use of nmr logging to obtain estimates of hydraulic conductivity in the high plains aquifer nebraska usa 1 hydraulic conductivity k is one of the most important parameters of interest in groundwater applications because it quantifies the ease with which water can flow through an aquifer material hydraulic conductivity is typically measured by conducting aquifer tests or wellbore flow wbf logging of interest in our research is the use of proton nuclear magnetic resonance nmr logging to obtain information about water filled porosity and pore space geometry the combination of which can be used to estimate k in this study we acquired a suite of advanced geophysical logs aquifer tests wbf logs and sidewall cores at the field site in lexington nebraska which is underlain by the high plains aquifer we first used two empirical equations developed for petroleum applications to predict k from nmr logging data the schlumberger doll research equation ksdr and the timur coates equation kt c with the standard empirical constants determined for consolidated materials we upscaled our nmr derived k estimates to the scale of the wbf logging k kwbf logging estimates for comparison all the upscaled kt c estimates were within an order of magnitude of kwbf logging and all of the upscaled ksdr estimates were within 2 orders of magnitude of kwbf logging we optimized the fit between the upscaled nmr derived k and kwbf logging estimates to determine a set of site specific empirical constants for the unconsolidated materials at our field site we conclude that reliable estimates of k can be obtained from nmr logging data thus providing an alternate method for obtaining estimates of k at high levels of vertical resolution

instability of a lithospheric step beneath western north island new zealand lithospheres of different thicknesses are often juxtaposed by movement on a continental transform boundary such a boundary with a step change in densities may trigger a gravitational instability as lateral pressure gradients are created where normal mantle lithosphere terminates against less dense asthenospheric mantle here we show for plausible values of the lithospheric viscosity a mechanism by which the thicker mantle lithosphere will drip off into the lower density asthenosphere as the mantle deforms it also progressively thickens and then thins the overlying crust creating a topographic wave that migrates in concert with the removal of mantle lithosphere within western north island new zealand geophysical data define a sharp lithospheric step across the taranaki ruapehu line and geological observations provide a history of uplift and subsidence that has propagated southward in the past 12 m y the rate of observed north to south migration of the wave 30 mm yr its wavelength 250 km and amplitude 1 km are compatible with it being caused by progressive removal of mantle lithosphere if the viscosity of the uppermost lithospheric mantle is 5 10 20 pa s providing one of the clearest examples yet of this fundamental geological process

neodymium isotopes in seawater from the barents sea and fram strait arctic atlantic gateways abstract the neodymium concentration c nd and isotopic composition e nd in seawater have been determined in the water column at five sites in the barents sea fram strait area where most of the water exchange between the arctic ocean and the north atlantic takes place in the main arctic ocean inflow branch across the barents sea the concentration and isotopic composition c nd 15 5 pmol kg and e nd 10 8 are similar to those reported for the northeastern nordic seas which is consistent with this region being a source area for the arctic inflow due to the addition of nd from svalbard shelf sediments the c nd in the surface waters above 150 m in the fram strait inflow branch is higher by a factor of 2 and the e nd is shifted to lower values 11 8 in the stratified nansen basin where cold low salinity water overlies warmer atlantic water the c nd and e nd do not vary with the vertical temperature salinity structure but are essentially constant and similar to those of the atlantic inflow throughout the entire water column down to 3700 m depth which indicates that the nd is to a large extent of atlantic origin compared to the atlantic inflow water the nd in the major arctic ocean outflow the fram strait show higher c nd in the surface waters above 150 m and a higher e nd 9 8 throughout the entire water column down to 1300 m depth sources for the more radiogenic nd isotopic composition in deep water of the fram strait outflow most likely involve boundary exchange with sediments on the shelf and slope as the water passes along the canadian archipelago river water is a possible source in the surface water but it also seems likely that pacific water nd modified by interactions on the shelf is an important component in the fram strait surface outflow changes in the relative proportions of inflow of river water and flow of pacific water through the arctic ocean could thus influence the isotopic composition of nd in the north atlantic

neodymium isotope constraints on chemical weathering and past glacial activity in svalbard abstract neodymium nd isotopes in leached authigenic components of marine sediments have been increasingly used as a tracer of past ocean water masses despite the general assumption that the nd isotopic composition of solutes released during chemical weathering fingerprints the source rocks on continents preferential dissolution of easily dissolvable phases may result in significant deviations in nd isotopic composition between the solutes and the source rocks with potential implications for the utility of nd isotopes in paleoenvironmental studies here we present the nd isotopic compositions of leached and detrital fractions separated from bedrock and marine sediment samples from the svalbard archipelago our goal is to further understand the behaviour of nd isotopes during chemical weathering in glacial catchments and evaluate how glacier fluctuations and associated weathering congruency may have affected the export of dissolved nd isotope signatures to seawater our results confirm that terrestrial weathering on svalbard causes considerable nd isotopic decoupling between the leached and detrital fractions of fjord sediments end resulting from the preferential dissolution of marine precipitates in glaciated catchments dominated by sedimentary rocks we also show that the degree of nd isotopic decoupling has fluctuated in response to climate variability on svalbard during the holocene which is also as suggested by the occurrence of generally higher end values during periods of glacier advances in sediment cores retrieved from two different fjords dicksonfjorden and woodfjorden we posit that the high end values can be ascribed to incongruent chemical weathering of fresh rock flour produced by glacial abrasion this finding suggests that the degree of nd isotopic decoupling could be used as a new proxy for tracing glacial fluctuations and associated glacier derived nutrient inputs to the marine realm

nmr measurements in carbonate rocks problems and an approach to a solution carbonate rocks are well known for their complex petrophysical behavior where in contrast to siliciclastic rocks different parameters including porosity and permeability usually are not directly related this behavior is the result of thorough reorganization of porosity during diagenesis and it turns prediction of reservoir quality of carbonate rocks into a challenge the study presented here deals with the problem of utilizing nmr techniques in prediction of petrophysical properties in carbonates we employ a visual porosity classification as a priori knowledge for better interpreting nmr data for prediction purposes this allows for choice of suitable t2 cutoff values to differentiate movable from bound fluids adapted for the specific carbonate rock thus resulting in better interpretation of nmr data the approach of using a genetic pore type classification for adapting the conventional method for t2 cutoff determination which originally was developed for siliciclastic rocks is promising similarly for permeability determination on the basis of nmr measurements the classification of carbonate rocks based on porosity types also shows potential the approach implemented here has the promise to provide a basis of standardized interpretation of nmr data from carbonate rocks

long term persistence of oil from the exxon valdez spill in two layer beaches oil spilt from the tanker exxon valdez more than 20 years ago still persists in the gravel beaches of prince william sound alaska field data and numerical modelling indicate that some of the oil was trapped in the anoxic environment of the lower layers of the beaches when the water table was low oil spilled from the tanker exxon valdez in 1989 refs 1 2 persists in the subsurface of gravel beaches in prince william sound alaska the contamination includes considerable amounts of chemicals that are harmful to the local fauna3 however remediation of the beaches was stopped in 1992 because it was assumed that the disappearance rate of oil was large enough to ensure a complete removal of oil within a few years here we present field data and numerical simulations of a two layered beach with a small freshwater recharge in the contaminated area where a high permeability upper layer is underlain by a low permeability lower layer we find that the upper layer temporarily stored the oil while it slowly and continuously filled the lower layer wherever the water table dropped below the interface of the two layers as a result of low freshwater recharge from the land once the oil entered the lower layer it became entrapped by capillary forces and persisted there in nearly anoxic conditions that are a result of the tidal hydraulics in the two layered beaches we suggest that similar dynamics could operate on tidal gravel beaches around the world which are particularly common in mid and high latitude regions4 5 with implications for locating spilled oil and for its biological remediation

the effect of a percolation threshold in the kozeny carman relation one of the most important properties of reservoir rocks and perhaps the most difficult to predict is permeability laboratory studies have shown that permeability depends on a long list of parameters porosity pore size and shape clay content stress pore pressure fluid type saturation a nearly overwhelming complexity in spite of this the essential behavior can often be expressed successfully using the remarkably simple kozeny carman kozeny 1927 carman 1937 1956 bear 1972 scheidegger 1974 relation b 3s2 where is the permeability is the porosity s is the specific surface area pore surface area per volume of rock and b is a geometric factor

predicting the permeability of sediments entering subduction zones using end member permeabilities defined by a worldwide compilation of sediment permeabilities at convergent margins we compare permeability predictions using a geometric mean and a two component effective medium theory emt our implementation of emt includes a threshold fraction of the high permeability component that determines whether flow occurs dominantly in the high or low permeability component we find that this threshold fraction in most cases is equal to the silt sand sized fraction of the sediment this suggests that sediments undergoing primary consolidation tend to exhibit flow equally distributed between the high and low permeability components we show that the emt method predicts permeability better than the weighted geometric mean of the end member values for clay fractions 0 6 this work provides insight into the microstructural controls on permeability in subducting sediments and valuable guidance for locations which lack site specific permeability results but have available grain size information

isotope studies of granitoids from the bangenhuk formation ny friesland caledonides svalbard the caledonian hecla hoek succession in ny friesland eastern svalbard has been interpreted for many decades to be a continuous stratigraphic sequence early palaeozoic and neoproterozoic strata

fractal measurements of sandstones shales and carbonates measurements were made of the fractal properties of sandstones shales and carbonates using a statistical analysis of structural features on fracture surfaces fractal behavior is associated with power law behavior for the number of features as a function of the feature size on the pore rock interface only one sedimentary rock a novaculite was found not to have a fractal structure the fractal dimensions range from 2 27 to 2 89 and the long length limits to the fractal regime range from 2 m to over 50 m in all cases the fractal behavior extends to less than 0 2 m which is the measurement resolution the porosity associated with the fractal pore rock interface can be calculated from the fractal parameters some of the samples have additional porosity not associated with power law behavior photographs and other evidence are used to show that the fractal structures are the result of diagenesis fractal diagenetic structures include euhedral quartz overgrowths druse quartz calcite dolomite clays and chert

continental delamination insights from laboratory models 1 one of the major issues of the evolution of continental lithospheres is the detachment of the lithospheric mantle that may occur under certain conditions and its impact on the surface in order to investigate the dynamics of continental delamination we performed a parametric study using physically scaled laboratory models the adopted setup is composed of a three layers visco elastic body analog for upper crust lower crust lithospheric mantle locally thickened thinned to simulate a density anomaly lithospheric root and an adjacent weak zone lying on a low viscosity material simulating the asthenosphere the results emphasize the interplay between mantle flow deformation surface topography and plate motion during a three phases process 1 a slow initiation phase controlled by coupling and bending associated with contraction and dynamic subsidence 2 lateral propagation of the delamination alongside with extension and a complex topographic signal controlled by coupling and buoyancy while poloidal mantle flow develops around the tip of the delaminating lithospheric mantle and 3 a late phase characterized by a counterflow that triggers retroward motion of the whole model a semiquantitative study allows us to determine empirically two parameters 1 an initiation parameter that constrains the propensity of the delamination to occur and correlates with the duration of the first stage 2 a buoyancy parameter characterizing the delamination velocity during late stages and therefore its propensity to cease finally we point out similarities and differences with the sierra nevada california usa in terms of topography deformation and timing of delamination

estimating irreducible water saturation and permeability of sandstones from nuclear magnetic resonance measurements by fractal analysis abstract understanding the relationships between the pore structure and bulk properties such as irreducible water saturation swir and permeability k of rocks is a crucial problem in geoscience in this study two types of fractal dimension were determined from nuclear magnetic resonance nmr t2 relaxation time distribution and models for estimating swir and k using fractal theory were proposed in view of the data of sandstone samples from upper paleozoic formation in china we found a good agreement between the predicted swir values based on fractal analysis and the experimental measurements and the estimated k values based on the proposed model are within one order of magnitude of measured k additionally another four frequently used k estimation models were compared with our proposed model and the result support that the proposed approach has great potential in investigating k while certain limitation still exists this procedure was applied on another set of sandstone samples collected from a different location and the predicted permeability values are reliable our study suggests that the proposed swir estimation model using nmr t2 data and fractal dimensions provides useful insights into characterizing the pore space properties of sedimentary rocks our work demonstrates that we can use nmr data to infer swir directly and the estimated swir value can be well integrated in permeability prediction model which improves the applications of nmr in characterizing the properties related to rock pores

elastic waves push organic fluids from reservoir rock 1 elastic waves have been observed to increase productivity of oil wells although the reason for the vibratory mobilization of the residual organic fluids has remained unclear residual oil is entrapped as ganglia in pore constrictions because of resisting capillary forces an external pressure gradient exceeding an unplugging threshold is needed to carry the ganglia through the vibrations help overcome this resistance by adding an oscillatory inertial forcing to the external gradient when the vibratory forcing acts along the gradient and the threshold is exceeded instant unplugging occurs the mobilization effect is proportional to the amplitude and inversely proportional to the frequency of vibrations we observe this dependence in a laboratory experiment in which residual saturation is created in a glass micromodel and mobilization of the dyed organic ganglia is monitored using digital photography we also directly demonstrate the release of an entrapped ganglion by vibrations in a computational fluid dynamics simulation

age differences between rbsr whole rock and upb zircon ages of syn and postorogenic svecokarelian granitoids in sottunga sw finland abstract the u pb age on pooled data of zircnos from the postorogenic svecokarelian mosshaga granite is 1788 11 ma 2 the corresponding rb sr whole rock age is 1742 34 ma 2 the mosshaga granite intrudes a synorogenic granodiorite which has a u pb zircon age of 1889 10 ma and a rb sr whole rock age of 1850 28 ma the age differences between the u pb zircon ages and rb sr whole rock ages are concluded to be geologically significant it is shown that the mosshaga pluton cooled rapidly and as a consequence the rb sr isotopic system closed at a time very close to the crystallization of the zircons a commonly observed feldspar and biotite alteration in svecokarelian granitoids indicates migration of rb and sr isotopes in the whole rock system which may lead to apparently younger rb sr ages

near surface thermal chemical boundary layer convection at infinite prandtl number two dimensional numerical experiments chemical differentiation and convective removal of internal heat make the earth s lithosphere a thermal and a chemical boundary layer thin layers of chemically light material form near the earth s surface and become embedded within the cold thermal boundary layer associated with interior heat removal the likelihood of near surface thermal and chemical boundary layer interactions influencing the earth s thermotectonic evolution prompts the models presented herein a simplified system consisting of a chemically light layer within the upper thermal boundary layer of a denser thermally convecting layer is explored through a suite of numerical experiments to see how its dynamic behaviour differs from similar well studied thermal boundary layer systems a major cause of differences between the two systems resides in the ability of the deformable near surface chemical layer to alter the effective upper thermal boundary condition imposed on the convectively unstable layer below in thermal equilibrium regions of chemical boundary layer accumulation locally enforce an effectively near constant heat flux condition on the thermally convecting layer due to the finite thermal conductivity of chemical boundary layer material for cases in which chemical accumulations translate laterally above the unstable layer the thermal coupling condition between chemical boundary layer material and the unstable layer below is one of non equilibrium type i e the thermal condition at the top of the convectively unstable layer is time as well as space variable a second major cause of differences is that for the thermal chemical system chemically induced rheologic variations can offset or compete with those due to temperature more specifically the presence of chemically weak material can lubricate convective downwellings allowing for enhanced overturn of an on average strong upper thermal boundary layer both of these factors have low order effects on internal flow structure and heat loss and lead to dynamic behaviour in which chemical boundary layer deformation is not only driven by flow in the thermally convecting interior layer but also feeds back and alters this flow some implications of this in regard to elucidating how near surface chemical boundary layer deformation e g continental tectonics might interact with and influence mantle convection are discussed

bending mechanics and mode selection in free subduction a thin sheet analysis summary to elucidate the dynamics of free buoyancy driven subduction of oceanic lithosphere i study a model in which a 2 d sheet of viscous fluid with thickness h and viscosity 1 subducts in an infinitely deep ambient fluid with viscosity 1 numerical solutions for the sheet s evolution are obtained using the boundary element method bem starting from an initial configuration comprising a short protoslab attached to a longer horizontal plate that is free to move laterally beneath an impermeable traction free surface interpretation of the solutions using thin viscous sheet theory shows that the fundamental length scale controlling the subduction is the bending length lb defined at each instant as the length of the portion of the sheet s midsurface where the rate of change of curvature is significant geophysically speaking lb is the sum of the lengths of the slab and of the region seaward of the trench where flexural bulging occurs the bending length in turn enters into the definition of the sheet s dimensionless stiffness s h lb 3 which controls whether the sinking speed of the slab is determined by the viscosity of the sheet itself s 1 or by that of the ambient fluid s 1 motivated by laboratory observations of different modes of subduction retreating versus advancing trench folding versus no folding etc in fluid layers with finite depth i calculate numerically the dip d of the slab s leading end as a function of and the normalized depth d h to which it has penetrated the contours of the function d d h strongly resemble the intermode boundaries in the laboratory based regime diagram of schellart supporting the hypothesis that the mode of subduction observed at long times in experiments is controlled by the dip of the slab s leading end when it reaches the bottom of the layer in particular the bem solutions explain why trenches advance in the laboratory only when lies in an intermediate range and why they retreat when is either smaller or larger than this application of the bem model to wu et al s compilation of the minimum curvature radii of subducted slabs suggests 140 510 for the earth this is too small to permit the laboratory type trench advancing mode in agreement with the lack of tomographic evidence for slabs that are bent over backwards

permeability prediction for low porosity rocks by mobile nmr estimating permeability from nmr well logs or mobile nmr core scanner data is an attractive method as the measurements can be performed directly in the formation or on fresh cores right after drilling furthermore the method is fast and non destructive compared to t 1 relaxation times commonly measured t 2 distributions are influenced by external and internal magnetic field gradients we performed two dimensional t 1 and t 2 relaxation experiments on samples of rhaetian sandstone a rock with low porosity and small pore radii using a mobile nmr core scanner which operates within a nearly homogeneous static magnetic field because small pore sizes are associated with high internal magnetic field gradients standard methods from nmr logging in the oil industry cannot be applied for accurate permeability prediction therefore a new model theory was developed which describes the pore radius dependence of the surface relaxivity p 2 by both an analytical and a more practical empirical equation using corrected p 2 values permeability can be predicted accurately from the logarithmic mean of the t 2 distribution and the physically based kozeny carman equation additional core plug measurements of structural parameters such as porosity permeability specific inner surface area and pore radius distributions supported the nmr results

cenozoic tectonic evolution of the new zealand plate boundary zone a paleomagnetic perspective abstract new zealand straddles the obliquely convergent boundary between the pacific and australian plates with subduction of pacific plate along the hikurangi margin finite plate reconstructions predict 800 km of relative plate motion since 43 ma with 80 90 clockwise rotation of the hikurangi margin since 20 ma at an average rate of 4 4 5 myr and the short term deformation

investigation of porosity and permeability effects from microstructure changes during limestone dissolution we studied experimentally the dissolution of a porous limestone core during co2 enriched water injection we measured the changes in porosity and permeability arising from modifications of the pore network geometry and the fluid rock interface a methodology based on periodic x ray microtomography imaging was implemented to record the evolution of the time and scale dependent microstructures with a spatial resolution of 4 91 m two processes were successively involved in the rapid permeability increase of the sample as documented from microscale to core scale measurements

geodynamic models of mature continental collision evolution of an orogen from lithospheric subduction to continental retreat delamination 1 the behavior of deep lithospheric processes in continental collision are frequently speculated on but poorly understood in this study we build on previous work to explore the styles of continental lithosphere deformation during mature collision where 1800 km of convergence has been accommodated by horizontal shortening we conducted a suite of numerical geodynamic experiments that test the sensitivity of mature continent collision to varying mantle lithosphere density mantle lithosphere yield stress lower crustal strength and to the presence of phase change related density changes in the lower crust i e eclogitization of mafic lower crust the models suggest that the early stages of collision are accommodated by subduction of lower crust and mantle lithosphere along a discrete shear zone beneath the overriding plate following this initial stage of subduction the subducting lower crust and mantle lithosphere can retreat from the collision zone permitting the sub lithospheric mantle to upwell and intrude the overriding plate as a result the lower crust and mantle lithosphere of the overriding plate delaminate from the overlying crust with local isostatic adjustment subduction and delamination driven crustal processes plateau like uplift occurs the sub crustal evolution also causes bands of syn convergent crustal extension to develop in models with a rheologically weaker lower crust surface crustal response to the deep lithosphere dynamics becomes more diffuse as an example the numerical experiments satisfy a number of surface observables of the himalayan tibetan orogen namely 1 the current general mantle lithosphere architecture as defined by seismic analyses 2 the long wavelength plateau uplift of the western tibetan plateau 3 the surface heat flow measurements in india the tethyan himalaya qiangtang and in qaidam basin and 4 the anomalous syn convergent extension in the southern portion of the orogen

whole grain evaporation for 207 pb 206 pb age investigations on single zircons using a double filament thermal ion source a technique has been developed and tested to analyse 207pb 206pb apparent ages by thermal evaporation of radiogenic lead directly from untreated whole zircon grains 0 3 mm the evaporation analyses are performed in the double filament arrangement of a thermal ion mass spectrometer thims the method is a powerful tool to distinguish between different lead components occurring in the same grain because differing activation energies of the competing lead components cause their sequential evaporation from the zircons the evaporation of test samples results in 207pb 206pb apparent ages in good agreement with u pb ages known from literature single zircons from a granite of the marble mountains california yield an age of crystallization of 1 410 30 ma ceylon zircons from heavy mineral bearing gravels yield 560 40 ma as age of crystallization of the pegmatitic gravel sources individuals from a heterogeneous zircon population of a diatexite from the southern schwarzwald sw germany indicate metamorphic zircon formation around 500 ma and the existence of middle proterozoic relics 1 95 0 05 ga

variation of permeability with porosity in sandstone diagenesis interpreted with a fractal pore space model permeability is one of the key rock properties for the management of hydrocarbon and geothermal reservoirs as well as for aquifers the fundamental equation for estimating permeability is the kozeny carman equation it is based on a capillary bundle model and relates permeability to porosity tortuosity and an effective hydraulic pore radius which is defined by this equation whereas in clean sands the effective pore radius can be replaced by the specific surface or by the grain radius in a simple way the resulting equations for permeability cannot be applied to consolidated rocks based on a fractal model for porous media equations were therefore developed which adjust the measure of the specific surface and of the grain radius to the resolution length appropriate for the hydraulic process these equations are calibrated by a large data set for permeability formation factor and porosity determined on sedimentary rocks this fractal model yields tortuosity and effective pore radius as functions of porosity as well as a general permeability porosity relationship the coefficients of which are characteristic for different rock types it can be applied to interpret the diagenetic evolution of the pore space of sedimentary rocks due to mechanical and chemical compaction with respect to porosity and permeability

lateral migration of a foundering high density root insights from numerical modeling applied to the southern sierra nevada abstract the southern sierra nevada is a geodynamically complex region where several models have been proposed to explain the rapid removal of lithospheric mantle occurring sometime between 8 0 and 3 5 ma tomographic studies show the presence of an east dipping slab shaped fast seismic anomaly reaching to about 300 km depth below the western sierras and great valley and receiver function studies indicate a broad region of lithosphere removal this work presents thermo mechanical modeling of asymmetric foundering of a high density batholithic root with lateral intrusion of asthenospheric material the predicted evolution is controlled by a the upwelling of buoyant asthenosphere facilitated by the presence of a weakened lithospheric mantle adjacent to a dense batholitic root b the westward inflow enabled by a low viscosity lower crust and c negative buoyancy of a batholithic dense root the dynamics of these models can be characterized as a slowly migrating lithosphere foundering process driven by the density anomaly of the ultramafic root but controlled by the magnitude of the lower crustal viscosity which determines the rate at which asthenospheric material can flow into the opening lower crustal gap final model predicted upper mantle structure is compatible with existing tomographic images and the observed v shape geometry of the moho below the western margin of the southern sierra nevada model predicted topography is also generally consistent with observations and shows a monotonous uplift of the high region since 7 ma and presently ongoing and an area of maximum subsidence west of the area of the v shaped moho due to the pull exerted by the sinking of the high density root

permeability prediction from micp and nmr data using an electrokinetic approach theaccuratemodelingofoil gas andwaterreservoirsdependsfundamentallyuponaccesstoreliablerockpermeabilitiesthatcannotbeobtaineddirectlyfromdownholelogs instead a range of empirical models are usually employed we propose a new model that has been derived analytically from electrokinetic theory and is equally valid for all lithologies the predictions of the new model and four other common models kozeny carman berg swanson and van baaren have been compared using measurements carried out on fusedandunfusedglassbeadpacksaswellason91rocksamples representing 11 lithologies and three coring directions the new model provides the best predictions for the glass beadpacksaswellforallthelithologies thecruxofthenew modelistohaveagoodknowledgeoftherelevantmeangrain diameter forexample frommicpdata hence wehavealso predictedthepermeabilitiesof21northseawellcoresusing all five models and five different measures of relevant grain size these data show that the best predictions are provided by the use of the new model with the geometric mean grain size wehavealsoappliedthenewmodeltothepredictionof permeability from nmr data of a 500 m thick sand shale succession in the north sea by inverting the t2 spectrum to provide a value for the geometric mean grain size the new model shows a good match to all 348 core measurements fromthesuccession performingbetterthanthesdr timurcoates hscm andkozeny carmanpredictions