Irham Nurwidyanto
Physic Department, Faculty Of Science And Mathematics, Diponegoro University, Semarang

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PEMODELAN TOMOGRAFI CROSS-HOLE METODE GEOLISTRIK RESISTIVITAS (Bentuk Anomali Silindris) Prabowo, Riza Eka; Yulianto, Gatot; Nurwidyanto, M. Irham
BERKALA FISIKA Vol 9, No 1 (2006): Berkala Fisika
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Abstract

            Cross-hole method using an amount of electrode were placed downhole is one of tomography method. Cross-hole tomography method delineate the geological conditions of the earth surface therefore it takes an important rule in the case of anomaly monitoring. The buis concrete planted in subsurface with deepness of about 1 m were used as the source of anomaly. Tomography cross-hole data with configuration such as pole-pole, pole-bipole, bipole-pole and bipole-bipole array were taken with the depth of the borehole is 1,2 m. The space variation of one electrode to another in the hole of drill is 0,2 m, 0,4 m, 0,6 m and 0,8 m for the configuration of pole-bipole, bipole-pole and bipole-bipole. Res2Dinv program obtained the images of bipole-bipole better than the images of other configuration. While the pole-pole configuration had the worst images compared to others. It is caused by two remote electrode of pole-pole array while bipole-bipole array do not have ones. Key words: cross-hole, tomography, borehole, remote electrode
Pengaruh Ukuran Butir Terhadap Porositas dan Permeabilitas pada Batupasir Nurwidyanto, M. Irham; Yustiana, Meida; Widada, Sugeng
BERKALA FISIKA Vol 9, No 4 (2006): Berkala Fisika
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It has been done a research to know the influence of grain size to permeabiality and porosity on sandstones from Ngrayong Formation, Ledok Formation, Kerek Formation and Selorejo Formation. The Permeability is measured by RUSKA Permeameter Gas, while the porosity is measured by  Porosimeter Gas A-9756 series. The grain size is then determined  using grain size analysis method. After the calculation, the grain size is attributed to permeability and porosity of sandstones with the analysis regresi method. Results obtained indicate that the influence of grain size significant at six sandstones. Based on the statistic calculation it has been obtained the relation  with Linear regression  equation Log k= -5.7 Log d + 15 with r2=0.7, for the grain size to permeability and = -1.9x102d +75 with  r2=0.7,  for the relation of grain size to porosity.   Key Word: sandstone, grain size, porosity, permeability
PEMODELAN ZONA SESAR OPAK DI DAERAH PLERET BANTUL YOGYAKARTA DENGAN METODE GRAVITASI Nurwidyanto, M. Irham; Dwi Indriana, Rina; Thaha Darwis, Zukhrufuddin
BERKALA FISIKA Vol 10, No 2 (2007): Berkala Fisika
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A gravity research was done in Pleret, Bantul, Yogyakart.It’s covering 55 measurements points. This research aims to estimated subsurface structure  fault zone of the area, correctly along Opak River’s. Type of Gravitymeter La Coste & Romberg G-1118 using electronics feedback system with accuracy 0.005 miligal was used to measure gravitational field. Interpretation result from kualitative and kuantitative  are  estimated the structure in the research area consist of tree layer that arre  limestone, breccia, and alluvial sediment and Opak sediment’s
STUDY PENDAHULUAN SESAR OPAK DENGAN METODE GRAVITY (STUDY KASUS DAERAH SEKITAR KECAMATAN PLERET BANTUL) Nurwidyanto, M Irham; Brotopuspito, Kirbani Sri; Waluyo, Waluyo; Sismanto, Sismanto
BERKALA FISIKA Vol 14, No 1 (2011): Berkala Fisika
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The reconnaissance research to predict the position and the type of Opak Fault in surrounding subdistrict Pleret area was carryout by gravity method. It done by measured the intensity of gravity field. The measurement was done in five lines  cross the Opak Fault which indicated in the geological map. The intensity of gravity field  in the surround of subdistrict Pleret area are measured by la-coste Romberg  Gravitymeter,  the latitude are measured by GPS Trimble, and the position are measured by GPS Garmin III Plus. The measurement was done in five lines which separated abaut 2,5 km and about 20 km in length. The distance of observations are about 0,5 km to 1 km. The data which be collected are reduction by drift and tidal correction, free air correction, bouger correction and terrain correction. The corrected data are made bouger anomaly contour. The result of this research by kwalitative interpretation are estimated that  the location of Opak Fault in the eastern part of the position of Opak Fault which indicated in the geological map. The type of opak fault are normal fault, because can be detected by gravity method. Key words : Opak Fault, Pleret, gravity method. 
Interpretasi Bawah Permukaan Daerah Manifestasi Panas Bumi Parang Tritis Kabupaten Bantul DIY Dengan Metode Magnetik Indratmoko, Putut; Nurwidyanto, M. Irham; Yulianto, Tony
BERKALA FISIKA Vol 12, No 4 (2009): Berkala Fisika
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Abstract                 Acquisition of geomagnetic field has been done at Kretek, Sanden, Pundong, Bantul and Panggang, Gunung Kidul, Yogjakarta Province on 14 s/d 17 October and  7,8,9,12 November 2009 in orde to interpreted the subsurface structure. Data has been collected by Proton Precession Magnetometer (PPM) to measured  the total  intensity of magnetic field, Global Positioning System (GPS) to determine the position and geology compass to the direction of north pole.                 The raw data has been processed and performed using IGRF (International Geomagnetics Reference Field) correction to obtain total field magnetic anomaly. Upward continuation was performed at 300 meters heigh by Magpick. Qualitative interpretation was done by analyzing regional and local anomaly maps. Quantitative interpretation was done 2 ½ D modelling cross-sectionanomaly maps using Mag2DC for Windows Software.     The result of 2-D modeling produces anomaly objects was susceptibility value (0,0405) in cgs unit  for the first object, susceptibility value (0,0425) in cgs unit  for the second object, susceptibility value (-0,0085) in cgs unit for the third object. The anomaly objects had depth in +580 meters from the surface and was considered the rock which had been experience demagnetitation proses.    Key word: magnetic anomaly, Parangtritis, susceptibilities.
Penentuan Kedalaman dan Ketebalan Akuifer Menggunakan Metode Seismik Bias (Studi Kasus Endapan Alluvial Daerah Sioux Park, Rapid Creek, South Dakota, United State of America) Listiyani, Fenti; Nurwidyanto, M. Irham; Yulianto, Gatot
BERKALA FISIKA Vol 9, No 3 (2006): Berkala Fisika
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Abstract

Data processing of refraction Seismic has been done by using the secondary data in area of Sioux Park, Rapid Creek, South Dakota, United State of America with the trajectory of seismic SP#1 which  has geology structure of alluvial sediment. The sediment Alluvial has a form of water carrier rock precipitated by Rapid Creek Tthe data processing of refraction Seismic usedin this experiment is  Reciprocal Hawkins methode that  represent a method that develop concept of time depth recognition. The time Depth from the refractor is  equal for the travel of critical time from the aspect of between refractor and surface less than time required for the ray path of projection of area refractor at a speed of refractor. Results   of  the seismic refracted obtained: first layer consist of clay  functioning as covering laye, the second layer lapped over from clay, sand, and gravel functioning as carrier coat irrigate or coat acquife and the   third layer lapped over from stone napal, functioning as waterproof coat ( impermeable). Deepness of layer acquifer vary from 0.93 ft - 12.01 ft ( 0.28 m – 3.66 m), and their thickness vary from 0.86 ft – 14.43 ft ( 0.26 m – 4.40 m). The geometry of these  acquiferare in the form of free acquifer  or unconfined aquifer. Keywords: seismic refraction, ground water
Analisis Atribut Seismik untuk Identifikasi Potensi Hidrokarbon Maulana Hadi, Johan; Nurwidyanto, M. Irham; Yulianto, Gatot
BERKALA FISIKA Vol 9, No 4 (2006): Berkala Fisika
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Rms amplitude and spectral decomposition attribute have been extracted for hydrocarbon potential identification in Amandah area, Talangakar Formation, North West Java Basin. Purpose of rms amplitude extractions is to see the change of lithology which is extreme. Example is like reservoir existence. Spectral decomposition has been used to see reservoir at thin thickness. The seismic attributes has been extracted from seismic data 3D Pre Stack Time Migration (PSTM). Log data has been taken from a well (AMD-01) to interpret and determine reservoir thickness in interest zone. Seismic attribute analysis has been used to see existence and shape of channel’s geometry spreading. The result of rms amplitude attribute extraction is reservoir which can be detected clearly at 10 ms, 20 ms, 30 ms and 40 ms window analysis. Whereas the result of spectral decomposition attribute extraction is reservoir which can be detected at 15 Hz – 25 Hz frequency with 30 ms and 40 ms window analysis. The result of rms amplitude and spectral decomposition attribute analysis shows hydrocarbon in Amandah area, Talangakar Formation is potential in channel depositional facies with depositional direction at north-south (N-S) and north nort east – south south west (NNE-SSW) and  thickness high of channel is concern at 36-60 m.   Key words: Seismic attribute, rms amplitude, spectral decomposition, reservoir,
INVERSI LINIER LEASTSQUARE DENGAN MATLAB ( Studi Kasus Model Gravitasi Bola Berlapis) Nurwidyanto, Irham; Setiawan, Ari
BERKALA FISIKA Vol 14, No 3 (2011): Berkala Fisika
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The linear  least square Inversion have been made with matlab8 for a case study of layered ball with the aim to study the response of the gravitational field of a layered ball.The gravitational field of layered ball formulation described later the value  is calculated by programming in matlab. As the validation data is computed on the surface of the earth'sgravitational field with a case of six layers with different density and radius. The value aresuitable  to the real slate. After the results are appropriate, the results of  programming was made is used to calculate the gravitation field  of another layered ball object, the data is then used assynthetic data (considered as a data field) which is an inversion of input data on the program aremade.The results obtained in this modeling can be concluded that there are ambiguity from theinversion results, which means that the parameters which be obtained from the invertion methodare  very different to the riil parameter if not given early predictive value as the limit of theexpected value. By providing a limit value (the value of the initial estimate) the expected results ofthe inverse can provide results that correspond (nearly) true value.Key words: Inversion, Linier leastquare, layered ball
Estimasi Penyebaran Sedimen Cekungan Jawa Timur Dengan Metode Gravity Adib Hasan, Muhamad; Nurwidyanto, M. Irham
BERKALA FISIKA Vol 11, No 4 (2008): Berkala Fisika
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This research is a reconnaissance study to predict the distribution and depth of the sediment basin in East Java based on Bouger Anomaly data in gravity method.Bouger anomaly is projected to flat plane used by equivalent point mass source method. Upward continuation is used to separate the regional and residual anomaly.  Modeling sub surface in two dimensions are used by polygon Talwani method by help computer program Geomodel.The results of this research can be concluded that in East Java sediment basin has about 6 km in depth. The central basin are reside in mid of East Java, there are around Sragen, Karanganyar, Ngawi, Madiun, Nganjuk, Kediri, Bojonegoro, Jombang and Mojokerto which in the east west direction. In the eastern part of East Java Basin there are Sidoarjo, Pasuruhan, Probolinggo and Maura bay has direction in northwest to southeast. Key words: Basin, basement, sediment, Bouger Anomaly
PEMODELAN ANOMALI GRAVITASI SESAR DENGAN PENDEKATAN MODEL SHEET (MODELLING GRAVITY ANOMALIES OF FAULT BY SHEET MODEL APPROACH) Nurwidyanto, M Irham; Setiawan, Ari
BERKALA FISIKA Vol 14, No 4 (2011): Berkala Fisika
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AbstractThe modelling gravity anomaly of fault model with a model sheet approach with the aim to study the response of gravity anomalies of faults was done.Modelling is done by modelling approaches bedding with a thickness t and density contrastwith surrounding Δρ. The  gravity anomaly at a point are formulated and  the calculation andvisualization program created in matlab8RS. From the modelling is made it can be concluded that the fault position is generally locatedbetween the gravity anomaly minimum and maximum gravity anomaly. When thetypes of fault arevertical normal fault then the fault position precisely located on the horizontal gradient  maximumvalue, whereas when the fault are not vertical, the location of fault are  to be near (around) themaximum horizontal gradient.Key words: modelling, gravity anomalies, faults, model sheets.