Low frequency model building based on relative impedance inversion to improve the accuracy of pre-stack simultaneous inversion: a case study from R oilfield in Bohai Bay, China

Seismic diffraction waveform energy contains important information about small-scale subsurface elements, and it is complementary to specular reflection information about subsurface properties. Diffraction imaging has been used for fault, pinchout, and fracture detection. Very little research, however, has been carried out taking diffraction into account in the impedance inversion. Usually, in the standard inversion scheme, the input is the migrated data and the assumption is taken that the diffraction energy is optimally focused. This assumption is true only for a perfectly known velocity model and accurate true amplitude migration algorithm, which are rare in practice. We have developed a new approach for impedance inversion, which takes into account diffractive components of the total wavefield and uses the unmigrated input data. Forward modeling, designed for impedance inversion, includes the classical specular reflection plus asymptotic diffraction modeling schemes. The output model is composed of impedance perturbation and the low-frequency model. The impedance perturbation is estimated using the Bayesian approach and remapped to the migrated domain by the kinematic ray tracing. Our method is demonstrated using synthetic and field data in comparison with the standard inversion. Results indicate that inversion with taking into account diffraction can improve the acoustic impedance prediction in the vicinity of local reflector discontinuities.

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Analysis and Design of Damping Circuit Parameters for LCC Valves Based on Broadband Model

Energies ◽

10.3390/en13051059 ◽

2020 ◽

Vol 13 (5) ◽

pp. 1059

Author(s):

Yingjie Tang ◽

Zheren Zhang ◽

Zheng Xu

Keyword(s):

Numerical Optimization ◽

Low Frequency ◽

Parameter Design ◽

Circuit Parameter ◽

Frequency Model ◽

Analysis And Design ◽

Electromagnetic Transient ◽

High Voltage Direct Current ◽

Novel Method

Damping circuits are installed inside the converter valve to limit commutation overshoots. They have significant effects on the valve’s turn-off performances, which should be carefully considered in parameter design. First, the calculation models for the turn-off process are discussed, including the conventional low frequency model and the broadband model. Then, it is found that high-frequency equipment parameters have significant effects on the transient valve voltage, which means that the conventional analytical methods based on low-frequency models is not suitable for damping circuit parameter design. The relationships between the turn-off performances and damping circuit parameters have also been analyzed in detail with the broadband model. To achieve better economic efficiency, this paper proposes a novel method for damping circuit parameter optimization, which combines the electromagnetic transient (EMT) calculation and the numerical optimization. Last, the case study is carried out based on a practical ±1100 kV ultra-high-voltage direct-current (UHVDC) transmission project, which proves the reliability and flexibility of the proposed method.

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Accurate poststack acoustic-impedance inversion by well-log calibration

Geophysics ◽

10.1190/1.3170687 ◽

2009 ◽

Vol 74 (5) ◽

pp. R59-R67 ◽

Cited By ~ 19

Author(s):

Igor B. Morozov ◽

Jinfeng Ma

Keyword(s):

Seismic Data ◽

Acoustic Impedance ◽

Joint Inversion ◽

Low Frequency ◽

Real Data ◽

Data Sets ◽

Frequency Model ◽

Physical Constraints ◽

Impedance Inversion ◽

Reliable Solution

The seismic-impedance inversion problem is underconstrained inherently and does not allow the use of rigorous joint inversion. In the absence of a true inverse, a reliable solution free from subjective parameters can be obtained by defining a set of physical constraints that should be satisfied by the resulting images. A method for constructing synthetic logs is proposed that explicitly and accurately satisfies (1) the convolutional equation, (2) time-depth constraints of the seismic data, (3) a background low-frequency model from logs or seismic/geologic interpretation, and (4) spectral amplitudes and geostatistical information from spatially interpolated well logs. The resulting synthetic log sections or volumes are interpretable in standard ways. Unlike broadly used joint-inversion algorithms, the method contains no subjectively selected user parameters, utilizes the log data more completely, and assesses intermediate results. The procedure is simple and tolerant to noise, and it leads to higher-resolution images. Separating the seismic and subseismic frequency bands also simplifies data processing for acoustic-impedance (AI) inversion. For example, zero-phase deconvolution and true-amplitude processing of seismic data are not required and are included automatically in this method. The approach is applicable to 2D and 3D data sets and to multiple pre- and poststack seismic attributes. It has been tested on inversions for AI and true-amplitude reflectivity using 2D synthetic and real-data examples.

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Improved seismic inversion and reservoir description of the Ichthys gas-condensate field, Browse Basin, Western Australia

The APPEA Journal ◽

10.1071/aj09080 ◽

2010 ◽

Vol 50 (2) ◽

pp. 716

Author(s):

Masamichi Fujimoto ◽

Takeshi Yoshida ◽

Andrew Long

Keyword(s):

Low Frequency ◽

Seismic Inversion ◽

Gas Condensate ◽

Sensor Technology ◽

Frequency Model ◽

Porosity Distribution ◽

Low Frequencies ◽

Simultaneous Inversion ◽

Dual Sensor ◽

Well Data

Seismic inversion has become a standard geophysical tool to enhance seismic resolution, predict the reservoir porosity distribution, and to discriminate between reservoir and non-reservoir pay zones. Conventional seismic data does not record the low frequencies necessary for inversion. To enable a complete bandwidth, low frequencies are modelled from well data and are typically interpolated throughout the volume using seismic velocities. This often causes the resultant porosity distribution calculated from the inverted P-impedance to be biased by the well data and the geometry of well locations. Dual-sensor GeoStreamer technology was used to acquire a regional multi-client 2D survey by PGS in 2008, including some lines over the Ichthys gas-condensate field in the Browse Basin. Dual-sensor streamer processing recovers a wider frequency bandwidth than conventional seismic. Receiver ghost removal combined with deep streamer towing simultaneously boosts both the low and high frequencies. The improved bandwidth enables a higher quality of velocity analysis, which further improves resolution throughout the section. Simultaneous inversion of the data validated the uplift of the low frequency data, and significantly reduced the bias towards well data for the low frequency model. The resultant P-impedance data demonstrated an excellent tie to well data. The dual-sensor technology promises to improve the description of the porosity distribution within our reservoir model.

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An Amplitude-Based Modeling Method and its Application on the Impedance Inversion in Heterogeneous Paleokarst Carbonate Reservoirs

Earth Science Research ◽

10.5539/esr.v5n2p199 ◽

2016 ◽

Vol 5 (2) ◽

pp. 199

Author(s):

Yuanyin Zhang ◽

Zandong Sun ◽

Zhijun Jin ◽

Ning Dong ◽

Yequan Chen ◽

...

Keyword(s):

Tarim Basin ◽

Traditional Method ◽

Low Frequency ◽

Modeling Method ◽

Carbonate Reservoirs ◽

P Wave ◽

Seismic Velocities ◽

Frequency Model ◽

Heterogeneous Reservoirs ◽

Impedance Inversion

For the modeling of complex reservoirs with strong heterogeneity, for instance the deeply buried paleokarst reservoirs in the Tarim Basin, the traditional method by lateral interpolation and extrapolation of measured logs between well locations with the guiding of interpreted seismic horizons is driven by distance and often leads to non-geologic solutions, while the past improvements via adding seismic velocities or attributes information are still not accurate due to the resolution limitation or AVO (amplitude versus offset) effects contamination. In this paper, we present an amplitude-based modeling method by utilizing the heterogeneous information from seismic data to guide the geological model construction, based on the inverted pure P-wave data which have removed the AVO effects. The proposed method is applied in the impedance inversion of the paleokarst carbonate reservoirs in the Tarim Basin, where the reservoirs are characterized by substantial heterogeneity. Both the constructed Low frequency model (LFM) and the inverted impedance results of proposed method are more correlative with drilling data than that of traditional method. This method is more beneficial for strong heterogeneous reservoirs description especially in well insufficient or absent areas, suggested by the comparisons with traditional methods in the ZG8 area.

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Stuck between a rock and a reflection: A tutorial on low-frequency models for seismic inversion

Interpretation ◽

10.1190/int-2016-0150.1 ◽

2017 ◽

Vol 5 (2) ◽

pp. B17-B27 ◽

Cited By ~ 9

Author(s):

Mark Sams ◽

David Carter

Keyword(s):

Elastic Properties ◽

Model Building ◽

Seismic Velocity ◽

Low Frequency ◽

Rock Physics ◽

Frequency Component ◽

Seismic Inversion ◽

Rock Properties ◽

Seismic Velocities ◽

Frequency Model

Predicting the low-frequency component to be used for seismic inversion to absolute elastic rock properties is often problematic. The most common technique is to interpolate well data within a structural framework. This workflow is very often not appropriate because it is too dependent on the number and distribution of wells and the interpolation algorithm chosen. The inclusion of seismic velocity information can reduce prediction error, but it more often introduces additional uncertainties because seismic velocities are often unreliable and require conditioning, calibration to wells, and conversion to S-velocity and density. Alternative techniques exist that rely on the information from within the seismic bandwidth to predict the variations below the seismic bandwidth; for example, using an interpretation of relative properties to update the low-frequency model. Such methods can provide improved predictions, especially when constrained by a conceptual geologic model and known rock-physics relationships, but they clearly have limitations. On the other hand, interpretation of relative elastic properties can be equally challenging and therefore interpreters may find themselves stuck — unsure how to interpret relative properties and seemingly unable to construct a useful low-frequency model. There is no immediate solution to this dilemma; however, it is clear that low-frequency models should not be a fixed input to seismic inversion, but low-frequency model building should be considered as a means to interpret relative elastic properties from inversion.

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