al coordination and speciation in calcium aluminosilicate glasses effects of composition determined by 27al mq mas nmr and raman spectroscopy the structure and properties of glasses and melts in the cao al2o3 sio2 cas system play an important role in earth and material sciences aluminum has a crucial role in this ternary system and its environment is still questioned in this paper we present new results using raman spectroscopy and 27al nuclear magnetic resonance on cas glasses obtained by classic and rapid quenching methods we propose an al si tetrahedral distribution in the glass network in different qn species in this system we show that al and si are mainly in q4 species along the join r cao al2o3 1 and in depolymerized q2 and q3 units at high cao content for other joins r 1 57 and 3 five 5 al and six fold 6 al coordinated aluminum can be detected in the peraluminous glasses r 1 except for glasses with low silica and high cao content the presence of 5 al is related to viscous flow mechanisms while in highly depolymerized glasses the absence of 5 al may indicate different mechanisms for melts to flow this systematic study on the cas system modifies the simple picture of aluminosilicate glasses and the existence of 5 al should be included by geochemists geophysicists and glass scientists to model appropriately the physical properties of aluminosilicate glasses and melts

extent of disorder in iron bearing albite and anorthite melts insights from multi nuclear 29si 27al and 17o solid state nmr study of iron bearing naalsi3o8 and caal2si2o8 glasses abstract knowledge of the detailed structure of iron bearing aluminosilicate glasses is essential to unraveling the effects of iron on the macroscopic properties of natural silicate glasses and melts however the local structures around the framework cations such as al and si and the extent of network polymerization in iron bearing aluminosilicate glasses are not well understood this is mainly because the high resolution solid state nmr one of the effective probes of the structures of aluminosilicate glasses has limited utility in delving into the local configurations of oxide glasses with paramagnetic elements i e iron here we use multi nuclear 29si 27al and 17o high resolution solid state nmr to investigate the effect of iron content on the local structure around framework cations and oxygen species in na al1 xfex si3o8 glasses with varying x fe al fe fe3 fe 0 8 naalsi3o8 glasses with varying fe2o3 naalsi3o8 fe2o3 fe3 fe 0 5 and caal2si2o8 glasses with varying fe2o3 caal2si2o8 fe2o3 fe3 fe 0 3 the nmr results for na al1 xfex si3o8 glasses reveal preferential interaction between fe3 and si rich framework and thus an extensive mixing between 4 si and 4 fe3 the presence of a small amount of 5 al in na al0 5fe0 5 si3o8 glass suggests that the extent of disorder around al increases by al fe3 substitution the nmr results for naalsi3o8 fe2o3 glasses suggest that fe2 interacts more strongly with al rich framework and reveal the presence of a non negligible fraction of na nbo confirming fe2 induced structural disorder the absence of 5 al in naalsi3o8 fe2o3 glasses indicates that fe3 is more likely to form a highly coordinated framework i e 5 fe3 when excess fe3 is added to charge balanced glasses the nmr spectra for caalsi2o8 fe2o3 glasses showed an iron induced increase in the 5 al fraction and confirmed that the overall degree of disorder increases with increasing fe2o3 content the noble nmr results for iron bearing aluminosilicate glasses revealed the nature of diverse aspect of iron induced structural disorder mainly characterized by the intermixing between si and fe3 preferential interaction between al and fe2 and formation of highly coordinated 5 fe3 the detailed iron induced structural evolution is largely dependent on the composition of melts as well as the valence state of iron the observed increase in the extent of structural disorder in charge balanced na and ca aluminosilicate glasses with increasing fe2 and fe3 can account for the iron induced decrease in viscosity of the corresponding iron bearing aluminosilicate melts

efficient method for coupling field data and numerical modeling for the estimation of transverse mixing coefficients in meandering rivers abstracta numerical model has been developed employing an orthogonal stream tube gridding system for the investigation of mixing patterns in meandering rivers the proposed model couples field data and modeling it uses a measured velocity field to solve the advection diffusion equation this equation provides a practical simulation with greater accuracy and lower computational cost for estimation of mixing in meandering channels with a long full mixing length the model has been used to estimate the transverse mixing coefficient in surveyed subreaches of the north saskatchewan river in canada good agreement was observed between the numerical and measured tracer concentrations using reasonable values for the transverse mixing coefficient the average dimensionless transverse mixing coefficient from the calibrated numerical model for the surveyed reach was 0 39 which was consistent with values estimated using empirical formulas for transverse mixing coefficients in natural meandering rivers the estimat

reconstruction of the layer anisotropic elastic parameters and high resolution fracture characterization from p wave data a case study using seismic inversion and bayesian rock physics parameter estimation wide azimuth seismic data can be used to derive anisotropic parameters on the subsurface by observing variation in subsurface seismic response along different azimuths layer based high resolution estimates of components of the subsurface anisotropic elastic tensor can be reconstructed by using wide azimuth p wave data by combining the kinematic information derived from anisotropic velocity analysis with dynamic information obtained from amplitude versus angle and azimuth analysis of wide azimuth seismic data interval p impedance s impedance and anisotropic parameters associated with anisotropic fracture media are being reconstructed using linearized analysis assuming horizontal transverse anisotropy symmetry in this paper it is shown how additional assumptions such as the rock model can be used to reduce the degrees of freedom in the estimation problem and recover all five anisotropic parameters because the use of a rock model is needed the derived elastic parameters are consistent with the rock model and are used to infer fractured rock properties using stochastic rock physics inversion the inversion is based on stochastic rock physics modelling and maximum a posteriori estimate of both porosity and crack density parameters associated with the observed elastic parameters derived from both velocity and amplitude versus angle and azimuth analysis while the focus of this study is on the use of p wave reflection data we also show how additional information such as shear wave splitting and or anisotropic well log data can reduce the assumptions needed to derive elastic parameter and rock properties

constructing a discrete fracture network constrained by seismic inversion data rock fractures are of great practical importance to petroleum reservoir engineering because they provide pathways for fluid flow especially in reservoirs with low matrix permeability where they constitute the primary flow conduits understanding the spatial distribution of natural fracture networks is thus key to optimizing production the impact of fracture systems on fluid flow patterns can be predicted using discrete fracture network models which allow not only the 6 independent components of the second rank permeability tensor to be estimated but also the 21 independent components of the fully anisotropic fourth rank elastic stiffness tensor from which the elastic and seismic properties of the fractured rock medium can be predicted as they are stochastically generated discrete fracture network realizations are inherently non unique it is thus important to constrain their construction so as to reduce their range of variability and hence the uncertainty of fractured rock properties derived from them this paper presents the underlying theory and implementation of a method for constructing a geologically realistic discrete fracture network constrained by seismic amplitude variation with offset and azimuth data several different formulations are described depending on the type of seismic data and prior geologic information available and the relative strengths and weaknesses of each approach are compared potential applications of the method are numerous including the prediction of fluid flow elastic and seismic properties of fractured reservoirs model based inversion of seismic amplitude variation with offset and azimuth data and the optimal placement and orientation of infill wells to maximize production this article is protected by copyright all rights reserved

direct inversion for a fluid factor and its application in heterogeneous reservoirs abstract prestack seismic inversion plays an important role in estimating elastic parameters that are sensitive to reservoirs and fluid underground in this paper a simultaneous inversion method named fmr ava fluid factor mu shear modulus rho density amplitude variation with angle is proposed based on partial angle stack seismic gathers this method can be used for direct inversion for the fluid factor shear modulus and density of heterogeneous reservoirs firstly an fmr approximation equation of a reflection coefficient is derived based on poroelasticity with p and s wave moduli secondly a stable simultaneous ava inversion approach is presented in a bayesian scheme this approach has little dependence on initial models furthermore it can be applied in heterogeneous reservoirs whose initial models for inversion are not easy to establish finally a model test shows the superiority of this fmr ava inversion method in stability and independence of initial models we obtain a reasonable fluid factor shear modulus and density even with smooth initial models and moderate gaussian noise a real data case example shows that the inverted fluid factor shear modulus and density fit nicely with well log interpretation results which verifies the effectiveness of the proposed method

transverse mixing in an unregulated northern river transverse mixing in an unregulated northern river in canada was studied in different discharge conditions with and without ice cover the distribution of cumulative discharge was constructed on the basis of river cross sectional shapes and a modified streamtube method was proposed to describe transverse mixing the modified method only uses raw field data to calibrate the modeled concentration profiles and thus can produce a reliable mixing coefficient even with relatively low quality field data the effects of river discharge and ice cover on the transverse mixing coefficient were examined in a fixed study reach it was found that the transverse mixing coefficient increased approximately linearly with river discharge from 84 to 960 m3 s the dimensionless transverse mixing coefficient scaled with river shear velocity and river depth appeared unaffected within 14 by the river discharge in both open water and ice covered conditions and its value was 21 smaller in the ice covered condition than

estimation of fracture parameters from reflection seismic data part iii fractured models with monoclinic symmetry existing geophysical and geological data indicate that orthorhombic media with a horizontal symmetry plane should be rather common for naturally fractured reservoirs here we consider two orthorhombic models one that contains parallel vertical fractures embedded in a transversely isotropic background with a vertical symmetry axis vti medium and the other formed by two orthogonal sets of rotationally invariant vertical fractures in a purely isotropic host rock using the linear slip theory we obtain simple analytic expressions for the anisotropic coefficients of effective orthorhombic media under the assumptions of weak anisotropy of the background medium for the first model and small compliances of the fractures all effective anisotropic parameters reduce to the sum of the background values and the parameters associated with each fracture set for the model with a single fracture system this result allows us to eliminate the influence of the vti background by evaluating the differences between t

aluminum coordination in rhyolite and andesite glasses and melts effect of temperature pressure composition and water content abstract the coordination state of the network formers si and al is one of the primary parameters describing the structure of silicate glasses and melts in this experimental study we use 27al mas nmr spectroscopy to investigate the effect of temperature pressure and composition on the coordination of al in dry and hydrous rhyolite and andesite glasses quenched from pressures of up to 3 5 gpa the spectra were collected at a high magnetic field of 20 tesla to increase spectral resolution and allow for a direct quantification of the different al coordinations the disorder around 4 al increases with increasing fictive temperature and pressure and with decreasing water content or peralkalinity al is predominantly 98 in fourfold coordination in all investigated samples nevertheless systematic trends in al coordination have been observed as a function of pressure composition and water content for the investigated pressure range the proportion of 5 al increases with increasing pressure but decreases with increasing water content and proximity to the metaluminous join for rhyolite glasses within analytical uncertainty the amount of 5 al is independent of fictive temperature the addition of water to andesite glasses does not decrease the amount of 5 al in contrast to the rhyolite glasses based on the glass data we conclude that the majority of al and si will be present in fourfold coordination in metaluminous dry and hydrous rhyolite magmas at the temperature and pressure conditions relevant for the crust and the subducting slab up to 3 5 gpa however consistent with previous predictions from model systems more higher coordinated al may be present in andesite and peralkaline or peraluminous rhyolite melts although the exact concentrations cannot be predicted accurately from the available data compared to more depolymerized melts rhyolite melts can accommodate a higher degree of densification without a significant increase in al coordination

anisotropic effective medium modeling of the elastic properties of shales shales are complex porous materials normally consisting of percolating and interpenetrating fluid and solid phases the solid phase is generally comprised of several mineral components and forms an intricate and anisotropic microstructure the shape orientation and connection of the two phases control the anisotropic elastic properties of the composite solid we develop a theoretical framework that allows us to predict the effective elastic properties of shales its usefulness is demonstrated with numerical modeling and by comparison with established ultrasonic laboratory experiments the theory is based on a combination of anisotropic formulations of the self consistent sca and differential effective medium dem approximations this combination guarantees that both the fluid and solid phases percolate at all porosities our modeling of the elastic properties of shales proceeds in four steps first we consider the case of an aligned biconnected clay fluid composite composed of ellipsoidal inclusion

seismic characterization of reservoirs with asymmetric fractures variations of reflection amplitude with offset and azimuth are sensitive to the presence of natural and induced fractures we tested inversion for fracture compliance matrix components from wide azimuth noisy synthetic pp reflection data the model was a fractured reservoir with monoclinic symmetry formed by two sets of vertical asymmetric fractures embedded in a vti background the fractures joints were assumed to be vertical with noncircular shape and or with asymmetric shear compliance results of synthetic inversion showed that an incorrect assumption about fracture shear symmetry e g treating asymmetric fractures as rotationally invariant fractures can cause considerable error in estimation of the fracture compliance matrix components of effective second and fourth rank fracture compliance matrices for a medium with monoclinic symmetry which takes into account layering and multiple fracture sets can be used as attributes related to the characteristics of the fractured medium monte carlo simulation was used to test the effect of uncertainties in the a priori information about background vti parameters of unfractured rock as they affect inversion for these attributes according to this analysis the direction of fast shear wave polarization was inverted robustly in the monte carlo simulation although the average values of the components of fracture compliance matrices obtained from monte carlo simulation were in agreement with the actual values used for forward modeling individual values obtained in monte carlo simulation were sensitive to uncertainties in the background properties in general because the elastic properties of background vti media without fractures or other azimuthally variable features do not cause azimuthal changes in reflection coefficient variation with offset simultaneous inversion for background properties and fracture tensor components require additional constraints

seismic anisotropy of fractured rock a simple method for including the effects of geologically realistic fractures on the seismic propagation through fractured rocks can be obtained by writing the effective compliance tensor of the fractured rock as the sum of the compliance tensor of the unfractured background rock and the compliance tensors for each set of parallel fractures or aligned fractures the compliance tensor of each fracture set is derivable from a second rank fracture compliance tensor for a rotationally symmetric set of fractures the fracture compliance tensor depends on only two fracture compliances one controlling fracture compliance normal the other tangential to the plane of the fractures the stiffness tensor which is more useful in the consideration of elastic wave propagation through rocks can then be obtained by inversion the components of the excess fracture compliance tensor represent the maximum amount of information that can be obtained from seismic data if the background rock is isotropic and the normal a

fracture parameter inversion for marcellus shale abstractwe inverted p wave amplitude variation with offset and azimuth avoaz data from the marcellus shale to obtain fracture parameters that can fully describe the elastic behavior of fractured rocks with overall symmetry of orthorhombic or monoclinic avoaz data from two interfaces 1 the upper interface between top marcellus and stafford limestone and 2 the lower interface between base marcellus and onondaga limestone were used for inversion to check the validity of our inversion results fracture parameters for the marcellus shale were inverted for each interface using monte carlo simulation to include uncertainty in our a priori information i e elastic properties of unfractured rocks that are assumed to be known from well logs inversion results appeared robust with respect to uncertainties and converge to the same values for the two inversions our results were also consistent with singular value decomposition analysis resolution matrix

elastic wave propagation in media with parallel fractures and aligned cracks a model of parallel slip interfaces simulates the behaviour of a fracture system composed of large closely spaced aligned joints the model admits any fracture system anisotropy triclinic the most general monoclinic orthorhombic or transversely isotropic and this is specified by the form of the 3 3 fracture system compliance matrix the fracture system may be embedded in an anisotropic elastic background with no restrictions on the type of anisotropy to compute the long wavelength equivalent moduli of the fractured medium requires at most the inversion of two 3 3 matrices when the fractures are assumed on average to have rotational symmetry transversely isotropic fracture system behaviour and the background is assumed isotropic the resulting equivalent medium is transversely isotropic and the effect of the additional compliance of the fracture system may be specified by two parameters in addition to the two isotropic parameters of the isotropic background dilute systems of flat aligned microcracks in an isotropic background yield an equivalent medium of the same form as that of the isotropic medium with large joints i e there are two additional parameters due to the presence of the microcracks which play roles in the stress strain relations of the equivalent medium identical to those played by the parameters due to the presence of large joints thus knowledge of the total of four parameters describing the anisotropy of such a fractured medium tells nothing of the size or concentration of the aligned fractures but does contain information as to the overall excess compliance due to the fracture system and its orientation as the aligned microcracks which were assumed to be ellipsoidal with very small aspect ratio are allowed to become non fiat i e have a growing aspect ratio the moduli of the equivalent medium begin to diverge from the standard form of the moduli for flat cracks the divergence is faster for higher crack densities but only becomes significant for microcracks of aspect ratios approaching 0 3

comparison of fixed and moving vessel flow measurements with an adp in a large river a comparison of three dimensional flow velocity measurements made with an acoustic doppler profiler adp from fixed and moving vessels at cross sections of the parana river argentina was performed the purpose was to design a rapid and reliable procedure for quantifying the velocity field and related parameters such as bed shear velocity and the identification of secondary circulations in large rivers using an adp the fixed vessel measurements were performed over a period of 10 min at three vertical profiles along two of the sections these data were then compared with the results of ten moving vessel repeat transects made at each of the sections and which intersected the fixed vessel sampling locations using a number of different adp setup configurations from the velocity profiles obtained with both fixed and moving vessel measurements total bed shear velocity values were computed by applying the law of the wall the results indicate there can be significant differences between velocities obtained using the moving vessel method and fixed vessel measurements averaged over 10 min these differences in horizontal velocity can be significantly reduced by averaging five or more moving vessel transects with corresponding shear velocities calculated from five transect averages showing differences ranging between 10 and 15 dependent on the adp configuration location of the at a point vertical velocity profile in relation to large scale bed roughness may also be an influential factor and ideally the bed morphology should be quantified together with the adp derived velocities when using the adp to identify secondary flow cells it was found that although one cross section transect can provide a reasonable overall picture an average of five cross sections is necessary to resolve the finer details of flow the implications for applications that use moving vessel techniques for measurement and analysis of three dimensional flow structures including secondary flows are highlighted

equivalent medium representation of fractured rock a similarity may be found between various approaches for determining the effects of parallel fractures or aligned cracks on seismic wave propagation at wavelengths that are long compared with the scale length of the cracks fractures can be modeled using an empirical linear slip condition however natural fracture surfaces can also be simulated directly as planar distributions of small isolated areas of slip cracks model 1 or conversely as planar distributions of imperfect interfacial contacts model 2 an alternative is plane surfaces separated by thin continuous layers of viscous fluid or a soft material model 3 we present analytic expressions for the fracture compliances for these three models and using these analytic results compute the effective compliances and stiffnesses of the fractured material as a result it is possible to relate the measured compliances or stiffnesses directly to the statistics of the microstructural details of a fracture given appropriate a priori information on the fracture surfaces the results for model 1 are equivalent to a volume distribution of cracks as studied by hudson 1980 1981 for small crack density the results for model 2 are basically the same as those given by white 1983 for a packing of spheres and finally the results for model 3 are in agreement with those given by backus 1962 for combinations of two constituent layers these results can be extended to the case of nonaligned fractures and to allow for fluid flow between cracks and into a porous matrix rock finally it is shown that the ratio of the normal to shear fracture compliance is a good indicator of the properties of the fracture infill

viscous flow behavior of tholeiitic and alkaline fe rich martian basalts abstract the chemical compositions of martian basalts are enriched in iron with respect to terrestrial basalts their rheology is poorly known and liquids of this chemical composition have not been experimentally investigated here we determine the viscosity of five synthetic silicate liquids having compositions representative of the diversity of martian volcanic rocks including primary martian mantle melts and alkali basalts the concentric cylinder method has been employed between 1500 c and the respective liquidus temperatures of these liquids the viscosity near the glass transition has been derived from calorimetric measurements of the glass transition although some glass heterogeneity limits the accuracy of the data near the glass transition it was nevertheless possible to determine the parameters of the non arrhenian temperature dependence of viscosity over a wide temperature range 1500 c to the glass transition temperature at superliquidus conditions the martian basalt viscosities are as low as those of the fe ti rich lunar basalts similar to the lowest viscosities recorded for terrestrial ferrobasalts and 0 5 to 1 order of magnitude lower than terrestrial tholeiitic basalts comparison with empirical models reveals that giordano et al 2008 offers the best approximation whereas the model proposed by hui and zhang 2007 is inappropriate for the compositions considered the slightly lower viscosities exhibited by the melts produced by low degree of mantle partial melting versus melts produced at high degree of mantle partial melting likely corresponding to the early history of mars is not deemed sufficient to lead to viscosity variations large enough to produce an overall shift of martian lava flow morphologies over time rather the details of the crystallization sequence and in particular the ability of some of these magmas to form spinifex texture is proposed to be a dominant effect on the viscosity during martian lava flow emplacement and may explain the lower range of viscosities 10 2 10 4 pa s inferred from lava flow morphology further the differences between the rheological behaviors of tholeiitic vs trachy basalts are significant enough to affect their emplacement as intrusive bodies or as effusive lava flows the upper range of viscosities 10 6 10 8 pa s suggested from lava flow morphology is found consistent with the occurrence of alkali basalt documented from in situ analyses and does not necessarily imply the occurrence of basaltic andesite or andesitic rocks

application of prestack orthotropic avaz inversion for fracture characterization of a deep carbonate reservoir in northern kuwait prestack anisotropic orthotropic symmetry avaz inversion of full azimuth 3d seismic data for fracture characterization of the upper najmah formation in northern kuwait was conducted this formation comprises a thin tight naturally fractured carbonate overlying a kerogen rich shale source rock the inversion methodology uses an orthotropic system of symmetry that is appropriate for analysis of vertical transverse isotropic vti anisotropic rock layers containing swarms of aligned vertical fractures measured seismic amplitudes show good agreement with synthetic models created at different well locations indicating reliable representation of fractures in amplitude data inversion results show good agreement with well and drilling data rock physics modeling shows a relationship between elastic properties and seismic anisotropy and between elastic properties and reservoir properties such as porosity and fracture density

ponded melt at the boundary between the lithosphere and asthenosphere the boundary between earth s rigid lithosphere and ductile asthenosphere is marked by a seismic discontinuity laboratory experiments on basaltic magmas show that melts should pond at pressures that correspond to the lithosphere asthenosphere boundary thus magma ponding could explain the observed seismic discontinuity

case study intermediate field mixing for a bank discharge in a natural river the intermediate field mixing characteristics of the gold bar wastewater treatment plant effluent into the north saskatchewan river at edmonton were evaluated this region may be considered to be the early part of the transverse mixing region where local channel characteristics are important an extensive field study was conducted to delineate the bathymetry of the study area and evaluate the mixing characteristics by means of a steady state dye test the topographic and limited velocity results of the field study were used to create and validate a depth averaged hydrodynamic model of the study reach in order to extract streamtube information the results from the hydrodynamic model were used to interpret the mixing characteristics of the study reach as well as extract channel characteristics from the analysis it is evident that the distribution of effective transverse mixing coefficient is highly dependent on local river conditions the use of the hydrodynamic model to extract channel characteristics provided a reasonable estimate of mixing characteristics without requiring detailed field velocity data the trade off is more detailed bathymetry data is required to have a realistic model plume averaged channel characteristics rather than cross sectional averaged were shown to produce more realistic transverse mixing coefficients assumed gaussian profile distributions were successfully applied suggesting that for a bank discharge if the maximum bank concentration and mass flux are known this technique could be applied

seismic characterization of reservoirs containing multiple fracture sets natural fractures in reservoirs play an important role in determining fluid flow during production and knowledge of the orientation and density of fractures is required to optimize production variations in reflection amplitude versus offset avo are sensitive to the presence of fractures but current models used to invert the seismic response often make simplified assumptions that prevent fractured reservoirs from being characterized correctly for example many models assume a single set of perfectly aligned fractures whereas most reservoirs contain several fracture sets with variable orientation within a given fracture set in addition many authors only consider the azimuthal variation in the small offset amplitude versus offset and azimuth response the variation in avo gradient with azimuth while the effect of fractures on amplitude versus offset and azimuth increases with increasing offset in this paper the variation in the reflection coefficient of seismic p waves as a function of azimuth and offset due to the presence of multiple sets of fractures with variable orientation within any fracture set is used to determine the components of a second rank fracture compliance tensor ij the variation in the trace of this tensor as a function of position in the reservoir can be used to estimate the variation in fracture density with position in the reservoir and may be used to choose the location of infill wells in the field the principal axes of ij reveal the most compliant direction within the reservoir and may be used to optimize the trajectory of deviated wells the determination of the principal axes of ij requires wide azimuth acquisition and the use of the small offset amplitude versus offset and azimuth the azimuthal variation of the avo gradient may give misleading results

use of avoa data to estimate fluid indicator in a vertically fractured medium microstructural attributes of cracks and fractures such as crack density aspect ratio and fluid infill determine the elastic properties of a medium containing a set of parallel vertical fractures although the tangential weakness t of the fractures does not vary with the fluid content the normal weakness n exhibits significant dependence on fluid infill based on linear slip theory we used the ratio g n t termed the fluid indicator as a quantitative measure of the fluid content in the fractures with g representing the square of the ratio of s and p wave velocity in the unfractured medium we used a born formalism to derive the sensitivity to fracture weakness of pp and ps reflection coefficients for an interface separating an unfractured medium from a vertically fractured medium our formulae reveal that the pp reflection coefficient does not depend on the 2d microcorrugation surface roughness with ridges and valleys parallel to the fracture strike whereas the ps reflection coefficien

modeling earth materials from crustal to lower mantle conditions a transferable set of interaction potentials for the cmas system abstract a fully flexible ionic interaction model aspherical ion model aim is presented and applied to various relevant minerals and melts of the ca mg al si o cmas system the model reproduces accurately lattice parameters and thermoelastic properties of minerals in a wide range of compositions furthermore its transferability range extends from the pressure and temperature conditions of the earth s crust to the lower mantle thus the aim extends greatly the applicability of classical models in nanoscale computer simulations of earth materials the increased transferability compared to other interatomic potentials and the much more efficient calculation of interaction energies compared to first principles electronic structure calculations will allow larger scale simulations the potential applications of the aim to new fields of atomistic modeling in earth sciences is discussed

a new fourier azimuthal amplitude variation fracture characterization method case study in the haynesville shale we describe a novel fracture characterization technique utilizing azimuthal amplitude variations avaz present in 3d seismic data and implement it using both synthetic and real seismic data targeting the haynesville shale the method we present here overcomes many common avaz limitations and differs from standard avaz approaches in the following ways 1 it is explicitly designed to model vertically fractured transverse isotropic vfti media 2 it can correctly resolve the fracture strike azimuth without a 90 degree ambiguity and uses a new magnitude based method that is invariant to the sign of seismic reflectivity rpp and 3 it utilizes advanced inversion techniques to estimate a novel fracture density proxy that responds linearly to crack density we present our method using a detailed derivation that relates seismic reflectivity directly to rock fracture properties in vfti media we validate our proposed method through rigorous testing on over 400 synthetic seismic datasets these synthetic test

azimuthally anisotropic elastic impedance inversion for fluid indicator driven by rock physics the normal to tangential fracture compliance ratio is usually used as a fracture fluid indicator ffi for fluid identification in fractured reservoirs with a new parameterization for fracture weaknesses we define a new ffi based on azimuthally anisotropic elastic impedance ei inversion and fractured anisotropic rock physics models first we derived a new azimuthally anisotropic ei equation with a similar expression for the isotropic and anisotropic ei parts to remove the exponential correction of ei which is attributable to weak anisotropy then we built a fractured anisotropic rock physics model used for the estimation of well log parameters for the normal and tangential fracture weaknesses which builds the initial background low frequency trend of fracture weaknesses finally based on the azimuthally anisotropic ei inversion method with the cauchy sparse and low frequency information regularization we estimated a ffi applied to fluid identification in fractured reservoirs tests on both synthe

seismic characterization of naturally fractured reservoirs using amplitude versus offset and azimuth analysis p wave seismic reflection data with variable offset and azimuth acquired over a fractured reservoir can theoretically be inverted for the effective compliance of the fractures the total effective compliance of a fractured rock which is described using second and fourth rank fracture tensors can be represented as background compliance plus additional compliance due to fractures assuming monoclinic or orthotropic symmetry which take into account layering and multiple fracture sets the components of the effective second and fourth rank fracture compliance tensors can be used as attributes related to the characteristics of the fractured medium synthetic tests indicate that using a priori knowledge of the properties of the unfractured medium the inversion can be effective on noisy data with s n on the order of 2 monte carlo simulation was used to test the effect of uncertainties in the a priori information about elastic properties of unfractured rock two cases were considered with wide azimuth waz and narrow azimuth naz reflection data and assuming that the fractures have rotationally invariant shear compliance the relative errors in determination of the components of the fourth rank tensor are substantially larger compared to the second rank tensor under the same assumptions elastic properties of background media consisting in horizontal layers without fractures do not cause azimuthal changes in the reflection coefficient variation with offset thus due to the different nature of these properties compared to fracture tensor components which cause azimuthal anomalies simultaneous inversion for background isotropic properties and fracture tensor components requires additional constraints singular value decomposition svd and resolution matrix analysis can be used to predict fracture inversion efficacy before acquiring data therefore they can be used to determine the optimal seismic survey design for inversion of fracture parameters however results of synthetic inversion in some cases are not consistent with resolution matrix results and resolution matrix results are reliable only after one can see a consistent and robust behaviour in inversion of synthetics with different noise levels