Layer | Fill | Outline |
---|
Map layers
Theme | Visible | Selectable | Appearance | Zoom Range (now: 0) |
---|
Fill | Stroke |
---|---|
Collaborating Authors
dispersion
Quantifying the influence of clay-bound water on wave dispersion and attenuation signatures of shale: An experimental study
Long, Teng (University of Houston) | Qin, Xuan (University of Houston) | Wei, Qianqian (University of Houston) | Zhao, Luanxiao (Tongji University) | Wang, Yang (University of Houston) | Chen, Feng (University of Houston) | Myers, Michael T. (University of Houston) | Zheng, Yingcai (University of Houston) | Han, De-Hua (University of Houston)
ABSTRACT Understanding the elastic and attenuation signatures of shales is of considerable interest for unconventional reservoir characterization and sealing capacity evaluation for CO2 sequestration and nuclear waste disposal. We have conducted laboratory measurements on seven shale samples at seismic frequencies (2โ100ย Hz) to study the effects of clay-bound water (CBW) on their wave dispersion and attenuation signatures. With nuclear magnetic resonance and a helium porosimeter, the volume of CBW in the shale samples is quantified. The forced-oscillation measurement reveals that Youngโs modulus exhibits a continuous dispersion trend from 2 to 100ย Hz. The extensional attenuation () shows a weak frequency and pressure dependence on effective pressure ranging from 5 to 35ย MPa. The magnitude of extensional attenuation shows a positive correlation with CBW, with an value of 0.89. It is found that 4% of CBW in the rock frame causes approximately a 5% modulus increase from 2 to 100ย Hz. We adopt a constant model for assigning frequency-dependent bulk and shear moduli to the CBW in the rock-physics modeling, which can fit the experimental data of modulus dispersion and attenuation well, indicating that the bulk and shear moduli of CBW in shales might behave viscoelastically.
- Research Report > New Finding (0.50)
- Research Report > Experimental Study (0.40)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (1.00)
- Geology > Mineral > Silicate (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geophysics > Borehole Geophysics (1.00)
- Geophysics > Seismic Surveying > Seismic Interpretation (0.67)
- North America > United States > New Mexico > San Juan Basin > San Juan Basin Field > Mancos Formation (0.99)
- North America > United States > Colorado > San Juan Basin > San Juan Basin Field > Mancos Formation (0.99)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Shale gas (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Open hole/cased hole log analysis (1.00)
Analytical solutions for dispersions and waveforms of acoustic logging in a cased hole
Wang, Hua (University of Electronic Science and Technology of China, University of Electronic Science and Technology of China) | Liu, Tianlin (University of Electronic Science and Technology of China) | Ji, Yunjia (University of Electronic Science and Technology of China)
Acoustic logging is one of the most promising methods for the quantitative evaluation of cement bond conditions in cased holes. However, inefficient utilization of full-wave information yields unsatisfactory interpretation accuracy. Fundamentally, this is because the wavefield characteristics have not been thoroughly investigated under various cement bonding conditions. Thus, this study derives analytical solutions of wavefields for a single-cased-hole model and emphasizes on the dispersion calculation algorithm. To solve the dispersion equation when solving for the poles of the propagating modes with real wavenumbers, we renormalize the Bessel function related to the borehole fluid by multiplying it with an attenuation factor. For leaky modes with complex wavenumbers, we propose a novel method to find peaks of the matrix condition number (LPMCN) in the frequency domain to determine dispersion poles, avoiding the local optimization issues resulting from the traditional GaussยNewton iteration method. Combining these two methods, we establish a fast and accurate workflow for evaluating the dispersion of all modes in cased holes using a relatively fast bisection method to manage the dispersion of the propagating modes and employing the LPMCN method to derive dispersion curves of leaky modes. Furthermore, all propagating modes are individually investigated in the monopole measurement by evaluating residues of the real poles in a casing-free model. The analysis demonstrates that the first-order pseudo-Rayleigh wave (PR1) and inner Stoneley wave (ST1) are the two strongest modes. Finally, we focus on the waveforms and dispersion characteristics of the outer Stoneley wave (ST2) related to the fluid channel in the cement annulus. The results reveal that as the fluid thickness increases the phase velocity of the ST2 mode decreases, while its amplitude increases. Therefore, the ST2 mode can potentially evaluate the thickness of the fluid channel in a cement annulus if an effective weak-signal-extraction method is utilized.
- Geophysics > Borehole Geophysics (1.00)
- Geophysics > Seismic Surveying > Seismic Processing (0.46)
Dispersion distorts the shape of a wavetrain; peaks and troughs advance toward (or recede from) the beginning of the wave as it travels. Leads to the concept of group velocity U distinct from phase velocity V. Where Failed to parse (SVG with PNG fallback (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") The dispersion of seismic body waves is very small under most circumstances, but surface waves may show appreciable dispersion in the presence of near-surface velocity layering. The dispersion of electromagnetic body waves is large in most earth materials.
- Information Technology > Knowledge Management (0.40)
- Information Technology > Communications > Collaboration (0.40)
Determination of the VS profile at a "noisy" industrial site via active and passive data: the critical role of Love waves and the opportunities of multi-component group velocity analysis
Dal Moro, Giancarlo (Academy of Sciences of the Czech Republic) | Mazanec, Martin (Academy of Sciences of the Czech Republic, Charles University)
In order to define the procedures necessary to unambiguously define the subsurface model, a comprehensive set of active and passive seismic data was collected in an industrial area characterized by an extremely-high level of background microtremors. Passive data are recorded to define three observables: the dispersion curve of the vertical component of Rayleigh waves via Miniature Array Analysis of Microtremors (MAAM), the Love-wave dispersion curve via Extended Spatial AutoCorrelation (ESAC) and the Horizontal-to-Vertical Spectral Ratio (HVSR). Active data used for the Holistic analysis of Surface waves (HS) are extracted from data recorded through a hybrid acquisition procedure accomplished with just two 3-component (3C) geophones used also to simultaneously define the HVSR at two points. Defined observables are combined according to three different approaches: the joint analysis of Rayleigh waves and HVSR, the joint analysis of Rayleigh and Love waves together with the HVSR and the joint analysis of multicomponent group velocities together with the HVSR and RPM (Rayleigh-wave Particle Motion) curves. In agreement with the theory, data show that, in general, surface-wave modelling cannot be performed considering modal dispersion curves: dispersion obtained from passive data needs to be modelled considering the effective curve while group-velocity obtained from active data can be analyzed using the Full-Velocity Spectrum (FVS) technique. Results show that joint inversion of Rayleigh-wave dispersion and HVSR does not necessarily ensure the correctness of the obtained shear-wave velocity (VS) profile and that Love waves represent a key observable to fully constrain an unambiguous inversion procedure. On the other hand, the joint analysis of multicomponent group-velocity spectra (from active multicomponent single-offset data) together with the HVSR and RPM curves is a further efficient way to obtain robust VS profiles through the active and passive data obtained by a single 3C geophone.
- Europe (1.00)
- Asia (0.92)
- North America > United States > California (0.45)
- Research Report > Experimental Study (0.48)
- Research Report > New Finding (0.47)
- Geology > Geological Subdiscipline (1.00)
- Geology > Structural Geology > Tectonics > Plate Tectonics (0.46)
- Geology > Sedimentary Geology > Depositional Environment (0.45)
- South America > Colombia > Bogota Basin (0.99)
- Europe > Norway > North Sea > Central North Sea > Central Graben > Block 2/8 > Valhall Field > Tor Formation (0.99)
- Europe > Norway > North Sea > Central North Sea > Central Graben > Block 2/8 > Valhall Field > Hod Formation (0.99)
- (2 more...)
Effect of flow patterns and velocity field on oil-water two-phase flow rate in horizontal wells
Wu, Yuyan (Yangtze University, Yangtze University) | Guo, Haimin (Yangtze University, Yangtze University) | Deng, Rui (Yangtze University, Yangtze University) | Song, Hongwei (Yangtze University, Yangtze University)
ABSTRACT In a wellbore, any change in flow rate will result in a change in flow pattern and velocity. The flow pattern and velocity are the key parameters that determine the pressure gradient and liquid holdup. To study the effect of the flow pattern and velocity field on the flow rate of oil-water flow in horizontal wells, we apply the commercial software package ANSYS Fluent 2020 R2 to predict the flow patterns, water holdups, pressure gradients, flow rates, and velocity fields of horizontal wells. Tralleroโs flow pattern chart and existing experimental data are used to verify the reliability of the model. We develop a simplified mathematical model of water holdup and compare it with existing models. This mathematical model may be limited to the range of fluid properties in the simulated method. The water holdup of the numerical simulation has a definite correlation with the experimental data. By comparing the numerical simulation results of the Nicolas model, the relationship between the slip velocity and water holdup is verified, and the reliability of the simulation results is verified. The simulation results demonstrate that the change in flow pattern is highly sensitive to the change in flow rate. When the flow pattern is stratified flow, the relative error of the simulated flow is small. When the flow pattern is dispersed flow, the relative error of the simulated flow is slightly larger. The oil is mainly concentrated in the high-velocity core area. At a higher total mixing velocity, the flow pattern is that of dispersed flow, with one phase uniformly mixed in the other phase. The simulation results have good qualitative and quantitative agreement with the experimental results.
Improving image resolution using deabsorption prestack time migration with effective Q estimation: A back-propagation network approach
Wu, Jizhong (Northeast Petroleum University) | Shi, Ying (Northeast Petroleum University) | Wang, Weihong (Northeast Petroleum University) | Li, Songling (Northeast Petroleum University) | Yang, Qianqian (Northeast Petroleum University)
ABSTRACT The conventional time migration method does not consider the attenuation caused by the viscoelasticity of the underground media during the imaging process. Therefore, the final imaging amplitude and phase include inaccuracies caused by attenuation. In this study, we develop a migration scheme to compensate for absorption and dispersion using an effective quality factor (Q) estimation based on a back-propagation (BP) neural network. We use BP neural network technology to automatically estimate the effective Q value from stacked imaging data, thereby avoiding manual Q estimation using conventional methods. Our scheme can be incorporated into conventional seismic data-processing workflows. Furthermore, synthetic and field data sets are used to validate our scheme, which is used to acquire high-resolution images with low noise levels. In addition to developing a completely data-driven Q-value estimation strategy, this study demonstrates close integration of artificial intelligence, data mining, and conventional geophysics; our approach is appropriate for estimating the effective Q and has strong industrial application value and significance.
ABSTRACT Seismic waves propagating in fluid-saturated porous rocks exhibit attenuation and velocity dispersion in a broad range of frequencies. At sonic and ultrasonic frequencies, the attenuation is predominantly caused by fluid flow in cracks and grain contacts, so-called squirt flow. This physical mechanism for attenuation also may be relevant at seismic frequencies. We develop a simple and accurate analytical model for attenuation and dispersion caused by squirt flow in isotropic porous rocks. The input material properties for a specific rock model can be directly measured in a laboratory or calculated using analytical and numerical approaches. The results from our squirt flow model are compared with inherently accurate 3D numerical solutions for the same pore geometries. The analytical and numerical results are in good agreement. Furthermore, we observe that our analytical model is more accurate than the currently available analytical solution for squirt flow in isotropic porous rocks. MATLAB routines to reproduce the presented results are made available.
- Europe (0.94)
- North America > United States > Massachusetts (0.28)
Q-compensated wavefield depth extrapolation-based migration using a viscoacoustic wave equation
You, Jiachun (Chengdu University of Technology) | Liu, Wei (Chengdu University of Technology) | Huang, Xingguo (Jilin University) | Xue, Yajuan (Chengdu University of Information Technology) | Cao, Junxing (Chengdu University of Technology)
ABSTRACT In a viscoacoustic medium, intrinsic attenuation causes seismic wavefields to attenuate in amplitude and become dispersed in phase, leading to distorted structural imaging and inaccurate migrated amplitudes. To address this problem, viscoacoustic reverse time migration corrects for dispersion and amplitude attenuation effects in wavefield propagation in forward and backward directions. To provide a parallel alternative approach, the time fractional derivative viscoacoustic wave equation in the depth domain is solved and a Q-compensated wavefield depth extrapolation scheme is established to compensate for viscoacoustic effects during recursive wavefield depth extrapolation. This approach decouples the amplitude attenuation and phase dispersion effects from the viscoacoustic vertical wavenumber. To suppress high wavenumber components and address the problem of exponential amplitude growth during wavefield depth extrapolation, we limit the imaginary part of the vertical wavenumber in the frequency wavenumber domain and use an adaptive stabilization solution. Numerical experiments of impulse responses in a viscoacoustic isotropic medium demonstrate that our proposed scheme can observe calculated wavefields exhibiting amplitude attenuation and phase dispersion effects in comparison to wavefields of the acoustic medium, indicating good agreement with theoretical expectations. We also demonstrate the capability of our proposed scheme to recover imaging amplitudes through a variety of numerical experiments, such as imaging of three-layer, Marmousi, and BP gas reservoir models. The results indicate that our proposed scheme can recover amplitude attenuation and phase dispersion effects more accurately than acoustic migration. We also use marine seismic data featuring natural gas hydrates to indicate that our proposed Q-compensated scheme can generate an enhanced imaging result, especially for the bottom simulating reflectors, compared with the conventional imaging algorithm without Q-compensation.
- Asia > China (0.47)
- North America > United States > Illinois > Madison County (0.34)
Improving image resolution using deabsorption prestack time migration with effective Q estimation: A back-propagation network approach
Wu, Jizhong (Northeast Petroleum University) | Shi, Ying (Northeast Petroleum University) | Wang, Weihong (Northeast Petroleum University) | Li, Songling (Northeast Petroleum University) | Yang, Qianqian (Northeast Petroleum University)
ABSTRACT The conventional time migration method does not consider the attenuation caused by the viscoelasticity of the underground media during the imaging process. Therefore, the final imaging amplitude and phase include inaccuracies caused by attenuation. In this study, we develop a migration scheme to compensate for absorption and dispersion using an effective quality factor (Q) estimation based on a back-propagation (BP) neural network. We use BP neural network technology to automatically estimate the effective Q value from stacked imaging data, thereby avoiding manual Q estimation using conventional methods. Our scheme can be incorporated into conventional seismic data-processing workflows. Furthermore, synthetic and field data sets are used to validate our scheme, which is used to acquire high-resolution images with low noise levels. In addition to developing a completely data-driven Q-value estimation strategy, this study demonstrates close integration of artificial intelligence, data mining, and conventional geophysics; our approach is appropriate for estimating the effective Q and has strong industrial application value and significance.
PUC-Rio Summary The success of an oilwell drilling operation is directly associated with the correct formulation of drilling fluids and their rheological measurements. The goal of this study is to investigate the usage of a Fann 35A viscometer and the methodology for rheological characterization of drilling fluids by comparison with the use of a rotational rheometer. Flow curves and gel strength tests were performed considering classic measurement artifacts such as apparent wall slip, secondary flows, steady-state (SS) regime, and inertial effects, among others. In addition, a study of the relationship between pressure drop and flow rate in a tube and in an annular space was carried out to investigate the influence of the viscosity function and of the rheological properties on the design of pipelines and the correct sizing of pumps. Use of American Petroleum Institute (API) equations and curve fitting were explored as potential choices for viscosity functions. The results indicate that the use of API equation predictions can compromise the effectiveness of the drilling process, while the choice of an adequate viscosity function is essential for the correct sizing of pumps. The gel strength was evaluated in the viscometer and presented divergent results from those obtained in the rheometer. Furthermore, a grooved geometry was developed for the viscometer to avoid the effects of apparent slip at low shear rates. Some recommendations are made based on the results obtained, which lead to better accuracy in the rheological results of drilling fluids and, consequently, better performance of some functions assigned to it. The proposed improvements and methodologies proved to be promising, although in some cases the cost-benefit remained unchanged. Introduction The main functions of a drilling fluid are cleaning the hole, carrying the cuttings to the surface, and maintaining the downhole hydrostatic pressure and stability of the wellbore. To accomplish these functions, rheological properties, density, lubricity, and pH need to be measured and controlled in the field (Bourgoyne et al. 1986). However, these fluids present complex non-Newtonian behavior, so obtaining their rheological properties is not a trivial task.