Judul: GEOKIMIA DAN PEMODELAN KEMATANGAN BATUAN INDUK PADA SUB-CEKUNGAN PENDALIAN, CEKUNGAN SUMATRA TENGAH===GEOKIMIA DAN PEMODELAN KEMATANGAN BATUAN INDUK PADA SUB-CEKUNGAN PENDALIAN, CEKUNGAN SUMATRA TENGAH
Pengarang: Winardi, Sarju ; Amijaya, Donatus Hendra ; Putri Dwi Afifah
Penerbit: Departemen Teknik Geologi FT. UGM
Tahun: 2023
Tipe: Tesis
Lokasi: Perpustakaan Departemen Teknik Geologi
ABSTRAK
Cekungan Sumatra Tengah merupakan salah satu cekungan penghasil hidrokarbon di Indonesia, Sub-Cekungan Pendalian yang merupakan bagian dari Cekungan Sumatra Tengah yang terindikasi memiliki potensi batuan induk yang cukup baik dan telah
memasuki fase kematangan puncak minyak (main oil) pada beberapa wilayah, namun penelitian mengenai batuan induk tersebut belum dieksplor secara mendetail sehingga menarik untuk diteliti. Penelitian ini dilakukan untuk mengetahui kualitas dan kuantitas batuan induk dari segi geokimia, dan menjelaskan sejarah kematangan serta memodelkan persebaran kematangan batuan induk tersebut pada daerah penelitian. Data yang digunakan meliputi data geokimia, well report, data log, dan data paleontologi dari enam sumur yang tersedia, penelitian ini juga menggunakan 14 lintasan seismik 2D. Metode yang digunakan berupa crossplot data geokimia untuk mengidentifikasi kualitas dan kuantitas batuan induk, pembuatan model kematangan batuan induk (1D) dengan kalibrasi data reflektansi vitrinit dan Bottom Hole Temperature (BHT). Pembuatan model persebaran kematangan batuan induk (2D)
menggunakan lintasan seismik yang telah diinterpretasi. Hasil penelitian menunjukkan bahwa dari ketiga interval yang dilakukan analisis kualitas, kuantitas dan kematangan batuan induk, Interval PMT atau Ekuivalen Formasi Pematang merupakan Interval yang berperan sebagai batuan induk di daerah penelitian dengan nilai TOC berkisar 0,06-2,8 wt% yang tergolong (poor-very good) dengan rerata 0,8 wt% (fair). Batuan induk tersebut berasosiasi dengan kerogen tipe II dan III dan memiliki kematangan termal yang tergolong mature. Tingkat kematangan batuan induk interval PMT terdiri dari tiga tingkat kematangan yaitu belum matang (immature), awal minyak (early oil), dan puncak minyak (main oil). Batuan induk mulai memasuki jendela kematangan sejak 20,06 juta tahun yang lalu. Secara umum, sumur-sumur di daerah penelitian telah menyentuh tingkat kematangan awal minyak.
Sebaran kematangan batuan induk pada Sub-cekungan Pendalian memperlihatkan bahwa zona awal minyak (early oil) dimulai pada kedalaman 4500 ft pada wilayah barat daya, sedangkan zona puncak minyak (main oil) dimulai pada kedalaman 7500 ft dan hanya menyebar pada deposenter cekungan, zona belum matang (immature)berada pada wilayah utara-timur laut, kematangan batuan induk relatif berkurang saat mendekati tepi cekungan.===The Central Sumatra Basin is one of the hydrocarbon potential basins in Indonesia, the Pendalian sub-basin which is part of the Central Sumatra basin indicated to have fair to good ssource rock potential and has entered the phase of main oil in several area, but the research on the source rock has not been explored in details so it is interesting to study. This research was conducted to determine the quality and quantity of source rock in terms of geochemistry, and explain the maturity history as well as the distribution of source rock maturity in the Pendalian sub-basin. The data used includes geochemical data, well reports, log data, and paleontological data from six available wells. This research also used 14 line of seismic 2D. The method used in this study includes
geochemical data crossplot to identify the quality and quantity of source rock, and build the source rock maturity modeling (1D) by calibrating vitrinite reflectance data and Bottom Hole Temperature (BHT) data, and modelling the distribution of source rock
maturity (2D) using seismic section that has been interpreted. The results showed that from the three intervals that has been analyzed for the quality, quantity and maturity of the source rock, the PMT interval or Equivalent of Pematang Formation is a interval that acts as a source rock in the study area with a TOC value ranging from 0.06-2.8 wt% which is classified as (poor-very good) with an average of 0.8 wt% (fair). The source rock is associated with kerogen types II and III and has a relatively mature thermal maturity. The maturity level of source rock in this study area (interval PMT) consists of three maturity levels, which are immature, early oil, and main oil. The source rock entered the maturity window at 20.06 million years ago. In general, the wells in the study area have touched the early maturity level of oil. The distribution of source rock maturity in the Pendalian Sub-basin shows that the early oil zone starts at a depth of 4500 ft in the southwest region, while the main oil zone starts at a depth of 7500 ft and only spreads to
the depocenter area, the immature zone is in the north-northeast region, the maturity of the source rock is relatively decrease as it approaches the edge of the basin.
ABSTRACT
The Central Sumatra Basin is one of the hydrocarbon potential basins in Indonesia, the Pendalian sub-basin which is part of the Central Sumatra basin indicated to have fair to good ssource rock potential and has entered the phase of main oil in several area, but the research on the source rock has not been explored in details so it is interesting to study. This research was conducted to determine the quality and quantity of source rock in terms of geochemistry, and explain the maturity history as well as the distribution of source rock maturity in the Pendalian sub-basin. The data used includes geochemical data, well reports, log data, and paleontological data from six available wells. This research also used 14 line of seismic 2D. The method used in this study includes
geochemical data crossplot to identify the quality and quantity of source rock, and build the source rock maturity modeling (1D) by calibrating vitrinite reflectance data and Bottom Hole Temperature (BHT) data, and modelling the distribution of source rock
maturity (2D) using seismic section that has been interpreted. The results showed that from the three intervals that has been analyzed for the quality, quantity and maturity of the source rock, the PMT interval or Equivalent of Pematang Formation is a interval that acts as a source rock in the study area with a TOC value ranging from 0.06-2.8 wt% which is classified as (poor-very good) with an average of 0.8 wt% (fair). The source rock is associated with kerogen types II and III and has a relatively mature thermal maturity. The maturity level of source rock in this study area (interval PMT) consists of three maturity levels, which are immature, early oil, and main oil. The source rock entered the maturity window at 20.06 million years ago. In general, the wells in the study area have touched the early maturity level of oil. The distribution of source rock maturity in the Pendalian Sub-basin shows that the early oil zone starts at a depth of 4500 ft in the southwest region, while the main oil zone starts at a depth of 7500 ft and only spreads to
the depocenter area, the immature zone is in the north-northeast region, the maturity of the source rock is relatively decrease as it approaches the edge of the basin.
Subyek/Kata Kunci: Batuan Induk, Pemodelan Kematangan, Subcekungan Pendalian, Formasi Pematang
