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Befriko Saparindra Murdianto

Bayesian Approach for Constraining Facies Simulations with Seismic Information

"ABSTRACT

Subsurface models of lithology are often poorly constrained due to the lack of

dense well control. Although limited in vertical resolution, high-quality threedimensional

(3-D) seismic data usually provide valuable information regarding

the lateral variations of lithology. In this thesis, I will show how Bayesian

approach can be used to generate seismically constrained models of

lithology. Unlike cokriging-based simulation methods, this method does not

rely on a generalized linear regression model, which is inadequate when

combining discrete variables, such as lithology indicator; and continuous

variables, such as seismic attributes. This method uses a Bayesian updating

rule to construct a posterior probability distribution function of lithoclasses by

using a priori information from well data and the seismic likelihood to constrain

the 3-D geological scenarios produced by geostatistical technique, which is

then sampled sequentially at all points in space to generate a set of

realizations. The realizations define alternative, equiprobable lithologic

models. The methodology was applied to delineate productive reservoir zone

in Boonsville, Texas. To achieve better result in the Bayesian Sequential

Indicator Simulation, I used acoustic impedance obtained from a seismic

inversion process as the attribute to constrain the simulation. It is expected

that by using this attribute, the separation of the litho-class conditional

distribution will be well defined and at the same time minimizing the overlaps

between the two distributions. The lithology classification obtained from BSIS

is then integrated with the result of the seismic inversion to clearly delineate

the productive zone in the field."

2007

T21196

UI - Tesis Membership Universitas Indonesia Library

Dyah Tribuanawati

Estimasi Porositas pada Reservoar Batugamping dengan Menggunakan Inversi Seismik dan Pendekatan Geostatistik

"Metode litologi seismik bertumpu pada amplitudo gelombang-gelombang seismik yang dipantulkan oleh bidang batas antar lapisan. Litologi seismik menghasilkan penampang pseudosonic log, pseudo velocity atau impedansi akustik yang merepresentasikan litologi lebih baik dari pada seismik struktur.

Amplitudo dari sinyal seismik terpantul tergantung pada variasi impedansi akustik yang merupakan hasil kali kecepatan dan densitas. Sehingga perubahan pada salah satu parameter tersebut, kecepatan atau densitas batuan akan berkontribusi pada variasi respon seismik dari reservoar.

Litologi dan ketebalan reservoar serta sejumlah sifat petrofisika batuan seperti porositas dan saturasi fluida dipengaruhi kedua parameter tersebut. Oleh karena itu untuk mengestimasi sifat-sifat petrofisika batuan dengan menggunakan data seismik harus mengkuantisasi kontribusi masing-masing parameter petrofisika pada pengukuran akustik.

Metoda ini digunakan untuk mengestimasi parameter petrofisika reservoar migas dari data seismik sehingga disebut sebagai 'Seismically guided reservoir characterization di luar sumur pengeboran.

Geostatistik merupakan framework yang mengkombinasikan sample yang terdistribusi secara spatial, berdasarkan atas data log sumur dan data seismik. Yang berguna untuk estimasi yang akurat dari reservoar properties dari ketidakpastian dari model reservoar.

Dalam geostatistik mapping teknik ini berdasarkan atas Kriging, Regresi Linear dan Cokriging untuk memberikan kontribusi berdasarkan informasi petrofisika batuan yang diperoleh dari log sumur dan arah spatial dari seismik attribute. Secara garis besar teknik geostatistik untuk mengkombinasikan informasi petrofisika dan data seismik.

Dengan geostatistik pada situasi dengan minimal kontrol data, dapat memprediksi karakteristik reservoar dengan lebih baik dibandingkan dengan mapping standard.

Seismic Lithology method was introduced in the 1970's was based on amplitude of the seismic waves reflected by the subsurface interfaces. Seismic lithology generates pseudo sonic log, pseudo velocity log or acoustic impedance time section which represents the lithology better than the seismic structure. By using this method it is possible to estimate the petrophysical properties of the reservoir rocks from seismic data. Furthermore it is possible to estimate the reservoir parameters from seismic data. This approach enables to implement a new method which referred to as seismically guided reservoir characterization in the zones outside the borehole.
The amplitudes of reflected seismics signals depend primarily on variations in acoustic impedance. Changes in either rock velocity or density will contribute to variations in the seismic response of the reservoir. A number of petrophysical properties, such as porosity, fluid saturation affect both rock velocity and density. To estimate reservoir properties using seismic data it is necessary to quantify the respective contribution of each petrophysical parameter to the acoustic measurements.
A series of laboratory P wave and S wave measurement has been conducted on limestone core samples from Baturaja limestone reservoir. By using the laboratory acoustic measurement data to support seismic derived porosity and fluid saturation determination in the reservoir. Several parameters have been derived from transit time data such as P and S wave velocities, Poisson ratio. To provide relationship between fluid saturation, porosity, P wave velocity and Poisson ratio, and modify acoustic impedance, crossplots between the parameters have been generated using a combination of laboratory acoustic measurement on core samples and mathematic modelling.
A geostatistical technique integrating well and seismic data has been studied for mapping porosity in hydrocarbon reservoirs. The most important feature of the cokriging method is that it uses spatial correlation functions to model the lateral variability of seismic and porosity measurements in the reservoir interval.
Cokriging was tested on a numerically simulated reservoir model and compared first with kriging, then with a conventional least squares procedure relying only on local correlation between porosity and acoustic impedance. As compared to kriging, the seismically assisted geostatistical method detects subtle porosity lateral variations that cannot be mapped from sparse well data alone.
As compared to the standard least squares approach, cokriging provides not only more accurate porosity estimates that are consistent with the well data. Using seismically derived acoustic impedances, cokrigging also was applied to estimate the distribution of porosity in limestone reservoir."

1999

T-Pdf

UI - Tesis Membership Universitas Indonesia Library

Dina Zaenab

Identifikasi litologi fluida dengan menggunakan metode extended elastic impedance studi kasus lapangan blackfoot

"Extended Elastic Impedance method is one of the methods in reservoir characterization, which is used to identify lithology and fluids content. This method is an extension of Elastic Impedance method by changing Sin²θ in Zoeppritz equation with tan χ to get scaled reflectivity equation. χ is angle range between -90° up to 90°. By using proper angle (χ), we can calculate the reflectivity that associates with the log parameter (Gamma Ray, Porosity, Lamda-Rho and Mhu-Rho). To proceeds this scheme we need to derive gradient and intercept from AVO analysis, which is used in Zoeppritz equation to calculate reflectivity volume. The proper angle (χ), which is derived from Whitcombe equation, is 30° for Gamma Ray. While the proper angle (χ) for porosity, mhu-rho, and lambda-rho is 60°, -90° and 15° respectively.

The result of mhu-rho and lamda-rho inversion in the target area contain of sandstone and oil in the time depth range of 1545 ? 1573 ms for horizon 1 and horizon 2. Based on seismic inversion, lamda-rho and mhu-rho crossplot analysis we can see that the distribution of reservoir in target area has lamda-rho value between 9050 ? 9300 m/s*g/cc or 25 ? 37 GPa*g/cc and mhu-rho value between 7500 ? 11200 m/s*g/cc or 25 ? 35 GPa*g/cc."

Depok: Fakultas Matematika Ilmu Pengetahuan Alam Universitas Indonesia, 2009

T 26241

UI - Tesis Open Universitas Indonesia Library

Muhammad Fahrinaldo Febrian Ramadhan

Estimasi litologi reservoir lapangan "A" menggunakan pemodelan parameter anisotrop = Estimation of reservoir lithology in field "A" using modeling of litologi reservoir litologi reservoir

"Seismik anisotrop didefinisikan sebagai kebergantungan kecepatan seismik terhadap arah penjalaran gelombang di bawah permukaan tanah. Sifat anisotrop dalam batuan dapat muncul akibat beberapa faktor seperti struktur geologi dan jenis litologi. Fenomena hockey stick adalah efek dari medium anisotrop yang sering muncul pada offset jauh. Pengetahuan mengenai efek anisotrop menjadi hal yang penting dalam pengolahan dan intepretasi data seismik.

Proses NMO dengan menggunakan metode waktu tempuh hiperbolik pada medium anisotrop akan memperlihatkan fenomena hockey stick pada far offset. Biasanya fenomena tersebut akan di muting pada pengolahan data seismik dengan pendekatan model bumi isotrop. Hal ini mengakibatkan adanya informasi litologi yang hilang. Oleh karena itu, penelitian ini dilakukan menggunakan pendekatan anisotrop untuk mereduksi nilai residual moveout pada data yang memiliki offset panjang.

Dari hasil penelitian ini didapatkan bahwa metode waktu tempuh non-hiperbolik Alkhalifah lebih baik dalam melakukan koreksi NMO untuk medium anisotrop dengan offset yang panjang dibandingkan dengan metode waktu tempuh hiperbolik. Selain itu, metode waktu tempuh Alkhalifah juga dapat mengestimasi litologi suatu reservoir. Nilai parameter anisotrop ? dari persamaan tersebut memiliki pola yang sama dengan log gamma ray. Pada reservoir didapatkan nilai ? sand bernilai negative dan shale positif.

Seismic anisotropy is defined as the dependence of seismic velocity against the direction of wave propagation below the earth surface. The anisotropic properties in rocks arise due to the several factors, such as geological structures and the type of lithology. Hockey stick phenomenon is the result of anisotropic medium that often appears on the far offset. Knowledge of the anisotropic effect becomes important in processing and interpretation of seismic data.
The NMO correction by using the hyperbolic travel time on the anisotropic medium can show hockey stick phenomenon on the far offset. Usually the phenomenon will be muting on the seismic data processing with isotropic earth model approach. It will result in missing some of the lithologic information. Therefore, this research was conducted using anisotropic approach to reducing residual moveout for data which has a very long offset.
The results of this research showed that the Alkhalifah method of non hyperbolic travel time was better in the NMO correction for anisotropy medium with a long offset compared to the method of hyperbolic travel time. In addition, Alkhalifah method can also estimate the lithology of a reservoir. The value of anisotropic parameter from the equation itself has the same pattern as the gamma ray log. In reservoir, the sand has negative value and shale has positif value."

Depok: Fakultas Matematika dan Ilmu Pengetahuan Alam Universitas Indonesia, 2018

S-Pdf

UI - Skripsi Membership Universitas Indonesia Library

Martin Krisnomurti

Diskriminasi gas/wet-sand dengan menggunakan kombinasi impedansi poisson (impedansi litologi dan impedansi ) study kasus Lapangan Zhezet = Gas/Wet-Sand discrimination by using combination of Poisson-Impedance (lithology impedance and fluid impedance) case study of Zhezet Field

"[ABSTRAK

Identifikasi keberadaan hidrokarbon di bawah permukaan bumi merupakan

salah satu tujuan utama dalam eksplorasi lapangan minyak bumi dalam usaha

mengidentifikasi keberadaan hidrokarbon. Impedansi-poisson yang merupakan

salah satu metoda yang digunakan untuk mendiskriminasi sifat fisis batuan

terhadap fluida dengan cara mengamati sensitivitas dari rasio poisson telah

diterapkan lebih lanjut untuk menghasilkan suatu metoda turunan yang lebih baik.

Pendekatan sifat fisika batuan antara impedansi-poisson dengan log sumuran yang

merepresentasikan properti batuan menghasilkan suatu metoda turunan yang

dinamakan impedansi-litologi. Sedangkan pendekatan sifat fisis fluida yang

terkandung didalam batuan terhadap impedansi-poisson menghasilkan diskriminasi

kandungan fluida didalam batuan yang kemudian dinamakan impedansi-fluida.

Metoda TCCA – Target Coeffisien Corellation Analysis – yang digunakan

untuk mencari koefisien korelasi tertinggi dari sifat fisis batuan terhadap

impedansi-poisson telah digunakan dalam penelitian ini untuk menghasilkan log

sumuran impedansi-litologi dan impedansi-fluida yang kemudian di propagasi

dengan neural network. Hasil propagasi impedansi-litologi digunakan sebagai

input untuk kalkulasi atribut koherensi yang diperkuat dengan hasil propagasi

impedansi-fluida untuk menghasilkan prediksi sebaran batuan reservoar.

Dari hasil penelitian pada horison FS33 terlihat pola channel yang

terbentuk dan tervalidasi dengan data sumur. Demikian juga pada sayatan horison

FS37, pola channel batuan reservoar terlihat dengan jelas dan tervalidasi terhadap

dua sumur yang dilalui. Sedangkan pada sayatan horison FS42 selain

teridentifikasi pola channel reservoar yang terbentuk, teridentifikasi juga batuan

karbonat yang divalidasi dengan data sumur dan data batuan inti

ABSTRACT

Hydrocarbon identification in subsurface is one of main goals in petroleum

exploration so that the litho-fluid content discriminations are a part of hydrocarbon

identifications which have been widely applied today. Poisson-impedance which is

one of the new methods that are used to discriminate rocks by examining the

sensitivity of physical rock properties of poisson-ratio has been further developed

to produce derivatives method. Physical properties approaches between poissonratio

and a well-log which represents rock properties can be used to get highest

correlation to produce a new derivative well-log named lithology-impedance. As a

fluid-rock properties approach between poisson-ratio and a well-log represents

litho-fluid content properties produces a new derivative well-log named fluidimpedance.

TCCA method –Target Coeffisien Corellation Analyst– is used to find the

highest correlation coefficient of the physical properties of rock fluid on the

poisson ratio has been used in this study to generate two new derivatives well-log

which would be propagated by means of neural-networks. The result of lithologyimpedance

propagation is further proceed with seismic coherence attribute as a

reflection of geology and stratigraphy forms which are then combined with fluidimpedance

propagation result to emphasize reservoir prediction distribution

laterally.

The study results of FS33 slicing discovers sand channels pattern and

validated by well-log. Similarly with horizon slicing of FS37, patterns of sand

channels reservoir are clearly visible and validated against two well-logs that

passed. While on horizon slicing of FS42 besides discovering sand channels,

carbonate rocks is also identified which is validated by well-log and core sample

analyst.;Hydrocarbon identification in subsurface is one of main goals in petroleum