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Shiraz 2009 - 1st EAGE International Petroleum Conference and Exhibition

  • Conference date: 04 May 2009 - 09 May 2009
  • Location: Shiraz, Iran
  • ISBN: 978-90-73781-65-8
  • Published: 04 May 2009

21 - 40 of 140 results

    • Uplift in Sedimentary Basins Revisited - New Insights from the Voring Basin, Norwegian Sea

      https://doi.org/10.3997/2214-4609.20145871

      Many sedimentary basins show subsidence pattern that cannot be explained by uniform stretching models. In fact, uplift, or reduced subsidence, appears to be common during basin evolution. In this study we review the causes and consequences of different uplift mechanisms. Using a two-dimensional basin model we explore how differential thinning, mineral phase transitions, and magmatic underplating affect the structural and thermal evolutions of sedimentary basins. The paper is divided into two parts: the first part explores the characteristics of different uplift mechanisms, while the second part shows the results of a reconstruction case study. The case study focuses on the structural and thermal evolution of the Gjallar Ridge, a structural high in the Norwegian Sea that was uplifted to sealevel during the last rifting phase. The key findings are: (i) all discussed uplift mechanisms show characteristic structural and thermal evolutions that can potentially be used to discriminate between them, (ii) mineral phase transitions can enhance mantle thinning induced uplift, (iii) uplift of the Gjallar Ridge is explainable by different scenarios but phase transitions and differential thinning appear the most likely, and (iv) integrated basin modeling is key for discriminating between different uplift scenarios.

    • Kopet-Dagh Basin Evolution During Middle-late Jurassic

      https://doi.org/10.3997/2214-4609.20145873

      In this paper with the help of latest available data including field, well and seismic data, palaeoenvironments and depositional sequences of Kashafrud, Chaman Bid and Mozduran formations constructed in order to determine the basin evolution of the Kopet-Dagh during Middle-Late Jurassic. Our study reveals that wedge-shaped sedimentary units, onlap surfaces, high sedimentation rate along with deepening- and fining-upward, assign extensional regime as the result of rifting during Middle Jurassic. The sequence of initial rapid continental stretching during the Middle Jurassic, followed by slower and thermally driven subsidence in the Late Jurassic. Tectonosedimentary evolution of the Kopet-Dagh Basin during Middle-Late Jurassic has a great interest for the future exploration and production in this rich but poorly understood hydrocarbon province.

    • Origin of Gaseous Hydrocarbons of the Outer Carpathians and Palaeozoic-Mesozoic Basement in Southeastern Poland

      https://doi.org/10.3997/2214-4609.20145874

      Natural gases accumulated both in the Polish Outer (Flysch) Carpathians and the Palaeozoic-Mesozoic basement are genetically related to thermogenic and microbial processes. Thermogenic gaseous hydrocarbons accumulated in the Dukla and Silesian units were generated from Type-II and -II/III kerogen of the Menilite Shales. Thermogenic gaseous hydrocarbons accumulated in the Sub-Silesian Unit migrated from the Silesian Unit. Natural gases accumulated in traps within the Middle Devonian, Lower Carboniferous and Upper Jurassic strata of the Palaeozoic-Mesozoic basement were mainly generated during thermogenic processes and only sporadically during microbial processes. The themogenic gases accumulated within Palaeozoic complex were generated from Type-II kerogen of the Ordovician-Silurian strata and gases accumulated within Mesozoic complex from Type-III (II/III) kerogen of the Middle Jurassic strata. In some traps within the Dukla and Silesian units of the Outer Carpathians and Palaeozoic-Mesozoic basement had already been formed and sealed as early as the initial, microbial transformation stage of the source rocks. These traps were successively supplied with thermogenic gaseous and liquid hydrocarbons generated from the same source organic matter at successively higher maturation stage.

    • Seismic Facies Analysis Based on K-means Clustering Algorithm Using 3D Seismic Attributes

      Authors H. Sabeti and A. Javaherian
      https://doi.org/10.3997/2214-4609.20145876

      In seismic interpretation, clustering seismic data can be used to extract more information about structures and geology of underground units. In this paper, an efficient clustering method called k-means clustering algorithm is utilized to categorize seismic facies based on seismic attributes. By a given k value (i.e. the number of clusters), k-means clustering algorithm uses an iterative algorithm that minimizes the sum of distances from each sample to its cluster centroid over all clusters. This algorithm moves samples between clusters until the sum cannot be decreased further. The result is a set of clusters that are as compact and well-separated as possible. By applying this method over a synthetic seismic cube it is concluded that lateral changes in layer boundaries are detectable. In the case of real data, in order to increase the information needed for clustering, eight seismic attributes were calculated using Paradigm software. By applying k-means clustering algorithm to real dataset, it is shown that more seismic facies appears by increasing the k value and this leads to extract useful information about underground beddings.

    • 3D Pore Pressure Prediction Using Seismic Data in an Oil Field in SW Iran

      https://doi.org/10.3997/2214-4609.20145877

      The pore pressure prediction method based on seismic velocity field is a common method for constructing a 3-D pore pressure cube. In this study, the resolution of stacking velocity was improved using sonic logs and a geostatistical calibration method. In this calibration procedure, the differences between velocity derived from sonic logs and stacking velocity were calculated and, then, the calibration parameters were obtained. These parameters were interpolated in the velocity grids. Effective pressures were calculated using the measured pore pressures and the calculated overburden pressures at well locations. The coefficients of Bowers equation were calculated using well data. Using the Bowers equation the calibrated stacking velocity cube was converted to the effective pressure cube. The pore pressure cube was constructed by computing the differences between the overburden pressure cube and the effective pressure cube. Finally the predicted pore pressure cube was calibrated with regard to the measured pore pressures at well locations. In the area of study, the stacking velocity was improved and, then, the pore pressure cube was made accordingly. The predicted pressures show good agreement with regard to the measured pressures at well locations.

    • Determination of Bin Size and Migration Aperture in 3D Seismic Survey Design for AHWAZ Oil Field

      https://doi.org/10.3997/2214-4609.20145879

      In oil exploration, because of anisotropy of the earth, velocity of the waves in horizontal and vertical directions are not uniform; but we can apply the assumption with good accuracy in exploration procedure that in a layer, velocity changing is limited as a result of slow variation in density and elastic properties of the layers in this horizontal directions. In general, variation of above parameters in horizontal directions is very slowly than vertical directions. For this reason often divide acquisition area to smaller areas and ignore horizontal variations and apply same vertical velocity distribution in any sub-areas. Conventional formula for Bin size and migration aperture is based on constant velocity assumptions. In this paper calculation of Bin size and migration aperture for AHWAZ oil field is carried out base on linear model between velocity and depth. On the other hand Bin size and migration aperture have the firstorder effects on acquisition and processing cost, thus method of this paper steer to optimize and reduce the cost of acquisition.

    • Estimation of Well Log Data by Conjunctive Use of Seismic and Petrophysical Data (Hendijan Oil Field, Iran)

      https://doi.org/10.3997/2214-4609.20145881

      Well logs are of the important tools for reservoir characterization. Parameters such as porosity, volume of shale, water saturation, permeability, lithology and production zones could be computed from processing and interpreting of well logs. Such information is obtained from petrophysical logs. Considering coverage and continuity of seismic data, log estimation in each location of reservoir by using seismic data, not only before the drilling but also after it will be applied and invaluable. So that using the predicted wells log from seismic data, reservoir evaluation and assessment over the seismic data coverage is possible. In this research, a formulation is established between well log data including sonic and density logs and their corresponding seismic attributes using neural networks in Hendijan oil field, Persian Gulf. For this purpose, optimal input seismic attributes were obtained using a forward stepwise regression. The results show a good agreement between measured and neural network predicted data at test wells. So, the estimated well logs could be used for reservoir parameters evaluation and reducing risks of future exploration and field’s development. Also such predicted well logs enable us to gain more vital parameter about a reservoir.

    • Seismic Velocity – Reservoir Permeability Relations within Hydraulic Units in an Oil Field Southwest Iran

      Authors M. Emami Niri and A. Misaghi
      https://doi.org/10.3997/2214-4609.20145882

      Establishing a relation between permeability and velocity has met with little success so far. Different types of uncertainties usually make this relationship not very straightforward. Categorizing the pore systems in different hydraulic units may reduce the uncertainties. This study tries to improve characterization of a carbonate reservoir with complex pore systems which is located in southwest of Iran. A combination of classification methods was used to build a robust determination of Hydraulic Units using porosity and permeability values. Then the concept of grouping porosity and permeability data according to their FZI (Flow Zone Indicator) values were tested. It was shown that such relation can be extended to seismic parameters to create strong correlation between velocity and permeability. Strong correlation between P and S waves' velocity and permeability in this field was observed, i.e. the correlation coefficient for Vp-Permeability lies between 0.72-0.96 and for VS-Permeability lies between 0.62-9.98. Such a relation is invaluable as a prediction tool. We understood that by grouping rocks into hydraulic units, we can control and predict flow properties such as permeability via seismic velocity in this field.

    • Seismic Attribute Redundancy Reduction Using Statistical Feature Extraction Technique

      https://doi.org/10.3997/2214-4609.20145883

      Combining seismic attributes and building a meta-attribute section is a useful stage for seismic object detection (fault, gas chimney and …), seismic facies analysis and many other applications. Many seismic attributes used in classification tasks are redundant, which yield a useless higher-dimensional feature space. In this paper, a criterion based on RDA with two sub-optimal forward and backward algorithms is presented to accomplish this problem. Then, classification based on four different MLP neural networks is done and the average error is plotted versus the ranked feature space. As a flexible method, the algorithm introduces dissimilar ranks as the training set changed by the user. This makes it possible to introduce several seismic attributes in input stage of the classification. Based on the proposed training set, the interpreter can find the most important seismic attributes for the classification.

    • Side View Seismic Location Method Helps Fracture Characterization in a Giant Fractured Carbonate Heavy Oil Field in Iran

      https://doi.org/10.3997/2214-4609.20145884

      Kuh-e-Mond heavy oil field is the largest onshore naturally fractured heavy oil carbonate field in Iran with a resource base of 6-10 Bb OOIP. The heavy oil is found in two formations with oil viscosities of 570-1160 cP in situ. Having a clear picture of the natural fracture fabric of the reservoir will help petroleum engineers and development geologists to determining orientation and flow characteristics of the dominant fracture sets in order to optimize production well placement. In this article, results from fractured media investigations using the Side View Seismic Location (SVSL) method are presented. The SVSL results indicate a transversely oriented zone of minimum values of open fracturing in the NW part of the field, which separates the field into two isolated blocks. The SE part is characterized by a high concentration of abnormally fractured zones and is considered to be the most promising area for primary field development. Based on this study a number of suitable locations for production well placement are proposed. Also, implementing proper down-hole operations in some of the existing wells are recommended to further assess the fabric and arrive at a development strategy.

    • Multiple Attenuation by F-X Parabolic Radon Transform

      https://doi.org/10.3997/2214-4609.20145887

      Multiples constitute one of the most troublesome forms of coherent noise in seismic exploration. Multiple reflections often destructively interfere with the primaries of interest. Therefore, suppressing multiples from reflection seismograms during processing stages is necessary. Radon transform is a robust tool for suppressing multiples from seismic data. The key idea in Radon based multiple attenuation is to map the CMP gather to a new domain where seismic reflections collapse to point-like events and, therefore, primaries and multiples are separable. The time invariant parabolic Radon transform is widely accepted for multiple suppression. The benefit of time invariance is that the computations can be performed in the frequency-space domain and so the computational costs are reduced. In this procedure, the first step is to replace hyperbolic events in offset domain with parabolas by applying NMO correction using velocities of primaries. In the next step, the data are transformed to the Radon domain by stacking amplitudes along parabolic trajectories. In this paper, a MATLAB coding for multiple attenuation using the parabolic Radon transform has been implemented and successfully applied on a synthetic model and a real data set. KEYWORDS: Radon transform, multiple attenuation, SNR enhancement, coherent noise

    • Rayleigh Wave Suppression in the RT Domain

      https://doi.org/10.3997/2214-4609.20145888

      Always on seismic data record, reflection event will be masked with Ground_roll and observation of this event is not usually easy. Radial trace transform is a simple transform for mapping x-t gathered data into apparent velocity and travel time domain. The apparent frequency of Ground_roll will be changed completely in RT domain. With knowledge of this changes and the application of frequency filters in RT domain, these events can be attenuated. In this paper the result obtained from F-K method and RT method on one common shot gather acquired from oil field has been compared. The results showed that the RT filters is much better attenuate those events with respect to F-K method without much reducing amplitude spectrum.

    • Solving the Problem of Conflicting Dips in Common-Reflection-Surface (CRS) Stack

      https://doi.org/10.3997/2214-4609.20145889

      CRS stack procedure is a data-driven imaging method which is independent of an explicit velocity model. The pragmatic search strategy for CRS attributes consists of three one-parameter searches. This implementation determines only one optimum stacking operator for each ZO sample to be simulated. Consequently, conflicting dip situations are not taken into account. In one of the efforts to overcome this problem, the strategy has been extended in order to take into account up to five conflicting dips at each sample. Here, we propose a strategy which considers all possible angles and, thus, accounts for all the conflicting dips that may exist at one sample. This strategy has some advantages that improve the continuity of reflection events as well as diffractions in the presence of conflicting dip situations. It also generally emphasizes diffraction events in the stacked section such that we may call it common-diffraction-surface stack. Here, we processed the Sigsbee 2A synthetic data and a real land data set with the new method. The stacked result of Sigsbee 2A and the results of the poststack depth migration of the real data also proved that the stacked section of the CDS stack is a suitable input for migration.

    • Using Singular Spectrum Analysis and Autoregressive Methods for Improvement of Temporal Resolution of Seismic Data

      https://doi.org/10.3997/2214-4609.20145890

      One of the goals of seismic processing is to improve the temporal resolution of seismic data. Seismic data usually have not enough temporal resolution because of band-limited nature of source signatures. In this paper we introduce a method in which we extrapolate deconvolved seismic spectrum for recovery of missed frequencies. The introduced method takes a certain part of both real and imaginary parts of the spectrum, where S/N is high compare to the rest of the spectrum, and extrapolates lower and higher portions of the spectrum using Singular Spectrum Analysis (SSA) and Autoregressive model. The selected part of spectrum is decomposed into some principal components. Each principal component has periodic pattern without trend, a narrow band frequency spectrum, and well defined characteristics to be extrapolated. After extrapolation of each principal component, the spectrum is reconstructed by combining the associated extrapolated principal components.

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