Karakterisasi Overpressure Melalui Analisa Geomekanika 1d Pada Formasi Cibulakan Tengah, Cibulakan Bawah, Dan Jatibarang Di Cekungan Jawa Barat Utara.

Pramudhita, Benedictus Dicky Pradnya Agung (2022) Karakterisasi Overpressure Melalui Analisa Geomekanika 1d Pada Formasi Cibulakan Tengah, Cibulakan Bawah, Dan Jatibarang Di Cekungan Jawa Barat Utara. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Kecelakaan pengeboran akibat overpressure telah terjadi beberapa kali dalam dua dekade terakhir ini, salah satunya pada Lumpur Sidoarjo (Lusi). Berdasarkan data peta kejadian overpressure di dunia, didapatkan bahwa hampir seluruh lapangan migas di Indonesia terindikasi adanya overpressure. Fenomena tersebut terindikasi pada hampir setiap lingkungan geologis dan dalam strata segala usia. Perencanaan pengeboran harus disiapkan dengan memiliki model geomekanik pra-pengeboran melalui identifikasi karakteristik overpressure tiap lapangan. Oleh sebab itu, dilakukan estimasi tekanan pori dan overpressure melalui pengolahan analisa geomekanika 1 dimensi menggunakan data log. Perbedaan respon logging sifat petrofisika dalam interval overpressure dapat digunakan untuk menentukan asal usul, kedalaman. pemadatan tidak seimbang dan ekspansi fluida (terutama generasi gas) yang umum dikenal dengan loading dan unloading. Analisa geomekanika akan dilakukan dengan menghitung semua orientasi stress yaitu overburden stress (Sv), horizontal minimum stress (Sh min), dan horizontal maksimum stress (SH max) sehingga dapat dianalisa regime stress pada Jatibarang. Estimasi tekanan pori akan dilakukan melalui metode Eaton dengan validasi kurva NCT sehingga dapat dilakukan klasifikasi zona overpressure tiap kedalaman. Penentuan mekanisme overpressure akan dilakukan melalui analisa kombinasi analisa kurva log, crossplot sonic velocity–density serta density–sonic transit time, dan estimasi tekanan. Didapatkan bahwa mekanisme berupa unloading yang diindikasi penyebabnya adalah ekspansi fluida, baik oleh pembentukan hidrokarbon ataupun transformasi mineral. Terlihat bahwa formasi dominan terletak di bawah kurva telodiagenesis yang menandakan adanya pengaruh mekanisme unloading dengan laju sedimentasi 100 m/jt tahun. Melalui sifat kurva log dan estimasi tekanan pori dapat dideteksi adanya top overpressure pada kedalaman 2220.8 meter dan 2231.1 meter karena adanya kandungan serpih yang relative tinggi pada formasi Cibulakan Tengah. Melalui orientasi stress didapatkan struktur patahan sub-cekungan Jatibarang berupa patahan normal dan strike-slip berdasarkan klasifikasi Anderson dan Zoback. Berdasarkan analisa orientasi stress geomekanika 1D dan estimasi tekanan pori didapatkan saran berat lumpur menggunakan persamaan Mohr-Coulomb sebagai referensi sumur eksplorasi atau eksploitasi baru di cekungan Jatibarang.
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Drilling accidents due to overpressure have occurred several times in the last two decades, one of which was in the Sidoarjo (Lusi) mud. Based on map data of overpressure events in the world, it was found that almost all oil and gas fields in Indonesia indicated overpressure. This phenomenon is indicated in almost every geological environment and in strata of all ages. Planning must be prepared by having a pre-drilled geomechanical model through the overpressure characteristics of each field. Therefore, it is necessary to estimate pore pressure and overpressure through one-dimensional geomechanical analysis using log data. The difference in the response to logging of petrophysical properties in the overpressure interval can be used to determine the origin, depth. unbalanced compaction and expansion of fluids (especially gas generation) commonly known as loading and unloading. Geomechanical analysis will be carried out by calculating all stress orientations, namely overburden stress (Sv), horizontal minimum stress (Sh min), and horizontal maximum stress (SH max) so that the stress regime in Jatibarang can be analyzed. Pore pressure estimation will be carried out using the Eaton method with NCT curve validation so that the classification of overpressure zones at each depth can be carried out. Determination of the overpressure mechanism will be carried out through a combination of log curve analysis, crossplot sonic velocity–density and density–sonic transit time, and pressure estimation. It was found that the mechanism in the form of unloading indicated the cause was fluid expansion, either by the formation of hydrocarbons or by mineral transformation. The dominant formation is located on the lower curve of telodiagenesis which indicates the influence of the demolition mechanism with a sedimentation rate of 100 m/m year. Through the nature of the log curve and the estimated pore pressure, it can be detected that there is top overpressure at a depth of 2220.8 meters and 2231.1 meters due to the relatively high shale content in the Central Cibulakan Formation. Through stress orientation, the fault structure of the Jatibarang sub-basin is found in the form of normal and strike-slip faults based on the Anderson and Zoback classification. Based on the 1D geomechanical stress orientation analysis and using the pressure estimate, the Mohr-Coulomb equation suggests mud weight as a reference for new exploration or exploitation wells in the Jatibarang Basin.

Item Type:	Thesis (Other)
Additional Information:	RSGf 531.1 Pra k-1 2022
Uncontrolled Keywords:	Geomekanika, Jatibarang, Overpressure. Geomechanic, Jatibarang, Overpressure.
Divisions:	Faculty of Civil, Planning, and Geo Engineering (CIVPLAN) > Geophysics Engineering > 33201-(S1) Undergraduate Thesis
Depositing User:	Mr. Marsudiyana -
Date Deposited:	21 May 2026 08:03
Last Modified:	21 May 2026 08:03
URI:	http://repository.its.ac.id/id/eprint/133321

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