SOURCE ROCK GEOCHEMISTRY PRA-TERSIER AKIMEUGAH BASIN, PAPUA

SOURCE ROCK GEOCHEMISTRY PRA-TERSIER AKIMEUGAH BASIN, PAPUA

The Akimeugah Basin is located north of the southern Papuan basement high (Merauke Ridge) which separates it from the Arafura Basin to the south. This basin Judging from its association with surrounding basins, the akimeugah basin is associated with basins that have produced hydro-coal in the West Papua Basin and Australian basins. From tracing various journals and articles, the geochemical literature will provide an overview of the active host rocks in the area.

The index map of the Akimeugah and Sahul Basins is based on the Indonesian Sediment Basin Map (Badan Geologi, 2009).

The Akimeugah Basin begins as a passive margin, which is a basin formed by rifting on the northern edge of the Australian continent at the edge of this bank, experiencing cracking due to a part of the mass in its northern part which is about to move and move from Australia. In this crack, horst and graben are formed which in the graben are deposited sediments of Paleozoic and Mesozoic synrifting. Then, when this part is separated and away from Australia (drifting) sediment drifting is deposited which is generally in the form of shale or limestone, this event occurs until Paleogene.

 

Tectonic maps and cross sections of the foreland basin

At the age of Neogen, Akimeugah collided with the Central Range of Papua (Back of Papua). Since that's the type foreland basin Akimeugah. Passive Paleozoic-Neogen margins are bent into the lower Banda line and Central Range. Then at the front of the buckling (foredeep) deposited molassic sediments which are erosional products from nearby heights. However, and burial by the sedimentary part of the passive margin molasses, Akimeugah has ripened Paleozoic, Mesozoic, or Paleogene host rock in the graben. move flips from foredeep to the forebulge (the direction in the direction of the passive margin which is not bent like foredeep) laterally, or moves vertically towards the immobilization deformation zone in the impact area. The main control of the Akimeugah basin is rifting and drifting in the Mesozoic-Paleogene Paleozoicum, and collisions on Neogene (Awang Satyana, in Sabarnas Agus 2011)

Stratigraphy of the Akimeugah Basin

The Akimeugah Basin consists of pre-cambrian-tertiary deposits. The basic rock consists of Gabro rocks aged pre-cambrian and Metamorphic rocks. Followed by the deposition of the Permian Dolomite Modio formation and the Aiduna Formation which are deposited incongruously. Then it was harmoniously deposited on top of Mesozoic clastic formations (Tipuma, Kopai, Woniwogi, Piniya and Ekmai Formations), as well as some carbonate coatings locally. Above the Ekmai Formation, overlaid by clastic and limestone Paleocene-Miocene age (Waripi, Lower Yawee, Adi Members, and Upper Yawee) are out of tune. The last deposition was the final claystone of the late Miocene to Plio-Pleistocene and the uncoated local carbonate, the Buru Formation.

GEOCHEMICAL METHOD

The geochemical approach is the process of identifying active host rocks beginning with evaluating the quantity of organic material using the parameters Petter and Cassa, 1994. Determination of the quality of organic material uses a modified Van Krevelen diagram in Hunt, 1996. And Determination of maturity level using the parameters Petter and Cassa, 1994. used consisted of analysis of TOC content, Rock-Eval Pyrolysis, and Vitrinite (RO) reflection.

Identification of Parent Rock

The process of identifying host rock intervals in the aqueduct basin is carried out in several wells. Where the host rock evaluation focuses on the Woni - Wogi Formation and Aiduna Formation

Organic Material Quantity

The source rock identification begins by analyzing the host rock quantity and the ability to generate hydrocarbon. The quantity of host rock is assessed by looking at the value of total organic content (TOC) expressed in units of the percentage by weight of dry rock. Analysis of the source rock quantity is done by making a TOC curve to the depth at the intervals of each formation, as follows:

a) Woni - Wogi Formation

The Woni-wogi Formation at the Early Cretaceous age with the lithology of sandstone, shale and siltstone consisting of having a value of organic material content is 0.34 wt - 2.9 wt% based on the classification of organic material content into the Poor - V. Good category (Peters and Cassa, 1994). Judging from the ability to generate hydrocarbons with parameters S1 + S2 (Potential Yield) the value is 0.2 mgHC / g - 6.21 mgHC / g which is included in the Poor-Good category (Peters and Cassa, 1994). This data shows that this formation has the potential to become host rock.

TOC content of Woni-Wogi Formation and Ability to generate

Hydrocarbons

b) Aiduna Formation

Aiduna Formation at Permian age with shale lithology has a value of organic material content which is 0.39 wt% - 3.45 wt% based on the classification of organic material content into the Poor - V. Good category (Peters and Cassa, 1994). Judging from the ability to generate hydrocarbons using the parameter value S1 + S2 (Potential Yield) with a value of 0.33 mgHC / g - 10.47 mgHC / g into the Poor-V.good category (Peters and Cassa, 1994). This data shows that this formation has the potential to become host rock

Quality of Organic Materials

The quality of organic material influences whether or not the potential of sedimentary rocks to become host rock, which is represented by the kerogen type of host rock. Kerogen type is influenced by the constituent material and its depositional environment. Kerogen type also determines the final active rock product in the form of oil, oil / gas or gas. Determination of kerogen type in this study using a modified van Krevelen diagram plot. The modification is to replace the plot of the H / C to O / C ratio to the ratio of the hydrogen index (HI) to Tmaks. This is done because there is little analysis that gets H / C, O / C and oxygen index (OI) data. Analysis of the quality of organic material using Tmax Vs HI values, as follows:

a) Woni - wogi Formation

The results of plotting HI vs Tmax data from 49 samples in this formation indicate that the kerogen type in the Woni-wogi formation has kerogen Type II - III (Modified Van Kravelen Diagram in Hunt 1996) which is dominated by kerogen type III (Prone Gas). Tmax data shows that this formation has a mature maturity level

Quality of the Woni - Wogi Formation

b) Aiduna Formation

Kerogen type analysis based on HI Vs Tmaks data conducted on 22 samples in the Aiduna formation shows that this formation has a kerogen type II - III which tends to produce a mixture of oil and gas dominated by type III (gas). Also based on Tmax data, this formation has entered the maturity window. With maturity level not yet mature.

Quality of Aiduna Formation

Maturity

Analysis of the maturity of organic material will determine the depth interval (window of maturity) of active host rock that produces hydrocarbons. Maturity analysis is done by looking at the value of vitrinite (Ro) reflectance. Maturity analysis based on vitrinite reflectance (Ro) is based on reflection values ​​(Ro) derived from kerogen, especially from vitrinite. Maturity analysis using Ro is done by combining the whole well so that the trend of maturity values ​​is obtained in a regional (Figure 6). The results of the Ro value analysis indicate that the maturity window in this basin is 7000 feet below sea level. This proves that the Woni-Wogi Formation and also the Aiduna Formation have entered the maturity window. Ro is done by combining all the wells so that the trend of maturity values ​​can be obtained regionally (Figure 6). The results of the Ro value analysis indicate that the maturity window in this basin is 7000 feet below sea level. This proves that the Woni-Wogi Formation and also the Aiduna Formation have entered the maturity window.

Regional Maturity

Immersion History

The results of modeling the history of 1D immersion in a well show that the maturity of the host rock occurs at the age of miocene at a depth of 1980 m or 6500 ft. It is this sediment yield that has the role of ripening pre-tertiary host rock. Where the speed of sedimentation takes place very quickly due to the large supply of erosion from the high sediment produced by the collusion of neogeneous ferns.

History of Immersion of a Well in the Akimeugah Basin

CONCLUSION

The results of the identification of pre-tertiary host rocks in the Akimeugah Basin indicate that the intervals of the host rock of the Woni-Wogi formation and Aiduna formation have poor organic matter content - good. In addition, the two formations have a kerogen type dominated by type III kerogen which will tend to produce gas and have entered the maturity window. This shows that the woni-wogi and Aiduna formations are active host rocks in the Akimeugah basin.

The maturation of this formation occurs during the middle myoses, where a lot of this fast and sedimentary sediment originates from collusion which occurs at that time which successfully ripens the pratersier host rock of this basin.

Reference:

• Harahap, B.H. 2012. Tectonostratigraphy of the Southern Part of Papua and Arafura Sea, Eastern Indonesia, Indonesian Journal of Geology, Vol. 7
• Huang, W.Y. dan Meinschein, W.G. 1979. Sterol as Ecological Indicators: Petroleum Geochemistry. Bandung. PreConvention short course IAGI : Awang H. Satyana 2004.
• Peck, J.M. and Soulhol, B., 1986. Pre- Tertiary Tensional Periods and Their Effects on the Petroleum Potential of Eastern Indonesia. Proceedings Indonesian Petroleum Association, 15th Annual Convention, 341-369.
• Peters, K.E. dan Cassa, M.R. 1994. Applied Source Rock Geochemistry, dalam Magoon, L.B. and Dow, W.G., eds., The Petroleum System - From Source to Trap: AAPG Memoir, 60
• Satyana, A. 2015. Petroleum Geochemistry for Exploration and Production of Conventional and Unconventional Hydrocarbons. Short Course: IPA 2015
• Subarnas, Agus. 2011. Penyelidikan Pendahuluan Kandungan Gas Dalam Batuan Serpih DiDaerah Subroto, E. (2004): Pengenalan Geokimia Petroleum. Bandung :Penerbit ITB
• Waghete Dan Sekitarnya, Kabupaten Deiyai Provinsi Papua. Prosiding Hasil Kegiatan Pusat Sumber Daya Geologi Tahun 2011
• Yudha Situmorang, et al, 2017, STUDI GEOKIMIA BATUAN INDUK AKTIF PRA-TERSIER CEKUNGAN AKIMEUGAH, LEPAS PANTAI PAPUA SELATAN, Padjajaran Geoscince Journal
• Waples, D. 1985. Geochemistry in Petroleum Exploration, International Human Resources Development Corporation, Boston.
• http://geomagz.geologi.esdm.go.id/cekungan-akimeugah-dan-sahul-harapan-baru-penemuan-migas/
• https://dzulfadlib.wordpress.com/tag/lapangan-minyak/

Ketungau and Melawi Basins, West Kalimantan

Ketungau and Melawi Basins, West Kalimantan

The Ketungau and Melawi Basins are located in the West Kalimantan region, adjacent to the Ma­laysian border. The Melawi Basin, in the south is separated from the Ketungau Basin by the Semitau High. Tectonically, the Ketungau and Me­lawi Basins can be classified as intramontane basins. The Ketungau and Melawi basins are separated from each other by a belt of deep-water rocks and a belt of melange. 

Regional geological pattern of Kalimantan

Preliminary exploration and assessment of the Ketungau and Melawi Basins were carried out during 1980s and 1990s by several oil companies. The most recent assessment work is conducted by Lemigas Team, and resulted in the Kayan Play Model for Melawi Basin exploration. In 2009-2010, the Geological Agency carried out field work activities in the Ketungau and Melawi Basins, which was intended to collect field data, outcrop samples, and sedimentologic and stratigraphy data, as reported by Santy et al. (2009), Gumilar et al. (2009), Heryanto et al. (2009), Santy et al. (2010), and Gumilar et al. (2010). Observation had been done in the Ketungau Formation, outcrop­ping in Ketungau and Sekalau River, and Silat For­mation, outcropping in Silat Rivers and its tributaries in the Melawi Basin. The aim of the study is to assess the probability of petroleum source rock potential for hydrocarbon play in the Ketungau and Melawi Basins. Several samples had been selected for an organic geochemistry analysis.

General Geological Setting

Tectonic activities in this region were controlled by the movement of Eurasian Plate to the southeast during Cretaceous - Early Tertiary. Pre-Tertiary tectonic activities created uplifting of Semitau Complex and Boyan Melange Complex separat­ing the Ketungau and Melawi Basin. Nevertheless, Halls and Nichols (2002) suggest that the Ketungau and Melawi Basins are not conventional foreland basin formed by loading of thrust sheets, indicated by the absence of thin skinned thrusting in the highly eroded areas.

The pattern of Ketungau-Melawi Basin bound­aries follows the direction pattern of NW-SE strike slip zone developing during Eocene-Oligocene (± 30 Ma) at the Sundaland Margin in Kalimantan. A 45o counter clockwise rotation during Late Oligocene to Early Miocene (± 20-10 Ma) resulted in a basin configuration as observed today. The next Neogene tectonic activities caused an E-W trending thrust system, sediment fold­ing, and created Ketungau, Silat, and Melawi syn­clines, as well as Sintang anticline.

 The base of Ketungau and Melawi Basins is not exposed, though there is a thick succession of lithic arenite sandstone sequence consisting of sandstone, silt, and mudstone. The thick sediment succession is a result of basin subsidence as the response of sedi¬ment infill in the boundary between a linear zone of granite and schist in the northern part (Semitau High), and the base of continental plate in the south¬ern part (Schwaner Mountain Zone).

Sediment infill in the Ketungau-Melawi basin was dominantly from the eroded rocks of older orogen in the Kalimantan Island. Small part of sedi¬ment supply probably also comes from Indochina land (Halls and Nichols, 2002). High rate of clastic detrital sediment supply in this basin had suppressed the productive development of carbonate benthic, therefore no well developed carbonate sediments exist.

Sedimentary phase of the Ketungau Basin oc¬curred during Eocene until Oligocene, with the deposition of fluvial conglomerate unit gradationally change to be lacustrine and shallow marine sediment unit of Kantu Formation. The Kantu For¬mation is conformably overlain by a fluvial clastic unit of the Tutoop Formation and a fluvio-marine de¬posit of the Ketungau Formation. Stratigraphic succession in the early develop¬ment of the Melawi Basin has a similar character¬istic and lithologic distribution with the Ketungau Basin. Those formations were deposited above the Pre-Tertiary basal sediments of Selangkai Formation. The Haloq For¬mation, the oldest sediments deposited in the basin, is regarded as an equivalence of Lower Ketungau. This formation consists of fluvial quartz sandstone and conglomeratic unit, deposited during Upper Eo¬cene. The Ingar Formation unconformably overlying the Haloq Formation, consists of alternating mud¬stone, silt, and fine sandstone of lacustrine deposit. The Dangkan Formation, which is considered to be equivalent to the Tutoop sandstone, was deposited unconformably over the Ingar Formation. It is fol¬lowed by the Silat Shale, regarded to be equivalent to the Ketungau Formation, that was deposited dur¬ing Oligocene. When the sediment deposition in the Ketungau Basin had terminated, the deposition in the Melawi Basin still occurred where fluvial units of the Payak, Tebidah, and Sekayam Formations were deposited.

Geological Map of Ketungau-Melawai Basins

Description of Ketungau and Silat Formations

As a whole packet, the Ketungau Formation is 900 m thick, consisting of claystone, shale, silt, fine sandstone, and thin bedded coal in the upper part. Claystone layers usually contain silt or fine sand concretions and mollusk fossils of Gastropods and Bivalves. Ichnofossils of Planolites, Thalassinoides, and Ophiomorpha were sometimes found in some layers. Sandstone is usu­ally micaceous and contains framboidal pyrite as an indication of marine influence. Shale layers are flaky, rich in organic matters, and contain mollusk fossils of Gastropods and Bivalves, of which some of them are in juvenile forms. The depositional environment of this forma­tion is fluvio-marine, with the interval of shallow marine sediments appearing periodically.

Stratigraphic comparison between Ketungau Basin and Melawi Basin, and Lupar-Serawak Valley

The Silat Formation consists of 1000 thick sedi­ments, dominated by black carbonaceous mudstone, shale, slaty shale, minor dark coloured siltstone, fine- to medium-grained sandstone, and occasionally thin layer of coal. In several spots, there are also rich layers of Gastropod, Pelecypod, and plant remains. The depositional environment of Silat shale is fluvio-marine to open.

References:

• Hall, R., 1996. Reconstructing Cenozoic SE Asia: In: Hall R. and Blundell D., (eds.) Tectonic evolution of Southeast Asia. Geological Society of London, p. 153-184
• Hall, R. and Nichols, G., 2002. Cenozoic Sedimentation and Tectonics in Borneo : Climatic Influences on Orogenesis. In: Jones, S.J. and Frostick, L. (eds.), 2002 Sedimen Flux to Basins : Causes, Controls, and Consequences, The Geological Society of London, Special Publication.
• Heryanto, R. Williams, P.R., Harahap, B.H., and Pieters, P.E., 1993a. Peta Geologi Lembar Putussibau, Kalimantan, Skala 1: 250.000, Pusat Penelitian dan Pengembangan Geologi, Bandung.
• Heryanto, R., Williams P.R., Harahap B.H., Pieters P.E., 1993b. Peta Geologi Lembar Sintang, Kalimantan skala 1 : 250.00. Pusat Penelitian dan Pengembangan Geologi, Bandung.
• L. D. Santy and H. Panggabean, 2013, The Potential of Ketungau and Silat Shales in Ketungau and Melawi Basins, West Kalimantan: For Oil Shale and Shale Gas Exploration, Indonesian Journal of Geology, Vol. 8 No. 1
• Pieters, P.E., D.S. Trails, and Supriatna S., 1987. Correlation of Early Tertiary Rocks Across Kalimantan. Proceedings of Sixteenth Annual Convention of Indonesian Petroleum Association,16, p.291-306.
• Williams, P. R., Supriatna, S., Trail, DS., and Heryanto, R., 1984. Tertiary Basin of West Kalimantan, Associated Igneous Activity and Structural Setting. Indonesian Petroleum Association 13th Annual Convention Proceed­ings, p.151-160.

 
 

TARAKAN BASIN - BORNEO

TARAKAN BASIN - BORNEO

Tarakan Basin, as the name implies, is around Tarakan Island. The island is geographically located in the Tarakan area, and its surrounding area, East Kalimantan Province, about 240 km north - northeast of Balikpapan. Geologically this island is located in the middle of the Tarakan Basin which is part of the NE Kalimantan Basin. Basically, the NE Kalimantan Basin is divided into 4 groups Sub basins: Tidung Sub Basin, Berau Sub Basin, Muara Sub-Basin, and Tarakan Sub-Basin.

Tarakan Basin is located in the northern part of Kalimantan Island. The area reaches 68,000 km2. In general, the northern part of this basin is limited by Mangkaliat exposure, in the East it is bordered by the Sulawesi Sea and in the West it is limited by the Central Range Complex.

 

Map of Location of the Tarakan Basin

Tarakan Basin can be divided into several sub-basins namely:

1. Tidung Sub-Basin

This sub-basin is located in the north and is on land extending to Sabah and developing during the Late Eocene to the Middle Miocene. Separated from the Berau Basin children to the south by the Latong Punggungan. Apart from Tarakan by the Sebuku Exposure, the anticline and fault rise northwestward along the coast and are bordered by a flat shear fault in northern Sempoa.

2. Tarakan Sub-Basin

This sub basin developed mainly in offshore areas filled with thick Plio-Pleistocene clastic deposits with deposition centers around Bunyu Island and Tarakan and have experienced pinchout and onlap to the west

and south.

3. Estuary Sub Basin

This sub basin is located off the coast of Tinggian Mangkalihat. It has the southernmost deposition center, developing off the coast. It is bounded by parallel parallel faults, the Mangkalihat and Maratua faults, cracked and passive margin sediments, and Oligocene carbonate structuring - Recent in the postrift section, which is the host rock at Eocene age.

4. Sub-Berau Basin

The Berau sub-basin is located in the southernmost part of the Tarakan Basin which developed from Eocene to Miocene and has a similar deposition history with the Tidung Sub-Basin. The dominant structure found on Tarakan Island is a normal fault trending Northwest to North with a fractured plane tilted to the East. Some of these faults are growth faults with roll over.

Tarakan Sub-Basin (Tossin and Kodir, 1996)

TEKTONIK

Tarakan Basin has a variety of faults, structural elements and trends. The tectonic history of the Tarakan basin begins with the extension phase from the Middle Eocene which forms a NW-SE direction wrench and influences the process of fracturing the Makassar strait which stops at the Early Miocene. This initial tectonic phase is the opening phase of the basin to the east which is indicated by the presence of enechelon block faulting which has a slope to the east.

From the Middle Miocene to the Pliocene is a more stable condition where sediment is deposited with a delta environment that spreads from several systems of distribution patterns from west to east. Examples of rivers that have a downstream in this area are the Proto-Kayan, Sesayap, Sembakung and several others. In this phase, the basin experiences subsidence due to the gravity of the load from the increasingly deltaic deposits, resulting in an electrical fault. The growth of the fault structure here indicates that the process of deployment of delta deposits to the west has taken place which has become less and begins to be deposited with carbonates. In the basin that leads to the east is composed of thick delta deposits, which are associated with normal syngenetic faults (normal faults that form together with precipitation).

The final tectonic phase in this basin is the compression process that occurs in Plio - Late Pleistocene due to the collision of the Philippine plate with the Borneo / East Kalimantan plate. This reactivates the existing structure and reverses the direction of some gravitational faults. However, a stronger force is in the northern part of the basin where the Miocene and Plosen deposits become folded and broken with NW - SE direction to WNE - ESE. In the eastern part of the basin, this compression phase forms a high structure because the sediment material is plastic so it forms the Bunyu and Tarakan anticlines.

From the tectonic phase it is believed that the deformation formed from the beginning of the tectonic process is the main controller of the formation of hydrocarbon deposits in the Tarakan basin.

Tectonic Order of the Tarakan Basin (Modified BEICIP, 1985)

REGIONAL GEOLOGY OF STRATIGRAPHY AND SEDIMENTATION

The Tarakan Basin is composed of Tertiary-aged rocks deposited on the Pre-Tierier bedrock. The dynamics of sedimentation in the Tarakan basin began at the Eocene age, initially the Tarakan Basin was a land area that deposited the Sembakung Formation - Green Formation. In the Oligocene a precipitation pattern of transgression is formed which is dominated by coarse clastic and carbonate rocks (Seilor Formation). The development of the transgression system continues until fine sediment is deposited (Nainputo Formation) and in some places reef limestone (Tabular Formation) is deposited. Then a regression occurs until the basin is lifted, and then coarse clastic sediments are deposited which the source is referred to as the Central Range Complex (LEMIGAS, 2006).

The depositional environment is a complex delta and stretches from West to East (Trained / Stretch Formation). The Tabul Formation is in the east which is a part of the Production Department which is composed of claystone facies. In the late Miocene, the elevation of Kuching took place, thus lifting the northern part of the Tarakan Basin. And in the Pliocene a delta environment was formed and deposited the Tarakan Formation.

The stratigraphy of the tarakan basin, from old to young is as follows:

Stratigraphy of the tarakan basin

Sembakung Formation

Early Tertiary rocks consist of the Sembakung Formation, which overlaps unaligned Late Cretaceous rocks, consisting of carbonic siliciclastic rocks from the litoral marine environment to the shallow sea at the time of the Eocene.

Green Formation

The Sujau Formation consists of clastic (conglomerates and sandstones), shale, and volcanic sediments. The clusters of the Sujau Formation represent the first stage of filling a "graben like" basin which may have been formed as a result of the burning of Makassar in the Early Eocene. The lithology of the composition of 1000 meters of volcanic acid, sandstone, volcaniclastic. The geological structure that develops is very complex and results in this area being strongly folded.

Seilor Formation

Micritic limestones from the Seilor Formation are deposited in harmony above the Sujau Formation and the Mangkabua Formation which consists of sea and marrow shales which are Oligocene to be a sign of succession change to basin.

Mangkabua Formation

In this formation there was a progradational change from the Seilor (micrite limestone) formation to a thick and massive batunapal. There are Nummulites fichteli (Marks, 1957) which are Oligocene. This formation eroded intensively at the end of the Oligocene because of the tectonic process in the form of lifting caused by volcanic activity.

Reference:

• Google.com
• Yahoo.com
• Wikipedia.com
• GDA Consultant, 2006, PRELIMINARY STUDY OF POTENTIAL HYDROCARBON IN Sangatta Block, Onshore, East Kalimantan, Pertamina UEP IV (Unpublished)
• http://nicoandreasnainggolan.blogspot.com/2014/04/tarakan-basin.html