Analisis Selisih Atribut Seismik Kompleks pada pengolahan data Seismik 4 dimensi untuk Steamflood monitoring di area 'TB-1878' PT. Caltex Pasific Indonesia

Abstract

Analisis Seismik 4D telah dilakukan pada data -Monitor I (Repro), Monitor 1 dan Monitor 2, yakni data Seismik 3D area 'TB-1878' setelah 8 dan 16 bulan dilakukan steamflooding, dengan cara menentukan selisih-waktu, selisih¬fase dan selisih-amplitudo masing-masing data tersebut terhadap Baseline, yakni data Seismik 3D area 'TB-1878' sebelum dilakukannya steamflooding. Dengan dibantu software Promax Chevronized 40, analisis Seismik 4D ini bertujuan mernantau perkembangan lateral steamflood berdasarkan anomali atribut seism ik yang diakibatkannya. Metode crosscorrelation dan penghitungan selisih-akar purata reflection strength diterapkan pada dua interval window masing-masing data yakni reference window, yang ditentukan pada fonnasi batuan-batuan non-reservoar non-target steamflooding, dan target window, yang ditentukan di formasi batuan reservoar target steamflooding. Hasil analisis pada reference window dijadikan korek.si bagi target window untuk meminimalkan faktor penyebab anomali atribut non-steamflood. Dari basil analisis Seismik 4D, ditunjukkan bahwa pada reference window, selisih-waktu, selisih-fase dan selisih-amplitudo. tidak rnenampakkan anomali di zona inj,eksi steamflood namun ditemukan koreksi yang cukup lugs pada Monitor I (Repro).— Baseline. Pada target window, masing-masing selisih-atribut menunjukkan anomali yang signifikan di zona injeksi-steanOood. Selisih-fase memperlihatkan anomali yang lebih optimal dibandingkan selisih-waktu, tetapi selisih-amplitudo memperlihatkan anomali yang paling optimal di antara ketiga selisih-atribut itu. Berdasarka.n perkembangan pola anomali yang dapat dikorelasikan dengan perkembangan sapuan lateral steamfrood, didapatkan rerata kecepatan .ekspansi lateral sumur injeksi islet/it/flood sebesar 4,3() meteribulan. Dengan demikian diperoleh perkembangan yang positif yaitu makin lama durasi stcamfloocling make makin leas zona yang akan tersapn olch weevil/100d. 4D Seismic analysis has been conducted to Monitor l (Repro), Monitor I. and Monitor 2 data, which are the 3D Seismic data of `TB-1878' area after 8 and 16 months been steam-flooded continuously, by determining the time-difference, phase-difference, and amplitude-difference of each data versus Baseline, which is a 3D Seismic data of `TB-1878' area before steamflooding. By the support of Promax Chevronized 4D software, the 4D Seismic analysis has the purpose to monitor the lateral expansion based on the seismic attribute anomaly that was resulted in. The cross-correlation method and the calculation of root mean square-difference of reflection strength was computed into two interval windows of each data that is the reference window, which was picked at non-reservoir rocks formation as the non-steam-flooded formation, and the target window, which was picked at reservoir rocks formation as the steam-flooded formation. The analysis result at the reference window become the correction for the target window to minimize the attribute anomaly caused by non-steamflood factor. From the 4D Seismic analysis result, it was showed that in the reference window, the time-difference, the phase-difference, and the amplitude-difference didn't exhibit anomaly at the steam flood injection zone but some large corrections exist in Monitor 1 (Repro)-Baseline. In the target window, each attribute-difference exhibits significance anomaly at the steamflood injection zone. The phase-difference displays more optimum, anomaly rather than the time-difference but the amplitude-difference displays the most optimum among those three attribute-differences. Based on the anomaly pattern development that can be correlated with the steamflood lateral swept, the averaged lateral expansion rate was obtained of 4,30 metres/month. Hence, a positive develOpment was obtained that is the longer duration of the steamflooding the wider the,zone that would had been swept by the steamflood.