INTEGRASI KARAKTERISASI RESERVOAR DAN EVALUASI SENSITIVITAS GAS INJEKSI UNTUK OPTIMASI CO2 – EOR PADA RESERVOAR FORMASI TIRRAWARRA, CEKUNGAN COOPER, AUSTRALIA SELATAN

M. Muaffa Oktadiansyah, Dr. Ir. Sarju Winardi, S.T., M.T.; Ir. Rahmadi Hidayat, S.T., M.Eng., Ph.D., IPP.

2026 | Skripsi | TEKNIK GEOLOGI

Penelitian ini bertujuan untuk mengintegrasikan karakterisasi reservoar dan analisis termodinamika fluida guna mengoptimalkan penerapan Carbon Dioxide Enhanced Oil Recovery (CO₂-EOR) di Formasi Tirrawarra, Cekungan Cooper. Objektif utama mencakup identifikasi zona prospektif berbasis petrofisika, evaluasi ambang batas impuritas metana (C₁) dan nitrogen (N₂) terhadap Minimum Miscibility Pressure (MMP), serta kuantifikasi Recovery Factor (RF) melalui simulasi dinamis. 

Karakterisasi reservoir mencakup penentuan litofasies, hingga parameter petrofisika dan analisis cut-off petrofisika untuk menentukan interval net pay. Pemodelan fasa fluida menggunakan Peng-Robinson Equation of State (PR-EoS) yang dikalibrasi terhadap data laboratorium melalui simulator CMG WinProp untuk menganalisis misibilitas Multiple-Contact. Model dinamis radial 3D per-interval reservoir dibangun dalam CMG GEM untuk menyimulasikan skenario produksi primer, deplesi lanjutan, dan injeksi Huff-n-Puff dengan variasi komposisi impuritas. 

Hasil analisis petrofisika menetapkan cut-off Vsh ? 0,35, ?_e ? 0,08, dan S_w ? 0,50, dengan Unit A dan C teridentifikasi sebagai zona prospektif utama. Pemodelan PVT menghasilkan MMP baseline CO₂ murni sebesar 2.694,7 psia. Keberadaan impuritas meningkatkan MMP dengan batas toleransi maksimum sebesar 25% untuk C₁ dan 10% untuk N₂ agar tekanan misibilitas tetap berada di bawah tekanan reservoir terdeplesi sebesar 3.123,65 psia. Hasil simulasi dinamis menunjukkan bahwa injeksi misibel CO₂ murni secara komputasional mampu meningkatkan RF hingga 42,61%, melonjak signifikan dibandingkan primary recovery yang hanya mencapai 14,86%. Sebaliknya, impuritas N₂ berlebih memicu pendesakan immiscible yang secara drastis menurunkan efisiensi penyapuan.  

This study aims to integrate reservoir characterization and fluid thermodynamic analysis to optimize the implementation of Carbon Dioxide Enhanced Oil Recovery (CO?-EOR) in the Tirrawarra Formation, Cooper Basin. The main objectives include identifying petrophysically based prospective zones, evaluating the threshold limits of methane (C?) and nitrogen (N?) impurities on Minimum Miscibility Pressure (MMP), and quantifying the Recovery Factor (RF) through dynamic simulation.

Reservoir characterization included lithofacies determination, petrophysical evaluation, and petrophysical cut-off analysis to define net pay intervals. Fluid phase behavior was modeled using the Peng–Robinson Equation of State (PR-EoS), which was calibrated against laboratory data using the CMG WinProp simulator to evaluate multiple-contact miscibility. A three-dimensional radial dynamic model for each reservoir interval was subsequently developed in CMG GEM to simulate primary production, extended depletion, and Huff-n-Puff injection scenarios with varying impurity compositions.

The petrophysical analysis established cut-off values of Vsh ? 0.35, ?e ? 0.08, and Sw ? 0.50, with Units A and C identified as the primary prospective zones. PVT modeling yielded a baseline MMP of 2,694.7 psia for pure CO? injection. The presence of impurities increased the MMP, with maximum tolerance limits of 25% for C? and 10% for N? to maintain miscibility pressure below the depleted reservoir pressure of 3,123.65 psia. Dynamic simulation results demonstrated that miscible pure CO? injection increased the RF to 42.61%, representing a substantial improvement compared to the primary recovery RF of 14.86%. In contrast, excessive N? impurities promoted immiscible displacement, significantly reducing sweep efficiency.

Kata Kunci : Formasi Tirrawarra, Petrofisika, CO2-EOR, Minimum Miscibility Pressure, Recovery Factor.