[iagi-net-l] Overpressure in Indonesia's sedimentary basins
Mas Bowo dan Ferdi, Thread-nya saya ubah jadi ‘overpressure in Indonesia’s sedimentary basins’ ya, sekalian promosi riset kami nih, hehehe. Mengenai overpressure di Lower Kutai Basin (LKB), ini kami kirimkan abstract dari paper kami yang akan diterbitkan kira-kira September ini di AAPG Bulletin. Sebagai acknowledgement, penulisan paper ini (termasuk PhD studentship saya), disponsori oleh Total E&P Indonesie: Terima kasih! Overpressure and shale compaction in the Lower Kutai Basin, Indonesia – a radical reappraisal Agus M. Ramdhan1* and Neil R. Goulty1 1Department of Earth Sciences, Durham University, South Road, Durham DH1 3LE, UK. *Present address: Department of Geology, Institut Teknologi Bandung, Jl. Ganesha 10, Bandung 40132, Indonesia. Corresponding author (e-mail: agu...@gc.itb.ac.id) ABSTRACT Lateral drainage and high temperatures in the shelfal area of the Lower Kutai Basin provide an exceptional opportunity to study compaction of Miocene shales and overpressure generation. Previous workers agreed that the principal mechanism of overpressure generation is disequilibrium compaction, but sonic and resistivity logs in several fields display reversals at a transition zone into high overpressure, indicating that overpressure is generated by unloading processes. The transition zone coincides with the vitrinite reflectance threshold for gas generation. Extreme overpressures in some wells are associated with reversals on density logs too, interpreted to result from cracks opening. The density–depth trends through the shales are similar in all wells and independent of overpressure until extreme overpressures are encountered. This observation strongly suggests that porosity reduction is controlled by chemical compaction and that cementation has caused the shales to become overcompacted, relative to the prevailing effective stress, at burial depths of ~3 km where the top of overpressure is encountered. Hence, the Lower Kutai Basin contains a unique reported example, to date, of a Neogene succession in which high overpressures are generated by unloading processes with no contribution from disequilibrium compaction. Density logs from the Peciko Field have been used to derive the empirical porosity–depth trend for shales in the depth range 6000–15,000 ft (1800–4600 m), where z is depth in thousands of feet. The corresponding temperatures range is 85–170°C, so this compaction curve applies for shales in the chemical compaction regime where no discrete smectite is present. Intinya memang kira-kira bahwa overpressure di LKB tidak disebabkan oleh undercompaction atau disequilibrium compaction (atau kita bisa sebut loading mechanism karena berhubungan dengan penambahan vertical load/sedimentation). Kami menduga penyebabnya adalah unloading (un-related-to loading). Kesimpulan kami ini cukup mengejutkan banyak peneliti yang mendalami overpressure. Mereka bertanya: “how come? You have ‘young’ sedimentary basin, undergoing moderate sedimentation rate, yet the overpressure is not caused by disequilibrium compaction?” Kami jawab, ya memang kami tidak menemukan sama sekali bukti disequilibrium compaction (porosity preservation at overpressure section). Malahan, kami menemukan bahwa sedimen di overpressured section adalah overcompacted instead of undercompacted. Kami tantang balik: coba tunjukkan satu cekungan sedimen di dunia, dimana cekungan tersebut relatif muda (Neogen kurang lebih), kemudian masih aktif mengalami sedimentasi, dan overpressure bukan disebabkan oleh disequilibrium compaction. Cekungan yang seperti ini sepertinya tidak ada di dunia (setidaknya sampai saat ini), dan LKB mungkin sangat unik! Kami menduga salah satu penyebab unloading yang utama di LKB adalah gas generation (kerogen to gas transformation). Penyebab lainnya kemungkinan adalah clay diagenesis (sebagai contoh transformasi illite jadi kaolinite). Hal ini masih terus kami teliti. Sebagai catatan, riset kami sebelumnya ini tidak mencakup deep-water Kutai Basin. Kami ingin sekali me-riset daerah ini, karena bisa jadi salah satu contoh klasik overpressure di deep water. Berminat mensponsori? Hehehe… Proses unloading overpressuring ini terutama dikontrol oleh temperatur, sehingga kami berhipotesis bahwa karena LKB ini dapat digolongkan sebagai ‘warm basin’ melihat thermal gradient-nya, maka proses-proses unloading sangat mungkin terjadi. Sebagai lanjutannya, kami berhipotesis juga bahwa di cekungan-cekungan sedimen lain di Indonesia, mengingat thermal gradient-nya cukup tinggi, unloading sangat boleh jadi merupakan penyebab terjadinya overpressure. Salah satu implikasi dari unloading overpressuring ini adalah kemungkinan ‘kegagalan’ metoda standard seperti Eaton’s Method untuk mengestimasi besarnya overpressure. Untuk mengestimasinya, diperlukan teknik-teknik spesial. Promosi: teknik spesial ini akan didiskusikan dengan cukup mendalam di workshop IAGI kami di Bali
Re: [iagi-net-l] Overpressure in Indonesia's sedimentary basins
Selamat Kang Agus MR. Salam. Dini Sent from my BlackBerry® smartphone from Sinyal Bagus XL, Nyambung Teruuusss...! -Original Message- From: Agus Mochamad Ramdhan Date: Mon, 27 Jun 2011 19:22:22 To: iagi-net@iagi.or.id Reply-To: Subject: [iagi-net-l] Overpressure in Indonesia's sedimentary basins Mas Bowo dan Ferdi, Thread-nya saya ubah jadi ‘overpressure in Indonesia’s sedimentary basins’ ya, sekalian promosi riset kami nih, hehehe. Mengenai overpressure di Lower Kutai Basin (LKB), ini kami kirimkan abstract dari paper kami yang akan diterbitkan kira-kira September ini di AAPG Bulletin. Sebagai acknowledgement, penulisan paper ini (termasuk PhD studentship saya), disponsori oleh Total E&P Indonesie: Terima kasih! Overpressure and shale compaction in the Lower Kutai Basin, Indonesia – a radical reappraisal Agus M. Ramdhan1* and Neil R. Goulty1 1Department of Earth Sciences, Durham University, South Road, Durham DH1 3LE, UK. *Present address: Department of Geology, Institut Teknologi Bandung, Jl. Ganesha 10, Bandung 40132, Indonesia. Corresponding author (e-mail: agu...@gc.itb.ac.id) ABSTRACT Lateral drainage and high temperatures in the shelfal area of the Lower Kutai Basin provide an exceptional opportunity to study compaction of Miocene shales and overpressure generation. Previous workers agreed that the principal mechanism of overpressure generation is disequilibrium compaction, but sonic and resistivity logs in several fields display reversals at a transition zone into high overpressure, indicating that overpressure is generated by unloading processes. The transition zone coincides with the vitrinite reflectance threshold for gas generation. Extreme overpressures in some wells are associated with reversals on density logs too, interpreted to result from cracks opening. The density–depth trends through the shales are similar in all wells and independent of overpressure until extreme overpressures are encountered. This observation strongly suggests that porosity reduction is controlled by chemical compaction and that cementation has caused the shales to become overcompacted, relative to the prevailing effective stress, at burial depths of ~3 km where the top of overpressure is encountered. Hence, the Lower Kutai Basin contains a unique reported example, to date, of a Neogene succession in which high overpressures are generated by unloading processes with no contribution from disequilibrium compaction. Density logs from the Peciko Field have been used to derive the empirical porosity–depth trend for shales in the depth range 6000–15,000 ft (1800–4600 m), where z is depth in thousands of feet. The corresponding temperatures range is 85–170°C, so this compaction curve applies for shales in the chemical compaction regime where no discrete smectite is present. Intinya memang kira-kira bahwa overpressure di LKB tidak disebabkan oleh undercompaction atau disequilibrium compaction (atau kita bisa sebut loading mechanism karena berhubungan dengan penambahan vertical load/sedimentation). Kami menduga penyebabnya adalah unloading (un-related-to loading). Kesimpulan kami ini cukup mengejutkan banyak peneliti yang mendalami overpressure. Mereka bertanya: “how come? You have ‘young’ sedimentary basin, undergoing moderate sedimentation rate, yet the overpressure is not caused by disequilibrium compaction?” Kami jawab, ya memang kami tidak menemukan sama sekali bukti disequilibrium compaction (porosity preservation at overpressure section). Malahan, kami menemukan bahwa sedimen di overpressured section adalah overcompacted instead of undercompacted. Kami tantang balik: coba tunjukkan satu cekungan sedimen di dunia, dimana cekungan tersebut relatif muda (Neogen kurang lebih), kemudian masih aktif mengalami sedimentasi, dan overpressure bukan disebabkan oleh disequilibrium compaction. Cekungan yang seperti ini sepertinya tidak ada di dunia (setidaknya sampai saat ini), dan LKB mungkin sangat unik! Kami menduga salah satu penyebab unloading yang utama di LKB adalah gas generation (kerogen to gas transformation). Penyebab lainnya kemungkinan adalah clay diagenesis (sebagai contoh transformasi illite jadi kaolinite). Hal ini masih terus kami teliti. Sebagai catatan, riset kami sebelumnya ini tidak mencakup deep-water Kutai Basin. Kami ingin sekali me-riset daerah ini, karena bisa jadi salah satu contoh klasik overpressure di deep water. Berminat mensponsori? Hehehe… Proses unloading overpressuring ini terutama dikontrol oleh temperatur, sehingga kami berhipotesis bahwa karena LKB ini dapat digolongkan sebagai ‘warm basin’ melihat thermal gradient-nya, maka proses-proses unloading sangat mungkin terjadi. Sebagai lanjutannya, kami berhipotesis juga bahwa di cekungan-cekungan sedimen lain di Indonesia, mengingat thermal gradient-nya cukup tinggi, unloading sangat boleh jadi merupakan penyebab terjadinya overpressure. S
Re: [iagi-net-l] Overpressure in Indonesia's sedimentary basins
Mas Agus, kalau ikutan jadi peneliti tapi bukan sponsor boleh enggak ? On 6/28/11, Agus Mochamad Ramdhan wrote: > Mas Bowo dan Ferdi, > > Thread-nya saya ubah jadi ‘overpressure in Indonesia’s sedimentary basins’ > ya, sekalian promosi riset kami nih, hehehe. > > Mengenai overpressure di Lower Kutai Basin (LKB), ini kami kirimkan abstract > dari paper kami yang akan diterbitkan kira-kira September ini di AAPG > Bulletin. Sebagai acknowledgement, penulisan paper ini (termasuk PhD > studentship saya), disponsori oleh Total E&P Indonesie: Terima kasih! > > > Overpressure and shale compaction in the Lower Kutai Basin, Indonesia – a > radical reappraisal > Agus M. Ramdhan1* and Neil R. Goulty1 > 1Department of Earth Sciences, Durham University, South Road, Durham DH1 > 3LE, UK. > *Present address: Department of Geology, Institut Teknologi Bandung, Jl. > Ganesha 10, Bandung 40132, Indonesia. Corresponding author (e-mail: > agu...@gc.itb.ac.id) > > ABSTRACT > > Lateral drainage and high temperatures in the shelfal area of the Lower > Kutai Basin provide an exceptional opportunity to study compaction of > Miocene shales and overpressure generation. Previous workers agreed that the > principal mechanism of overpressure generation is disequilibrium compaction, > but sonic and resistivity logs in several fields display reversals at a > transition zone into high overpressure, indicating that overpressure is > generated by unloading processes. The transition zone coincides with the > vitrinite reflectance threshold for gas generation. Extreme overpressures in > some wells are associated with reversals on density logs too, interpreted to > result from cracks opening. > > The density–depth trends through the shales are similar in all wells and > independent of overpressure until extreme overpressures are encountered. > This observation strongly suggests that porosity reduction is controlled by > chemical compaction and that cementation has caused the shales to become > overcompacted, relative to the prevailing effective stress, at burial depths > of ~3 km where the top of overpressure is encountered. Hence, the Lower > Kutai Basin contains a unique reported example, to date, of a Neogene > succession in which high overpressures are generated by unloading processes > with no contribution from disequilibrium compaction. > > Density logs from the Peciko Field have been used to derive the empirical > porosity–depth trend for shales in the depth range 6000–15,000 ft (1800–4600 > m), where z is depth in thousands of feet. The corresponding temperatures > range is 85–170°C, so this compaction curve applies for shales in the > chemical compaction regime where no discrete smectite is present. > > > Intinya memang kira-kira bahwa overpressure di LKB tidak disebabkan oleh > undercompaction atau disequilibrium compaction (atau kita bisa sebut loading > mechanism karena berhubungan dengan penambahan vertical load/sedimentation). > Kami menduga penyebabnya adalah unloading (un-related-to loading). > Kesimpulan kami ini cukup mengejutkan banyak peneliti yang mendalami > overpressure. Mereka bertanya: “how come? You have ‘young’ sedimentary > basin, undergoing moderate sedimentation rate, yet the overpressure is not > caused by disequilibrium compaction?” Kami jawab, ya memang kami tidak > menemukan sama sekali bukti disequilibrium compaction (porosity preservation > at overpressure section). Malahan, kami menemukan bahwa sedimen di > overpressured section adalah overcompacted instead of undercompacted. Kami > tantang balik: coba tunjukkan satu cekungan sedimen di dunia, dimana > cekungan tersebut relatif muda (Neogen kurang lebih), kemudian masih aktif > mengalami > sedimentasi, dan overpressure bukan disebabkan oleh disequilibrium > compaction. Cekungan yang seperti ini sepertinya tidak ada di dunia > (setidaknya sampai saat ini), dan LKB mungkin sangat unik! > > Kami menduga salah satu penyebab unloading yang utama di LKB adalah gas > generation (kerogen to gas transformation). Penyebab lainnya kemungkinan > adalah clay diagenesis (sebagai contoh transformasi illite jadi kaolinite). > Hal ini masih terus kami teliti. Sebagai catatan, riset kami sebelumnya ini > tidak mencakup deep-water Kutai Basin. Kami ingin sekali me-riset daerah > ini, karena bisa jadi salah satu contoh klasik overpressure di deep water. > Berminat mensponsori? Hehehe… > > Proses unloading overpressuring ini terutama dikontrol oleh temperatur, > sehingga kami berhipotesis bahwa karena LKB ini dapat digolongkan sebagai > ‘warm basin’ melihat thermal gradient-nya, maka proses-proses unloading > sangat mungkin terjadi. Sebagai lanjutannya, kami berhipotesis juga bahwa di > cekungan-cekungan sedimen lain di Indonesia, mengingat thermal gradient-nya > cukup tinggi, unloading sangat boleh jadi merupakan penyebab terjadinya > overpressure. > > Salah satu implikasi dari unloading overpressuring ini adalah kemungkinan > ‘kegagalan’ metoda standard seperti Eaton’s Metho
Re: [iagi-net-l] Overpressure in Indonesia's sedimentary basins
Mas Ferdy, sangat-sangat welcome, mas... Ditunggu di kampus kalo gitu... Atau tertarik sekalian S-3? Salam, Agus On Tue Jun 28th, 2011 3:26 AM PDT kartiko samodro wrote: >Mas Agus, kalau ikutan jadi peneliti tapi bukan sponsor boleh enggak ? > >On 6/28/11, Agus Mochamad Ramdhan wrote: >> Mas Bowo dan Ferdi, >> >> Thread-nya saya ubah jadi ‘overpressure in Indonesia’s sedimentary basins’ >> ya, sekalian promosi riset kami nih, hehehe. >> >> Mengenai overpressure di Lower Kutai Basin (LKB), ini kami kirimkan abstract >> dari paper kami yang akan diterbitkan kira-kira September ini di AAPG >> Bulletin. Sebagai acknowledgement, penulisan paper ini (termasuk PhD >> studentship saya), disponsori oleh Total E&P Indonesie: Terima kasih! >> >> >> Overpressure and shale compaction in the Lower Kutai Basin, Indonesia – a >> radical reappraisal >> Agus M. Ramdhan1* and Neil R. Goulty1 >> 1Department of Earth Sciences, Durham University, South Road, Durham DH1 >> 3LE, UK. >> *Present address: Department of Geology, Institut Teknologi Bandung, Jl. >> Ganesha 10, Bandung 40132, Indonesia. Corresponding author (e-mail: >> agu...@gc.itb.ac.id) >> >> ABSTRACT >> >> Lateral drainage and high temperatures in the shelfal area of the Lower >> Kutai Basin provide an exceptional opportunity to study compaction of >> Miocene shales and overpressure generation. Previous workers agreed that the >> principal mechanism of overpressure generation is disequilibrium compaction, >> but sonic and resistivity logs in several fields display reversals at a >> transition zone into high overpressure, indicating that overpressure is >> generated by unloading processes. The transition zone coincides with the >> vitrinite reflectance threshold for gas generation. Extreme overpressures in >> some wells are associated with reversals on density logs too, interpreted to >> result from cracks opening. >> >> The density–depth trends through the shales are similar in all wells and >> independent of overpressure until extreme overpressures are encountered. >> This observation strongly suggests that porosity reduction is controlled by >> chemical compaction and that cementation has caused the shales to become >> overcompacted, relative to the prevailing effective stress, at burial depths >> of ~3 km where the top of overpressure is encountered. Hence, the Lower >> Kutai Basin contains a unique reported example, to date, of a Neogene >> succession in which high overpressures are generated by unloading processes >> with no contribution from disequilibrium compaction. >> >> Density logs from the Peciko Field have been used to derive the empirical >> porosity–depth trend for shales in the depth range 6000–15,000 ft (1800–4600 >> m), where z is depth in thousands of feet. The corresponding temperatures >> range is 85–170°C, so this compaction curve applies for shales in the >> chemical compaction regime where no discrete smectite is present. >> >> >> Intinya memang kira-kira bahwa overpressure di LKB tidak disebabkan oleh >> undercompaction atau disequilibrium compaction (atau kita bisa sebut loading >> mechanism karena berhubungan dengan penambahan vertical load/sedimentation). >> Kami menduga penyebabnya adalah unloading (un-related-to loading). >> Kesimpulan kami ini cukup mengejutkan banyak peneliti yang mendalami >> overpressure. Mereka bertanya: “how come? You have ‘young’ sedimentary >> basin, undergoing moderate sedimentation rate, yet the overpressure is not >> caused by disequilibrium compaction?” Kami jawab, ya memang kami tidak >> menemukan sama sekali bukti disequilibrium compaction (porosity preservation >> at overpressure section). Malahan, kami menemukan bahwa sedimen di >> overpressured section adalah overcompacted instead of undercompacted. Kami >> tantang balik: coba tunjukkan satu cekungan sedimen di dunia, dimana >> cekungan tersebut relatif muda (Neogen kurang lebih), kemudian masih aktif >> mengalami >> sedimentasi, dan overpressure bukan disebabkan oleh disequilibrium >> compaction. Cekungan yang seperti ini sepertinya tidak ada di dunia >> (setidaknya sampai saat ini), dan LKB mungkin sangat unik! >> >> Kami menduga salah satu penyebab unloading yang utama di LKB adalah gas >> generation (kerogen to gas transformation). Penyebab lainnya kemungkinan >> adalah clay diagenesis (sebagai contoh transformasi illite jadi kaolinite). >> Hal ini masih terus kami teliti. Sebagai catatan, riset kami sebelumnya ini >> tidak mencakup deep-water Kutai Basin. Kami ingin sekali me-riset daerah >> ini, karena bisa jadi salah satu contoh klasik overpressure di deep water. >> Berminat mensponsori? Hehehe… >> >> Proses unloading overpressuring ini terutama dikontrol oleh temperatur, >> sehingga kami berhipotesis bahwa karena LKB ini dapat digolongkan sebagai >> ‘warm basin’ melihat thermal gradient-nya, maka proses-proses unloading >> sangat mungkin terjadi. Sebagai lanjutannya, kami berhipotesis juga bahwa di >> cekungan-cekungan sedimen lain di Ind
Re: [iagi-net-l] Overpressure in Indonesia's sedimentary basins
Mas Ferdy, sangat-sangat welcome, mas... Ditunggu di kampus kalo gitu... Atau tertarik sekalian S-3? Salam, Agus On Tue Jun 28th, 2011 3:26 AM PDT kartiko samodro wrote: >Mas Agus, kalau ikutan jadi peneliti tapi bukan sponsor boleh enggak ? > >On 6/28/11, Agus Mochamad Ramdhan wrote: >> Mas Bowo dan Ferdi, >> >> Thread-nya saya ubah jadi ‘overpressure in Indonesia’s sedimentary basins’ >> ya, sekalian promosi riset kami nih, hehehe. >> >> Mengenai overpressure di Lower Kutai Basin (LKB), ini kami kirimkan abstract >> dari paper kami yang akan diterbitkan kira-kira September ini di AAPG >> Bulletin. Sebagai acknowledgement, penulisan paper ini (termasuk PhD >> studentship saya), disponsori oleh Total E&P Indonesie: Terima kasih! >> >> >> Overpressure and shale compaction in the Lower Kutai Basin, Indonesia – a >> radical reappraisal >> Agus M. Ramdhan1* and Neil R. Goulty1 >> 1Department of Earth Sciences, Durham University, South Road, Durham DH1 >> 3LE, UK. >> *Present address: Department of Geology, Institut Teknologi Bandung, Jl. >> Ganesha 10, Bandung 40132, Indonesia. Corresponding author (e-mail: >> agu...@gc.itb.ac.id) >> >> ABSTRACT >> >> Lateral drainage and high temperatures in the shelfal area of the Lower >> Kutai Basin provide an exceptional opportunity to study compaction of >> Miocene shales and overpressure generation. Previous workers agreed that the >> principal mechanism of overpressure generation is disequilibrium compaction, >> but sonic and resistivity logs in several fields display reversals at a >> transition zone into high overpressure, indicating that overpressure is >> generated by unloading processes. The transition zone coincides with the >> vitrinite reflectance threshold for gas generation. Extreme overpressures in >> some wells are associated with reversals on density logs too, interpreted to >> result from cracks opening. >> >> The density–depth trends through the shales are similar in all wells and >> independent of overpressure until extreme overpressures are encountered. >> This observation strongly suggests that porosity reduction is controlled by >> chemical compaction and that cementation has caused the shales to become >> overcompacted, relative to the prevailing effective stress, at burial depths >> of ~3 km where the top of overpressure is encountered. Hence, the Lower >> Kutai Basin contains a unique reported example, to date, of a Neogene >> succession in which high overpressures are generated by unloading processes >> with no contribution from disequilibrium compaction. >> >> Density logs from the Peciko Field have been used to derive the empirical >> porosity–depth trend for shales in the depth range 6000–15,000 ft (1800–4600 >> m), where z is depth in thousands of feet. The corresponding temperatures >> range is 85–170°C, so this compaction curve applies for shales in the >> chemical compaction regime where no discrete smectite is present. >> >> >> Intinya memang kira-kira bahwa overpressure di LKB tidak disebabkan oleh >> undercompaction atau disequilibrium compaction (atau kita bisa sebut loading >> mechanism karena berhubungan dengan penambahan vertical load/sedimentation). >> Kami menduga penyebabnya adalah unloading (un-related-to loading). >> Kesimpulan kami ini cukup mengejutkan banyak peneliti yang mendalami >> overpressure. Mereka bertanya: “how come? You have ‘young’ sedimentary >> basin, undergoing moderate sedimentation rate, yet the overpressure is not >> caused by disequilibrium compaction?” Kami jawab, ya memang kami tidak >> menemukan sama sekali bukti disequilibrium compaction (porosity preservation >> at overpressure section). Malahan, kami menemukan bahwa sedimen di >> overpressured section adalah overcompacted instead of undercompacted. Kami >> tantang balik: coba tunjukkan satu cekungan sedimen di dunia, dimana >> cekungan tersebut relatif muda (Neogen kurang lebih), kemudian masih aktif >> mengalami >> sedimentasi, dan overpressure bukan disebabkan oleh disequilibrium >> compaction. Cekungan yang seperti ini sepertinya tidak ada di dunia >> (setidaknya sampai saat ini), dan LKB mungkin sangat unik! >> >> Kami menduga salah satu penyebab unloading yang utama di LKB adalah gas >> generation (kerogen to gas transformation). Penyebab lainnya kemungkinan >> adalah clay diagenesis (sebagai contoh transformasi illite jadi kaolinite). >> Hal ini masih terus kami teliti. Sebagai catatan, riset kami sebelumnya ini >> tidak mencakup deep-water Kutai Basin. Kami ingin sekali me-riset daerah >> ini, karena bisa jadi salah satu contoh klasik overpressure di deep water. >> Berminat mensponsori? Hehehe… >> >> Proses unloading overpressuring ini terutama dikontrol oleh temperatur, >> sehingga kami berhipotesis bahwa karena LKB ini dapat digolongkan sebagai >> ‘warm basin’ melihat thermal gradient-nya, maka proses-proses unloading >> sangat mungkin terjadi. Sebagai lanjutannya, kami berhipotesis juga bahwa di >> cekungan-cekungan sedimen lain di Ind
