Jurnal Geofisika Eksplorasi
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PENDUGAAN PATAHAN DAERAH “Y†BERDASARKAN ANOMALI GAYABERAT DENGAN ANALISIS DERIVATIVE
Full text linkThe research area "Y" is an area of gold mineralization with low sulfidation epithermal type deposit. The existence of this type of mineralization on the path marked by the presence of mineral deposits, which form the quartz veined below the surface of the deposited within the structure of the fault. In this study, analysis of gravity data using derivatives analysis, i.e. First Horizontal Derivative (FHD) to determine the boundary fault structure and Second Vertical Derivative (SVD) to determine the type of fault. The existence of the fault structure integrated with subsurface modeling results in two-dimensional and three-dimensional. The results showed three line slice made in the area of research, identified structure of down faults (normal) trending northeast - south on slice 1 with an estimated dip (slope) is 22° and expected of strike on this fault is N 158° W and thrust fault structure trending northwest - south on slice 2 also slice 3 with an estimated dip (slope) is 22° and expected of strike on this fault is N 158° E. The results of the modeling of two-dimensional and three-dimensional show fracture structure is at the density of 2 g/cc – 2,67 g/cc in the depth of around 100 m - 250 m that consists of sedimentary rocks (clay and sandstone) with a density of 2,2 g/cc – 2,3 g/cc at the age of Tertiary Pliocene, tuff rock with a density of 2,4 g/cc – 2,5 g/cc at the age of Early Miocene and bedrock (basement) in andesite form with a density of 2,67 g/cc
PREDIKSI POROSITAS MENGGUNAKAN METODE NEURAL NETWORK PADA LAPANGAN OZZA, CEKUNGAN SUMATRA TENGAH
Full text linkInformation from geological structures that are considered to contain hydrocarbons may not necessarily contain economical hydrocarbons, so additional analysis is needed to determine the position of new wells. Seismic and log methods can be used to determine areas considered prospective for oil and gas exploration. Seismic analysis method developed to be able to integrate seismic data and log data is a neural network. Neural network is a data processing to get a non-linear approach of the statistical relationship of the input data to the output data, then distributed to all seismic volumes. The results of the study of sand reservoir characteristics in the Ozza Field have a porosity value of more than or equal to 20%, and for shale it has a porosity value of less than 20%. The correlation between the original porosity value and predictive porosity is that the higher the porosity value in the original log the higher the value of the neural network porosity, and vice versa. The porosity distribution map in the prospect area has a higher porosity value than the surrounding area. The prospect zone for new exploration is in the southwest area of the study area
Analisis Model Kecepatan Gelombang-P pada Coal-Seam Gas Studi Kasus Cekungan Sumatera Selatan, Indonesia
Full text linkThe rock physics model is one effective yet challenging way to investigate the coal-seam gas potential in Indonesia. However, because of the complex conditions of the Coal-Seam Gas Reservoirs, it is difficult to establish models. Despite the scarce modeling, this study aims to estimate the relation of gas-saturated within pores of coal seam to the elastic properties of rock, which is P-wave velocity. First, the coal seam minerals are applied to quantify matrix moduli using the Voigt-Reuss-Hill Average method. Pride’s simple equation is used to estimate the elastic properties of the coal seam at dry condition (zero gas saturation). Finally, Biot-Gassmann’s theory is applied to determine the elastic properties of coal seam with fully gas saturated. As the result, the proposed model showed that there is a significant negative correlation between gas content with both density and P-wave velocity of the coal seam. Finally, this P-wave velocity model of gas-saturated coal seams should be properly useful as the quick look for identifying coal seam gas potentials.Â
IDENTIFICATION OF ANDESITE ROCK BASED ON THE RESISTIVITY VALUE IN SATUI AREA, SOUTH KALIMANTAN
Full text linkAndesite rock identification has been carried out in Satui, South Kalimantan using the geoelectric method. Four lines resistivity measurement using Wenner configuration are used with a length of 200-350 m. The purpose of this study is to determine the depth, thickness and position of andesite rocks in the measurement area. Based on the results of processing there are three types of layers in the measurement area, clay with a resistivity of 9.760-68.373 Ωm, sandstones with a resistivity value of 68.373-324.509 Ωm and andesite with a resistivity ≥ 324.509 Ωm. The results of 2D interpretation show that the andesite rock in the entire first path are at a distance of 10.00-170.00 m, depth 6.76-9.94 m and thickness 7.36-10.54 m. Andesite in the second lane are found at a distance of 80-345 m, depth 1.25-9.94 m and thickness 2.62-10.54 m, on the third lane found at a distance of 100.00-200.00 m, depth 13.40 m and 3.90 m thick. Andesite in the fourth lane are found at a distance of 5.00-175.00 m with a depth of 6.76-13.40 m and thickness 1.95-10.54 m
ANALISA LUASAN TERUMBU KARANG DI PERAIRAN PULAU TEGAL LAMPUNG DENGAN TEKNOLOGI PENGINDERAAN JAUH
Full text linkDamage to coral reefs on Tegal Island has an impact on reducing coral reef habitats, so monitoring needs to be done. Monitoring is done by analyzing the extent and changes by utilizing remote sensing technology to map the existing conditions. The data used are Landsat imagery in 1998, 2008, 2015 and 2018. Digital image processing is done starting from image correction, lyzenga algorithm calculation, image interpretation and field validation, and accuracy testing of coral reef habitats using a confusion matrix. The results showed that there was a change in the area of coral reefs from 1998 to 2018. The coral reef class experienced a reduction of 11.22 ha. Coral classes that changed into sand classes were 9.13 ha (29.49%) and seagrasses were 4.38 ha (14.15%). The class of sand that turned into coral reefs was 2.08 ha (13.52%) and seagrass classes that turned into coral reefs were 0.21 ha (0.25%). The biggest change is the change in the coral reef to sand covering an area of 9.13 ha (29.49%), while the smallest change is the change in seagrass into a coral reef covering an area of 0.21 ha (0.25%). In the other classes, the biggest change in area was seagrass change into sand covering an area of 5.76 ha (6.96%), while the smallest change was the change in the sand to seagrass covering an area of 2.67 ha (17.35%)
KAJIAN LOKASI POTENSIAL PERUMAHAN DAN PERMUKIMAN DI KABUPATEN PESAWARAN DENGAN SISTEM INFORMASI GEOGRAFIS (SIG)
Full text linkPesawaran District, as a new district which was established in 2007, has experienced a rapid growth in population. As the population increases, housing and residential land needs will increase. Therefore, there should be a careful planning in determining the location of housing and settlement development in Pesawaran District. This study aims to: 1) Know the weight for each parameter used in determining the level of potential for a land for the development of housing and residential areas with method AHP 2) Know the potential level of land in Pesawaran District for the development of housing and settlements. The method used is AHP (Analytic Hierarchy Process), while the method by spatial analysis using GIS (Geographic Information System).The results of the study with AHP calculations show that the most dominant parameter is accessibility. The reason is, accessibility will affect the ease of transportation services and affordability of distance. The results of the analysis using GIS resulted in 5 potential locations for the development of residential and residential areas in Pesawaran District which are very potential (13456.50 ha), potential (47941.61 ha), quite potential (47362.11 ha), less extensively potential (16107.09 ha), and no potential (8251.13 ha)
INVERSI 2D DATA MAGNETOTELURIK UNTUK MENGETAHUI KEBERADAAN HIDROKARBON DAERAH BULA, MALUKU
Full text linkThere had been done a regional research which tittle is “2D inversion magnetotelluric data for understanding the hidrocarbon presence in Bula, Malukuâ€. This study aims to determine the resistivity distribution area of research based on data Magnetotelluric, identifying the presence of hydrocarbons based on the value of the resistivity of the results of 2D inversion of data Magnetotelluric. Methods of data processing done are (i) transform raw data from the time domain into the frequency domain, (ii) reduce noise by robust processing, (iii) process combine, (iv) Selection cross power, (v) inversion 1D and 2D. 2D inversion results is sectional subsurface resistivity distribution, layer having resistivity values 7-16 Ωm along MT1 and MT7 point at a depth of 1000 meters is a clay stone which is indicated as cap rock. Layer with resistivity values 34-120 Ωm, which is between the point MT6 and MT7 at a depth of 1500 meters is indicated as the sandstone reservoir. Based on geologic information and sectional 2D inversion seen their fault based on the resistivity contrast is between the point MT2 and MT3, MT3 and MT4 and MT6 and MT7
ALTERNATIF PEMODELAN NUMERIK KOPEL THERMO-HYDRO -MECHANIC INJEKSI CO2 PADA FORMASI GEOLOGI BAWAH PERMUKAAN
Full text linkCO2 injection into subsurface formations is a potential method to reduce CO2 gas emissions in the atmosphere. Geological and geophysical studies are carried out as an effort to analyze the storage capacity and potential risks. The results are then used to analyze the response of reservoir rock to the injected CO2 fluid. The effect of fluid injection on reservoir rocks is complex and involves a coupled system of fluid flow-geomechanics. CO2 fluid injection can increase fluid pressure that affects the local stress conditions of reservoir and surrounding rock. Meanwhile, changes in temperature due to the presence of CO2 fluid also affect reservoir rock stress, although not significantly. The complexity of the subsurface reservoir system includes thermomechanical and hydromechanical analysis involving multi-phase and multi-component fluids. To study these complex interactions, a program which can simulate the coupling between multi-phase and multi-component fluid-flows-geomechanics is needed. To accommodate these needs, Rutqvist et al (2002) have proposed a numerical modeling approach by linking TOUGH2-ECO2N and FLAC3D. In this study we developed an external program that linking TOUGH2 with different fluid modul (ECO2M), and FLAC3D using these approaches to run the coupled THM simulation automatically and seamlessly until the end of simulation
PERBANDINGAN NILAI PERCEPATAN TANAH MAKSIMUM BERDASARKAN MODIFIKASI KONSTANTA ATENUASI DAN DATA ACCELEROGRAPH TAHUN 2008-2016 PADA STASIUN BMKG LAMPUNG
Full text linkPeak ground acceleration is one of the parameters used in estimating the extent of breakdown caused by earthquake shocks. In the present study, the determination of an attenuation empirical formula PGA (Peak Ground Acceleration) based on the attenuation equation Lin and Wu (2010). Data used in the study of seismic event data by period year 2008-2012. Through the calculation of regression analysis, then obtained the function attenuation of peak ground acceleration in Lampung region at each station accelerograph.At the LWLI accelerograph station obtained the value of the empirical coefficient of the distance of earthquake -2.351, the empirical coefficient of earthquake magnitude 0,574, and the constant 2,430. At the KASI accelerograph station obtained the value of the empirical coefficient of the distance of earthquake -2.522, the empirical coefficient of earthquake magnitude 0.654, and the constant 2.182. At the BLSI accelerograph station obtained the value of the empirical coefficient from the distance of earthquake -3.224, the empirical coefficient of earthquake magnitude 0.651, and constant 4,092. At the KLI accelerograph station obtained the value of the empirical coefficient from the distance of earthquake -2.746, the empirical coefficient of earthquake magnitude 0.751, and the constant 2.053.Result of correlation test verification, chart relation between distance and magnitude earthquakes, ratio PGA contour maps, as well as a ratio between the value of PGA models with the observation of accelerograph year 2013-2016 show that the acceleration attenuation function of the obtained soil is relatively good. Based on PGA attenuation contour map model at an event the earthquake on 28th May 2011, PGA great value be found in the Liwa region with a PGA score of 10-20 gal and its seismic intensity value is V-VI MMI. It happens because of the source the earthquake is in the western sea of Liwa
PEMETAAN MIKROZONASI DAERAH RAWAN GEMPABUMI MENGGUNAKAN METODE HVSR DAERAH PAINAN SUMATERA BARAT
Full text linkRegional Painan, the distric of Pesisir Selatan, the province of west Sumatera is one of the areas with high risk disaster prone. This study aims attempts to maped the disaster prone area of the Painan region based on the dominant frequency value, Vs30, PGA and amplification and to know the value of ground movement from the area. By using the HVSR method (Horizontal to Vertical Spectra Ratio) expected to assist to zone the regions. Based on the research that has been done, it is known that the Painan area, West Sumatera, have values of dominant frequency between 0.6 to 12.07 Hz. As for the value Vs30Â between 73.08 to 1449 m/s and the amplification values between 0.47 to 6.01. The PGA value for Painan region between 0.034 to 0.063 g. Based on the analysis that has been done by correlating the four zoning map, it is known that the area which has a high risk of earthquake disaster that is estimated to coastal areas. This is supported by the dominant low frequency value and the value Vs30 small and PGA of high value. The amplification value of this region is divided into four zones, areas that have amplification is very high being around the beach and composed by rock alluvial, the value of amplification of high contained in nearly all the regions Painan while amplification medium and low are the small area of Painan and the small area of Bungo Pasang Salido because based on the geological map of the area is composed of two types of rocks are alluvial and rock Painan Formations