The Experts below are selected from a list of 18300 Experts worldwide ranked by ideXlab platform
Morten Jakobsen - One of the best experts on this subject based on the ideXlab platform.
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Seismic Characterization of Reservoirs with Multiple Fracture Sets Using Velocity and Attenuation Anisotropy Data
73rd EAGE Conference and Exhibition incorporating SPE EUROPEC 2011, 2011Co-Authors: Aamir Ali, Morten JakobsenAbstract:The successful management of Fractured reservoirs depends upon improved characterization of Fractured systems which often provide pathways for fluid flow during production. Knowledge about spatial distribution of Fracture density and azimuthal Fracture Orientation can greatly help in optimizing production from Fractured reservoirs. Frequency dependent measurements of seismic anisotropy or seismic velocity and attenuation can potentially give important information about the Fractures present in the reservoir. In this study, we use frequency dependent velocity and attenuation data to infer information about the multiple Fracture sets present in the reservoir. We model a reservoir containing two sets of Fractures oriented in different directions characterized by unknown azimuthal Fracture Orientations and Fracture densities. The method is based on a viscoelastic T-matrix approach and a Bayesian method of inversion that provides information about uncertainties as well as the mean values. We then try to estimate the unknown azimuthal Fracture Orientations and Fracture densities from velocity and attenuation data as a function of frequency and azimuth. Our synthetic example shows that velocity data alone cannot recover the unknown Fracture parameters. It also shows how joint inversion of velocity and attenuation data greatly reduces the uncertainty in the unknown Fracture parameters.
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characterization of Fractured reservoirs using a consistent stiffness permeability model focus on the effects of Fracture aperture
Geophysical Prospecting, 2011Co-Authors: Ali Shahraini, Aamir Ali, Morten JakobsenAbstract:In this paper we propose a method for the characterization of naturally Fractured reservoirs by quantitative integration of seismic and production data. The method is based on a consistent theoretical frame work to model both effective hydraulic and elastic properties of Fractured porous media and a (non-linear) Bayesian method of inversion that provides information about uncertainties as well as mean (ormaximum likelihood) values. We model a Fractured reservoir as a porous medium containing a single set of vertical Fractures characterized by an unknown Fracture density, azimuthal Orientation and aperture. We then look at the problem of Fracture parameter estimation as a non-linear inverse problem and try to estimate the unknown Fracture parameters by joint inversion of seismic amplitude versus angle and azimuth data and dynamic production data. Once the Fracture parameters have been estimated the corresponding effective stiffness and permeability tensors can be estimated using consistent models. A synthetic example is provided to clearly explain and test the workflow. It shows that seismic and production data complement each other, in the sense that the seismic data resolve a non-uniqueness in the Fracture Orientation and the production data help to recover the true Fracture aperture and permeability, because production data are more sensitive to the Fracture aperture than the seismic data.
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Seismic characterization of reservoirs with multiple Fracture sets using velocity and attenuation anisotropy data
Journal of Applied Geophysics, 2011Co-Authors: Aamir Ali, Morten JakobsenAbstract:Abstract Knowledge about the spatial distribution of the Fracture density and the azimuthal Fracture Orientation can greatly help in optimizing production from Fractured reservoirs. Frequency-dependent seismic velocity and attenuation anisotropy data contain information about the Fractures present in the reservoir. In this study, we use the measurements of velocity and attenuation anisotropy data corresponding to different seismic frequencies and azimuths to infer information about the multiple Fracture sets present in the reservoir. We consider a reservoir model with two sets of vertical Fractures characterized by unknown azimuthal Fracture Orientations and Fracture densities. Frequency-dependent seismic velocity and attenuation anisotropy data is computed using the effective viscoelastic stiffness tensor and solving the Christoffel equation. A Bayesian inversion method is then applied to measurements of velocity and attenuation anisotropy data corresponding to different seismic frequencies and azimuth to estimate the azimuthal Fracture Orientations and the Fracture densities, as well as their uncertainties. Our numerical examples suggest that velocity anisotropy data alone cannot recover the unknown Fracture parameters. However, an improved estimation of the unknown Fracture parameters can be obtained by joint inversion of velocity and attenuation anisotropy data.
Ian D Gates - One of the best experts on this subject based on the ideXlab platform.
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effect of gap and flow Orientation on two phase flow in an oil wet gap relative permeability curves and flow structures
International Journal of Multiphase Flow, 2013Co-Authors: Saeed Shad, Brij B Maini, Ian D GatesAbstract:Abstract Naturally Fractured reservoirs contain about 25–30% of the world supply of oil. In these reservoirs, Fractures are the dominant flow path. Therefore, a good understanding of transfer parameters such as relative permeability as well as flow regimes occurring in a Fracture plays an important role in developing and improving oil production from such complex systems. However, in contrast with gas–liquid flow in a single Fracture, the flow of heavy oil and water has received less attention. In this research, a Hele-Shaw apparatus was built to study the flow of water in presence of heavy oil and display different flow patterns under different flow rates and analyze the effect of Fracture Orientations on relative permeability curves as well as flow regimes. The phase flow rates versus phase saturation results were converted to experimental relative permeability curves. The results of the experiments demonstrate that, depending on Fracture and flow Orientation, there could be a significant interference between the phases flowing through the Fracture. The results also reveal that both phases can flow in both continuous and discontinuous forms. The relative permeability curves show that the oil–water relative permeability not only depends on fluid saturations and flow patterns but also Fracture Orientation.
J J S De Figueiredo - One of the best experts on this subject based on the ideXlab platform.
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on the source frequency dependence of Fracture Orientation estimates from shear wave transmission experiments
Journal of Applied Geophysics, 2015Co-Authors: Leo K Santos, J J S De Figueiredo, Bode Omoboya, Jorg Schleicher, Robert R Stewart, Nikolay DyaurAbstract:Abstract Shear-wave propagation through anisotropic Fractured or cracked media can provide valuable information about these Fracture swarms and their Orientations. The main goal of this work is to recover information about Fracture Orientation based on the shear waveforms (S-waveforms). For this study, we carried out ultrasonic S-wave measurements in a synthetic physical model made of epoxy resin (isotropic matrix proxy), with small cylindrical rubber strips as inclusions (artificial cracks) inserted in it to simulate a homogeneous anisotropic medium. In these experiments, we used low, intermediate, and high frequency shear-wave sources, with frequencies 90, 431, and 840 kHz. We integrated and interpreted the resulting S-wave seismograms, cross-correlation panels and anisotropic parameter-analysis curves. We were able to estimate the crack Orientation in single-Orientation Fracture zones. The high frequency peaks associated with scattered S-waves provided interpretable information about the Fracture Orientations when the propagation direction was parallel to the Fracture plane. The analysis was possible utilizing results from frequency-versus-polarization-angle curves. Moreover, we applied a bandpass filtering process to the intermediate and high frequency seismograms in order to obtain low frequency seismograms. A spectral analysis using frequency–wavenumber (F–K) spectra supports this filtering process. The results obtained using an analysis of cross-correlograms and the Thomsen parameter γ extracted from filtered high-frequency data were quite similar to those obtained using a low-frequency source. This highlighted the possibility of using less expensive high-frequency sources to recover information about the Fracture set.
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estimating Fracture Orientation from elastic wave propagation an ultrasonic experimental approach
Journal of Geophysical Research, 2012Co-Authors: J J S De Figueiredo, Jorg Schleicher, Robert R Stewart, Nikolay DyaurAbstract:[1] Elastic-wave propagation in Fractured and cracked media depends on the dominant spatial Orientation of the discontinuities. Consequently, compressional and shear-wave velocities can give valuable information about the Orientation of the cracks. The main goal of this work is to estimate the preferential Fracture Orientation based on an analysis of cross-correlated S-wave seismograms and Thomsen parameters. For this purpose, we analyzed ultrasonic measurements of elastic (P and S) waves in a physical-modeling experiment with an artificially anisotropic cracked model. The solid matrix of the model consisted of epoxy-resin; small rubber strips simulate cracks with a compliant fill. The anisotropic cracked model consists of three regions, each with a different Fracture Orientation. We used the rotation of the S-wave polarizations for a cross-correlation analysis of the Orientations, and P- and S-wave measurements to evaluate the weak anisotropic parametersγ and e.The shear and compressional wave sources had dominant frequencies of 90 kHz and 120 kHz. These frequencies correspond to long wavelengths compared to the spacing between layers, indicating a nearly effective-media behavior. Integrating the results from cross-correlation with anisotropic parameter analysis, we were able to estimate the Fracture Orientation in our anisotropic cracked physical model. Theγparameter showed good agreement with the cross-correlation analysis and, beyond that, provided additional information about the crack Orientation that cross-correlation alone did not fully resolve. Moreover, our results show that the shear waves are much more strongly influenced by, and can thus contain more information about, crack Orientation than compressional waves.
Daniel R Burns - One of the best experts on this subject based on the ideXlab platform.
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reservoir Fracture characterization from seismic scattered waves
Geophysical Journal International, 2014Co-Authors: Xinding Fang, Michael Fehler, Zhenya Zhu, Yingcai Zheng, Daniel R BurnsAbstract:The measurements of Fracture parameters, such as Fracture Orientation, Fracture density and Fracture compliance, in a reservoir is very important for field development and exploration. Traditional seismic methods for Fracture characterization include shear wave birefringence (Gaiser and Dok, 2001; Dok et al., 2001; Angerer et al., 2002; Vetri et al., 2003) and amplitude variations with offset and azimuth (AVOA) (Ruger, 1998; Shen et al., 2002; Hall et al., 2003; Liu et al., 2010; Lynn et al., 2010). These methods are based on the equivalent medium theory with the assumption that Fracture dimension and spacing are small relative to the seismic wave length, so a Fracture zone behaves like an equivalent anisotropic medium. But Fractures on the order of seismic wave length are also very important for enhanced oil recovery, and they are one of the important subsurface scattering sources that generate scattered seismic waves. Willis et al. (2006) developed the Scattering Index method to extract the Fracture scattering characteristics by calculating the transfer funtion of a Fracture zone. Fang et al. (2011) proposed a modification of the SI method (the Fracture Transfer Function (FTF) method) that leads to a more robust Fracture characterization. In this paper, we use both laboratory data and field data to explore the capability of the FTF method.
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a robust method for Fracture Orientation and density detection from seismic scattered energy
2011Co-Authors: Xinding Fang, Michael Fehler, Tianrun Chen, Daniel R BurnsAbstract:The measurements of Fracture parameters, such as Fracture Orientation, Fracture density and Fracture compliance, in a reservoir is very important for field development and exploration. Traditional seismic methods for Fracture characterization include shear wave birefringence (Gaiser and Dok, 2001; Dok et al., 2001; Angerer et al., 2002; Vetri et al., 2003) and amplitude variations with offset and azimuth (AVOA) (Ruger, 1998; Shen et al., 2002; Hall et al., 2003; Liu et al., 2010; Lynn et al., 2010). These methods are based on the equivalent medium theory with the assumption that Fracture dimension and spacing are small relative to the seismic wave length, so a Fracture zone behaves like an equivalent anisotropic medium. But Fractures on the order of seismic wave length are also very important for enhanced oil recovery, and they are one of the important subsurface scattering sources that generate scattered seismic waves. Willis et al. (2006) developed the Scattering Index method to extract the Fracture scattering characteristics by calculating the transfer funtion of a Fracture zone. This method has two sources of uncertainty: (1) calculation of the transfer function is sensitive to the analysis time window; (2) the interpretation of the transfer function is based on the assumption that the background reflectivity of the medium is white. Here we propose a modification of the SI methods that addresses these issues and leads to a more robust Fracture characterization.
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Fracture spacing and Orientation estimation from spectral analyses of azimuth stacks
Seg Technical Program Expanded Abstracts, 2005Co-Authors: Laura Vetri, Daniel R Burns, Mark E Willis, Rama V N Rao, Nafi M ToksozAbstract:Discrete, vertically aligned Fracture systems impart one or more notches in the spectral ratios of stacked reflected seismic traces. This apparent attenuation is due to the azimuth dependant scattering introduced by the Fractures. The most prominent notch is located at the frequency where the P wavelength is about twice the Fracture spacing. The frequency location of the notches can be used to determine the Fracture spacings. Azimuth stacks with an Orientation parallel to the Fractures tend not show these spectral notches – allowing for another way to detect the Fracture Orientation. An analysis of the vertical component of the 3D, ocean bottom cable seismic survey data from the Emilio field, offshore Italy, shows a prominent set of Fractures with a spacing of about 30 to 40 meters with Orientations that agree with previous studies.
Longgang Tian - One of the best experts on this subject based on the ideXlab platform.
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estimation of Fracture Orientation distributions from a sampling window based on geometric probabilistic method
Rock Mechanics and Rock Engineering, 2021Co-Authors: Qi Zhang, Xiaojun Wang, Longgang TianAbstract:Accurate Orientation distributions are crucial to generating a reliable discrete Fracture network (DFN) model for rock mass, while conventional one-dimensional (1D) and two-dimensional (2D) observation data have significant sampling bias. The study proposes a complete analytical method for estimating the Orientation distributions of three-dimensional (3D) Fractures in rock mass in conjunction with trace statistics in a sampling window, which is suitable for most continuous distributions by reducing the sampling bias. Traces are divided into three categories to derive the geometric probabilistic relationships between 2D trace statistics and 3D Fracture Orientation distributions. The moment estimation, number estimation, and normalization error functions are derived, and the distribution parameters are determined by minimizing the total error function. The proposed method is compared with the Terzaghi family methods and validated by multiple sets of stochastic Fracture networks with different Orientation distributions and sampling windows generated by the Monte Carlo method. The results indicate that the estimated continuous Orientation distributions subjected to the error functions from a large single sampling window are well matched with the true distributions after removing the number estimation error functions of trace samples fewer than 20. Daxiagu tunnel is selected as a case study and the distributions estimated by the proposed method are more coincident with the field observation than those fitted by the Orientations of the rock outcrops on the excavation face.
