coal mining industry, the coal quality is as crucial as the coal quantity because it can impact the coal usefulness. The quality of coal itself can be influenced by several factors, such as moisture content, ash, sulfur, and volatile matter. This study tries to understand the coal quality and its variation in the Muara Enim Formation of South Sumatra Basin. The research was conducted in the West Banko field, PT. Bukit Asam, Tbk., Tanjung Enim, South Sumatra. By using linear regression, this study found that increasing ash and total moisture content will lead to a decreasing amount of the calorific value. Additionally, the value of coal quality content such as ash and total moisture can be affected by the depositional environment, sedimentation rate, and coal characteristics in the study area thus affecting the calorific value. Transitional lower delta plain depositional environment with low sedimentation rate and coarsening upward sandstone sequence indicates lower ash and total moisture content in the study area. The highest calorific value found in the study area is in C1 seam, this can be seen from the ash quality and total moisture distribution map which inversely proportional to the calorific value.

THE ZONATION OF COAL RANK IN MUARA ENIM FORMATION BASED ON THE REFLECTION STUDY

Coal is a sedimentary rock containing approximately 50% to 70% carbon derived from the accumulation of plant residue that had undergone chemical and physical changes. In this research, the petrographic analysis method of coal was conducted based on the following parameters, measuring vitrinite reflectance (Ro%), estimation of moisture, volatile matter, and carbon-hydrogen content. This study aims to determine the zonation of coal rank through the vitrinite reflectance analysis in Maura Enim Formation. The samples observed were obtained from the Muara Enim Formation, which had undergone certain geological events to form lignite and anthracite coal ranks, then analyzed using the descriptive method. The results showed that the reflectance value of vitrinite was between 0.20% - 0.44%, which was utilized in the sorting of coal from lignite - sub-bituminous, according to ASTM D2798-06 (2006). Furthermore, in the Southwest region, coal is formed through greater pressure than those in the Northeast. Generally, the level of difference is caused by pressure, temperature, and time factor. Therefore, this study is recommended as a guideline in determining coal rank through vitrinite reflectance analysis in different formations.

Cleat properties of the Tanjung Agung coalfield, South Sumatra Basin: implications to fluid flow

Observation of the coal cleats of the Muara Enim Formation in Tanjung Agung coalfield aims to characterize the cleat properties and interpret their implications for fluid flow. This study used the scanline method to measure cleat attributes in the form of orientation, aperture, spacing, filler, and cleat connectivity. The face cleat was dominated by NE-SW direction as an indication of the effect of paleostress, while butt cleat with NW-SE direction indicated the effect of stress release. The presence of one major fault and three minor faults trending NW-SE in the mine pit is interpreted as the main controlling factor for cleat development in the study area. These cleats have an aperture ranging from 0.4 - 2.3 mm, good connectivity, and are not filled, so they are considered to be analogous to fluid flow paths with transition and turbulent flow types with relatively NE-SW direction.

Subsidence and heat propagation modeling on the underground coal gasification (Case study at Muara Enim Formation, South Sumatera)

One of the important issues to study underground coal gasification (UCG) is the prediction of surface subsidence. Several parameters that influence these conditions are the thickness of cap rock, the physical and mechanical characteristics, the structure condition, the minerals composition of the rock, and external conditions. This study had been carried out simulation and modeling to determine the level of surface subsidence risk and the effect of high temperatures due to the activities. The modeling results show that the thickness of the rock above the UCG coal seam greatly affects the surface subsidence. The depth is more than 200 m and found that the SF value is 1.59 which indicates UCG reactor depth of ≥ 200 m is safe from the risk of subsidence. From the characteristic aspect of the cap rock, the claystone types which not contain kaolinite minerals are more prone to collapse than those of contain kaolinite minerals. From this models, the gasifier at 150 m depth was estimated that there will be a decline of -7.23 m, and the minimum subsidence is at 275 m about 0.1 m. The heat propagation modeling results show that at 50 m the temperature is estimated to be 213- 289°C, but if the thickness of the cap rock is > 200 m depth, the temperature is around 29-28°C.

Macrolithotype and gas content of shallow low-rank coal of Muaraenim Formation at Musi Banyuasin, South Sumatera Basin

The macrolithotype method has already proven as an early method to determine high-rank coal gas content which is related to organic and inorganic materials, and also coal diagenesis level. This study aims to determine the relationship between macrolithotype and shallow low-rank coal gas content in Muaraenim Formation. Based on analysis result, coal seams exposed at depth of <300m have thickness varying from 0.5 to 10m. All seams in the research area were present in the Late Miocene and classified as lignite. Macrolithotype coal varies from durain - bright clarain with bright band percentage reaching 90%. Petrographic analysis showed that vitrinite reflections ranged from 0.24 to 0.36%. Proximate analysis showed that moisture content ranged from 10,64-12,9 wt.%, volatile matter 40,83-44,96 wt.%, and calorific value 4509-6035 kcal/kg and also Ultimate analysis showed that carbon content 72,48-74,02 wt.%. Gas desorption showed that gas content per seam varies from 0.27-29,84 scf/ton. According to the result between bright band vs depth and gas content vs depth, there was no relation between bright band and gas content due to very poor trend line value. This result was probably due to the low level of coal diagenesis that the bright band content did not show a linear trend line.

Macerals Analysis Seam M2 Muaraenim Formation, : Implication Toward Coal Facies and Coal Rank in Kendi Hill, South Sumatra

The Muaraenim Formation is a coal bearing formation in South Sumatra Basin of the Late Miocene – Pliocene. Shell (1978) divides this formation based on coal seam content are: M1, M2, M3, and M4. Coal seam in this area include in seam M2 member, with the general characteristics of the presence of silicified coal on the roof and floor of coal seams as a marker. The administration of the research area is located in east Kendi Hill, South Sumatra. The Kendi Hill is composed of adesite igneous rocks that intruded Muaraenim Formation in unconformity at the time of Pleistocene. This study aims to determine the environment of coal depositional based on maceral analysis and determine the factors influence the physical characteristics of coal seams in Kendi Hill. Data that has been obtained from the field, then conducted a selection process. The number of samples analyzed were nine sample based on near and far to the Kendi Hill spread from the southern, central, and northern of the location. The result of the analysis will display the maceral diagram. Megascopically, coal seam in the Kendi Hill are black, dull with bright, uneven – subchoncoidal, blackish brown in streak, have a pyrite and resin. The thickness of the coal seams ranges from 0,45 to 14 meters. Based on the maceral analysis, the coal seam in the Muaraenim Formation is composed dominated by vitrinite, then liptinite, inertinite and mineral matter pyrite (1,6-6,6%). Vitrinite reflectance of coal in the research area ranges from (0,37-0,48%) that included to the Sub bituminous – High Volatile Bituminous C. From the results of Tissue Preservation Index and Gelification Index value indicated that the environment of coal depositional in the research area was a limnic to wet forest swamp. Whereas the deposition of the Muaraenim Formation in deltaic environment (Transitional lower delta plain).

Characteristics of Coal and Cleat Attributes in Ulak Lebar and Surroundings Area, Lahat Regency, South Sumatra

The research conducted in Ulak Lebar Area, Lahat Regency, South Sumatra. The focus of this study is on the Muara Enim Formation as it is known as the main coal-bearing formation in South Sumatra Basin. The research is aimed to determine the characteristics of coal based on its physical properties, also knowing the cleat development at the coal seam in the research area. The methods used such as literature study, field observation and laboratory test. Field observations included the observations of coal megascopic appearance and cleat attributes analysis such as the measurements of cleat orientation, aperture, spacing and length. The analysis result of cleat at LP 2A and LP 2B shows a relatively similar such as spacing value ranged between 6 - 9 cm and 5.5 – 8.6 cm while the aperture value ranged from 0.05 - 0.2 cm, and 0.05 - 0.25 cm, whereas at LP 67 the spacing value ranged from 1.5 to 3.3 cm and the aperture valued between 0.1 - 0.3 cm. A rather significant difference between the cleat spacing values of LP 67 towards both previous observation stations is indicated by the geological processes occurred during the coalification process thus affected the development of cleats in coal, the geology structure control is characterized by a relatively large aperture and smaller spacing values. The laboratory test conducted is maceral analysis, shows the coal in the research area is dominantly composed of vitrinite (74,8%) and the vitrinite reflectance value is 0,40 indicating the coal classified as sub-bituminous rank.

A Comparison between Model Base Hardconstrain, Bandlimited, and Sparse-Spike Seismic Inversion: New Insights for CBM Reservoir Modelling on Muara Enim Formation, South Sumatra

Coal Bed Methane (CBM) as a newly developed resource in Indonesia is one of the alternatives to relieve Indonesia’s dependencies on conventional energies. Coal resource of Muara Enim Formation is known as one of the prolific reservoirs in South Sumatra Basin. Seismic inversion and well analysis are done to determine the coal seam characteristics of Muara Enim Formation. This research uses three inversion methods, which are: model base hard- constrain, bandlimited, and sparse-spike inversion. Each type of seismic inversion has its own advantages to display the coal seam and its characteristic. Interpretation result from the analysis data shows that the Muara Enim coal seam has 20 (API) gamma ray value, 1 (gr/cc) – 1.4 (gr/cc) from density log, and low AI cutoff value range between 5000-6400 (m/s)*(g/cc). The distribution of coal seam is laterally thinning northwest to southeast. Coal seam is seen biasedly on model base hard constraint inversion and discontinued on band-limited inversion which isn’t similar to the geological model. The appropriate AI inversion is sparse spike inversion which has 0.884757 value from cross plot inversion as the best correlation value among the chosen inversion methods. Sparse Spike inversion its self-has high amplitude as a proper tool to identify coal seam continuity which commonly appears as a thin layer. Cross-sectional sparse spike inversion shows that there are possible new boreholes in CDP 3662-3722, CDP 3586-3622, and CDP 4004-4148 which is seen in seismic data as a thick coal seam.

Characterization of Coal Quality Based On Ash Content From M2 Coal-Seam Group, Muara Enim Formation, South Sumatra Basin

Muara Enim Formation is well known as coal-bearing formation in South Sumatra Basin. As coal-bearing formation, this formation was subjects of many integrated study. Muara Enim Formation can be divided into four coal-seam group, M1, M2, M3, and M4. The M2 group comprising of Petai (C), Suban (B), Lower Mangus (A2), and Upper Mangus (A1). Depositional environments of Group M2 is transitional lower delta plain with sub-depositional are crevasse splay and distributary channel. The differentiation of both sub-depositional environments can be caused the quality of coal deposit. One of quality aspects is ash content. This research conducted hopefully can give better understanding of relationship between depositional environments to ash content. Group M2 on research area were found only Seam C, Seam B, and Seam A2, that has distribution from north to central so long as 1400 m. Coal-seam thickness C ranged between 3.25-9.25 m, Seam B range 7.54-13.43 m, and Seam C range 1.53-8.37 m, where all of coal-seams thickening on the central part and thinning-splitting to northern part and southern part. The ash content is formed from burning coal residue material. Ash contents on coal seam caused by organic and inorganic compound which resulted from mixing modified material on surrounded when transportation, sedimentation, and coalification process. There are 27 sample, consists of 9 sample from Seam C, 8 sample from Seam B, and 10 sample from Seam A2. Space grid of sampling is 100-150 m. Ash content influenced by many factors, but in research area, main factor is existence of inorganic parting. Average ash content of Seam C is 6,04%, Seam B is 5,05%, and Seam A2 is 3,8%. Low ash content influenced by settle environment with minor detrital material. High ash content caused by oxidation and erosional process when coalification process. Ash content on coal in research area originated from detritus material carried by channel system into brackish area or originated from higher plant in brackish area. The high ash content also can be caused by after the coal deposited. It had originated from overburden horizon which infill in cleat of coal seam.