experimental study of fluid transport processes in the matrix system of the european organic rich shales i scandinavian alum shale abstract this contribution presents results from a laboratory study investigating the fluid gas water transport properties in the matrix system of the scandinavian alum shale the maturity of the organic matter of the shale samples ranged between 0 5 and 2 4 vitrinite reflectance vr r gas he ar ch 4 and water flow properties were determined at effective stresses ranging between 5 and 30 mpa and a temperature of 45 c the effects of different controlling factors parameters on the fluid conductivity including permeating fluid moisture content anisotropy heterogeneity effective stress pore pressure and load cycling were analyzed and discussed pore volume measurements by helium expansion were conducted under controlled in situ effective stress conditions on a limited number of plugs drilled parallel and perpendicular to bedding for alum shale the intrinsic permeability coefficients measured parallel and perpendicular to bedding 6 10 22 8 10 18 m 2 were within the range previously reported for other shales and mudstones permeability coefficients were strongly dependent on permeating fluid moisture content anisotropy effective stress and other sample to sample variations the intrinsic absolute permeabilities measured with helium were consistently higher up to five times than those measured with argon and methane permeability coefficients he ch 4 measured on a dry sample were up to six times higher than those measured on an as received sample depending on effective stress the effect of moisture on measured permeability coefficients became more significant as effective stress increased permeability coefficients he ch 4 measured parallel to bedding were up to more than one order of magnitude higher than those measured perpendicular to bedding parallel to bedding all samples showed a nonlinear reduction in permeability with increasing effective stress 5 30 mpa the stress dependence of permeability could be well described by an exponential relationship

near inertial internal wave interactions with mesoscale fronts observations and models moored observations of near inertial currents and buoyancy fluctuations from the frontal air sea interaction experiment fasinex may be understood as nearinertial internal waves reflecting off sheared background currents the fasinex moored array measured upper ocean currents temperature and conductivity between january and june 1986 in a region of the sargasso sea heavily populated by strong upper ocean fronts the background jets associated with these features have typical cross front scales of 20km maximum currents of 0 5 m s 1 and relative vorticities of 0 3 in the vicinity of fronts observed near inertial currents have short horizontal scales show no clear horizontal phase structure and trace out elongated current ellipses with elevated across front over along front variance during these periods inertial band pass buoyancy fluctuations often correlate with major axis currents wkb ray tracing models of propagating monochromatic plane waves exhibit horizontal phase propagation and correlations between minor axis currents and buoyancy and thus cannot explain these results models of near inertial internal waves reflected or trapped by a barotropic frontal jet produce mode like structures with short horizontal scales little horizontal phase propagation and anisotropic current ellipses aligned primarily cross front model buoyancy may correlate with one or both current ellipse components depending on the incidence angle of the wave and the degree to which it reflects completely reflected waves with horizontal scales similar to those of the front and near normal incidence angle produce current ellipses and correlation patterns consistent with the observations

upper ocean temperature structure inertial currents and richardson numbers observed during strong meteorological forcing abstract upper ocean currents and temperature in the northeastern pacific were measured during a 14 day period in november 1980 as part of strex velocities in the upper ocean are dominated by near inertial frequency oscillations thew oscillations are modified by wind stress variations associated with the passage of a strong cold front the change in the inertial currents both in the mixed layer and below is qualitatively consistent with linear internal wave dynamics if turbulent stresses during the storm are assumed to extend 10 20 m below the mixed layer the ratio of mean squared buoyancy frequency n2 and mean squared shear s2 computed over a 10 m interval defines an average richardson number r0 n2 s2 r0 is approximately 2 5 except in regions of high inertial shear in particular values as low as 0 7 are obtained in a 20 m thick region immediately below the base of the mixed layer the data are consistent with a model of the oecanic shear field consisting of a background shear corresponding to a va

on the response of the ocean to a moving storm the nonlinear dynamics abstract a novel and efficient numerical method is used to investigate the nonlinear equations of motion for the upper layer of a two layer ocean in which the lower layer is infinitely deep and at rest the efficiency is achieved by seeking solutions that are in a steady state translating in equilibrium with the storm oscillations are found in the wake of the storm two features of the response are attributed to the nonlinear terms in the equation of motion 1 a rapid transition from a maximum in the downwelling phase to a maximum in the upwelling phase of each oscillation followed by a gradual relaxation to the next downwelling maximum and 2 a displacement of the maximum response usually to the right of the storm track by 40 km it is shown that the horizontal pressure gradient terms can be neglected from the momentum equations for fast large storms in which case a lagrangian integration can be performed following fluid particles this enables feature 1 to be attributed to the along tra

the subthermocline lens d1 part i description of water properties and velocity profiles abstract one remarkable result of the local dynamics experiment in polymode is the discovery of a large number of small energetic eddies using ctd data sofar float tracks and profiles of absolute velocity we describe one of these features the subthermocline eddy d1 the feature has an advective time scale of 1 day and its primary mode of movement is advection by the ambient flow field the eddy is resolved into a coordinate system moving with the velocity of the ambient flow which ranges from 11 16 cm s 1 its phase speed is less than 2 cm s 1 the eddy is a lens centered at 1500 db velocity profiles show the lens has no detectable signal in and above the main thermocline or below about 3000 db its subsurface velocity maximum is 28 6 cm s 1 at 1500 db 15 km from the center the radial variation of the azimuthal velocity is gaussian inside the velocity maximum but decays as e br beyond there is little evidence of the eddy beyond a radius of 25 km inside the velocity maximum the eddy is characte

near inertial wave interactions with mean flow and bottom topography near caryn seamount abstract velocity measurements near caryn seamount in the sargasso sea reveal intensified mean and near inertial motions in the upper ocean embedded in a regional eastward flow is an anticyclonic eddy that appears to be tied to the topography an energetic downward propagating near inertial wave packet is found at the eddy s base this wave appears to be trapped in the eddy undergoing critical layer amplification as it tries to leave near the bottom enhanced upgoing near inertial wave energy is found within 1000 m of the top of the seamount

change in composition and pore structure of longmaxi black shale during oxidative dissolution abstract owing to the presence of chemically unstable compositions e g clay minerals carbonate pyrite and organic matter om which are closely related to shale structure failures or dissolution pores the methods to increase gas well long term productivity from tight shale matrix need to take into account the chemical interaction of shale with injected fluid in this study black shale samples obtained from lower silurian longmaxi formation in sichuan basin china were treated with 15 wt hydrogen peroxide h2o2 for the comprehensive understanding of the change in shale composition and the associated dissolution structures the measurements of mass loss total organic carbon content and mineralogical composition showed that carbonate reductive inorganic minerals containing ferrous iron e g pyrite and chlorite and om in samples exhibited strong dissolution however the other minerals behaved in a non reactive manner at the experimental time scale after the oxidative treatment for 240 h a large amount of oxidation induced fractures and dissolution pores were observed by field emission scanning electron microscopy the fractures mainly oriented parallel to lamination were attributed to the dissolution of om and structural alteration of clay minerals all the dissolution pores seemed to be strongly dependent on the loss of dolomite pyrite and om results from high pressure mercury intrusion and low pressure nitrogen adsorption analysis showed that these dissolution pores ranging from 10 to 500 nm in diameter exhibited a significant increase in pore volume due to the removal of interconnected pore filling om while the volume of pores 1 m in size exhibited a minor increase because the micrometer size dissolved particles appeared to be discrete or unconnected thus the oxidative dissolution could lead to the higher porosity and better connectivity of nanometer size pore networks in shale samples the induced fractures reduced the size of diffusion dominant zones in shale matrix and the dissolution pores increased the size of gas transport pathways into fractures these results indicate that the injection of h2o2 may play an important role in shale matrix stimulation by oxidative dissolution which is likely to improve matrix diffusivity

observations of internal wave reflection off sloping bottoms current and temperature spectra exhibit intensification and polarization near sloping bottoms over a band of frequencies centered at the local internal wave critical frequency examples are drawn from a variety of island seamount and continental slope observations waves propagating down from mid depth change energy density wave number and azimuth when they reflect off the bottom providing a natural perturbation to the deep ocean interior internal wave spectrum deviations from linear theory are interpreted as evidence for dissipation through subsequent shear instability and or nonlinear interaction topographic features appear likely to be energy sinks for internal wave energy

internal inertial waves in a surgasso sea front abstract this work examines the presence of internal inertial waves in a front in the north atlantic subtropical convergence zone results of doppler shear profiler and towed thermistor chain surveys are displayed to document the position and magnitude of the front objective maps of the total measured velocity are computed and subtracted from the observed velocity fields the remaining wave signal is processed to yield horizontal towed and vertical dropped kinetic energy spectra across the front from these rotary spectra are also computed along the line of tow and in the vertical to determine the horizontal and vertical anisotropy it is found that several nearly monochromatic waves are propagating northward and southward from the front with horizontal length scales of 32 50 km it was also discovered that the region of anticyclonic frontal vorticity exhibits an excess of downgoing energy at the longest vertical wavelength thus sampled 50 m while the region of cyclonic vorticity possesses more

thermal maturity source rock potential and kinetics of hydrocarbon generation in permian shales from the damodar valley basin eastern india abstract this study investigates the source rock characteristics of permian shales from the jharia sub basin of damodar valley in eastern india borehole shales from the raniganj barren measure and barakar formations were subjected to bulk and quantitative pyrolysis carbon isotope measurements mineral identification and organic petrography the results obtained were used to predict the abundance source and maturity of kerogen along with kinetic parameters for its thermal breakdown into simpler hydrocarbons the shales are characterized by a high toc 3 4 mature to post mature heterogeneous type ii iii kerogen raniganj and barren measure shales are in mature late oil generation stage rr raniganj 0 99 1 22 rr barren measure 1 1 1 41 vitrinite is the dominant maceral in these shales barakar shows a post mature kerogen in gas generation stage rr barakar 1 11 2 0 and consist mainly of inertinite and vitrinite the 13corg value of kerogen concentrate from barren measure shale indicates a lacustrine marine origin 24 6 30 84 vs vpdb and that of raniganj and barakar 22 72 25 03 vs vpdb show the organic provenance to be continental the 13c ratio of thermo labile hydrocarbons c1 c3 in barren measure suggests a thermogenic source discrete bulk kinetic parameters indicate that raniganj has lower activation energies e 42 62 kcal mol compared to barren measure and barakar e 44 68 kcal mol temperature for onset 10 middle 50 and end 90 of kerogen transformation is least for raniganj followed by barren measure and barakar mineral content is dominated by quartz 42 63 siderite 9 15 and clay 14 29 permian shales in particular the barren measure as inferred from the results of our study demonstrate excellent properties of a potential shale gas system

the energy flux from the wind to near inertial motions in the surface mixed layer abstract time series of wind stress computed from long term meteorological buoy data off north america are used to examine the forcing of surface inertial currents by the wind a simple damped slab model of the mixed layer is used to compute h the average flux of energy from the wind to mixed layer inertial currents in a mixed layer of fixed depth h the forcing of mixed layer inertial motions is highly intermittent most of the forcing occurs during the winter months with a few dozen events accounting for typically over half the total energy flux major forcing events are usually associated with translating cold fronts or small lows with scales of about 100 km the larger synoptic scale features have little energy at the inertial frequency and thus result in only weak forcing of inertial currents a strong seasonal signal exists in the inertial forcing at ows p 50 n 145 w 50 m is largest from october to february and is a factor of 12 above the june and july values if seasonally varying

fine scale temperature variability the influence of near inertial waves measurements made with a towed thermistor chain and acoustic doppler current profiler in the seasonal thermocline of the sargasso sea are examined for relationships among small scale temperature activity shear and internal wave variability patches of intense activity measuring 5 10 m high and several kilometers in length are found to persist within a near inertial wave packet the packet was tagged with a drogue and followed for about 16 hours as it was advected along an edge of a cold core ring the patches occur along surfaces of high vertical shear where the richardson number 7 m vertical resolution falls to values less than one within the patches are groups of small scale internal waves and fluid overturns the overturns are 1 3 m high and are associated with wave breaking events away from the wave packet activity levels are less and the active fraction of the water column appears to be linked to variability in the internal wave field it is conjectured that the near inertial wave patches are the same species as persistent mixing patches observed by gregg et al 1986 which were also associated with a near inertial wave

statistics of mixing patches observed in the sargasso sea temperature measurements made with a towed thermistor chain in the seasonal thermocline of the sargasso sea have been converted to sections of fine structure activity by normalizing values of meter scale horizontal fluctuations by the local vertical gradient individual patches of high activity are then separated from background and examined for length l height h aspect ratio l h and signal intensity over the range 0 5m h 20m and 30 m l 2 km the aspect ratio tends to be about 100 similar to reports of turbulent patches measured with velocity microstructure profilers numbers of patches decrease with increasing patch height and length and large patches tend to have higher activity levels

interaction of superinertial waves with submesoscale cyclonic filaments in the north wall of the gulf stream abstracthigh resolution nearly lagrangian observations of velocity and density made in the north wall of the gulf stream reveal banded shear structures characteristic of near inertial waves niws here the current follows submesoscale dynamics with rossby and richardson numbers near one and the vertical vorticity is positive this allows for a unique analysis of the interaction of niws with a submesoscale current dominated by cyclonic as opposed to anticyclonic vorticity rotary spectra reveal that the vertical shear vector rotates primarily clockwise with depth and with time at frequencies near and above the local coriolis frequency f at some depths more than half of the measured shear variance is explained by clockwise rotary motions with frequencies between f and 1 7f the dominant superinertial frequencies are consistent with those inferred from a dispersion relation for niws in submesoscale currents that depends on the observed aspect ratio of the wave shear as well as the vertical vorticity

wind forced internal waves in the north pacific and sargasso sea abstract the three dimensional structure of the near inertial frequency internal wave field was measured at two open ocean sites using expendable velocity profilers both wave fields appear to be dominantly wind forced although their vertical structure and horizontal scales are quite different the hydro 79 data were taken in the sargasso sea in september 1979 the internal wave field is predominantly downward propagating and vertically uniform when wkb scaled in the upper 800 m of the ocean the energy density is roughly equal to munk s 1981 universal value the stkex data were taken during a period of strong storms in the northeastern pacific ocean in november 1980 in the upper few hundred meters the wave field is five times larger horizontally and five times more energetic when wkb scaled than the hydro 79 wave field measurements made after the passage of a strong cold front show an even more energetic and larger scale wave field extending to 500 m comparison with the simulations of price 198

importance of rock properties on the producibility of gas shales abstract as the development of unconventional gas resources has progressed the heterogeneity and complexity of shales as gas and oil reservoirs have become apparent the production histories from shales both within a sequence of interbedded strata and from adjacent wells commonly exhibit inexplicable variations and predictions from numerical modeling are rarely accurate as a result of the variability in the reservoir and rock parameters of gas shales the complex interaction between the shale properties and the producibility of the reservoir is seldom apparent one of the most difficult parameters to quantify is the fabric this study compares the relative importance of the fabric parameters of gas shales on their producibility using a commercial numerical simulator and field and laboratory determined rock properties the fabric parameters include the stress dependent fracture permeability which controls the gas transport through the fracture network as well as the effective fracture spacing which controls the path length for gas transport through the matrix and the stress dependent matrix permeability which controls the gas transport through the matrix the results of the numerical simulations show that for a wide range of stress dependent fracture permeabilities stress dependent matrix permeabilities and fracture spacings the productivity of a gas shale reservoir is limited by inefficient gas transport through the matrix the matrix permeability below which gas production is subeconomic is not a specific value but varies with the effective fracture spacing and with fracture permeability the matrix permeability and effective fracture spacing have a greater impact on the producibility of strata with larger fracture permeabilities the influence of the effective fracture spacing on production is greater than the influence of the matrix permeability the lower production associated with a large fracture spacing or a small matrix permeability can be offset by a large matrix permeability or a small fracture spacing the production simulations also show the strong dependence on the geomechanical properties of the rock which affect how the gas transport through the matrix and fractures changes with stress the influence of the geomechanical properties on the producibility depends on whether the production is limited by the gas transport through the matrix when the fabric parameters result in a matrix independent production small fracture spacing large matrix permeability small fracture permeability the production is solely controlled by the stress dependent fracture permeability with larger initial fracture permeability larger young s modulus and larger poisson s ratio resulting in higher production in this case young s modulus is much more influential than the poisson s ratio when the fabric parameters result in a matrix limited production the rock mechanics parameter which relates the exponential decline of matrix permeability with effective stress has the strongest influence on the producibility the influence of poisson s ratio on producibility not only varies with the fabric parameters but also with the young s modulus and when the production is matrix limited a smaller poisson s ratio results in a higher production for all cases except when both and young s modulus are small

the mesoscale spatial structure and evolution of dynamical and scalar properties observed in the northwestern atlantic ocean during the polymode local dynamics experiment abstract dynamical properties examined in this paper are the dynamic height and the pressure on an isopycnal scalars are the salinity and the oxygen concentration on an isopycnal the sea surface temperature and salinity are also examined these properties are obtained from the spatially uniform and densely sampled hydrographic surveys conducted during a two month period of the polymode local dynamics experiment in 1978 near 31 n 69 5 w the spatial maps of the dynamic height and the pressure of an isopycnal show that the baroclinic current in this area sometimes intensifies to a jetlike flow and at other times has the shape of elongated eddies the current flows primarily in the ne sw direction westward propagation occurs but varies in time and with depth eddies that transport water properties are also observed in this area the salinity and the oxygen on an isopycnal are found to be correlated with itself and with each other from the surface to the 18 c water layer within a 200 db range in the ther

on the response of the ocean to a moving storm parameters and scales abstract this paper has two purposes one is to present a new and efficient multilevel numerical model for calculating the response of the ocean to a moving storm the second is to show how on a time scale of a few inertial periods following the arrival of the storm the maximum horizontal and vertical velocities found in the wake can be calculated using a linear ekman model and a knowledge of that part of the change in the depth of the wind mixed layer due to entrainment this is demonstrated over a range of experiments with the multilevel numerical model these integrate the full nonlinear equations of motion with realistic ocean stratification and involve substantial entrainment of water into the wind mixed layer it is also shown that on this time scale the horizontal currents are confined near the surface but that the vertical velocity field extends throughout the depth of the ocean it is shown in appendix b that the wind forcing need only be large or fast for the forced response not to feel t

on the behavior of internal waves in the wakes of storms abstract the rossby adjustment process in the wake of a storm is studied with a view to finding within the context of linear theory how wave dispersion in both the vertical and meridional directions spreads energy which is initially confined entirely to the mixed layer comparisons are made between three cases 1 a periodic storm on the f plane where dispersion is purely vertical 2 a bounded storm on the f plane and 3 a bounded storm centered 2700 km from the equator on an equatorial beta plane particular attention is paid to the initial rate of loss of energy from the mixed layer and some simple formulas which work very well in the cases studied are derived these show that the rate of loss goes up when the mixed layer depth is increased and also that the rate scales as the square of the wavenumber values of the rates are sufficient to provide a major source of energy for internal waves below the mixed layer the often observed tendency for phase lines to propagate upward is found in all case

a near inertial internal wave spectrum for the sargasso sea in late summer abstract independent estimates of the frequency wavenumber spectrum of near inertial waves for the sargasso sea in late summer were made using 8 time series of horizontal velocity from a single moored vertical array and 58 vertical profiles of horizontal velocity from a horizontal array of expendable velocity profilers the profiler data were analyzed to produce an internal wave frequency wavenumber spectrum with sufficient resolution to resolve the details of the inertial peak and compute the vertical energy flux comparison with the lower resolution spectrum from the moored array shows qualitative agreement the differences are most likely due to biases in both techniques and to intermittency of the internal wave field these data reveal a marked asymmetry of the near inertial internal wave field with a net downward enemy flux of 0 12 0 12 ergs cm 2 s 1 the downward propagating waves have more energy a larger horizontal scale and a lower frequency than the upward propagating waves the magnitude of t

the nature of the l chondrite parent body s disruption as deduced from high pressure phases in the sixiangkou l6 chondrite the disruption of the l chondrite parent body lcpb at similar to 470ma is currently the best documented catastrophic celestial impact event based on the large number of l chondritic materials associated with this event uranium lead u pb dating of apatite and its high pressure decomposition product tuite in the sixiangkou l6 chondrite provides a temporal link to this event the u pb system of phosphates adjacent to shock melt veins was altered to varying degrees and the discordance of the u pb system correlates closely with the extent of apatite decomposition this suggests that the u pb system of apatite could be substantially disturbed by high temperature pulse during shock compression from natural impacts at least on the scale of mineral grains although many l chondrites can be temporally related to the catastrophic lcpb impact event the shock conditions experienced by each individual meteorite vary this could be due to the different geologic settings of these meteorites on their parent body the shock pressure and duration derived from most meteorites may only reflect local shock features rather than the impact conditions although they could provide lower limits to the impact conditions the sixiangkou shock duration similar to 4s estimated from high pressure transformation kinetics provides a lower limit to the high pressure pulse of the lcpb disruption impact combined with available literature data of l chondrites associated with this impact event our results suggest that the lcpb suffered a catastrophic collision with a large projectile with a diameter of at least 18 22km at a low impact velocity 5 6kms 1 this is consistent with astronomical estimates based on the dynamical evolution of l chondritic asteroids

near inertial motions over a mid ocean ridge effects of topography and hydrothermal plumes we investigate the spatial structure of near inertial motions in the vicinity of the endeavour segment of juan de fuca ridge approximately 48 n 129 w in the northeast pacific ocean on the basis of time series current and water property data collected from september 1984 to september 1987 near inertial motions are ubiquitous features of the 2200 m water column with root mean square rms current speeds comparable to those of the dominant m2 tidal currents within the lower 1000 m of the water column where most of the observations were obtained near inertial oscillations have rms current speeds of o 1 cm s and vertical isotherm displacements of o 10 m the fluctuations are confined to the frequency band 0 966 1 079 f f is the local coriolis parameter and have characteristic event durations of 1 week although the spectra of subsurface motions are dominated by the blue shifted superinertial band significant spectral peaks are found also in the subinertial and inertial frequency bands marked alteration of the near inertial current amplitudes occurs over two well defined depth zones within the study region within the 200 m zone immediately above the 2100 m ridge crest current amplitudes are amplified by a factor of 1 2 1 7 because of bottom reflection and or scattering of the downward propagating energy evidence that the amplification may be linked to bottom reflection rather than to scattering is provided by flattening and cross slope rotation of the near inertial current ellipses with increased proximity to the top of the ridge reflection would occur at grazing angles of less than 1 and would be associated with surface generated waves originating at distances of over 100 km from the observational site in contrast to the enhanced amplitudes immediately above the top of the ridge near inertial currents within the 1600 to 1800 m depth range undergo pronounced attenuation and frequency alteration amplitude attenuation is especially pronounced for motions in the superinertial band and may arise through critical layer absorption of downward propagating waves as they encounter increased vertical shear in the background flow the increased shear is most likely associated with buoyancy induced flow formed by the extensive hydrothermal plume emanating from vent sites in the axial valley along the ridge crest but it could also be related to bottom trapped oscillations over the steep ridge topography near inertial motions are estimated to have vertical coherence scales of the order of 10 100 m while horizontal coherence scales exceed the 50 km separation between the mooring locations minimum vertical and horizontal coherences are found for the depth zone 1600 1800 m while maximum correlation occurs for near bottom motions immediately above the crest of the ridge weak near inertial motions are observed within the 100 m deep axial valley

inertial wave dynamics in the north atlantic subtropical zone doppler current profiler observations of an inertial wave packet are presented from a region where a cold core ring impinges on a front in this intense current a drogue is deployed to mark one region of the fluid as the drogue is advected by the current the ship follows it zigzagging across the drogue s trajectory along this ship track vertical rotary velocity spectra indicate the presence of a downgoing intertial wave with a vertical wavelength which slowly changes from 50 to 100 m as time progresses the wave s intrinsic frequency was measured for the first time ever a horizontally synoptic data set is obtained at the drogue depth by correcting for frontal advection and the temporal rotation of the wave velocity examination of these synoptic data indicates the presence of a southgoing near inertial wave with horizontal wavelength 20 km the wave is confined to a 25 km region supplementary ray tracing calculations through objective maps of the ring flow field indicate that the wave is strongly influenced by doppler shifting this is accompanied by a slow counterclockwise turning of the horizontal wave number vector a decrease in the intrinsic frequency and an increase in the vertical wavelength in qualitative agreement with the data a companion paper marmorino et al this issue details the effect of this inertial wave upon the small scale temperature activity with horizontal length scales of 1 3 m

volumetric strain associated with methane desorption and its impact on coalbed gas production from deep coal seams the permeability of deep 1000 m 3300 ft coal seams is commonly low for deep coal seams significant reservoir pressure drawdown is required to promote gas desorption because of the langmuir type isotherm that typifies coals hence a large permeability decline may occur because of pressure drawdown and the resulting increase in effective stress depending on coal properties and the stress field during production however the permeability decline can potentially be offset by the permeability enhancement caused by the matrix shrinkage associated with methane desorption the predictability of varying permeability is critical for coalbed gas exploration and production well management we have investigated quantitatively the effects of reservoir pressure and sorption induced volumetric strain on coal seam permeability with constraints from the adsorption isotherm and associated volumetric strain measured on a cretaceous mesaverde group coal piceance basin and derived a stress dependent permeability model our results suggest that the favorable coal properties that can result in less permeability reduction during earlier production and an earlier strong permeability rebound increase in permeability caused by coal shrinkage with methane desorption include 1 large bulk or young s modulus 2 large adsorption or langmuir volume 3 high langmuir pressure 4 high initial permeability and dense cleat spacing and 5 low initial reservoir pressure and high in situ gas content permeability variation with gas production is further dependent on the orientation of the coal seam the reservoir stress field and the cleat structure well completion with injection of n2 and displacement of ch4 only results in short term enhancement of permeability and does not promote the overall gas production for the coal studied

turbulent mixing induced by upgoing near inertial waves in the seasonal thermocline of the norwegian sea acoustic doppler current profiler and towed thermistor chain measurements made in the seasonal thermocline in the norwegian sea are examined for evidence that near inertial shear leads to small scale turbulent mixing as inferred from meter scale temperature fluctuations for the 1 day of data examined here spatial variability in shear is dominated by near inertial waves having upward energy propagation 30 m vertical wavelength and 5 to 10 km horizontal extent 20 km wavelength repeated samples of one of these waves had high froude number and enhanced small scale variability dominated by 20 m long waveforms which we conjecture are kelvin helmholtz instabilities arising from the near inertial shear

mesoscale eddy internal wave coupling part i symmetry wave capture and results from the mid ocean dynamics experiment abstract vertical profiles of horizontal velocity obtained during the mid ocean dynamics experiment mode provided the first published estimates of the high vertical wavenumber structure of horizontal velocity the data were interpreted as being representative of the background internal wave field and thus despite some evidence of excess downward energy propagation associated with coherent near inertial features that was interpreted in terms of atmospheric generation these data provided the basis for a revision to the garrett and munk spectral model these data are reinterpreted through the lens of 30 years of research rather than representing the background wave field atmospheric generation or even near inertial wave trapping the coherent high wavenumber features are characteristic of internal wave capture in a mesoscale strain field wave capture represents a generalization of critical layer events for flows lacking the spatial symmetry inherent in a parallel shear flow or isolated vortex

near inertial wave wake of hurricanes katrina and rita over mesoscale oceanic eddies abstract tropical cyclones tcs katrina and rita moved as major hurricanes over energetic geostrophic ocean features in the gulf of mexico increased and reduced oceanic mixed layer oml cooling was measured following the passage of both storms over cyclonic and anticyclonic geostrophic relative vorticity g respectively this contrasting thermal response is investigated here in terms of the evolution of the storms near inertial wave wake in geostrophic eddies observational data and ray tracing techniques in realistic geostrophic flow indicate that tc forced oml near inertial waves are trapped in regions of negative g where they rapidly propagate into the thermocline these anticyclonic rotating regimes coincided with the distribution of reduced oml cooling because rapid downward dispersion of near inertial energy reduced the amount of kinetic energy available to increase vertical shears at the oml base by contrast tc forced oml near inertial waves were stalled in upper layers of cyclonic circula

variability of rock mechanical properties in the sequence stratigraphic context of the upper devonian new albany shale illinois basin abstract rock mechanical properties of tight shale reservoirs are important parameters in the exploration and development of unconventional shale oil and gas understanding the stratigraphic variability of rock mechanical properties in black shale successions is important for identifying promising intervals for hydraulic stimulation high resolution hardness tests 6 cm spacing with an equotip bambino 2 hardness tester were conducted on a new albany shale core to study the stratigraphic variability of rock mechanical properties combined with high resolution geochemical analyses 8 cm spacing acquired with a portable x ray fluorescence spectrometer it is possible to relate hardness variability to shale composition the results of our study suggest an average quartz content of about 28 for the entire succession approximately half of that amount 13 is interpreted to be of biogenic origin biogenic quartz mainly derived from dissolution of radiolaria occurs as authigenic quartz precipitated in tasmanites cysts and as microcrystalline quartz precipitated in the shale matrix petrographic observations indicate that the hardness of the new albany shale is critically controlled by biogenic quartz content not by total quartz content as suggested in multiple prior studies biogenic quartz forms an interconnected stiff framework which increases the hardness of shales in contrast dispersed hard grains e g detrital quartz feldspar and dolomite do not contribute to brittle behavior when examined under a scanning electron microscope hard shales are rich in biogenic quartz and contrast visibly with soft shales that are characterized by high contents of clay minerals negative correlation between hardness and al2o3 content as well as differential compaction of clay minerals around hard grains indicate that clay minerals are an important ductile component in the new albany shale although the general softness of kerogen suggests that there should be an influence of organic matter on hardness this effect is counteracted by biogenic quartz cementation which has a comparable stratigraphic distribution pattern we propose a new mineral composition based brittleness index on the basis of biogenic quartz content to characterize the brittleness of tight shale reservoirs within a sequence stratigraphic context the hardness of the new albany shale increases in transgressive systems tracts reaches a maximum at maximum flooding surfaces and decreases in highstand systems tracts with the exception of the blocher member maximum flooding surface intervals have the highest potential to develop brittle fractures and should be potential targets for hydraulic stimulation

thermal maturation of gas shale systems shale gas systems serve as sources reservoirs and seals for unconventional natural gas accumulations these reservoirs bring numerous challenges to geologists and petroleum engineers in reservoir characterization most notably because of their heterogeneous character due to depositional and diagenetic processes but also because of their constituent rocks fine grained nature and small pore size much smaller than in conventional sandstone and carbonate reservoirs significant advances have recently been achieved in unraveling the gaseous hydrocarbon generation and retention processes that occur within these complex systems in addition cutting edge characterization technologies have allowed precise documentation of the spatial variability in chemistry and structure of thermally mature organic rich shales at the submicrometer scale revealing the presence of geochemical heterogeneities within overmature gas shale samples and notably the presence of nanoporous pyrobitumen such research advances will un