Hasil Pencarian  ::  Simpan CSV :: Kembali

Abstrak :
Inversi seismik deterministik sudah banyak digunakan dalam lapangan eksplorasi dan pengembangan. Metode ini digunakan sebagai salah satu cara untuk karakterisasi reservoir dengan menghilangkan efek wavelet sehingga dapat membantu interpreter untuk memetakan struktur bawa permukaan dengan lebih baik. Akan tetapi, metode ini memiliki limitasi karena menggunakan impedansi rata-rata dari layer seismik dimana pada umumnmya nilai impendansi lebih kecil daripada impedansi data sumur sehingga dihasilkan model inversi yang tidak sesuai. Metode inversi stokastik menggunakan konsep geostatistikal, dimana variogram berperan penting dalam menghasilkan output yang sesuai. Pada inversi stokastik dihasilkan banyak realisasi inversi yang digunakan sebagai basis dalam analisis uncertainty, tiap realisasi akan sama pada tiap lokasi sumur yang digunakan namun akan berubah seiring dengan bertambahnya jarak spasial dari lokasi sumur. Metode inversi stokastik akan diaplikasikan pada lapangan gas “K” yang terletak di lepas pantai cekungan Bonaparte, Indoensia Timur. Data yang tersedia antara lain, sebagian dari 3D PSTM angle gather dengan luasan 1,300 km2, 3 sumur dengan data P-Sonic, S-Sonic, densitas, Gamma Ray, dan log resistivitas. Tambahan data berupa report komplesi dan report well testing tersedia untuk beberapa sumur. Lapangan gas “K” terletak pada undeformed continental margin Australia yang melampar kearah lndonesia, dimana secara geologi lapangan “K” terletak pada area Timur dari Sahul Platform dan memiliki struktur berupa tiltef fault block. Lapangan ini memiliki reservoir batupasir formasi Plover yang tersaturasi gas dengan hidrokarbon kolom cukup signifikan, dimana reservoir terdeposisi pada lingkungan shallow marine pada umur Middle Jurasic. Target utama pada lapangan gas “K” merupakan strukutural trap berupa horst block, tilted fault block yang berada dibawah sub-unconformity di umur Palaezoic. Penerapan metode inversi stokastik pada lapangan gas “K” menghasilkan kelebihan yang cukup signifikan dibandingkan dengan inversi deterministik. Reservoir pada lapangan gas “K” terdiri dari batupasir dengan persilangan shale tipis. Metode inversi stokastik dapat membedakan antara batupasir yang tersaturasi gas dengan intraformational shale tipis yang tidak teresolusi oleh seismik dan inversi deterministik. Hasil realisasi dapat digunakan untuk analisis uncertainty dengan probabilitas P10, P50, dan P90 dari facies yang dihasilkan. ......Deterministic seismik inversion method has been successfully used in various projects in exploration and development. This method enables the interpreter to get better understanding of subsurface by omitting the wavelet and tuning effects therefore quantitative reservoir properties can be generated. However, this method has significant limitation by generating average impedances of each layer, and the range of values is smaller than the impedance from the wells therefore the inversion will not produce results that are not within the calibration range. Stochastic seismik inversion is done by conditioning well data and reproducing spatially varying statistics using variogram which could overcome the deterministic limitation. This method generates multiple realizations of high-frequency elastic properties that are consistent with both seismik amplitude and well data. In such instances, stochastic seismik inversion method could provide the uncertainties associated with the models that have been generated. The proposed method is applied in “K” gas field which located in the offshore Bonaparte Basin, Eastern Indonesia. The available dataset for this work includes : part of PSTM 3D which cover 1,300 km2 in angle gather, and 3 wells with compressional sonic, shear sonic, density, gamma ray, and resistivity logs. Additional well completion and well testing reports are available for some wells. Geologically, the “K” field is located within relatively undeformed Australian continental margin that extends into Indonesian waters. It lies on the eastern extremity of the Sahul Platform and occupies a large tilted fault block bounded to the east and south by the Calder-Malita Grabens. This field contains a significant gas column, reservoired within shallow marine, highly mature, quartzose sandstone of the Middle Jurassic Plover Formation. Potential targets in the area may be large folds, horst blocks, tilted fault blocks ad sub-unconformity traps in the Palaeozoic section. The application of stochastic seismik inversion showed significant benefits compared to deterministic especially in “K” gas field where the reservoirs are stacked sandstone with intraformational shale. Some of the reservoir and all the intraformational shales are below seismik resolution. Stochastic seismic inversion able to distinguish those features, in addition the inverted volumes with multiple realizations with ranking criteria for P10, P50, and P90 of facies could be utilized to reduce the risk associated with exploration plan and field development.

Abstrak :
Lapangan Phy berada di lingkungan pengendapan delta plain dengan beberapa kualifikasi; batupasir yang berasal dari sungai adalah sungai - sungai yang memiliki sejarah geologi berbeda dengan ketebalan 20 - 40 meter, beberapa sungai - sungai kecil dengan ketebalan 10 - 15 meter, dan endapan sungai lainnya ketebalannya sekitar 2 meter. Berdasar kondisi geologi, lapangan Phy memiliki beberapa paket batupasir pada masing - masing log. Litologi pada lapangan ini juga bervariasi; batupasir, batulempung, batubara, dan gamping. Lapangan ini juga memiliki beberapa tantangan yaitu : a. Klasifikasi litologi dan fluida pada zona sangat dangkal (di atas 700m) dan sangat dalam (di bawah 3000 m) sulit diidentifikasi karena isu amplitude seismic b. Delineasi litologi spasial dan distribusi fluida sulit dipetakan karena anisotropi data seismic c. Resolusi vertikal untuk karakterisasi reservoir kurang baik karena paket batupasir yang tipis. Untuk menyelesaikan tantangan - tantangan tersebut, inversi simultan dan inversi geostatistik dilakukan pada lapangan ini. Separasi litologi dapat dilakukan dengan baik pada zona 2 (lebih kurang 2000 - 5000 m. Namun terdapat beberapa pertimbangan untuk menggunakan hasil inversi simultan dan geostatistik pada lapangan Phy. Kedua hasil inversi simultan dan geostatistik tidak dapat memetakan distribusi hidrokarbon baik secara vertikal maupun horizontal. Hal ini disebabkan karena hasil analisis petrofisika dan fisika batuan tidak memberikan hasil yang dapat merepresentasikan separasi litologi dan fluida. Beberapa perbaikan untuk klasifikasi fluida pada lapangan ini perlu dipelajari lebih lanjut. Melalui korelasi litologi, inversi simultan dan geostatistik dapat memetakan distribusi batupasir dengan baik meskipun beberapa keterbatasan muncul. Distribusi lateral dari prediksi batupasir berkorelasi dengan baik terhadap informasi net sand dari data sumur tetapi resolusi vertikal kurang baik. Secara kontras, inversi geostatistik memberikan hasil yang lebih detail dalam resolusi vertikal tetapi tidak berkorelasi cukup baik dengan data net sand dari sumur karena efek pemodelan variogram. ......Phy field is located on delta plain depositional environment with several qualifications; channel sand bodies are either multi - story channels with a thickness of 20 to 40 meters, many single channels with a thickness of 10 to 15 meters, and distributary channels deposits gave mouth bars with a thickness of around 2 meters. Due to this geological condition, Phy field has several sand packages on each log. The lithology of this field is also varied; sandstone, shale, coal, and limestone. This field also has several challenges: d. Lithology and fluid classification at Very Shallow (above 700 m) and Very Deep (below 3000 m) zones, caused by seismic amplitude issue e. Spatial lithology and fluid distribution delineation, caused by seismic anisotropy f. Vertical resolution resolving of reservoir characterization, caused by thin sand packages. To solve those challenges on Phy field, simultaneous inversion (SI) and geostatistical inversion (GI) have been conducted on this field. Lithology separation could be conducted well from Zone 2 (more or less 2000 - 2500 m). Nevertheless, there are several considerations to use GI and SI in Phy field. Both simultaneous and geostatistical inversion results could not characterize hydrocarbon distribution vertically and horizontally. It is because of the petrophysics and rock physics result of elastic properties which have been used as the inputs for lithology and fluid classification. Several enhancements for the classification for this field are needed to be studied deeper. Through lithology correlation, simultaneous and geostatistical inversion could delineate sand distribution well even though some limitations also overcome. Simultaneous inversion lateral distribution of sand prediction correlates well to net sand information from wells but lack of vertical resolution. Besides, geostatistical inversion gives more detail in vertical resolution of capturing thin sands but lack of lateral prediction of sands because of variogram effect.

Abstrak :
ABSTRAK Pengamatan sinyal gempa bumi di seluruh dunia memungkinkan para ahli seismologi untuk mengetahui struktur internal dari bumi terutama kerak buminya. Dalam penelitian ini, dilakukan analisa terhadap receiver function dan dispersi gelombang permukaan di daerah Jawa bagian Barat, Indonesia. Penelitian ini bertujuan untuk : (1) Memodelkan struktur kecepatan kerak bumi di daerah Jawa bagian barat yang didapatkan dari join inversi receiver function dan dispersi gelombang permukaan, (2) Mengetahui ketebalan kerak bumi di daerah Jawa bagian barat dan (3) Mengetahui keberadaan Low Velocity Zone ( zona kecepatan rendah). Receiver function dihitung dari data gempa dengan magnitude lebih besar dari 5 dengan jarak episenter 30o - 90o dengan teknik iterasi dekonvolusi. Dispersi gelombang permukaan diperoleh dengan menggunakan analisis frekuensi waktu dari gempa dengan manitude lebih besar dari 5 dengan jarak 30o - 40o. Dari hasil join inversi yang dilakukan, didapatkan model kecepatan struktur kerak bumi di daerah Jawa Bagian Barat dengan ketebalan kerak bervariasi pada tiap stasiun yaitu antara 30-38 km. Ketebalan kerak paling tebal terdapat di Zona Pegunungan Bayah dan Zona Bandung. Struktur kecepatan kerak bumi pada stasiun yang berada pada zona fisiografi yang sama memiliki kesamaan pola kecepatan Vs.

---

ABSTRACT Earthquake signal observations around the world allow seismologists to obtain the information of internal structure of the Earth especially the Earth's crust. In this study, receiver functions and surface wave dispersion analized in Western Java, Indonesia. The objectives of this study (1). Modelling crustal structure velocity of western java obtained from joint inversion of teleseismic data receiver function and surface wave dispersion (2) To find out the earth's crust thickness in Western Java and (3). To find out the existence of low velocity zone. Receiver function were calculated from earthquakes with magnitude more than 5 and at distance 30o - 90o, with iterative deconvolution technique. Surface wave dispersions were calculated using frequency time analysis from earthquakes at distance 30o - 40o. Crustal velocity structure model in Western Java obtained from joint inversion receiver function and surface wave dispersion, and crustal thickness beneath each station is about 30-38 km. Pegunungan Bayah zone and Bandung zone has the most thick earth crust. Crustal structure velocity has identically pattern which are in the same physiography zone.

Abstrak :
[ABSTRAK
Lapangan XXX merupakan lapangan minyak di cekungan Natuna Barat dengan reservoir utama berupa reservoir batu pasir. Ketebalan reservoir pada lapangan ini sangat bervariasi sehingga hasil inversi hanya dapat memetakan ketebalan reservoir yang mendekati ketebalan tuning. Berdasarkan uji sensitifitas, parameter AI di setiap sumur tidak dapat membedakan hidrokarbon, sehingga parameter akustik saja tidak dapat diaplikasikan dalam karakterisasi reservoir lapangan ini. Namun ketika parameter densitas terpisah dengan parameter kecepatan P, sebaran hidrokarbon dapat dibedakan dengan baik. Kecepatan S tidak tersedia di semua sumur padahal data ini sangat diperlukan untuk melakukan pengolahan data dengan metode inversi simultan. Oleh karena itu akan dilakukan beberapa estimasi untuk mendapatkan data kecepatan S antara lain dengan metode castagna, metode gassmann, metode parsial, metode Xu-White dan metode Lee. Data kecepatan S yang dipakai adalah kecepatan S terbaik yang diperoleh dari metode Xu White dikarenakan hasil log poisson’s rationya paling mendekati tren kurva saturasi air. Selain itu aspek rasio batuan yang mempertimbangkan nilai porositas dan volume clay, serta kontrol kualitas Vp model dari metode Xu-White memiliki rasio error minimum jika dibandingkan dengan nilai Vp dari data log. Metode inversi simultan dengan data pre-stack atau partial stack memungkinkan dilakukannya prediksi parameter Impedansi P, Impedansi S, dan densitas dari data seismik. Selain itu meode inversi simultan dapat dipergunakan multi wavelet dalam pengolahan datanya. Hasil penampang inversi yang diperoleh menunjukkan bahwa inverse densitas dapat menjelaskan letak sebaran batuan reservoir dan fluida berdasarkan cut off sensitifitas yakni nilai dibawah 2,26 gr/cc.

---

ABSTRACT
field is an oil field in West Natuna Basin with sandstone reservoir as primary target. There was varying reservoir thickness, so the inversion method that could only be applied to map reservoir thickness, which close to tuning thickness. Based on sensitivity analysis, Acoustic Impedance parameters couldn’t indicate hydrocarbon appearance for each well, so Acoustic Impedance cannot be applied for reservoir characterization in this field. Density versus Acoustic Impedance could map hydrocarbon appearance. Shear velocity weren’t available where those data was needed for running simultaneous inversion method. Predicting velocity shear would be carried out by using several method such as Castagna, Gassmann, Parsial, Xu-White, and Lee. The best estimated velocity shear would be used for inversion, The best estimated shear velocity from Xu-White method because Xu-White’s poisson ratio log presents similar trend with water saturation log (Sw). Moreover, Xu-White’s ratio aspect is also considering porosity and clay volume value. Based on quality control result, Vp model of Xu-White had minimum error ratio compared to Vp from log. Simultaneous inversion with pre-stack and parsial stack data what can be used for predicting P-Impedance, S-Impedance, and density from seismic data. Otherwise, this method is also used not only for single wavelet but also multi wavelet. The inversion result from this study can mapping out the hydrocarbon appearance for reservoir target based on cut off value from sensitivity test of less than 2,26 gr/cc.;X field is an oil field in West Natuna Basin with sandstone reservoir as primary target. There was varying reservoir thickness, so the inversion method that could only be applied to map reservoir thickness, which close to tuning thickness. Based on sensitivity analysis, Acoustic Impedance parameters couldn’t indicate hydrocarbon appearance for each well, so Acoustic Impedance cannot be applied for reservoir characterization in this field. Density versus Acoustic Impedance could map hydrocarbon appearance. Shear velocity weren’t available where those data was needed for running simultaneous inversion method. Predicting velocity shear would be carried out by using several method such as Castagna, Gassmann, Parsial, Xu-White, and Lee. The best estimated velocity shear would be used for inversion, The best estimated shear velocity from Xu-White method because Xu-White’s poisson ratio log presents similar trend with water saturation log (Sw). Moreover, Xu-White’s ratio aspect is also considering porosity and clay volume value. Based on quality control result, Vp model of Xu-White had minimum error ratio compared to Vp from log. Simultaneous inversion with pre-stack and parsial stack data what can be used for predicting P-Impedance, S-Impedance, and density from seismic data. Otherwise, this method is also used not only for single wavelet but also multi wavelet. The inversion result from this study can mapping out the hydrocarbon appearance for reservoir target based on cut off value from sensitivity test of less than 2,26 gr/cc., X field is an oil field in West Natuna Basin with sandstone reservoir as primary target. There was varying reservoir thickness, so the inversion method that could only be applied to map reservoir thickness, which close to tuning thickness. Based on sensitivity analysis, Acoustic Impedance parameters couldn’t indicate hydrocarbon appearance for each well, so Acoustic Impedance cannot be applied for reservoir characterization in this field. Density versus Acoustic Impedance could map hydrocarbon appearance. Shear velocity weren’t available where those data was needed for running simultaneous inversion method. Predicting velocity shear would be carried out by using several method such as Castagna, Gassmann, Parsial, Xu-White, and Lee. The best estimated velocity shear would be used for inversion, The best estimated shear velocity from Xu-White method because Xu-White’s poisson ratio log presents similar trend with water saturation log (Sw). Moreover, Xu-White’s ratio aspect is also considering porosity and clay volume value. Based on quality control result, Vp model of Xu-White had minimum error ratio compared to Vp from log. Simultaneous inversion with pre-stack and parsial stack data what can be used for predicting P-Impedance, S-Impedance, and density from seismic data. Otherwise, this method is also used not only for single wavelet but also multi wavelet. The inversion result from this study can mapping out the hydrocarbon appearance for reservoir target based on cut off value from sensitivity test of less than 2,26 gr/cc.]

Abstrak :
Pemodelan sifat fisik batuan yang telah dilakukan dengan menggunakan data seismik, data sumur dan atribut seismik untuk mempelajari penyebaran kualitas reservoir pada daerah laut dangkal Natuna di lapangan N. Pemodelan dimulai dengan menentukan batasan vertikal reservoir dengan membagi litologi sand dan shale kedalam bentuk diskrit. Konstrain antara data litologi dengan atribut seismik ditentukan oleh koefisien dan probabilitas kemunculan pendekatan nilai. Pemodelan sebaran litologi berdasarkan variogram dengan statistik dan analisis atribut impedansi akustik. Hasil pemodelan sifat fisik batuan pada tiap sumur dijadikan acuan untuk menentukan kualitas reservoir di suatu titik. Penyebaran model petrofisika diprediksi dengan menggunakan Sequential Gausian Simulation. Jumlah sumur yang terbatas pada lapangan ini menjadi isu penting yang menyebabkan variogram kurang berperan dalam analisis data sehingga penyebaran model petrofisika lebih ditekankan dari analisis pengendapan reservoir. Hasil distribusi facies pada formasi Upper Arang terutama pada lapisan AA-20 dan AA-40 dominan berada pada daerah antiklin disekitar sumur dan perkembangan reservoir lebih ke arah barat. Pemodelan facies digunakan sebagai panduan dan kontrol untuk mendistribusikan properti reservoir dalam model geologi 3D yang ditampilkan dalam peta distribusi reservoir yang berupa penyebaran porositas, saturasi air dan Net to Gross. ......Physical properties modeling of rocks that have been done using seismic data, well data and seismic attributes to study the distribution of reservoir quality in shallow marine areas of the field N. Modeling begins by determining the vertical border of the reservoir with sand and shale lithology, which is divided into discrete form. Constraints between data lithology and seismic attribute determined by the coefficients and probability of occurrence value. Lithological distribution is based on variogram modeling with statistics and analysis of acoustic impedance attribute. The results of the physical properties modeling of rocks in each of the wells is used as a reference for determining the quality of the reservoir at a point. The distribution of petrophysical model is predicted using Gausian Sequential Simulation. Limited number of wells in this field becomes an important issue that causes less variogram plays a role in data analysis so that the distribution of petrophysical models emphasized more than the analysis of reservoir sedimentation. The results of facies distribution in Upper Arang formation mainly in the lining of AA and AA-20-40 dominant anticline located on the area around the well and reservoir development further to the west. Facies modeling is used as a guide and control to distribute the reservoir properties in a 3D geological model shown in the map of the spread of the distribution of reservoir porosity, water saturation and Net to Gross.

Abstrak :
Lapangan geotermal X berada di area gunung A yangmana berdasarkan data geologi ditemukan adanya manifestasi berupa hot spring dan fumarole. Pengukuran MT dilakukan untuk mengetahui persebaran resistivity batuan di bawah permukaan. Pengolahan data MT dilakukan dari analisis time series dan filtering noise kemudian dilakukan Transformasi Fourier dan Robust Processing. Setelah itu baru dilakukan crosspower untuk menyeleksi data sehingga output dari proses ini berupa kurva MT. Setelah didapatkan kurva MT dilakukan koreksi statik dikarenakan kurva TE dan TM terjadi shifting. Untuk proses akhirnya baru dilakukan inversi 2D dan inversi 3D. setelah itu dilakukan perbandingan antara 2D dan 3D. Wilayah interest lapangan X berada di lintasan AA dan lintasan AB. Berdasarkan analisis 3D diidentifikasi bahwa zona alterasi menipis di wilayah upflow dan menebal ke arah outflow yangmana sesuai dengan teori. Wilayah upflow dapat diketahui dengan melihat manifestasi berupa fumarole.

---

The geothermal field X is located in the area of Mount A which based on geological data found the presence of hot spring and fumarole manifestations. MT measurements were carried out to determine the distribution of rock resistivity in the subsurface. MT data processing is starts from time series analysis and noise filtering then Fourier Transform and Robust Processing are performed. After that, crosspower is done to select data so that the output of this process is an MT curve. After got the MT curve then a static correction is done because the TE and TM curves are shifting. For the final process are 2D inversion and 3D inversion. After that make a comparison between 2D and 3D. The area of interest in field X is on the line AA and line AB. Based on the 3D analysis, it was identified that alteration zones thinned in the upflow region and thickened towards the outflow which is make sense with the theory.

Abstrak :
Lapangan "Z" merupakan salah satu lapangan hidrokarbon yang sedang dikembangkan dan berada di Cekungan Sumatra Selatan yang terkenal sebagai salah satu cekungan penghasil hidrokarbon terbesar di Indonesia. Pada awalnya inversi seismik dilakukan dengan hanya menghasilkan penampang impedansi akustik yang memiliki keterbatasan dalam mengidentifikasi litologi batuan serta kandungan fluidanya. Untuk mengatasi permasalahan tersebut, dilakukan inversi simultan yang dilakukan pada data pre-stack yang menghasilkan tiga parameter sekaligus, yaitu parameter impedansi akustik, impedansi shear, dan densitas. Ketiga parameter tersebut ditransformasi sehingga memperoleh parameter lame berupa nilai lambda-rho dan mu-rho yang lebih sensitif dalam mengidentifikasi litologi batuan maupun kandungan fluida di dalam reservoir. Skripsi ini bertujuan untuk mengkarakterisasi reservoir batupasir dengan menggunakan metode Simultaneous Inversion. Inversi ini dilakukan pada data pre-stack yang telah dikondisikan terlebih dahulu dengan kontrol dari data sumur dan horison. Hasil inversi yang diperoleh adalah reservoir batupasir berisi gas pada penelitian ini dicirikan dengan nilai lambda-rho yang rendah yaitu bernilai 5700-7000 (m/s)*(g/cc), impedansi-S yang tinggi yaitu bernilai 3200-4700 (m/s)*(g/cc), dan nilai mu-rho yang tinggi bernilai 11-14,3 GPa*g/cc. Sedangkan pada reservoir batupasir berisi minyak memiliki nilai lambda-rho yang tinggi sekitar 7000-9000 (m/s)*(g/cc). Reservoir batupasir pada penelitian ini relatif sangat tipis sehingga diperlukan ketelitian dalam menganalisisnya.

---

The 'Z' field is a hydrocarbon field that still on developement and located in the South Sumatra Basin that is known as one of the largest hydrocarbon-producing basins in Indonesia. At first, the seismic inversion is performed by simply generating acoustic impedance cross section that has limitations in identifying rock lithology and fluid content. To solve this problem, simultaneous inversion performed on the pre-stack data which generates three parameters simultaneously, namely acoustic impedance, shear impedance and density parameters. These parameters can be transformed to obtain lame parameter called lambda-rho and mu-rho which are more sensitive in identifying rock lithology and fluid content in the reservoir. This thesis aims to characterize the sandstones reservoir using Simultaneous Inversion method. This inversion is done on the pre-stack data which previously been conditioned with the control of wells and horizons. Inversion results obtained are gas-containing sandstone reservoir, which in this research identified with the small lambda-rho value about 5700-7000 (m/s)*(g/cc), high impedance-S value about 3200-4700 (m/s)*(g/cc), and high mu-rho value about 11-14.3 GPa*g/cc. In other side the oil-containing sandstone reservoir has a high lambda-rho value about 7000-9000 (m/s)*(g/cc). Sandstones reservoir in this study are relatively very thin, that means it is required a huge accuracy in analyzing it.

Abstrak :
ABSTRAK
Metode gravitasi merupakan metode geofisika yang didasarkan pada pengukuran variasi medan gravitasi karena adanya perbedaan rapat massa antar batuan. Oleh sebab itu, metode gravitasi sering digunakan dalam eksplorasi bawah permukaan, salah satunya eksplorasi hidrokarbon. Dalam proses awal, penentuan kedalaman basement dirasa penting supaya dapat dilanjutkan untuk melakukan reka ulang dalam menentukan zona reservoir hidrokarbon. Setelah penentuan basement selesai, dilanjutkan dengan melakukan permodelan inversi 3D supaya didapatkan gambaran detail mengenai struktur bawah permukaan yang mendekati bentuk sebenarnya. Berdasarkan hasil analisis data didapatkan kedalaman basement rata-rata sekitar 5.5 km dengan struktur pembentuknya adalah patahan naik dan arah strukturnya dari Timur Laut ke Barat Daya. Hasil model inversi 3D didapatkan basement yang terdeteksi merupakan batuan beku Andesite dengan nilai densitasnya sekitar 2.5 gr/cm3. Kemudian untuk zona reservoir hidrokarbon diperkirakan terletak di daerah central basin sampai bagian Selatan pulau Timor, dengan komposisi batuan reservoirnya adalah batuan sedimen pasir dengan nilai densitas sekitar 2.2 gr/cm3.

---

ABSTRACT
The method of gravity is a geophysical method which is based on the measurement of variation of the variative gravitational field due to the difference in mass density between rocks. Therefore, gravity methods are often used in subsurface exploration, one of which is hydrocarbon exploration. In the initial process, the determination of the basement depth is important in order to re establish the process in determining the hydrocarbon reservoir zone. After the basement determination is completed, the next step is to proceed with 3D inversion modeling in order to get a detailed picture of the subsurface structure that approximates the actual shape. Based on the data analysis, the average basement depth is about 5.5 km with its forming structure is the rising fracture and the direction of its structure from Northeast to Southwest. The result of 3D inversion model was found the detected basement is Andesite igneous rock with density value about 2.5 gr cm3. Then for the hydrocarbon reservoir zone is estimated to be located in the central basin area to the Southern part of the island of Timor, with the composition of the reservoir rock is sand sedimentary rock with a density value of about 2.2 gr cm3.

Abstrak :
Generalized (or pseudo-) inverse concepts routinely appear throughout applied mathematics and engineering, in both research literature and textbooks. Although the basic properties are readily available, some of the more subtle aspects and difficult details of the subject are not well documented or understood. This book is an excellent reference for researchers and students who need or want more than just the most basic elements. First published in 1979, the book remains up-to-date and readable, and it includes chapters on Markov Chains and the Drazin inverse methods that have become significant to many problems in applied mathematics.

Abstrak :
Lapangan Eka terletak di Cekungan Sumatra Tengah, dengan reservoar berupa batuan sedimen tersier utama yang memproduksi hidrokarbon. Reservoar lapisan tipis ini berada Formasi Bekasap dan dibagi menjadi 3 zona reservoar utama Bekasap A, B, dan C. Karakterisasi reservoir dilakukan untuk mendelineasi distribusi reservoir dalam Formasi Bekasap dengan menggunakan inversi seismik, Inversi Deterministik DI , dan Inversi Geostatistik GI. GI adalah metode simulasi yang menggunakan data seismik, hasil DI, dan data log sumur. GI dapat memisahkan reservoir yang tebal menjadi beberapa lapisan tipis yang ketebalan sebenarnya di bawah ketebalan tuning. Analisis cross plot menunjukkan Impedansi Akustik AI tidak dapat membedakan litologi antara pasir dan serpih dalam Formasi Bekasap. Namun, AI cukup baik dalam memisahkan pasir dan serpih pada Bekasap A dan Bekasap B. Lithologi pasir memiliki nilai impedansi akustik yang berkisar antara 18213 - 25043 gr / cm3 ft / s. Pasir berpori reservoir memiliki parameter cutoff tambahan yang porositasnya total, berkisar antara 0.2649 - 0.4136. Hasil DI mencitrakan hasil blocky pada distribusi batu pasir. Keterbatasan inversi deterministik dalam resolusi vertikal membuatnya sulit untuk membedakan reservoar berlapis tipis dan mengasumsikan lapisan tersebut sebagai satuan tubuh pasir yang tebal. DI juga tidak bisa menyelesaikan masalah non-keunikan. Tujuan dari penelitian ini adalah untuk menggambarkan distribusi reservoir dengan resolusi lebih tinggi. GI diterapkan pada alur kerja inversi. Hasil GI dapat mencitrakan distribusi reservoar berlapis tipis yang DI tidak dapat selesaikan. ......Eka field is located in Central Sumatra Basin, the largest principal Indonesia tertiary sediment basin producing hydrocarbon. Having great potential to produce hydrocarbon, Bekasap Formation were divided into 3 reservoir zones Bekasap A, B, and C. Reservoir characterization was conducted to delineate the distribution of reservoir within Bekasap Formation by generating seismic inversions, Deterministic Inversion DI, and Geostatistic Inversion GI . GI is a simulation method honoring seismic data, DI result, and well log data. The GI can separate the blocky layers of the reservoir into several thin layers which thicknesses are below the tuning thickness. Cross plot analysis showed the Acoustic Impedance AI cannot distinguish lithology between sand and shale in Bekasap Formation. However, AI is was quite good in separating sand and shale on Bekasap A and Bekasap B. The sand lithology has the value of acoustic impedance ranges from 18213 ndash 25043 gr cm3 ft s. The porous sand reservoir has additional parameter cut off which is porosity total, ranging from 0.2649 ndash 0.4136. DI result shows the blocky event on sand distribution. The limitation of deterministic inversion in vertical resolution makes it hard to differentiate the thin bed layers of reservoir which assumes the layers as one thick body sand. DI cannot resolve the non uniqueness matter. The aim of this research is to delineate the distribution of the reservoir with higher resolution. GI is applied to the inversion workflow. GI results in high definition imaging that can highlight the distribution of the thin bed reservoirs which DI cannot.