estimation of rock physics properties from seismic attributes part 2 applications abstractthe estimation of quantitative rock physics properties is of great importance for reservoir characterization and monitoring in co2 storage or enhanced oil recovery as an example we have combined the high resolution results of full waveform inversion fwi methods with rock physics inversion because we consider a generic and dynamic rock physics model our method is applicable to most kinds of rocks for a wide range of frequencies the first step allows determination of viscoelastic effective properties i e quantitative seismic attributes whereas the rock physics inversion estimates rock physics properties porosity solid frame moduli fluid phase properties or saturation this two step workflow is applied to time lapse synthetic and field cases the sensitivity tests that we had previously carried out showed that it can be crucial to use multiparameter inputs to accurately recover fluid saturations and fluid properties however due to the limited data availability and difficulties in get

self organization and nonlinear dynamics in sedimentary basins and discussion patterns of mineralization may develop during diagenesis that are not a direct reflection of sedimentary features or stresses and fluids imposed on the boundaries of a basin these patterns occur through the amplification of omnipresent non uniformities of textural or compositional variables amplification occurs through feedback involving the coupling of diagenetic processes the spatial scale of these patterns varies from microns to kilometres examples to be discussed include intracrystalline oscillatory zoning millimetre to metre scale differentiated layering and stylolites liesegang bands reaction front fingering pulsatile fluid release from overpressurized zones in deep basins and kilometre scale basin compartmentation

flow dissolution and precipitation in dolomite 1 the evolution of hydraulic conductivity and porosity during the process of dedolomitization was examined in a series of laboratory experiments by analyzing the effects of concurrent dolomite dissolution and calcium carbonate precipitation linear flow experiments were performed in columns of crushed sucrosic dolomite by injecting different concentrations of hcl at various flow rates temporal changes in head gradient were used to calculate overall hydraulic conductivities of each column while chemical analyses of the effluent acid enabled estimation of porosity changes during the experiments after each experiment the rock samples were retrieved and sectioned in order to study the pore space geometry micromorphology and mineral concentrations a range of injected hcl concentrations and flow rates was identified which leads to oscillations in the effective hydraulic conductivity and porosity of the evolving rock samples in all cases however the porous medium ultimately clogged short term experiments were also used to study the formation of dissolution and precipitation bands along the columns under the experimental conditions dolomite dissolution is a reaction rate controlled process experiments indicated that as such the flow rate and the ph of the injected fluid affect dissolution only during the initial stages when calcium carbonate is dissolved on the other hand both the flow rate and the ph of the injected fluid strongly influence the precipitation process throughout the duration of the experiments because higher flow rates retard nucleation these findings are in qualitative accordance with field observations of dolomite formations

dolomite formation and biogeochemical cycles in the phanerozoic summary based on present knowledge of the purely chemical controls on the kinetics of massive dolomite formation the abundance and distribution of dolomite throughout the phanerozoic remains an enigma sometimes referred to as the dolomite problem comparing dolomite abundance to secular variation in seawater chemistry indicates that some changes in seawater chemistry are more likely to have resulted from extensive dolomitization rather than to have caused it the recently formulated microbial dolomite model provides the opportunity to view the geological history of dolomite formation from a new perspective a biogeochemical approach to the dolomite problem reveals a plausible connection between phanerozoic geochemical cycles and dolomite formation in particular periods of more extensive dolomitization broadly correlate with diverse indicators of decreased oxygen levels in the atmosphere and oceans lowered oxygen levels would have fostered a more active community of anaerobic microbes including sulphate reducing bacteria which in turn could have led to more extensive dolomitization of marine carbonates

concretion morphologies reflecting diagenetic and epigenetic pathways abstract due to complex physicochemical processes concretions develop variable but distinctive morphologies reflecting the state of the sediment in subsequent stages of diagenesis and epigenesis they deserve a study and systematization in their own right at the same time concretional morphologies illustrate the effect of hierarchic self organization which is a basic element also in biological evolution

on the role of density and attenuation in three dimensional multiparameter viscoacoustic vti frequency domain fwi an obc case study from the north sea 3 d frequency domain full waveform inversion fwi is applied on north sea wide azimuth ocean bottom cable data at low frequencies 10 hz to jointly update vertical wave speed density and quality factor q in the viscoacoustic vti approximation we assess whether density and q should be viewed as proxy to absorb artefacts resulting from approximate wave physics or are valuable for interpretation in the presence of soft sediments and gas cloud fwi is performed in the frequency domain to account for attenuation easily multiparameter frequency domain fwi is efficiently performed with a few discrete frequencies following a multiscale frequency continuation however grouping a few frequencies during each multiscale step is necessary to mitigate acquisition footprint and match dispersive shallow guided waves q and density absorb a significant part of the acquisition footprint hence cleaning the velocity model from this pollution low q perturbations correlate with low velocity zones associated with soft sediments and gas cloud however the amplitudes of the q perturbations show significant variations when the inversion tuning is modified this dispersion in the q reconstructions is however not passed on the velocity parameter suggesting that cross talks between first order kinematic and second order dynamic parameters are limited the density model shows a good match with a well log at shallow depths moreover the impedance built a posteriori from the fwi velocity and density models shows a well focused image with however local differences with the velocity model near the sea bed where density might have absorbed elastic effects the fwi models are finally assessed against time domain synthetic seismogram modelling performed with the same frequency domain modelling engine used for fwi

cenozoic dolomites of carbonate islands their attributes and origin abstract dolomites found on and below carbonate islands atolls and oceanic platforms provide useful insights into the origin of dolomite insights that may not be attainable from the study of more ancient cratonic dolomites for this reason they have been the subject of study for decades a critical mass of case studies now exist and some significant conclusions can be drawn from the cumulative data in most cases the association with an island is causal and not genetic nevertheless these dolomite occurrences are referred to herein as island dolomites one type of dolomite on carbonate islands is penecontemporaneous dolomite a phase that forms while the host sediment is in its original depositional setting island examples are holocene in age occur in holocene sediments and originate as a direct precipitate from either normal or evaporated seawater these are microcrystalline poorly ordered ca rich 18o enriched and geochemically unstable phases that are susceptible to recrystallization in the setting in which they formed post depositional dolomite is the other type of dolomite associated with carbonate islands this type of dolomite replaces older precursors and forms as cement distinctive characteristics include a dominance of fabric preserving texture pore lining cement rims that may exhibit micron scale banding with low mg calcite and formation in association with precursor dissolution sr isotopic dating indicates that all examples are neogene or quaternary in age those formed during the middle miocene through pliocene are massive laterally continuous and often multigenerational in contrast younger examples tend to be localized partial replacements of a single generation sr isotope ages also suggest global synchroneity in many dolomitization events which suggests a connection between dolomitization global eustacy and or global climatic factors geochemical attributes of post depositional island dolomites are ca enrichment positive 18o and 13c low sr contents 150 300 ppm and low fe global similarity in petrography and geochemistry of replacive island dolomites argues for a similar origin inferred origins however depend primarily on how 18o and sr data are interpreted values for 18o and dsr must be assumed due to uncertainties in oxygen isotope fractionation and sr partitioning there is no consensus or uniformity in those assumptions thus interpretations can vary and be biased to a desired result covariant trends in 13c and 18o some negative 13c values and high sr all favor a mixing zone origin but examples with these attributes are few lack of covariance in the isotopes mean 18o of 2 0 to 3 5 and low sr future studies should standardize the type of data collected and the analytical techniques employed multiple geochemical attributes should be measured on microsampled components and quantitative modeling should be employed in order to constraint interpretations as much as possible also needed are a better understanding of the kinetic processes that form these dolomites more careful assessment of their recrystallization status and an improved understanding of dsr and 18o at low temperature

formation of lateral patterns in rock properties by dolomitization evidence from a miocene reaction front bonaire netherlands antilles abstract petrophysical and geochemical properties of dolomites may exhibit a nested set of lateral patterns typically at the scales of a few meters to 20 m this study assesses whether those lateral patterns are inherited from the limestone precursor or formed during dolomitization sampling was done across a preserved limestone to dolomite reaction front in grainstones of the miocene seroe domi formation bonaire netherlands antilles post dolomitization diagenetic overprinting in the two rock types is absent or minimal two 65 m lateral transects were drilled at 30 cm spacing in two separate beds porosity permeability and geochemical 18o 13c mn sr and na analyses were performed on all 287 recovered samples and 287 thin sections were point counted for petrographic attributes variography shows that dolomite abundance and porosity contain three scales of lateral variability much of the signal is random sample to sample noise as 65 of the total spatial variance occurs at 30 cm spacing however porosity and dolomite abundance also exhibit a short scale correlation length of 3 7 m and a long range oscillatory pattern hole effect at 16 m both of which are also periodic trace elements mn sr and permeability exhibit short range correlation to 5 8 m but no long range pattern mole mg and 13c show increasing variance with distance and all other dolomite attributes exhibit no spatial patterns no limestone attributes show evidence for any short range or long range oscillatory patterns this indicates that the lateral patterns in dolomite abundance porosity permeability sr and mn contents were not inherited from the limestone precursor dolomitization is interpreted to be the cause of the observed spatial patterns as that is the only geologic process that has affected the dolomite but not the limestone on the other side of the front geochemical self organization during the dolomitization process is suggested to be the mechanism by which the spatial patterns in the dolomites emerge a model for that self organizing process is proposed that involves positive feedbacks between precipitation dissolution textural properties reaction rates carbon transport and the evolving flow field relative to mississippian permian and eocene dolomites that have been studied previously the seroe domi dolomites have similar porosity variance at 30 cm spacing and hole effects with slightly greater wavelengths and much larger magnitudes any differences are interpreted to be related to diagenetic history the older dolomites have been affected by burial diagenesis and or weathering which would likely increase sample to sample variability therefore increasing short scale randomness decreasing the magnitude of hole effects and shortening wavelengths of hole effects the lateral patterning formed by dolomitization may thus not be as strongly expressed in ancient dolomites that have complex burial histories

alterations in guano phosphates and mio pliocene carbonates of table mountain santa barbara curacao abstract the table mountain santa barbara consisting of the mio pliocene seroe domi limestone formation was probably covered with a guano layer in the pleistocene solutions carrying guano derived phosphate percolated downwards resulting in partial phosphatization of the underlying limestones only two phosphate minerals are present in the table mountain apatite and whitlockite phosphatization includes both replacement of the original carbonate or pre phosphate dolomite and cementation in primary as well as secondary porosity cryptocrystalline isotropic phosphate cement micro crystalline apatite isopachous apatite fringe cement multiple zoned apatite crusts rhombic whitlockite cements two factors controlled the final distribution of the phosphate within the table mountain firstly changing positions of the sea level and therefore of the diagenetic environments determined the overall distribution of the phosphatized interval a horizontal layer 98 128 m above sea level sandwiched between two non phosphatized limestone units original carbonate facies and mineralogy was the second controlling factor causing the final variations in degree of phosphatization the limestones comprise two lithofacies a coralliferous limestone lenses erratically distributed amidst and b micritic limestones these coralliferous limestones are phosphatized preferentially forming so called phosphate pockets sharply outlined within a non phosphatized micritic limestone host these pockets are characteristically organized into five zones which are described in detail higher original porosity permeability of the coralliferous limestone lenses as compared to the micrites additionally enhanced by a phase of pre phosphate dolomitization determined preferential phosphatization of this facies type a second controlling factor was the original carbonate mineralogy and resulting dia

lateral periodic variations in the petrophysical and geochemical properties of dolomite mississippian dolowackestones contain periodic oscillations in the lateral distribution of trace element concentrations porosity and permeability random variations at 30 cm spacing account for 50 70 of the total variability the remainder of the variability occurs in short and long range oscillatory patterns with periods of 1 2 7 6 m which can only be resolved by high resolution sampling of an 150 m lateral transect possible origins for these patterns are 1 inheritance from the depositional precursor 2 for mation by self organizing processes during dolomitization or 3 overprinting by late dia genesis these oscillatory patterns have up to now been unrecognized and addressing their origin and meaning s represents a new approach to the study of dolomites under standing the lateral distribution of petrophysical properties can also improve models of fluid flow in dolomite petroleum reservoirs and contaminant transport between matrix and conduits in dolomite aquifers further if 30 50 of the variability in a geochemical attribute in any bed is due to lateral periodicity one must ask if that variability is too great to assume a spot sample will be a suitable proxy for ancient geologic processes and conditions

implications of replacement for reaction transport modeling abstract mineral replacement in rocks consists of growth of guest mineral and dissolution of host the two reactions are coupled by the grain grain stress generated by growth of the guest grain in a rigid or very viscous rock in which it has initially no available room this stress self adjusts to make the volumetric rates of guest growth and host dissolution equal to each other which accounts for the volume conservation typical of replacement volume preservation during replacement is required by conservation of mass and momentum as well the two reactions are also simultaneous and proceed by a sequence of many tiny alternating increments where these increments are small enough internal textural details of the host grain or grain aggregate are morphologically preserved as ghost textures by the replacement the strong variation of mineral reaction rates with stress required by replacement is evidenced also experimentally reported widespread replacement in many rocks laterites diagenesis of siliciclastics and carbonates metasomatic ores metamorphic rocks and hydrothermal alteration warrants creating water rock reactive transport models that predict when and where in a system replacement should take place current geochemical models implicitly view replacement as sequential uncoupled dissolution of host and growth of guest this sequence of reactions may also occur in rocks but crucially differs from replacement implications of replacement for water rock reaction modeling include 1 balancing of replacement reactions on volume 2 use of helmholtz rather than gibbs free energies of minerals involved in replacement 3 taking account of the strong stress dependence of mineral growth and dissolution rates in rocks and 4 taking account of possible accommodation of growth by local deformation as well as pressure solution of the host rock and of the effect of strain rate growth rate on local rock viscosity

outcrop analog for cyclic shelf reservoirs san andres formation of permian basin stratigraphic framework permeability distribution geostatistics and fluid flow modeling vertical and horizontal transects were sampled from core and outcrop of the san andres formation at lawyer canyon guadalupe mountains new mexico to assess permeability variation in a geologic framework of upward shallowing carbonate cycles and to show the potential effect these variations have on viscous dominated flow behavior in analogous reservoirs these cycles occur in a ramp crest facies tract are 3 13 m 10 45 ft thick and contain both vertical and lateral variation of lithofacies thicker cycles consist of a basal dolomudstone which is overlain by burrowed dolopackstone and capped by bar flank ooid peloid dolograinstone and bar crest ooid dolograinstones in vertical transects permeability is extremely variable about the mean yet upward increasing trends coinciding with the succession of lithofacies typify a given cycle semi variance analysis shows permeability to be uncorrelated vertically at distances greater than 5 5 m 18 ft which is the average cycle thickness suggesting that the cycles may equate to a fluid flow unit in a reservoir semi variance analysis of measurements collected along a horizontal transect within bar crest dolograinstones of a single cycle shows permeability is uncorrelated at distances greater than 3 6 m 12 ft this correlation distance appears to be controlled by alternating porous and tightly cemented zones that formed during dolomitization vertical and lateral variogram models were fit to the spatial parameters to generate a variety of conditionally simulated permeability fields fluid flow simulations show viscous dominated flow behavior is compartmentalized by both the individual cycles and groups of cycles the basal dolomudstones are potential baffles to flow crossover between cycles but poorly developed cycles i e those that are mud rich and lack well developed bar flank and bar crest facies result in the greatest compartmentalization of fluid flow within a succession of cycles

time lapse seismic imaging using regularized full waveform inversion with a prior model which strategy full waveform inversion is an appealing technique for time lapse imaging especially when prior model information is included into the inversion workflow once the baseline reconstruction is achieved several strategies can be used to assess the physical parameter changes such as parallel difference two separate inversions of baseline and monitor data sets sequential difference inversion of the monitor data set starting from the recovered baseline model and double difference inversion of the difference data starting from the recovered baseline model strategies using syntheticmarmousi data sets we investigate which strategy should be adopted to obtain more robust and more accurate time lapse velocity changes in noise free and noisy environments this synthetic application demonstrates that the double difference strategy provides the more robust time lapse result in addition we propose a target oriented time lapse imaging using regularized full waveform inversion including a prior model and model weighting if the prior information exists on the location of expected variations this scheme applies strong prior model constraints outside of the expected areas of timelapse changes and relatively less prior constraints in the time lapse target zones in application of this process to the marmousi model data set the local resolution analysis performed with spike tests shows that the target oriented inversion prevents the occurrence of artefacts outside the target areas which could contaminate and compromise the reconstruction of the effective time lapse changes especially when using the sequential difference strategy in a strongly noisy case the target oriented prior model weighting ensures the same behaviour for both time lapse strategies the double difference and the sequential difference strategies and leads to a more robust reconstruction of the weak time lapse changes the double difference strategy can deliver more accurate time lapse variation since it can focus to invert the difference data however the double difference strategy requires a preprocessing step on data sets such as time lapse binning to have a similar source receiver location between two surveys while the sequential difference needs less this requirement if we have prior information about the area of changes the target oriented sequential difference strategy can be an alternative and can provide the same robust result as the doubledifference strategy

deformation of mg0 9 fe0 1 sio3 perovskite aggregates up to 32 gpa room temperature investigations on the shear stress and deformation mechanisms of mg0 9fe0 1 sio3 perovskite are performed in situ up to 32 gpa using radial x ray diffraction and the diamond anvil cell as a deformation apparatus the uniaxial stress supported by the perovskite aggregate is found to increase continuously with pressure up to 10 9 1 9 gpa at 32 1 gpa our measurements show no development of significant lattice preferred orientations in the sample which indicates that deformation by dislocation glide is not the dominant deformation mechanism under these conditions assuming that the underlying cause for seismic anisotropy in the deep earth is elastic anisotropy combined with lattice preferred orientation our results indicate that silicate perovskite deformed under the conditions of this experiment would not be the source of seismic anisotropy c 2003 elsevier science b v all rights reserved

in situ measurement of texture development rate in cairo3 post perovskite the rate of crystallographic preferred orientation cpo development during deformation of post perovskite is crucial in interpreting seismic anisotropy in the lowermost mantle but the stability field of mgsio3 post perovskite prevents high strain deformation experiments being performed on it therefore to constrain the rate of cpo development in post perovskite we deformed cairo3 a low pressure analogue of mgsio3 post perovskite in simple shear at 3 2 gpa and 400 c to a shear strain of 0 81 from x ray diffraction patterns acquired during deformation we invert for cpo as a function of strain by comparing the cpo that develops with visco plastic self consistent vpsc models we constrain the critical resolved shear stresses crss of the non primary slip systems in cairo3 to be of order 6 times stronger than the primary 100 010 slip system this value is significantly less than has been assumed by previous studies and if applicable to mgsio3 implies that seismic anisotropy in the d layer develops slower than has previously been assumed

influence of aperture variability on dissolutional growth of fissures in karst formations the influence of aperture variability on dissolutional growth of fissures is investigated on the basis of two dimensional numerical simulations the logarithm of the fissure aperture before dissolution begins is modeled as a gaussian stationary isotropic random field the initial phase of dissolutional growth is studied up to the time when turbulent flow first occurs at a point within the fissure the breakthrough time the breakthrough time in variable aperture fissures is smaller than that in uniform fissures and decreases as the coefficient of variation of the aperture field increases in comparing uniform and variable aperture fissures in limestone the breakthrough time with 0 1 is about a factor of 2 smaller than that in a uniform fissure the breakthrough time is reduced by about an order of magnitude with 2 0 the mechanism leading to reduced breakthrough times is the focusing of flow into preferential flow channels which are enlarged at a faster rate than the surrounding regions of slower flow dissolution channels are narrower and more tortuous as increases investigations of the influence of reaction rate reveal that the influence of aperture variability is more pronounced in rapidly dissolving rock in uniform fissures in rapidly dissolving minerals breakthrough times are very long since water becomes saturated with respect to the mineral within a short distance of the entrance to the flow path however in variable aperture fissures breakthrough occurs rapidly because of selective growth along preferential flow channels which progressively capture larger fractions of the total flow these results partly explain why conduits develop rapidly in gypsum although previous one dimensional studies suggest that conduit growth will not occur

modeling dislocations and plasticity of deep earth materials it is widely recognized that earth sciences were revolutionized when continental drift proposed by wegener in 1912 took the more comprehensive form of plate tectonics following the early suggestion of holmes hess proposed in the early sixties what missed to wegener s model a mechanism and a driving force i e the presence of large flows within the convecting mantle to evacuate the internal heat the earth appears now as a dynamic system dominated by flows and deformation processes almost everywhere convective flow in the liquid core which is the source of the earth magnetic field slow deformation of the hot viscous solid mantle and rigid brittle deformations of the cold crust understanding and modeling the deformation mechanisms of earth materials is thus one of the most important challenges of geophysics among the three large topics listed above we will focus on mantle convection only two scientific fields which developed approximately at the same time i e just before and just after the second world war meet here geophysics and materials science which aims at explaining how solids can deform see below mantle convection raises however some questions that are specific to this field although some very significant advances have been achieved recently on the experimental side see for instance karato and weidner 2008 most of these questions remain largely unsolved and at the limits of our capabilities it appears thus necessary to complement the usual experimentally based approach by a numerical multi scale modeling approach in order to increase the significance of our models this multi scale modeling must be based on the physics at the relevant scales see fig 1 and will

kilometer scale chemical reaction boundary patterns and deformation in sedimentary rocks abstract we use three dimensional 3d seismic data to image patterns developed by kilometer scale chemical reaction boundaries to demonstrate that chemical patterns are scaleable phenomena the patterns develop in biosiliceous marine successions due to the dissolution of opal a biogenic silica and reprecipitation as opal ct crystobalite and tridymite during burial the reaction boundary patterns comprise roughly circular regions where the reaction boundary has preferentially advanced these regions are up to 2 7 km wide and c 50 200 m in height and are termed cells the cells form by amalgamation with adjacent juvenile cells they also form by the incorporation of much smaller regions surrounding the cells where the chemical change has already occurred that we term satellites 50 m wide the reaction results in enhanced rates of sediment compaction hence differential advancement of reaction boundaries causes differential subsidence of the overburden inducing folding and faulting of the overburden above the cellular promontories we propose three potential mechanisms for the development of kilometer scale reaction boundary patterns a mass transport of silica by advection b perturbation of isotherms as a result of convective or conductive heat transport or c establishment of a positive feedback loop between fluid production due to the reaction hydraulic fracturing and the upward and lateral transport of fluids this study provides the first insights into how strongly patterned diagenetic reaction boundaries evolve at a basin scale an initial conceptualization of the potential range of reaction boundary morphologies that could exist in this diagenetic system and the likely mechanisms that could control them furthermore it demonstrates that the discipline of seismic diagenesis could represent a completely new approach for the study of chemical diagenetic processes in sedimentary rocks

dolomite occurrence evolution and economically important associations abstract dolomite is not a simple mineral it can form as a primary precipitate a diagenetic replacement or as a hydrothermal metamorphic phase all that it requires is permeability a mechanism that facilitates fluid flow and a sufficient supply of magnesium dolomite can form in lakes on or beneath the shallow seafloor in zones of brine reflux and in early to late burial settings it may form from seawater from continental waters from the mixing of basinal brines the mixing of hypersaline brine with seawater or the mixing of seawater with meteoric water or via the cooling of basinal brines bacterial metabolism may aid the process of precipitation in settings where sulfate reducing species flourish and microbial action may control primary precipitation in some hypersaline anoxic lake settings dolomite is a metastable mineral early formed crystals can be replaced by later more stable phases with such replacements repeated a number of times during burial and metamorphism each new phase is formed by the partial or complete dissolution of an earlier dolomite this continual re equilibration during burial detracts from the ability of trace elements to indicate depositional conditions and resets the oxygen isotope signature of the dolomite at progressively higher temperatures because subsurface dolomite evolves via dissolution and reprecipitation a bed of dolomite can retain or create porosity and permeability to much greater burial depths and into higher temperature realms than a limestone counterpart dolomitization also creates new crystals with new rhomb growth following the dissolution of less stable precursors repetition of this process without complete pore cementation can generate intercrystalline porosity a number of times in the rock s burial history intercrystalline porosity is a highly interconnected style of porosity that gives dolomite reservoirs their good fluid storage capacity and efficient drainage the fact that many dolomite reservoirs formed via brine reflux means that they sit beneath an evaporite seal in both platform and basinwide evaporite settings the same association of evaporites sulfate source and entrained hydrocarbons means that burial conditions are also suitable for thermochemical sulfate reduction and the precipitation of base metals this tends to occur at higher temperatures 60 c 80 c and so the resulting dolomites tend to be ferroan and consist of saddle shaped crystals

integrated characterization of carbonate ramp reservoirs using permian san andres formation outcrop analogs the san andres formation permian guadalupian of the permian basin is representative of carbonate ramp reservoirs in that it has highly stratified character complex facies and permeability structure and generally low recovery efficiencies of 30 of original oil in place the approach used here to describe carbonate ramp reservoirs such as the san andres formation produces detailed reservoir models based on integration of sequence stratigraphic analysis petrophysical quantification through definition of rock fabric flow units and fluid flow simulation synthesis of these subdisciplines clarifies which aspects of the geologic petrophysical model are most significant in predicting reservoir performance and ultimately in understanding the location of remaining oil satur tion the san andres formation crops out along the algerita escarpment a long oblique dip continuous shelf to basin exposure in the central guadalupe mountains these outcrops provide a unique opportunity to study lateral relationships in geologic and petrophysical structure analogous to those occurring between wells in subsurface reservoirs on the basis of sequence stratigraphic analysis three scales of cyclicity are recognized depositional sequences high frequency sequences and cycles examination of the cycles in two detailed window areas provides a practical scale for petrophysical quantification and fluid flow simulation an understanding of cycle position within the high frequency sequence framework also provides predictive information petrophysical analysis revealed six rock fabric groups dominated by intergranular separate vug or dense intercrystalline pore types comparison of these rock fabric groups with facies descriptions produced a rock fabric flow unit model that honors the geologic structure of the cycle and sequence framework permeability data were averaged within rock fabric flow units using a geometric mean approach based on fine scale fluid flow modeling of deterministic and stochastically generated permeability fields two dimensional black oil fluid flow models illustrate that 1 major differences in sweep efficiency and fluid flow performance are predicted when linear interwell interpolations are compared with actual interwell scale geologic structure as determined by outcrop geologic and petrophysical mapping 2 an understanding of static geologic petrophysical conditions provides only a partial understanding of reservoir performance defined by the interaction of these static properties and dynamic properties of fluid flow interaction within the flow unit architecture and 3 because of the orderly distribution of high and low permeability facies within cycle stacks of high frequency sequences this larger scale of geologic description can give a reasonable first order approximation of fluid flow patterns and early breakthrough end page 181

a downscaling strategy from fwi to microscale reservoir properties from high resolution images abstract extracting detailed earth information from an ensemble of seismic traces is a challenge facing full waveform inversion so far success on synthetic and real data has been accomplished primarily for the twin purposes of complex structural imaging and geologic interpretation an ongoing issue for the seismic imaging community in addition to building high resolution images is the reliable extraction of acoustic and shear velocities anisotropic parameters quality factors and density such extractions performed at the seismic resolution scale should help greatly with quantitative interpretation and estimation of rock properties a step toward this goal is described here a generic rock physics model is assumed which upscales microscale rock physics properties to mesoscale effective medium poroelastic quantities to be recovered from macroscale estimates of seismic attributes it is shown on simple synthetic examples that quantitative multiparameter reconstruction when it is possible can re

elasticity and dislocations in ice x under pressure abstract we determine the compressibility the elasticity and the slip systems for ice x in the 100 350 gpa pressure range from first principles calculations our results show that ice x has a high elastic anisotropy which increases by more than two orders of magnitude over this pressure range we use the peierls nabarro model to compute the dislocation structure for the most likely glide systems we obtain that the easiest slip systems are 1 1 1 1 1 0 at low pressures and 1 0 0 1 1 0 at higher pressure this suggests that the mantle of large icy planets may have different rheological properties at shallow and at deep conditions in contrast the mantle of smaller icy planets would be more homogeneous from a rheological point of view

terra rossa genesis implications for karst and eolian dust a geodynamic thread abstract although terra rossa has long been thought to form by residual dissolution of limestone and or by accumulation of detrital mud ash or dust on preexisting karst limestones we present conclusive new field and petrographic evidence that terra rossa forms by replacement of limestone by authigenic clay at a moving metasomatic front several centimeters wide the red clay s major chemical elements al fe and si probably come from dissolved eolian dust the replacement of calcite by clay exhibits a serrated microstylolitic texture that helps prove that replacement happens not by dissolution precipitation as conventional wisdom has it but by pressure solution of calcite driven by the crystallization stress generated by the growth of clay crystals the acid produced by the isovolumetric replacement of limestone by clay quickly dissolves out additional porosity permeability in an adjacent slice of limestone within the front triggering a reactive infiltration instability that should theoretically

generation of evenly spaced pressure solution seams during late diagenesis a kinetic theory stylolites and pressure solution seams can form during diagenesis of rocks subjected to stress through a feedback involving texture and pore fluid solute concentration this feedback destabilizes the state of uniform texture represented here only by porosity for simplicity a mathematical kinetic model that includes pressure solution diffusion and reprecipitation predicts the spontaneous generation even in initially uniform rocks of regions alternatingly in space more and less soluble a region that becomes more soluble also becomes simultaneously more porous the kinetic theory predicts that stylolites can form at roughly constant spacings this agrees with many field and petrographic observations bedding planes between beds that have initially different texture are shown by the theory to be the focus of a porosity instability that can lead to the formation of a stylolite and to the generation of more stylolites within each bed this prediction agrees with the observation that many stylolites have developed at bedding planes

terra rossa genesis by replacement of limestone by kaolinite iii dynamic quantitative model abstractwe model quantitatively the chemical dynamics of terra rossa formation that we deduced earlier from new field and petrographic evidence the key phenomenon is that authigenic kaolinite a proxy for kaolinite solid solutions and other clays replaces limestone at a downward moving reaction front at the base of the existing terra rossa the chemical elements needed to make the authigenic clay are assumed to come from dissolution of eolian clay dust deposited at the surface the model consists of equations of mass conservation in one spatial dimension that incorporate infiltration diffusion and replacement and dissolution reactions distinctive elements of the model are that 1 the kinetics of the kaolinite for calcite replacement is dominated by the crystallization stress generated by the kaolinite growth in accordance with the view that replacement happens not by dissolution precipitation but by guest mineral growth driven pressure solution of the host 2 the field observation that the terr

from velocity and attenuation tomography to rock physical modeling inferences on fluid driven earthquake processes at the irpinia fault system in southern italy we retrieve 3 d attenuation images of the crustal volume embedding the fault system associated with the destructive ms 6 9 1980 irpinia earthquake by tomographic inversion of t measurements a high qp anomaly is found to be correlated with the 1980 fault geometry while the qs model shows regional scale variations related to the ne edge of the uplifted pre tertiary limestone an upscaling strategy is used to infer rock properties such as porosity consolidation type of fluid mixing and relative saturation percentage at 8 10 km fault depth we constrain the porosity and consolidation in the ranges 4 5 and 5 9 respectively with the possible fluid mixes being both brine co2 and ch4 co2 the consolidation parameter range indicates high pore pressures at the same depths these results support the evidence for a fracture system highly saturated in gases and a seismicity triggering mechanism at the fault zone which is strongly controlled by fluid induced pore pressure changes

giant calcite cemented concretions dakota formation central kansas usa giant spheroidal concretions cannonball concretions some nearly 6 m in diameter in fluvial channel fill sandstones at two localities of the dakota sandstone formed by import of cement constituents at a burial depth of 1 km during cannonball concretion growth a self organizational process restricted concretions to a relatively few but widely spaced and locally evenly spaced sites other forms of calcite cements at these localities are cement patches in the form of intergrown grape size concretions grapestone and locally pervasive cement an early episode of invasion by thermogenically generated h2s which reacted with iron oxides on detrital grains generated scattered pyrite crystals and decimetre scale spheroidal pyrite concretions intergranular volumes igv in the concretions range from 36 to 27 the absence of a trend in igv and of carbon and oxygen isotope ratios from cannonball centres to margins indicates that these concretions did not cement progressively outwards from the centre rather the modern spheres represent the spatial extent of nucleation sites that were not otherwise organized within that volume carbon and oxygen isotope values for concretion calcites plot along a swath between depleted values of 18c of 36 and 18o of 13 and enriched values of 4 and 6 respectively four groups of calcites are evident on the basis of trace element content and suggest that the calcite precipitated across a range of oxidation conditions that do not correlate strongly with the isotopic compositions although fluvial overbank sandstones have some pedogenic calcite the channel sandstones have at most a trace of pedogenic calcite and carbonate rock fragments so that the bulk of cement components were imported to the sandstones carbon and calcium sources for calcite cement include marine limestone carbonate shells and anhydrite in addition to hco derived from oxidized methane most likely derived from beds underlying or laterally in communication with dakota sandstones hco in ascending formation waters released during compaction mixed with meteoric water whose temperature and composition varied with time to generate the 7 range in 18ocalcite values measured

required but disguised environmental signals in limestone marl alternations the nature of rhythmic carbonate rich successions such as limestone marl alternations has been and still is subject to controversy the possibility of an entirely diagenetic origin for the rhythmic calcareous alternations is discarded by most authors one problem with an entirely diagenetic self organized development of limestone marl alternations is the fact that limestone and marl beds in many examples are laterally continuous over hundreds of meters or even kilometers in an entirely self organized system lateral coupling would be very limited thus one would expect that rather than laterally continuous beds randomly distributed elongate nodules would form we address the origin of limestone marl alternations using a computer model that simulates differential diagenesis of rhythmic calcareous successions the setup uses a cellular automaton model to test whether laterally extensive rhythmic calcareous alternations could develop from homogeneous sediments in a process of self organization our model is a strong simplification of early diagenesis in fine grained partly calcareous sediments it includes the relevant key mechanisms to the question whether an external trigger is required in order to obtain laterally extensive limestone marl alternations our model shows that diagenetic self organization alone is not sufficient to produce laterally extensive correlatable beds although an external control on bedding formation could be considered to have solved the problem as commonly assumed we here suggest an interesting third possibility the rhythmic alternations were formed through the interaction of both an external trigger and diagenetic self organization in particular we observe that a very limited external trigger either in time or amplitude readily forms correlatable beds in our otherwise diagenetic model remarkably the resulting rhythmites often do not mirror the external trigger in a one to one fashion and may differ in phase frequency and number of couplets therefore the interpretation of calcareous rhythmites as a one to one archive of climate fluctuations may be misleading parameters independent of diagenetic alteration should be considered for unequivocal interpretation