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"Teknik Amplitude Variation Offset (AVO) sudah sering digunakan dalam memprediksi pengendapan hidrokarbon. Knott dan Zoeppritz mengembangkan metode AVO dengan menggunakan nilai dari kecepatan gelombang primer (vp), kecepatan gelombang sekunder (vs) dan densitas. Kemudian, Rutherford dan William membagi AVO menjadi 4 kelas berdasarkan grafik intercept dan gradien. Metode ini telah sukses digunakan dibeberapa kasus dalam memprediksi keberadaan hidrokarbon. Namun, dibeberapa kasus masih ada ambiguitas dan misinterpretasi seperti yang terjadi pada respon minyak dan air dimana nilai porositas yang besar dan karakter yang mirip, sehingga pada penelitian ini diperlukan AVO attribute baru yang diberi nama J-atribut untuk memprediksi keberadaan hidrokarbon dan mengurangi ambiguitas pada hasil interpretasi. Metode J-attribut belum banyak diaplikasikan di lapangan Indonesia. Metode ini dilakukan pada Lapangan Fauna yang berlokasi di Daratan Cekungan Sumatera Utara. Data yang digunakan pada penelitian ini yaitu data 3 sumur yang dilengkapi dengan well marker dan data log seperti Gamma Ray, SP, Caliper, Neutron Porosity, Density, Resistivity, DT, Photoelectric, dan checkshot.

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The Amplitude Versus Offset (AVO) technique has often been used to predict the occurrence of hydrocarbons. Knott and Zoeppritz developed the AVO method by using values of primary wave velocity (vp), secondary wave velocity (vs) and density. Rutherford and William divide AVO into 4 classes based on intercept and gradient attributes. This method has been successfully used to predict hydrocarbons. However, in some cases there are still ambiguities and misinterpretations such as those occurred in oil and water zones have large porosity but with similar characters. In this study we have used a new AVO attribute approach the so called J-attribute to reduce ambiguities in the interpretation. The J-attribute has not yet been tried in the Indonesian fields. This method was carried out in the Fauna Field, which is located in the North Sumatra Basin. The data used in this study consist of 3 wells completed by markers and log data such as Gamma Ray, SP, Caliper, Neutron Porosity, Density, Resistivity, DT, Photoelectric, and checkshot surveys."

"Dalam penelitian ini, telah diestimasi parameter anisotrop dan untuk reservoir dan shale layer. Hal ini telah dilakukan menggunakan data sumur dari 7 sumur lapangan ldquo;G rdquo;, termasuk log sonik gelombang P dan log sudut inklinasi dari sumur bor. Kecepatan dari log sonik dan sudut inklinasi diterapkan pada persamaan polinomial orde kedua, termasuk parameter dan. Software Matlab digunakan untuk melakukan perhitungan parameter anisotrop, sedangkan Microsoft Excel digunakan untuk melakukan plot kecepatan terhadap sudut inklinasi. Kemudian hasil dari parameter anisotrop di kuantifikasi terhadap informasi litologi di sumur. Kemudian akan dilakukan analisis AVO pada kasus isotrop dan anisotrop sebagai perbandingan. Hal ini akan mengarah kepada indikasi terkait bagaimana pentingnya melibatkan parameter anisotrop. Nilai parameter anisotrop yang telah diperoleh tersebut diterapkan dalam analisis AVO, dilakukan pada seluruh sumur. Pendekatan menggunakan persamaan Shuey diterapkan dalam penelitian ini. Kasus anisotrop telah dibandingkan dengan kasus isotrop dengan melakukan plot koefisien refleksi terhadap sudut datang. Hasilnya menunjukkan bahwa terdapat perbedaan antara kasus isotrop dan kasus anisotrop pada offset jauh.

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In this work, the anisotropy parameters, dan for the reservoir and the shale layer on the G field have been estimated. This was done using well logs from 7 wells, including P wave sonic log and the inclination angle of the wellbore. The velocity from the sonic log and the inclination angle were applied to a second order polynomial equation, wich includes the anisotropy parameter. The Matlab software was utilized to perform the calculations, while Microsoft excel was utilized to plotting velocity versus inclination angle. Afterwards, the value of anisotropy parameter will be used for quantification of lithologic information on well data. Further on, an AVO analysis will be performed for the anisotropic case and the isotropic case for comparison. This will lead to an indication of how important including the anisotropy in AVO analyses can be. These parameters were applied in an AVO analysis, performed for all well. An approximation using the 3 term Shuey equation was applied for this purpose. The anisotropic case was compared with the isotropic case by plotting reflection coefficient with incidence angle. This showed that there is an evident difference between the isotropic and the anisotropic model at large offsets."

"Lateral lithology and saturation heterogeneities are key aspects of reservoir characterization. Amplitude versus offset (AVO), which is based on the change in reflection response caused by the change in incident angle, provides the relationship between reservoir parameters, petrophysical parameters, and elastic constants.Conventional AVO analysis and modeling by iteratively picking on the reflection event can sometimes be challenging due to practicalities of picking, resolution problems, and thin layer effects. Lithofacies identification based on seismic impedance inversion can alleviate these difficulties. Impedance inversion is also relatively free from the horizon interpretation problem, which can be subjective in heterogeneous reservoirs.In this study, we modify the Extended Elastic Impedance (EEI) method to predict lateral lithologic and saturation heterogeneities from seismic data. To validate the developed method, we apply Simultaneous AVO inversion. The modified extended elastic impedance method uses a least squares weight combination of intercept and gradient to produce lateral and vertical elastic parameters or log analysis of interest. This method provides more reliable and stable results compared to the original extended elastic impedance. In addition, the method produces any type of elastic parameter without an explicit relation function."

"Area penelitian merupakan struktur pengembangan pada bagian timur struktur "Sulis" dengan luas area sekitar 3 km2 dan merupakan kompartemenisasi batupasir. Perbedaan batas minyak air pada sumur-sumur existing mengindikasikan adanya perbedaan facies dan lingkungan pengendapan dari batu pasir. Terbatasnya jumlah sumur produksi serta data geologi pada area penelitian ini yang dapat memperkirakan penyebaran hidrokarbon secara lateral dan perubahan facies batupasir dapat menyebabkan suatu potensi kegagalan dalam memperoleh kandungan hidrokarbon pada pemboran sumur-sumur pengembangan di struktur "Sulis" ini. Tesis ini membahas metode analisa untuk dapat memperkirakan zona penyebaran hidrokarbon serta perkiraan jenis kandungannya. Perkiraan dari sebaran zona hidrokarbon adalah berdasarkan analisa dari kontras perubahan nilai poisson's ratio yang tinggi serta adanya respon anomali seismik pada area penelitian. Nilai poisson's ratio pada kisaran 0.1-0.2 diperkirakan merupakan jenis kandungan gas dan kisaran 0.2 - 0.3 merupakan jenis kandungan minyak. Data-data yang digunakan berupa data seismik 3D prestack gather dari struktur "Sulis", log sonic dan log density sumur acuan X-63 dan diproses menggunakan software Hampson Russell. Analisa AVO ini dilakukan dengan metode forward modelling yang meliputi poses Fluid Replacement Modelling, perhitungan perubahan nilai skala poisson's ratio serta analisa Amplitude Versus Offset. Hasil analisis yang berupa peta perubahan nilai poisson's ratio serta respon seismik berupa anomaly amplitude telah dapat digunakan untuk mengidentifikasi zona penyebaran hidrokarbon pada area penelitian di struktur "Sulis".

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The area of study is development structure at the east of "Sulis" structure with 3km2 of wide. This area consist of sandstone compartement with variation of deposition environment. The diference of oil water contact at the existing wells were indicated different of sandstone facies and deposition environment. The limitation of production wells and geology data to estimate lateral hydrocarbon distribution and sandstone facies in this area will be a failure risk potential in drilling wells development at "Sulis" structure.

The topic of this thesis is discussed about the methode analysis to predict about the distribution and type of hydrocarbon. The estimation of hydrocarbon distribution zone is base on high contrast of poisson's ratio changed and seismic anomali respons in the area study. The value of Poisson's ratio in the range 0.1 - 0.2 is estimated of gas type and in range 0.2 - 0.3 is estimated of oil type.

3D seismic prestack gather of "Sulis" structure, sonic and density log of existing X- 63 well was used in processing analysis with Hampson Russell software. The AVO analysis is include forward modelling methode, fluid replacement modelling, scaled poisson's ratio changed and amplitude versus offset.

The analysis result of scaled poisson's ratio changed and amplitude anomalies respons has identified the distribution zones and type of hydrocarbon in area study of "Sulis" structure."