Journal of Geoscience, Engineering, Environment, and Technology
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Geomorphological Assessment to Tract the Flow Evolution of Kali Putih, Srumbung District, Magelang Regency, Central Java, Indonesia
Get PDFKali Putih (The White River) is located in Srumbung district, Magelang regency, Central Java, Indonesia. It is originated from the upper slope of Merapi volcano, flowing to the Southwest direction. Kali Putih belongs to one of the most channels where frequently flowed by lahar of Merapi volcano. Based on geomorphological and geological traces found at the surrounding of modern Kali Putih channel, this indicated that the flow of Kali Putih has undergone displacement several times. The position of ancient river valley in the past has changed into the modern river valley in the present time. The existence of ancient Kali Putih is exhibited by the presence of large dry valley morphology associated with volcanic blocks, gravels, and sand sized materials with various sorting, representing the characteristics of lahar and alluvial deposits. In the present time, the former river channels are currently used by local people for agricultural and fisheries land
Analysis of Ultramafic Rocks Weathering Level Using the Magnetic Susceptibility in Konawe Regency, Southeast Sulawesi, Indonesia
No full textThe Konawe region is part of the Sulawesi Southeast Arm ophiolite belt where ultramafic rocks are exposed in the form of dunite and peridotite. The formation of nickel deposits is closely related to the weathering process of ultramafic rocks as a source rock. Ultramafic rocks exposed to the surface will experience weathering which is influenced by many factors, including in the form of climate change, topography, and existing geological structures.
The weathering process in the source rock can influence variations in chemical elements and magnetic properties in laterite soil profiles. For example, the chemical weathering might affect magnetic mineralogy and the physical weathering could affect granulometry as well as the quantity of magnetic minerals in the soil. Condition of weathering of ultramafic rocks (initial, moderate and advanced) can affect nickel content in laterite sediments. The weathering profile study of serpentine mineral is an indication of the lateralization process that occurs in ultramafic rocks and is carried out through petrographic analysis of thin cuts and polish cuts. Determination of weathering level like this is based on the level of weathering of the mineral serpentine.
In this study, the determination of the weathering level of ultramafic rocks (initial, moderate, and continued) uses magnetic susceptibility parameter. A total of 232 ultramafic rock core samples obtained from 34 hand samples were taken from different places and weathered levels were analyzed. The results of the research have shown that the magnetic susceptibility of ultramafic rocks in the study area varies, from 580 x 10-6 SI to 4.724 x 10-6 SI. Based on the value of magnetic susceptibility, magnetic minerals contained in ultramafic rock samples are hematite and geotite minerals. This means that the weathering level of ultramafic rock samples is the continued weathering level. The level of continued weathering that occurs in ultramafic rocks in the study area produces nickel laterite deposits with a nickel content of 1.65 - 2.40% in the saprolite zone, 0.42% in the saprock zone, and 0.20 - 0.51% in the basic rock zone (bedrock)
The Origin of Geothermal Water Around Slamet Volcano - Paguyangan - Cipari, Central Java, Indonesia
No full textThe existences of several hot springs between Slamet volcano, Paguyangan, and Cipari Districts raised questions regarding their origin. Several studies have been conducted related to the hydrothermal system at the location. Subsequent studies are needed to understand the hydrothermal system at the research site for the sustainability and conservation of geothermal natural resources. This research has reviewed several previous studies plus the latest information on the origin of hot spring water with the help of deuterium (2H) and 18O isotopes. This study used geochemical analysis of hot springs (geothermal) and local meteoric water to obtain information on isotope values. This was used for the interpretation of the origin of geothermal water. This study also used regional geological analysis methods for the interpretation of the mechanism for the emergence of these hot springs. The results of the analysis informed that the origin of hot water was local meteoric water. The geological structure was weak enough to allow water from the geothermal reservoir to reach the surface and meteoric water into the reservoir
Subsurface Shallow Modelling Based on Resistivity Data in The Hot Springs Area of Libungo Geothermal, Gorontalo, Indonesia
Get PDFVolcano-tectonic events in Libungo can be the cause of the presence of geothermal potential. There is no detailed research on shallow subsurface conditions in Libungo that can show the distribution of subsurface fluids. This research aims to create a shallow subsurface model of the Libungo geothermal area based on resistivity data. Resistivity data collection was carried out in the Libungo hot springs area. The electrode configuration used is the Schlumberger configuration. The variation in resistivity values is calculated using current data, potential difference data and geometry factors. The results of the calculation of the resistivity values variation are plotted versus depth. Variations of resistivity value versus depth are then displayed in the form of a single log, lithology distribution and 3D lithology model. The results showed that the shallow subsurface of the Libungo geothermal area was composed of andesite, volcanic breccia, silty clay and clay. Andesite in the research area has resistivity values ranging from 320 - 349 Ωm, has slightly fracture and is andesite dry. Volcanic breccia has a resistivity value of 177-198 Ωm, has a well to slightly fracture and is a volcanic breccia moist. Silty clay has a resistivity value of 3.25-37.99 Ωm and is a wet to moist silty clay. Clay has resistivity values in the range 1.56-2.78 Ωm and is wet to moist clay. Fluid distribution in the shallow subsurface area occurs in volcanic breccia, silty clay and clay. Shallow subsurface fluids accumulate mostly in the northern part of the Libungo geothermal area
Resistivity Models of Pantar Island Geothermal System East Nusa Tenggara, Indonesia
Get PDFThe subsurface geological conditions of a geothermal system are vital objects to be considered in geothermal exploration. The Magnetotellurics survey was conducted to explore for geothermal potential in Pantar Island. This is to achieve deeper penetration compared to our previous study that adopted resistivity method to determine reservoir zones based on rock resistivity models. The difference in rock resistivity in geothermal systems provides subsurface geological information in the form of low resistivity that associated the clay cap zones (high conductive), the medium resistivity zones associated with the reservoir zones, and high resistivity associated with a heat source. The results of 2D and 3D models from MT data show that the low resistivity value (<20Ωm) as a clay cover zones, this layer from the surface to -1000 meters. Medium resistivity values (20-100 Ωm) starting from depths -1000 meters to -2000 meters associated with reservoirs zones, high resistivity values (> 200 Ωm) starting from depths of -2000 meters are considered as heat source from the Pantar geothermal system
Geophysical Survey on Open Dumping Landfill for Monitoring Spread of Leachate: A Case Study in Pekanbaru, Riau, Indonesia
Get PDFPekanbaru is a city in Indonesia with high population growth. The increasing amount of the population has a parallel relationship with the increasing quantity of waste disposal. This study has been conducted on an open dumping landfill at Pekanbaru that surrounded by residential areas. Waste disposal produces leachate as a threat to surface water and groundwater resources. This study aims to investigate the contamination spread formed by leachate using the geophysical method. Direct Current Resistivity (DCR) has been used to produce 2 D Resistivity subsurface Models. Data acquisition has been done using multi-electrodes (32 electrodes) with spacing 2 m between electrodes. 2D Resistivity model produced, a contaminant from leachate represented by low resistivity value 26.1 - 870 Ωm. The deepest penetration of leachate that detected is around 3 m from the surface. It has been understood that leachate from the landfill of the study area is not contaminated groundwater yet. It confirmed by groundwater analysis at residential around the landfill area. By knowing the spreading of leachate, preventive action can be made to maintain the quality of groundwater resources
Simultaneous Equation Model for Economic Calculation of Households of Independent Rubber Farmers in Mineral Land in Kampar Regency, Riau Province, Indonesia
Get PDFRubber is a plantation crop which is mostly a source of community income in Kampar District. As a source of household income, rubber farming is managed by households independently. This study generally aims to design models and government policy strategies in the development of smallholder rubber plantations on land typology mineral land conditions on the economic decision making of rubber farmer households. Specifically, this study was conducted with the aim of analyzing the characteristics of independent smallholders and internal and external dominant factors that influence the allocation of working time, income and household expenses of rubber farmers. This research was conducted using a survey method located in Kampar District. The data used in this study consisted of primary data obtained using the interview method. Samples were taken by simple random sampling method with 60 rubber farmers. Descriptive analysis and Economic Decision Model of Rubber Farmer Households using the simultaneous equation model approach with the Two Stages Least Square (2SLS) analysis method were performed to answer the research objectives. The results showed that only internal factors of farm households are responsive to household economic decisions. There are no external factors included in the model that are responsive to the economic decisions of rubber farming households in Kuantan Singingi Regency regarding the aspects of production, working time allocation, income and expenditure of rubber farming households. From the aspect of production, no responsive internal or external factors were found, but the biggest effect was the number of productive rubber stems. From the aspect of work time allocation, internal factors that are responsive to influence are the total outpouring of farmer work, outpouring of farm family work in businesses and the workforce of farmer households. Furthermore, from the aspect of farmer's household income the responsive internal factors that influence it are the farmer's household income in the business. then what influences household expenditure is outflow of work in business, farmer education, wife education and total rubber farmer income. The policy implications of increasing rubber prices and outpouring of family work in the business have the most positive impact. While the increase in wages for workers outside the family has a negative impact on the household economy
Identification of Clay Mineral Content Using Spectral Gamma Ray on Y1 Well in Karawang Area, West Java, Indonesia.
Get PDFNorthwest Java Basin (NWJB) is one of the proven hydrocarbon basins in Indonesia. The scope of this paper will focus onthe shales and sandstone interval within Y1 well in Karawang area, NWJB, Indonesia.A cored interval from Y1 well was chosen for an investigation of the clay minerology for the gamma-ray activity and with the purpose of determining how the Spectral Natural Gamma (SNG) log could be used as an indicator of source rock and reservoir quality. The Th/U as a redox indicator is used to assert that the shales are of anoxic conditions of shallow marine environments. Despite the relatively high insoluble Th values (60-74.15) ppm, the presence of U in substantial amounts, which only occurs in reducing conditions where it is preserved as a lower insoluble valence (U4+) explains for the low Th/U values ranging between (5.8-7.1) ppm/ppm. The overall Th/U value of the evaluated shales remain less than 25, where Th/U <25 is suggestive of marine sediments, whereas Th/U <4 is indicative of marine black shales of reducing conditions. Although no linear relationship was found between clay content and K, Th, or U, the K content characteristic three discrete reservoir characteristic (RC). The RC-I has predicted a matrix-supported texture with the highest K signal, illite and illitised kaolinite are roughly equal in importance as source of K. The RC-II has predicted a grain-supported texture with intermediate K content. K-feldspar, mica and illite as the main sources. The RC-III has predicted have a low K content with grain-supported texture and most of the K is hosted in feldspar. Overall, the laboratory measurements appear to be applicable to the log data, and, using SEM or XRD, the detail facies subdivision can be extended throughout the source rock and reservoir section based on the SNG log
Gas Saturated Sandstone Reservoir Modeling Using Bayesian Stochastic Seismic Inversion
Get PDFThis study has been done to map the distribution of gas saturated sandstone reservoir by using stochastic seismic inversion in the “X” field, Bonaparte basin. Bayesian stochastic inversion seismic method is an inversion method that utilizes the principle of geostatistics so that later it will get a better subsurface picture with high resolution. The stages in conducting this stochastic inversion technique are as follows, (i) sensitivity analysis, (ii) well to seismic tie, (iii) picking horizon, (iv) picking fault, (v) fault modeling, (vi) pillar gridding, ( vii) making time structure maps, (viii) scale up well logs, (ix) trend modeling, (x) variogram analysis, (xi) stochastic seismic inversion (SSI). In the process of well to seismic tie, statistical wavelets are used because they can produce good correlation values. Then, the stochastic seismic inversion results show that the reservoir in the study area is a reservoir with tight sandstone lithology which has a low porosity value and a value of High acoustic impedance ranging from 30,000 to 40,000 ft /s*g/cc