Indonesia Conference Directory

Corresponding Author
Muhammad Zaki

Institutions
(1) Geophysical Engineering, UPN Veteran Yogyakarta, Jalan SKW 104 Lingkar Utara, Yogyakarta 55283, Indonesia
(a) wahyu.hidayat[at]upnyk.ac.id

Abstract
Wonogiri Dam is one of the largest dams in Indonesia, located ± 2 km south of the Wonogiri City, in the province of Central Java. Wonogiri Dam has a volume ± 400 million m3 with a surface area of 73,6 km2 which has many benefits such as for agriculture, tourism, and power plant. Wonogiri is a part of the East Java Southern Mountain Zone. There are many rocks types found at Wonogiri, such as volcanic breccias, andesite lavas, tuffs, and many igneous intrusive rocks of the Miocene Mandalika and Semilir Formations, unconformably underlie Quaternary volcanic rocks of Lawu and Merapi Volcanoes (Sutarto, 2013). This research aimed to determine Ground Shear Strain (GSS) value along main dam and the surrounding area and to predict phenomena based on GSS values. From dominant period (TG) value, we can predict site class based on the classification of Zhao et al (2004). The microtremor data was taken on 31 observation points which is divided from 14 observation points with 100 m spacing in main dam and 17 observation points with 1.000 m spacing in surrounding area from Wonogiri Dam. Microtremor data was analysed using Horizontal to Vertical Spectral Ratio (HVSR) method to get amplification factor and dominant frequency. Those data were used to determine the seismic vulnerability index (Kg). Kanai empirical equations was used to calculate Peak Ground Acceleration (PGA) value based on earthquake event on 27th of Mei, 2006 with a moment magnitude of 6,3 and and 11,8 km depth. Seismic vulnerability index and peak ground acceleration value are used to determine the GSS value. The results of this research showed that GSS value in research area was about 3,4 x 10-4 to 7,2 x 10-3. The phenomena that can happen were ground movement as the form of surface cracking and settlement. Seismic vulneribility index was below 20 (0,35 to 16,97) which means surrounding area from Wonogiri Dam and main dam have low-risk, but potential for damage to building is still possible. Along main dam area, we need to notice the point at 400m and 600m. The value of the dominant period in research area ranged from 0.07 to 1.11 second. Based on the classification of Zhao et al (2004), there are 3 classes of site class in the research area.

Keywords
Dam, Ground Shear Strain, Site Class.

Topic
Geophysics,Geomatics and Geochemistry

Link: https://ifory.id/abstract/VcXez6vJdmuH

Corresponding Author
Y Yatini

Institutions
(1)Departement of Geophysics Engineering, Universitas Pembangunan Nasional Veteran Yogyakarta, SWK (104) North Ring Road Street Condong Catur, Yogyakarta55283. Indonesia.
email: jeng_tini[at]upnyk.ac.id
(2)Geophysics Departemant, Universitas Gadjah Mada (UGM), Sekip Utara BLS 21 Yogyakarta 55281
(3)Geophysics Departement, Universitas Brawijaya, Jl. Veteran, Malang 65145

Abstract
Sileri Crater is a manifestation of the Dieng Volcanic Complex (DVC) which has a large geothermal prospect. The problem of subsurface conductivity distribution is very important in geothermal prospecting. The geothermal prospects indicated by the presence of manifestations have characteristics of high conducivity values. The conductivity parameters were obtained by the Very Low Frequency (VLF) method. Research in DVC prospect area, precisely around Sileri Crater area using the VLF method, aims to map the subsurface structure through the distribution of conductivity values. VLF data consists of tilt, ellipse, vertical and horizontal magnetic field. VLF data processing is done by using the filter of moving average, Fraser and Karous-Hjelt. Current Density Equivalent (CDE) results are correlated to simplify the interpretation of the conductive zone. The results show that the conductive anomalies on A, B C, and D lines in the east are influenced by the presence of geothermal pipes around the crater. Other conductive anomalies found on the E and F lines are estimated to be caused by the influence of lithological contact between andesite lava and volcanic deposits. Andesite lava responds to conductive anomalies on the measurement results of the VLF method while volcanic deposits lithology has a more resistive.

Keywords
DVC, VLF, conductivity, tilt, fraser and CDE

Topic
Geophysics,Geomatics and Geochemistry

Link: https://ifory.id/abstract/vUjT2dFEeYG8

Corresponding Author
Ardian Novianto

Institutions
Universitas Pembangunan Nasional Veteran Yogyakarta

Abstract
Abstract. Jambakan is a village in Bayat District, Klaten Regency, Central Java Province, Indonesia. Even though it is located ±30 km from the sea, brackish water is found in its aquifers. In light of this, scientific discussion on where this water comes from is deemed necessary. Based on the groundwater quality analysis at the local wells, brackishwater was detected in shallow aquifers at the depths of 5-8 m. The geoelectrical method using the Schlumberger and dipole-dipole electrode configurations screened for any aquifers vertically and horizontally. The results showed that aquifers were distributed discontinuously, for which they were interpreted as fan alluvial deposits in shallow seas or molasses accumulations on the land. The interpretation also revealed that the brackishwater resulted from contacts with minerals in seawater sediments that composed the aquifers in this village.

Keywords
Schlumberger,dipole-dipole,electrode

Topic
Geophysics,Geomatics and Geochemistry

Link: https://ifory.id/abstract/68cGXzxy2JPQ

Corresponding Author
Mau Lina

Institutions
a) University of Lampung, Lampung
*maulln197[at]gmail.com
b) Marine Geological Institute, Bandung

Abstract
Petrophysical analysis of well log data have been crucial for determination of reservoir prospect zone with lithology and hydrocarbon types based on petrophysical parameters. In addition, sensitivity analysis is carried out to determine elastic parameters that are sensitive of lithology variability and pore-fluid type. Based on the crossplot results, parameters such as Lambda-Rho, Mu-Rho, and VpVs ratio can detect lithology and pore-fluid types because they are sensitive to porosity and rock matrix characteristics. This study focuses on reservoir characterization of ‘MS- well on Late-Miocene N17 rock formation which was classified as a shelf carbonate matrix. The petrophysical parameters are carried out such as porosity ( ), water saturation (Sw), shale content (Vshale), and formation water resistivity (Rw) using density and neutron logs calculation, Indonesian-s equation, and qualitative analysis approcach. Based on the results of petrophysical analysis it is known that the reservoir zone is at 5003-5297 ft with total thickness 101 ft netpay. The reservoir has a limestone lithology with Gamma Ray-s value between 15-55 API. The hydrocarbon prospect zone is indicated by the separation of NPHI and RHOB curves with low value, porosity 18.5%, water saturation 37%, and water resistivity shows 0.12-0.13. The reservoir zone is indicated by the cut-off of Lambda-Rho <25 GPa*gr/cc, Mu-Rho <70 GPa*gr/cc, and VpVs ratio <2. Finally, both the petrophysical and sensitivity analysis show indication of fresh water biogenic gas reservoir.

Keywords
petrophysical and sensitivity analysis; reservoir characterization; lithology; carbonate; Nias basin

Topic
Geophysics,Geomatics and Geochemistry

Link: https://ifory.id/abstract/L794QjvweZEH

Corresponding Author
Wiji Raharjo

Institutions
Geophysical Engineering, Universitas Pembangunan Nasional Veteran Yogyakarta, Jl. SWK 104 Condongcatur, Depok, Sleman, Yogyakarta, Indonesia 55283
* wiji.raharjo[at]upnyk.ac.id

Abstract
Geomagnetic 3D modelling can be done by varying inclination angel for each layer and Talwani method to build the initial model as forward modelling formulation. In modelling process, random noise distribution is always needed to build synthetic data from observation data. There are two kind of random noise distribution used in this research. They are uniform distribution and Gaussian distribution. This concept then applied in satellite data of magnetic intensity in Sintang, West Borneo. Sintang is chosen because it is rich of mineralization and off course has big potential of susceptibility. Based on modelling inversion result, uniform distribution is better in separate big and low anomaly of susceptibility contrast than Gaussian distribution in this research-s data

Keywords
3D modelling, geomagnetic, Talwani method, uniform and Gaussian distribution

Topic
Geophysics,Geomatics and Geochemistry

Link: https://ifory.id/abstract/7cyPZn2Kmdeh

Corresponding Author
Tiara Ayu Ningratri

Institutions
a) University of Lampung, Lampung
*tiaraayuratri[at]gmail.com
b) Marine Geological Institute, Bandung

Abstract
Cross plot analysis of well log data and its calculated elastic atributes are one of the most effective methods to discriminate lithology and fluid type, because the geophysical rock properties analysis is relatively less time and cost compare to other method such as geological core sample analysis. This study uses well log data analysis based on cross plot, lithology separation, fluid type distribution map of 5 (five) wells at Nias Waters. The inverse of the interval transit times of the sonic logs are used to generate computed compresional velocities and Castagna-s formula for predicting S-wave data. Employing rock physics algorithms, rock properties including elastic attributes such as LambdaRho, MuRho, and Vp/Vs ratio are also extracted from the well log data. Cross plotting is carried out and plots with the most outstanding results are LambdaRho - Vp/Vs, MuRho - Vp/Vs, LambdaRho - Density, MuRho - Density, and AI - Vp/Vs. For the one well considered, the MT-1 well and its formation N10-N11 interest zone, those cross plots can identify lithology and fluid type. It determines formation N10-N11 as a gas carbonate reservoir with average porosity 23% which indicates that proper gas flow in the reservoir. Finally, the cross plot analysis are suitable to characterize reservoirs lithology and fluid type.

Keywords
cross plot analysis; Castagna-s formula; carbonate reservoir; Nias Waters

Topic
Geophysics,Geomatics and Geochemistry

Link: https://ifory.id/abstract/EW2r7U6Nfvwp

Corresponding Author
Tiara Ayu Ningratri

Institutions
a) University of Lampung, Lampung
*tiaraayuratri[at]gmail.com
b) Marine Geological Institute, Bandung

Abstract
Cross plot analysis of well log data and its calculated elastic atributes are one of the most effective methods to discriminate lithology and fluid type, because the geophysical rock properties analysis is relatively less time and cost compare to other method such as geological core sample analysis. This study uses well log data analysis based on cross plot, lithology separation, fluid type distribution map of 5 (five) wells at Nias Waters. The inverse of the interval transit times of the sonic logs are used to generate computed compresional velocities and Castagna-s formula for predicting S-wave data. Employing rock physics algorithms, rock properties including elastic attributes such as LambdaRho, MuRho, and Vp/Vs ratio are also extracted from the well log data. Cross plotting is carried out and plots with the most outstanding results are LambdaRho - Vp/Vs, MuRho - Vp/Vs, LambdaRho - Density, MuRho - Density, and AI - Vp/Vs. For the one well considered, the MT-1 well and its formation N10-N11 interest zone, those cross plots can identify lithology and fluid type. It determines formation N10-N11 as a gas carbonate reservoir with average porosity 23% which indicates that proper gas flow in the reservoir. Finally, the cross plot analysis are suitable to characterize reservoirs lithology and fluid type.

Keywords
cross plot analysis; Castagna-s formula; carbonate reservoir; Nias Waters

Topic
Geophysics,Geomatics and Geochemistry

Link: https://ifory.id/abstract/UZHAmBK6P9gh

Corresponding Author
Adelia Irna Santika

Institutions
a) Department of Geophysical Engineering, UPN “Veteran” Yogyakarta
*corresponding author: adeliairnasantika[at]gmail.com
b) Marine Geological Institute, Bandung

Abstract
Surface Related Multiple Elimination (SRME) technique is known to have ineffectiveness to attenuate shallow water multiples, primarily because the water-bottom reflection required by SRME for predicting the multiples is not recorded due to lack of near offset data. The conventional technique using predictive deconvolution in either x-t or tau-p domain is often used to suppress these multiples, however, it also attenuates primary events that have a periodicity close to that of water layer. These limitations cause unrealistic seismic images in final output. In this paper, we propose an enhanced technique by modelling the water-bottom reflection and then adding it to the recorded seismic data. The modified data can then be used to predict first order multiple. We present multi stages processing workflow for removing water-bottom multiples in shallow water situations. Firstly, we use a multi-channel prediction filter estimated from the multiples for attenuating short-period water-layer related multiples. Secondly, we apply F-K filter for isolating signals from noise in frequency-wavenumber (f-k) domain. Lastly, SRME technique for suppressing other long-period surface multiples generated by sub-surfaces underneath the water-bottom. Through real-data examples from Nias Waters, North Sumatra, we demonstrate that our workflow provides an optimal multiple attenuation solution in shallow water environment in comparison with conventional methods such as predictive deconvolution or SRME alone. Tests result show that the multi stages technique can produce better result than using predictive deconvolution or SRME alone. Furthermore, we also show SRME approach can give optimum seismic migration images after we combined these stages. We successfully applied these techniques in 2D seismic data of Nias Waters.

Keywords
shallow water; multiple; predictive deconvolution; F-K filter; SRME

Topic
Geophysics,Geomatics and Geochemistry

Link: https://ifory.id/abstract/zD897qjGWgAd

Corresponding Author
Ajimas Pascaning Setiahadiwibowo

Institutions
1Departement of Geophysical Engineering, Universitas Pembangunan Nasional Veteran Yogyakarta, Indonesia
Jl. SWK No. 104, Ngropoh, Condongcatur, Depok Subdistrict, Sleman Regency, Special Region of Yogyakarta 55283
2Meteorology Climatology and Geophysics Agency Yogyakarta, Indonesia
Jl. Wates KM 8 Jitengan Balecatur, Gamping Subdistrict,, Sleman Regency, Special Region of Yogyakarta 55295

Abstract
Yogyakarta is one of the earthquake-prone areas because it lies near subduction area, the last recorded occurrence of large intensity earthquake activity on 2006, May 27th had a magnitude of 5.9 SR (Richter Scale) and suffered considerable damage. The Department of Social Affairs said that 6,234 people died, 36,299 people were injured and about 1.5 million people were displaced by the earthquake. The earthquake also caused damage to 616,458 residential building units in Yogyakarta and Central Java. Under the USGS, the epicenter of the earthquake is about 25 km southeast of Yogyakarta with a depth of 17.1 km below sea level. Microtremor data with HVSR (Horizontal to Vertical Spectral Ratio) method can be used to determine the value of the predominant frequency spectrum (fo) and amplification factor (A) which describes the dynamic characteristics of the soil. The HVSR analysis method was developed to calculate the ratio of the Fourier spectrum of the microtremor signal to the horizontal component against its vertical component. Calculations regarding the value of soil vulnerability and analysis of subsurface structures are intended to determine the level of vulnerability of an area to earthquake hazards. In the Piyungan sub-district the thickness of the sediment layer (H) ranges from 5 meters to 75 meters below the surface. The northern part of Piyungan sub-district tends to have a thick layer of sediment which is quite thick reaching 45 meters to 75 meters. While the value of the soil vulnerability index in most of the northern part of the study area has a land vulnerability index value that tends to be greater than 40 x 10-6 s2/cm with a maximum value of 78.62 x 10-6 s2/cm. Most of the study areas have soft soil types (Vs < 175 m/s), medium soils (175 m/s < Vs ≤ 350 m/s) and very dense soils and soft rocks (350 m/s < Vs ≤ 750 m/s).

Keywords
Microsroseismic, Horizontal to Vertical Spectral Ratio,Ellipticity Curve, Sediment Layer Thickness.

Topic
Geophysics,Geomatics and Geochemistry

Link: https://ifory.id/abstract/kD7raBteNHng

Corresponding Author
Adelia Irna Santika

Institutions
a) Department of Geophysical Engineering, UPN “Veteran” Yogyakarta
*corresponding author: adeliairnasantika[at]gmail.com
b) Marine Geological Institute, Bandung

Abstract
Surface Related Multiple Elimination (SRME) technique is known to have ineffectiveness to attenuate shallow water multiples, primarily because the water-bottom reflection required by SRME for predicting the multiples is not recorded due to lack of near offset data. The conventional technique using predictive deconvolution in either x-t or tau-p domain is often used to suppress these multiples, however, it also attenuates primary events that have a periodicity close to that of water layer. These limitations cause unrealistic seismic images in final output. In this paper, we propose an enhanced technique by modelling the water-bottom reflection and then adding it to the recorded seismic data. The modified data can then be used to predict first order multiple. We present multi stages processing workflow for removing water-bottom multiples in shallow water situations. Firstly, we use a multi-channel prediction filter estimated from the multiples for attenuating short-period water-layer related multiples. Secondly, we apply F-K filter for isolating signals from noise in frequency-wavenumber (f-k) domain. Lastly, SRME technique for suppressing other long-period surface multiples generated by sub-surfaces underneath the water-bottom. Through real-data examples from Nias Waters, North Sumatra, we demonstrate that our workflow provides an optimal multiple attenuation solution in shallow water environment in comparison with conventional methods such as predictive deconvolution or SRME alone. Tests result show that the multi stages technique can produce better result than using predictive deconvolution or SRME alone. Furthermore, we also show SRME approach can give optimum seismic migration images after we combined these stages. We successfully applied these techniques in 2D seismic data of Nias Waters.

Keywords
shallow water; multiple; predictive deconvolution; F-K filter; SRME

Topic
Geophysics,Geomatics and Geochemistry

Link: https://ifory.id/abstract/Fh3G6axNwEDu

Corresponding Author
Mau Lina

Institutions
a) University of Lampung, Lampung
*maulln197[at]gmail.com
b) Marine Geological Institute, Bandung

Abstract
Petrophysical analysis of well log data have been crucial for determination of reservoir prospect zone with lithology and hydrocarbon types based on petrophysical parameters. In addition, sensitivity analysis is carried out to determine elastic parameters that are sensitive of lithology variability and pore-fluid type. Based on the crossplot results, parameters such as Lambda-Rho, Mu-Rho, and VpVs ratio can detect lithology and pore-fluid types because they are sensitive to porosity and rock matrix characteristics. This study focuses on reservoir characterization of ‘MS- well on Late-Miocene N17 rock formation which was classified as a shelf carbonate matrix. The petrophysical parameters are carried out such as porosity ( ), water saturation (Sw), shale content (Vshale), and formation water resistivity (Rw) using density and neutron logs calculation, Indonesian-s equation, and qualitative analysis approcach. Based on the results of petrophysical analysis it is known that the reservoir zone is at 5003-5297 ft with total thickness 101 ft netpay. The reservoir has a limestone lithology with Gamma Ray-s value between 15-55 API. The hydrocarbon prospect zone is indicated by the separation of NPHI and RHOB curves with low value, porosity 18.5%, water saturation 37%, and water resistivity shows 0.12-0.13. The reservoir zone is indicated by the cut-off of Lambda-Rho <25 GPa*gr/cc, Mu-Rho <70 GPa*gr/cc, and VpVs ratio <2. Finally, both the petrophysical and sensitivity analysis show indication of fresh water biogenic gas reservoir.

Keywords
petrophysical and sensitivity analysis; reservoir characterization; lithology; carbonate; Nias basin

Topic
Geophysics,Geomatics and Geochemistry

Link: https://ifory.id/abstract/U7TQP3qapHjM

Corresponding Author
Tri Nopi Yanti

Institutions
a) University of Lampung, Lampung
*trinopiyanti30[at]gmail.com
b) Marine Geological Institute, Bandung

Abstract
Comprehensive characterizarion methods are carried out to determine accurate source rock and reservoir identification. Geochemical data has become a critical part of recent unconventional exploration and development. However, due to high cost of geological core extraction and analysis, geophysical wireline logging tools have become the primary source of downhole measurement of geomechanical properties. This study covers an integrated approach at defining geochemical report derived from geological core extraction and analysis and its relationship with geophysical wireline logs of 5 (five) wells at Northeast Java Basin. Wireline logs can be used to identify reservoir and source rock intervals in the primary stage of well drilling. However, the well logs that directly measure the hidrogen content of the kerogen do no exist. Consequently, it used for source rock evaluations and calculation of Total Organic Carbon (TOC) most commonly include sonic, density, gamma ray, neutron, and resistivity. The Van Krevelen diagram has been applied to all 5 (five) wells that indicates 2 (two) of them have potential gas – kerogen type III/IV with marginally mature to mature source rock. The integration of well logs and geochemical data greatly improves the accuracy and understanding of the controls of reservoir quality and source rock. It can be used for further step of knowing basin potential and its prospect level.

Keywords
well log analysis; geochemical data; Total Organic Carbon; Northeast Java Basin

Topic
Geophysics,Geomatics and Geochemistry

Link: https://ifory.id/abstract/7umXR6aPZWK9

Corresponding Author
Esha Firnanza

Institutions
a) Lampung University, Engineering Faculty, Geophysics Engineering Department
Jalan Prof. Dr. Sumantri Brojonegoro No.1 Bandar Lampung 35145
*eshafirnanza[at]gmail.com
b) Indonesian Defense University, Defense Management Faculty, Energy Security Department
IPSC Area, Sentul, Sukahati, Citeureup, Bogor, West Java 16810

Abstract
Preliminary survey using refraction seismic method is an important thing to determine boundaries between weathered layer and rigid layer on highway geotechnical survey. The main thing in refraction seismic survey is to do interpretation survey result to accurate subsurface data. This research conducted subsurface velocity modeling using refraction seismic tomography. The purpose on this research is to make 2D velocity model to determine and analyze boundaries between weathered layer and rigid layer lithology for highway construction corresponding to ASTM D 5777 standard on each line from FRMLN field consist of line E2, E3, E4, and E5. Acquisition data using generalized-reciprocal method with several processing data stages consist of static correction, filtering, gain, first-break picking, inversion and tomography modeling. Based on modeling result, there is two kind of weathered layer lithology and three kind of rigid rocks lithology on research location. Weathered layer lithology consist of top soil in velocity 0-375 m/s and weathered layered (soil) in velocity 750-1125 m/s, while rigid rocks lithology consist of tuff in velocity 1500-1875 m/s, silicic tuff in velocity 2250-4125 m/s, and andesite in velocity more than 5250 m/s. Identified layer which occur a weathering in LINE E2 had a thickness variation around 2-6.3 meter, LINE E3 had a thickness variation around 1-5.6 meter, and LINE E5 had a thickness variation around 1-4 meter from surface.

Keywords
Geotechnical, generalized-reciprocal method, tomography, tuff, weathered layered (soil).

Topic
Geophysics,Geomatics and Geochemistry

Link: https://ifory.id/abstract/RP7g9tHedYDL

Corresponding Author
Rahmat Catur Wibowo

Institutions
Geophysical Engineering Department, Universitas Lampung
Jl. Sumantri Brojonegoro No.1 Kec. Rajabasa Kota Bandar Lampung, Lampung, Indonesia
*catur3712[at]gmail.com

Abstract
The main workable coal measures are concentrated at two horizons within the Miocene Muara Enim Formations (MEF). The main Coal Bed Methane (CBM) targets are the MEF coals, which are known to have good coal thickness and favorable depth for CBM production. Typically, coals are recognized to thin toward the east as they pinch out against the Sunda landmass. Important elements of the CBM play are coal presence and coal lateral distribution. The objective of this study is to identify thin coal reservoir distribution by using well and seismic data integration. Reprocessing seismic data prior to acoustic impedance (AI) inversion produces better results. In situations where wells are located far from seismic lines, calibration with logs is problematic and inversion produces less than maximum results. Multi-attribute approach can optimize the results. Integration of the filtering, AI inversion, and then multi-attribute & neural network methods produce the best output to identify coal seams, their distribution and continuity. The thickest coal identified well data (10 wells) of 6 m in depth 768 m with a total of 5 layers of coal (seam A, B, C, D, and E) in R5 well. Based on seismic modeling, the seams was only seams A with a total volume respectively 518 million m3.

Keywords
thinned coal, cbm, muara enim formation, seismic modelling, geostatistical

Topic
Geophysics,Geomatics and Geochemistry

Link: https://ifory.id/abstract/uGUaKnVZ7AXF

Corresponding Author
Muhammad Faizal Zakaria

Institutions
1. Teknik Geofisika, UPN "Veteran" Yogyakarta
2. Teknik Geofisika, UPN "Veteran" Yogyakarta
3. Teknik Lingkungan, UPN "Veteran" Yogyakarta
4. Fisika, Universitas Islam Negeri Sunan Kalijaga Yogyakarta

Abstract
Tuk sibedug is a spring located in Seyegan sub-district, Sleman Regency. This spring is never dry even in the long dry season. Myth says that the spring is purified because it was discovered by Sunan Kalijaga during the Islamic dispatch in Java. This study aims to determine the subsurface conditions around Tuk Sibedug and determine the configuration of groundwater systems in these areas. The study was conducted by measuring the geoelectric method of Dipole-dipole configuration. Measurements were made on 3 tracks around the spring with a target depth of about 90 m. The tool used is Syscal Jr Switch-48. The software used is Global Mapper13, Surfer10, Res2dinv3, and Arcgis 10.3. The result interpreted as clay stone, sandstone, and breccia. The clay has the smallest resistivity value ie (3.80 - 9,18) Ohm-meter, sandstone (9,18 - 34,40) Ohm-meter, and breccia (34,40 - 83,10) Ohm-meter. Ground water is stored in sandstone. The type of aquifer is a confined aquifer so it has it own natural pressure to push the water to the surface.

Keywords
Tuk Sibedug, Resistivity, aquifer

Topic
Geophysics,Geomatics and Geochemistry

Link: https://ifory.id/abstract/aM3ECWAcFDh9

Corresponding Author
Suharsono Suharsono

Institutions
Universitas Pembangunan Nasional Veteran Yogyakarta

Abstract
Geological complexity part of South-West of Central Java area becomes an attraction for geologists and geophysicist to conduct details research in this area. An integrated approach of gravity and magnetic interpretation was performed to determine the subsurface geological structure patterns, distribution of sedimentary sub-basin, and basement configuration. Objective of this research is to analyze the depth of basement and describe the illustration of sedimentary rock. Interpretation of basement depth was processed from magnetic data whereas geological structure and sedimentary patterns was analyzed using gravity data. Magnetic Anomaly pattern shows that low intensity of magnetic < 60 nT (yellow – green) is disseminated at West-East of the map where as high intensty magnetic about > 200nT (red-purple) indicates basement rock or intrusive rock. Bouguer anomaly indicates that the area is dominated high anomaly 79.4 – 116 mgal (orange to purple) in west, north and southeast area, while low anomaly 49 – 79 mgal ( blue-yellow) in the middle to northwest of area. Interpretation of magnetic data have guided gravity method in reconstuction basin model especially in basement and intrusive rock. Foreward modelling of regional gravity map has pointed seven Formation with different desities, Tapak Formation; Upper Halang; Lower Halang; Pemali Formation; Gabon Formation; Karangsambung Formation and Basement rock

Keywords
Exploration of oil and gas, Gravity Method, Oil and gas basin, Geological structure

Topic
Geophysics,Geomatics and Geochemistry

Link: https://ifory.id/abstract/NQE4YKcvdbFz

Corresponding Author
Tri Nopi Yanti

Institutions
a) University of Lampung, Lampung
*trinopiyanti30[at]gmail.com
b) Marine Geological Institute, Bandung

Abstract
Comprehensive characterizarion methods are carried out to determine accurate source rock and reservoir identification. Geochemical data has become a critical part of recent unconventional exploration and development. However, due to high cost of geological core extraction and analysis, geophysical wireline logging tools have become the primary source of downhole measurement of geomechanical properties. This study covers an integrated approach at defining geochemical report derived from geological core extraction and analysis and its relationship with geophysical wireline logs of 5 (five) wells at Northeast Java Basin. Wireline logs can be used to identify reservoir and source rock intervals in the primary stage of well drilling. However, the well logs that directly measure the hidrogen content of the kerogen do no exist. Consequently, it used for source rock evaluations and calculation of Total Organic Carbon (TOC) most commonly include sonic, density, gamma ray, neutron, and resistivity. The Van Krevelen diagram has been applied to all 5 (five) wells that indicates 2 (two) of them have potential gas – kerogen type III/IV with marginally mature to mature source rock. The integration of well logs and geochemical data greatly improves the accuracy and understanding of the controls of reservoir quality and source rock. It can be used for further step of knowing basin potential and its prospect level.

Keywords
well log analysis; geochemical data; Total Organic Carbon; Northeast Java Basin

Topic
Geophysics,Geomatics and Geochemistry

Link: https://ifory.id/abstract/xvwgmD9VnpNE