Effects of fluid-shear resistance and squirt flow on velocity dispersion in rocks

Geophysics ◽  
2015 ◽  
Vol 80 (2) ◽  
pp. D99-D110 ◽  
Author(s):  
Nishank Saxena ◽  
Gary Mavko
Keyword(s):  
Velocity Dispersion ◽  
Seismic Velocity ◽  
Laboratory Data ◽  
Elastic Solid ◽  
High Viscosity ◽  
New Method ◽  
Biot Theory ◽  
Local Flow ◽  
Shear Relaxation ◽  
High Frequency Effects

Laboratory measurements of rocks saturated with high-viscosity fluids (such as heavy-oil, bitumen, magma, kerogen, etc.) often exhibit considerable seismic velocity dispersion, which is usually underestimated by the Biot theory. Over the years, grain-scale dispersion mechanisms such as squirt (local-flow) and shear relaxation (nonzero shear stress in the pore fluid) have been more successful in explaining the measured dispersion. We developed a new method to quantify the combined high-frequency effects of squirt and shear dispersion on the effective moduli of rocks saturated with viscous fluids. Viscous fluid at high frequencies was idealized as an elastic solid of finite shear modulus, hydraulically locked in stiff and soft pores. This method entailed performing solid substitution in stiff pores of a dry rock frame, which itself was unrelaxed due to solid-filled soft pores. The unrelaxed frame stiffness solutions required information on the pressure dependency of the rock stiffness and porosity. This method did not have any adjustable parameters, and all required inputs can be directly measured. With various laboratory and numerical examples, we noted that accounting for combined effects of squirt and shear relaxation was necessary to explain laboratory-measured velocities of rocks saturated with fluids of high viscosity. Predictions of the new method were in good agreement with the laboratory data.

The relation between seismic P‐ and S‐wave velocity dispersion in saturated rocks

Geophysics ◽  
1994 ◽  
Vol 59 (1) ◽  
pp. 87-92 ◽  
Author(s):  
Gary Mavko ◽  
Diane Jizba
Keyword(s):  
Wave Velocity ◽  
Large Scale ◽  
Velocity Dispersion ◽  
Seismic Velocity ◽  
Ultrasonic Velocities ◽  
S Wave ◽  
Local Flow ◽  
Wave Velocities ◽  
Shear Compliance

Seismic velocity dispersionin fluid-saturated rocks appears to be dominated by tow mecahnisms: the large scale mechanism modeled by Biot, and the local flow or squirt mecahnism. The tow mechanisms can be distuinguished by the ratio of P-to S-wave dispersions, or more conbeniently, by the ratio of dynamic bulk to shear compliance dispersions derived from the wave velocities. Our formulation suggests that when local flow denominates, the dispersion of the shear compliance will be approximately 4/15 the dispersion of the compressibility. When the Biot mechanism dominates, the constant of proportionality is much smaller. Our examination of ultrasonic velocities from 40 sandstones and granites shows that most, but not all, of the samples were dominated by local flow dispersion, particularly at effective pressures below 40 MPa.

A New Method for Calculating the Inflection Point Temperature of Heavy-Oil Rheology Transforming from Non-Newton Fluid into the Newton Fluid

2021 ◽  
pp. 1-16
Author(s):  
Dong Liu ◽  
Yonghui Liu ◽  
Nanjun Lai ◽  
Youjun Ji ◽  
TingHui Hu
Keyword(s):  
Newtonian Fluid ◽  
Heavy Oil ◽  
Inflection Point ◽  
High Viscosity ◽  
Current Approach ◽  
Temperature Data ◽  
New Method ◽  
Good Correspondence ◽  
Point Temperature ◽  
Shengli Oilfield

Abstract The inflection point temperature of rheology (IPTR) of heavy oil transforming from a non-Newtonian fluid into a Newtonian fluid is a key parameter in the steam huff- and-puff process. It is particularly relevant in terms of optimizing injection parameters, calculating the heating radius, and determining well spaces. However, the current approach exhibits obvious shortcomings, such as the randomness of the selected tangent line and inadaptability for extra-heavy oil with high viscosity. Therefore, this paper presents a novel method for calculating IPTR using viscosity–temperature data. The approach is based on the Arrhenius equation and quantitatively evaluates the IPTR according to the inflection point of the apparent activation energy. The IPTR values of four heavy-oil samples obtained from the Bohai Oilfield in China were quantitatively predicted according to viscosity–temperature data using the proposed method. The method's accuracy was verified by a series of rheological investigations on samples obtained from two heavy-oil wells. Additionally, the new method was used to predict IPTR according to the published viscosity–temperature data of 10 heavy-oil samples from the Shengli Oilfield. Again, a good correspondence was found, and mean absolute and relative errors of 3°C and 4.6%, respectively, were reported. Therefore, the proposed model was confirmed to improve the prediction accuracy of the existing method, and provided a new method for calculating the IPTR of heavy-oil.

Application of Low-Frequency Energy Increment Technology in Hydrocarbon Prediction

2012 ◽  
Vol 472-475 ◽  
pp. 178-182
Author(s):  
Zhi Ming Li ◽  
Xue Yan Hu ◽  
Ling Xia Zhen
Keyword(s):  
Laboratory Data ◽  
Low Frequency ◽  
Biot Theory ◽  
Hydrocarbon Detection ◽  
Hydrocarbon Prediction ◽  
Phase Medium ◽  
Multi Phase ◽  
Cave Detection ◽  
Fluid Detection ◽  
Energy Increment

Based on the Biot theory and laboratory data, engineers of LandOcean recently develop a certain technology for hydrocarbon detection in multi-phase medium in order to reduce ambiguity and uncertainty. The sensitivity of the technology is superior to others especially in carbonate pores and cave detection, igneous hydrocarbon prediction and fluid detection of non-well areas. A number of projects and wells drilling proved that this technology is effective and reliable.

Local and global fluid-flow effects on dipole flexural waves

Geophysics ◽  
2020 ◽  
Vol 85 (1) ◽  
pp. D1-D11
Author(s):  
Elliot J. H. Dahl ◽  
Kyle T. Spikes
Keyword(s):  
Fluid Flow ◽  
Low Frequency ◽  
Summation Method ◽  
Sensitivity Analyses ◽  
Flexural Wave ◽  
Biot Theory ◽  
S Wave ◽  
Local Flow ◽  
Flow Effects ◽  
Wave Induced

Wave-induced fluid flow (WIFF) can significantly alter the effective formation velocities and cause increasing waveform dispersion and attenuation. We have used modified frame moduli from the theory of Chapman together with the classic Biot theory to improve the understanding of local- and global-flow effects on dipole flexural wave modes in boreholes. We investigate slow and fast formations with and without compliant pores, which induce local flow. The discrete wavenumber summation method generates the waveforms, which are then processed with the weighted spectral semblance method to compare with the solution of the period equation. We find compliant pores to decrease the resulting effective formation P- and S-wave velocities, that in turn decrease the low-frequency velocity limit of the flexural wave. Furthermore, depending on the frequency at which the local-flow dispersion occurs, different S-wave velocity predictions from the flexural wave become possible. This issue is investigated through changing the local-flow critical frequency. Sensitivity analyses of the flexural-wave phase velocity to small changes in WIFF parameters indicate the modeling to be mostly sensitive to compliant pores in slow and fast formations.

scholarly journals Pressure Signal Analysis for the Characterization of High-Viscosity Two-Phase Flows in Horizontal Pipes

2020 ◽  
Vol 8 (12) ◽  
pp. 1000
Author(s):  
Lizeth Torres ◽  
José Noguera ◽  
José Enrique Guzmán-Vázquez ◽  
Jonathan Hernández ◽  
Marco Sanjuan ◽  
...  
Keyword(s):  
Mass Flow ◽  
Two Phase Flow ◽  
High Viscosity ◽  
Flow Rate Ratio ◽  
Phase Flow ◽  
Two Phase ◽  
Local Flow ◽  
Horizontal Pipes ◽  
Pressure Time ◽  
Mass Flow Rates

We study a high-viscosity two-phase flow through an analysis of the corresponding pressure signals. In particular, we investigate the flow of a glycerin–air mixture moving through a horizontal pipeline with a U-section installed midway along the pipe. Different combinations of liquid and air mass flow rates are experimentally tested. Then, we examine the moments of the statistical distributions obtained from the resulting pressure time series, in order to highlight the significant dynamical traits of the flow. Finally, we propose a novel correlation with two dimensionless parameters: the Euler number and a mass-flow-rate ratio to predict the pressure gradient in high-viscosity two-phase flow. Distinctive variations of the pressure gradients are observed in each section of the pipeline, which suggest that the local flow dynamics must not be disregarded in favor of global considerations.

Effects of ellipsoidal heterogeneities on wave propagation in partially saturated double-porosity rocks

Geophysics ◽  
2018 ◽  
Vol 83 (3) ◽  
pp. WC71-WC81 ◽  
Author(s):  
Weitao Sun ◽  
Fansheng Xiong ◽  
Jing Ba ◽  
José M. Carcione
Keyword(s):  
Wave Propagation ◽  
Aspect Ratio ◽  
Wave Velocity ◽  
Velocity Dispersion ◽  
Laboratory Data ◽  
P Wave ◽  
Lagrange Equations ◽  
Wave Dissipation ◽  
P Wave Velocity ◽  
The Impact

Reservoir rocks are heterogeneous porous media saturated with multiphase fluids, in which strong wave dissipation and velocity dispersion are closely associated with fabric heterogeneities and patchy saturation at different scales. The irregular solid inclusions and fluid patches are ubiquitous in nature, whereas the impact of geometry on wave dissipation is still not well-understood. We have investigated the dependence of wave attenuation and velocity on patch geometry. The governing equations for wave propagation in a porous medium, containing fluid/solid heterogeneities of ellipsoidal triple-layer patches, are derived from the Lagrange equations on the basis of the potential and kinetic energies. Harmonic functions describe the wave-induced local fluid flow of an ellipsoidal patch. The effects of the aspect ratio on wave velocity are illustrated with numerical examples and comparisons with laboratory measurements. The results indicate that the P-wave velocity dispersion and attenuation depend on the aspect ratio of the ellipsoidal heterogeneities, especially in the intermediate frequency range. In the case of Fort Union sandstone, the P-wave velocity increases toward an upper bound as the aspect ratio decreases. The example of a North Sea sandstone clearly indicates that introducing ellipsoidal heterogeneities gives a better description of laboratory data than that based on spherical patches. The unexpected high-velocity values previously reported and ascribed to sample heterogeneities are explained by varying the aspect ratio of the inclusions (or patches).

Ambient lower mantle structure and composition inferred from seismic tomography, convection models, and geochemistry.

2020 ◽  
Author(s):  
Grace E. Shephard ◽  
John Hernlund ◽  
Christine Houser ◽  
Reidar Trønnes ◽  
Fabio Crameri
Keyword(s):  
Lower Mantle ◽  
Subduction Zones ◽  
Large Scale ◽  
Seismic Velocity ◽  
Seismic Signal ◽  
High Viscosity ◽  
S Wave ◽  
Velocity Models ◽  
Reference Velocity ◽  
Seismic Anomalies

<p>The lower mantle can be grouped into high, low, and average (i.e., ambient) seismic velocity domains at each depth, based on the amplitude and polarity of wavespeed perturbations (% δlnVs, % δlnVp). Many studies focus on elucidating the thermo-chemical and structural origins of fast and slow domains, in particular. Subducted slabs are associated with fast seismic anomalies throughout the mantle, and reconstructed palaeo-positions of Cenozoic to Mesozoic subduction zones agrees with seismically imaged deep slabs. Conversely, slow wavespeed domains account for the two antipodal LLSVPs in the lowermost mantle, which are potentially long-lived features, as well as rising hot mantle above the LLSVPs and discrete mantle plumes. However, low-amplitude wavespeeds (close to the reference velocity models) are often overlooked By comparing multiple P- and S-wave tomographic models individually, and through “vote maps”, we reveal the depth-dependent characteristics and the geometry of ambient structures, and compare them to numerical convection models. The ambient velocity domains may contain early refractory and bridgmantic mantle with elevated Si/(Mg+Fe) and Mg/Fe ratios (BEAMS; bridgmanite-enriched mantle structures). They could have formed by early basal magma ocean (BMO) fractionation during a period of core-BMO exchange of SiO<sub>2</sub> (from core to BMO) and FeO (from BMO to core), or represent cumulates of BMO crystallization with bridgmanite as the liquidus phase. The high viscosity of bridgmanitic material may promote its convective aggregation and stabilise the large-scale, degree-2 convection pattern. Despite its high viscosity, bridgmanitic material, representing a primitive and refractory reservoir for primordial-like He and Ne components, might be entrained in vigorous, deep-rooted plumes. The restriction of a weak seismic signal, ascribed to iron spin-pairing in ferropericlase, to the fast and slow domains, supports the notion that the ambient lower mantle domains are bridgmanitic.</p>

THE DEVELOPMENT OF A NEW METHOD OF SEISMIC VELOCITY DETERMINATION

Geophysics ◽  
1952 ◽  
Vol 17 (3) ◽  
pp. 560-574 ◽  
Author(s):  
F. P. Kokesh
Keyword(s):  
Conventional Method ◽  
Explosive Charge ◽  
Velocity Measurement ◽  
Seismic Velocity ◽  
Seismic Energy ◽  
New Method ◽  
Seismic Velocities ◽  
The Past ◽  
Velocity Information ◽  
Made In

The conventional method of making velocity surveys in bore holes is inherently expensive, time consuming, and inconvenient, and has a tendency towards non‐uniformity of results. With increasing recognition of the importance of seismic velocity information in the evaluation of seismograph data, the attention of geophysicists is turning towards means of overcoming the obstacles standing in the way of obtaining velocity information in greater volume. Considerable interest has recently been aroused in a new method of measuring seismic velocities wherein the explosive charge is placed in the hole and the seismic energy is picked up with multiple detector groups placed on the surface. Experimentation carried on during the past year indicates that the new method is quite workable. Casing perforator guns of the conventional bullet type have given results to depths exceeding 8,000 ft. with complete safety. Some experimentation with primacord as the explosive has given encouragement as a means of increasing the depth at which the method may be used. Substantial improvements have been made in the manner of obtaining the time break. This paper attempts to outline the basic problems of velocities and their measurement and describes the preliminary development that has been done thus far on the new method of velocity measurement.

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