STUDI KOMPARASI METODE MIGRASI SEISMIK DALAM MENGKARAKTERISASI RESERVOIR MIGAS DI BLOK KANGEAN, LAUT BALI MENGGUNAKAN INVERSI IMPEDANSI AKUSTIK BERBASIS MODEL

ABSTRAK Karakterisasi reservoir menjadi penting dalam tahapan eksplorasi minyak dan gas bumi. Salah satu hal yang dibutuhkan untuk mencapai keakuratan dalam mengkarakterisasi reservoir adalah penampang seismik yang sesuai dengan penampang aslinya. Struktur lapisan bumi yang kompleks mengakibatkan gelombang terdifraksi, sehingga penampang seismik mengalami pembelokan dari posisi sebenarnya. Penelitian ini menerapkan metode migrasi seismik Kirchhoff dan Stolt (F-K) untuk mengembalikan posisi reflektor pada waktu dan kedalaman yang sebenarnya pada data seismik 2D di Perairan Utara Bali. Data seismik diintegrasikan dengan data sumur APS-1 sebagai kontrol untuk diinversikan dengan teknik inversi berbasis model sehingga dapat mengkarakterisasi reservoir. Penelitian ini bertujuan membandingkan hasil migrasi seismik yaitu migrasi Stolt dan migrasi Kirchhoff untuk diinversikan menggunakan metode inversi berbasis model sehingga dapat diketahui sejauh mana kualitas data seismik mempengaruhi proses karakterisasi reservoir. Nilai korelasi dari hasil analisis regresi antara log impedansi inversi dengan log impedansi data sumur pada migrasi Kirchhoff sebesar 0,739 dan galat regresi sebesar 873,54, sedangkan pada migrasi Stolt memiliki nilai korelasi sebesar 0,698 dan nilai galat sebesar 1236,17. Hal ini menunjukkan bahwa migrasi Kirchhoff lebih baik dari migrasi Stolt baik secara kualitatif maupun kuantitatif dalam mengkarakterisasi reservoir hidrokarbon. ABSTRACTReservoir characterization is an important method in gas and oil exploration. In order to obtain accuracy for defining reservoir, required seismic image that similar to the actual seismic image. The complexity of earth structure could cause diffracted waves, therefore, seismic image was diffracted from its actual position. This study applies Kirchhoff and Stolt (F-K) seismic migration methods to restore the position of the reflector at the actual time and depth seismic data in North Bali. Seismic data is integrated with APS-1 well data as controls to be converted with model-based inversion techniques so as to characterize the reservoir. This study aims to compare the results of seismic migration namely Stolt and Kirchhoff migration to be converted using a model-based inversion method so that it can be seen to what extent the quality of seismic data influences the reservoir characterization process. Correlation value from the results of regression analysis between inversion log impedance and well impedance log data in Kirchhoff migration is 0.739 and regression error is 873.54, while the Stolt migration has a correlation value of 0.698 and an error value of 1236.17. This shows that Kirchhoff's migration is better than Stolt migration both qualitatively and quantitatively in characterizing hydrocarbon reservoirs.

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Accuracy of wavelets, seismic inversion, and thin-bed resolution

Interpretation ◽

10.1190/int-2017-0023.1 ◽

2017 ◽

Vol 5 (4) ◽

pp. T523-T530

Author(s):

Ehsan Zabihi Naeini ◽

Mark Sams

Keyword(s):

Seismic Data ◽

Reservoir Characterization ◽

Low Frequency ◽

Seismic Inversion ◽

Inversion Method ◽

Frequency Content ◽

Frequency Model ◽

North West ◽

The North ◽

Well Data

Broadband reprocessed seismic data from the North West Shelf of Australia were inverted using wavelets estimated with a conventional approach. The inversion method applied was a facies-based inversion, in which the low-frequency model is a product of the inversion process itself, constrained by facies-dependent input trends, the resultant facies distribution, and the match to the seismic. The results identified the presence of a gas reservoir that had recently been confirmed through drilling. The reservoir is thin, with up to 15 ms of maximum thickness. The bandwidth of the seismic data is approximately 5–70 Hz, and the well data used to extract the wavelet used in the inversion are only 400 ms long. As such, there was little control on the lowest frequencies of the wavelet. Different wavelets were subsequently estimated using a variety of new techniques that attempt to address the limitations of short well-log segments and low-frequency seismic. The revised inversion showed greater gas-sand continuity and an extension of the reservoir at one flank. Noise-free synthetic examples indicate that thin-bed delineation can depend on the accuracy of the low-frequency content of the wavelets used for inversion. Underestimation of the low-frequency contents can result in missing thin beds, whereas underestimation of high frequencies can introduce false thin beds. Therefore, it is very important to correctly capture the full frequency content of the seismic data in terms of the amplitude and phase spectra of the estimated wavelets, which subsequently leads to a more accurate thin-bed reservoir characterization through inversion.

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Case study: Seismic resolution and reservoir characterization of thin sands using multiattribute analysis and bandwidth extension in the Daqing field, China

Interpretation ◽

10.1190/int-2019-0017.1 ◽

2020 ◽

Vol 8 (1) ◽

pp. T89-T102

Author(s):

David Mora ◽

John Castagna ◽

Ramses Meza ◽

Shumin Chen ◽

Renqi Jiang

Keyword(s):

Seismic Data ◽

Reservoir Characterization ◽

Statistical Significance ◽

Physical Property ◽

Seismic Attributes ◽

Oil Field ◽

Thin Layers ◽

Inversion Method ◽

Bandwidth Extension ◽

Multiattribute Analysis

The Daqing field, located in the Songliao Basin in northeastern China, is the largest oil field in China. Most production in the Daqing field comes from seismically thin sand bodies with thicknesses between 1 and 15 m. Thus, it is not usually possible to resolve Daqing reservoirs using only conventional seismic data. We have evaluated the effectiveness of seismic multiattribute analysis of bandwidth extended data in resolving and making inferences about these thin layers. Multiattribute analysis uses statistical methods or neural networks to find relationships between well data and seismic attributes to predict some physical property of the earth. This multiattribute analysis was applied separately to conventional seismic data and seismic data that were spectrally broadened using sparse-layer inversion because this inversion method usually increases the vertical resolution of the seismic. Porosity volumes were generated using target porosity logs and conventional seismic attributes, and isofrequency volumes were obtained by spectral decomposition. The resulting resolution, statistical significance, and accuracy in the determination of layer properties were higher for the predictions made using the spectrally broadened volume.

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Application of model-based inversion technique in a field in the coastal swamp depobelt, Niger delta

International Journal of Advanced Geosciences ◽

10.14419/ijag.v6i1.10124 ◽

2018 ◽

Vol 6 (1) ◽

pp. 122

Author(s):

Okoli Austin ◽

Onyekuru Samuel I. ◽

Okechukwu Agbasi ◽

Zaidoon Taha Abdulrazzaq

Keyword(s):

Niger Delta ◽

Reservoir Characterization ◽

Seismic Inversion ◽

Inversion Method ◽

Seismic Reflection Data ◽

Model Based ◽

Reflection Data ◽

X 32 ◽

Niger Delta Basin ◽

Bypassed Oil

Considering the heterogeneity of the reservoir sands in the Niger Delta basin which are primary causes of low hydrocarbon recovery efficiency, poor sweep, early breakthrough and pockets of bypassed oil there arises a need for in-depth quantitative interpretation and more analysis to be done on seismic data to achieve a reliable reservoir characterization to improve recovery, plan future development wells within field and achieve deeper prospecting for depths not penetrated by the wells and areas far away from well locations. An effective tool towards de-risking prospects is seismic inversion which transforms a seismic reflection data to a quantitative rock-property description of a reservoir. The choice of model-based inversion in this study was due to well control, again considering the heterogeneity of the sands in the field. X-26, X-30, and X-32 were used to generate an initial impedance log which is used to update the estimated reflectivity from which we would obtain our inverted volumes. Acoustic impedance volumes were generated and observations made were consistent with depth trends established for the Niger Delta basin, inverted slices of Poisson impedances validated the expected responses considering the effect of compaction. This justifies the use of inversion method in further characterizing the plays identified in the region.

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High-resolution reservoir characterization by an acoustic impedance inversion of a Tertiary deltaic clinoform system in the North Sea

Geophysics ◽

10.1190/1.3506039 ◽

2010 ◽

Vol 75 (6) ◽

pp. O57-O67 ◽

Cited By ~ 10

Author(s):

Daria Tetyukhina ◽

Lucas J. van Vliet ◽

Stefan M. Luthi ◽

Kees Wapenaar

Keyword(s):

North Sea ◽

Seismic Data ◽

Reservoir Characterization ◽

Structural Information ◽

Sampling Rate ◽

Seismic Inversion ◽

Acoustic Properties ◽

The North ◽

The North Sea ◽

Well Data

Fluvio-deltaic sedimentary systems are of great interest for explorationists because they can form prolific hydrocarbon plays. However, they are also among the most complex and heterogeneous ones encountered in the subsurface, and potential reservoir units are often close to or below seismic resolution. For seismic inversion, it is therefore important to integrate the seismic data with higher resolution constraints obtained from well logs, whereby not only the acoustic properties are used but also the detailed layering characteristics. We have applied two inversion approaches for poststack, time-migrated seismic data to a clinoform sequence in the North Sea. Both methods are recursive trace-based techniques that use well data as a priori constraints but differ in the way they incorporate structural information. One method uses a discrete layer model from the well that is propagated laterally along the clinoform layers, which are modeled as sigmoids. The second method uses a constant sampling rate from the well data and uses horizontal and vertical regularization parameters for lateral propagation. The first method has a low level of parameterization embedded in a geologic framework and is computationally fast. The second method has a much higher degree of parameterization but is flexible enough to detect deviations in the geologic settings of the reservoir; however, there is no explicit geologic significance and the method is computationally much less efficient. Forward seismic modeling of the two inversion results indicates a good match of both methods with the actual seismic data.

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Impact of phase rotation on reservoir characterization and implementation of seismic well tie technique for calibration offshore Nile Delta, Egypt

The Leading Edge ◽

10.1190/tle39050346.1 ◽

2020 ◽

Vol 39 (5) ◽

pp. 346-352

Author(s):

Mohamed G. El-Behiry ◽

Mohamed S. Al Araby ◽

Ramy Z. Ragab

Keyword(s):

Seismic Data ◽

Reservoir Characterization ◽

Nile Delta ◽

Seismic Wavelet ◽

Well Location ◽

Formation Behavior ◽

Dynamic Components ◽

Well Data ◽

Phase Amplitude ◽

Seismic Anomalies

Seismic wavelets are dynamic components that result in a seismic trace when convolved with reflectivity series. The seismic wavelet is described by three components: amplitude, frequency, and phase. Amplitude and frequency are considered static because they mainly affect the appearance of a seismic event. Phase can have a large effect on seismic appearance by changing the way it describes the subsurface. Knowing the wavelet properties of certain seismic data facilitates the process of interpretation by providing an understanding of the appearance of regional geologic markers and hydrocarbon-bearing formation behavior. The process through which seismic data wavelets are understood is called seismic well tie. Seismic well tie is the first step in calibrating seismic data in terms of polarity and phase. It ensures that the seismic data are descriptive to regional markers, well markers, and discoveries (if they exist). The step connects well data to seismic data to ensure that the seismic correctly describes well results at the well location. It then extends the understanding of seismic behavior to the rest of the area covered by the seismic data. Good seismic well tie will greatly reduce uncertainties accompanying seismic interpretation. One important outcome of the seismic well tie process is understanding the phase of seismic data, which affects how seismic data will reflect a known geologic marker or hydrocarbon-bearing zone. This understanding can be useful in quantifying discoveries attached to seismic anomalies and extending knowledge from the well location to the rest of the area covered by seismic data.

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Creating detailed subsurface models using predictive image-guided well-log interpolation

Interpretation ◽

10.1190/int-2016-0051.1 ◽

2017 ◽

Vol 5 (3) ◽

pp. T279-T285 ◽

Cited By ~ 8

Author(s):

Parvaneh Karimi ◽

Sergey Fomel ◽

Rui Zhang

Keyword(s):

Seismic Data ◽

Reservoir Characterization ◽

Structural Information ◽

Rock Properties ◽

Well Log ◽

Initial Model ◽

The North ◽

Structural Framework ◽

Seismic Image ◽

Seismic Reflectors

Integration of well-log data and seismic data to predict rock properties is an essential but challenging task in reservoir characterization. The standard methods commonly used to create subsurface model do not fully honor the importance of seismic reflectors and detailed structural information in guiding the spatial distribution of rock properties in the presence of complex structures, which can make these methods inaccurate. To overcome initial model accuracy limitations in structurally complex regimes, we have developed a method that uses the seismic image structures to accurately constrain the interpolation of well properties between well locations. A geologically consistent framework provides a more robust initial model that, when inverted with seismic data, delivers a highly detailed yet accurate subsurface model. An application to field data from the North Sea demonstrates the effectiveness of our method, which proves that incorporating the seismic structural framework when interpolating rock properties between wells culminates in the increased accuracy of the final inverted result compared with the standard inversion workflows.

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Simultaneous inversion of PP and PS seismic data

Geophysics ◽

10.1190/1.2194533 ◽

2006 ◽

Vol 71 (3) ◽

pp. R1-R10 ◽

Cited By ~ 51

Author(s):

Helene Hafslund Veire ◽

Martin Landrø

Keyword(s):

Seismic Data ◽

Reservoir Characterization ◽

Model Building ◽

Joint Inversion ◽

P Wave ◽

Inversion Method ◽

System Of Equations ◽

S Wave ◽

Data Set ◽

Simultaneous Inversion

Elastic parameters derived from seismic data are valuable input for reservoir characterization because they can be related to lithology and fluid content of the reservoir through empirical relationships. The relationship between physical properties of rocks and fluids and P-wave seismic data is nonunique. This leads to large uncertainties in reservoir models derived from P-wave seismic data. Because S- waves do not propagate through fluids, the combined use of P-and S-wave seismic data might increase our ability to derive fluid and lithology effects from seismic data, reducing the uncertainty in reservoir characterization and thereby improving 3D reservoir model-building. We present a joint inversion method for PP and PS seismic data by solving approximated linear expressions of PP and PS reflection coefficients simultaneously using a least-squares estimation algorithm. The resulting system of equations is solved by singular-value decomposition (SVD). By combining the two independent measurements (PP and PS seismic data), we stabilize the system of equations for PP and PS seismic data separately, leading to more robust parameter estimation. The method does not require any knowledge of PP and PS wavelets. We tested the stability of this joint inversion method on a 1D synthetic data set. We also applied the methodology to North Sea multicomponent field data to identify sand layers in a shallow formation. The identified sand layers from our inverted sections are consistent with observations from nearby well logs.

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Depth-domain seismic reflectivity inversion with compressed sensing technique

Interpretation ◽

10.1190/int-2016-0005.1 ◽

2017 ◽

Vol 5 (1) ◽

pp. T1-T9 ◽

Cited By ~ 3

Author(s):

Rui Zhang ◽

Kui Zhang ◽

Jude E. Alekhue

Keyword(s):

Compressed Sensing ◽

Time Domain ◽

Seismic Data ◽

Reservoir Characterization ◽

Synthetic Data ◽

Seismic Inversion ◽

Inversion Method ◽

Depth Migration ◽

Band Limited ◽

The Time Domain

More and more seismic surveys produce 3D seismic images in the depth domain by using prestack depth migration methods, which can present a direct subsurface structure in the depth domain rather than in the time domain. This leads to the increasing need for applications of seismic inversion on the depth-imaged seismic data for reservoir characterization. To address this issue, we have developed a depth-domain seismic inversion method by using the compressed sensing technique with output of reflectivity and band-limited impedance without conversion to the time domain. The formulations of the seismic inversion in the depth domain are similar to time-domain methods, but they implement all the elements in depth domain, for example, a depth-domain seismic well tie. The developed method was first tested on synthetic data, showing great improvement of the resolution on inverted reflectivity. We later applied the method on a depth-migrated field data with well-log data validated, showing a great fit between them and also improved resolution on the inversion results, which demonstrates the feasibility and reliability of the proposed method on depth-domain seismic data.

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Inversion of reservoir fluid mobility from the frequency-dependent seismic data-a case study of gas-bearing reservoirs

Interpretation ◽

10.1190/int-2020-0084.1 ◽

2020 ◽

pp. 1-47

Author(s):

Yijiang Zhang ◽

Xiaotao Wen ◽

Dongyong Zhou ◽

Wenhua Wang ◽

Man Lu ◽

...

Keyword(s):

Seismic Data ◽

Extraction Method ◽

Low Frequency ◽

Real Data ◽

Inversion Method ◽

Frequency Dependent ◽

Reservoir Fluid ◽

Well Data ◽

Gas Bearing ◽

Mobility Coefficient

The reservoir fluid mobility is by definition the ratio of rock permeability to fluid viscosity. This attribute can be applied to reservoir physical property and permeability evaluation. So far, the only means of obtaining the reservoir fluid mobility over a large range of exploration areas is based on the extraction method. However, the location of high fluid mobility obtained by the extraction method is close to the reservoir interface. To obtain the fluid mobility in the middle of the reservoir, an approximate inversion method of reservoir fluid mobility from frequency-dependent seismic data is proposed. Firstly, we calculate the reservoir fluid mobility coefficient using well data according to the relationship of fluid parameters. Then, we establish an inversion equation based on the low-frequency reflection coefficient and the reservoir fluid mobility. Taking the reservoir fluid mobility coefficient calculated from well data as a priori constraint, the low-frequency model is subsequently constructed and applied with the inversion equation to obtain an inversion objective function. Next, the inversion equation is solved by the basis pursuit algorithm. Finally, the proposed reservoir fluid mobility inversion method is applied to synthetic and real data of gas-bearing reservoirs. The real data processing results show that the proposed reservoir fluid mobility inversion method can estimate the fluid mobility in the actual position of the reservoir more effectively.

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