Identifikasi Persebaran Litologi Reservoar Batupasir Menggunakan Analisis Seismik Inversi Impedansi Elastik Di Lapangan Najlaa Formasi Cibulakan Cekungan Jawa Barat Utara

Telah dilakukan inversi terhadap data seismik PSTM 3D lapangan NAJLAA, Cekungan Jawa Barat Utara. Metode yang digunakan yaitu inversi impedansi elastik untuk mengidentifikasi pola penyebaran litologi dan fluida hidrokarbon dari reservoar batupasir di lapisan Z.2210 Formasi Cibulakan. Inversi AVO dilakukan untuk mendapatkan intercept, gradient, reflektivitas impedansi elastik, near angle stack dan far angle stack. Analisis grafik AVO dan atribut angle stack untuk mengetahui respon amplitudo terhadap offset digunakan untuk menentukan kelas anomali AVO. Dari hasil analisis sensitifitas menunjukan bahwa impedansi elastik dengan sudut 30o paling sensitif dalam pemisahan litologi batupasir dan serpih. Sehingga proses inversi impedansi elastik dengan sudut 30o terbukti paling sensitif dalam pemetaan penyebaran litologi. Selanjutnya dilakukan analisis crossplot antara log impedansi elastik sudut 30o terhadap log gamma ray untuk membedakan litologi batupasir dan crossplot antara log lambda-rho terhadap log gamma ray untuk menentukan adanya indikasi fluida hidrokarbon. Hasil analisis AVO menunjukkan bahwa respon pada lapisan Z.2210 termasuk dalam anomali AVO kelas IIp yang terletak pada twt 1794 ms sampai 1799 ms di sumur UI-10. Pemetaan inversi impedansi elastik dengan sudut 30o inline 1141 menunjukkan bahwa litologi batupasir zona target mempunyai nilai 1410 (m/s)2*gr/cc sampai 1570 (m/s)2*gr/cc dengan daerah penyebaran batupasir pada reservoar lapisan Z.2210 memiliki orientasi arah timur laut-barat daya. Kata kunci: Inversi; AVO; Impedansi Elasti

Investigasi Bidang Gelincir Pada Daerah Rawan Longsor Di Ruas Jalan Tawaeli-Toboli Menggunakan Metode Geolistrik Tahanan Jenis

Telah dilakukan penelitian investigasi bidang gelincir pada daerah rawan longsor dengan metode geolistrik tahanan jenis 2D di jalan Tawaeli – Toboli dengan menggunakan konfigurasi Wenner dengan panjang lintasan 96 m dan spasi antar elektroda 6 m yang dianalisis dengan software Res2Dinv.  Selanjutnya dapat ditentukan struktur dan litologi bawah permukaan sehingga dapat memberikan informasi mengenai bidang gelincir. Hasil dari penelitian ini menunjukkan bahwa penyusun tanah di daerah penelitian adalah kerikil, batu pasir, dan genes. Nilai hambatan jenis setiap lapisan batuan yaitu kerikil berkisar antara 10 Ωm – 84 Ωm, lapisan batu pasir berkisar antara 84 Ωm – 158 Ωm, dan lapisan genes berkisar antara 232 Ωm – 528 Ωm. Pada wilayah penelitian terdapat lapisan genes yang diduga merupakan bidang gelincir. Bentuk bidang gelincir yang diperoleh pada wilayah penelitian yaitu jenis gelincir rotasi dengan arah longsoran mengarah ke arah jalan raya dengan kedalaman 7 m – 35 m untuk semua lintasan. Investigation of the slip surface has been carried out in landslide-prone areas using the 2D resistivity geoelectric method on the Tawaeli-Toboli road using the Wenner configuration with 96 meters of track length, and 6 m of electrode spacing analyzed with Res2DinV software. Furthermore, the subsurface structure and lithology can be determined to provide information about the slip plane. This study's results indicate that the soil compilers in the study area are gravel, sandstone, and genes. The value of electrical resistivity of each rock layer, namely gravel ranges from 10 Ωm - 84 Ωm, sandstone layer covers from 84 Ωm - 158 Ωm, and the genes layer ranges from 232 Ωm - 528 Ωm. In the research area, there are layers of genes that are thought to be the slip plane. The shape of the sliding plane obtained in the study area is the rotating slip with landslide direction leading to the highway with a depth of 7 meter - 35 meter for all trajectories

Identifying Andesite Rocks Sources Using Geoelectrical Resistivity in Loli, Donggala Regency, Central Sulawesi

Research has been carried out in Loli Village, Donggala Regency, Central Sulawesi using the Wenner-Schlumberger resistivity geoelectric method to determine the resource of andesite rocks. This measurement was done by determining the path points in the field using the Global Positioning System (GPS). The data collection was carried out using the geoelectrical resistivity method based on the area’s measurement plan. The data obtained was in the form of position data for each electrode, potential data (V), and current strength data (I) used to calculate the resistivity value (r). The results obtained from this research are andesite rock resource content, which was characterized by a high resistivity value ranging from 300–600 Wm. The resistivity value of the cover layer is low, ranging from 14–45 Wm. The latent content of andesite rocks was dominated in the southeast region on the trajectory of DRSA_01, DRSA_02, DRSA_03, DRSA_04, and DRSA_06 which had a lower topography than the northwest region. DOI: http://dx.doi.org/10.17977/um024v4i22019p04

IDENTIFIKASI PERSEBARAN LITOLOGI RESERVOAR BATUPASIR MENGGUNAKAN ANALISIS SEISMIK INVERSI IMPEDANSI ELASTIK DI LAPANGAN NAJLAA FORMASI CIBULAKAN CEKUNGAN JAWA BARAT UTARA

Abstrak Telah dilakukan inversi terhadap data seismik PSTM 3D lapangan NAJLAA, Cekungan Jawa Barat Utara. Metode yang digunakan yaitu inversi impedansi elastik untuk mengidentifikasi pola penyebaran litologi dan fluida hidrokarbon dari reservoar batupasir di lapisan Z.2210 Formasi Cibulakan. Inversi AVO dilakukan untuk mendapatkan intercept, gradient, reflektivitas impedansi elastik, near angle stack dan far angle stack. Analisis grafik AVO dan atribut angle stack untuk mengetahui respon amplitudo terhadap offset digunakan untuk menentukan kelas anomali AVO. Dari hasil analisis sensitifitas menunjukan bahwa impedansi elastik dengan sudut 30o paling sensitif dalam pemisahan litologi batupasir dan serpih. Sehingga proses inversi impedansi elastik dengan sudut 30o terbukti paling sensitif dalam pemetaan penyebaran litologi. Selanjutnya dilakukan analisis crossplot antara log impedansi elastik sudut 30o terhadap log gamma ray untuk membedakan litologi batupasir dan crossplot antara log lambda-rho terhadap log gamma ray untuk menentukan adanya indikasi fluida hidrokarbon. Hasil analisis AVO menunjukkan bahwa respon pada lapisan Z.2210 termasuk dalam anomali AVO kelas IIp yang terletak pada twt 1794 ms sampai 1799 ms di sumur UI-10. Pemetaan inversi impedansi elastik dengan sudut 30o inline 1141 menunjukkan bahwa litologi batupasir zona target mempunyai nilai 1410 (m/s)2*gr/cc sampai 1570 (m/s)2*gr/cc dengan daerah penyebaran batupasir pada reservoar lapisan Z.2210 memiliki orientasi arah timur laut-barat daya. Kata kunci: Inversi; AVO; Impedansi Elastik Abstract An inversion has been carried out againts the seismic data of PSTM 3D at Najlaa field in the Northern West Java basin. The method used is elastic impedance to identify lithology and hidrocarbon distribution of sandstones reservoir in the layer of Cibulakan Formation, Z.2210. AVO inversion has been carried out to get intercept, gradient, elastic impedance reflectivity, near angle stack, and angle stack. The AVO graph analyzing and angle stack attribute are used to determine amplitude response of the offset used to determine AVO anomaly class. From the result of sensitivity analysis showed that elastic impedance has the most sensitivity in the separation of sandstones lithology and mudstones in the angle of 30 degree. It is approved in the mapping of lithology distribution. Further crossplot analysis has been carried out between elastic impedance log angle in 30 degree againts gamma ray log to distinguish sandstones lithology and crossplot between lambda-rho log to gamma ray log to determine the indication of hidrocarbon fluids. The result of AVO analysis showed the response in the layer Z.2210 included in IIp AVO anomaly located at twt 1794 ms to 1799 ms in UI-10 well logging. Elastic Impedance mapping 30 degree inline 1141 showed that target zone of sandstones lithology has a value of 1410 (m/s)2*gr/cc to 1570 (m/s)2*gr/cc with region spread of the sandstones distribution in reservoir layers Z.2210 which has an orientation toward Northeast-Southwest. Keywords:   Inversion; AVO; Elastic Impedanc

Studi Material Organik batuan Induk Sebagai Sumber Batuan Hidrokarbon Lapangan 'X' Berdasarkan Data Geokimia

The need for oil and gas has led to increased exploration to produce hydrocarbons in various basins and discover new reserves. This was also done in the Kutai basin on the eastern island of Kalimantan using a quantitative correlation between geophysical logs and rock core data and qualitative analysis by analyzing geochemical data derived from the host rock. To determine the characteristics of the hydrocarbon source rock in the three test wells, three types were analyzed, namely organic material richness, organic material type, and maturity level. For the Maau-1, Wahau-1, and Tengkawang-1 test wells, the organic material content has an excellent type to become source rock. The three wells are of medium-special hydrocarbon potential in organic material, making them very likely to produce oil and gas. As for the nature of the material content, the three wells have a mature level of the source rock, making them very potential as the  very good source rock. The need for oil and gas has led to increased exploration to produce hydrocarbons in various basins and discover new reserves. This was also done in the Kutai basin on the eastern island of Kalimantan using a quantitative correlation between geophysical logs and rock core data and qualitative analysis by analyzing geochemical data derived from the host rock. To determine the characteristics of the hydrocarbon source rock in the three test wells, three types were analyzed, namely organic material richness, organic material type, and maturity level. For the Maau-1, Wahau-1, and Tengkawang-1 test wells, the organic material content has an excellent type to become source rock. In terms of organic matter, all three wells have medium-special hydrocarbon potential and, therefore, high potential to produce oil and gas. As for the nature of the material content, the three wells have a mature level of the source rock, making them very potential as the very good source rock.

INVERSI IMPEDANSI ELASTIK DAN UNTUK KARAKTERISASI KANDUNGAN RESERVOIR BATUPASIR

Penelitian ini berupa analisis inversi data seismik dengan menggunakan impedansi elastik dan lr (lambda-rho) untuk mengestimasi kandungan  reservoir batupasir. Analisis Inversi Amplitude Versus Offset (AVO) dilakukan untuk mendapatkan reflektivitas impedansi elastik dan lambda-rho sehingga diperoleh kelas anomalinya. Dalam menentukan litologinya diperoleh sudut 30o sebagai sudut yang sensitif sehingga selanjutnya dilakukan proses inversi dengan sudut tersebut. Hasil dari analisis Anomali Inversi Amplitude Versus Offset (AVO) menetapkan kelas anomali respon terletak pada posisi IIp sehingga dengan menggunakan sudut 30o tersebut dilakukan pemetaan inversi impedansi elastik untuk mengetahui litologi batupasir yang diperkirakan mempunyai arah timurlaut-baratdaya. Selanjutnya untuk melakukan analisis untuk estimasi adanya fluida dengan menggunakan analisis inversi lambda-rho sehingga diperoleh nilai target 40-65 MPa*gr/cc pada litologi batupasir tersebut dengan arah orientasi utara-tenggara

ANALISIS SEISMOTEKTONIK UNTUK PENANGGULANGAN DAERAH RAWAN BENCANA GEMPA BUMI

Tana Toraja located in the compression belt of two active fault seismic source zones. There are Palu- Koro and the Walanai faults have resulted the eastward, movement of the Banggai-Sula micro continent since neogen time. The field observations of the neotectonic holosen age were  found as the river deposit and beachsand terraces and the fault  fan structure where there  are consist of three teracces units  which the maximum high of  the oldest terrace (±100.000 years)  about of 12 m and the minimum about of  7 m. Base on the differences high of the maximum terrace  units in the Salu Sadang and Rongkong rivers, so  the maximum magnitude earthquake displacement (md) can be calculated at every fault segments. The evaluation of geological structures and earthquake data, this region can be devided  into four seismic source zones there are the salu sadang, The  Buttu Karoa-Lamasi Sabang  active faults, the old volcano tectonic earthquakes of the Buttu-Karoa-Kalumpang Mamuju and the volcano tectonic earthquakes of the Limbong Seismic Zource Zone. Base on tne neotectonic condition and the existing of seismic source zones above, Tana Toraja and surrounding area is one of the potential seismic hazard area in the South Sulawesi region which must be have more attention

Tingkat Karakteristik Batuan Induk Sebagai Sumber Kandungan Minyak dan Gas Bumi : Studi Kasus Cekungan Lariang-Karama-Sulawesi Barat

The need for oil and gas is increasing. This increases exploration and exploitation activities in oil and gas through production by searching for new reserves or developing old fields. This research was conducted in western Sulawesi, Lariang Basin in the Kalumpang Formation, Budung-Budung Formation, Lisu Formation and Pasang Kayu Formation, which is dominated by massive sedimentary basins. This research was conducted with quantitative and qualitative analyses of geophysical log data with rock data and correlation between geochemical data and data from source rocks. Source rock characterization was carried out by analyzing organic material content, organic material type and maturity level. The three test wells were analyzed so that it can be interpreted that the organic material content does not have good potential as a source rock with the type of organic material in the medium category that produces gas but is not effective, so the maturity level is obtained immature which does not have good potential as an effective source rock but can produce oil and gas in small quantities