Pemodelan Fasies 3D Interval ‘KF’ dan ‘SN’ Formasi Talang Akar Lapangan ‘Vein’ Cekungan Jawa Barat Utara

Kevin Fernando Sulistyo Nugroho, Ir. Moch. Indra Novian, S.T., M.Eng. IPP. ; Ir. Salahuddin Husein, S.T., M.Sc., Ph.D., IPM.

2026 | Skripsi | TEKNIK GEOLOGI

Lapangan "Vein" yang terletak di Subcekungan Arjuna Tengah Cekungan Jawa Barat Utara telah beroperasi sejak tahun 1984 dengan reservoir utama berupa batupasir interval ‘KF’ dan ‘SN’ dari Formasi Upper Talang Akar. Pada awal pengembangannya, kedua interval ini mencatatkan laju produksi awal (initial production rate) sebesar 8.042 BOPD minyak dan 215,5 MMSCFD gas, serta mencapai puncak produksi pada tahun 1994 dengan laju 7.440 BOPD dan 20.635 MMSCFD. Tetapi, pasca puncak produksi, lapangan ini mengalami tren penurunan yang signifikan hingga menyisakan produksi sebesar 135 BOPD minyak dan 2 MMSCFD gas per tahun 2026. Penurunan produksi secara drastis ini diindikasikan akibat kompleksnya distribusi dan heterogenitas batupasir reservoir yang terendapkan pada lingkungan transisi. Penelitian ini bertujuan untuk mengidentifikasi fasies, asosiasi fasies, dan lingkungan pengendapan, serta memetakan sebarannya secara spasial melalui pemodelan 3D. Penelitian ini mengintegrasikan data core dari sumur KF-2 dan K-9, 23 data log sumur, peta impedansi akustik, serta data dipmeter. Seluruh data diolah melalui analisis litofasies, elektrofasies, , dan marker stratigrafi untuk menentukan asosiasi fasies dan lingkungan pengendapan interval penelitian. Hasil integrasi kemudian dimodelkan menggunakan perangkat lunak Petrel 2020 menggunakan metode Truncated Gaussian Simulation (TGS). Hasil analisis menunjukan bahwa interval ‘KF’ dan ‘SN’ terendapkan di lingkungan lower delta plain dengan asosiasi fasies distributary channel (tersusun atas litofasies batupasir planar cross-lamination dan batupasir horizontal laminaton), interdistributary bay (tersusun atas litofasies batupasir ripple, batupasir flaser, batulanau laminasi, batulanau teroksidasi, batubara, dan batugamping), crevasse splay (tersusun atas litofasies batupasir), dan tidal channel (tersusun atas litofasies batupasir dan batulanau). Keseluruhan asosiasi fasies menunjukan tren pengendapan dari utara – timur laut menuju selatan – barat daya. Secara lateral, fasies distributary channel yang bertindak sebagai reservoir utama menunjukkan tren penyebaran yang semakin menebal dan melebar ke arah Selatan. Adapun secara vertikal, fasies distributary channel mengalami perubahan transisi menjadi interdistributary bay akibat adanya pengaruh marine yang semakin dominan (transgressive trend). Model 3D fasies yang terbentuk mampu menggambarkan kompleksitas reservoir lingkungan transisi delta dan dapat digunakan sebagai bahan pemodelan lanjutan yang dapat dijadikan sebagai acuan pengembangan lapangan di Lapangan ‘Vein’. 

The ‘Vein’ Field, located in the Arjuna Sub-basin of the North West Java Basin, has been operated since 1984, with primary reservoirs consisting of sandstone within the 'KF' and 'SN' intervals of the Upper Talang Akar Formation. During early development, these two intervals recorded an initial production rate of 8,042 BOPD of oil and 215.5 MMSCFD of gas, reached its peak production in 1994 at 7,440 BOPD and 20.635 MMSCFD. However, post peak production, the field experienced a significant decline, leaving a production rate of 135 BOPD of oil and 2 MMSCFD of gas as of 2026. This sharp production decline is indicated to be driven by the complex distribution and heterogeneity of the reservoir sandstones deposited in a transitional environment. This study aims to identify the facies, facies associations, and depositional environments, as well as to map their spatial distribution through 3D modeling. This study integrates core data from wells KF-2 and K 9, 23 well log data, acoustic impedance map, and dipmeter data. All data were processed through lithofacies analysis, electrofacies analysis, and stratigraphic markers to determine facies associations and the depositional environment of the study interval. The integrated results then modeled using Petrel 2020 software employing the Truncated Gaussian Simulation method. The analysis shows that the 'KF' and 'SN' intervals were deposited in a lower delta plain environment with facies associations comprising distributary channel (composed of planar cross-laminated sandstone and horizontally laminated sandstone lithofacies), interdistributary bay (composed of ripple sandstone, flaser sandstone, laminated siltstone, oxidized siltstone, coal, and limestone lithofacies), crevasse splay (composed of sandstone lithofacies), and tidal channel (composed of sandstone and siltstone lithofacies). The overall facies associations display a depositional trend oriented from North – Northeast toward South – Southwest. Laterally, the distributary channel facies, acting as the primary reservoir, exhibits a thickening and widening trend toward the South. Vertically, the distributary channel facies undergoes a transitional shift into interdistributary bay driven by increasingly dominant marine influence (transgressive trend). The resulting 3D facies model effectively captures the complexity of deltaic transitional reservoirs and can serve as a foundation for further modeling to guide field development strategies in the ‘Vein’ Field. 

Kata Kunci : Pemodelan Fasies 3D, Upper Talang Akar, distributary channel, Cekungan Jawa Barat Utara, delta