Perbandingan Kecepatan Sonic dan Kecepatan Interval dalam Prediksi 3D Tekanan Pori Menggunakan Metode Eaton pada Lapangan "AZK", Sub Cekungan Palembang Selatan, Cekungan Sumatera Selatan
IRCHASH AZKIA MAKNUNA, Dr. Sudarmaji, S.Si., M.Si ; Dimas Pramudito, S.T., M.T
2024 | Skripsi | GEOFISIKA
Industri migas
terus menghadapi banyak tantangan dalam proses eksplorasi, salah satunya
kejadian sejarah ledakan pada anjungan pengeboran minyak Deep Water Horizon di
Teluk Meksiko yang disebabkan adanya kegagalan well-control dan
kesalahan pengeboran sehingga terjadi blowout. Salah satu penyebab
terjadinya kesalahan pengeboran adalah overpressure yang terjadi ketika
tekanan fluida pada pori batuan lebih besar dari tekanan normal. Pada
penelitian ini dilakukan perhitungan tekanan pori dan penentuan zona overpressure
di Lapangan “AZK”, Sub-cekungan Palembang Selatan, Cekungan Sumatera
Selatan dengan membandingkan dua nilai kecepatan yaitu kecepatan sonic
dan kecepatan interval. Hasil tekanan pori selanjutnya dimodelkan melalui
pemodelan 1D dan pemodelan 3D, dilakukan juga inversi impedansi akustik
dengan metode inversi model based. Metode yang digunakan pada penelitian
ini adalah Metode Eaton dengan fokus zona penelitan pada Formasi Baturaja
hingga Formasi Talang Akar. Zona overpressure ditemukan
pada bagian bawah Formasi Talang Akar di kedalaman 2200 – 2500 m dengan nilai
tekanan pori berdasarkan kecepatan sonic sebesar 3952.4 – 5007.5 Psi dan
berdasarkan kecepatan interval sebesar 4038 – 5920.1 Psi. Mekanisme penyebab overpressure
di bagian bawah talang akar tergolong dalam mekanisme loading dan mekanisme
unloading. Mekanisme loading terjadi akibat ketidakseimbangan
kompaksi batuan (disequilibrium compaction) sedangkan mekanisme unloading
disebabkan adanya perubahan mineral lempung (smektit menjadi illit. Kedua
mekanisme ini menyebabkan fenomena perpindahan overpressure (Lateral
Reservoir Drainage). Perbandingan data kecepatan menghasilkan penggunaan
kecepatan interval dianggap lebih efisien dan murah daripada penggunaan
kecepatan sonic baik dalam proses pemodelan, perhitungan, maupun analisis zona overpressure.
The oil and gas
industry continues to face many challenges in the exploration process, one of
which is the historical explosion on the Deep Water Horizon oil drilling
platform in the Gulf of Mexico which was caused by well-control failures and
drilling errors resulting in a blowout. One of the causes of drilling errors is
overpressure which occurs when the fluid pressure in the rock pores is greater
than normal pressure. In this research, pore pressure calculations and
overpressure zone determination were carried out in the "AZK" Field,
South Palembang Sub-basin, South Sumatra Basin by comparing two velocity
values, namely sonic velocity and interval velocity. The pore pressure results
were then modeled through 1D modeling and 3D modeling, and acoustic impedance
inversion was also carried out using a model based inversion method. The method
used in this research is the Eaton Method with a research zone focus on the
Baturaja Formation to the Talang Akar Formation. The overpressure zone was
found at the bottom of the Talang Akar Formation at a depth of 2200 – 2500 m
with a pore pressure value based on sonic velocity of 3952.4 – 5007.5 Psi and
based on interval velocity of 4038 – 5920.1 Psi. The mechanisms that cause
overpressure at the bottom of the root gutter are classified as loading
mechanisms and unloading mechanisms. The loading mechanism occurs due to an
imbalance in rock compaction (disequilibrium compaction) while the unloading
mechanism is caused by a change in clay minerals (smectite to illite. Both of
these mechanisms cause the phenomenon of overpressure displacement (Lateral
Reservoir Drainage). Comparison of velocity data results in the use of interval
velocity being considered more effective and cheaper than the use of sonic velocity
in the modeling process, calculations and analysis of overpressure zones.
Kata Kunci : Tekanan pori, Overpressure, Kecepatan Sonic. Kecepatan Interval