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"Inversi seismik deterministik sudah banyak digunakan dalam lapangan eksplorasi dan pengembangan. Metode ini digunakan sebagai salah satu cara untuk karakterisasi reservoir dengan menghilangkan efek wavelet sehingga dapat membantu interpreter untuk memetakan struktur bawah permukaan dengan lebih baik. Akan tetapi, metode ini memiliki limitasi karena menggunakan impedansi rata-rata dari layer seismik dimana pada umumnmya nilai impendansi lebih kecil daripada impedansi data sumur sehingga dihasilkan model inversi yang tidak sesuai. Metode inversi stokastik menggunakan konsep geostatistikal, dimana variogram berperan penting dalam menghasilkan output yang sesuai. Pada inversi stokastik dihasilkan banyak realisasi inversi yang digunakan sebagai basis dalam analisis uncertainty, tiap realisasi akan sama pada tiap lokasi sumur yang digunakan namun akan berubah seiring dengan bertambahnya jarak spasial dari lokasi sumur. Metode inversi stokastik akan diaplikasikan pada lapangan gas K yang terletak di lepas pantai cekungan Bonaparte, Indoensia Timur. Data yang tersedia antara lain, sebagian dari 3D PSTM angle gather dengan luasan 1,300 km2, 3 sumur dengan data P-Sonic, S-Sonic, densitas, Gamma Ray, dan log resistivitas. Tambahan data berupa report komplesi dan report well testing tersedia untuk beberapa sumur. Lapangan gas K terletak pada undeformed continental margin Australia yang melampar kearah lndonesia, dimana secara geologi lapangan K terletak pada area Timur dari Sahul Platform dan memiliki struktur berupa tilted fault block. Lapangan ini memiliki reservoir batupasir formasi Plover yang tersaturasi gas dengan hidrokarbon kolom cukup signifikan, dimana reservoir terdeposisi pada lingkungan shallow marine pada umur Middle Jurasic. Target utama pada lapangan gas K merupakan struktural trap berupa horst block, tilted fault block yang berada dibawah sub-unconformity di umur Palaezoic. Penerapan metode inversi stokastik pada lapangan gas K menghasilkan kelebihan yang cukup signifikan dibandingkan dengan inversi deterministik. Reservoir pada lapangan gas K terdiri dari batupasir dengan persilangan shale tipis. Metode inversi stokastik dapat membedakan antara batupasir yang tersaturasi gas dengan intraformational shale tipis yang tidak teresolusi oleh seismik dan inversi deterministik. Hasil realisasi dapat digunakan untuk analisis uncertainty dengan probabilitas P10, P50, dan P90 dari facies yang dihasilkan.

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Deterministic seismic inversion method has been successfully used in various projects in exploration and development. This method enables the interpreter to get better understanding of subsurface by omitting the wavelet and tuning effects therefore quantitative reservoir properties can be generated. However, this method has significant limitation by generating average impedances of each layer, and the range of values is smaller than the impedance from the wells therefore the inversion will not produce results that are not within the calibration range. Stochastic seismic inversion is done by conditioning well data and reproducing spatially varying statistics using variogram which could overcome the deterministic limitation. This method generates multiple realizations of high-frequency elastic properties that are consistent with both seismic amplitude and well data. In such instances, stochastic seismic inversion method could provide the uncertainties associated with the models that have been generated. The proposed method is applied in K gas field which located in the offshore Bonaparte Basin, Eastern Indonesia. The available dataset for this work includes : part of PSTM 3D which cover 1,300 km2 in angle gather, and 3 wells with compressional sonic, shear sonic, density, gamma ray, and resistivity logs. Additional well completion and well testing reports are available for some wells. Geologically, the K field is located within relatively undeformed Australian continental margin that extends into Indonesian waters. It lies on the eastern extremity of the Sahul Platform and occupies a large tilted fault block bounded to the east and south by the Calder-Malita Grabens. This field contains a significant gas column, reservoired within shallow marine, highly mature, quartzose sandstone of the Middle Jurassic Plover Formation. Potential targets in the area may be large folds, horst blocks, tilted fault blocks ad sub-unconformity traps in the Palaeozoic section. The application of stochastic seismic inversion showed significant benefits compared to deterministic especially in K gas field where the reservoirs are stacked sandstone with intra-formational shale. Some of the reservoir and all the intraformational shales are below seismic resolution. Stochastic seismic inversion able to distinguish those features, in addition the inverted volumes with multiple realizations with ranking criteria for P10, P50, and P90 of facies could be utilized to reduce the risk associated with exploration plan and field development."

"[Inversi seismik deterministik telah dilakukan dengan menggunakan data PSTM di Lapangan Coki, Cekungan Kutai. Konsentrasi dari studi ini adalah zona Utama dengan kedalaman kurang lebih 3 km yang merupakan zona dengan akumulasi gas terbanyak. Tujuan utama dari penelitian ini adalah untuk mengidentifikasi ekstensidari batupasir di Zona Utama dengan menggunakan metode klasifikasi lithoseismic berdasarkan input dari hasil inversi seismik deterministik mengingat kontribusi seismik untuk pengembangan zona Utama sangat kecil sebelumnya dikarenakanresolusi yang terbatas. Studi kelayakan fisika batuan menunjukkan bahwa untuk Zona Utama, kandungan fluida gas dan air sudah tidak bisa dipisahkan lagi di crossplot P-Impedance vsPoisson’s Ratio.Sedangkan untuk pemisahan litologi batupasir dan batulempung secara umum masih bisa dipisahkan terutama untuk batupasir dengan kualitas bagus. Dengan menggunakan cube P-Impedance dan Poisson’s Ratio hasil seismik inversi sebagai input, klasifikasi lithoseismic dilakukan untuk memisahkanbatupasir dan batulempung. Hasil akhir dari proses ini adalah sand probability cube. Sand probability cube ini selanjutnya diinterpretasi dan digunakan untuk memprediksi ekstensi dari sand di zona Utama. Hasil interpretasi menemukan beberapa target baru di daerah dimana tidak ada kontrol dari sumur dan amplitudoseismic tidak menunjukkan karakteristik khusus. Berdasarkan hasil interpretasi ini optimalisasi trayektori dan desain beberapa sumur dilakukan.

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Deterministic seismic inversions were performed using PSTM (Pre-stack time migration) data in the Coki field, Kutai Basin. The study concentrated on the Peciko Main Zone (~3 km burial depth) which is the main gas producing interval of the field.

The main objectives of this project were to identify and map sand and possibly to define new targets for future development wells. Until 2012, seismic data had little contribution to well planning for this interval since their resolutions are poor and the seismic images only show the thick packages of stacked reservoirs. A rock physics feasibility study on P-impedancevs. Poisson’s Ratio crossplot showed that water and gas sands overlap each other significantly, meanwhile sand are discriminated from shale in particular for good quality sand. Lithoseismic classification is done using inverted P-impedance and Poisson’s Ratio to discriminate sand from shale. The final result is sand probability cube. Sand probability cube is then interpreted and used to define possible extension of sand limit for Main Zone.The final interpretation discovered several new targets where there is no well control and the seismic amplitudes didn’t show any distinctive characteristics. Then well trajectories are optimized using defined sand extension in

order to better target the reservoir.;Deterministic seismic inversions were performed using PSTM (Pre-stack time

migration) data in the Coki field, Kutai Basin. The study concentrated on the Peciko

Main Zone (~3 km burial depth) which is the main gas producing interval of the field.

The main objectives of this project were to identify and map sand and possibly to

define new targets for future development wells. Until 2012, seismic data had little

contribution to well planning for this interval since their resolutions are poor and the

seismic images only show the thick packages of stacked reservoirs.

A rock physics feasibility study on P-impedancevs. Poisson’s Ratio crossplot showed

that water and gas sands overlap each other significantly, meanwhile sand are

discriminated from shale in particular for good quality sand. Lithoseismic

classification is done using inverted P-impedance and Poisson’s Ratio to discriminate

sand from shale. The final result is sand probability cube.

Sand probability cube is then interpreted and used to define possible extension of

sand limit for Main Zone.The final interpretation discovered several new targets

where there is no well control and the seismic amplitudes didn’t show any distinctive

characteristics. Then well trajectories are optimized using defined sand extension in

order to better target the reservoir.;Deterministic seismic inversions were performed using PSTM (Pre-stack time

migration) data in the Coki field, Kutai Basin. The study concentrated on the Peciko

Main Zone (~3 km burial depth) which is the main gas producing interval of the field.

The main objectives of this project were to identify and map sand and possibly to

define new targets for future development wells. Until 2012, seismic data had little

contribution to well planning for this interval since their resolutions are poor and the

seismic images only show the thick packages of stacked reservoirs.

A rock physics feasibility study on P-impedancevs. Poisson’s Ratio crossplot showed

that water and gas sands overlap each other significantly, meanwhile sand are

discriminated from shale in particular for good quality sand. Lithoseismic

classification is done using inverted P-impedance and Poisson’s Ratio to discriminate

sand from shale. The final result is sand probability cube.

Sand probability cube is then interpreted and used to define possible extension of

sand limit for Main Zone.The final interpretation discovered several new targets

where there is no well control and the seismic amplitudes didn’t show any distinctive

characteristics. Then well trajectories are optimized using defined sand extension in

order to better target the reservoir.;Deterministic seismic inversions were performed using PSTM (Pre-stack time

migration) data in the Coki field, Kutai Basin. The study concentrated on the Peciko

Main Zone (~3 km burial depth) which is the main gas producing interval of the field.

The main objectives of this project were to identify and map sand and possibly to

define new targets for future development wells. Until 2012, seismic data had little

contribution to well planning for this interval since their resolutions are poor and the

seismic images only show the thick packages of stacked reservoirs.

A rock physics feasibility study on P-impedancevs. Poisson’s Ratio crossplot showed

that water and gas sands overlap each other significantly, meanwhile sand are

discriminated from shale in particular for good quality sand. Lithoseismic

classification is done using inverted P-impedance and Poisson’s Ratio to discriminate

sand from shale. The final result is sand probability cube.

Sand probability cube is then interpreted and used to define possible extension of

sand limit for Main Zone.The final interpretation discovered several new targets

where there is no well control and the seismic amplitudes didn’t show any distinctive

characteristics. Then well trajectories are optimized using defined sand extension in

order to better target the reservoir., Deterministic seismic inversions were performed using PSTM (Pre-stack time

migration) data in the Coki field, Kutai Basin. The study concentrated on the Peciko

Main Zone (~3 km burial depth) which is the main gas producing interval of the field.

The main objectives of this project were to identify and map sand and possibly to

define new targets for future development wells. Until 2012, seismic data had little

contribution to well planning for this interval since their resolutions are poor and the

seismic images only show the thick packages of stacked reservoirs.

A rock physics feasibility study on P-impedancevs. Poisson’s Ratio crossplot showed

that water and gas sands overlap each other significantly, meanwhile sand are

discriminated from shale in particular for good quality sand. Lithoseismic

classification is done using inverted P-impedance and Poisson’s Ratio to discriminate

sand from shale. The final result is sand probability cube.

Sand probability cube is then interpreted and used to define possible extension of

sand limit for Main Zone.The final interpretation discovered several new targets

where there is no well control and the seismic amplitudes didn’t show any distinctive

characteristics. Then well trajectories are optimized using defined sand extension in

order to better target the reservoir.]"