Fatahillah, Yosar (2016) Penentuan Potensi Batuan Induk Menggunakan Model Log Toc, Pada Formasi Ngimbang, Lapangan “Arrazi”, Cekungan Jawa Timur Utara. Diploma thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Formasi Ngimbang dikenal sebagai salah satu sumber pasokan utama hidrokarbon di Cekungan Jawa Timur Utara. Analisa laboratorium telah membuktikan Formasi Ngimbang sebagai batuan induk yang relatif kaya kandungan organik, ketersediaan data laboratorium terbatas untuk mengukur distribusi kematangan dan kuantitas material organik dalam skala luas cekungan regional. Hal inilah yang menjadi tujuan utama dalam penelitian ini. Dengan demikian dibutuhkan suatu metode sederhana yang terbukti dan akurat mengukur TOC (kandungan karbon organik) pada seluruh kedalaman lubang bor. Penelitian ini mengamati perilaku TOC Model berdasarkan data log sumur. Dengan demikian, akan menghemat banyak waktu dan menekan biaya observasi. Dalam penelitian ini, lima TOC logging model digunakan; Passey (1990), Schmoker-Hester (1983), Meyer-Nederloff (1984), Decker / Density Crossplot Model (1993), dan Improved Decker Model untuk kasus batugamping (serupa dengan model Decker). Selain itu digunakan juga model Mallick-Raju untuk menentukan tingkat kematangan formasi. Tiga data sumur dan data batuan inti yang digunakan untuk menentukan model yang paling cocok untuk diterapkan di formasi Ngimbang, sekaligus untuk membandingkan keakuratan nilai model TOC. Model Meyer-Nederloff hanya digunakan sebagai perbandingan standar model. Nilai LOM (Tingkat Metamorfisme) diperlukan untuk digunakan pada Passey Model dengan menggunakan crossplot antara DlogR dan TOC dari data inti. Perhitungan menggunakan Decker dan model Improved Decker dilakukan melalui diskritisasi interval kedalaman terhadap sifat geologis dan fisik batuan. Hasil menggambarkan buruknya akurasi model Schmoker-Hester yang diakibatkan oleh rendahnya kandungan mineral pirit, dan rasio yang berbeda antara besar bahan organik dan bahan karbon organik. Dengan demikian, dibutuhkan koreksi lanjutan dengan karakteristik Formasi Ngimbang untuk dapat membentuk model yang akurat dengan pendekatan yang sama dengan model Scmoker-Hester. Penerapan metode Passey, baik yang diturunkan dari log sonic dan log densitas
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menunjukkan banyak nilai TOC negatif. Kami menyimpulkan bahwa ini adalah hasil dari waktu sonic transit yang sangat rendah (<242 us/m) dan tingkat yang lebih tinggi dari LOM> 10,5. Dengan mempertimbangkan hal-hal di atas, diasumsikan bahwa Formasi Ngimbang sebagian besar bersifat batu induk "Non-Passey". Sebaliknya, Model Decker untuk observasi Shale memberikan hasil yang memuaskan dengan memperlihatkan korelasi yang relatif akurat antara log densitas denganTOC batu inti (koefisien korelasi 0,867). Improved Decker Model pada batugamping memberikan hasil yang akurat baik secara kuantitatif dan kualitatif. Namun, regresi linear pada Limestone memberikan korelasi yang lebih rendah (0,764). Penerapan metode ini lebih rumit dibandingkan pada Decker batuserpih dikarenakan selisih nilai TOC dari batugamping pada Ngimbang atas (didominasi batuserpih) dan Ngimbang bawah (didominasi batugamping) sangat signifikan. Hal ini disebabkan karena kedua sub-formasi memiliki perbedaan yang signifikan dalam litologi, kematangan, dan latar burial history (sejarah pengendapan).
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Ngimbang Formation is known as one major source of hydrocarbon supply in the North Eastern Java Basin. Although, laboratory analyses prove the Ngimbang Formation to be relatively rich source rock, such data are typically too limited to regionally quantify the distribution of organic matter on basin wide scale, which is the main objective in this research. Therefore, a simple- acurately proven method to quantify the TOC (Total Organic Carbon Content) throughout the borehole is needed. This research observes the behavior of TOC Model based on well log data. Thus, will save splendid amount of both time and observation cost. We also include observations on application of linear regression on the relation of both Density, Gamma Ray, and Resistivity log to changes in TOC Value on Limey Mudstone which is the same approach as Decker Model, but not on the Shalestone. Hence, this research will deliver clearer description of unconeventional gas (Shale Gas) potential in Indonesian Source rocks In this research, five TOC logging calculation models is used; Passey (1990), Schmoker-Hester (1983), Meyer-Nederloff (1984), Decker/ Density Crossplot Model (1993), Improved Density Crossplot Model suited to Limestone (closesly similar to Decker model), and Vitrinite Reflectance (Ro) model. Three wells data along with its available core data was used to determine the most suitable model to be applied in the Ngimbang formation, as well as to compare the accuracy of these TOC model values. Meyer-Nederloff Model was only used as standard comparison model. The value of LOM (Level of Metamorphism) needed to use on Passey Model was determined by using crossplot between DlogR and TOC from core data. Calculation using Decker and Improved Density Crossplot model was made through discretization of depth interval with respect to its geologic and physical properties. The result describes the lack of accuracy of Schmoker-Hester Model as a result of low amount of pyrite component, and different ratio of organic matter and organic carbon matter. Thus, further correction with Ngimbang Formation characteristics is needed to establish accurate model with
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similar approach as Scmoker-Hester model. Application of Passey method, both derived from sonic and density log shows numerous negative TOC value. We concluded that this was the result from particularly low sonic transit time (<242 us/m) and higher degree of LOM>10.5. To which considering both requirement, we can assume that the Ngimbang Formation is mostly “Non-Passey” source rocks. In contrast, the Decker Models for Shale observation gives satisfactory result. Producing relatively accurate correlation between the density log to core TOC (correlation coefficient of 0.867 was obtained). Improved Decker Model applied to Limestone gives accurate result both quantitatively and qualitatively. However, linear regression on the Limestone gives lower correlation (0.764). Application of this method has to be carefully maintained as difference in TOC values of Limestone in Upper Ngimbang (Shale dominated) and Lower Ngimbang (Limestone dominated) is eloquent, since both sub-formation have significant difference in lithologic, maturity, and geologic background.
| Item Type: | Thesis (Diploma) |
|---|---|
| Additional Information: | RSGf 526 Fat p |
| Uncontrolled Keywords: | Model Log TOC, Passey Model, Schmoker Hester Model, Density Log, TOC |
| Subjects: | T Technology > TN Mining engineering. Metallurgy |
| Divisions: | Faculty of Civil, Environmental, and Geo Engineering > Geophysics Engineering > 33201-(S1) Undergraduate Theses |
| Depositing User: | EKO BUDI RAHARJO |
| Date Deposited: | 09 Oct 2019 08:57 |
| Last Modified: | 09 Oct 2019 08:57 |
| URI: | http://repository.its.ac.id/id/eprint/71093 |
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