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Babasafari A.A.,Oil Exploration Operation Company | Khoshdel H.,Exploration Directorate
6th Saint Petersburg International Conference and Exhibition on Geosciences 2014: Investing in the Future | Year: 2014

Seismic reservoir characterization helps to find more information about rock physics in oil and gas explorations. One of the important properties in reservoirs is hydrocarbon saturation. Fluid content discrimination on seismic data is possible if it is feasible in well data and seismic data has adequate quality. In this study a gas carbonate reservoir is evaluated to map fluid distribution using integration of AVO inversion and seismic attributes. Feasibility study of fluid content discrimination was certified in well data by cross-plotting Acoustic Impedance vs. Vp/Vs logs. AVO modeling represents fluid effect as well. Results of simultaneous pre-stack inversion were used to predict water saturation cube which completely discriminate gas from water around GWC on surface attribute map. By subtracting of far stack from near stack data and applying iso-frequency component attribute over the volume the pay zone was discriminated from non-pay zone around GWC. This was confirmed again by unsupervised facies classification. This field has been already interpreted structurally and depth map of reservoir has been built. The contour level of GWC on depth map somewhere was not coincided in comparison with the observed gas content as demonstrated above. It illustrates that calculated reserve will be increased.(Close to 0.2 STCF). Copyright © 2014 by the European Association of Geoscientists & Engineers. All rights reserved. Source

Karimpouli S.,Amirkabir University of Technology | Hassani H.,Amirkabir University of Technology | Malehmir A.,Uppsala University | Nabi-Bidhendi M.,University of Tehran | Khoshdel H.,Exploration Directorate
Journal of Applied Geophysics | Year: 2013

The South Pars, the largest gas field in the world, is located in the Persian Gulf. Structurally, the field is part of the Qatar-South Pars arch which is a regional anticline considered as a basement-cored structure with long lasting passive folding induced by salt withdrawal. The gas-bearing reservoir belongs to Kangan and Dalan formations dominated by carbonate rocks. The fracture role is still unknown in gas accumulation and distribution in this reservoir. In this paper, the Scattering Index (SI) and the semblance methods based on scattered waves and diffraction signal studies, respectively, were used to delineate the fracture locations. To find the relation between fractures and gas distribution, desired facies containing the gas, were defined and predicted using a method based on Bayesian facies estimation. The analysis and combination of these results suggest that preference of fractures and/or fractured zones are negligible (about 1% of the total volume studied in this paper) and, therefore, it is hard to conceive that they play an important role in this reservoir. Moreover, fractures have no considerable role in gas distribution (less than 30%). It can be concluded from this study that sedimentary processes such as digenetic, primary porosities and secondary porosities are responsible for the gas accumulation and distribution in this reservoir. © 2013 Elsevier B.V. Source

Karimpouli S.,Amirkabir University of Technology | Hassani H.,Amirkabir University of Technology | Nabi-Bidhendi M.,University of Tehran | Khoshdel H.,Exploration Directorate | Malehmir A.,Uppsala University
Journal of Geophysics and Engineering | Year: 2013

In this study, a carbonate field from Iran was studied. Estimation of rock properties such as porosity and permeability is much more challenging in carbonate rocks than sandstone rocks because of their strong heterogeneity. The frame flexibility factor (γ) is a rock physics parameter which is related not only to pore structure variation but also to solid/pore connectivity and rock texture in carbonate reservoirs. We used porosity, frame flexibility factor and bulk modulus of fluid as the proper parameters to study this gas carbonate reservoir. According to rock physics parameters, three facies were defined: favourable and unfavourable facies and then a transition facies located between these two end members. To capture both the inversion solution and associated uncertainty, a complete implementation of the Bayesian inversion of the facies from pre-stack seismic data was applied to well data and validated with data from another well. Finally, this method was applied on a 2D seismic section and, in addition to inversion of petrophysical parameters, the high probability distribution of favorable facies was also obtained. © 2013 Sinopec Geophysical Research Institute. Source

Khazaiefar A.,University of Shahrood | Nejati Kalateh A.,University of Shahrood | Roshandel Kahoo A.,University of Shahrood | Allahverdi Meigouni F.,Exploration Directorate
Journal of the Earth and Space Physics | Year: 2015

There are various approaches for depth estimation of anomalous potential field data. Spectral analysis of gravity and magnetic data has been used extensively for many years to derive the depth to certain geological structures, such as the magnetic basement or the Curie temperature isotherm. The interpretation of the gravity and magnetic data is preferred in frequency domain because of simple relation between various source models and fields. The estimation of the depth of anomalous sources is usually carried out by Spector and Grant method and its variants in frequency domain. This method, which assumes a uniform distribution of parameters for an ensemble of magnetized blocks, leads to a depth-dependent exponential rate of the decay. In the frequency domain, geophysical source parameters have been assumed as uncorrelated and randomly distributed. Assumption of the uncorrelated random sources is not true as revealed from many borehole data in the German continental deep drilling project (KTB) around the globe. Susceptibility data of pilot hole is analyzed and its power spectrum shows a generalized behavior. Therefore, the generalized spectral method for gravity and magnetic data, based on the realistic distribution of anomalous sources, is found useful for finding the depth values and statistical properties of the source distribution. The scaling spectral method has been applied in many parts of the world. An important aspect of this method is that the scaling properties of the source distributions are related to the scaling properties of the fields in a general way. This relationship can be used to derive information on local geology. A technique to estimate the depth to anomalous sources from the generalized power spectra of magnetic profiles is presented. The power spectrum corresponding to low wavenumber may be dominated by scaling properties alone rather than the depth values. If the logarithm of obtained power spectrum of potential field data that transformed in Fourier domain, is plotted versus wave number values, although some factors affect the plot, but the depth is a dominant factor. The depth various source is thus found from the slope of this plot. If there is more than one ensemble, the slope at smaller frequencies gives the depth to deeper sources, and subsequent slopes at higher frequencies give the depth of shallower source. The depth values calculated by this method are close to the realistic values. To test the reliability of any technique it is necessary for the technique to be tested on the synthetic data. In present research work, the efficiency of generalized power spectrum has been investigated using theoretical model of magnetic and the results have been compared with commonly power spectrum. At the end the generalized power spectrum method has performed well in the depth estimation of anomalous sources of magnetic data acquired on polymetal deposit of Oshvand located in Hamedan Province and the results compared with the commonly power spectrum, IP and RS methods. Based on the previous studies conducted in the area, our estimation of the depth of anomalous sources by means of generalized power spectrum approach has been evaluated and confirmed. Source

Karimpouli S.,University of Zanjan | Malehmir A.,Uppsala University | Hassani H.,Amirkabir University of Technology | Khoshdel H.,Exploration Directorate | Nabi-Bidhendi M.,University of Tehran
Journal of Geophysics and Engineering | Year: 2015

Abstract Diffraction arrivals are important data that have increasingly been used to delineate the sources of diffractors and to explore subsurface discontinuities. In prestack data, diffractions are both zero- and non-zero offset hyperbolas while reflections are only zero-offset hyperbolas. An iterative algorithm using an apex-shifted Radon transform (ASRT) approach is presented in this paper that uses the diffraction hyperbolic trajectory similar to that of prestack time migration in order to locate diffractors and to estimate their corresponding background velocities. Because diffraction energy is generally weak in seismic data and particularly in prestack data, noise attenuation and edge enhancement methods are applied on the instantaneous phase of the seismic data instead of the amplitude data. This means that the phase data are input to the ASRT algorithm. The method is then tested on two synthetic datasets (a point-diffraction model with randomly distributed diffractors and the 2D BP/SEG salt model) and one real data example. Results show that this method can locate the diffractors reasonably well on the rough surfaces of the salt dome and the discontinuities associated with structures such as paleo-channels and faults. Our analysis of the estimated velocities suggests that they are generally valid for diffraction delineation; however, the accuracy of the estimation decreases as background velocity and depth increase. © 2015 Sinopec Geophysical Research Institute. Source

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