Azimuthal anisotropy in<i>P</i>-wave 3-D (multiazimuth) data

Lynn, Heloise B.; Simon, Karen M.; Bates, C. Richard; Dok, Richard Van

doi:10.1190/1.1437392

Cited by 66 publications

(27 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…They found small, but definite stacking velocity anisotropy, which was consistent with Chen's results and the known fracture trend. Similar results have been reported elsewhere by Blackhawk Geosciences (1995), Lynn et al (1996), Craft et al (1997), and others.…”

Section: P-wave Stacking Velocity Anisotropysupporting

confidence: 80%

“…For example, Alford (1986), Willis (1986), Mueller (1991), Winterstein, (1992, Chen (1995), Lynn et al (1996), Corrigan et al (1996) and [among others] measured shear wave splitting travel time differences in surface seismic shear-wave surveys. Beydoun et al, 1985, Crampin et al, 1986, Johnston, 1986Rizer, 1990, and [among others] used shear wave splitting in multicomponent VSPs as an indicator of fractures.…”

Section: Shear Wave Splitting Travel Time Differencesmentioning

confidence: 99%

See 1 more Smart Citation

Multi-Attribute Seismic/Rock Physics Approach to Characterizing Fractured Reservoirs

Mavko¹

2000

View full text Add to dashboard Cite

JUSTIFICATIONDuring Phase I, we performed our rock physics, geologic, and seismic feasibility analysis for fracture characterization. We addressed the problem of seismic fracture detection and characterization, in general, and specifically at our field site in West Texas. In this analysis, we were able to implement a number of fracture modeling procedures and to quantitatively assess the theoretical detectability of reservoir fractures. This allowed us to identify which of the several seismic attributes are most likely to be useful for fracture detection at the site. One of our results showed that Thomsen's parameters should be very useful for indicating gas-filled fractures at the site. We also outlined Monte Carlo approaches that can be applied for feasibility analysis at any site.Prior to our study, most seismic fracture detection methods have focused on qualitatively detecting seismic anisotropy. While anisotropy is critical, when used alone it has left us with interpretation ambiguities and nonuniqueness. During Phase 1 of this project, we found that by statistically integrating geologic and seismic information we can develop nontraditional methods for fracture detection. For example, we found that quantifying the correlations between fracture occurrence and depositional environment, and between fracture spacing and layer thickness, we allow us to decrease the uncertainty of fracture interpretation using seismic anisotropy. One of the reasons for this is that different depositional environments (and rock facies) give rise to differences in their seismic signatures (impedances, velocities, and Poisson's ratio.Phase II will allow us to validate and improve these methodologies by carrying out a smallscale field pilot study. Taking methods to the field, always allows us to make them more applicable. In the field, we will be able to more accurately assess the uncertainties introduced by measurement noise, source and receiver response, coupling, and near surface acoustic properties. We can then more realistically develop ways to reduce the uncertainty, as well as to identify which aspects of the geology and fracture distribution we can characterize most robustly. The small-scale field study will also help us to establish empirical fracture parameters that are needed as inputs to rock physics models. For example, ALL of the effective medium models for fracture-induced anisotropy require fracture stiffness as inputs (these are sometimes characterized as moduli or aspect ratios). There is no realistic way to assign these values DOE FINAL TECHNICAL REPORT ON PHASE 4 theoretically, so being able to calibrate them in a small pilot will give us the critical inputs we need for interpreting the full scale seismic survey in phase III. Finally, the data from the pilot will allow us to add an aspect of "data mining" to the study. In Phase I, we have exploited our best theoretical tools, but the real field data will give us the opportunity to discover other, unpredicted, signatures of fractures that might prove valuable.Our a...

show abstract

Section: P-wave Stacking Velocity Anisotropysupporting

confidence: 80%

Section: Shear Wave Splitting Travel Time Differencesmentioning

confidence: 99%

Multi-Attribute Seismic/Rock Physics Approach to Characterizing Fractured Reservoirs

Mavko¹

2000

View full text Add to dashboard Cite

show abstract

“…Consequently P-wave anisotropy has been extensively studied and is widely used for fracture characterization (e.g. Winterstein 1986;Lynn et al 1996;Rüger 1997;Li 1999). P waves have the potential not only to characterize fractures but also of discriminating between saturating fluids (Rüger & Tsvankin 1997;Bakulin et al 2000).…”

Section: Introductionmentioning

confidence: 99%

Water saturation effects onP-wave anisotropy in synthetic sandstone with aligned fractures

Amalokwu¹,

Chapman²,

Best³

et al. 2015

Geophys. J. Int.

View full text Add to dashboard Cite

S U M M A R YThe seismic properties of rocks are known to be sensitive to partial liquid or gas saturation, and to aligned fractures. P-wave anisotropy is widely used for fracture characterization and is known to be sensitive to the saturating fluid. However, studies combining the effect of multiphase saturation and aligned fractures are limited even though such conditions are common in the subsurface. An understanding of the effects of partial liquid or gas saturation on P-wave anisotropy could help improve seismic characterization of fractured, gas bearing reservoirs. Using octagonal-shaped synthetic sandstone samples, one containing aligned penny-shaped fractures and the other without fractures, we examined the influence of water saturation on P-wave anisotropy in fractured rocks. In the fractured rock, the saturation related stiffening effect at higher water saturation values is larger in the direction across the fractures than along the fractures. Consequently, the anisotropy parameter 'ε' decreases as a result of this fluid stiffening effect. These effects are frequency dependent as a result of wave-induced fluid flow mechanisms. Our observations can be explained by combining a frequency-dependent fractured rock model and a frequency-dependent partial saturation model.

show abstract

“…Recent studies and case histories (Lynn et al, 1996;Corrigan et al, 1996) have shown that wave propagation signatures, including reflection moveout and amplitude-variation-with-offset (AVO), are sensitive to the presence of azimuthal anisotropy. Hake et al (1984) derived the quartic Taylor series term A 4 of t 2 − x 2 reflection-moveout curves for pure modes in TI media with a vertical axis of symmetry.…”

Section: Introductionmentioning

confidence: 99%

Nonhyperbolic Reflection Moveout for Orthorhombic Media

Al-Dajani¹,

Toksöz²

1998

60th EAGE Conference and Exhibition

View full text Add to dashboard Cite

Reflection moveout in azimuthally anisotropic media is not only azimuthally dependent but it is also nonhyperbolic. As a result, the conventional hyperbolic normal moveout (NMO) equation parameterized by the exact NMO (stacking) velocity loses accuracy with increasing offset (i.e., spreadlength). This is true even for a single-homogeneous azimuthally anisotropic layer. The most common azimuthally anisotropic models used to describe fractured media are the horizontal transverse isotropy (HTI) and the orthorhombic (ORT).Here, we introduce an analytic representation for the quartic coefficient of the Taylor's series expansion of the two-way traveltime for pure mode reflection (i.e., no conversion) in arbitrary anisotropic media with arbitrary strength of anisotropy. In addition, we present an analytic expression for the long-spread (large-offset) nonhyperbolic reflection moveout (NHMO). In this study, special attention is given to Pwave propagation in orthorhombic media with horizontal interfaces. The quartic coefficient, in general, has a relatively simple form, especially for shear wave propagation. The reflection moveout for each shear-wave mode in a homogeneous orthorhombic medium is purely hyperbolic in the direction normal to the polarization. In addition, the nonhyperbolic portion of the moveout for shear-wave propagation reaches its maximum along the polarization direction, and it decreases rapidly away from the direction of polarization. Hence, the anisotropy-induced nonhyperbolic reflection moveout for shear-wave propagation is significant in the vicinity of the polarization directions.In multilayered azimuthally anisotropic media, the NMO (stacking) velocity and the quartic moveout coefficient can be calculated with good accuracy using Dix-type averaging (e.g., the known averaging equations for VTI media). The interval NMO velocities and the interval quartic coefficients, however, are azimuthally dependent. This allows us to extend the nonhyperbolic moveout (NHMO) equation, originally designed for VTI media, to more general horizontally stratified azimuthally anisotropic media. Numerical examples from reflection moveout in orthorhombic media, the focus of this paper, show that this NHMO equation accurately describes the azimuthally-dependent P -wave reflection traveltimes, even on spreadlengths twice as large as the reflector depth. This work provides analytic insight into the behavior of nonhyperbolic moveout, and it has important applications in modeling and inversion of reflection moveout in azimuthally anisotropic media.

show abstract

Azimuthal anisotropy inP-wave 3-D (multiazimuth) data

Cited by 66 publications

References 0 publications

Multi-Attribute Seismic/Rock Physics Approach to Characterizing Fractured Reservoirs

Multi-Attribute Seismic/Rock Physics Approach to Characterizing Fractured Reservoirs

Water saturation effects onP-wave anisotropy in synthetic sandstone with aligned fractures

Nonhyperbolic Reflection Moveout for Orthorhombic Media

Contact Info

Product

Resources

About