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Designing a Genetic Algorithm for Efficient Calculation in Time-Lapse Gravity Inversion Wahyudi, Eko Januari; Santoso, Djoko; Kadir, Wawan Gunawan Abdul; Alawiyah, Susanti
Journal of Engineering and Technological Sciences Vol 46, No 1 (2014)
Publisher : ITB Journal Publisher, LPPM ITB

As an advanced application of soft computation in the oil and gas industry, genetic algorithms (GA) can contribute to geophysical inversion problems in order to achieve better results and efficiency in the computational process. Time-lapse gravity responses to pore-fluid density changes can be modeled to provide the density distribution in the subsurface. This paper discusses the progress of work in inverse modeling of time-lapse gravity data using value encoding with alphabet formulation. The alphabet formulation was designed to provide the solution for positive and negative density change with respect to a reference value (0 gr/cc). The inversion was computed using a genetic algorithm as the optimization method. Working with genetic algorithms, time-intensive computational processes are a challenge, so the algorithm was designed in steps through the evaluation of a GA operator performance test. The performances of several combinations of GA operators (selection, crossover, mutation, and replacement) were tested with a synthetic model of a single-layer reservoir. Sharp boundaries of density changes in the reservoir layer were derived from interpretation of the averaged calculation of several model samples. Analysis showed that the combination of stochastic universal sampleâmultipoint crossoverâquenched simulated annealing per generationâno duplicity achieved the most promising results.

ANNOTATION OF USING BOREHOLE TIME-LAPSE GRAVITY BY GENETIC ALGORITHM INVERSION FOR SUBSURFACE MODELING Gunawan, Indra; Wahyudi, Eko Januari; Alawiyah, Susanti; Kadir, Wawan Gunawan Abdul; Fauzi, Umar
Journal of Engineering and Technological Sciences Vol 52, No 2 (2020)
Publisher : Institute for Research and Community Services, Institut Teknologi Bandung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.eng.technol.sci.2020.52.2.2

We present the annotation to a genetic algorithm (GA) method for an inverse synthetic subsurface density model using surface and borehole time-lapse gravity data. The objective of the inversion is to find the boundaries of the object area and background, where one bit of the chromosome represents the densities. The model that was used in this paper was a simple homogeneous body anomaly and a simplified real water mass injection model in order to argue that the code is suitable for field modeling. We show the influences of the existence of borehole gravity data and location towards the inversion, where the result indicates that an additional good borehole location could increase the success rate up to 13.33% compared to without gravity borehole data for the simple model and up to 4.39% for the field model. The inversion produced the best results when the borehole positions were placed in a state of symmetry towards the body object?s mass.

Designing a Genetic Algorithm for Efficient Calculation in Time-Lapse Gravity Inversion Eko Januari Wahyudi; Djoko Santoso; Wawan Gunawan Abdul Kadir; Susanti Alawiyah
Journal of Engineering and Technological Sciences Vol. 46 No. 1 (2014)
Publisher : Institute for Research and Community Services, Institut Teknologi Bandung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.eng.technol.sci.2014.46.1.4

As an advanced application of soft computation in the oil and gas industry, genetic algorithms (GA) can contribute to geophysical inversion problems in order to achieve better results and efficiency in the computational process. Time-lapse gravity responses to pore-fluid density changes can be modeled to provide the density distribution in the subsurface. This paper discusses the progress of work in inverse modeling of time-lapse gravity data using value encoding with alphabet formulation. The alphabet formulation was designed to provide the solution for positive and negative density change with respect to a reference value (0 gr/cc). The inversion was computed using a genetic algorithm as the optimization method. Working with genetic algorithms, time-intensive computational processes are a challenge, so the algorithm was designed in steps through the evaluation of a GA operator performance test. The performances of several combinations of GA operators (selection, crossover, mutation, and replacement) were tested with a synthetic model of a single-layer reservoir. Sharp boundaries of density changes in the reservoir layer were derived from interpretation of the averaged calculation of several model samples. Analysis showed that the combination of stochastic universal sample"“multipoint crossover"“quenched simulated annealing per generation"“no duplicity achieved the most promising results.

Annotation of Using Borehole Time-Lapse Gravity by Genetic Algorithm Inversion for Subsurface Modeling Indra Gunawan; Eko Januari Wahyudi; Susanti Alawiyah; Wawan Gunawan Abdul Kadir; Umar Fauzi
Journal of Engineering and Technological Sciences Vol. 52 No. 2 (2020)
Publisher : Institute for Research and Community Services, Institut Teknologi Bandung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.eng.technol.sci.2020.52.2.2

We present the annotation to a genetic algorithm (GA) method for an inverse synthetic subsurface density model using surface and borehole time-lapse gravity data. The objective of the inversion is to find the boundaries of the object area and background, where one bit of the chromosome represents the densities. The model that was used in this paper was a simple homogeneous body anomaly and a simplified real water mass injection model in order to argue that the code is suitable for field modeling. We show the influences of the existence of borehole gravity data and location towards the inversion, where the result indicates that an additional good borehole location could increase the success rate up to 13.33% compared to without gravity borehole data for the simple model and up to 4.39% for the field model. The inversion produced the best results when the borehole positions were placed in a state of symmetry towards the body object's mass.

Simulasi Numerik untuk Menentukan Gaya Gravitasi Bawah Permukaan Pada Model Prisma Segiempat Indra Gunawan; Susanti Alawiyah
Indonesia Journal on Computing (Indo-JC) Vol. 1 No. 2 (2016): September, 2016
Publisher : School of Computing, Telkom University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.21108/INDOJC.2016.1.2.88

Resolusi model bawah permukaan menggunakan data gaya berat dengan pendekatan prisma segi-empat ditentukan oleh ukuran dari prisma tersebut. Semakin kecil ukuran prisma, maka semakin tinggi resolusi yang dihasilkan. Sayangnya, ukuran dari prisma berkorelasi langsung dengan jumlah prisma pada volume model. Jumlah dari prisma juga akan berhubungan dengan harga komputasi yang harus dibayar untuk menghitung area yang sedang dikaji. Untuk mengatasi hal ini, dalam penelitian ini digunakan beberapa metode perhitungan pemodelan kedepan melalui pendekatan prisma segi-empat sebagai akibat dari model objek massa jenis yang homogen. Selanjutnya dilakukan analisa terhadap efisiensi, akurasi dan kemampuan dari setiap metode menggunakan bahasa pemrograman C++ dengan presisi ganda. Sebagai contoh objek dan titik observasi, digunakan standard cubic model untuk membandingkannya dengan hasil perhitungan. Berdasarkan hasil perhitungan, terdapat beberapa titik observasi yang tidak bisa dihitung karena adanya sifat singularity. Paper ini memberikan informasi benchmark dan review metode berdasarkan pada pengujian yang dilakukan.

Analysis Of The Geothermal Potential Based Fault Zone In Burni Telong Bener Meriah, Aceh, Indonesia Gartika Setiya Nugraha; Marwan Marwan; Oky Ikhramullah; Susanti Alawiyah; Sutopo Sutopo
UNEJ e-Proceeding 2016: Proceeding The 1st International Basic Science Conference
Publisher : UPT Penerbitan Universitas Jember

Show Abstract | Download Original | Original Source | Check in Google Scholar

Mount of Burni Telong located in Bener Meriah, Aceh, Indonesia is one of the mountains that have the potential for development of renewable energy from geothermal sources, but is still untapped. The evidence suggests that, to date Aceh still depends on power supplies from North Sumatra. This dependence often affects alternate electricity blackouts all over the province so that the necessary rationale for their source of power generation in Aceh. The purpose of this study was to analyze the potential development of Burni Telong as geothermal energy power plant in Aceh, Indonesia.This study was a survey with the approach in the field of geophysics. Analysis of potential geothermal done using the gravity method to investigate the distribution of mass in the subsurface. The study found that there are two tracks, namely: A-A' and B-B track'. A-A' tracks has four layers, composed of: Riolitic Tuff (1.77g/cm3), basaltic Tuff (2:12 gr/cm3), Diorites (2.78 gr/cm3),and basalt (3:00 gr/cm3). B-B' tracks has three layers, namely: Basaltic Tuff (2.12 gr/cm3); Diorites (2,78 gr/cm3), and basalt (3.00 gr/cm3). In both of these trajectories found two faults, namely: normal and Horst. It can be concluded that the difference in density contrast and hot springs that are parallel to the fault indicates a fault in Burni-Telong, so Burni Telong has the potential Geothermal and very likely to be developed as a source of electricity generation from geothermal energy in Aceh, Indonesia.

PEMODELAN TIME-LAPSE MICROGRAVITY UNTUK ESTIMASI PERUBAHAN MUKA AIRTANAH DI BANDUNG, JAWA BARAT Eko Januari Wahyudi; Wawan Gunawan A. Kadir; Susanti Alawiyah; Setianingsih Setianingsih; Indra Gunawan; Dadi Abdurrahman
JURNAL SUMBER DAYA AIR Vol 19, No 2 (2023)
Publisher : Bina Teknik Sumber Daya Air, Kementerian Pekerjaan Umum dan Perumahan Rakyat

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.32679/jsda.v19i2.858

ABSTRACT Studies related to groundwater monitoring using geophysical methods have been carried out since the 1990s. Surface gavity data with a scheme of relative gravimeter measurements is chosen for monitoring in urban areas because it is quite fast, easy, affordable, and relatively low-impact on the environment. The significance of the time-lapse microgravity method for the target of this study depends on changes in the mass of water in the aquifer layer below the surface. The research area in this study covers the city of Bandung and several surrounding areas with an interpolated grid coverage of (18 x 17) km2. Gravity changes were determined by six repeated surveys at the same observation points from 2010 to 2021. The aim of this research is to develop a method for estimating groundwater table changes based on time-lapse microgravity data modeling. The complexity of subsurface density changes is simplified for two parts related to near surface density changes and density changes in the intermediate aquifer layer. The trend of groundwater table data in 2010 is used as a reference to determine estimates for 2015, 2016 (February and August), 2019, and 2021. Modeling results for intermediate aquifers (confined groundwater system) provide changes in groundwater levels from 2010 with estimates reached ±23 meters, while the results of modeling at near surface (shallow groundwater level) indicate a groundwater level change of approximately ±8 meters from the year 2010.Keywords: microgravity, groundwater, modeling, hydrology, aquifer. ABSTRAKStudi terkait pemantauan airtanah dengan metode geofisika telah dilakukan sejak tahun 1990-an. Data gravity di permukaan dengan skema pengukuran gravimeter relatif dipilih pada pemantauan di area perkotaan karena cukup cepat, mudah, murah, dan relatif tidak merusak lingkungan. Signifikansi metode time-lapse microgravity pada target studi ini bergantung pada perubahan massa air pada lapisan akuifer di bawah permukaan. Area penelitian pada studi ini mencakup Kota Bandung dan beberapa area di sekitarnya dengan cakupan luasan interpolasi grid (18 x 17) km2. Perubahan gravitasi ditentukan oleh enam kali survei berulang pada beberapa titik pengamatan yang sama sejak 2010 sampai 2021. Tujuan dari penelitian ini adalah mengembangkan metode untuk mengestimasi perubahan muka airtanah berdasarkan pemodelan data time-lapse microgravity. Kompleksitas perubahan densitas di bawah permukaan disederhanakan untuk dua bagian terkait perubahan densitas dekat permukaan dan perubahan densitas pada lapisan akuifer menengah. Kecenderungan dari data muka airtanah pada tahun 2010 digunakan sebagai acuan untuk menentukan estimasi pada tahun 2015, 2016 (Februari dan Agustus), 2019, dan 2021. Hasil pemodelan pada akuifer menengah (sistem airtanah tertekan) memberikan perubahan muka airtanah dari tahun 2010 dengan estimasi mencapai ±23 meter, sedangkan hasil pemodelan pada kedalaman yang lebih dangkal (muka airtanah dangkal) menunjukkan perubahan muka airtanah mencapai ±8 meter dari tahun 2010.Kata Kunci: microgravity, airtanah, pemodelan, hidrologi, akuifer

Study of Calculation of Terrain Correction Using square pattern and sloped triangle Method in Karangsambung Area Salam, Rafi; Wahyudi, Eko Januari; Alawiyah, Susanti
Jurnal Geofisika Vol 17 No 2 (2019): Jurnal Geofisika
Publisher : Himpunan Ahli Geofisika Indonesia (HAGI)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.36435/jgf.v17i2.412

Conventional assessments of terrain correction are carried out by laying out transparent paper containing the Hammer chart on topographic maps, then estimating the elevation for each compartment. But this procedure has disadvantages, the number of compartments are too small for area with many topographic variations, and there is a subjectivity from the observer in estimating the compartments height. This research aim to overcome these problems and get more accurate terrain correction value. In this research, estimation of terrain correction carried out using square pattern and sloped triangle method. This method divides the area around the measurement point into a zone containing a square-shaped and triangle compartment. The research start with testing the program by using synthetic data to see the effect of rock bodies on terrain correction value. Then the program was applied to Karangsambung to see the topographic influence around Karangsambung on terrain correction. The program is then applied to gravity data, and the results are compared with calculations using the Hammer chart. Based on the synthetic data test, it was found that the value of terrain correction from a rock body measuring 10 x 10 km with a height difference of 1000 m from the station no longer significantly affects at the distance of 20 km. The topography around Karangsambung in the form of South Seraju Ranges with altitude of 1000 m at distance of 20 30 km gives effect of 0.05 mGal on terrain correction, while the Quaternary Volcano with an altitude of 3000 m at distance of 30 40 km gives effect of 0.1 mGal. The results of applying program at the gravity data show that the use of the square pattern method is able to correct errors from Hammer chart up to 3 mGal. The difference between the calculation of the two methods is getting bigger in the station located at slope area. It happens because estimation of the height difference in slope area is more difficult to do.

Inversi Gaya Berat Model Talwani Menggunakan Flower Pollination Algorithm Latupeirissa, Pricilia O. M; Bahri, Samsul; Alawiyah, Susanti
Tanah Goyang : Jurnal Geosains Vol 2 No 1 (2024): Tanah Goyang : Jurnal Geosains
Publisher : Program Studi Teknik Geofisika, Universitas Pattimura

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.30598/tanahgoyang.2.1.13-21

Tantangan utama dalam semua metode geofisika, termasuk pemodelan gayaberat adalah rekonstruksi distribusi parameter fisik bawah permukaan berdasarkan data yang diamati dan diambil di permukaan. Inversi gravitasi ditujukan untuk memperoleh informasi untuk membuat model distribusi densitas dibawah permukaan menggunakan percepatan gravitasi terukur yang dikenal sebagai anomali gravitasi. Pemodelan inversi adalah salah satu teknik pemodelan di mana parameter modelnya diperoleh langsung dari data pengamatan, Tujuan dari penelitian ini adalah melakukan pemograman pemodelan kedepan model Talwani serta pemodelan kebelakang dengan metode flower pollination algorithm. FPA merupakan bagian dari contoh inversi non-deterministik dan sering disebut juga sebagai algoritma penyerbukan bunga serta dikembangkan oleh Xin-She Yang pada tahun 2012. Sesuai dengan namanya, algoritma ini merupakan suatu algoritma yang terinspirasi dari proses penyerbukan bunga. Pemodelan dalam penelitian ini menggunakan tiga model sederhana yang menggambarkan suatu kondisi di bawah permukaan. Model pertama yang digunakan yaitu model dengan intrusi, model kedua yaitu model dengan patahan serta model yang terakhir yaitu model dengan adanya cekungan.

Inversi Gaya Berat Model Talwani Menggunakan Flower Pollination Algorithm Latupeirissa, Pricilia O. M; Bahri, Samsul; Alawiyah, Susanti
Tanah Goyang : Jurnal Geosains Vol 2 No 1 (2024): Tanah Goyang : Jurnal Geosains
Publisher : Program Studi Teknik Geofisika, Universitas Pattimura

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.30598/tanahgoyang.2.1.13-21

Tantangan utama dalam semua metode geofisika, termasuk pemodelan gayaberat adalah rekonstruksi distribusi parameter fisik bawah permukaan berdasarkan data yang diamati dan diambil di permukaan. Inversi gravitasi ditujukan untuk memperoleh informasi untuk membuat model distribusi densitas dibawah permukaan menggunakan percepatan gravitasi terukur yang dikenal sebagai anomali gravitasi. Pemodelan inversi adalah salah satu teknik pemodelan di mana parameter modelnya diperoleh langsung dari data pengamatan, Tujuan dari penelitian ini adalah melakukan pemograman pemodelan kedepan model Talwani serta pemodelan kebelakang dengan metode flower pollination algorithm. FPA merupakan bagian dari contoh inversi non-deterministik dan sering disebut juga sebagai algoritma penyerbukan bunga serta dikembangkan oleh Xin-She Yang pada tahun 2012. Sesuai dengan namanya, algoritma ini merupakan suatu algoritma yang terinspirasi dari proses penyerbukan bunga. Pemodelan dalam penelitian ini menggunakan tiga model sederhana yang menggambarkan suatu kondisi di bawah permukaan. Model pertama yang digunakan yaitu model dengan intrusi, model kedua yaitu model dengan patahan serta model yang terakhir yaitu model dengan adanya cekungan.

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