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"ABSTRAKLapangan X Jawa Barat merupakan daerah yang akan dikembangkan berdasarkandata-data survei seismik 2D dan data sumur eksplorasi yang telah dilakukan.Tujuannya adalah untuk pengembangan lapangan, pematangan lead menjadiprospek dan sebagai data yang akan digunakan untuk Enhanced Oil Recovery.Dengan data-data yang sudah ada sebelumnya, maka diputuskan untuk tidakmelakukan survei seismik 2D lagi tetapi melakukan survei seismik 3D dengandesain parameter yang berbeda. Hal ini disebabkan karena pengembanganlapangan X meliputi daerah yang luas, sehingga pemilihan desain parametersurvei seismik 3D yang berbeda tersebut bertujuan untuk menekan biaya surveiseismik dan tetap mendapatkan hasil data seismik yang baik dan dapatdipergunakan untuk mempercepat pengembangan lapangan.Teknologi survei seismik 3D umumnya memerlukan biaya yang lebih mahaldibandingkan dengan survei seismik 2D. Hal ini disebabkan jumlah peralatan dantenaga kerja yang digunakan lebih banyak. Dengan berkembangnya teknologisurvei seismik 3D terutama desain parameter, peralatan instrument perekamandata dan peralatan pengolahan data, maka biaya dan operasi survei seismik dapatlebih efektif dan efisien tanpa mengurangi tujuan daripada survei seismik itusendiri.Dari hasil kajian, penggunaan desain parameter seismik 3D yang berbeda padalapangan X, tidak berpengaruh besar pada kualitas data seismik yang diperoleh.Survei seismik 3D tersebut tetap dapat menghasilkan data dengan kualitas yangbagus dan target yang diharapkan dapat terlihat dengan baik. Sehingga surveiseismik 3D ini mempunyai keuntungan yaitu tetap mendapatkan data seismik 3Dsesuai yang diharapkan dengan biaya yang dapat ditekan mencapai 33% dariperhitungan awal.

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AbstractThe X field on West Java province, will be developed based on 2D seismic surveydata and exploration wells. The goal is to develop field, establish leads intoprospects and Enhanced Oil Recovery.Referring to the availability data, it is decided to carried out 3D seismic ratherthan 2D seismic. This is caused by the development of the X field covers a largearea, so the selection of different parameters design of 3D seismic survey aims toreduce the cost of seismic surveys and still get good results and seismic data canbe used to accelerate the development of the field.3D seismic survey technologies generally require a higher cost compared with 2Dseismic survey. This is due to the amount of equipment and labor. With thedevelopment of technology, especially parameters design of 3D seismic survey,recording instrument equipment and data processing equipment, the cost andseismic survey operations can be more effective and efficient withoutcompromising the objectives of the seismic survey itself.The results of the study, the used of different parameters design on 3D seismicsurvey of the X field, no significant effect on the quality of seismic data acquired.3D seismic survey is still to produce data with good quality and the expectedtarget can be seen properly. So the 3D seismic survey has the advantage that itstill get the 3D seismic data fit the expected cost can be reduced to 33% of theinitial calculations."

"Tatanan tektonik kompleks di wilayah Papua Barat menyebabkan tingginya tingkat seismisitas sehingga berpotensi mengalami kerusakan yang besar saat mendapatkan getaran yang kuat ataupun gempa bumi. Peranan kajian karakteristik lapisan bawah permukaan seperti metode mikrotremor berdasarkan sifat gerakan tanah sangat penting sebagai langkah mitigasi bencana ataupun dalam perencanaan pembangunan infrastruktur. Pada penelitian ini, dua parameter penting pada data mikrotremor yaitu frekuensi dominan dan amplifikasi tanah yang berguna dalam mengestimasi karakteristik tanah, digunakan untuk menganalisis dan memetakan distribusi zona indeks kerentanan seismik, percepatan tanah maksimum (PGA), 𝑉𝑠30 dan Ground Shear Strain pada lapisan sedimen di wilayah area penelitian “SA”, Papua Barat. Hasil penelitian menunjukkan bahwa area penelitian didominasi oleh lapisan sedimen aluvial yang tebal dengan karakteristik tanah lunak hingga tanah sedang. Nilai indeks kerentanan seismik relatif rendah pada area ini bernilai antara 0,8 – 14,1 dimana tergolong dalam area yang tidak terlalu rentan terhadap aktivitas seismik atau potensi kerusakan kecil. Selain itu, nilai percepatan tanah maksimum area penelitian bernilai 149 – 771 gal yang tergolong dalam kategori intensitas gempa bumi III sampai V, yaitu kerusakan ringan hingga berat dengan sifat dinamis tanah elasto-plastis yang dapat mengakibatkan fenomena crack atau retakan pada lapisan tanah.

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The complex tectonic in the West Papua region causes high levels of seismicity so that it has potential to sustained major damage during strong vibrations or earthquakes. The role of the study of the characteristics of the subsurface layer such as the microtremor method based on the nature of the ground motion is very important as a disaster mitigation step or in infrastructure development planning. In this study, two important parameters in the microtremor data, namely the dominant frequency and soil amplification which are useful in estimating soil characteristics, are used to analyze and mapping the distribution of seismic susceptibility index zones (𝐾𝑔), maximum soil acceleration (PGA), 𝑉𝑠30 and Ground Shear Strain in sediments layer in the “SA” study area, West Papua. The results showed that the research area was dominated by a thick layer of alluvial sediment with soft to medium soil characteristics. The value of the seismic vulnerability index is relatively low in this area, which is between 0.8 - 14.1 which is classified as an area that is not too vulnerable to seismic activity or small damage potential. In addition, the maximum ground acceleration value of the study area is 149 – 771 gal which belongs to the category of earthquake intensity III to V, i.e. mild to severe damage with elasto-plastic soil dynamic properties which can cause crack in the soil layer.

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"Lapangan Geotermal Hululais terletak di Propinsi Bengkulu, yang dalam tatanan tektonik berada di tepi cekungan struktur pull-apart dalam zona Sistim Sesar Sumatera. Sebanyak 24 sumur telah dibor sejak tahun 2007 sampai 2018. Distribusi permeabilitas sumur-sumur ini menunjukkan karakteristik yang bervariasi. Untuk mengidentifikasi distribusi permeabilitas dan karakteristik reservoir bawah permukaan lapangan yang tergambar dalam suatu model kecepatan gelombang shear 3D sebagai hasil pengukuran kecepatan gelombang Rayleigh, maka dilakukan penelitian menggunakan metode Ambient Noise Tomography (ANT) dalam skala lokal. Akuisisi data gelombang permukaan di lapangan ini menggunakan 20 seismometer yang dipasang di 156 titik pengamatan dengan spasi 500 - 1000 meter. Pemrosesan data diawali dengan ekstraksi gelombang permukaan hasil korelasi silang dari dua titik amat menggunakan Fungsi Green dan ekstraksi grup kecepatan dari kurva dispersi untuk pemodelan ke depan (forward model) dilakukan inversi dengan metode Fast Marching Method (FMM). Selanjutnya untuk mendapatkan resolusi pencitraan tomografi yang lebih tinggi dilakukan checker board test sebelum dilakukan inversi model dengan teknik inversi subspace. Grup kecepatan gelombang Rayleigh dalam domain periode, kemudian dilakukan konversi ke domain kedalaman dengan menggunakan metode Neighborhood Algorithm (NA) untuk mendapatkan profil kecepatan gelombang Shear 1 D. Profil kecepatan 1 D ini yang digunakan dalam pencitraan gelombang Shear dalam 3D. Hasil pencitraan tomografi gelombang Shear menggambarkan adanya distribusi anomali kecepatan (Vs) rendah yang berasosiasi dengan zona permeabel di zona patahan dan hal ini ditunjukkan adanya kondisi hilang sirkulasi pada saat pemboran sumur. Sedangkan distribusi anomali Vs tinggi yang bersasosisi dengan batuan kompak dijumpai di sumur yang tidak terjadi hilang sirkulasi pada saat pemboran. Sebaran anomali Vs rendah juga dijumpai pada kedalaman dangkal, sesuai dengan penyebaran anomali resistivitas rendah dari MT (<20 ohm-m), yang berasosiasi dengan lapisan batuan penutup (cap rock). Sedangkan penyebaran anomali Vs tinggi yang berasosiasi dengan granodiorit sebagai batuan dasar teramati di beberapa sumur pemboran. Distribusi kecepatan gelombang Shear rendah yang berasosiasi dengan zona permeabel dipakai sebagai dasar dalam penentuan target pemboran.

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Hululais Geothermal Field is located in Bengkulu Province which is tectonically located on the edge of a pull-apart structure basin in the Sumatra Fault System zone. A total of 24 wells have been drilled since 2007 to 2018. The permeability distribution of these wells shows varying characteristics. To determine the permeability distribution and characteristics of the subsurface reservoir in the field described in the 3D shear wave velocity model from Rayleigh wave velocity measurements, a study was conducted using the Ambient Noise Tomography (ANT) method on a local scale. Surface wave data acquisition in this field used 20 seismometers installed at 156 observation points with a spacing of 500 – 1000 meters. Data processing begins with surface wave extraction from the cross-correlation results of two very different points using the Green's Function and velocity group extraction from the dispersion curve for forward model inversion using the Fast Marching Method (FMM). Furthermore, to obtain a higher tomography imaging resolution, a checker board was performed before the model inversion was carried out using the subspace inversion technique. The Rayleigh wave velocity group in the period domain is then converted to the depth domain using the Neighborhood Algorithm (NA) method to obtain a 1 D shear wave velocity profile. This 1 D velocity profile is used in 3D shear wave imaging. The results of shear wave tomography imaging illustrate the presence of low velocity (Vs) distribution anomalies associated with permeable zones in the fault zone and this indicates the presence of lost circulation conditions during well drilling. While the high Vs anomaly distribution associated with compact rocks was found in wells that did not indicate loss of circulation during drilling. The low Vs anomaly distribution was also found at shallow depths, in accordance with the low resistivity anomaly distribution of MT (<20 ohm-m) associated with the cap rock. While the high Vs anomaly distribution associated with granodiorite as the bedrock was observed in several drilling wells. The low shear wave velocity distribution associated with permeable zones is used as a basis for determining drilling targets."

"Variansi adalah salah satu teknik dalam metoda statistik yang digunakan untuk mencari dan menemukan suatu ukuran yang memberikan gambaran umum tentang bagaimana nilai-nilai pada suatu perangkat data itu beragam (bervariansi). Dalam data seismik 3D variansi dapat digunakan untuk mengukur keragaman amplitudo secara lateral, perubahan amplitudo ini secara implisit dapat disebabkan oleh karena adanya patahan, rekahan, chanel ataupun perubahan 1ithologi. Informasi ini sangat diperlukan oleh para geofisikawan, geologiwan maupun para ahli reservoir dalam meningkatkan presisi pemodelan reservoir dan menurunkan resiko kegagalan dalam pemboran. Pada tesis ini telah dilakukan pengujian penerapan teknik variansi dalam suatu volume data seismik 3D dengan berbagai macam konfigurasi trace kearah lateral, dan faktor pembobotan yang di gunakan untuk mengantenuasi noise sekaligus menormalisasikan harga varian dari setiap sampel yang dioperasikan secara vertikal. Dan data citra time slice yang dihasilkan terdapat perbedaan yang cukup signifikan antara data volume seismik 3D sebelum dan sesudah dilakukannya proses variansi. Pola struktur geologi, seperti patahan, rekahan dan chanel yang semula terpendam dalam data, setelah ditransformasikan kedalam domain variansi kini dapat terdefinisikan dengan jelas.

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Variance is once of several kind statistical methods which is usually used to looking about the variant of our data set. I n 3D seismic data, variance can be used for measuring the variance of seismic amplitude laterally. Implicitly, seismic amplitude changes can be happened due to faults, disjoints, chanels or lithology changes. This information is very important specially for geophysicist, geologist or reservoir engineer to improve their reservoir modelling and to decrease the risk of drilling failed. In this thesis we have been tested the aplication of variance method into a 3D seismic data volume by several kind of seismic trace configuration, and also weightening factor to antenuate the noise and to normalize the variance value for each sample which was operated vertically. Based on the time slice image that had been produced, there were significant diferences between 3D seismic data volume before and after applied variance process. The geological structure such us faults, disjoints and chanel which could not be seen on the conventional time slice after be transfered into variance domain their geological features can be defined with more clearly."

"[ABSTRAKLapangan Athar mulai berproduksi sejak tahun 1975 dengan produksi kumulatif mencapai 900 MMbbls dan RF 50%. Pada tahun 2011 dilakukan akuisisi seismik 3D untuk melihat remaining potential yang ada di lapangan ini. Analisa seismik 3D dengan atribut seismik dan inversi simultan memberikan hasil yang cukup baik untuk menentukan penyebaran batupasir dan hidrokarbon yang ada di dalam nya. Volume densitas hasil inversi, atribut minimum amplitude, dan atribut arc length membantu dalam mengidentifikasi penyebaran reservoar. Lambda-Rho dan AI membantu dalam mengidentifikasi area-area yang mengandung hidrokarbon. Interpretasi struktur di seismik menunjukkan adanya sesar minor, yang sebelumnya tidak teridentifikasi pada seismik 2D. Hasil analisa seismik digunakan dalam pembuatan 3D geomodel. Penentuan batas channel, dan area hidrokarbon di dipandu hasil dari analisa seismik dan data sumur. Empat tubuh channel teridentifikasi dari analisis tersebut, sementara overbank deposit disebarkan secara statistik. Data interpreasi struktur digunakan untuk menentukan jumlah segmen atau kompartemen, dan hasilnya adalah lima segmen selatan dan satu segmen utara terdapat di zona dangkal Lapangan Athar. Hasil pemodelan geologi menunjukkan bahwa segmen 5 menjadi area yang masih memiliki prosepek untuk produksi minyak, sementara segmen 2 memiliki prospek untuk produksi gas.

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ABSTRACTAthar Field start producing since 1975 up to now with cummulative production reached 900 MMbbls and RF 50%. 3D seismic was acquired in 2011 to identify the remaining potential in this field. Analysis of 3D seismic with attribute and simultaneous inversion provide a good result to determine reservoar distribution and hydrocarbon contained. Density cube from inversion, minimum amplutide attribute, anda arc length attribute are used to map the sand distribution. Lambda Rho and AI (Ip) are usefull to identify the remaining hyrocarbon area. Structural interpretation from seismic shows there are minor faults which is not identified before with 2D seismic. The result of the analysis was used to create 3D Geomodel. The channel limit determination, and remaining hydrocarbon area guided by analysis from seismic and well data. As a result, four channel bodies were identified, whilst overbank deposit distributed statistically. Structural interpretation data used to determine the number of segment or compartment, and the result are five segments in the south and one segment in the north identified in the shallow zone Athar Field. The result of geological modeling shows that segment 5 still has prospect in oil production, whilst segment 2 has prospect in gas production.;Athar Field start producing since 1975 up to now with cummulativeproduction reached 900 MMbbls and RF 50%. 3D seismic was acquired in 2011 toidentify the remaining potential in this field.Analysis of 3D seismic with attribute and simultaneous inversion provide agood result to determine reservoar distribution and hydrocarbon contained. Densitycube from inversion, minimum amplutide attribute, anda arc length attribute are usedto map the sand distribution. Lambda Rho and AI (Ip) are usefull to identify theremaining hyrocarbon area. Structural interpretation from seismic shows there areminor faults which is not identified before with 2D seismic.The result of the analysis was used to create 3D Geomodel. The channel limitdetermination, and remaining hydrocarbon area guided by analysis from seismic andwell data. As a result, four channel bodies were identified, whilst overbank depositdistributed statistically. Structural interpretation data used to determine the number ofsegment or compartment, and the result are five segments in the south and onesegment in the north identified in the shallow zone Athar Field.The result of geological modeling shows that segment 5 still has prospect inoil production, whilst segment 2 has prospec in gas production, Athar Field start producing since 1975 up to now with cummulativeproduction reached 900 MMbbls and RF 50%. 3D seismic was acquired in 2011 toidentify the remaining potential in this field.Analysis of 3D seismic with attribute and simultaneous inversion provide agood result to determine reservoar distribution and hydrocarbon contained. Densitycube from inversion, minimum amplutide attribute, anda arc length attribute are usedto map the sand distribution. Lambda Rho and AI (Ip) are usefull to identify theremaining hyrocarbon area. Structural interpretation from seismic shows there areminor faults which is not identified before with 2D seismic.The result of the analysis was used to create 3D Geomodel. The channel limitdetermination, and remaining hydrocarbon area guided by analysis from seismic andwell data. As a result, four channel bodies were identified, whilst overbank depositdistributed statistically. Structural interpretation data used to determine the number ofsegment or compartment, and the result are five segments in the south and onesegment in the north identified in the shallow zone Athar Field.The result of geological modeling shows that segment 5 still has prospect inoil production, whilst segment 2 has prospec in gas production]"