SKRIPSI APLIKASI ATRIBUT SEISMIK DAN INVERSI ACOUSTIC IMPEDANCE (AI) UNTUK PREDIKSI PENYEBARAN RESERVOAR BATUPASIR PADA LAPANGAN “KANAKA” FORMASI BEKASAP CEKUNGAN SUMATERA TENGAH APPLICATION OF SEISMIC ATTRIBUTES AND ACOUSTIC IMPEDANCE (AI) INVERSION TO PREDICT OF SANDSTONE RESERVOAR ON KANAKA FIELD, BEKASAP FORMATION CENTRAL SUMATERA BASIN Diajukan sebagai salah satu syarat untuk memenuhi gelar Sarjana Strata Satu (S-1) Jurusan Teknik Geofisika, Fakultas Teknologi Mineral, Universitas Pembangunan Nasional “Veteran” Yogyakarta. Oleh : INDAH WIDYA PRATIWI 115 130 062 JURUSAN TEKNIK GEOFISIKA FAKULTAS TEKNOLOGI MINERAL UNIVERSITAS PEMBANGUNAN NASIONAL ”VETERAN” YOGYAKARTA 2018 ABSTRAK APLIKASI ATRIBUT SEISMIK DAN INVERSI ACOUSTIC IMPEDANCE (AI) UNTUK PREDIKSI PENYEBARAN RESERVOAR BATUPASIR PADA LAPANGAN “KANAKA” FORMASI BEKASAP CEKUNGAN SUMATRA TENGAH Indah Widya Pratiwi 115.130.062 Lapangan “Kanaka” merupakan lapangan produksi minyak dan gas bumi yang terletak pada cekungan Sumatera Tengah. Zona target hidrokarbon berada pada formasi Bekasap. Survei Geofisika menggunakan metode seismik refleksi dipercaya dapat memberikan informasi seputar distribusi reservor. Perpaduan antara atribut seismik dan inversi acoustic impedance (AI) efektif untuk dijadikan sebagai landasan dalam mengambil tindakan terhadap reservoar. Dari perpaduan tersebut akan diperoleh berupa peta persebaran reservoar batupasir berdasarkan analisa inversi Model Based dan analisa atribut seismik menggunakan atribut Envelope, Root Mean Square (RMS) dan Instantaneous Phase. Berdasarkan hasil pengolahan dan interpretasi dari penelitian lapangan “Kanaka”, maka didapatkan nilai impedansi akustik rendah sebesar 16.860 – 18.654 ((ft/s)*(g/cc)) yang diinterpretasikan sebagai batupasir dan impedansi akustik tinggi sebesar 18.654 – 20.300 ((ft/s)*(g/cc)) yang diinterpretasikan sebagai batulempung. Distribusi reservoar batupasir pada lapangan ini tersebar pada bagian Timur daerah telitian. Reservoar batupasir diperkirakan memiliki terbal reservoar ± 40 ft pada kedalaman sekitar 1930-1970 ft atau pada time 645 – 653 ms. Sumur eksplorasi diusulkan berada disekitar inline 459 xline 1674 atau pada koordinat X : 849555.41 Y: 72385.87, yang mengacu pada nilai inversi AI, inversi densitas, hasil analisis atribut seismik (Envelope, RMS dan Instantaneous Phase) serta peta time depth structure. Kata kunci : Penyebaran Reservoar, Atribut Seismik, Inversi Model Based. v ABSTRACT APPLICATION OF SEISMIC ATTRIBUTES AND ACOUSTIC IMPEDANCE (AI) INVERSION TO PREDICT OF SANDSTONE RESERVOAR ON KANAKA FIELD, BEKASAP FORMATION CENTRAL SUMATERA BASIN Indah Widya Pratiwi 115 130 062 “Kanaka” field is a production field of oil and gas located in Central Sumatera basin. This reserch will be discuss the distribution of sandstone reservoir in Bekasap formation. The combination of seismic attributes and acoustic impedance inversion (AI) are effective methode that can explain the distribution of reservoir. Analysis inversion of Model Based will be good at distribution of reservoir and analysis seismic attibutes (Envelope, Root Mean Square (RMS) and Instantaneous Phase) will be support the information of reservoir. Based on the results of processing and interpretation showed low acoustic impedance [16,860 - 18,654 ((ft / s) * (g / cc))] interpreted as sandstone and high acoustic impedance [18.654 - 20.300 ((ft / s) * (g / cc))] interpreted as claystone. The distribution of reservoir sandstones in this field is scattered in the eastern part of Kanaka’s area. This field is estimated to have a reservoir of ± 40 ft. A new well is proposed around inline 459 and xline 1674 or coordinates X: 849555.41 Y: 72385.87. The location of new well refers to the density inversion, AI inversion, seismic attribute analysis as well as the time depth structure map. Keywords : Distributions of Reservoir, Seismic Attributes, Model Based Inversion. vi DAFTAR ISI HALAMAN JUDUL .................................................................................... i HALAMAN PENGESAHAN ....................................................................... ii HALAMAN PERNYATAAN ...................................................................... iii KATA PENGANTAR .................................................................................. iv ABSTRAK .................................................................................................... v ABSTRACT ................................................................................................... vi DAFTAR ISI ................................................................................................ vii DAFTAR GAMBAR ..................................................................................... x DAFTAR TABEL ........................................................................................ xiii DAFTAR LAMPIRAN ................................................................................ xiv DAFTAR SINGKATAN DAN LAMBANG ................................................ xv BAB I. PENDAHULUAN 1.1. Latar Belakang ........................................................................................ 1 1.2. Rumusan Masalah. ................................................................................... 2 1.3. Maksud dan Tujuan ................................................................................. 2 1.4. Batasan Masalah ..................................................................................... 2 1.5. Lokasi dan Waktu Penelitian ................................................................... 3 BAB II. TINJAUAN PUSTAKA 2.1. Geologi Regional .................................................................................... 4 2.1.1. Tatanan Tektonik Cekungan Sumatra Tengah ........................... 4 2.1.2. Tektonostratigrafi Cekungan Sumatra Tengah ........................... 5 2.1.3. Kerangka Tektonik Cekungan Sumatra Tengah ........................ 10 2.1.4. Petroleum System ..................................................................... 14 2.2. Geologi Lokal Lapangan Kanaka ............................................................ 17 2.2.1. Struktur Lapangan Kanaka ........................................................ 17 2.2.2. Stratigrafi Lapangan Kanaka ..................................................... 18 2.2.3. Petroleum System Lapangan Kanaka .......................................... 19 2.3. Penelitian Terdahulu ............................................................................... 20 vii BAB III. DASAR TEORI 3.1. Seismik Refleksi ...................................................................................... 23 3.1.1. Penjalaran Gelombang Seismik ................................................. 24 3.2. Seismik Atribut ........................................................................................ 25 3.3. Seismik Inversi ........................................................................................ 30 3.3.1. Inversi Model Based .................................................................. 32 3.4.Well Logs .................................................................................................. 37 3.4.1. Log Listrik ................................................................................ 38 3.4.2. Log Radioaktif ........................................................................... 43 3.4.3. Log Akustik ............................................................................... 47 3.5. Kondisi Lubang Sumur ........................................................................... 50 3.6. Reservoar ................................................................................................ 52 3.6.1. Batuan Reservoar ....................................................................... 52 3.6.2. Batupasir ................................................................................... 53 3.6.3. Sifat Fisik Batuan Reservoar ...................................................... 54 BAB IV. METODOLOGI PENELITIAN 4.1. Tahapan Penelitian .................................................................................. 61 4.2. Data Penelitian ....................................................................................... 65 4.2.1. Data Seismik ............................................................................ 65 4.2.2. Data Sumur ................................................................................ 67 4.2.3. Data Horizon ............................................................................ 67 4.2.4. Data Marker ............................................................................. 69 4.2.5. Data Sesar ................................................................................. 69 BAB V. HASIL DAN PEMBAHASAN 5.1. Hasil ....................................................................................................... 71 5.1.1. Analisa Sumur ........................................................................... 71 5.1.2. Analisa Crossplot ...................................................................... 72 5.1.3. Analisa Tuning Thickness .......................................................... 76 5.1.4. Ekstraksi Wavelet dan Well Seismic Tie ..................................... 77 viii 5.1.5. Analisa Inversi Modelbased ....................................................... 79 5.1.6. Analisa Atributes Seismic........................................................... 82 5.2. Interpretasi ............................................................................................... 86 5.2.1. Interpretasi Geologi ................................................................. 86 5.2.2. Analisis Penyebaran Zona Hidrokarbon ................................... 89 5.2.3. Perencanaan Sumur Baru ........................................................... 91 BAB VI. KESIMPULAN DAN SARAN 6.1. Kesimpulan ............................................................................................. 95 6.2. Saran ....................................................................................................... 95 DAFTAR PUSTAKA LAMPIRAN ix DAFTAR GAMBAR Gambar 1.1. Peta Lokasi Lapangan Kanaka .................................................. 3 Gambar 2.1. Elemen Tektonik yang mempengaruhi Cekungan Sumatera Tengah (Heidrick dan Aulia, 1996) ........................... 4 Gambar 2.2. Kolom Stratigrafi Cekungan Sumatra Tengah (Heidrick dan Aulia, 1996) ....................................................................... 5 Gambar 2.3. Geologi Regional Sumatera (Pertamina BPPKA,1996) ............. 6 Gambar 2.4. Pola Struktur Regional Cekungan Sumatera Tengah (Pertamina BPPKA, 1996) ....................................................... 10 Gambar 2.5. Kerangka struktur geologi fase F2 dan F3 yang mempengaruhi struktur geologi pada cekungan Sumatra tengah (Heidrick & Turlington, 1997) ...................................... 12 Gambar 2.6. Perkembangan tektonostratigrafi Cekungan Sumatra Tengah (Heidrick dan Aulia, 1996)....................................................... 13 Gambar 2.7. Peta Geologi Lokal N.R. Camerun, S.A Ghazali, dan S.J Thomson ,1982) ....................................................................... 17 Gambar 2.8. Stratigrafi Lapangan Kanaka (BOB. PT Bumi Siak Pusako - Pertamina Hulu) ..................................................................... 18 Gambar 2.9. Hasil inversi Model Based sumur 1 (A) dan Time Maps Structure (B) (Fatkhurrochman, 2010). ..................................... 21 Gambar 2.10. Hasil P-wave section sumur 1 (A) dan Time Maps Structure (B) (Fatkhurrochman, 2010). ..................................... 22 Gambar 3.1. Konsep penjalaran gelombang seismik refleksi dari source ke Receiver (Subiyanto & Muhantoro, 2004) ............................ 23 Gambar 3.2. Pemantulan dan pembiasan pada bidang batas dua medium untuk gelombang P datang (Sheriff dan Geldart, 1995)............. 24 Gambar 3.3. Klasifikasi Atribut Seismik (Brown, 2000) ............................... 26 Gambar 3.4. Ilustrasi Atribut Envelope ......................................................... 27 Gambar 3.5. Ilustrasi penghitungan amplitudo RMS (Sukmono, 2007) ......... 28 Gambar 3.6. Hubungan antara tras amplitudo dengan tras Instantaneous Phase (Sukmono, 2007) ........................................................... 29 x