Situs Semburan Lusi
Geophysical Research Abstracts Vol. 20, EGU2018-2125, 2018 EGU General Assembly 2018 © Author(s) 2017.
Suatu tinjauan dari laporan pemboran sumur Banjarpanji-1 dan kegempaan Indonesia untuk mengkaji hipotesis tentang pemicu semburan Lusi
A review of drilling reports from the Banjarpanji-1 well and Indonesian seismicity to assess hypotheses about the trigger of the Lusi eruption
Mark Tingay (1), Michael Manga (2), Max Rudolph (3), and Richard Davies (4)
(2) University of California, Berkeley, Berkeley, United States
(1) University of Adelaide, (3) University of California, Davis,
(4) Newcastle University
Ditinjau Oleh: Dr. Hardi Prasetyo
Sciences Manager, Misi Nasional Penanggulangan Bencana LUSI
2006-2017, Kerjasama BPLS-LUSI LAB
Abstrak
Penyebab semburan lumpur Lusi (The cause of the Lusi mud eruption) masih tetap menjadi hal yang kontroversial (remains controversial).
Salah satu hipotesis adalah bahwa semburan Lusi dipicu oleh gempabumi dengan intensitas M 6,3 di selatan Yogyakarta, berjarak 254 km dari Situs Lusi (the eruption was triggered by the M6.3 Yogyakarta earthquake some 254 km away). Hipotesis kedua adalah bahwa semburan Lusi tersebut disebabkan oleh pengeboran.
Pada makalah ini ditinjau data pengeboran dan laporan pengeboran harian (We review drilling data and the daily drilling reports).
Dimana dengan jelas telah dapat mengkonfirmasikan bahwa lubang sumur sudah tidak utuh (which clearly confirm that the wellbore was not intact), dan bahwa telah terjadi suatu ledakan di bawah permukaan (there was a subsurface blowout).
Data tekanan ke bawah lubang dari Lusi (Downhole pressure data from Lusi) langsung dapat menyaksikan kelahiran Lusi di permukaan pada tanggal 29 Mei 2006 (directly witness the birth of Lusi at the surface on the 29th of May 2006).
Dimana menunjukkan bahwa adanya hubungan langsung (indicating a direct connection) antara sumur dan semburanj Lusi (between the well and the eruption).
Selanjutnya, laporan pengeboran harian secara khusus juga menyatakan (the daily drilling reports specifically state) bahwa aktivitas Lusi terlihat berubah (that Lusi activity was visibly altered) dalam tiga kesempatan terpisah (on three separate occasions).
Dalam upaya mencoba menghentikan semburan (by attempts to kill the eruption) dengan memompa cairan padat ke sumur BJP-1 (by pumping dense fluid down the BJP-1 well).
Hal ini memberikan bukti lebih lanjut tentang adanya hubungan antara sumur bor dan Lusi (providing further evidence of a connection between the wellbore and Lusi).
Dibandingkan dengan contoh lain dari semburan lumpur yang baru terjadi di tempat lain oleh gempa bumi lainnya, gempa Yogyakarta jauh memberikan kekuatannya (the Yogyakarta earthquake was far away given its magnitude).
Kerapatan energi seismik (the seismic energy density) gempa Yogyakarta hanya 0,0043 J/m3, dimana berada kurang seperempat dari kepadatan energi seismik minimum 0,019 J/m3. Yang pernah disimpulkan telah memicu semburan lumpur baru di tempat lain (that has ever been inferred to trigger new mud eruptions elsewhere).
Kami menunjukkan bahwa wilayah Lusi sebelumnya pernah mengalami gempa dangkal lainnya (the Lusi area had previously experienced other shallow earthquake) dengan frekuensi yang sama dan goyangan tanah yang kuat (similar frequencies and stronger ground shaking), namun tidak memicu semburan (that did not trigger an eruption).
Akhirnya, data dari sumur BJP-1 menunjukkan bahwa tidak ada hubungan hidrodinamika sebelumnya (the data from the BJP-1 well indicates that there was no prior hydrodynamic connection) antara cairan hidrotermal berkedudukan dalam yang mengalami tekanan berlebih dan lempung Kalibeng dangkal (deep overpressured hydrothermal fluids and the shallow Kalibeng clays).
Disamping itu tidak ada bukti terjadinya pencairan atau pergerakan dari lempung Kalibeng yang disebabkan oleh gempa tersebut (there was no evidence of any liquefaction or remobilization of the Kalibeng clays induced by the earthquake).
Karena itu penulis menyatakan lebih favorit terhadap inisiasi Semburan Lusi oleh pengeboran dan bukan oleh gempa (We thus strongly favor initiation by drilling and not an earthquake)
ABSTRACT
The cause of the Lusi mud eruption remains controversial.
One hypothesis is that the eruption was triggered by the M6.3 Yogyakarta earthquake some 254 km away.
The second is that the eruption was caused by drilling.
We review drilling data and the daily drilling reports, which clearly confirm that the wellbore was not intact and that there was a subsurface blowout.
Downhole pressure data from Lusi directly witness the birth of Lusi at the surface on the 29th of May 2006, indicating a direct connection between the well and the eruption.
Furthermore, the daily drilling reports specifically state that Lusi activity was visibly altered on three separate occasions by attempts to kill the eruption by pumping dense fluid down the BJP-1 well, providing further evidence of a connection between the wellbore and Lusi.
By comparison with other examples of newly initiated mud eruptions elsewhere by other earthquakes, the Yogyakarta earthquake was far away given its magnitude.
The seismic energy density of the Yogyakarta earthquake was only 0.0043 J/m3, which is less than a quarter of the minimum 0.019 J/m3 seismic energy density that has ever been inferred to trigger new mud eruptions elsewhere.
We show that the Lusi area had previously experienced other shallow earthquakes with similar frequencies and stronger ground shaking that did not trigger an eruption.
Finally, the data from the BJP-1 well indicates that there was no prior hydrodynamic connection between deep overpressured hydrothermal fluids and the shallow Kalibeng clays, and that there was no evidence of any liquefaction or remobilization of the Kalibeng clays induced by the earthquake.
We thus strongly favor initiation by drilling and not an earthquake.
