Journal of Geoscience, Engineering, Environment, and Technology

Back matter JGEET Vol 09 No 02 2024

JGEET (J. Geoscience Eng. Environ. Technol.) — 2024-06-29

Front matter JGEET Vol 09 No 02 2024

JGEET (J. Geoscience Eng. Environ. Technol.) — 2024-06-29

Magma Petrogenesis Study Based on Morphology and Texture Of Zircon Minerals: Case Study At The Causative Intrusive In The HLE Porphyry Copper-Gold Prospect, Sumbawa Island, Indonesia

Fadlin — 2024-06-29

The zircon mineral is one of the accessory minerals within igneous rocks for its ability to resist hydrothermal and metamorphic processes. By examining their morphology and texture, zircon minerals can provide valuable insights into magma's petrogenesis, including temperature and composition. Two methods used to reach the research objectives include Petrography and SEM-CL analysis of the zircon grain from the diorite porphyry of the HLE prospect. On the basis of Petrography observation, the grain size of zircon ranges from 50 to 300 µm in size, and most have a transparent to grey color with prismatic, non-prismatic euhedral-subhedral elliptical, and non-prismatic rounded in shape. The zircon crystal typologies from the diorite porphyry are classified into S10, P2, S12, S13, S16, and S17 types, indicating the wide range of the crystallization temperature of zircon, ranging from 700 to 800 °C. The zircon from the diorite porphyry of the HLE prospect shows the medium values of pyramids typology, which is {101} = {211}. It corresponds to a medium Al/Na + K ratio (A index) value, indicating zircon as a product from the calc-alkaline magmas series. The trend of the calc-alkaline/sub-alkaline in typology suggests crustal sources mixed with mantle material. Furthermore, based on SEM-CL analysis the zircon shows dominantly oscillatory zoning with thin bands, and some grains show weak zoning in the outer core, typical of magmatic zircon. Moreover, the presence of lamellae texture of magnetite-ilmenite mineral under the scanning electron microscopy (BSE image) can be interpreted as the magma related to the high oxidizing magma.

Restoring The Permeability Of Peat Soil Using Sand-Mixed And Bio-Grouting Techniques Made From Bacteria

Gezan Jacob — 2024-06-29

Restoring the permeability of peat soil using a mixture of sand and bio-grouting techniques made from bacteria aimed to determine the effect of adding 5% sand by weight of dry soil and bacteria on the permeability of peat soil. Peat soil is a problem that is often encountered in the world of construction. Peat is a type of soil formed from the accumulation of half-decayed plant remains which causes it to have a high organic matter content.

The research testing method refers to ASTM (American Society for Testing and Materials) procedures and SNI. Preliminary testing, namely testing the original soil moisture content, testing the original soil specific gravity, and testing standard compaction (proctor test). Meanwhile, permeability testing was carried out using the falling head method. The original soil was taken at the location of Buana Makmur Village km 55, Dayun Sub District, Siak Regency, namely in the form of sand 5% of the dry weight of the soil, additional ingredients in the form of bacteria and CaCl2 and Uruea.

Based on the results of testing the physical properties of the original soil, it is known that the soil in Buana Makmur Village, km 55, Dayun Sub District, Siak Regency, is an original soil type with a water content of 407.5% and a specific weight (Gs) of 1.3 gr. Based on the results of the permeability test conducted, mixing 5% sand and adding 25% bacteria had the lowest permeability coefficient value compared to the original soil and sand mixed soil which had a permeability coefficient of K20oc = 1.166x10^-3cm/second.

Relocation Study of Flores Sea Hypocenter (Mw = 7.3) Based on Single Station Estimation Using ObsPy

Azmi Khusnani — 2024-06-29

One area in Indonesia that is prone to disasters is the Flores Sea area, which has the potential for earthquakes to trigger tsunamis. This is due to the location of Flores, which is in a subduction zone that originates from the collision of the Indo-Australian (South) and Eurasian plates. Inaccuracies in earthquake locations are influenced by differences in residual travel time values, mathematical solutions to location problems, and inaccuracies in the seismic velocity model used. The accuracy of determining the hypocenter of an earthquake influences the location of the earthquake source, which will later be used as a reference in appropriate earthquake disaster mitigation planning. Based on this, an analysis of earthquake hypocenter data is needed, so it is important to carry out research. This research aims to relocate the hypocenter using ObsPy with a single station. The results obtained show that the Python package, namely ObsPy, can carry out data retrieval commands through filtering, detrending, normalisation, and determining data request parameters, such as the start and end times of the desired data, location, network, and data type. This research contributes to the field of seismology because the process of determining the hypocenter requires a relatively short time. Apart from that, the accuracy obtained also provides accurate values.

Multiple Linear Regression Method for Thermal Maturity Prediction Based On Well Logs

Rahmat Catur Wibowo — 2024-06-29

Accurate estimation of thermal maturity is essential in characterizing a source rock, especially using vitrinite reflectance (Ro). The limitations of laboratory data related to the high cost of analysis require a special reliable method to measure the Ro value indirectly in the source rock layer. The proposed method is a continuous prediction of the value of Ro from well logs data using the Multiple Linear Regression (MLR) technique in the Palembang Sub-Basin, South Sumatra Basin. A total of 25 Ro data from 2 wells (RCW-01 and RCW-02) are available from the laboratory's core data analysis results. The Ro data varies from 0.39% to 0.76%, with an average of 0.54%. Prediction of the value of Ro is carried out using the MLR method, which is then carried out training and validation for continuous Ro. The training was carried out using one well (RCW-01) at 2287-3027 m and testing at other intervals (1848-2286 m). The results of the training show an estimation accuracy of R² 0.99, while the test results produce R² 0.81. The MLR formula in the RCW-01 well was then applied to the RCW-02 well for the validation test phase. The well RCW-02 produces a good correlation estimate equal to R² 0.85. Prediction of the value of Ro using the MLR method can be used to evaluate the source rock layer of a sedimentary basin in the form of a continuous interval.

Provenance Analysis Based On Petrographic Samples On EXIA-1 Well, Banggai Basin, East Sulawesi, Indonesia

Reddy Setyawan — 2024-06-29

The structure of Exia is composed of Miocene built-up carbonates formed by shear faults. The buildup carbonate feature in the Exia prospect can be seen from the high elevation surrounded by lows with an NNE-SSW and NE-SW trending. The MA-1, SE-1, MI-1 wells are several wells in the Tiaka and Senoro Fields which are proven to have large gas reserves. Tiaka Field is located to the west of the Exia Well, while Senoro Field is to the northeast. The study used primary data from the Exia-1 well in the form of cutting samples. The wet and dry cutting samples were further processed into thin section. This thin section is then carried out for petrographic, XRD, and SEM analysis. Tomori Formation starts from the deeper environment FZ1 upwards to the shallower FZ5 –FZ6 (reef) with open marine and restricted areas. The allochem that composes the limestone at The Matindok Formation consists of red algae fragments and benthic forams which indicate the facies zone of formation in FZ 4 (slope). In the upper Mantawa Formation, it is still quite clear the presence of large forams indicating a reef association environment (FZ5-FZ6), but the presence of a large number of planktonic forams indicates a deeper depositional environment / slope, so it is possible that large forams were transported from a shallower environment. The Kintom Formation have rock provenance ranging from continental blocks in the interior of the craton to a recycled orogeny section of recycled quartz zone.

Metamorphic Complex Deformation in North Bangka Island Based on Macrostructures and Microstructures Evidences

Rezki Hendrawan — 2024-06-29

The northern Bangka Island is composed of Pemali metamorphic complex which is indicated by the collision between Indochina and Sibumasu blocks. These features are interesting to observe because the metamorphic rocks could be recorded in some geological structures at different times. The study began by conducting field observation on Pemali Metamorphic Complex as objects. Field observation aims to collect lithological data, structural data, and oriented rock samples. The results of field pitching were processed to determine macrostructures, microstructures, and mineral distribution. The data was analyzed based on kinematic, descriptive, and deformation mechanisms to determine the deformation patterns that occurred in the study area.

Field and oriented thin section data show structures and occurred in different deformation conditions. The analysis based on macrostructures and microstructures showed that the northern part of Bangka Island experienced three different deformation phases. Deformation begins with the formation of folds that are associated with collisions between Sibumasu-Indochina, followed by a second deformation that forms a fold with different verging. Both deformations are formed in the ductile zone and the brittle-ductile transition zone. The third deformation occurs when rocks have been lifted to the surface by the presence of faults, joints, and veins. The sequence of the deformation model is similar to the deformation experienced in the Bentong-Raub suture zone formed in the shear zone.

Slope Stability Analysis Using the Rock Structure Rating (RSR) Method And Atterberg Limit at Riau - West Sumatra Cross road Km 165 Harau Subdistrict, Lima puluh Kota Regency, West Sumatra Province

Tessema Ogie Damares — 2024-06-29

Stability on the slope was considered important for the safety of people who pass through the highway. Failure of slopes on highways can cause losses especially roads had an important role in community activities. The research was located on the Riau – West Sumatra Km 165. The purpose of this research was to find out treatment or mitigation that can be given to the research slope and know the soil classification based on the analysis Atterberg Limit. The research slope was divided into 3 parts using analytical Rock Structure Rating (RSR) method based on different slope conditions. And 1 part of the slope that has become soil using the analytical method Atterberg Limit. Treatment or mitigation that can be given to the research slope, namely the use of rock shopandshotcrete based on the RSR diagram and the use of rock embankments to resist landslides.

Tsunami Modeling Using DEMNAS and DEM Data from UAV Surveys for Planning Evacuation Routes on Samas Coast, Bantul Regency

Sulpisius Sihombing — 2024-06-29

The interaction between the Indo-Australian plate and the Eurasian plate exerts significant influence on seismic activities within the southern seas of Java Island, with potential repercussions extending to the triggering of tsunamis. Given the densely populated nature of this area, especially along the southern region of Yogyakarta Province, the coast of Samas Beach and its surroundings, mitigation efforts are needed to reduce the potential loss of life caused by tsunamis. One of the mitigation efforts is making a tsunami model which can be done using the help of DEMNAS and DEM topographical data from unmanned aerial vehicle (UAV) photogrammetry. The COMCOT software is a tool used in modeling tsunamis based on a numerical model of the shallow water equation that processes tsunami generator parameters and DEM data into an accurate tsunami model. The modeling results show that the tsunami waves will reach the Samas coast in the 38th minute after the occurrence of the earthquake. The maximum height of the tsunami inundation obtained using DEMNAS data was 21.72 m while using the UAV-DEM it was obtained 23.34 m. Comparison of modeling using DEMNAS and UAV-DEM data shows that image data collection using UAV has good resolution and has high accuracy so that it is able to produce a tsunami model that better shows the propagation of a tsunami in the actual field. The location used as a temporary/final evacuation site is Tegalsari Elementary School because of its strategic location and in tsunami modeling, this location is in the very low risk zone.

Water and Reinforced Effects on Slope: Case Study on District Koto Panjang, Riau, Indonesia

Soewignjo Agus Nugroho — 2024-06-29

This paper discussed a study case related to slope stability and its analysis. The observation and also research object was a hill side on border area between West Sumatera-Riau, Indonesia. This border area consists of numerous slopes with heterogeneous soil characteristics. This location is also susceptible for having landslides, especially on rainy season. The schemes of this research consisted of collecting samples, laboratory tests, finite element method analysis, and slope`s reinforcement planning with anchors or geosynthetic plates. The soil samples were tested on their actual condition and liquid limit condition. This purposed to predict the failures on slope. Afterwards, some reinforcement plannings need to be done. The results of this researach have shown that on existing condition, the safety factor was 1.262. If the soil reach its liquid limit, the safety factor decreased to 0.568. After the reinforcement planning was done, the safety factor went up to 1.120 and the slope stability could be maintained.

Economic Work Evaluation Of New Zone Behind Pipe Based On Psc Cost Recovery And Gross Split Contract In YL Field

Tania Indah Danastri — 2024-06-29

Oil production in the YL field has decreased, to increase production work was carried out New Zone Behind Pipe (NZBP). For production results to benefit contractors and the government, this project was carried out by grab into account operating and investment costs following the standard cooperation contract system that applies in Indonesia. This study aimed to calculate the economic indicators of NPV, IRR, and POT based on the PSC system cost Recovery and system gross Split. Then determine which contract was feasible more or better by comparing the final results of the economic indicators of PSC contracts and economic indicators of contracts Gross Split. This study produced a comparison based on the system growth Split more wells were considered feasible, namely 6 of the 12 wells studied, with oil production above 2.65 MSTB to 9.71 MSTB, respectively the NPV, IRR, and POT values were 11.90 to 52, 5, 11% to 40%, 0 to 4.22 months. While the PSC system only 5 wells were considered feasible out of 12 wells, with oil production of 1.82 MSTB to 9.71, respectively the NPV, IRR, and POT values were 13.2 to 189.80, 11% to 156%, and 0 to 6.47 months. The system Gross Split was the best cooperation contract system to be applied to the YL field.

Evolution of T. simplex, Jenkins from the Middle Miocene to the Early Pliocene and its Chances of Becoming a Distinct Subspecies

Hita Pandita — 2024-06-29

The presence of Turritellidae fossils in rocks is very important, because they are index fossils at the levels of mollusk biostratigraphy in Indonesia. However, its use is not yet optimal, due to one of the reasons being different names for the same specimen or conversely giving the same species name to different forms. One example is Turritella simplex. This research is intended to re-identify Turritella simplex originating from two populations that have different shapes and sizes. The goal is to find out whether the two populations are the same or different species. The method used is the analysis of the similarity of the identification parameters and the similarity test of the biometric patterns. The results showed that the two populations from Cilanang and Meningten showed similar morphological identification parameters, but differen in biometric aspects. The recommendation from this research is to divide it into two different subspecies, and can be represented at different biostratigraphic levels. Both populations show an evolutionary process in terms of biometry and morphology.

The Mitigation of Risk Management: Non-Productive Time Analysis on Drilling Operations in ZY Field

Muhammad Ariyon — 2024-06-29

Currently, petroleum is still the main energy source in Indonesia. However, since the 1990s, Indonesia began to experience a decline in oil production and an increase in domestic energy demand, which caused Indonesia to import oil to meet domestic energy needs. Through SKK Migas, Indonesia has a target to produce 1 million barrels per day by 2030, with one of the efforts being undertaken by carrying out massive and aggressive drilling. Drilling is the most critical, dangerous, complex and expensive operation in the oil and gas industry. It cannot be denied that in reality many unplanned problems (unscheduled events) which result in non-productive time (NPT) are encountered during drilling operations which sometimes cause unpredictable budget usage and can also result in delays in hydrocarbon production. This research was carried out by analyzing 50 wells that had been drilled in the BR field. In this research, a risk management process was carried out for the NPT categories to determine the level of risk in each NPT category and develop a mitigation analysis to reduce the NPT. Dealing with the finding, it indicates that the NPT rig moving (RMV) and drilling 8-1/2 (DRLG 8-1/2) categories have a red risk level which means unacceptable. The biggest contribution to NPT in the RMV category is location problems, while for DRLG 8-1/2 it is loss of circulation

Modeling and Interpretation of Geothermal System Components Using the Gravity Method at the “X” Geothermal

Mochammad Malik Ibrahim — 2024-06-29

Geothermal field "X" is one of the geothermal fields located in North Sulawesi Province managed by PT Pertamina Geothermal Energy. This research aims to determine the presence of geothermal system components in the subsurface using the gravity method. Gravity method data processing is processed with observational and theoretical corrections to obtain a complete Bouguer anomaly. The complete Bouguer anomaly is separated into regional and residual anomaly using the upward continuation process. The results of modeling and interpretation of residual (shallow) gravity prove the existence of 3 (three) rock layers and their density values, Post Tondano Andesite Unit layer (2,4 g/cm³), Tondano Rhyolite Unit layer (2,5 g/cm³) and Pre Tondano Andesite Unit layer (2,7 g/cm³). The results of modeling and interpretation of regional (deep) gravity evidence the existence of 3 (three) rock layers along with the rock density value, Tondano Rhyolite Unit layer (2,5 g/cm³), Pre Tondano Andesite Unit layer (2,7 g/cm³) and diorite intrusion rock layer (2,9 g/cm³). The geothermal system in the research area is composed of Post Tondano Andesite Unit as overburden rock, Tondano Rhyolite Unit as caprock, Pre Tondano Andesite Unit as reservoir rock and Diorite intrusion rock as heat source.

Analysis of Subsidence Hazards in Pandan Cave Area, Giri Mulyo Village, Marga Sekampung District, East Lampung using Analytical Hierarchy Process

Bilal Al Farishi — 2024-06-29

Pandan Cave is a basalt lava cave which is a unique geological tourism area located in Giri Mulyo Village, Marga Sekampung District, East Lampung Regency, Lampung Province. This cave was formed when the lava flow cooled at the top because it was in contact with the cold atmosphere, while at the bottom it was still flowing. This uniqueness caused Pandan Cave to become one of the tourist attractions that was once crowded with tourists. However, the condition of this cave is still very natural which can lead to the risk of geological disasters such as subsidence which can endanger tourists, so it is necessary to research to minimize the occurrence of geological disasters in the area. This research was conducted by observing aerial photographs, collecting data directly in the field, and then processing it with the Analytical Hierarchy Process (AHP). Parameters used in this AHP method include lithology, vegetation, weathering, rock mass class, and cave roof thickness. The existence of subsidence in the study area is influenced by weathering (34%), vegetation (31%), thickness of the cave roof layer (16%), lithology (10%), and rock mass class (9%). Based on the overlay results for each parameter that has been weighted, the Pandan Cave tourism area is divided into three subsidence hazard zone classifications, that is low hazard zone with value of 0.28-0.44, medium hazard zone with range of 0.44-0.60, and high hazard zone with range of 0.60-0.75. Through the Analytical Hierarchy Process (AHP) method and overlay of each parameter used, the distribution of subsidence hazard zones in the study area was obtained. The low threat zone of 27.57 ha is about 57.07% of the total research area, the medium threat zone is 15.86 ha or about 32.83% of the total research area, and the high threat zone is 4.88 ha or about 10. 10% of the total research area.

Spatial and Seasonal Variation of Doline Water Hydrochemistry in West Gunungsewu Karst Area, Yogyakarta Special Region, Indonesia

T. Listyani R.A. — 2024-06-29

The doline water hydrochemical study was conducted in the Gunungsewu karst area, Yogyakarta Special Region. The hydrogeological survey followed by doline water sampling was carried out in the Panggang and Wonosari-Baron Hydrogeological Subsystems. Ten selected doline water samples were taken, each in the dry and rainy season, for further physical/chemical testing in the laboratory. Research analysis includes hydrochemical analysis of several parameters such as pH, TDS, EC, major and minor ions content and assisted by difference and variability tests statistical analysis. The hydrochemical variations of doline water in the study area generally did not show any spatial variations, except for the EC parameter. Temporal/seasonal hydrochemical variations are apparent, as evidenced by differences in many variations of TDS, EC, major ions (Ca²⁺, Na⁺, K⁺, HCO₃^-, Cl^-), and minor ions (sulfate and nitrate). In the dry season, the hydrochemical facies generally develop as Ca, Na-bicarbonate facies, while in the rainy season, doline water typically has Ca-bicarbonate facies. The hydrochemical of doline water may be influenced by groundwater.

The Exotic Beauty of Karst Morphology of Langgun Island and Geotourism Potential of Langkawi Island, Malaysia

Catur Cahyaningsih — 2024-06-29

The research area is located in the eastern part of Langgun Island, Langkawi, Malaysia. Several small islands in the area are included in the research scope, including Anak Tikus Island, Anak Berangan Island, Batang Tunggang Cape, and Langgun Cape. Research on karst geomorphology is still very poor in the research area, especially regarding the classification and the history of the formation. The main motivation for this research is to reveal the beauty and uniqueness of the karst morphology of the research area, which is one of the most valuable geological heritages. Chemical weathering caused by surface water and underground water causes the limestone exposed on this island to form an island karst landscape. The karst morphology in Langgun Island is classified into exokarst and endokarst geomorphology. The morphology of exokarst is divided into two, namely negative exokarst and positive exokarst. The negative exokarst geomorphology found in the study area is dolina and uvala. Meanwhile, the morphology of positive exokarst consists of weathering island karst, which is karst resulting from wave erosion (tombolo, sea stumps, abrasion platforms, sea notches), and residual hills (karst tower and karst cone). The endokarst morphology found is the stalactite feature. This research will be able to increase understanding of karst development so that it forms a unique, beautiful morphology and increases the value of tourism potential, especially in the research area to influence tourist to visit.

Classification and Distribution Of Mangrove Genus Using Multispectral Unmanned Aerial Vehicle (UAV) In The Waters Of Lancang Island, Kepulauan Seribu, Indonesia

Armanda — 2024-06-29

Mapping of mangrove distribution is important as basic information in mangrove resource management. development of remote sensing technology with multispectral unmanned aerial vehicle (UAV) with high spatial resolution. This study aims to determine the classification and distribution of mangrove genera using a pixel-based classification method and calculate the accuracy level of mangrove genus classification using a multispectral unmanned aerial vehicle (UAV) in Lancang Island Waters, Kepulauan Seribu. This research was carried out in August 2023 by obtaining 481 mangrove genus observation points using the DJI Phantom 4 multispectral drone. Image classification was processed using a pixel-based classification method with two classification levels, including level 1 (mangrove), resulting in an area of 18.72 ha. Level 2 (mangrove genus) uses guided classifications such as Support Vector Machine (SVM), K-Nearest Neighbor (KNN), and Random Forest (RF). Based on the classification results, the best results were obtained using the RF algorithm with an accuracy of 89.78% and a kappa index of 0.51, followed by the SVM algorithm with an accuracy of 89.78% and a kappa index of 0.45, then using the KNN algorithm with an accuracy of 88.32% and a kappa index of 0.43.