Southeast Sumatra Research Articles

Lithium enrichment in high-enthalpy geothermal system influenced by seawater, Indonesia

Lithium holds significant importance in energy storage and can be extracted from geothermal water, making it an additional resource to traditional mining. Combining lithium extraction from geothermal water with electricity generation from geothermal energy offers a compelling strategy to address future energy challenges. Situated in Southeast Sumatra, Indonesia, Way Ratai has considerable geothermal potential and is known for its hot springs. This study primarily aims to characterize lithium enrichment within the Way Ratai geothermal system. Water samples from various sources (one spring, seven hot springs, one well, and seawater) were analyzed for cations, anions, trace elements, and isotopic composition. The results show that Way Ratai is an old geothermal system with sodium-chloride water, where lithium enrichment is attributed to interactions between water and rocks, with some influence from seawater. The discrepancy between calculated and observed magnesium (Mg) concentrations suggests a pre-heating mixing process between rainwater and seawater. The reservoir rock in Way Ratai is mostly andesitic, with temperatures ranging from 182o to 227oC. This study enhances our understanding of thermal water characteristics, reservoir temperatures, and water origins in high enthalpy geothermal systems, offering valuable insights into lithium enrichment in coastal geothermal regions.

Lithofacies, Facies Association, and Depositional Environment of 34-1, 33-6, and 33-4 Sandstone, Wida Field, Gita Member, Talang Akar Formation, Asri Basin, Offshore Southeast Sumatra

Three Gita Member reservoirs 34-1, 33-6, and 33-4 produce from solution gas drive with rapid pressure decline and low recovery factor. After successful oil production enhancements through waterflooding injections prompt the need for a reservoir model in further field development. Before such models were built reservoir characterization was carried out to determine facies and depositional environment for facies modeling. The study integrated core, wireline log, petrophysical logs, seismic attribute, petrography, etc. Next, well correlation was carried out to distribute stratigraphic markers. Finally, seismic attribute and well correlation were integrated to construct pie chart and depositional environment map. External geometry from seismic attribute revealed distributary channel with point bars which act as reservoir and consist of medium-fine grained planar tabular cross bedding sandstone, mud drapes sandstone, and ripple-wavy lamination sandstone. The wireline log showed fining-upward pattern and core displayed abundant channel rip up clasts, sharp or erosional contact with underlying lithology. Frequent mud drapes found within channel sandstone indicate tidal influence in proximity to marine environment probably in lower delta plain. Channels are trending west-east (34-1) and north-south (33-6 and 33-4). Other facies associations are shallow marine, swamp, interdistributary bay, and tidally influenced interdistributary bay. Shallow marine FA consists of skeletal limestone (Lm), calcareous mudstone, and calcareous sandstone (Sc). Rootlet mudstone (Fb) and interlamination of carbonaceous mudstone with very fine-grain sandstone (Fl) formed interdistributary bay FA. Swamp FA consists of coal and coaly mudstone. Tidally influenced interdistributary bay FA consists of carbonaceous laminated mudstone high in carbon (Flb), intensely bioturbated carbonaceous mudstone (Flb), very finely laminated mudstone-very fine grain sandstone (Fl) and black fissile shale (Fm).

Radiogenic geothermal systems of Bangka Island, Indonesia: Implications of high heat production and tectonic framework

The presence of geothermal manifestation in Bangka Island (Southeast Sumatra, Indonesia) with the absence of Quaternary volcanic activity and also relatively low seismicity events has raised intriguing questions on the control of the geothermal system in this area. As the regional tectonic setting of Indonesia volcanic geothermal systems has been known, that of non-volcanic geothermal systems such as radiogenic system become an issue to be investigated. This study reports the geochemistry and petrography analysis of Triassic granite related to radiogenic production at the vicinity of hot springs in Bangka Island. Surface temperatures of the Bangka hot springs range from 37 to 70.7 °C and pH values vary between 5.6 and 7.5. These hot springs are discharging either in close to massive granite bodies or occur in between two major NE-SW striking faults zones, i.e., Pemali fault and Payung fault. Our results indicate the average radiogenic heat production of Late Triassic Klabat granite in the northern area ranges from 28.5 to 38.34 μWm−3 and the southern area ranges from 28.3 to 49.5 μWm−3. In comparison to similar granite belt located in Malaysia, heat production of granitoid in Bangka hot springs is four times higher, possibly due to their different granite origins.

LOW RESISTIVITY PAY DEVELOPMENT: CASE STUDY OF TALANGAKAR FORMATION ASRI BASIN, OFFSHORE SOUTHEAST SUMATRA, INDONESIA

Southeast Sumatra is a prolific oil and gas block located offshore in the Java Sea, 90 km north of Jakarta Bay. This area covers two major basins, namely Sunda Basin and Asri Basin. The initial development of the area focused on faulted and high closures and high-resistivity reservoirs. Further analysis shows that there are special low-resistivity reservoirs in Widuri Area, especially in the Aryani field. This paper will discuss the low resistivity pay zone reservoirs and fluid containment of the intervals. The paper will also include further assesment this undeveloped interval to increase oil production, considering the upside potential of the reservoirs using current geological, geophysical, and reservoir engineering approaches. Additionally, it will describe the operational challenges faced during the production period. The low-resistivity pay zone, a hydrocarbon-bearing reservoir in the Aryani field of the Widuri area, was identified using gas readings in the daily drilling reports, complemented with mud logging data. The Basal Sand interval, which drapes above the basement, was the site of the first producing well of Basal Sand, Aryani AC-X, preceded by a hydraulic fracturing job. Lambda-mu-rho inversion was implemented to delineate this reservoir. To recognize the potency in those wells, data reconfirmation was conducted between the elan summary, sidewall core, and cutting data. Aryani AC-X has successfully drained oil using a submersible pump, with an initial production of 408 bopd and cumulative production of 240 MBO.

Study on The Design of Solar-Wind Energy System to Reduce The Use of Gas Fuel in The Southeast Sumatra Block

The Southeast Sumatra block produces oil and gas. Natural gas production of 15,300 MSCF is used as fuel for turbine generators to generate 38 MW of electrical energy, while the rest is used as business products. The application of the solar-wind system can reduce the load on the turbine generator so that gas fuel consumption is also reduced. Five platforms have areas that can be utilized for a solar-wind system. This study aims to determine the amount of gas fuel consumption that can be reduced by the solar-wind system application. The method is simulation using the HOMER software to determine the amount of electrical energy that can be supplied and the costs required by the solar-wind system. The components used are found in the HOMER software and on the market. The simulation results show that the off-grid solar-wind system can provide electricity supply of 50,235 kWh per year and reduce gas fuel consumption by 20,094 MSCF per year. The on-grid solar-wind system can provide electricity supply of up to 81,230 kWh per year and reducing the use of gas fuel by 32,492 MSCF per year. The off-grid solar-wind system will increase gas sales by $132,620 per year with NPV>0 and ROI 21%, while the on-grid system will increase gas sales by $214,447 per year with NPV>0 and ROI 57%. Both models of solar-wind systems have positive economic values ​​so that they are feasible to implement

Seismic Expression of Paleogene Talangakar Formation - Asri & Sunda Basins, Java Sea, Indonesia

The Asri and Sunda Basin are located offshore Southeast Sumatra under the SE Sumatera Production Sharing Contract (PSC). Currently, Pertamina Hulu Energi OSES operates in the Asri and Sunda Basins, known as Southeast Sumatra (SES) Block. As one of Indonesian prime oil and gas producing area in the past 50 years, these basins have produced cumulatively more than 1,500 MMBOE with an average of 90,000 BOPD. Both Asri and Sunda Basins are part of a series of Cenozoic half grabens developed on the Asian continental margin, that have occupied a retro arc setting since early Neogene times.Hydrocarbon exploration activities in the offshore southeastern Sumatra began with a signed agreement of Contract Sharing between IIAPCO (Independent Indonesian American Petroleum Company) and Pertamina on 6 September 1968.The contract area included the offshore areas east of Sumatra and south of Bangka - Belitung Islands, covering an area of 124,000 km2. After the final relinquishment in 2008, the current PSC boundary covers an area of 5,851 km2.This paper presents the results of integrated petroleum geosciences framework, its implications for Oligo-Miocene reservoirs and hydrocarbon prospectivity of the basins using near field exploration approaches. A four-fold division comprising rift initiation, rift climax, immediate post rift and late-post rift stages of basin evolution characterize the basin filling. Seismic expression of these kinematic units gives an idea about the linkage of their deposition with different stages of rift evolution. The present study has also identified a new potential play concept in Oligo -Miocene reservoirs.

A Feasibility Study of SCADA Implementation at an Indonesian Oil Company

The implementation of Supervisory Control and Data Acquisition (SCADA) will make an activity more efficient because it will help control operation and production processes; control can be applied appropriately and at any time (real-time). This process will undoubtedly help the company to get maximum benefits. In 2020, the world oil price was very volatile and had touched a negative level. It is predicted that the uncertainty and low oil price will continue in the next few years. PT Pertamina Hulu Energi - Offshore South East Sumatra (PHE OSES), an Indonesian national company, plans to fully apply the SCADA system in its operational and production areas, because currently most of the PHE OSES areas still use the manual system. SCADA's estimated investment value of USD 8.6 million is a major investment for the company amidst the uncertainty of oil prices. Therefore, this project must get attention starting from the preparation, installation and implementation stages. In this article, economic analysis, cost & benefit analysis, and sensitivity test to factors that can affect economic value will be carried out. An analysis will also be carried out in terms of change management. All of these analyzes will answer whether the implementation of SCADA is feasible or not. The result of this research show that this project is feasible to be implemented in PHE OSES, it meets the capital budgeting criteria and has benefit to cost ratio larger than one. Oil price and oil losses recovery are the most affecting factors in the project’s feasibility. Company must do training, socialization, and hiring of experts play the vital role in the success of this project.

A Feasibility Study of SCADA Implementation at an Indonesian Oil Company

The implementation of Supervisory Control and Data Acquisition (SCADA) will make an activity more efficient because it will help control operation and production processes; control can be applied appropriately and at any time (real-time). This process will undoubtedly help the company to get maximum benefits. In 2020, the world oil price was very volatile and had touched a negative level. It is predicted that the uncertainty and low oil price will continue in the next few years. PT Pertamina Hulu Energi - Offshore South East Sumatra (PHE OSES), an Indonesian national company, plans to fully apply the SCADA system in its operational and production areas, because currently most of the PHE OSES areas still use the manual system. SCADA's estimated investment value of USD 8.6 million is a major investment for the company amidst the uncertainty of oil prices. Therefore, this project must get attention starting from the preparation, installation and implementation stages. In this article, economic analysis, cost & benefit analysis, and sensitivity test to factors that can affect economic value will be carried out. An analysis will also be carried out in terms of change management. All of these analyzes will answer whether the implementation of SCADA is feasible or not. The result of this research show that this project is feasible to be implemented in PHE OSES, it meets the capital budgeting criteria and has benefit to cost ratio larger than one. Oil price and oil losses recovery are the most affecting factors in the project’s feasibility. Company must do training, socialization, and hiring of experts play the vital role in the success of this project.

Srivijaya: Trade and Connectivity in the Pre-modern Malay World

The Malay city state of Srivijaya, a major actor in world economy between the seventh and the thirteenth centuries, grew at the centre of a complex set of networks encompassing much of the Indian Ocean and the South China Sea. On the basis of a critical review of past studies and the results of recent research in the archaeology and epigraphy of south-east Sumatra and the Thai-Malay Peninsula, this chapter presents a much revised and improved representation of the state and urban formation of this elusive polity, emphasizing the role of trade networks and of accompanying cultural and religious exchange networks, as operated by both local and cosmopolitan actors.

Application of Fracture Barrier Analysis in Well Stimulation Planning for Upper Baturaja Limestone Formation Based on Well Log & Drill Cutting Data from OBF-01 and OBF-04 Wells, Offshore Southeast Sumatra

In general, the South Sumatra Regional Stratigraphy of the Baturaja Limestone Formation facies is deposited on the Buildup Carbonate (Reef) and the Limestone Clastic Carbonate of the Baturaja Formation which grows as a buildup reef on the platform in the Basement High (Horst) underneath is the Lemat Formation volcanic deposits. Referring to the facies model in general, the Baturaja Limestone Formation, the depositional environment starts from Shelf Lagoon Open Circulation - Winnowed Edge Sand - Organic Buildup - Fore Slope - Deep Shelf Margin - Open Sea Shelf - Basin, meaning that carbonate is formed starting from pure organic Cabonate Buildup Reef without / a little sludge / mud to the Carbonate Basin where more muddy / mud is present, this condition causes clay minerals to also more and more mix with Terigenous Clastics (Quartz, feldpar). The complexity of the Baturaja Limestone Formation requires fracture barrier analysis associated with well stimulation planning in order to increase oil productivity with the appropriate method. Fracture barrier fracture analysis is an approach method to determine the depth interval that becomes a barrier in hydraulic fracturing by correlating the results of geomechanical analysis from well log data and mineralogical analysis from drill cuttings data, so that a commonly used well stimulation method can be selected, namely hydraulic fracturing, acidizing, and acid-fracturing.From the ternary diagram plot the XRD (bulk) analysis results show that the distribution of the main minerals (Quartz, Clay, Calcite) is more dominant in the ductile zone, hard to frac category. This shows that all the depth intervals in the OBF-01 and OBF-04 wells are more ductile, and are not recommended for hydraulic fracturing. From the XRD (bulk) analysis, Calcite mineral is more dominant, so for well stimulation work it is recommended to use acidizing or acid-fracturing.

Pipe Network Evaluation for "X" Field Production Optimization

Fields "X" is an old field in the South East Sumatra Block. The area was developed using ten platforms. One main problems on this field is the disruption of some wells productivity due to flow constraints in the piping network. The objective of this paper is to evaluate the pipeline network for area "X1" using simulation model. The simulation results show that there are bottlenecking and backpressure problems in the network. By fixing the problems, total oil production in this area can be increased up to 19 percent or 1,006.2 BOPD higer than initial condition.

Factors causing employees to resign from foreign oil company in China National Oil Offshore Corporation South East Sumatra (CNOOC SES Ltd.)

This study was conducted to determine and analyse the influence of organisational culture, work-life balance (WLB) and work pressure on employee engagement and employee turnover intention. This research uses a quantitative approach using structural equation modelling (SEM) and surveys. The population used is CNOOC SES Ltd. employees which amounted to 574 people. This research was tried in January to August 2018. This research was tried out at the CNOOC SES Ltd. Office, which is located at Indonesia Stock Exchange Tower 1 floor 19-23 JendralSudirmanKav 52 Jakarta, 12190, Indonesia. The findings in this study are that there is a significant and positive influence between company culture and WLB on employee engagement and there is a significant and negative influence between work pressure on employee engagement.

Factors causing employees to resign from foreign oil company in China National Oil Offshore Corporation South East Sumatra (CNOOC SES Ltd.)

Factors causing employees to resign from foreign oil company in China National Oil Offshore Corporation South East Sumatra (CNOOC SES Ltd.)

Long-term seismic observations along Myanmar–Sunda subduction margin: insights for 2004 Mw > 9.0 earthquake

The present study investigates the temporal variation of few seismic parameters between the Myanmar (Zone I), Andaman–Nicobar–Northwest Sumatra (Zone II), Southeast Sumatra–West Indonesia (Zone III) and East Indonesia (Zone IV) converging boundaries in reference to the generation of 26 December 2004 Mw > 9.0 off-Sumatra mega-earthquake event. The four segments are distinguished based on tectonics parameters, distinct geological locations, great earthquake occurrences, and the Wadati–Benioff zone characteristics. Two important seismic parameters such as seismic energy and b values are computed over a time-window of 6-month period during the entire 1976–2013 period for these segments. The b values show a constant decrease in Zones II, III, and IV, whereas the Zone I does not show any such pattern prior to the 2004 mega-event. The release of seismic energy was also gradually decreasing in Zones II and III till the 2004 event, and little similar pattern was also noted in Zone IV. This distinct observation might be indicating that the stress accumulation was dominant near the Sumatra–Java area located towards southeast of Zone II and northwest of Zone III. The released strain energy during the 2004 event was subsequently migrated towards north, rupturing ~ 1300 km of the boundary between the Northwest Sumatra and the North Andaman. The occurrence of 2004 mega-event was apparently concealed behind the long-term seismic quiescence existing near the Sumatra and Nicobar margin. A systematic study of the patterns of seismic energy release and b values, and the long-term observation of collective behaviour of the margin tectonics might have had given clues to the possibility of the 2004 mega-event.

The effect of increasing CO2concentration and flow rate on amine still performance in meeting gas sale specifications

The main purpose of this study is to examine the effect of increasing CO2removal and flow rate on performance of an amine still. The amine still is located in Field X in South East Sumatra at a new gas well producing gases with a rich CO2content. The still uses activated MDEA as the amine and has an IMTP 40-type packing column. Two film and desorption equilibrium curve theories were employed to analyse the amine still design conditions. Design equations were utilized to find the slope of the equilibrium curve. A slope of the equilibrium curve of 45° in the amine still is obtained in this study. The maximum liquid CO2composition of the amine still feedstock (xo) which can be separated to produce lean amine according to the specification design flow rate is 0.0307. The total flow rate of CO2-rich amine at xo= 0.029 is 761,157.6 kg/hour; the total flow rate of CO2-rich amine atxo= 0.0295 is 628,861.1 kg/hour; the total flow rate of CO2- rich amine at xo= 0.03 is 513,962.6 kg/hour; and the total flow rate of CO2-rich amine at xo= 0.0305 is 409,575.3 kg/hour.

Use of Liner Drilling Technology as a Solution to Hole Instability and Loss Intervals: A Case Study Offshore Indonesia

Summary The Banuwati field offshore southeast Sumatra, Indonesia, presents major challenges to both drilling and liner running operations because of the problematic lower Baturaja limestone formation, which is a carbonate reef structure known for severe lost-circulation conditions. The operator previously had experienced severe losses with wellbore-stability issues while drilling this formation with the inability to set the 7-in. drilling liner at the planned depth in Well A-3. The liner had to be pulled out of the hole, leading to the eventual abandonment of the existing openhole section and resulting in the sidetracking of the well. Liner-while-drilling technology was identified as the most suitable solution for setting the planned 7-in. drilling liner through the loss interval because of the following: Documented lost-circulation problems have been minimized or eliminated through the use of liner drilling technology possibly attributed to the "smear effect" (Fontenot et al. 2004) phenomenon.The liner system selected provided for high torsional capability as well as the requirement for both a mechanical and a pressure event to release the setting tool, thus minimizing the chances of premature release.A drill shoe with a displaceable polycrystalline-diamond-compact (PDC) cutting structure was used to drill the 8½-in. hole section and subsequently displaced before cementing so as to allow drill out with a conventional drill bit and bottomhole assembly (BHA). This paper will discuss the implementation of liner drilling technology in the Banuwati field project. This technology was used to drill successfully through the known lost-circulation zone with the 7-in. liner cemented in place, allowing the operator to reach the completion objectives while realizing a savings of more than USD 1 million.

インドネシア／オセアニア地域のガスプロジェクト―ＬＮＧ，Ｐ／Ｌ Ｇａｓ―

This presentation focuses on current status and future possibility regarding the commercialization of Indonesian and Oceania natural gas projects. The topics cover both LNG projects and pipeline gas projects.With respect to the LNG business, Indonesia and Australia play a vital role for supplying LNG to the Asian core markets (Japan, South Korea, Taiwan). Indonesia has 2 existing supply sources (Bontang / Arun). Tangguh is under development for Indonesia's 3rd LNG production center. INPEX's Masela and Pertamina's Donggi are under investigation for future LNG projects.In Australia, the existing NorthWest Shelf project continues to grow and Bayu-Undan (Darwin LNG) is under constructing. For future projects, Greater Sunrise, Gorgon and INPEX Browse are under consideration.Regarding the LNG markets, LNG suppliers are widely interested in the China and North America West Coast as emerging markets, but have some subjects to be resolved. And while the globalization of LNG market is ongoing, a wave of changing the business model and the terms of the sales / purchase contracts is required for our LNG projects to compete with other projects. INPEX have interests in Bontang / Tangguh/Bayu-Undan as non-operator and Masela/Browse as operator. INPEX would like to expand LNG business in this region for our future growth.For pipeline gas business in these two regions, it is immature compared with Europe / North American markets. However, to catch up with domestic gas demand, expansion of the gas pipeline network is necessary.Furthermore, INPEX has interests in NorthWest Java / SouthEast Sumatra projects etc. in Indonesia and Griffin project etc. in Australia.

Tectonic features of the southern Sumatra‐western Java forearc of Indonesia

Multichannel reflection seismic profiles along the active Sunda Arc, where the Indo‐Australian plate subducts under the overriding Eurasian margin revealed two accretionary wedges: The inner wedge I is of assumed Paleogene age, and the outer wedge II is of Neogene to Recent age. The inner wedge I is composed of tectonic flakes stretching from southeast Sumatra across the Sunda Strait to northwest Java, implying a similar plate tectonic regime in these areas at the time of flake development during upper Oligocene. Today, wedge I forms the outer arc high and the backstop for the younger outer wedge II. The missing outer arc high of the southern Sunda Strait is explained by a combination of Neogene transtension due to a clockwise rotation of Sumatra with respect to Java and by arc‐parallel strike‐slip movements. The rotation created transtensional pull‐apart basins along the western Sunda Strait (Semangka Graben) as opposed to transpression and inversion on the eastern Sunda Strait, within the new detected Krakatau Basin. The arc‐parallel transpressional Mentawai strike‐slip fault zone (MFZ) was correlated from the Sumatra forearc basin to the northwest Java forearc basin. Off the Sunda Strait, northward bending branches of the MFZ are connected with the right‐lateral Sumatra fault zone (SFZ) along the volcanic arc segment on Sumatra. It is speculated that the SFZ was attached to the Cimandiri‐Pelabuhan Ratu strike‐slip fault of Java prior to the presumed rotation of Sumatra, and that since the late lower Miocene the main slip movement shifted from the volcanic arc position to the forearc basin area due to increasingly oblique plate convergence.

On the occurrence of the giant diatom Ethmodiscus rex in an 80-ka record from a deep-sea core, southeast of Sumatra, Indonesia: implications for tropical palaeoceanography

Environmental changes recognised in a 80-ka record obtained from a deep-sea core taken at a water depth of 2542 m offshore southeast Sumatra conclusively indicate, for the first time, that ‘blooms’ of the giant diatom Ethmodiscus rex occurred in the Indian Ocean during the last glacial period, with the largest numbers coinciding with the Last Glacial Maximum. Previous occurrences of E. rex in both the Indian and the western Pacific Oceans could not be dated due to the paucity of foraminifers and contamination by diagenetic carbonate found in association with the diatoms. We use a reliable δ 18O record to date the core. The interpretation of terrigenous clays and trace metals in the core sediments, together with carbon isotopes measured on planktic foraminifers, suggests that conditions that favoured the diatomaceous blooms were a combination of changes in hydrological regime in the region caused by a substantial increase in salinity near the surface, and coinciding with a rise in nitrate levels near the surface. No major upwelling was recorded during glacial times. During the glacial period, the Indonesian Archipelago, as other tropical regions, was much drier, thus preventing a low-salinity ‘cap’ to occur at the surface of the oceans in contrast with the Holocene. In addition, monsoonal winds were absent, thus permitting the ocean to be permanently stratified, with high levels of silica and nutrients near the surface. The glacial mode of productivity, represented by the ‘blooms’ of E. rex added considerable amounts of biogenic silica to the sediment, but is not reflected by ‘classic’ productivity proxies like biogenic barium. Therefore, we have to distinguish between a ‘classic’ productivity mode as observed in the photic zone today and a glacial ‘deep’ productivity, dominated by E. rex, which may have utilised nutrients from a wider depth range.

Regional GPS data confirm high strain accumulation prior to the 2000 June 4Mw= 7.8 earthquake at southeast Sumatra

Summary Site velocities derived from repeated measurements in a regional GPS network in Southeast Asia help to constrain the motion of tectonic blocks as well as slip rates along major faults in the area. Using 3-D forward dislocation modelling, the influence of seismic elastic loading and unloading on the measured site motions are approximated. Results suggest that the northwestern Sunda arc is fully coupled seismogenically, whereas its eastern part along Java shows localized deformation. Higher horizontal velocity gradients than expected from the modelling of a fully coupled plate interface west of Manila in the Philippines suggest that deformation may be localized there. Assuming that geodetically derived convergence represents long-term rates, accumulated geodetic moments are compared to those derived using seismic data from 1977 to 2000 (Harvard CMT catalogue). If areas displaying localized deformation are dominated by creep processes, the largest difference between accumulated and seismically released deformation is located where the 2000 June 4 Mw = 7.8 Sumatra earthquake occurred.