pore characteristic analysis of a lacustrine shale a case study in the ordos basin nw china abstract organic shales deposited in a continental environment are well developed in the ordos basin nw china which is rich in hydrocarbons however previous research concerning shales has predominantly focused on marine shales and barely on continental shales in this study geochemical and mineralogical analyses high pressure mercury intrusion and low pressure adsorption were performed on 18 continental shale samples obtained from a currently active shale gas play the chang 7 member of yanchang formation in the ordos basin a comparison of all these techniques is provided for characterizing the complex pore structure of continental shales geochemical analysis reveals total organic carbon toc values ranging from 0 47 to 11 44 indicating that there is abundant organic matter om in the study area kerogen analysis shows vitrinite reflectance ro of 0 68 1 02 indicating that kerogen is at a mature oil generation stage x ray diffraction mineralogy xrd analysis indicates that the dominant mineral constituents of shale samples are clay minerals which mainly consist of illite chlorite kaolinite and negligible amounts of montmorillonite quartz and feldspar followed by low carbonate content all scale pore size analysis indicates that the pore size distribution psd of shale pores is mainly from 0 3 to 60 nm note that accuracy of all scale psd analysis decreases for pores less than 0 3 nm and more than 10 m experimental analysis indicates that mesopores 2 50 nm are dominant in continental shales followed by micropores

sensitivity of extratropical cyclone characteristics to horizontal resolution in the ecmwf model the sensitivity to horizontal resolution of northern hemisphere extratropical cyclone characteristics during the wintertime december march is investigated using a set of seasonal forecasts 1982 2001 with the european centre for medium range weather forecasts ecmwf model three different horizontal resolutions tl95 tl159 and tl255 are employed in order to test the realism of the simulations the model results are compared with those obtained from era 40 re analysis data the cyclone tracking is accomplished by applying an automatic tracking scheme to six hourly mean sea level pressure data it is shown that many of the key characteristics of extratropical cyclones in the ecmwf model are highly sensitive to horizontal resolution with the low resolution version tl95 for example simulating only about 60 of the re analysed total number of extratropical cyclones regions found to be particularly sensitive include the northern pacific the arctic baffin bay and the labrador sea as well as the mediterranean sea for the latter region it is shown that even the relatively high resolution version of the model tl255 significantly underestimates the number of cases of genoa cyclogenesis furthermore it is shown that in some regions such as the entrance regions of the major northern hemisphere storm tracks model deficits are insensitive to increases in horizontal resolution the same analysis has been repeated for the high resolution operational ecmwf analysis 2000 2004 truncated at different total wave numbers tl95 tl159 tl255 and tl511 in order to separate dynamical effects of differences in resolution from those due to pure spectral truncation it is found that the dynamical effect of changing horizontal resolution dominates over the truncation effect for intense cyclones whereas the truncation effect dominates for shallow cyclones copyright 2006 royal meteorological society

energetics of winter troughs entering south america abstract the energetics and behavior of midtropospheric troughs over the southern hemisphere and their relationship with south america surface cyclogenesis were studied during the winters of 1999 2003 all surface cyclogenesis situations over uruguay and adjacent areas associated with 500 hpa troughs were analyzed the atmospheric circulation associated with type b and type c cyclones form the basis for two composites composite b with 25 cases and composite c with 13 cases the results showed that the midtropospheric troughs were more intense in composite c than in composite b before the surface cyclogenesis and that the opposite occurred during the surface cyclogenesis the baroclinic conversion was dominant in both composites in composite b the ageostrophic flux convergence afc contributed positively to the intensification of the surface cyclone since it imported energy into the area before the cyclogenesis started but in composite c the afc served as a sink because it exported energy based

climatological characteristics of fronts in the western north pacific based on surface weather charts composite front climatology in the western north pacific is determined using a newly developed 1 0 gridded data set here we propose a research strategy for determining the spatiotemporal distribution of fronts using weather chart images published by the japan meteorological agency one of the major data providers in the region a preliminarily investigation of the internal data characteristics for the period of 2000 2010 is undertaken and the final 4 years of data are used for an analysis of front climatology to avoid the effect of any spurious trends this enables in depth analyses to be conducted which have not previously been possible in the region including the composites of cross sectional patterns for the thermal fields and precipitation near fronts front length seasonality and the significance of the thermal gradient near the fronts in addition to determining the frontal frequency and spatial distribution of frontal precipitation pixel wise analysis reveals that 56 of the local precipitation maximum is located on the warm side of a cold front caused by less tilted upward motion on the warm side with the intrusion of the upper level cold dry air into the warm side this new data set also enables a further analysis of the occluded fronts which are not correctly distinguished in the existing objective detection method

beyond cold and warm an objective classification for maritime midlatitude fronts this study introduces a detailed and objective classification for mid latitude maritime fronts the classification is based on a principal component analysis pca to determine the dominant patterns of variability between fronts here fronts are defined as three dimensional frontal volumes which are detected in the era interim data set for a large number of locations in the atlantic pacific and indian oceans during both winter and summer in addition to the well established distinction between warm and cold fronts the pca exposes several new dimensions of variability a front intensity b surface fluxes and c along front transports linked to the intensity of the associated conveyor belts these new dimensions of variability are regionally and seasonally robust and a lagged composite analysis demonstrates that each of the new front types evolves in a dynamically characteristic way further the new front types can be related to established ones like katafronts and anafronts the new front types are finally redefined based on simple parameter thresholds to simplify their application in future studies

specific surface area and pore size distribution in clays and shales one of the biggest challenges in estimating the elastic transport and storage properties of shales has been a lack of understanding of their complete pore structure the shale matrix is predominantly composed of micropores pores less than 2 nm diameter and mesopores pores with 2 50 nm diameter these small pores in the shale matrix are mainly associated with clay minerals and organic matter and comprehending the controls of these clays and organic matter on the pore size distribution is critical to understand the shale pore network historically mercury intrusion techniques are used for pore size analysis of conventional reservoirs however for unconventional shale reservoirs very high pressures 414 mpa 60 000 psi would be required for mercury to access the full pore structure which has potential pitfalls current instrumental limitations do not allow reliable measurement of significant portions of the total pore volume in shales nitrogen gas adsorption techniques can be used to characterize materials dominated by micro and mesopores 2 50 nm a limitation of this technique is that it fails to measure large pores diameter 200 nm we use a nitrogen gas adsorption technique to study the micro and mesopores in shales and clays and compare the results from conventional mercury porosimetry techniques our results on pure clay minerals and natural shales show that i they have a multiscale pore structure at different dimensions ii fine mesopores with a characteristic 3 nm pore size obtained with n2 gas adsorption are associated with an illite smectite group of clays but not with kaolinite iii compaction results in a decrease of pore volume and a reduction of pore size in the inter aggregate macropores of the illitesmectite clays while the fine intra tachoid mesopores are shielded from compaction iv for natural shales mineralogy controls the pore size distributions for shales and the presence of micropores and fine mesopores in natural shales can be correlated with the dominance of the illite smectite type of clays in the rock our assessment of incompressible 3 nm sized pores associated with illite smectite clays provides an important building block for their mineral modulus

why do baroclinic waves tilt poleward with height theoretical and modeling studies of nongeostrophic effects in baroclinic waves predict that baroclinic waves should tilt poleward with height with a larger tilt in total meridional wind than in geostrophic quantities regression analysis of ncep ncar reanalysis 6 hourly data demonstrates that observed baroclinic waves do indeed tilt poleward with height although the observed tilt is smaller than predicted by previous studies the meridional ageostrophic wind enhances the poleward tilt of meridional wind perturbations despite being smaller in amplitude than the meridional geostrophic wind by a factor of 5 an improved estimate of the structure of the meridional ageostrophic wind in baroclinic waves is calculated assuming force balance several important terms in this estimate have been left out of previous estimates of the meridional ageostrophic wind three terms in the improved estimate produce nearly all of the poleward tilt of the meridional wind 1 the advection of geostrophic zonal wind perturbations by the mean zonal wind 2 the convergence of the eddy momentum flux and 3 the effect of friction the poleward tilt with height of baroclinic waves explains why upper level storm tracks tend to occur poleward of near surface baroclinic regions and may play a role in the midwinter suppression of the pacific storm track

a global climatology of atmospheric fronts 1 atmospheric fronts in the lower troposphere often mark regions of significant weather and serve as an important conceptual tool that is frequently used and well understood by the public this study uses an objective method to identify fronts in the era 40 reanalysis and to compile a quantitative global climatology of their occurrence the climatology confirms the mid latitude storm tracks as the regions of highest front frequency and identifies slow moving frontal boundaries in the subtropics corresponding to major climate features such as the mei yu front the climatology also shows fronts to be common features of the south pacific convergence zone in the northern hemisphere fronts shift poleward in summer in the southern hemisphere this and other aspects of seasonal behavior are rather different

evaluating the information content of tomographic data application to mesoscale observations integrating tomography in the design of future experiments requires knowledge of the information content of this type of data the case of mesoscale observations is examined here the evaluation of the performances of tomography as the only data type available is done by simulating acoustic transmissions in a quasi geostrophic model during a period of 106 geophysical days a linear inversion is then applied to recover the stream function field the linear hypothesis is validated for that particular scale and type of oceanic perturbation as is the robustness to erroneous data the full three dimensional stream function fields are reconstructed information brought by tomography varies according to the mode the first baroclinic mode is well estimated the barotropic mode is partially estimated only one component of the current is felt and higher modes are not resolved the relative vorticity is assessed with horizontal resolution at the scale of the elementary cells defined by the tomographic array it is compared to direct triangular computations the original contribution of tomography is in the simultaneous time and space dimensions complementary to the classical point measurements

high spatial resolution in vertical slice ocean acoustic tomography most studies of ocean acoustic tomography have assumed that little horizontal information is available from the many acoustic multipath travel times observed in a single vertical plane slice between source and receiver moorings there is in fact significant small scale information present in such data sets we examine single vertical slice tomography in spectral terms and show that the acoustic measurements resemble a high pass filter which is more sensitive to small scales shorter than 100 km than to longer scales with the exception of the mean which is well measured the sensitivity extends to scales smaller than 10 km in theory although the level of the ocean energy spectrum is so low at these scales that even small data errors limit the measurement we use analytical calculations supplemented by numerical simulations with realistic data sets to show that accurate reconstructions of the high wave number features are possible out to the limits of the parameterization 9 2 km wavelength when the power spectrum of the ocean features is white or red the total measurement error is 1 ms and multiple receivers are used the ultimate limit of spatial resolution may be smaller still depending on array configuration measurement errors and the shape of the power spectrum

barnett shale gas production fort worth basin issues and discussion newark east barnett shale field fort worth basin texas is currently the most productive gas field in texas in terms of daily production and is growing at an annual rate of more than 10 however despite the fact that the barnett play has been studied intensely by very capable geologists and engineers from several companies over a period of many years there continues to be several misunderstandings concerning fundamental factors controlling the success of the barnett play of north texas barnett gas production is poorer in areas near faults and structural flexures anticlines and synclines fractures which are most abundant in these structural settings are detrimental to barnett production open natural fractures are rare in the barnett and have little or nothing to do with barnett productivity in areas where barnett shale is thermally mature with respect to gas generation it is slightly overpressured about 0 52 psi ft 11 76 kpa m limestone beds within the barnett formation are the product of debris flows that originated on a carbonate shelf to the north of the present basin center it appears that the barnett can be used as an exploration model for other basins especially analogous basins of the ouachita trend the history of the development of the barnett reservoir in north texas provides an excellent example of how persistence can lead to success in nonconventional gas plays

the importance of shale composition and pore structure upon gas storage potential of shale gas reservoirs abstract the effect of shale composition and fabric upon pore structure and ch 4 sorption is investigated for potential shale gas reservoirs in the western canadian sedimentary basin wcsb devonian mississippian d m and jurassic shales have complex heterogeneous pore volume distributions as identified by low pressure co 2 and n 2 sorption and high pressure hg porosimetry thermally mature d m shales 1 6 2 5 vro have dubinin radushkevich d r co 2 micropore volumes ranging between 0 3 and 1 2 cc 100 g and n 2 bet surface areas of 5 31 m 2 g jurassic shales which are invariably of lower thermal maturity ranging from 0 9 to 1 3 vro than d m shales have smaller d r co 2 micropore volumes and n 2 bet surface areas typically in the range of 0 23 0 63 cc 100 g co 2 and 1 9 m 2 g n 2 high pressure ch 4 isotherms on dried and moisture equilibrated shales show a general increase of gas sorption with total organic carbon toc content methane sorption in d m shales increases with increasing toc and micropore volume indicating that microporosity associated with the organic fraction is a primary control upon ch 4 sorption sorption capacities for jurassic shales however can be in part unrelated to micropore volume the large sorbed gas capacities of organic rich jurassic shales independent of surface area imply a portion of ch 4 is stored by solution in matrix bituminite solute ch 4 is not an important contributor to gas storage in d m shales structural transformation of d m organic matter has occurred during thermal diagenesis creating and or opening up microporosity onto which gas can sorb as such d m shales sorb more ch 4 per weight percent wt toc than jurassic shales inorganic material influences modal pore size total porosity and sorption characteristics of shales clay minerals are capable of sorbing gas to their internal structure the amount of which is dependent on clay type illite and montmorillonite have co 2 micropore volumes of 0 78 and 0 79 cc 100 g n 2 bet surface areas of 25 and 30 m 2 g and sorb 2 9 and 2 1 cc g of ch 4 respectively dry basis a reflection of microporosity between irregular surfaces of clay platelets and possibly related to the size of the clay crystals themselves mercury porosimetry analyses show that total porosities are larger in clay rich shales compared to silica rich shales due to open porosity associated with the aluminosilicate fraction clay rich sediments low si al ratios have unimodal pore size distributions

geochemical constraints on the origin and volume of gas in the new albany shale devonian mississippian eastern illinois basin this study involved analyses of kerogen petrography gas desorption geochemistry microporosity and mesoporosity of the new albany shale devonian mississippian in the eastern part of the illinois basin specifically detailed core analysis from two locations one in owen county indiana and one in pike county indiana has been conducted the gas content in the locations studied was primarily dependent on total organic carbon content and the micropore volume of the shales gas origin was assessed using stable isotope geochemistry measured and modeled vitrinite reflectance values were compared depth of burial and formation water salinity dictated different dominant origins of the gas in place in the two locations studied in detail the shallower owen county location 415 433 m 1362 1421 ft deep contained significant additions of microbial methane whereas the pike county location 832 860 m 2730 2822 ft deep was characterized exclusively by thermogenic gas despite differences in the gas origin the total gas in both locations was similar reaching up to 2 1 cm3 g 66 scf ton lower thermogenic gas content in the shallower location lower maturity and higher loss of gas related to uplift and leakage via relaxed fractures was compensated for by the additional generation of microbial methane which was stimulated by an influx of glacial melt water inducing brine dilution and microbial inoculation the characteristics of the shale of the maquoketa group ordovician in the pike county location are briefly discussed to provide a comparison to the new albany shale

a new perspective on southern hemisphere storm tracks abstract a detailed view of southern hemisphere storm tracks is obtained based on the application of filtered variance and modern feature tracking techniques to a wide range of 45 yr european centre for medium range weather forecasts ecmwf re analysis era 40 data it has been checked that the conclusions drawn in this study are valid even if data from only the satellite era are used the emphasis of the paper is on the winter season but results for the four seasons are also discussed both upper and lower tropospheric fields are used the tracking analysis focuses on systems that last longer than 2 days and are mobile move more than 1000 km many of the results support previous ideas about the storm tracks but some new insights are also obtained in the summer there is a rather circular strong deep high latitude storm track in winter the high latitude storm track is more asymmetric with a spiral from the atlantic and indian oceans in toward antarctica and a subtropical jet related lower latitu

storm tracks in the southern hemisphere abstract from 1979 to 1989 global european centre for medium range weather forecasts ecmwf analyses of many meteorological variables important in baroclinic storms have been bandpass filtered to highlight fluctuations on 2 to 8 day time scales in order to illuminate the relationships among the variables in baroclinic storm track regions because of the greater zonal symmetry in the southern hemisphere sh versus the northern hemisphere nh it is possible to examine these relationships over a zonal sector without being dominated by local effects associated with jet stream entrance and exit regions of the storm tracks the bandpassed variance of geopotential height is used to define the storm track and its meridional profile has a pronounced midlatitude maximum in the sh the locations of the jet stream and the variance maxima of meridional and zonal velocity components vorticity vertical motion specific humidity and temperature all bear a distinctive relationship to the storm track but the lat

inertia gravity waves revealed in radiosonde data at jang bogo station antarctica 74 37 s 164 13 e 2 potential sources and their relation to inertia gravity waves

an objective cyclone climatology for the southern hemisphere abstract an objective method is developed and used to derive a climatology of centers of cyclonic vorticity for the southern hemisphere based on twice daily european centre for medium range weather forecasts ecmwf 1000 hpa analyses during 1980 86 these centers were computed as local minima of geostrophic relative vorticity g extending previous studies based on pressure minima this use of g avoids a bias favoring slower and or deeper cyclones that occurs when pressure is used and includes a large number of additional mobile vorticity centers in the 45 55 s band that are missed where a local pressure minimum cannot be found an automated tracking algorithm similar to that of murray and simmonds is used to match predicted location pressure and g from previous track history with available centers large numbers of g centers were found south of 60 s and near the midlatitude continents as in previous studies these were a mixture of migratory centers and other fixed topographic features the maxi

tomographic maps of the ocean mesoscale part 1 pure acoustics abstract a field test of ocean acoustic tomography was conducted in 1981 for a two month period in a 300 km square at 26 n 70 w in the north atlantic just south of the mode region nine acoustic deep sea moorings with sea floor transponders for automated position keeping and with provisions for precise time keeping were set and recovered from the measured travel times between moorings various displays of the three dimensional field of sound speed closely related to temperature have been obtained by inversion procedures these procedures use historical ocean data as a reference but all information from the in situ surveys has been withheld the pure tomographic results were then compared to direct in situ observations the tomographically derived spatial mean profile compares favorably to an equivalent profile from the in situ observations both differ significantly from the historical average maps constructed at three day intervals for a two month period show a pattern of eddy structure in agre

development of organic porosity in the woodford shale with increasing thermal maturity abstract using a combination of focused ion beam milling and scanning electron microscopy we describe the evolution of secondary organic porosity in eight woodford shale late devonian early mississippian samples with mean random vitrinite reflectance values ranging from 0 51 ro to 6 36 ro organic porosity was observed to be absent in samples with vitrinite reflectance values of up to 0 90 ro with the first appearance of secondary pores starting with the 1 23 ro sample porosity in the organic matter was unexpectedly absent in a sample with a vitrinite reflectance of 2 00 ro however organic pores were again found in samples with higher thermal maturities porosity when present did not appear to be uniformly distributed among the organic matter that was within less than a micron of each other suggesting important differences in composition of the organic matter thin regions of organic matter were observed between grains raising the possibility that small amounts of the deposited organic matter were compacted between grains to form thin layers and or the structures are part of the secondary organic matter interpreted to be post oil bitumen which was left behind as a residue during oil migration through the shale some regions of porous organic matter appeared to be grain protected whereas others did not which indicates that these non protected porous organic regions may be stress supporting with porosity intact under in situ reservoir conditions these observations suggest that thermal maturity alone is insufficient to predict porosity development in organic shales and other factors such as organic matter composition complicate porosity development

heterogeneity of intergranular intraparticle and organic pores in longmaxi shale in sichuan basin south china evidence from sem digital images and fractal and multifractal geometries abstract previous studies have determined many types of pores in shale such as organic pores inorganic pores and microfractures in this study pores are classified as intergranular intraparticle and organic pores based on the location of their occurrence the heterogeneities of the three pore types and their effects on the occurrence of shale gas which is of utmost practical importance for shale gas exploration and development are discussed in this study the three types of pores are quantitatively characterized using fractal and multifractal methods the mean fractal dimension and mean width of the multifractal spectrum of these pores are found to be different i e 1 5985 and 1 665 for intraparticle pores 1 5869 and 1 475 for intergranular pores and 1 6 and 1 3725 for organic pores intraparticle pores have the highest heterogeneity intergranular pores have intermediate heterogeneity and organic pores have the lowest heterogeneity sem images show that organic pores have good connectivity homogeneous distribution and small range of aperture change but have the lowest heterogeneity even where pores are abundant thus they provide the largest shale gas occurrence space in contrast intergranular pores are less abundant have lower connectivity and have higher heterogeneity than organic pores thereby providing a relatively smaller shale gas occurrence space finally intraparticle pores are the least abundant and possess the poorest connectivity largest range of aperture change and highest heterogeneity of the three pore types thereby providing the smallest shale gas occurrence space we conclude that organic pores are crucial to the occurrence of shale gas and can provide a new index for the evaluation of shale gas exploration and development

acoustic tomography in the straits of florida variability of the florida current has been monitored via acoustic tomography a reciprocal tomography experiment was conducted in the eastern half of the florida straits during mid october and november 1983 a triangular array of transceivers with leg separations of approximately 45 km was deployed at 27 n the presence of a surface mixed layer in the region allowed for the ducted propagation of acoustic energy in the surface layer a deeper layer was sampled by an unresolved group of refracted bottom reflected ray arrivals incorporating the complete set of arrivals we are able to obtain depth dependent estimates of the temperature field current velocity and relative vorticity the oceanography of the region has been shown to be dominated by the lateral shifting of the surface and subsurface core of the florida current the influx of westward flowing water through the northwest providence channel at 26 n also appears as a large scale signal in the eastern florida straits low frequency fluctuations of temperature current velocity and vorticity occur at periods ranging from several days to nearly 2 weeks and are intimately related to meandering of the florida current system

breakthrough pressure and permeability in partially water saturated shales using methane carbon dioxide gas mixtures an experimental study of carboniferous shales from the eastern qaidam basin china as an important unconventional and alternative resource shale gas has attracted worldwide attention the breakthrough pressure is a major factor in the generation and migration of shale gas as well as in the evaluation of the caprock sealing capacity carboniferous shales are considered to have great potential for the exploitation of shale gas thus investigations of the breakthrough pressure and gas effective permeability are significant two shale samples taken from the carboniferous hurleg formation in the eastern qaidam basin china were chosen to conduct breakthrough experiments to investigate the effects of water saturation and co2 ch4 mixed mole fractions on the breakthrough pressure and gas effective permeability prior to the experiments various relevant parameters e g the porosity mineral composition and organic geochemistry the total organic content thermal maturity and kerogen type and microstructure of these samples were also measured the results of our breakthrough experiments show that the breakthrough pressure increases with the water saturation and decreases with the co2 mole fraction in the gas mixture the situation for the gas effective permeability is just the opposite pore size distribution measurements indicate that there are many nanoscale micropores that can easily be blocked by water molecules this results in the reduced connectivity of gas pathways thus the breakthrough pressure increases and the gas effective permeability decreases with increasing water saturation the breakthrough pressure decreases with the co2 mole fraction because the interfacial tension of the co2 water system is smaller than that of the ch4 water system the viscosity of the co2 ch4 mixture was found to increase with the co2 mole fraction by fitting a series of values under the same temperature and pressure conditions leading to an increase in the gas effective permeability furthermore co2 molecules are smaller than ch4 molecules making it easier for co2 to move across pathways after each breakthrough experiment the co2 mole fraction in the effluent was less than that in the injected gas and it increased over time until reaching the initial injected gas composition this is because the adsorption and solubility of co2 in water are greater than those of ch4 this study provides practical information for further investigations of shale gas migration and extraction and the sealing capacities of caprocks

diagnosis of frontal instabilities over the southern ocean the development of three fronts over the southern ocean is described using seawinds on quikscat scatterometer surface winds and an attribution technique to partition the wind field in three components nondivergent and irrotational components at the scale of the front and the remaining harmonic component or environmental flow induced by the synoptic scale flow the front and the environment in which the front is embedded are analyzed separately a frontal wave is shown to develop out of the first front when the large scale alongfront stretching decreases the environmental flow becomes frontolytic and a connection with the upper levels is established in the second case the stretching remains relatively strong and no frontal wave develops the third front exhibits a developing wave but is not in a favorable configuration with the upper levels the frontal wave does not deepen significantly

unconventional shale gas systems the mississippian barnett shale of north central texas as one model for thermogenic shale gas assessment shale gas resource plays can be distinguished by gas type and system characteristics the newark east gas field located in the fort worth basin texas is defined by thermogenic gas production from low porosity and low permeability barnett shale the barnett shale gas system a self contained source reservoir system has generated large amounts of gas in the key productive areas because of various characteristics and processes including 1 excellent original organic richness and generation potential 2 primary and secondary cracking of kerogen and retained oil respectively 3 retention of oil for cracking to gas by adsorption 4 porosity resulting from organic matter decomposition and 5 brittle mineralogical composition the calculated total gas in place gip based on estimated ultimate recovery that is based on production profiles and operator estimates is about 204 bcf section 5 78 10 9 m 3 1 73 10 4 m 3 we estimate that the barnett shale has a total generation potential of about 609 bbl of oil equivalent ac ft or the equivalent of 3657 mcf ac ft 84 0 m 3 m 3 assuming a thickness of 350 ft 107 m and only sufficient hydrogen for partial cracking of retained oil to gas a total generation potential of 820 bcf section is estimated of this potential approximately 60 was expelled and the balance was retained for secondary cracking of oil to gas if sufficient thermal maturity was reached gas storage capacity of the barnett shale at typical reservoir pressure volume and temperature conditions and 6 porosity shows a maximum storage capacity of 540 mcf ac ft or 159 scf ton

simulations of acoustic tomography array performance with untracked or drifting sources and receivers ocean tomography as originally proposed required all sources and recievers to be tautly moored and acoustically tracked to separate travel time perturbations due to mooring motion from those due to ocean features it is possible to process the tomographic travel times to estimate both ocean sound speed perturbations and mooring offsets effecting a separation without external tracking a side effect of this processing is a check on the ray identification since the varying instrument positions can be used as a synthetic array for estimating ray angle simulations and examples with actual data were used to contrast mapping performance with and without mooring tracking for a variety of ray data sets in general the ocean maps degrade when the tracking data are withheld however when many high precision ray travel time measurements are available the degradation is small in these cases it would be possible to deploy free drifting instruments as part of a monitoring experiment

the effect of water saturation on methane breakthrough pressure an experimental study on the carboniferous shales from the eastern qaidam basin china abstract breakthrough pressure plays an important role in shale gas flow mining and caprock evaluation a series of breakthrough experiments were conducted under different water saturation conditions for four shales taken from the carboniferous hoit taria formation in the eastern qaidam basin china to investigate the influence of water saturation on breakthrough pressure relevant geochemical tests mineral composition clay content total organic carbon thermal maturity and vitrinite reflectance and micro structural characteristics of micro pores were also conducted breakthrough pressures under at least five different water saturations from 0 to 100 were obtained and relationship between breakthrough pressure and water saturation was fitted for each sample we found that breakthrough pressure increases exponentially with water saturation the decrease in effective pore diameter caused by both the bound water films and the swelling of the clay minerals resulted in the increase in the breakthrough pressure after water saturation reached about 60 breakthrough pressure increased rapidly from connectivity reduction caused by the sealing off of smaller pores and partial water saturation of the macropores by analyzing the correlation between breakthrough pressure and pore structure characteristics breakthrough pressure is inversely related to porosity and is primarily affected by macropores because macropores consist of many microfractures with lengths up to dozens of micrometers they determine the porosity and then affect the connectivity of the rock correlation analysis between the mineral compositions and breakthrough pressure showed that toc content exhibits a positive correlation with breakthrough pressure but neither quartz content nor the clay mineral content exhibits a correlation by combining this information with field emission scanning electron microscope results we found that microfractures are easily created where the toc total organic carbon is concentrated and these microfractures substantially contribute to the number of macropores however dissolution pores in the quartz and clay minerals are rare therefore the correlation between toc content and breakthrough pressure primarily results from the microfractures this study provides practical information for further studies of shale gas migration as well as shale gas mining and caprock evaluation

effects of composition and pore structure on the reservoir gas capacity of carboniferous shale from qaidam basin china abstract shale adsorption and breakthrough pressure are important indicators of shale gas development and key factors in evaluating the reservoir capacities of shales in this study geochemical tests pore structure tests methane adsorption tests and breakthrough pressure tests were conducted on shales from the carboniferous hurleg formation in eastern qaidam basin the effects of the shale compositions and pore structures on the adsorption and breakthrough pressures were studied and the reservoir capacities of the shales were evaluated by analyzing the shale adsorptions and sealing effects the results indicate that the organic carbon content was only one of factors in affecting the adsorption capacity of the shale samples while the effect of the clay minerals was limited based on the positive correlation between the adsorption capacity and specific surface area of the shale the specific surface area of the micropores can be used as an indicator to determine the adsorption capacity of shale the micro fracturing of brittle minerals such as quartz create a primary path for shale gas breakthrough whereas the expansion of clay minerals with water greatly increases the breakthrough pressure in the shale samples methane adsorption tests showed that maximum methane adsorption for shale samples z045 and s039 was 0 107 and 0 09655 mmol g respectively the breakthrough pressure was 39 36 mpa for sample s039 maintained for 13 days throughout the experiment however no breakthrough was observed in sample z045 when subjected to an injected pressure of 40 mpa for 26 days this indicates that sample z045 corresponding to a depth of 846 24 m exhibited higher adsorption capacity and a better reservoir sealing effect than sample s039 498 4 m depth this study provides useful information for future studies of qaidam basin shale gas exploration and development and for evaluation of shale quality

characteristics of the southern hemisphere winter storm track with filtered and unfiltered data abstract the structure and evolution of the fluctuations in synoptic scales in the southern hemisphere sh during winter are discussed using six years of european centre for medium range weather forecasts analyses it is shown that patterns from unfiltered meridional wind series in the sh display all the features needed to represent the synoptic scale waves typical periods and wavelengths are similar to those observed in the northern hemisphere 4 days 4000 km although over the pacific ocean they can be as high as 7 8 days and 4700 km respectively as in the northern hemisphere tilts are not geographically fixed but change with the stage of the evolution of the wave the phase speed of the waves agrees with the low level winds in extensive areas of the middle latitudes and ranges from 12 m s 1 in the indian ocean to 6 m s 1 in the pacific ocean the estimated group velocities achieve maximum values of about 38 m s 1 also in the indian ocean and agree with the upper level maximum winds in accor

baroclinicity meridional temperature gradients and the southern semiannual oscillation abstract it has long been known that a strong half yearly oscillation exists in surface pressure at high southern latitudes there are two minima during the year the one occurring in october being more intense than that in march the semiannual oscillation sao has been related to the different surface types and inertia at 50 and 65 s these conspire to produce a semiannual wave in the meridional temperature gradient between those two latitudes the timing of the maxima for these is as above but the stronger is in march however if the arguments of van loon are applied literally then the seasonal evolution of temperature gradient should follow a comparable seasonal evolution of baroclinicity and surface pressure a full calculation of baroclinicity shows that the seasonal evolution of static stability combined with the twice annual maxima of meridional temperature gradient produces a larger peak of baroclinicity in october consistent with the sao in surface pressure

frontal wave cyclogenesis in the north atlantic a climatological characterisation the ambient conditions during cyclogenesis on fronts in the north atlantic na are characterised climatologically in the era interim dataset these secondary cyclones which grow from frontal waves are typically small in scale shallow and deepen rapidly and pose a challenge to forecasters and numerical weather prediction models frontal wave development has been studied intensively in the past based on observations e g fastex real case studies or analytical models in this study frontal wave cyclogenesis is studied from a climatological perspective and is detected by a combination of two automated identification methods for the period between 1979 and 2014 a climatology of frontal wave cyclogenesis is presented horizontal composites provide an estimate of the climatological mean of conditions during frontal wave cyclogenesis which may prove useful in the assessment of the realism of proposed idealized models of frontogenesis the findings are also compared with assumptions made in earlier idealized studies of frontal waves the composites reveal coherent structures of diabatically generated low level pv in the lower troposphere neutral moist static stability at cyclogenesis and an ambient lower troposphere close to saturation the vertical pv structure in the east na is more vertically aligned than in the west na and pv anomalies from the upper and lower levels reach deeper into the mid troposphere which indicates an enhanced phase lock between the two anomalies previous studies suggest the existence of an upper limit of along frontal stretching above which frontal wave development is strongly suppressed the presented multi decadal analysis confirms its existence in a range between 0 6 and 0 8 10 5 s 1 finally a climatology of along frontal stretching for the na is presented and compared to the fraction of cyclogenesis forming on frontal waves

water saturation driven evolution of helium permeability in carboniferous shale from qaidam basin china an experimental study abstract permeability is an important parameter for describing the transport properties of gas shales this study investigates the effects of water saturation on stress dependent permeability and the slip factor of carboniferous shales in the qaidam basin china to analyze correlations between water saturation effective stress helium permeability and slip factor helium permeability of 12 shale samples with different water saturation at pore pressures up to 6 89 mpa and effective stresses up to 27 58 mpa at 25 c is measured subsequently shale characteristics including mineral composition total organic carbon toc content thermal maturity vitrinite reflectance and pore structure distribution psd pore volume and type are determined the analyses reveal a consistent exponential relation between apparent effective gas permeability at 6 89 mpa and effective stress the apparent effective helium permeability at 4 13 mpa decreases exponentially with increasing water saturation particularly in shale samples with a high intrinsic permeability the critical water saturation value of shale is 30 40 two different modes of gas water two phase flow are observed when water saturation is 30 helium permeability decreases sharply and gas water flow in the shale samples appear as channel flow however when water saturation is 40 helium permeability slowly decreases gas water flow in the shale samples appear as funicular flow gas and water simultaneously flow in all capillaries and thin films of structured water on mineral surfaces reduce the pore throat diameter thus increased water films in narrow flow paths increase the gas slippage effect furthermore the slip factor initially decreased with increasing water saturation before increasing helium permeability exhibits a negative correlation with toc and clay contents and a positive correlation with quartz content the micropores and mesopores in samples with high clay content and toc are favorable to gas adsorption but not to gas transport permeability measurements of humidity oven dried samples reveal a power law relation between the gas slip factor and klinkenberg corrected permeability the slope of the resulting curve 0 29 is lower than that obtained for low permeability gas sands this study provides practical information for further studies of shale gas migration and the gas slippage effect in certain gas water flows

influence factors and an evaluation method about breakthrough pressure of carbonate rocks an experimental study on the ordovician of carbonate rock from the kalpin area tarim basin china abstract there are many oil and gas fields around the world that are sealed by tight carbonate caprocks compared with gypsum rocks and shales tight carbonate caprocks are characterized by brittleness and ease of structural fracturing and dissolving in acidic groundwater the breakthrough pressure bp is a significant indicator that indicates the sealing capacity of the caprocks therefore we conducted a series of experiments including effective porosity permeability casting thin sections bp mineral composition microstructural characteristics and clay minerals contents on carbonate samples from ordovician system in the kalpin area tarim basin china to research factors that affect the bp of carbonate caprocks according to the experimental data analysis the bp deceases with macropore proportions and increases with proportions of micropore and mesopore volume due to the large macropore proportion and low clay content

ocean acoustic tomography from ships mesoscale mapping of the ocean sound speed field in a 1000 1000 km area by means of ocean acoustic tomography is greatly enhanced by augmenting a few acoustic moorings with a movable ship based receiver computer simulations based on realistic noise levels in the measured acoustic travel times give 5 1 residual variance in c x y z for four six acoustic source moorings in an ocean perturbed in the gravest baroclinic mode for comparison objective mapping based on traditional vertical profiles requires 3 times the steaming distance to yield equivalent residual error detailed results depend on many parameters the assumed mesoscale spectrum and vertical mode structure the number of observed multipaths the mooring configuration the number of ship stations and the travel time signal level due to mesoscale eddies and noise level due to internal waves and position keeping errors these parameters have critical values below which there is distinct deterioration and beyond which there is little gain we believe that the critical values can be attained in practice so the ultimate limit on mesoscale mapping is imposed by the internal wave induced travel time error this assumes that position keeping of the submerged acoustic sources and receiver by a combination of satellite navigation and high frequency acoustics can be achieved with 10 m accuracy the present study assumes a stationary ocean a second paper will deal with reciprocal transmissions yielding currents and hence the barotropic mode this is required in a dynamic ocean model for estimating c x y z t all this is preparatory to a tomography experiment in the greenland sea in 1988 1989

a review of ocean acoustic tomography 1987 1990 the techniques and instruments used in acoustic tomography of the oceans are surveyed and results are summarized sections are devoted to theoretical studies and numerical simulations mesoscale mapping vertical slice tomography flow imaging and nonlinear bias series of tomographic experiments analyses to identify global changes and outstanding problems the forward and inverse problems and ocean physics typical data are presented in tables and graphs and a comprehensive bibliography is provided 72 refs

an objective study of 500 hpa moving troughs in the southern hemisphere abstract the location and movement of 500 hpa troughs using an automated method are studied with data from a 24 yr period with the objective of determining the trough formation and dissipation regions in the southern hemisphere to identify the 500 hpa mobile troughs an objective method that uses the eulerian centripetal acceleration eca is developed on average 868 troughs per year were identified by the method with an increase in trend during the period studied the troughs have an average lifetime of 4 3 days being longer shorter in subtropical high latitudes the average calculated phase velocity was 13 6 m s 1 being higher lower in middle high latitudes the troughs are normally found in the 60 40 s latitudinal band with maximum occurrence at 50 s the longitudinal distribution of trough genesis has three maximum regions over the drake strait and the south atlantic ocean over the indian ocean around 50 s and over the southwestern pacific ocean between 150 e and 150 w the trough d

basin scale tomography a new tool for studying weather and climate we present the first experimental results demonstrating the use of acoustic tomography to observe the large scale 500 km temperature fluctuations in ocean basins use of the tomographic technique as presented here will eventually lead to a better understanding of weather climate ocean circulation and the distributions of marine organisms from june to september 1987 tomographic signals were transmitted between four sources and nine receivers over a 3000 by 4000 km region the basin scale in the northeast pacific this paper discusses five issues related to transmissions across one 3000 km section first basin scale tomography is feasible because multipaths are stable in the presence of ocean fluctuations and the multipaths can be understood with ray theory and its extensions second the tomography problem can be initiated from climatological estimates it is unnecessary to initiate with conventional measurements during the experiment a prohibitively expensive proposition third a description of the tomographic reconstruction procedure kalman filtering is presented the filter imposes temporal and spatial constraints on the solution for the thermal field fourth the sensitivity of the estimated thermal field is examined with respect to variations of the constraints thermal maps are not very sensitive to variations of the constraints fifth tomography is used to observe significant changes from month to month in the large scale thermal field in the ocean including the seasonal thermocline where week to week resolution can be obtained in contrast available point measurements appear to be insufficient for observing monthly changes in the large scale thermal field in the ocean these acoustic measures of weather and climate in the ocean cannot be verified with other data e g satellites point measurements and thus provide an orthogonal perspective by which weather and climate may be observed and understood

theory of acoustic measurement of internal wave strength as a function of depth horizontal position and time high frequency 1 cpd variations in travel time of acoustic transmissions over ocean mesoscale distances are known to be dominated by the effects of internal wave displacements of the sound speed stratification flatte et al 1979 flatte 1983a variations in the difference in travel time between transmissions in opposite directions along the same path reciprocal transmissions are dominated by internal wave currents munk et al 1981 we investigate the usefulness of a two mooring acoustic system for determining the statistical variances of internal wave displacements and currents as a function of depth geographical position and time we find that statistical fluctuations in the internal wave field itself prevent recovery of range dependent information between the two moorings however range averaged information can be obtained about mean energy level and about vertical energy migration we find that uncertainties in the buoyancy and sound speed profiles do not significantly affect the usefulness of the method

elastic properties of seafloor sediments from the modelling of amplitudes of multiple water waves recorded on the seafloor off bear island north atlantic wide angle seismic data acquired by use of air guns and ocean bottom seismometers obs contain strong direct water arrivals and multiples generally considered as noise and thus not included in the modelling however a recent study showed that standard ray tracing modelling of the water multiples recorded off the bear island north atlantic provided a reliable estimate of the velocity distribution in the water layer here we demonstrate that including the amplitudes in the modelling provide valuable information about the vp contrast at the seafloor as well as the vp vs ratio and attenuation qp of the uppermost sediments the vp contrast at the seafloor is estimated at about 250 m s within a precision of approximately 30 m s the vp vs ratio in the uppermost sedimentary layer is modelled in the range 2 25 2 50 and the qp factor is estimated at 1000 for the water 30 50 for the uppermost layer and 40 50 for the second sedimentary layer the values obtained for the sediments suggest a lithology dominated by silty clays with porosity below average

geochemistry and origin of the giant quaternary shallow gas accumulations in the eastern qaidam basin nw china abstract this study provided an overview of the geological setting and geochemical characteristics of the pleistocene shallow gas accumulations in the eastern qaidam basin nw china the five largest gas accumulations discovered in this region have a combined enclosure area of about 87 km 2 and 7 9 trillion cubic feet tcf of proven gas reserves the dominance of methane mostly more than 99 9 and the 13 c and d values of methane 68 51 to 65 00 and 227 55 to 221 94 respectively suggest that these gases are biogenic derived from the degradation of sedimentary organic matter by methanogens under relatively low temperatures 15 tds and strong stratification the deposition and extensive lateral occurrence of lacustrine shoreline sands silts in beach sand sheets and sand bars provided excellent reservoirs for the biogenic gas generated from adjacent rocks effective but dynamic gas seals are provided by a combination of factors such as the intermittent vertical variation in the sediment lithologies hydraulic trapping due to the mudstone water saturation the hydrocarbon gradient created as the result of gas generation from potential caprocks and the presence of a regional caprock consisting of 400 800 m of muds and evaporites it appears that the most favorable traps for large gas accumulations occur on structural slopes near the major gas kitchen and the prolific gas pools are often those large gentle anticlines with little faulting complication

acoustic tomography in the florida strait temperature current and vorticity measurements various aspects of near bottom ocean variability including the alongshore temperature and current the cross slope temperature the onshore offshore flow and the area averaged relative vorticity on the western slope of the florida strait near 27 n have been measured with a three point acoustic reciprocal transmission three pairs of reciprocal travel time data were extracted from acoustic pulse responses of a 1983 august triangular transmission experiment temperatures and currents were estimated from the sum and difference respectively of reciprocal travel times and an area averaged vorticity was estimated from circulation following stokes theorem the estimations agree well with the concurrent direct measurements at two nearby moorings low frequency fluctuations of temperatures currents and vorticity show a strong weekly period clearly and consistently describing a near bottom onshore offshore water movement on the western slope in association with the gulf stream meanders

the methane sorption capacity of paleozoic shales from the sichuan basin china the methane sorption capacities of paleozoic shales from the sichuan basin were investigated the primary results show they have sorption capacities ranging between 0 94 and 4 29 cm3 grock at stp comparable to the sorption capacity 1 27 2 41 cm3 grock at stp of barnett shale however the sorption isotherms indicate that most of the sichuan basin shales would reach their approximate sorption equilibrium at 3 4 mpa in contrast to the continuously upward trend of north american shales a general positive relationship between toc content and methane sorption capacity indicates that toc content is the major controlling factor for the methane sorption of the sichuan shales a negative relationship between the clay mineral content and the sorption capacity of these shales may suggest that clay minerals play an insignificant role in the methane sorption of these paleozoic shales sorption capacities and variation ranges are generally ordered as to geological age viz cambrian silurian permian

results from the 1984 marginal ice zone experiment preliminary tomography transmissions implications for marginal ice zone arctic and surface wave tomography during the 1984 marginal ice zone experiment mizex 84 a 224 hz center frequency acoustic tomography sound source was deployed off spitsbergen norway in 1200 m of water over the course of 10 days it transmitted hourly signals that were recorded by receivers at two locations one moving with the ice pack and the other stationary the main purpose of the transmissions was to answer the following questions which are important to the feasibility of acoustic tomography in marginal ice zone miz and arctic regions 1 can the signals be coherently averaged to improve the signal to noise ratio of the multipath arrival peaks 2 are the surface scattering and bottom reflection losses acceptably low 3 are the arrivals identifiable 4 are the arrivals stable and 5 are the arrivals resolvable our data analysis provides generally positive answers indicating that ocean acoustic tomography is feasible in miz regions however the shallow bathymetry in the mizex 84 area increases the difficulty of the problem consistent with the observations of palmer et al 1985 and deferrari and nguyen 1985 in the shallow water of the straits of florida in analyzing the data it was noticed that the phase or travel time fluctuation spectra of surface interacting rays exhibited a shape similar to that of the surface wave frequency spectrum this suggested that tomography could also measure the surface wave field a previously unexplored possibility theoretical expressions are derived in this paper which relate the acoustic fluctuations to standard surface wave descriptors e g the frequency directional spectrum these expressions are then used to compute the surface wave frequency spectra for 2 days of data though these spectra are uncorroborated by other wave spectrum measurements e g wave rider buoys the rms wave heights predicted by the acoustics agree well with rms wave heights estimated by wind force data

extratropical fronts in the lower troposphere global perspectives obtained from two automated methods in this study two commonly used automated methods to detect atmospheric fronts in the lower troposphere are compared in various synoptic situations the first method is a thermal approach relying on the gradient of equivalent potential temperature th while the second method is based on temporal changes in the 10 m wind wnd for a comprehensive objective comparison of the outputs of these methods of frontal identification both schemes are firstly applied to an idealised strong baroclinic wave simulation in the absence of topography then two case studies one in the northern hemisphere nh and one in the southern hemisphere sh were conducted to contrast fronts detected by the methods finally we obtain global winter and summer frontal occurrence climatologies derived from era interim for 1979 2012 and compare the structure of these th is able to identify cold and warm fronts in strong baroclinic cases that are in good agreement with manual analyses wnd is particularly suited for the detection of strongly elongated meridionally oriented moving fronts but has very limited ability to identify zonally oriented warm fronts we note that the areas of the main th frontal activity are shifted equatorwards compared to the wnd patterns and are located upstream of regions of main wnd front activity the number of wnd fronts in the nh shows more interseasonal variations than th fronts decreasing by more than 50 from winter to summer in the sh there is a weaker seasonal variation of the number of observed wnd fronts however th front activity reduces from summer djf to winter jja the main motivation is to give an overview of the performance of these methods such that researchers can choose the appropriate one for their particular interest

pore structure characterization for the longmaxi and niutitang shales in the upper yangtze platform south china evidence from focused ion beam he ion microscopy nano computerized tomography and gas adsorption analysis abstract pore structure is of great importance in the occurrence of shale gas in this study pores in shale samples from the lower silurian longmaxi and lower cambrian niutitang shales in chongqing in the upper yangtze platform south china were examined using focused ion beam he ion microscopy fib him nano computerized tomography nano ct and gas adsorption analysis the results show that most pores in measured samples of the niutitang shale are mineral matrix pores and have poor connectivity including both intraparticle and interparticle pores organic matter pores in measured samples of the niutitang shale are rare and have small diameters in measured samples of the longmaxi shale om pores mostly macropores and large mesopores are the most abundant the nano ct results revealed that the abundance of om pores led to good pore connectivity in the longmaxi shale samples whereas the prevalence of mineral matrix pores resulted in poor connectivity in the niutitang shale samples n2 and co2 adsorption analyses showed that the mean value of micropore mesopore volumes in the niutitang and longmaxi shales samples are 0 0332 ml g and 0 0261 ml g respectively the mean values of micropores mesopores surface area in the niutitang and longmaxi shales samples are 33 84 m2 g and 32 46 m2 g respectively thus there is little difference between measured samples of the longmaxi and niutitang shales in terms of volume and surface area of micropores mesopores the equal vitrinite reflectance equal ro values of measured samples of the longmaxi shale are lower than those of the niutitang shale samples over maturity equal ro 3 resulted in a reduction of the number of pores in organic matter small pore size and poor connectivity in measured samples of the niutitang shale relatively low maturity 2

southern hemisphere winter extratropical cyclone characteristics and vertical organization observed with the era 40 data in 1979 2001 abstract the mean characteristics and trends of southern hemisphere sh winter extratropical cyclones occurring at six levels of the troposphere over the period 1979 2001 have been investigated using the 40 yr ecmwf re analysis era 40 data cyclonic systems were identified with the melbourne university cyclone finding and tracking scheme this study shows that mean sea level pressure mslp cyclones are more numerous more intense smaller deeper and slower moving than higher level cyclones the novel vertical tracing scheme devised for this research revealed that about 52 of sh winter mslp cyclones have a vertically well organized structure extending through to the 500 hpa level about 80 of these vertically coherent sh cyclones keep their westward tilt until the surface cyclones reach their maximum depths and the mean distance is 300 km between the surface and the 500 hpa level cyclone centers when the surface cyclones obtain their maturity according to the authors definition of vertical orga

the organic matter distribution and methane capacity of the lower cretaceous strata of northeastern british columbia canada abstract the methane sorption capacity of a succession of sandstone siltstone shale and coal from the lower cretaceous fort st john group of northeastern british columbia was investigated average organic matter om content for all formations is 2 3 wt with a minimum of 0 6 wt and maximum of 10 1 wt the methane sorption capacity ranges between 0 19 and 2 74 cm3 g at 6 mpa and at 30 c total gas capacity free and sorbed gas ranges between 2 2 and 16 6 cm3 g at 6 mpa micropore volumes range between 0 43 and 1 69 cm3 100 g a positive correlation exists between the om content micropore volume and the methane capacity of shales shales with high methane capacities have either high contents of inertodetrinite or vitrinite moisture content shows a positive relationship with om content micropore volume and methane capacity the negative relationship between moisture and surface area derived from n2 adsorption suggests the moisture is located within the microporosity of the om and also explains the positive relationship between methane capacity and moisture the high inertodetrinite and vitrinite contents correlate with sea level regressions that delivered terrestrial om from coastal plains located south of the study area into the basin

geochemical evolution of organic rich shales with increasing maturity a stxm and tem study of the posidonia shale lower toarcian northern germany hydrocarbon generation and retention processes occurring within gas shales as a response to increases in thermal maturation are still poorly constrained while efforts have been directed at unravelling the resource potential composition and textures of these economically important unconventional systems their spatial variability in chemistry and structure is still poorly documented at the sub micrometer scale here we have characterized samples of the lower toarcian posidonia shale samples from northern germany at varying stages of thermal maturation using a combination of compositional organic geochemistry and spectromicroscopy techniques including synchrotron based scanning transmission x ray microscopy stxm we document geochemical and mineralogical heterogeneities down to the nanometer scale within the investigated samples as a function of their level of thermal maturity in particular authigenic albite crystals containing nanometric halite inclusions have been documented within the investigated mature and overmature samples the presence of such tracers of palaeobrine carbonate interactions supports a maturation scenario for the lower toarcian posidonia shale intimately related to ascending brine fluids rather than a maturation scenario solely resulting from high heat flows in addition various types of asphaltene and nso rich bitumen have been detected within the same samples very likely genetically derived from thermally degraded organic precursors furthermore the formation of nanoporous pyrobitumen has been inferred for samples of gas window maturity likely resulting from the formation of gaseous hydrocarbons by providing in situ insights into the fate of bitumen and pyrobitumen as a response to the thermal evolution of the macromolecular structure of kerogen the results reported here constitute an important step towards better constraining hydrocarbon generation processes during natural shale gas maturation

tomographic resolution of mesoscale eddies in the marginal ice zone a preliminary study the adequacy of ocean acoustic tomography to resolve mesoscale eddies in the marginal ice zones miz in the vertical plane containing the acoustic multipaths connecting a pair of transceivers is studied using simulation inversions based on realistic eddy profiles obtained from conductivity temperature depth data resolution in this plane is seen to be strongly dependent upon the characteristics of the sound channel for optimal minimum mean square error estimators resolution is directly related to accuracy with better resolution implying higher accuracy for unaided acoustic tomography i e no supplementary measurements using only non bottom interacting paths horizontal and vertical resolution lengths of the order of 40 km and 200 m respectively are found in the upper water column for a transmission range of 150 km the implication is that the horizontal resolution is marginally adequate to resolve miz eddies but the vertical resolution is not since the horizontal scale of the eddies is of the same order whereas the vertical scale is much shorter the incorporation of bottom reflected arrivals is found to improve resolution significantly however the improvement only occurs in the horizontal direction and saturates when more than 14 of these arrivals are included beyond this point additional travel time observations give mostly redundant information on the other hand the disappearance of less stable non bottom interacting ray paths can result in a significant loss of resolution but only vertically the deficiency in vertical resolution is a result of the upward refracting nature of the miz sound channel it is also demonstrated that the inclusion of point temperature measurements on the acoustic transceiver moorings can dramatically increase the vertical resolution of the overall system particularly within a horizontal correlation length of the mooring with the inclusion of satellite radiometry surface temperature measurements adequate vertical resolution is achieved over the entire range considered

travel time tomography in shallow water experimental demonstration at an ultrasonic scale acoustic tomography in a shallow ultrasonic waveguide is demonstrated at the laboratory scale between two source receiver arrays at a 1 1 000 scale the waveguide represents a 1 1 km long 52 m deep ocean acoustic channel in the kilohertz frequency range two coplanar arrays record the transfer matrix in the time domain of the waveguide between each pair of source receiver transducers a time domain double beamforming algorithm is simultaneously performed on the source and receiver arrays that projects the multi reflected acoustic echoes into an equivalent set of eigenrays which are characterized by their travel times and their launch and arrival angles travel time differences are measured for each eigenray every 0 1 s when a thermal plume is generated at a given location in the waveguide travel time tomography inversion is then performed using two forward models based either on ray theory or on the diffraction based sensitivity kernel the spatially resolved range and depth inversion data confirm th

observed winter cyclone tracks in the northern hemisphere in re analysed ecmwf data the observed cyclone activity in the northern hemisphere winter djf is investigated in 1979 97 european centre for medium range weather forecasts re analyses the cyclone trajectories are determined automatically by a next neighbour search of minima identified in the 1000 hpa geopotential height field z1000 these are compared with the traditional storm track defined by the root mean square of the band pass filtered 500 hpa geopotential height anomaly the analysis covers the north atlantic and north pacific basins the trend of the cyclone density distribution is similar to that of the storm track in the north atlantic but opposite in the north pacific in the atlantic the total number of cyclones with low central z1000 increases due to the northward shift towards lower regional climatological pressure whereas the number of cyclones with large gradients decreases in the pacific the number of intense weak cyclones with large low gradients increases decreases the cyclone track variability is investigated by a cluster analysts of the relative cyclone trajectories the three centroids corresponding to north eastward and zonally propagating cyclones and nearly stationary ones are very similar in both ocean basins the winter mean cluster occupation numbers of the two propagating cyclone clusters are positively correlated with one another in the atlantic and negatively in the pacific the three atlantic cyclone clusters can be linked to particular aspects of the central european climate the cyclonic activity can be related to teleconnection patterns which are dominant during northern hemisphere winter during high north atlantic oscillation index winters deeper icelandic lows the atlantic cyclone density shifts northward and is associated with more stationary cyclones during el nino warm event winters the pacific cyclone density is shifted northward and their propagation is oriented more zonally as in high pacific north american index phases deeper aleutian lows in the north atlantic propagating cyclones occur less and stationary ones more frequently in el nino winters the correlations between the north east ward propagating cyclones in the pacific and the north eastward and zonally propagating ones in the atlantic suggest an interaction between the two storm tracks

identification and climatology of southern hemisphere mobile fronts in a modern reanalysis abstractpresented here is an objective approach to identify characterize and track southern hemisphere mobile fronts in hemispheric analyses of relatively modest resolution such as reanalyses among the principles in its design were that it should be based on broadscale synoptic considerations and be as simple and easily understood as possible the resulting eulerian scheme has been applied to the european centre for medium range weather forecasts ecmwf re analysis era interim and a climatology of frontal characteristics at both the 10 m and 850 hpa levels derived for the period 1 january 1989 28 february 2009 the knowledge of the character of these features is central to understanding weather and climate over the hemisphere in both summer and winter the latitude belt 40 60 s hosts the highest frequency of frontal points but there are significant zonal asymmetries within this band the climatology reveals that the longest fronts are in the indian ocean where mean lengths exceed 2000 km the me

mississippian barnett shale fort worth basin north central texas gas shale play with multi trillion cubic foot potential the mississippian barnett shale serves as source seal and reservoir to a world class unconventional natural gas accumulation in the fort worth basin of north central texas the formation is a lithologically complex interval of low permeability that requires artificial stimulation to produce at present production is mainly confined to a limited portion of the northern basin where the barnett shale is relatively thick 300 ft 92 m organic rich presentday total organic carbon 3 0 thermally mature vitrinite reflectance 1 1 and enclosed by dense limestone units able to contain induced fractures the most actively drilled area is newark east field currently the largest gas field in texas newark east is 400 mi 2 1036 km 2 in extent with more than 2340 producing wells and about 2 7 tcf of booked gas reserves cumulative gas production from barnett shale wells through 2003 was about 0 8 tcf wells in newark east field typically produce from depths of 7500 ft 2285 m at rates ranging from 0 5 to more than 4 mmcf day estimated ultimate recoveries per well range from 0 75 to as high as 7 0 bcf efforts to extend the current barnett play beyond the field limits have encountered several challenges including westward and northward increases in oil saturation and the absence of lithologic barriers to induced fracture growth patterns of oil and gas occurrence in the barnett in conjunction with maturation and burial history data indicate a complex multiphased thermal evolution with episodic expulsion of hydrocarbons and secondary cracking of primary oils to gas

the wintertime southern hemisphere split jet structure variability and evolution a persistent feature of the southern hemisphere upper level time mean flow is the presence of a split jet across the south pacific east of australia during the austral winter the split jet is composed of the subtropical jet stj on its equatorward branch and the polar front jet pfj on its poleward branch the ncep ncar reanalysis is used to investigate the structure and evolution of the split jet results show that the presence absence of the pfj determines the degree of split flow given that the stj is a quasi steady feature a splitflow index sfi is developed to quantify the variability of the split jet in which negative values represent strong split flow and positive values nonsplit flow correlations with teleconnection indices are investigated with the sfi positively correlated to the southern oscillation index and negatively correlated to the antarctic oscillation the sfi is used to construct composites of heights temperature and wind for split flow and non split flow days the composites reveal that relatively cold conditions occur in the south pacific in association with nonsplit flow regimes and split flow regimes occur when relatively warm conditions prevail in the latter situation cold air bottled up over antarctica helps to augment the background tropospheric thickness gradient between antarctica and the lower latitudes with a resulting increase in the thermal wind and the pfj it is surmised that frequent cold surges out of antarctica moving into the south pacific are associated with non split flow regimes in this context the variability of the split jet responds to large scale baroclinic processes and is further modulated by synoptic scale disturbances

the diurnal evolution of cold fronts in the australian subtropics the effect of the diurnal cycle on the evolution of cold fronts in the australian subtropics is investigated in two high resolution numerical simulations the simulations are made using the pennsylvania state university national center for atmospheric research mesoscale model mm5 with the initial and boundary conditions taken from the operational analyses of the european centre for medium range weather forecasts these simulations are compared with the observations of two cold fronts taken during the central australian fronts experiment in 1991 the simulations show a number of features that have been suspected but never confirmed or quantified i although the wind field in the boundary layer is frontogenetic daytime turbulent mixing is strongly frontolytic which accounts for the weakening and deceleration of the fronts during the late morning and afternoon when convective mixing in the boundary layer is most vigorous ii when the mixing subsides in the early evening the low level winds increase along with the deformation and convergence leading to a strengthening and acceleration of the fronts iii bore like disturbances are generated during the early hours of the morning as the nocturnal inversion strengthens these bores propagate ahead of the front developing a series of large amplitude waves at their leading edge copyright c 2009 royal meteorological society

measuring the kuroshio current with ocean acoustic tomography ocean current profiling using ocean acoustic tomography oat was conducted in the kuroshio current southeast of taiwan from august 20 to september 15 2009 sound pulses were transmitted reciprocally between two acoustic stations placed near the underwater sound channel axis and separated by 48 km based on the result of ray simulation the received signals are divided into multiple ray groups because it is difficult to resolve the ray arrivals for individual rays the average differential travel times from these ray groups are used to reconstruct the vertical profiles of currents the currents are estimated with respect to the deepest water layer via two methods an explicit solution and an inversion with regularization the strong currents were confined to the upper 200 m and rapidly weakened toward 500 m in depth both methods give similar results and are consistent with shipboard acoustic doppler current profiler results in the upper 150 m the observed temporal variation demonstrates a similar trend to the prediction from the hybrid coordinate ocean model

midlatitude fronts and variability in the southern hemisphere tropical width abstractthis study examines the relationship between midlatitude synoptic activity and variations in the width of the tropics in the southern hemisphere for the period 1979 2016 the edge of the tr

a proposed method of surface map analysis present surface frontal analyses suffer from the defect that frontal positions are typically not collocated with zones of intense temperature contrast further individuals typically do not agree as to the existence type and location of fronts the author argues that the lack of a surface temperature analysis is mainly responsible for these flaws and it is proposed that such analysis preferably of potential temperature in regions of variable terrain elevation become part of routine procedure such an analysis will reveal nonfrontal baroclinic zones of considerable intensity most cold fronts except the strongest ones are denoted as baroclinic troughs propagating eastward in the prevailing westerly flow it is argued that when a meridional cold front exists in the presence of even a small meridional temperature gradient the wind shift should propagate away from the intense surface temperature gradient which then weakens an explanation is provided based on quasigeostrophic theory it follows that fronts are short lived phenomena

thermal evolution of the greenland sea gyre in 1988 1989 slice inverses of temperature and heat content from the 1988 1989 greenland sea tomography experiment and other observations including standard conductivity temperature depth stations moored thermistors surface meteorological variables and surface ice cover are combined to better understand the thermodynamics of the greenland sea gyre thermal evolution of the gyre center seems to divide naturally into the following three periods a preconditioning phase november january during which surface salinity is increased by brine rejection from ice formation and by entrainment but in which the mixed layer deepens only slowly to a depth of some 150 200 m a deep mixing phase february march during which the surface mixed layer deepens rapidly to approximately 1500 m in the gyre center purely under the influence of local surface cooling and a restratification phase during which the products of deep mixing are replaced by arctic intermediate water flowing in from the gyre edges the onset of the deep mixing phase occurs after ice formation in the gyre center stops resulting in an area of open water where large heat fluxes can occur in surrounding regions including the odden region to the south ice is still being formed to the north and west closer to the steep topography of the continental shelf the inverse results show significant variability due to advection and large temperature and heat content fluctuations with a period of about 50 days are seen

the effect of moisture on the methane adsorption capacity of shales a study case in the eastern qaidam basin in china this study investigated the effects of moisture on high pressure methane adsorption in carboniferous shales from the qaidam basin china the shale characteristics including the organic inorganic compositions and pore structure volume and surface distribution were obtained using various techniques gibbs adsorption measurements were performed over a pressure range up to 6 mpa and temperatures of 308 15 k on dry samples and moisture equilibrated samples to analyze the correlations between organic inorganic matter pore structure and moisture content on the methane sorption capacity compared to dry samples the sorption capacity of wet samples 0 44 2 52 of water content is reduced from 19 7 5 3 to 36 1 6 1 langmuir fitting is conducted to investigate moisture dependent variations of adsorbed methane density langmuir pressure and volume by combining the pore volume and surface distribution analyses our observations suggested that the main competition sites for ch4 h2o covered pores of approximately 2 7 nm whereas the effective sites for methane and water were predominantly distributed within smaller 10 nm respectively regarding the compositional correlations the impact of moisture on the amount of adsorbed methane shows a roughly linearly decreasing trend with increasing toc content ranging from 0 62 to 2 88 whereas the correlation between the moisture effect and various inorganic components is more complicated further fitting results indicate that illite smectite mixed formations are closely related to the methane capacity whereas the illite content show an evident connection to the pore structural volume and surface variations in the presence of moisture

pore types in the barnett and woodford gas shales contribution to understanding gas storage and migration pathways in fine grained rocks the identification of organoporosity microscale and nanoscale pores within organic matter in shales its importance to storage and perhaps transfer of gas molecules through shales and methods for gathering three dimensional images of the pores such as by argon ion milling and or field emission scanning electron microscopy have all been well documented and discussed for unconventional gas shales however other types of pores exist within shales that can be important to storage and migration of gas and oil and other technologies are available for their identification and imaging the different pore types found in the barnett and woodford shales are described and classified in this article scanning electron microscopy revealed the presence of porous floccules in both the barnett and woodford shales which appear similar to laboratory produced floccules and to those in other ancient shales published experimental and observational studies indicate that floccules are hydraulically equivalent to coarser grains and are transported by traction processes current induced microsedimentary structures and textures within the barnett and woodford shales as well as the preserved floccules suggest such processes were active during transport and deposition pore spaces between the floccules are open and can provide storage space as well as permeability pathways for gas molecules through the shales pores are also found within organic matter that occurs both as discrete particles and as adsorbed coatings around clay grains in the shale they are referred to here as organopores porous fecal pellets are also common in the barnett shale preserved fossil fragments such as organic walled spores and inorganic sponge spicules have hollow central chambers which may remain partially or completely open even after burial intraparticle pores occur between grains of various minerals e g pyrite framboids microchannels within shale matrix which may be the bounding surfaces of scours or microsedimentary structures may also provide permeability pathways for hydrocarbon migration mircrofractures are also common and their initiation might be related to mineral crystal structure when present in sufficient quantity these pore types offer potential gas and oil molecule storage spaces and permeability pathways through the shales

effect of the andes cordillera on precipitation from a midlatitude cold front the effects of the andes cordillera the major mountain range in south america on precipitation patterns of baroclinic systems approaching from the southeast pacific remain largely unstudied this study focuses on a case in late may 2008 when an upper level trough and surface cold front produced widespread precipitation in central chile the primary goal was to analyze the physical mechanisms responsible for the structure and evolution of the precipitation weather research and forecasting wrf model simulations indicate that as an upper level trough approached central chile midtropospheric flow below 700 hpa was blocked by the high topography and deflected poleward in the form of a barrier jet this northerly jet had wind maxima in excess of 15 m s 21 was centered around 925 hpa and extended westward 200 km from the mountains it intersected the cold front which approached from the south near the coast thereby increasing convergence along the frontal surface slowing its equatorward progress and enhancing rainfall over central chile another separate region of heavy precipitation formed over the upwind slopes of the cordillera a trajectory analysis confirmed that the barrier jet moved low level parcels from their origin in the moist southeast pacific boundary layer to the coast when model topography was reduced to twenty percent of its original height the cold front advanced more rapidly to the northeast generated less precipitation in central chile between 338 and 368s and produced minimal orographic precipitation on the upwind andean slopes based on these findings the high topography appears responsible for not only orographic precipitation but also for substantially increasing precipitation totals over the central coast and valley

observations of sound speed fluctuations in the western philippine sea in the spring of 2009 as an aid to understanding long range acoustic propagation in the philippine sea statistical and phenomenological descriptions of sound speed variations were developed two moorings of oceanographic sensors located in the western philippine sea in the spring of 2009 were used to track constant potential density surfaces isopycnals and constant potential temperature surfaces isotherms in the depth range 120 2000 m the vertical displacements of these surfaces are used to estimate sound speed fluctuations from internal waves while temperature salinity variability along isopycnals are used to estimate sound speed fluctuations from intrusive structure often termed spice frequency spectra and vertical covariance functions are used to describe the space time scales of the displacements and spiciness internal wave contributions from diurnal and semi diurnal internal tides and the diffuse internal wave field related to the garrett munk gm spectrum are found to dominate the sound speed variability spi

global climatologies of fronts airmass boundaries and airstream boundaries why the definition of front matters abstractclimatologies of fronts airmass boundaries and airstream boundaries can be calculated using automated approaches on gridded data such approaches may require choices to define a front in

ocean acoustic tomography at 1000 km range using wavefronts measured with a large aperture vertical array broadband acoustic signals transmitted from a moored 250 hz source to a 3 km long vertical line array of hydrophones 1000 km distant in the north central pacific ocean were used to determine the amount of information available from tomographic techniques used in the vertical plane connecting a source receiver pair a range independent pure acoustic inverse to obtain the sound speed field using travel time data from the array is shown to be possible by iterating from climatological data without using any information from concurrent environmental measurements range dependent inversions indicate resolution of components of oceanic variability with horizontal wavelengths shorter than 50 km although the limited spatial resolution of concurrent direct measurements does not provide a strong cross validation since the typical cast spacing of 20 25 km gives a nyquist wavelength of 40 50 km the small travel time signals associated with high wavenumber ocean variability place stringent but achievable requirements on travel time measurement precision the forward problem for the high wavenumber components of the model is found to be subject to relatively large linearization errors however unless the sound speed field at wavelengths greater than about 50 km is known from other measurements or from a two dimensional tomographic array the high ocean wavenumber resolution that is in principle available from tomographic measurements is therefore achievable only under restricted conditions

a cyclone phase space derived from thermal wind and thermal asymmetry abstract an objectively defined three dimensional cyclone phase space is proposed and explored cyclone phase is described using the parameters of storm motion relative thickness asymmetry symmetric nonfrontal versus asymmetric frontal and vertical derivative of horizontal height gradient cold versus warm core structure via the thermal wind relationship a cyclone s life cycle can be analyzed within this phase space providing substantial insight into the cyclone structural evolution an objective classification of cyclone phase is possible unifying the basic structural description of tropical extratropical and hybrid cyclones into a continuum stereotypical symmetric warm core tropical cyclone and asymmetric cold core extratropical cyclone life cycles are illustrated using 1 navy operational global atmospheric prediction system nogaps operational analyses and 2 5 ncep ncar reanalyses the transitions between cyclone phases are clearly illustrated within the phase space including extratro

geochemical characteristics of oil and source rocks and implications for petroleum systems talara basin northwest peru in the first comprehensive study of the talara basin petroleum system of onshore and offshore northwest peru we test oil source rock correlation through molecular biomarker analysis of oil samples from wells scattered throughout the basin as well as purported source rocks the new data presented in this manuscript suggest that the oils constitute one oil family and that the source rock was a predominant marine clay deposited in an oxic to suboxic environment substantial relative amounts of oleanane in each oil sample indicate a notable input of terrestrial organic matter deposited in a mixed marine and terrestrial environment probably deltaic the high ratio of 24 norcholestanes to 27 norcholestanes and c25 highly branched isoprenoid hbi alkanes suggests a significant upwelling component in the source rock depositional environment in addition the high oleanane indices oleanane hopane of the oils are not paralleled in any alternative source rock candidate in this study the values are as expected for tertiary source rocks and are at levels that exceed any reported cretaceous or older source rock or oil this result in concert with high nordiacholestane ratios norcholestane ratios and hbi concentrations indicates a tertiary age source rock possible source rocks were selected and analyzed from different outcrops and wells and compared with the oils a negative correlation suggests that upper cretaceous intervals of limestone marl and black shale previously believed to be important source rocks can be discounted as an important contributor to talara basin oils instead the new data suggest a tertiary source rock eocene oligocene comparable to that of the progreso basin however no such source rock strata have yet been identified within the talara basin certain upper cretaceous samples with good source potential could support another petroleum system not yet identified in the coastal areas of peru

fractured shale gas systems the first commercial united states natural gas production 1821 came from an organic rich devonian shale in the appalachian basin understanding the geological and geochemical nature of organic shale formations and improving their gas producibility have subsequently been the challenge of millions of dollars worth of research since the 1970s shale gas systems essentially are continuous type biogenic predominant thermogenic or combined biogenic thermogenic gas accumulations characterized by widespread gas saturation subtle trapping mechanisms seals of variable lithology and relatively short hydrocarbon migration distances shale gas may be stored as free gas in natural fractures and intergranular porosity as gas sorbed onto kerogen and clay particle surfaces or as gas dissolved in kerogen and bitumen five united states shale formations that presently produce gas commercially exhibit an unexpectedly wide variation in the values of five key parameters thermal maturity expressed as vitrinite reflectance sorbed gas fraction reservoir thickness total organic carbon content and volume of gas in place the degree of natural fracture development in an otherwise low matrix permeability shale reservoir is a controlling factor in gas producibility to date unstimulated commercial production has been achievable in only a small proportion of shale wells those that intercept natural fracture networks in most other cases a successful shale gas well requires hydraulic stimulation together the devonian antrim shale of the michigan basin and devonian ohio shale of the appalachian basin accounted for about 84 of the total 380 bcf of shale gas produced in 1999 however annual gas production is steadily increasing from three other major organic shale formations that subsequently have been explored and developed the devonian new albany shale in the illinois basin the mississippian barnett shale in the fort worth basin and the cretaceous lewis shale in the san juan basin in the basins for which estimates have been made shale gas resources are substantial with in place volumes of 497 783 tcf the estimated technically recoverable resource exclusive of the lewis shale ranges from 31 to 76 tcf in both cases the ohio shale accounts for the largest share

diminutive frontal waves a link between fronts and cyclones abstract a number of recent publications have dealt with cyclone identification and tracking following on this paper extends the typical cyclone life cycle back in time to embrace a new feature called a diminutive frontal wave one aim is to improve predictability by extending tracks this is particularly important for small cyclonic windstorms which can often be missed in postprocessed output from operational ensemble and climate runs the recognition of diminutive waves requires a new front relative low level vorticity partition the parts are labeled frontal vorticity and disturbance vorticity and are computed respectively from front parallel and cross front low level wind components a diminutive frontal wave then lies wherever there is a local along front maximum in the disturbance vorticity computations require local coordinates these are conveniently provided at all grid points by objective front diagnostics analysis of cyclone type transitions over the north atlantic in opera

influence of co2 on new albany shale composition and pore structure abstract to determine the possible influence of co2 on the pore structure and mineralogy of the new albany shale devonian mississippian experiments were conducted utilizing indiana shale samples of varying total organic carbon content under various conditions after the shale samples were heated to as high as 150 c in teflon lined high pressure reaction cells with either distilled water or nacl brine and co2 the reaction products were characterized by mesopore and micropore analysis x ray diffraction and scanning electron microscope analysis of the shale residue and fluid chemistry analysis of the reactant brine results from co2 saturated shale and distilled water showed no changes in shale pore structure relative to shale samples without co2 surface saturation a second series of experiments was run at 80 c using 50 000 ppm nacl brine 60 mesh ground shale 2 1 by mass and varying amounts of solid co2 dry ice the pressure in the reaction cells was controlled by the partial pressure of co2 and ranged from 100 to 3500 psi 0 69 to 24 13 mpa post reaction brine samples showed up to thousands of ppm of k mg and ca in solution the concentration of ca and mg in the brine tended to increase in proportion to the increasing partial pressure of co2 the same experiments using chips of shale from the new albany shale showed lower concentrations of the cations in solution but displayed a similar pattern of increasing ca and mg with increasing co2 pressure scanning electron microscope examination of the shale chips confirmed the dissolution of carbonate mineralized biogenic structures in the shale

the arctic frontal zone as seen in the ncep ncar reanalysis abstract calculations of a thermal front parameter using ncep ncar reanalysis data over the period 1979 98 reveal a relative maximum in frontal frequencies during summer along northern eurasia from about 60 to 70 n best expressed over the eastern half of the continent a similar relative maximum is found over alaska which is present year round although best expressed in summer these high latitude features can be clearly distinguished from the polar frontal zone in the midlatitudes of the pacific basin and collectively resemble the summertime arctic frontal zone discussed in several early studies while some separation between high and midlatitude frontal activity is observed in all seasons the summer season is distinguished by the development of an attendant mean baroclinic zone aligned roughly along the arctic ocean coastline and associated wind maxima in the upper troposphere the regions of maximum summer frontal frequency correspond to preferred areas of cyclogenesis and to where the summertime

morphology genesis and distribution of nanometer scale pores in siliceous mudstones of the mississippian barnett shale research on mudrock attributes has increased dramatically since shale gas systems have become commercial hydrocarbon production targets one of the most significant research questions now being asked focuses on the nature of the pore system in these mudrocks our work on siliceous mudstones from the mississippian barnett shale of the fort worth basin texas shows that the pores in these rocks are dominantly nanometer in scale nanopores we used scanning electron microscopy to characterize barnett pores from a number of cores and have imaged pores as small as 5 nm key to our success in imaging these nanopores is the use of ar ion beam milling this methodology provides flat surfaces that lack topography related to differential hardness and are fundamental for high magnification imaging nanopores are observed in three main modes of occurrence most pores are found in grains of organic matter as intraparticle pores many of these grains contain hundreds of pores intraparticle organic nanopores most commonly have irregular bubblelike elliptical cross sections and range between 5 and 750 nm with the median nanopore size for all grains being approximately 100 nm internal porosities of up to 20 2 have been measured for whole grains of organic matter based on point count data from scanning electron microscopy analysis these nanopores in the organic matter are the predominant pore type in the barnett mudstones and they are related to thermal maturation nanopores are also found in bedding parallel wispy organic rich laminae as intraparticle pores in organic grains and as interparticle pores between organic matter but this mode is not common although less abundant nanopores are also locally present in fine grained matrix areas unassociated with organic matter and as nano to microintercrystalline pores in pyrite framboids intraparticle organic nanopores and pyrite framboid intercrystalline pores contribute to gas storage in barnett mudstones we postulate that permeability pathways within the barnett mudstones are along bedding parallel layers of organic matter or a mesh network of organic matter flakes because this material contains the most pores

nano scale pore structure and fractal dimension of organic rich wufeng longmaxi shale from jiaoshiba area sichuan basin investigations using fe sem gas adsorption and helium pycnometry abstract much attention have been recently paid to the upper ordovician wufeng shale o3w and lower silurian longmaxi shale s1l in the jiaoshiba area of sichuan basin which is now the largest producing shale gas field in china field emission scanning electron microscopy fe sem low pressure gas n2 and co2 adsorption helium pycnometry x ray diffraction and geochemical analyses were performed to investigate the pore structure and fractal dimension of the pores in o3w s1l shale formation in the jiaoshiba area fe sem images show that organic matter om pores are dominant in the organic rich samples and these pores are often irregular bubble like elliptical and faveolate in shape while in organic poor samples limited and isolated interparticle interp intraparticle intrap and om pores are observed reversed s shaped isotherms obtained from nitrogen adsorption are type and hysteresis loops indicate that the shape of micropore in the samples is slit or plate like bet surface areas and total pore volume vary from 12 2 to 27 1 m2 g and from 1 8 10 2 to 2 9 10 2 cm3 g with an average of 19 5 m2 g and 2 3 10 2 cm3 g respectively adsorption volume from both n2 and co2 adsorption increases with respect to toc contents porosities obtained from helium porosimetry are comparable with these from gas co2 and n2 adsorption in o3w s1l shale however porosity determined by quantitative fe sem analysis is much smaller which is mainly related to limited resolution and the small areas of investigation based on the frenkel halsey hill fhh model of low pressure n2 adsorption fractal dimensions of the pores varied from 2 737 to 2 823 relationships between pore structure parameters and toc content mineral composition and fractal dimension reveal that the fractal dimension is mainly associated with micropores samples with higher toc content higher quartz content and lower clay content tend to contain more heterogeneous micropores resulting in higher fractal dimensions and more complicated pore structure in shales therefore fractal dimension is an effective parameter to reflect the complexity of pore structure and the degree of micropore development in o3w s1l shale