suspended sediment transport in the surf zone response to cross shore infragravity motion a field experiment to investigate the magnitude and temporal and spatial scales of suspended sediment transport in the inner surf zone was conducted at san marine oregon on october 7 13 1984 instrumentation consisted of five electromagnetic current meters three strain gauge type pressure transducers and 25 optical backscatter sensors to measure the concentrations of suspended sediment the instruments were deployed approximately 70 m x seaward of the mean high water line mean depth h 1 1 1 3 m in a closely spaced cross shaped pattern data were collected for 68 min periods spanning high tide during the 7 day experiment during the experiment waves varied in angle of approach from shore normal to southwesterly offshore significant swell heights were 3 5 m with periods of 12 14 s local sea conditions with wind waves of approximately 8 s also occurred a visual estimation of the width of the surf zone indicated it to be approximately 500 m and the breaker pattern suggested that there were two longshore bars at approximately 200 and 500 m offshore the data resulting from the experiment encompass a broad range of wave and current conditions which included periods of extreme infragravity motion 30 t 300 s and weak longshore currents and periods of low infragravity motion and strong longshore currents periods of incident wave dominance also occurred the field study section of this paper qualitatively describes the sediment response to strong 240 cm s 1 low frequency 0 01 hz cross shore fluid motions which dominated the inner surf zone during two of the data runs the infragravity band accounted for 85 of the cross shore velocity variance the peak 0 01 hz of which was associated with shore normal standing waves concentration gradients of suspended sediment appear to be associated with diffusive processes and develop and decay on time scales of the infragravity motions rather than those of incident waves suspension events during times of infragravity dominance often persisted for periods of 30 45 s and reached peak concentrations of 20 40 g l 1 at elevations in excess of 26 cm mean suspended load was 3 4 times larger than that associated with incident wave motions the modeling section of the paper attempts to quantitatively describe the observed time dependent vertical suspended sediment distribution with a one dimensional turbulent diffusion model formulations of eddy diffusion and erosion rate coefficients associated with peak cross shore flows are found to agree with or fall within the range of values from previous laboratory and field studies and are used in the model the model is evaluated by its ability to reproduce the time dependent vertical distribution of suspended sediment and to estimate the observed mean suspended load and the correct direction and magnitude of the mean longshore and cross shore flux level above the bed z 31 cm of suspended sediment

storm induced response of a nearshore bar system abstract a nearshore bar system was surveyed periodically through a storm and the following recovery period the data showed a very rapid response of morphology to changing wave conditions and allowed various models on bar formation to be tested under low energy conditions prior to the storm a small bar was surveyed 13 m offshore both the high reflectivity of the beach and the cross shore distance to the bar are consistent with a model of sediment convergence at the node or antinode of a standing wave of incident period such a small scale bar may be a common feature on beaches with steep foreshores and more gentle offshore slopes with the increase in wave height during the storm the bar became better developed and migrated offshore at rates up to 2 2 m h 1 the bar maintained its form in that the ratio of trough depth to crest depth h t h c remained roughly constant the bar was in no way related to processes which would cause the convergence of sediment in the breaker zone through most of the storm the bar crest distance offshore was typically only 10 of the surf zone width analysis of the bar distance offshore in terms of a standing wave motion showed that the causative wave period must have been much longer than that of incident waves probably on the order of a minute surf zone wave data showed significant energy in the infragravity band at these periods although no definite link has been made after the height of the storm the bar had a crescentic morphology the development of this morphology occurred very rapidly with parts of the bar migrating onshore at rates up to 1 2 m h 1 in contrast to the storm during the recovery period h t h c varied by nearly a factor of three analysis of the offshore and longshore length scales showed the bar to be similar to one which would be generated by a standing mode 1 edge wave of period on the order of one minute

mass flux and undertow in a surf zone abstract the mass of water carried shoreward by the breaking waves in a surf zone will in a two dimensional situation be compensated by a seaward return flow the undertow it is shown that the undertow is driven by the local difference between radiation stress and the set up pressure gradient which only balance each other in average over the depth turbulent shear stresses are required to maintain a steady situation comparison with measurements confirms the theoretical results

direct measurements of bed stress under swash in the field 1 utilizing flush mounted hot film anemometry the bed stress under swash was measured directly in a field experiment conducted on barret beach fire island new york the theory development and calibration of the instrument package are discussed and results from the field experiment are presented examples of bed stress time series throughout a swash cycle are presented and an ensemble averaged swash bed stress cycle is calculated strong asymmetry is observed between the uprush and backwash phases of the swash flow the maximum bed shear stress exerted by the uprush is approximately double that of the backwash while the duration of the backwash is 135 greater than that of the uprush friction coefficients in the swash zone are observed to be similar in magnitude to those from steady flow with the mean observed friction coefficient equal to 0 0037 swash friction coefficients derived from the current measurements exhibit a reynolds number dependence similar to that observed for other flows a systematic difference between coefficients for uprush and backwash is suggested

the morphodynamics of beach ridge formation magilligan northern ireland abstract magilligan foreland is a holocene beach ridge plain comprising three principal sets of sand ridges sets i and ii are related to the mid holocene progradation of the plain while set iii represents recent deposition at the distal margin at present two types of beach ridge are being formed in both cases as part of the general recovery sequence following storm erosion of the dune cliffs mode i beach ridge development is associated with shore normal sediment transport under dissipative wave conditions these ridges form around the high water mark of spring tides through the migration of coalescence of swash bars within 30 to 55 days of a storm mode ii formation is more complex sediment initially stored in nearshore bars is moved alongshore causing bar elongation the bar moves into the intermediate and even reflective wave domains eventually narrowing of the bar leads to severance of a downdrift portion usually at or near the major drift pulse to the north west of the foreland normally this sediment starved remnant welds progressively onto the beach face in the direction of the dominant process gradient east to west but occasionally locally generated counteractive seas move sediment onshore employing the bar as a traverse conduit mode ii beach ridges emerge onto the upper beach around 90 150 days after a storm the beach ridges have distinctive structures depending on their mode of formation and both constitute important sources for dune building sand

composition and pore characteristics of black shales from the ediacaran lantian formation in the yangtze block south china the ediacaran period was critical in the evolution of the biosphere and ocean in the history of the earth shales rich in organic matter om are well developed for this period in the yangtze block china and have recently been related to shale gas exploration in south china to date detailed characterisation of the ediacaran shales is not available the present work sets out a detailed investigation of the composition and pore characteristics of samples from a shallow drill core in the ediacaran lantian formation in the lower yangtze area and the effects of shale composition on the pore growth are discussed the 90 m thick lantian black shales are highly over mature equivalent vitrinite reflectance evro value approximately 4 0 with a total organic carbon toc content up to 12 they are dominated by quartz 33 72 generally with low clay or feldspar content bulk porosities of the shales range from 1 0 to 7 9 and are positively correlated with toc content high magnification scanning electron microscopy sem images support the crucial importance of om content on pore development generally pore volume shows excellent positive correlation with toc content for micropores good correlation for mesopores and relatively poor correlation for macropores two samples with mostly high toc content showed very low macropore volume and medium mesopore volume these results suggest a close relationship between om with relatively small pores and enhanced compaction effect on large pores in highly om enriched shales

swash oscillations on a natural beach run up swash oscillations were measured on a gently sloping beach face for a variety of incident wave conditions run up energy spectra at wind wave frequencies show an 3 dependence and energy levels that are independent of incident wave height this suggests saturation in contrast run up energy at surf beat periods increase approximately linearly with increasing incident wave energy thus in the inner surf zone where wave breaking limits the energy at wind wave frequencies the principal manifestation of large incident wind waves is energetic surf beat

swash on steep and shallow beaches extensive field observations of swash on natural beaches are used to relate the magnitudes of swash oscillations to incident wave conditions and the beach slope swash fluctuations at wind wave frequencies defined here as f 05 hz appear to be saturated as in laboratory experiments with monochromatic waves wave breaking prevents the magnitudes of swash oscillations at incident wave frequencies from increasing past a certain level which depends on the beach slope all data sets considered support this conclusion in contrast the magnitude of swash oscillations at surf beat frequencies defined as f 05 hz varies between data sets possible reasons for the discrepancy are discussed despite their differences all data sets show that motions at surf beat frequencies dominate the swash spectrum on dissipative beaches as in previous studies the frequencies of spectral hills and valleys in the spectra of surf zone sensors suggests that a significant fraction of the surf beat energy is contained in motions which are standing in the cross shore direction preliminary analysis indicates that shoreward propagating surf beat is coupled to incident wave groups

sediment transport and beach profile evolution induced by bi chromatic wave groups with different group periods abstract in this paper large scale experimental data are presented showing the beach profile morphological evolution induced by four different bi chromatic wave conditions characterized by very similar energy content between them but varying the modulation period important differences were observed in the resultant beach profiles as a function of the wave group periods larger variability in the profile evolution is generally observed for larger wave group periods and more importantly as the wave group period increases the distance between the generated breaker bar and the shoreline increases the measured primary wave height to depth ratio increases with the wave group period which is consistent with the observed larger wave height at the breaking location the primary wave breaking location is also observed at increasing distances with respect to the initial shoreline as the wave group period increases the variation in with wave group period is related to the selective energy dissipation of the higher primary frequency component f1 during the wave group shoaling broad bandwith conditions reduced wave group period lead to larger dissipation of wave heights at the f1 component relative to f2 resulting in a reduction in the wave modulation and primary wave height at the breaking location suspended sediment fluxes obtained from collocated velocity and sediment concentration measurements in the surf zone showed a consistently larger contribution of the mean return flow to the suspended sediment fluxes compared with the wave group and primary wave components the distinct beach profile evolution in terms of bar location is interpreted from an increasing distance of the mean breakpoint location and the location of maximum return flow with respect to the shoreline as the wave group period increases

a comprehensive study on geometric topological and fractal characterizations of pore systems in low permeability reservoirs based on sem micp nmr and x ray ct experiments abstract characterization of pore systems in subsurface systems is of great importance for predicting the properties of rocks and classifying the subsurface systems geometric features have been used widely for this aim but topological characteristics of the pore structures are not studied much in fact accurate characteristics of pore space should comprise both its geometric and topological properties in this paper the above vital characteristics are comprehensively studied based on direct experimental results besides previous studies aiming at linking fractal dimension analysis to pore space are often based on limited sources of information which are the mercury injection capillary pressure micp and nuclear magnetic resonance nmr in this paper the scanning electron microscope sem micp nmr and x ray computed tomography x ray ct experiments are all used to characterize the geometric and topological properties of pore space of several low permeability porous media based on our observations the advantages and disadvantages of the above techniques in characterizing the pore structure are also summarized moreover the differences of these three experiments are quantified using fractal dimension the results indicate that the nmr technique is a promising tool for characterizing geometric features of pore systems as it can cover more details than other techniques most of geometric topological fractal and transport properties of pore space can be obtained from x ray ct method which is unique among all the methods in addition the 3d fractal dimensions of pore systems obtained from nmr is smaller than that from micp which is due more ultra micropores captured by nmr that smooth the surface of the pore systems finally a novel method constrained by a new pore shape factor for calculating the pore size from 2d images is proposed by which the pore size distributions are compared more effectively

probability distributions for wave runup on beaches measured probability distributions of shoreline elevation swash height shoreline excursion length and swash maxima and minima from a wide range of beach types are compared to theoretical probability distributions the theoretical distributions are based on assumptions that the time series are weakly steady state ergodic and a linear sum of random variables despite the swash process being inherently non linear results indicate that these assumptions are not overly restrictive with respect to modeling exceedence statistics in the upper tail of the probability distribution the rms errors for a range of exceedence level statistics 50 10 5 2 and 1 were restricted to 10 cm and often 5 cm for all of the swash variables that were investigated the results presented here provide the basis for further refinement of coastal inundation modeling as well as stochastic type morphodynamic modeling of beach response to waves further work is required however to relate the parameters of swash probability distributions to wave conditions further offshore c 2010 elsevier b v all rights reserved

microfracturing and microporosity in shales shales are ubiquitous rocks in sedimentary basins where their low permeability makes them efficient seals for conventional oil and gas reservoirs and underground waste storage repositories waste waters co2 nuclear fuels moreover when they contain organic matter they form source rocks for hydrocarbons that may escape towards a more porous reservoir during burial a process referred to as primary migration and when the hydrocarbons cannot escape these rocks can be exploited as oil or shale gas reservoirs while the presence of fractures at the outcrop scale has been described the existence of fractures at smaller scales their link with microporosity the mechanisms that created them their persistence over geological times and their effect on the petrophysical properties of shales represent scientific challenges for which drillings in various sedimentary basins over the past decades may hold timely key data here we review and synthetize the current knowledge on how microfractures and micropores in shales can be imaged and characterized and how they control their anisotropic mechanical properties and permeability one question is whether such microfractures when observed in outcrops or in drilled core samples extracted from boreholes are related to decompaction and do not exist at depth another question is whether veins observed in shales represent microfractures that were open long enough to have acted as flow paths across the formation the mechanisms of microfracture development are described some have an internal origin fracturing by maturation of organic matter dehydration of clays while others are caused by external factors tectonic loading importantly the amount of microfracturing in shales is shown to depend strongly on the content in 1 organic matter and 2 strong minerals the nucleation of microfractures depends on the existence of mechanical heterogeneities down to the nanometer scale their propagation and linkage to create a percolating network will depend on the presence of heterogeneities at the meso to macro scales such percolating microfracture networks could control both the long term sealing capabilities of cap rocks and the further propagation of hydraulic fracturing cracks finally possible areas of research for describing the mechanism of microfracture formation in greater detail and how this impacts the transport and mechanical properties of shales are also discussed

water saturation relations and their diffusion limited equilibration in gas shale implications for gas flow in unconventional reservoirs author s tokunaga tk shen w wan j kim y cihan a zhang y finsterle s abstract 2017 american geophysical union all rights reserved large volumes of water are used for hydraulic fracturing of low permeability shale reservoirs to stimulate gas production with most of the water remaining unrecovered and distributed in a poorly understood manner within stimulated regions because water partitioning into shale pores controls gas release we measured the water saturation dependence on relative humidity rh and capillary pressure pc for imbibition adsorption as well as drainage desorption on samples of woodford shale experiments and modeling of water vapor adsorption into shale laminae at rh 0 31 demonstrated that long times are needed to characterize equilibrium in larger 5 mm thick pieces of shales and yielded effective diffusion coefficients from 9 10 9 to 3 10 8 m2 s 1 similar in magnitude to the literature values for typical low porosity and low permeability rocks most of the experiments conducted at 50 c on crushed shale grains in order to facilitate rapid equilibration showed significant saturation hysteresis and that very large pc 1 mpa are required to drain the shales these results quantify the severity of the water blocking problem and suggest that gas production from unconventional reservoirs is largely associated with stimulated regions that have had little or no exposure to injected water gravity drainage of water from fractures residing above horizontal wells reconciles gas production in the presence of largely unrecovered injected water and is discussed in the broader context of unsaturated flow in fractures

a landslide in till near warman saskatchewan canada little information is available about typical shear strength parameters of tills in southern saskatchewan even though till is the most common earth material used for construction in this region the warman landslide in the south saskatchewan river valley provides some insight into the shear strength characteristics of a till and the results are compared with laboratory tests the till is from the upper till of the sutherland group which has a high clay content relative to the underlying and overlying tills a back analysis of the landslide produced 27 assuming c 0 comparison with laboratory test data and results from a similar landslide near lebret saskatchewan suggests that 22 5 with c 7 kpa may be appropriate residual shear strength parameters a rising water table appears to have been the main contributing factor to instability between 1969 and 1984 there is a possibility however that at the 1 50 return interval for flood levels on the river erosion at the toe of the landslid

nearshore bars and the break point hypothesis abstract the set of hypotheses calling for bar formation at the break point was tested with field data during two different experiments waves were measured across the surf zone coincident with the development of a nearshore bar we use a criterion based on the wave height to depth ratio to determine the offshore limit of the inner surf zone during the first experiment the bar became better developed and migrated offshore while remaining well within the inner surf zone during the second experiment the surf zone was narrower and we cannot rule out the possibility of break point processes contributing to bar development we conclude that bars are not necessarily coupled with the break point and can become better developed and migrate offshore while being in the inner surf zone landward from initial wave breaking in the outer surf zone

how does the pore throat size control the reservoir quality and oiliness of tight sandstones the case of the lower cretaceous quantou formation in the southern songliao basin china abstract pore throat size is a very crucial factor controlling the reservoir quality and oiliness of tight sandstones which primarily affects rock properties such as permeability and drainage capillary pressure however the wide range of size makes it difficult to understand their distribution characteristics as well as the specific controls on reservoir quality and oiliness in order to better understand about pore throat size distribution petrographic scanning electron microscopy sem pressure controlled mercury injection pmi rate controlled mercury injection rmi quantitative grain fluorescence qgf and environmental scanning electron microscopy esem investigations under laboratory pressure conditions were performed on a suite of tight reservoir from the fourth member of the lower cretaceous quantou formation k 1 q 4 in the southern songliao basin china the sandstones in this study showed different types of pore structures intergranular pores dissolution pores pores within clay aggregates and even some pores related to micro fractures the pore throat sizes vary from nano to micro scale the pmi technique views the pore throat size ranging from 0 001 m to 63 m and revealed that the pore throats with radius larger than 1 0 m are rare and the pore throat size distribution curves show evident fluctuations rmi measurements indicated that the pore size distribution characteristics of the samples with different porosity and permeability values look similar the throat size and pore throat radius ratio distribution curves had however significant differences the overall pore throat size distribution of the k 1 q 4 tight sandstones was obtained with the combination of the pmi and rmi methods the permeability is mainly contributed by a small part of larger pore throats less than 30 and the ratio of the smaller pore throats in the samples increases with decreasing permeability although smaller pore throats have negligible contribution on reservoir flow potential they are very significant for the reservoir storage capacity the pore throats with average radius larger than 1 0 m mainly exist in reservoirs with permeability higher than 0 1md when the permeability is lower than 0 1md the sandstones are mainly dominated by pore throats with average radius from 0 1 m to 1 0 m the ratio of different sized pore throats controls the permeability of the tight sandstone reservoirs in different ways we suggest that splitting or organizing key parameters defining permeability systematically into different classes or functions can enhance the ability of formulating predictive models about permeability in tight sandstone reservoirs the pmi combined with qgf analyses indicate that oil emplacement mainly occurred in the pore throats with radius larger than about 0 25 0 3 m this result is supported by the remnant oil micro occurrence evidence observed by sem and esem

infragravity waves over a natural barred profile measurements of cross shore flow were made across the surf zone during a storm as a nearshore bar became better developed and migrated offshore measured infragravity band spectra were compared to synthetic spectra calculated numerically over the natural barred profile assuming a white run up spectrum of leaky mode or high mode edge waves as in earlier studies the spectra compared closely however for some frequencies the energy of the measured spectrum exceeded the energy of the synthetic spectrum suggesting that the run up spectrum was not white but had dominating frequencies utilizing cross shore flow data and synthetic spectra from a number of cross shore locations an equivalent run up spectrum was calculated for each day on the first day of the storm the equivalent run up spectrum indicated a dominant wave that had a node in velocity reasonably close to the bar crest later during the storm when the bar had migrated farther offshore there was no evidence for a dominant motion having a velocity node at the bar crest the structure of the equivalent run up spectrum compared well with spectra of direct measurements of run up obtained several hundred meters away we have no clear evidence in support of the theory that infragravity waves might form or force the offshore migration of a bar to confirm this finding longer records obtained synoptically over a developing bar are required the dominant wave observed early in the storm was consistent with symond and bowen s 1984 theoretical prediction of resonant amplification of discrete frequencies over a barred profile

petrophysical characterization of tight oil sandstones by microscale x ray computed tomography abstract tight oil sandstones have complex pore structure due to multiple pore types and multiscale pore size ranging from several nanometers to dozens of microns in this study petrophyiscal properties of tight oil sandstones were quantified based on microscale x ray computed tomography xct imaging techniques the pore types in gray scale images were identified porosity pore size distribution psd and pore connectivity were analyzed from segmented image stacks and their permeability was calculated by representative elementary volume rev scale lattice boltzmann method lbm three types of pores including residual interparticle pores grain dissolution pores and micro fractures were identified a multi threshold segmentation algorithm was applied to segment the image stacks into three constituents namely pore matrix and clay the calculated volumetric fraction of the pore constituent from the segmented image stacks was smaller than experimental porosity because a certain amount of porosity was also contributed by clay constituent the psd of the samples was found to be unimodal in the range of 3 69 m with the peak at around 10 15 m the clay constituent led to the increase in the overall connectivity of the images stacks indicating that clays bridged the isolated pores by assigning appropriate porosity and permeability to the clay constituent calculated permeability of the samples using rev scale lbm well matched the experimental data this study provides new insight into characterization of pore structure of tight oil sandstones by xct technique

comparison of pore systems of clay rich and silica rich gas shales in the lower silurian longmaxi formation from the jiaoshiba area in the eastern sichuan basin china abstract the jiaoshiba area in the eastern sichuan basin hosts the largest commercial shale gas field in china with an annual production of 1 7 bcf the gases are primarily produced from the clay rich siliceous marine shales in the wufeng and longmaxi formations in this paper sixteen organic rich shale samples from a variety of lithofacies from the longmaxi formation in the jiaoshiba area were studied to evaluate the pore systems of clay rich shales by comparison with the silica rich gas shales the investigation includes the assessment of porosity and pore size distribution by means of shale bulk and skeletal density measurements low pressure n2 co2 gas adsorption and mercury intrusion the shale samples with different lithofacies have porosity values ranging from 3 25 to 5 65 and display similar fractional volumes of micropores mesopores and macropores and corresponding specific surface areas all three pore fractions contribute to the shales total pore volumes while the total specific surface areas are mainly contributed to by micropores and mesopores there is a positive correlation between pore volumes and toc contents indicating that the porosities in the shales are dominated by organic matter pores with toc content being the main parameter controlling pore development toc normalized pore volumes decrease with a further increase in the toc content from 1 6 to 4 2 this may be related to the fact that the toc rich shales are more susceptive to mechanical compaction clay mineral content appears to have little effect on the pore volume or specific surface area development in the shales shale samples with clay rich siliceous shale lithofacies display similar toc contents porosities and fractional volumes of all pore sizes and specific surface areas with those of the silica rich argillaceous and argillaceous siliceous mixed lithofacies this suggests that the marine shales with silica rich argillaceous and argillaceous siliceous mixed lithofacies from the longmaxi formation in the jiaoshiba area are capable of generating significant amount of pore spaces for shale gas storage

top seal development in the shale dominated upper devonian catskill delta complex western new york state the preferential generation of vertical natural hydraulic fractures at the contact of the upper devonian hanover gray shale and overlying dunkirk black shale of the catskill delta complex western new york state suggests that the latter served as a hydraulic top seal to formation fluids migrating upward from deeper in the sediment pile petrophysical properties and small scale textural characteristics of these siliceous fine grained rocks confirm the crucial role of depositional environment and sequence stratigraphic position of a shale lithotype in determining its sealing capacity the especially high sealing capacity of the basal interval of the dunkirk shale inferred early high stand systems tract hst strata reflects the anoxic depositional environment of these deposits that favored the preservation of their abundant organic matter and finely laminated depositional texture the absence of bioturbation enabled the undisrupted sediment notably carbonaceous clay rich laminae to undergo rapid mechanical compaction platy grain reorientation and porosity reduction compaction induced squeezing of ductile organic matter into void spaces further reduced pore throat diameters immediately underlying heavily bioturbated deposits of the organic lean hanover shale inferred upper hst or low stand wedge sediments accumulated in a dysoxic depositional environment disruption of layering and homogenization of sediment by burrowing organisms produced a more porous and permeable microfabric through which formation fluids moved only to be arrested by the high capillary entry pressures at the base of the dunkirk shale natural hydraulic fractures some of which propagated into the dunkirk shale formed when fluid pressure at the top of the hanover shale reached the fracture gradient the high sealing capacity of the basal dunkirk shale was probably enhanced by its finely laminated nature and the generation of biogenic methane both of which contributed to the formation of a near impermeable gas capillary seal

comparison of diagenetic characteristics and pore evolution in outcrops and cores of tight sandstone reservoirs in the triassic yanchang formation the ordos basin china the sedimentary and diagenetic control on tight sandstone reservoir quality is a key focus of hydrocarbon exploration this paper compares reservoir characteristics such as diagenetic processes pore types and porosity evolution of cores and outcrops of the yanchang formation the ordos basin northwestern china to identify diagenetic trends and processes responsible for improving reservoir quality and to develop a model for identifying reservoir sweet spots in tight sandstone formations samples of the yanchang formation sandstone are taken from wells and adjacent outcrops in the ordos basin no significant differences were found in porosity destructive diagenesis such as compaction and cementation between the core and outcrop samples however the effects of dissolution are far more pronounced in cores than in the outcrop resulting in a higher core sample porosity high density sampling of the outcrop revealed that the reservoir sweet spot model is controlled by sedimentation whereas three distinct vertical diagenetic zones were identified in adjacent wells a comprehensive analysis of cores and outcrop samples shows that both areas experienced similar sedimentation and early diagenetic patterns however the diagenetic processes experienced by core and outcrop sandstones diverged during the later part of burial and uplift with dissolution being responsible for the contrasting reservoir porosities between core and outcrop

beach systems of the central netherlands coast processes morphology and structural impacts in a storm driven multi bar system abstract the 124 km long central netherlands coast consists of a sand barrier system fronted by beach and surf zone containing 2 to 3 bars the beach and surf zone are the product of wind waves generated in the north sea interacting with the medium to fine shoreface sands in a micro tidal environment the inner bar is usually attached to the beach as a ridge and runnel cut by drains and rips the second and third bars are highly rhythmic and are characterised respectively by transverse bars and rips and rhythmic to longshore bar and trough bar types structural impacts influence 48 km of shore with harbour moles inducing lower wave energy and shoreline progradation a 4 5 km long dyke replaces part of the beach but apparently has had little impact on mesoscale bar dynamics while 158 groynes in three fields have produced more intermediate rip driven surf zones natural beach processes however dominate the entire coast with the hierarchical bar morphology related to cross shore wave breaking the equilibrium beach concept of wright et al 1987 was used to empirically predict beach bar type the results explain both the hierarchy of bar type and the temporal variation in beach bar type finally a multi bar beach model for the coast is presented which builds upon the single bar model of wright and short 1984

wave setup a field study a new and efficient method is described for obtaining field measurements of surf zone mean water levels the method applies manometer tubes rather than the traditional pressure transducers and hence makes it unnecessary to survey the vertical positions of the sensors a substantial data base is obtained which apart from quantitative data for the field site and similar beaches gives clear general indications of where previous wave setup models need to be amended it is clear from the data that while traditional setup models work reasonably well seaward of the still water line the most landward part of the mean water surface on fairly steep beaches at least requires radically different models it is still possible however to obtain reasonable estimates of the shoreline setup by tying together the concepts of setup and runup and utilizing presently available empirical formulae for the maximum runup level

waves currents sediment flux and morphological response in a barred nearshore system abstract a shore normal array of seven bi directional electromagnetic flowmeters and nine surface piercing continuous resistance wave staffs were deployed across a multiple barred nearshore at wendake beach georgian bay canada and monitored for a complete storm cycle time integrated estimates of total itvf and net invf sediment volume flux together with bed elevation changes were determined using depth of activity rods the three bars ranging in height from 0 10 to 0 40 m accreted during the storm 0 03 m and the troughs were scoured 0 05 m sediment reactivation depths reached 0 14 m and 12 of the nearshore control volume was mobilized however the invf value for the storm was less than 1 of the control volume revealing a near balance in sediment volume in the bar system landward migration of the inner crescentic and second sinuous bars occurred in association with an alongshore migration of the bar form itself the outermost straight shore parallel bar remained fixed in location the surf zone was highly dissipative throughout the storm 3 8 10 2 192 10 2 and the wave spectrum was dominated by energy at the incident frequency spectral peaks at frequencies of the first harmonic and at one quarter that of the incident wave were associated with secondary wave generation just prior to breaking and a standing edge wave respectively the former spectral peak was within the 95 confidence band for the spectrum while the latter contributed not more than 10 to the total energy in the surface elevation spectrum even near the shoreline during the storm wave height exceeded 2 m h s and periods reached 5 s t p k orbital velocities exceeded 0 5 m s 1 u rm s and were above the threshold of motion for the medium to fine sands throughout the storm shore parallel flows in excess of 0 4 m s 1 were recorded with maxima in the troughs and minima just landward of the bar crest the rate and direction of sediment flux is best explained by the interaction of antecedent bed slopes with spatial gradients in the mean and asymmetry of the shore normal velocity field these hydrodynamic parameters represent steady flows superimposed on the dominantly oscillatory motion and assumed a characteristic spatial pattern from the storm peak through the decay period increases spatially in the magnitudes of both the mean flows and flow asymmetries cause an increasing net transport potential erosion decreases in these values spatially cause a decreasing net transport potential and thus deposition these transport potentials are increased or decreased through the gravity potential induced by the local bed slope shore parallel flow was important in explaining sediment flux and morphological change where orbital velocities mean flows and flow asymmetries were at a minimum

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

pore throat sizes in sandstones tight sandstones and shales pore throat sizes in siliciclastic rocks form a continuum from the submillimeter to the nanometer scale that continuum is documented in this article using previously published data on the pore and pore throat sizes of conventional reservoir rocks tight gas sandstones and shales for measures of central tendency mean mode median pore throatsizes diameters are generally greater than2 mm in conventionalreservoir rocks range from about 2 to 0 03 mm in tight gas sandstones and rangefrom0 1to0 005 mminshales hydrocarbonmolecules asphaltenes ring structures paraffins and methane form another continuum ranging from 100 a 0 01 mm for asphaltenes to 3 8 a 0 00038 mm for methane the pore throat size continuum provides a useful perspective for considering 1 the emplacement of petroleum in consolidated siliciclastics and 2 fluid flow through fine grained source rocks now being exploited as reservoirs

fractal analysis of tight shaly sandstones using nuclear magnetic resonance measurements assessing quantitatively the microscopic pore structures of porous rocks including irregularities of pore shapes and pore size distributions is becoming one of the most challenging efforts nuclear magnetic resonance nmr measurements were used to provide insights into the pore geometry pore size and shape and pore connectivity of the chang 7 tight shaly sandstones in situ permeability 0 1 md in ordos basin the incremental transverse relaxation time t2 distributions for the 100 brine saturated samples display unimodal and bimodal behaviors presenting a geometrical arrangement composed of small to large pore size domains the nmr parameters such as bulk volume irreducible bvi capillary and clay bound water free fluid index ffi movable water the value of t2 separating the bvi from ffi the amplitude weighted mean on a logarithmic scale t2gm and the value of t2 that shows the highest frequency on the t2 spectrum t2peak for each sample were determined then the fractal theory was adopted to quantitatively express the complexity and heterogeneity of the sandstones the results show that only minor primary intergranular porosity remains and variable amounts of micropores and secondary intragranular porosity with poor connectivity occur in the chang 7 tight shaly sandstones assuming spherical pores a new model to calculate the fractal dimension of pore structure from the nmr t2 distributions is proposed the fractal dimensions of all the samples are calculated and the accuracy of the proposed model is verified by the regression coefficients the microscopic pore structures are heterogeneous in these tight sandstones according to the high value of fractal dimensions micropores are the primary causes of heterogeneity in tight sandstones and samples with unimodal t2 distribution behaviors and high content of short components have the highest fractal dimension and heterogeneity the calculated fractal dimension is strongly correlated with t2peak and t2gm therefore the fractal model proposed in this study can be used to calculate the fractal dimensions and evaluate the heterogeneities of the porous rocks satisfactorily the fractal model proposed in this study helps to quantitatively assess the pore structures of tight sandstones using nmr measurements

pore structure wettability and spontaneous imbibition of woodford shale permian basin west texas abstract even after more than 30 years of exploration and production low total recovery of shale gas

formation of magnetic minerals at hydrocarbon generation conditions in this paper we report the pyrolysis and formation of magnetic minerals in three source rock samples from the wessex basin in dorset southern england the experimental conditions in the laboratory recreated the catagenesis environment of oil source rocks magnetic analysis of both the heated and the unheated samples at room temperature and at very low temperatures 5 k coupled with transmission electron microscopy imaging and x ray analysis revealed the formation of nanometre sized 10 nm magnetic particles that varied across the rock samples analysed but more importantly across the pyrolysis temperature range magnetic measurements demonstrated the formation of these magnetic minerals peaked at 250 c for all rock samples and then decreased at 300 c before rising again at 320 c the newly formed magnetic minerals are suggested to be primarily pyrrhotite though magnetite and greigite are also thought to be present the sizes of the magnetic minerals formed suggest a propensity to migrate together with oil potentially explaining the magnetic anomalies observed above and within oil fields

the dependency of inshore long waves on the characteristics of offshore short waves abstract this paper pursues the feasibility of establishing workable site specific relationships between concurrent inshore long wave characteristics and offshore short wave characteristics such relationships would have immediate relevance to the design of wave climate date collection systems for proposed ship mooring facilities a strong dependency was shown to exist between inshore long wave height and the height and frequency of the offshore short waves but no similar dependency was found for long wave frequency the possibility of a dependency between inshore long wave frequency and the group frequency of the offshore short waves was also pursued this proved inconclusive because wave group frequencies in a quasi stationary sea state were shown to be an extremely variable quantity such that the wave records to which the authors had access were too short to provide stable statistical descriptions of the characteristic group frequencies this leads to recommendations regarding the required minimum lengths of wave records when seeking data on wave group frequencies

beach morphodynamics in a strong wind bay a low energy environment abstract the morphodynamic behaviour of a multibarred beach in a fetch limited strong wind bay seaford beach se australia was examined during both high and low energy conditions and considered in the context of a definition of low energy provided in the literature measurements of nearshore waves currents and morphology revealed a bimodal behaviour under initial low energy conditions the beach exhibited a low tide terrace state and waves and currents were of very low magnitude during subsequent high energy conditions the beach demonstrated dynamic behaviour through the formation of a transitional transverse bar and rip rhythmic bar and beach and migration of the middle bar with the morphology remaining in an arrested high energy state during intervening low energy periods although broadly conforming to the morphodynamic model the beach did exhibit some distinct characteristics attributable to its fetch limited location limited progression through the morphodynamic model and the importance of wind direction and magnitude in governing morphodynamic behaviour furthermore rip currents were not significant in driving beach change through intermediate states the presence of infragravity energy in the storm wave spectra a dissipative multibarred surf zone dynamic inner and middle bars and the attainment of a transitional transverse bar and rip rhythmic bar and beach state during rising wave conditions underline seaford beach as bimodal exhibiting process and morphologic features of both higher and lower energy beaches as an example of a beach in a strong wind bay seaford illustrates that not all fetch limited beaches are low energy furthermore the presence of infragravity energy in a highly fetch limited environment indicates that infragravity energy may occur commonly in fetch limited environments that are subject to periodic strong winds a process that has remained largely unrecognised

a rock physics model for characterizing the total porosity and velocity of shale a case study in fuling area china abstract the total porosity in a shale gas reservoir is the key parameter to evaluate its potential production capability petroleum geologists have been pursuing an accurate way of predicting total porosity in shale gas reservoirs from logging curves in the fuling area near chongqing in china we use core test data and well logging data in order to establish a logging response model for porosity through the analysis of the data we found that the porosity and the p sonic p velocity have a strong correlation by combining our results with previous research i e physical rock data we establish a new model which better predicts the total porosity of a given a shale reservoir than the models established in previous research in addition to total porosity mineral composition pore pressure pore fluid type and confining pressure affect p velocity by taking a series of artificial cores as test objects and systematic analysis of total porosity mineral composition and content pore fluid type and pressure on the p velocity we establish response templates between every individual parameter and p velocity to this end we further establish a multi parameter rock physical characterization equation for the total porosity and p velocity and analyze its applicable conditions using the rich geological and geophysical data of the lower silurian series in the fuling area we gradually improve the model for the total porosity and verify the results using well logging data finally a set of accurate methods are established to predict the total porosity in shale gas reservoirs by using well logging data

experimental investigation into the sealing capability of naturally fractured shale caprocks to supercritical carbon dioxide flow geological storage of co2 is considered a solution for reducing the excess co2 released into the atmosphere low permeability caprocks physically trap co2 injected into underlying porous reservoirs injection leads to increasing pore pressure and reduced effective stress increasing the likelihood of exceeding the capillary entry pressure of the caprocks and of caprock fracturing assessing on how the different phases of co2 flow through caprock matrix and fractures is important for assessing co2 storage security fractures are considered to represent preferential flow paths in the caprock for the escape of co2 here we present a new experimental rig which allows 38 mm diameter fractured caprock samples recovered from depths of up to 4 km to be exposed to supercritical co2 scco2 under in situ conditions of pressure temperature and geochemistry in contrast to expectations the results indicate that scco2 will not flow through tight natural caprock fractures even with a differential pressure across the fractured sample in excess of 51 mpa however below the critical point where co2 enters its gas phase the co2 flows readily through the caprock fractures this indicates the possibility of a critical threshold of fracture aperture size which controls co2 flow along the fracture

insight into pore throat size distribution and the controls on oil saturation of tight sandstone reservoirs using nuclear magnetic resonance parameters a case study of the lower cretaceous quantou formation in the southern songliao basin china pore throat structure characterization is crucial in tight oil sandstone reservoir studies to better understand pore throat size distribution and the effects on reservoir oil saturation petrographic scanning electron microscopy quantitative grain fluorescence qgf nuclear magnetic resonance nmr and pressure controlled mercury injection investigations were performed on a suite of tight sandstones from the fourth member of the lower cretaceous quantou formation k1q4 in the southern songliao basin china the tight sandstone samples showed similar compositional and textural maturity but different reservoir qualities at different depth intervals two oily indicators qgf index and qgf on extract spectra intensity varied significantly with respect to burial depth suggesting the existence of strong oil heterogeneities in the k1q4 tight sandstones oil emplacement occurred mainly in the primary pores associated with the absence of pore filling authigenic minerals pore throat size distributions had wider ranges in the oil rich layers than in the samples lacking oil emplacement the nmr pore throat radii ranged from 0 01 to 10 m in oil lacking samples but ranged from 0 01 to 100 m in oil rich layers oil signals were mainly detected in the pore throats with radii ranging from approximately 0 1 to 1 0 m in oil rich layers the nmr porosity can be divided into three parts based on transverse relaxation time t2 spectrum 1 immovable fluid 2 porosity of effective movable fluid pemf and 3 porosity of bound fluid bivariate plots of the ratios of various porosity types have significant effects in deciphering the oil saturation of tight sandstone reservoirs the pemf reflected well the reservoir qgf index among others therefore it can be considered as an effective nmr parameter to characterize pore size distribution and helpful in oil reservoir prediction a good relationship exists between pemf and geometric mean of the t2 distribution t2gm indicating that t2gm could also reflect reservoir oil saturation the pemf is mainly contributed by large pore throats and the poorly sorted pore throat distribution is better for effective movable fluids occurrence in tight sandstones the approach employed in this study provides a more comprehensive and accurate pore throat structure characterization in tight sandstone oil reservoirs generating effective parameters and convenient ways to evaluate reservoir oil saturation importantly it could be applicable for improving tight sandstone oil exploration and development efficiencies

morphodynamics of a bar trough surf zone abstract a field study was made of the distinguishing morphodynamic processes operating in a surf zone which perennially exhibits accentuated bar trough topography the longshore bar trough and rhytmic bar and beach states as described by wright and short 1984 characteristic features of the morphology include a shallow bar with a steep shoreward face a deep trough and a steep beach face this morphology which is favored by moderate breaker heights and small tidal ranges strongly controls the coupled suite of hydrodynamic processes in contrast to fully dissipative surf zones the bar trough surf zone is not at all saturated and oscillations at incident wave frequency remain dominant from the break point to the subaerial beach the degree of incident wave groupiness does not change appreciably across the surf zone infragravity standing waves which in dissipative surf zones dominate the inshore energy remain energetically secondary and occur at higher frequencies in the bar trough surf zone analyses of the field data combined with numerical simulations of leaky mode and edge wave nodal antinodal positions over observed surf zone profiles indicate that the frequencies which prevail are favored by the resonant condition of antinodes over the bar and nodes in the trough standing waves which would have nodes over the bar are suppressed sediment resuspension in the surf zone appears to be largely attributable to the incident waves which are the main source of bed shear stress in addition the extra near bottom eddy viscosity provided by the reformed non breaking waves traversing the trough significantly affects the vertical velocity profile of the longshore current whereas the bar is highly mobile in terms of onshore offshore migration rates the beach face and inner regions of the trough are remarkably stable over time

regularity and randomness in the formation of beach cusps abstract controversy still exists on whether rhythmic features such as beach cusps are the result of the presence of standing edge wave motions in the hydrodynamics or if they are the result of self organising processes the compatibility between the two mechanisms is here investigated through the use of a numerical model simulating the formation and development of beach cusps simulations characterised by different forcing conditions have been performed a series of random simulations each individual run simply differing from the others in the seed used in the random number generator showed the typical self organisation behaviour with the features appearing at different locations and even with slightly different spacing regular series of simulations have been run by changing the wavelength of the template superimposed by the hydrodynamic forcing and the number of cycles when the template was present results surprisingly indicate that even a minimum number of cycles with a regular forcing can deterministically induce the final shoreline configuration furthermore if the forcing template has the same wavelength as the one resulting from purely random simulations growth rates are much faster than those obtained with random conditions implications for the kind of field measurements necessary to discern which of the two mechanisms is responsible for beach cusp formation have also been considered

bar generating cross shore flow mechanisms on a beach random waves normally incident on a dissipative beach induce a variety of cross shore flows such as asymmetric oscillatory flow wave grouping induced long wave flow breaking induced turbulent flow and momentum decay induced undertow these flows are identified analyzed and hindcasted in a set of laboratory experiments with the aim of revealing the role of each of the flow mechanisms in the two dimensional case of bar generation on a beach

spectral signatures for swash on reflective intermediate and dissipative beaches in this paper we synthesise a large data set gathered from a wide variety of field deployments and integrate it with previously published results to identify the spectral signatures of swash from contrasting beach types the field data set includes the full range of micro tidal beach types reflective intermediate and dissipative with beach gradients ranging from approximately 1 6 to 1 60 exposed to offshore significant wave heights of 0 5 3 0 m the ratio of swash energy in the short wave f 0 05 hz to long wave f 0 05 hz frequency bands is found to be significantly different between the three beach types swash energy at short wave frequencies is dominant on reflective and intermediate beaches and swash at long wave frequencies is dominant on dissipative beaches consistent with previously reported spectral signatures for the surf zone on these beach types the available swash spectra were classified using an automated algorithm clara into five different classes the ordered classes represent an evolution in the spectrum shape described by a frequency downshifting of the energy peak from the short wave into the long wave frequency band and an increase in the long wave swash energy level compared to a relatively minor variation in the short wave swash energy level a universally common feature of spectra from all beach states was an f 4energy roll off in the short wave frequency band in contrast to the broadly uniform appearance of the short wave frequency band the appearance of the long wave frequency band was highly variable across the beach states we incorporate the results presented here and previously published observations into the morphodynamic beach state model and propose an ordered sequence of swash spectra under increasing and decreasing incident wave energy level this extension of the beach state model to include the swash zone leads to the following propositions for morphodynamic controls on the nature of the swash spectrum 1 the short wave part of the swash spectrum is relatively constant in form across all beach states f 4 energy roll off and the energy density per unit frequency is controlled by the beach face gradient alone 2 the spectral bandwidth of the energy roll off varies directly with offshore wave energy level and inversely with beach face gradient or beach state in a manner consistent with the non linear wave breaking criterion 3 the infragravity part of the swash spectrum is highly variable in form across all beach states and the energy level is related to the offshore wave energy level and surf zone morphology

bar formation due to wave groups and associated long waves abstract field observations reveal that waves propagating onto a beach from deeper water have a grouped structure associated with this pattern of alternating high and low waves is a long wave forced by radiation stress variations due to the changing short wave height as the wave groups propagate onshore the relationship between the variation in the short wave height and the long wave motion is complicated by breaking of the short waves reflection of the long wave and the generation of a free long wave by time variation of the breakpoint position nevertheless there may still be a fixed phase relation between the short wave envelope and the long wave motion at any particular location resulting in a net transport of sediment over the timescale of the short wave groups this transport arises from sediment grains mobilised by short waves and moved by the long wave motion model predictions of wave group propagation onto a beach and the associated long wave motions are presented which suggest that sediment transport due to short wave long wave coupling may result in the formation of a bar within the inner surf zone and the possibility of additional bars further offshore outside the surf zone this mechanism for bar formation may provide a new framework for understanding bar morphodynamics

field observations of surf beat 1 progressive edge waves nineteen biaxial electromagnetic current meters have been used to determine the longshore and on offshore structure of currents at surf beat periods 1 4 min the sensors formed two linear arrays a long shore array within the surf zone and an on offshore array stretching from the shoreline to well beyond the breaker line analysis of the longshore current components yields a clear picture of progressive low mode edge waves with frequency wave number dispersion relations which are in remarkably good agreement with predictions some separation of edge wave modes is found with mode zero energy dominating in the frequency band 0 006 and 0 011 hz and mode one between 0 015 and 0 025 hz on offshore currents present a rather different picture which while not inconsistent with the longshore currents suggests that other sources of energy are also important to the on offshore currents these include standing edge waves probably formed by reflections at nearby scripps canyon and motions which are nonresonantly forced by incoming wave groups

large scale experiments on beach profile evolution and surf and swash zone sediment transport induced by long waves wave groups and random waves new large scale laboratory data are presented on the influence of long waves bichromatic wave groups and random waves on sediment transport in the surf and swash zones physical model testing was performed in the large scale ciem wave flume at upc barcelona as part of the susco swash zone response under grouping storm conditions experiment in the hydralab iii program vicinanza et al 2010 fourteen different wave conditions were used encompassing monochromatic waves bichromatic wave groups and random waves the experiments were designed specifically to compare variations in beach profile evolution between monochromatic waves and unsteady waves with the same mean energy flux each test commenced with approximately the same initial profile the monochromatic conditions were perturbed with free long waves and then subsequently substituted with bichromatic wave groups with different bandwidth and with random waves with varying groupiness beach profile measurements were made at half hourly and hourly intervals from which net cross shore transport rates were calculated for the different wave conditions pairs of experiments with slightly different bandwidth or wave grouping show very similar net cross shore sediment transport patterns giving high confidence to the data set consistent with recent small scale experiments the data clearly show that in comparison to monochromatic conditions the bichromatic wave groups reduce onshore transport during accretive conditions and increase offshore transport during erosive conditions the random waves have a similar influence to the bichromatic wave groups promoting offshore transport in comparison to the monochromatic conditions the data also indicate that the free long waves promote onshore transport but the conclusions are more tentative as a result of a few errors in the test schedule and modifications to the setup which reduced testing time the experiments suggest that the inclusion of long wave and wave group sediment transport is important for improved near shore morphological modeling of cross shore beach profile evolution and they provide a very comprehensive and controlled series of tests for evaluating numerical models it is suggested that the large change in the beach response between monochromatic conditions and wave group conditions is a result of the increased significant and maximum wave heights in the wave groups as much as the presence of the forced and free long waves induced by the groupiness the equilibrium state model concept can provide a heuristic explanation of the influence of the wave groups on the bulk beach profile response if their effective relative fall velocity is larger than that of monochromatic waves with the same incident energy flux

acoustic measurements of suspended sand concentration in the c2s2 experiment at stanhope lane prince edward island abstract a 3 mhz acoustic concentration meter acm was deployed with electromagnetic flowmeters in the nearshore region in october 1984 at stanhope lane prince edward island canada as a component of the canadian coastal sediment study the acm measured the backscatter of acoustic energy in a vertical beam pattern within approximately 1 m of the seabed laboratory calibration experiments were conducted to verify a method for converting acoustic backscatter into suspended sand concentration profiles the acm functioned well when there were no air bubbles in the water both the suspended sand concentration profiles and the bottom location were measured with an approximately 1 s time resolution and a 1 cm vertical spatial resolution the suspension of sand is related to the wave and current forcing and is dominated by events of short duration

modification of edge waves by barred beach topography a numerical model to calculate edge wave profiles and wavelengths for arbitrary bottom profiles and given frequency was developed utilizing the model wave equation of berkhoff 1972 following smith and sprinks 1975 surface profiles and longshore wave numbers were found for fixed wave periods using an eigenvalue approach the model was verified by calculating profiles and dispersion for a plane beach of mild slope and comparing results with the analytic solution of eckart 1951 and ursell 1952 the model was then applied to the case of a beach with multiple offshore bars with bar positions determined by the antinodal positions of a standing incident wave of a set frequency calculation of surface profiles for a range of frequencies using a fixed beach indicated that antinodes of the edgewave profiles tend to be trapped by the bars suggesting the possibility that bars affect the long wave climate in such a way as to lead to self maintenance over extended periods no effect of the bars on the dispersion relationship was found and it was concluded that for the particular beach profile used the edge waves respond to the mean beach slope over the offshore length of the profile

infragravity waves and nearshore bars in protected storm dominated coastal environments abstract field measurements of run up oscillations were conducted on fetch restricted storm wave dominated beaches in denmark experiments took place under conditions with breaker heights of 1 5 3 m and wave periods of 5 7 s statistically significant spectral peaks were identified in the infragravity regime the frequencies of these peaks were compared to frequencies predicted by the edge wave cut off model originally proposed by huntley j geophys res 81 1976 and it was found that the waves were probably cut off mode edge waves with the mode number corresponding to the number of nearshore bars at the locality in question the waves were usually standing alongshore but during an experiment in which a very high energy level prevailed the edge waves were probably progressive the selection of only one or two cut off modes may be the result of an interrelationship between the topographic cut off and offshore wave groups the nearshore region was surveyed following storms it was found that there was generally a good correlation between bar positions and rhythmic dimensions and the theoretical cross shore and longshore structure of the recorded edge waves it is concluded that infragravity waves may be important in the formation migration and morphology of nearshore bars with the number of bars depending on the edge wave mode number

sediment transport and beach morphodynamics induced by free long waves bound long waves and wave groups new laboratory data are presented on the influence of free long waves bound long waves and wave groups on sediment transport in the surf and swash zones as a result of the very significant difficulties in isolating and identifying the morphodynamic influences of long waves and wave groups in field conditions a laboratory study was designed specifically to enable measurements of sediment transport that resolve these influences the evolution of model sand beaches each with the same initial plane slope was measured for a range of wave conditions firstly using monochromatic short waves subsequently the monochromatic conditions were perturbed with free long waves and then substituted with bichromatic wave groups with the same mean energy flux the beach profile changes and net cross shore transport rates were extracted and compared for the different wave conditions with and without long waves and wave groups the experiments include a range of wave conditions e g high energy moderate energy low energy waves which induce both spilling and plunging breakers and different turbulent intensities and the beaches evolve to form classical accretive erosive and intermediate beach states the data clearly demonstrate that free long waves influence surf zone morphodynamics and promote increased onshore sediment transport during accretive conditions and decreased offshore transport under erosive conditions in contrast wave groups which can generate both forced and free long waves generally reduce onshore transport during accretive conditions and increase offshore transport under erosive conditions the influence of the free long waves and wave groups is consistent with the concept of the relative fall velocity h wst as a dominant parameter controlling net beach erosion or accretion free long waves tend to reduce h wst promoting accretion while wave groups tend to increase the effective h wst promoting erosion

intermittent sediment suspension and its implications to sand tracer dispersal in wave dominated environments abstract recent observations of time series of suspended sand concentration in wave dominated environments indicate the occurrence of intermittent near bed suspension the process of intermittent suspension is a significant mechanism resulting in the transport of sand due to waves and currents dyed sand tracer measurements which had previously been interpreted to indicate the dominance of bed load motion are reinterpreted within the context of intermittent suspension by using an order of magnitude stochastic description of suspension and burial events this analysis indicates that tracer burial and dispersal patterns are consistent with the process of intermittent suspension

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

bars bumps and holes models for the generation of complex beach topography in shallow water any two waves of the same frequency are shown to produce complex patterns of drift velocity above the sea bed if the longshore components hi h of the wave numbers of the two waves are different these steady flow patterns exhibit a longshore periodicity of wave number hi h irrespective of whether the waves propagate in the same direction say hi he positive or in opposite directions he negative the interaction of two edge wave modes is examined in detail the drift velocities are calculated and a simple sediment transport model is used to predict the beach topography that would be in equilibrium with these flow patterns as expected crescentic sand bars are produced by the special case of standing edge waves hi h intriguingly for all other cases a combination of complex transverse bars plus meandering or straight offshore bars result patterns that are surprisingly reminiscent of many published descriptions of complex rhythmic topography the extension of the model to three or more waves produces topography that appears to be very irregular although the pattern should repeat over sufficiently long distances along the beach even with only three waves these distances may be very large compared to the scale of the bars