ANALISIS PETROFISIKA UNTUK EVALUASI RESERVOIR DAN ESTIMASI AKUMULASI HIDROKARBON BATUPASIR "X", FORMASI NGRAYONG ATAS, LAPANGAN "MARTIAL", CEKUNGAN JAWA TIMUR UTARA
DICKY ADITYA Y Y, Dr. Eddy Hartantyo, S.Si., M.Si
2016 | Skripsi | S1 GEOFISIKALapangan "MARTIAL" yang merupakan daerah penelitian berada di daerah Cepu, Cekungan Jawa Timur Utara. Lapangan tersebut telah menghasilkan hidrokarbon dengan reservoir utama batuan karbonat di Formasi Kujung. Namun, berdasarkan data mudlog terdapat oil show pada interval di atas reservoir utama yakni pada Formasi Ngrayong atas dengan litologi batupasir "X". Berdasarkan informasi tersebut, batupasir "X" di Formasi Ngrayong berpotensi menjadi reservoir. Oleh karena itu perlu dilakukan analisis petrofisika dan interpretasi seismik pada interval batupasir Formasi Ngrayong. Analisis petrofisika dilakukan dengan menggunakan 6 data sumur. Berdasarkan analisis sumur diketahui bahwa zona reservoir terbagi menjadi 4 zona yaitu sand-1, sand-2, sand-3, dan sand-4. Analisis tersebut meliputi perhitungan kandungan serpih, porositas efektif, permeabilitas, saturasi air serta lumping untuk menentukan zona hidrokarbon dan akumulasi hidrokarbon. Interpretasi seismik dilakukan dengan menggunakan data seismik 3D Post Stack Time Migration. Untuk mendapatkan peta ketebalan (isopach) yang akan digunakan untuk menentukan arah pengendapan dan geometri batupasir "X". Peta ketebalan (isopach) menunjukan arah pengendapan yakni utara - selatan dengan geometri yang terbentuk berupa channel bar. Hasil deterministik menunjukan nilai volume serpih rata-rata 64 %, porositas efektif 6 %, saturasi air 70 %, dan permeabilitas 2,56 mD dengan kualitas reservoir di batupasir X tergolong buruk dan bersifat ketat (tight). Berdasarkan peta net reservoir, net to gross, dan net pay, akumulasi hidrokarbon diperkirakan berada di daerah barat dan timur daerah penelitian.
"MARTIAL"field which is the research region, is located at Cepu, North East Java Basin. That field has produced hydrocarbon with build carbonate as main reservoir at Kujung Formation. However, based on mudlog information, there is an oil show at the interval of the top of main reservoir which is in top Ngrayong Formation with sandstone lithology "X". Based on that information, the sandstone "X" in Ngrayong Formation is potentially become a reservoir. Therefore, it is necessary to evaluate Ngrayong Formation's sandstone interval with petrophysical analysis and seismic interpretation. Petrophysical analysis is done by using 6 well data. Based on well analysis it is known that the reservoir zone is splitted into 4 zone, which are sand-1, sand-2, sand-3, sand-4. That petrophysical analysis consist of shale volume calculation, effective porosity, permeability, water saturation and lumping to determine hydrocarbon zone and hydrocarbon accumulation. Seismic interpretation is done by using 3D Post Stack Time Migration to produced thickness (isopach) map which is used to determine sedimentation flow and reservoir geometry of sandstone "X". Isopach map shows the direction of sedimentation flow which is from north to south with geometry that is formed in the form of channel bar. Deterministic result shows that average shale volume is 64%, effective porosity 6%, water saturation 70%, and permeability 2,56 mD, with reservoir sandstone "X" quality is categorized as poor and tight. Based on net reservoir, net to gross, and net pay map, hydrocarbon accumulation is estimated at west and east of research area.
Kata Kunci : Kata kunci : petrofisika, interpretasi seismik, peta ketebalan (isopach), gross, net reservoir, net to gross, net pay, akumulasi hidrokarbon
