Between 1930 and 1940, oil shows as well as gas that existed in the reservoir in gaseous phase rather than in solution (free gas) were found in the Mukah area. However, none of the discoveries were developed. Drilling results suggest that oil shows are common, while gas shows are present at deeper depths. Exploration requires a knowledge of heterogeneities in the rock. This paper is an introduction to a thematic set on the characterization of strata which acts as a reservoir for hydrocarbon gas and focuses on two main topics: (1) heterolithic facies and (2) diagenesis.The Balingian Sub-basin contains more than 6 km of sediment infill and is believed to be an important hydrocarbon kitchen. The coalbearing sedimentary packages are composed of shale or mudstone, alternating with sandstone layers of varying lateral extent and locally intercalated with coal beds. These were deposited in Upper Miocene tide-influenced or tide-dominated deltaic and estuarine environments. However, some coals and carbon derived from the hydrogen-rich parts of plants such as cuticles and spores or sporinite might have generate and expel oil. Diagenetic events were an additional aspect that affects the reservoir quality. Clay cements have grown as a combination of grain-coating or pore-lining and pore throat blocking clots. The pore throat blocking cements caused a rapid decrease of porosity, so that it had an effect on the permeability similar to that of ductile grain compaction. The grain-coating and pore-lining cements in contrast caused a slight reduction in the permeability as the pore-throats were only partially blocked. A better understanding of the coalbearing heterolithic strata through assessment may lead to the discovery of new unconventional hydrocarbon reserves.
In exploration, the investigation of prospective area encounters several barriers of land ownership, budget limitation, and exhausting permit procedures. To speed up the exploration activities of bauxite deposits and bauxite characteristics, grades of the gap areas should be simulated based on the available test pit data sets. This study aims to address the limitations and to optimize the exploration boundaries using the R project for statistical computation. R data analysis weaves the framework of kriging that required information from the adjacent data. This study utilizes the geochemical data of Al 2 O 3 , Fe 2 O 3 , SiO 2 , and TiO 2 from 296 test pit sampling points. The geochemical data used for R analysis were taken from bauxite horizon, while the other mineralogical properties were taken entirely from the exposed bedrock and test pit data. To verify the result of R analysis, recent data of the simulated area were used as a comparison. The R result shows the prediction value is slightly below the actual value of Al 2 O 3 . The kriging simulation of Al 2 O 3 was correlated with test pit and mineralogical characteristics of samples. This reveals the predicted value of simulation closely represents the true value of Al 2 O 3 grades. Extrapolation results of Fe 2 O 3 and RSiO 2 with regards to Al 2 O 3 grades suggest that higher grade of bauxite underwent desilication and deferruginization as evidenced by a high value of Index of Lateritization. It can be inferred that this attempt points out the advantages of a quick and reliable projection of bauxite laterite deposits from the limited parameters
<p>The recent eruption of Kesongo mud volcano (MV) that occurred in 28<br />August 2020 in Blora, Central Java was a common natural phenomenon.<br />MV eruption occurred periodically depending on the recharge fluid system<br />that interconnected to a geothermal system and hydrocarbon reservoir.<br />During the eruption, methane and CO2 gas were emitted to the<br />atmosphere together with rocks, muds and fluids flowing from the fracture<br />and fault system of MV. The extruded materials could be harmful and<br />beneficial for the affected ecosystem. <strong>Aims</strong>: This study aimed to address<br />the potential impact of the extruded mud volcano materials to the<br />environment. <strong>Methodology and Results</strong>: An attempt was carried out by<br />investigating gas and fluid content of every mud volcano morphology in the<br />selected 11 areas of Kradenan, Central Java and Sidoarjo, East Java. The <br />pristine fluids and gas of MV were sampled for chemical and toxic<br />compound observation. Gas composition and type was observed using gas<br />chromatography. The result shows that methane gas content ranges from<br />0.06 to 67.6 mol%., while the CO2 content ranges from 0.21 to 79.9 mol%.<br />Methane gas exhibits thermogenic gas that associated with hydrocarbon<br />generation. <strong>Conclusion, significance and impact study</strong>: The chemical<br />compound of fluids indicates high Boron (B) content above 0.5 ppm which<br />has harmful effect for crops and human health, but some compounds of<br />Ca, Na, K, Mg present as essential elements for soil nutrient. According to<br />the methane flux and chemical compound emitted by mud volcano, this<br />study contributes to a management practice to restore and conserve the <br />global ecosystem.</p>
Sebuku Island is located in Kotabaru Regency, South Kalimantan and is known as one of the main sources of laterite iron in Indonesia. Based on its tectonic setting, Sebuku Island is located within the suture zone that connects Southwest Borneo Block (SWB) and East Java West Sulawesi Block (EJWB). Due to its tectonic setting, Sebuku Island is composed of various rocks associated with suture zone, such as ophiolite rocks. The ophiolite rocks could host mineralization that occurred in Sebuku Island. The aim of this study is to determine the characteristics of lithology and mineralization as determinants of geological processes that influence the formation of rocks and mineral deposits in Sebuku Island. This study was carried out through petrological, petrographic, ore microscopy analysis, and geochemical analysis (x-ray fluorescence). 22 rock samples from Sebuku Island were collected and the result of this research shows that the chromite host rocks are composed of serpentinized dunite and serpentinite. Chromite minerals (FeCr2O4) were found in massive forms with cataclastic, brecciated texture and disseminated with pull-apart texture. Based on observation of the polished sections, it is known that the associated mineral of chromite is magnetite which is an alteration of chromite minerals. Chromitite chemical data shows the chromite composition is Al-rich (Cr# = 0.6) and classified as podiform chromitite formed by fractional crystallization. There are two magma series of igneous rock in the study area i.e. tholeiitic series consists of ultramafic-mafic rocks and calc-alkaline consists of micro-diorite. The abundance of Al2O3 and TiO2 in chromitite shows that Al-rich chromitite has formed in Supra Subduction Zone (SSZ) and has occurred near or above the Moho-transition zone.
High demand in utilizing the mineral and metal for industrial manufacture, which is unequal to the resources, has caused a vulnerable disruption. To compensate stocks in the global market, exploration of raw materials should be carried out for by-products. This study aims to elucidate the enrichment mechanism of Sc, Ga, and Nb elements from the bauxite weathering profile and sediment residue. An observation has been conducted using petrography, mineragraphy, x-ray fluorescence spectroscopy (XRF), x-Ray diffraction (XRD), inductively coupled plasma combined with mass spectrometry (ICP-MS), and scanning electron microscope - energy dispersive spectrometry (SEM-EDS). The results indicate that bauxite ores (gibbsite) hold the metal compounds of Ga, while some iron minerals of goethite and hematite are present as Sc-bearing minerals, and Nb is highly concentrated within saprolite of bauxite. The maximum enrichment of Ga and Sc is observed from the bauxite sample and sediment residue derived from microdiorite pyroxene, which makes up 24.2 - 42.1 ppm and 39.9 - 55.4 ppm, respectively. By contrast, Nb enriched about nine-fold higher in the saprolite zone relative to bauxite produced by weathering of granitic parent rocks. It suggests that metal concentration in the lateritic products depending immensely on the precursor rock types.
Situating in a tropical climate, will be favourable for Indonesia and Malaysia to have an intensive weathering and a concentration of lateritic bauxite. The study area takes place in Kuantan, Pahang State, Malaysia and Landak area, West Kalimantan, Indonesia. The study area has different type of parent rock, topography and drainage condition, which will also cause the different characteristics of alumina minerals in bauxite. One of the common form of alumina minerals is known as Gibbsite [Al(OH)3]. The objective of this research is to investigate the genesis of gibbsite from two different parent rocks. Samples were taken and collected from pitting, analyzed for Al2O3, Fe2O3, SiO2 and TiO2 using XRF and XRD examination. The parent rock of bauxite in Kuantan is basalt, meanwhile, in Landak, ranges from granodiorite to andesite. Petrography and XRD analyses of Kuantan bauxite shows predominant gibbsite, with minor amount of geothite, hematite, kaolinite, illite, quartz and feldspar, while in Landak, mineralogically consists of variant amount of gibbsite, goethite, hematite, kaolinite, illite and quartz. In Kuantan, the amount of Al2O3 varies from 23.6% - 51.01%, nearly similar than that in Landak that varies from 31.35% - 55.03%. Gibbsite in Kuantan is assumed as a transformation of Ca-rich plagioclase and Ferromagnesian- silicate minerals, on the other hand, gibbsite in Landak was produced from direct weathering of primary Al- silicate minerals (Na- plagioclase and K-feldspar). From study, it can be inferred that gibbsite formed from a layer of silicates and will concentrated in finer clay as a weathering product. Moreover, the different types of parent rock will produce different types and amount of alumina minerals. The study will be beneficial to predict the existence of potential alumina minerals in lateritic bauxite.
Land subsidence has long occurred around the Special Capital Region of Jakarta. It is important to know and deal with Land subsidence events which also cause various negative impacts. Aim: When large amounts of groundwater are withdrawn from certain types of rocks, such as fine-grained sediments, land subsidence occurs. The rock compacts because the water helps to keep the ground in place. When the water is removed, the rocks collapse in on themselves.The immediate impact is the building collapse around the Kota Tua of DKI Jakarta. Methodology and Results: The research method used is a quantitative descriptive survey method by observing the amount of land subsidence that occurs in the Kota Tua area and its surroundings. The results showed that there has been a vertical land subsidence that varies between 20-60 cm. Based on the results of the resistivity values and coordinates plotted on the Regional Geological Map (Jakarta and Kep Seribu), the research location is classified into Lithology: Clay, Sand Silt, Gravel, and Pebbles (Quartenary deposits). The phenomenon, land subsidence, is caused by a combination of various parameters, including natural consolidation of alluvial soils, excessive groundwater extraction, and also building loads from infrastructure development and tectonic factors. Conclusion, significance, and impact study: Knowing the value of land subsidence and its location is expected to support urban planning, basic infrastructure planning and development, housing, settlement planning, and local financial improvement in efforts to mitigate land subsidence disasters.
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