porosity and hydrocarbon distribution in the north sea chalk reservoirs abstract since 1970 more than 25 billion barrels of hydrocarbons in place at reservoir conditions have been discovered in the north sea chalk reservoirs for accurate development drilling satisfactory reserve estimate and optimal recovery a precise description of the porosity and hydrocarbon distribution has proved necessary because such reservoirs were unknown it took some time to fully understand their local and regional variation based on a 12 year experience of the north sea chalks and the data from 180 wells a basic geological model was established and tested on the other fields in the area and is described in this paper thickness variations are due to differential diagenesis as well as depositional factors porosity generally decreases downsection and towards the flank as a result of the progressive invasion of rock by oil and subsequent inhibition of chemical compaction layering in porosity reflects differences in initial porosity hydrocarbon saturation varies with structural elevation and rock type i e depositional facies mineral content differential behaviour to early and late diagenesis pore and pore throat size and morphology tortuosity this report is divided into two parts development of the model and comments on the individual fields

levee morphology and sedimentology along the lower tuross river south eastern australia levees on the lower tuross river in south eastern australia reflect a complex interplay between depositional and erosional processes stream power conditioned primarily by valley width is the key determinant of levee morphology and sedimentology in this confined valley setting three styles of levee are described the rewlee levee is functionally linked to a flood channel in narrow valley settings 250 m these levees contain a diverse facies assemblage characterized by various scales of erosion surfaces vertical accretion on levees has produced conditions under which stream power values exceed the threshold for catastrophic floodplain stripping the levee at the mortfield site is associated with less confined settings valley width 500 600 m which present lower flood stage and stream power conditions this levee hosts a wide range of facies but erosion surfaces are seldom observed in the more open valley setting at the central site valley width 700 1000 m levees comprise uniform fine grained deposits which grade to pronounced distal floodplains with backswamps as levees reflect a combination of within channel and overbank processes both depositional and erosional these geomorphic features influence the character and sedimentology of adjacent landforms and the associated alluvial architecture of the basin

variations in natural levee morphology in anastomosed channel flood plain complexes abstract natural levees are common features of alluvial river systems yet their origin and evolution are poorly understood in this paper we present morphologic and sedimentologic data from two anastomosed rivers and offer a hypothesis of natural levee growth in these systems based on mechanisms of sediment transport in settings where floodbasins fill at the same rate as the channel levees form by turbulent diffusion of suspended sediment away from a high velocity thread into a floodbasin of relatively stagnant water the theory of diffusive transport suggests that these levees should be narrow steep and display abrupt decreases in grain size due to rapid decreases in carrying capacity with distance into the floodbasin in environments where an appreciable water surface slope is maintained between the main channel and the floodbasin levees form by advection of sediment out of the channel and into the floodbasin advective transport theory indicates that these levees should be broad and gently sloped with grain sizes gradually decreasing away from the main channel natural levees occurring in the anastomosed reach of the upper columbia river in se british columbia display significantly different morphology from levees in the cumberland marshes region of the lower saskatchewan river in east central saskatchewan at the upper columbia site the rise in stage of the floodbasin water nearly keeps up with that of the channel water because of good communication between channel and floodbasins through crevasses this inhibits the establishment of a water surface slope and the bulk of the escaping sediment is deposited close to the channel in contrast the cumberland marshes region is characterized by wide and volumetrically large floodbasins these conditions keep floodbasin water surface elevations relatively low and maintain an appreciable elevation head between the channel and its floodbasin fostering levee growth by advective transport

diagenetically enhanced bedding in argillaceous platform limestones stratified cementation and selective compaction a field and petrographic study has been made of 34 massive beds in argillaceous limestones of open marine platform facies in the u k lithologies include grainstones packstones wackestones and lime mudstones the rocks are of silurian carboniferous and jurassic ages additional information was obtained from other limestones in the u k the u s a canada and continental europe the beds are parts of sequences composed of couplets of strata fissile limestones alternating with hard limestones in the fissile limestones the effects of mechanical compaction and pressure dissolution have been concentrated whereas in the hard limestones they are minimal or absent bedding planes visible in outcrop are diagenetic in origin and lie in the middle parts of the fissile limestones where compaction has been most severe the features produced by pressure dissolution are dissolution seams and fitted fabric there are no stylolites the original carbonate sediments were bioturbated and any structures produced by flowing water were destroyed the vertical distribution of the bedding planes bears no relation to primary depositional bedding planes which are rare or absent it is inferred that the strata which were to become the hard limestones were selectively cemented before mechanical compaction had been completed thenceforth mechanical compaction and then pressure dissolution were concentrated in the less cemented strata these became the fissile limestones pressure dissolution acted late in the diagenetic history and provided only an insignificant part if any of the carbonate for cementation it is concluded that the orientation of beds couplets is parallel to successive sea floors and that the sediments that eventually became single beds accumulated synchronously similar couplets in platform limestones of the mississippian and pennsylvanian of the u s a extend over thousands of square kilometres the signal that controlled the initial selective cementation must have been widespread and synchronous and also syndepositional in its timing but otherwise cannot be further defined on the basis of the data so far collected the presumed order of events was 1 accumulation of carbonate sediment terrigenous clay and organic matter 2 hydrodynamic reworking and bioturbation the latter finally overprinting the former 3 selective cementation of the more carbonate rich strata yielding couplets each consisting of a relatively well cemented stratum and a poorly cemented stratum 4 mechanical compaction concentrated in the less cemented strata 5 pressure dissolution concentrated in the same strata

environmental implications of the magnetic record in pleistocene lacustrine sediments of the qaidam basin ne tibetan plateau abstract the application of magnetic proxies in paleoclimate studies has the advantage of fast and non destructive measurement procedures which is an important precondition for obtaining high resolution datasets within a manageable time frame here we demonstrate the advantage of using magnetic proxies for a 940 m long drill core comprising lacustrine sediments from the qaidam basin ne tibetan plateau which was previously dated by magnetostratigraphy and optical stimulated luminescence osl dating comparison of three independent mass specific magnetic susceptibility datasets confirms the horizontal homogeneity of the drill core at scales of several cm 3 the potential linkage of to astronomical forcing is suggested by spectral analysis magnetic grain size and mineralogy dependent parameters were used to evaluate possible scenarios explaining the variation moreover using additional palynological results we demonstrate the correlation of with climatic constraints thereby showing the climate sensitivity of higher and lower values are related to dry and more humid conditions respectively our results lead us to conclude that variations are caused by the interference of two driving mechanisms low temperature oxidation in the catchment area and a changing catchment area in summary this study confirms the informative value of magnetic proxies for detecting paleoenvironmental change in high resolution

sedimentary records of large holocene floods from the middle reaches of the yellow river china slackwater deposits have been used as evidence for the magnitude and frequency of palaeofloods which occurred prior to gauged and historical data sets e g holocene extreme flood reconstruction in north america and australia the slackwater deposits from xiaolangdi reach of the yellow river have been identified and related to floods according to both eyewitness accounts and the analysis of sediments the technique successfully delineated the peak flood level and estimated a discharge of the 1994 ad flood in the yellow river the discrepancy of the estimated discharge was less than 5 compared with the instrumental records when we applied the technique to palaeoflood analysis the highest slackwater deposits and flood indicators from the tributary mouths the low river terraces and the loess platforms and loess alcoves together with radiocarbon dating provided evidence of at least six floods with peak discharges greater than 27 300 m3 s 1 at xiaolangdi section over the last 8500 yr the largest flood in ca 7362 yr b p had an estimated discharge of 42 900 m3 s 1 which is the maximum flood event known in the yellow river the results provide a basis for a determining the floods which were comparable to the most cataclysmic flood during the last 2360 yr in 1843 ad and b estimating the flood magnitude for a 10 000 yr time scale relevant for building xiaolangdi dam one of the largest dams under construction in the world the reconstruction of palaeofloods also provides evidence for a phase between ca 6000 8000 yr b p which was much wetter than today as a result of increased summer precipitation and enhanced pacific monsoon conditions in eastern china

quantitative characterization of carbonate pore systems by digital image analysis a new method of digital image analysis can quantify pore parameters over more than three orders of magnitude from a submicron to a millimeter scale this porosity characterization does not require knowledge of lithology age burial depth or diagenesis of the sample the method is based on digital analyses of images from thin sections at variable magnifications taken under an optical microscope om and under an environmental scanning electron microscope esem the results help explain variations in permeability for carbonate samples with a variety of complex pore structures the analyses however can be done on any thin sections of other rock types the om images provide macroporosity information whereas the esem images yield information on microporosity the boundary between macroporosity and microporosity is defined at a pore area of 500 m2 which translates to a pore length of approximately 20 m which is roughly the thickness of a thin section and thus the resolution of the om the digitized thin section images are binarized into a macropore and a matrix phase om or a micropore and a solid phase esem a standard digital image analysis program is used to detect all individual pores and to measure pore area and pore perimeter based on these analyses one can calculate for each sample the amount of macroporosity the amount of microporosity within the matrix intrinsic microporosity the shapes of the macropores perimeter over area and the pore size distribution comparison of total porosity determined from plugs indicates that macroporosity and microporosity values based on this methodology match the plug data confirming the validity of the method the combination of macroporosity and microporosity data yields pore size distribution and pore shape information that can explain the distribution of physical properties in particular permeability in parameter sensitivity analyses using neural networks permeability appears to be mainly controlled by the macropore shape in high permeability samples and by the amount of intrinsic microporosity in the low permeability samples

advances in borehole imaging technology and applications abstract borehole imaging devices are currently available for both wireline and logging while drilling lwd environments for use in both openhole and cased wells most wireline and all lwd devices provide indirect images that are derived from a high density grid of electrical or ultrasonic acoustic measurements optical techniques such as television and photography provide direct images of the borehole imaging devices consist of 1 a rotating sensor acoustic or electrical that scans the borehole with each revolution 2 multiple azimuthally placed sensors or 3 a downhole television or photographic camera advances in digital acquisition and processing permit real time display and evaluation of images of the open borehole or the inside of casing the resolution and borehole coverage of microelectrode devices has increased with newer designs that allow additional measurement sensors per pad additional pad segments on a four arm tool and the introduction of six arm imaging tools in nonconductive borehole fluids a four arm microinduction device can provide crude images macroelectrode imaging tools laterolog type wireline provide lower resolution electrical images from either an azimuthal arrangement of sensors around a mandrel wireline or from azimuthally sensitive sensors logging while drilling that scan the borehole during rotation of the bottomhole assembly in acoustic imaging recent devices incorporate design changes that provide improved image resolution and operate in a wider range of borehole conditions ultrasonic transducers now use lower transmitting frequencies and spherical focusing and these tools also offer surface selectable acquisition parameters acoustic and microresistivity imaging techniques measure different physical properties and these data are complementary one recently introduced wireline service combines microresistivity and acoustic imaging devices in a single tool for simultaneous single pass acquisition recent advances in cable and sonde design permit downhole video in a wider range of petroleum environments in flowing wells and in tubing openhole image interpretation involves qualitative visual identification and quantitative characterization of strike and dip on planar features lithology bedding fractures and vugs when core is available features identified on log derived images can be correlated or calibrated to it or when core is absent images may serve as a substitute borehole images are useful in formation evaluation when calibrated sedimentology stratigraphy and structural analysis current applications include core orientation reconstructing missing core identification and characterization of fractures and depositional features e g bedforms reservoir architecture bedding grain size porosity permeability net sand and net pay counts faults folds and fractures hydrocarbon water geothermal wells and in rock engineering evaluation of borehole stress borehole stability directional placement of wellbore for optimal drainage fractured reservoirs evaluation of fracture stimulations and perforation control cased hole applications include cement evaluation casing inspection detection of fluid entry identifying production blockages and assisting in fishing operations

rhythmic bedding produced in cretaceous pelagic carbonate environments sensitive recorders of climatic cycles various types of rhythmic bedding are prominent features of cretaceous pelagic carbonates these bedding rhythms are the primary depositional result of variations in carbonate productivity terrigenous dilution redox conditions and or the energy of bottom currents each bedding cycle type is different in its expression in the stratigraphic record but ultimately was caused by rhythmic climatic variations related to variations in receipt of solar insolation as the result of the earth s orbital characteristics the so called milankovitch cycles stratigraphic sequences may contain a single bedding cycle type or a composite of several types although sediment type and sedimentary structures were influenced by variations in local climatic oceanographic tectonic and diagenetic parameters pelagic carbonate environments during the cretaceous were particularly sensitive recorders of orbitally induced changes in worldwide climate

lower rhine historical flood magnitudes of the last 450years reproduced from grain size measurements of flood deposits using end member modelling abstract objective the objective of this research was to unlock the potential of fluvial archives to create flood chronologies based on grain size characteristics of flood deposits located in two recently formed fluvio lacustrine sequences methods grain size data was compared with contemporaneous discharge measurements for the lower rhine the netherlands regression relations between coarse tail grain size parameters and measured discharge were established for the last 240 years and applied to the older parts of both cores resulting in peak discharge estimates back to ad 1550 results grain size descriptive parameters such as the 95th percentile and end member modelling outcomes correlate well with discharge and turn out to be sensitive proxies for inferring flood magnitudes locally geomorphological changes influence the relation between peak discharge magnitudes and flood bed coarseness but these can be assessed using continuous flood layer and background sedimentation measurements to standardize grain size descriptive parameters conclusion implications flood records distilled from sedimentary archives hold great potential for extending existing records of observed discharge and aid establishment of design discharge for flood protection measures and assessment of non stationarity of the flooding regime due to climatic and anthropogenic forcing

microbial mediated pre salt carbonate deposition during the messinian salinity crisis calcare di base fm southern italy abstract a multi scale analysis of sedimentary carbonate facies and post sedimentary diagenetic features of the calcare di base formation the precursor to evaporites in upper messinian successions of northern calabria and central sicily has revealed their microbial bio mediated origin massive to laminated microbial boundstones represent the most common sedimentary facies forming flat to low relief cm to m scale stromatolitic and thrombolitic bodies the fabric of the micrite varies from peloidal to aphanitic and almost always preserves filamentous bacteria which characterized the original microbial mat the mat was dominated by sulphur oxidizing bacteria belonging to the thiotrichaceae but there is evidence for a more complex community with sulphate and or nitrate reducing bacteria all being responsible for the mediation of the carbonate precipitation microbial boundstones are rich in pseudomorphs of ca sulphate and halite which formed during the deposition of the microbial carbonate layers of primary gypsum are interbedded locally with carbonates suggesting the presence of restricted marine conditions the stable o and c isotopic composition of the carbonates that vary from dolomite to aragonite and calcite suggests a complex interplay between arid to humid climatic changes expressed cyclic interbedding of the carbonate with marl marlstone later diagenetic events mainly consist of phreatic meteoric recrystallization and cementation although considered as diachronous the microbial carbonates can be mapped out over a distance of more than 500 km across southern italy this indicates near constant environmental conditions upon the central mediterranean shelf at the beginning of the salinity crisis deposition of the extensive subaqueous microbial deposit that largely comprises the calcare di base is envisaged to have taken place across a shallow to moderate depth platform with local slopes into deeper water areas where some resedimentation occurred

floodplain sedimentation in the upper mississippi valley natural versus human accelerated abstract understanding the time scales and pathways for response and recovery of rivers and floodplains to episodic changes in erosion and sedimentation has been a long standing issue in fluvial geomorphology floodplains are an important component of watershed systems because they affect downstream storage and delivery of overbank flood waters and they also serve as sources and temporary sinks for sediments and toxic substances delivered by river systems here 14c and 137cs isotopic dating methods are used along with ages of culturally related phenomena associated with mining and agriculture to determine rates of sedimentation and morphologic change for a reach of the upper mississippi river and adjacent tributaries in southwestern wisconsin and northwestern illinois the most important environmental change that influenced fluvial activity in this region during last 10 000 years involved the conversion of a late holocene mosaic of prairie and forest to a landscape dominated by cropland and pastureland associated with euro american settlement results presented herein for the upper mississippi valley umv show that the shift from pre agriculture natural land cover to landscape dominance by agricultural land use of the last 175 200 years typically increased rates and magnitudes of floodplain sedimentation by at least an order of magnitude accelerated overbank flooding led to increased bank heights on tributary streams and in turn contributed to more frequent deep flows of high energy these high energy flows subsequently promoted bank erosion and lateral channel migration and the formation of a historical meander belt whose alluvial surface constitutes a new historical floodplain inset against the earlier historical floodplain the new historical floodplain serves as a flume like channel that provides efficient downstream transport of water and sediment associated with moderate and large magnitude floods floodplains on lower tributaries however continue to experience rates of overbank sedimentation that are of anomalously high magnitude given improved land cover and land conservation since about 1950 this lower valley anomaly is explained by minimal development of historical agriculture period meander belts because of relatively low stream power in these channel and floodplain reaches of relatively low gradient in general long term pre agriculture rates of vertical accretion between about 10 000 and 200 years ago averaged about 0 2 mm yr 1 in tributary watersheds smaller than about 700 km2 and about 0 9 mm yr 1 on the floodplain of the upper mississippi river where the contributing watershed area increases to about 170 000 km2 on the other hand rates of historical vertical accretion during the period of agricultural dominance of the last 200 years average between 2 and 20 mm yr 1 with short episodes of even higher rates during times of particularly poor land conservation practices significant hydrologic effects of mining and agricultural started by the 1820s and became widespread in the study region by the mid 19th century the hydrologic and geomorphic influences of mining were relatively minor compared to those related to agriculture high resolution dating of floodplain vertical accretion deposits shows that large floods have frequently provided major increments of sedimentation on floodplains of tributaries and the main valley upper mississippi river the relative importance of large floods as contributors to floodplain vertical accretion is noteworthy because global atmospheric circulation models indicate that the main channel upper mississippi river should experience increased frequencies of extreme hydrologic events including large floods with anticipated continued global warming instrumental and stratigraphic records show that coincident with global warming a shift to more frequent large floods occurred since 1950 on the upper mississippi river and these floods generally contributed high magnitudes of floodplain sedimentation

cretaceous rhythmic bedding sequences a plausible link between orbital variations and climate abstract simple oscillation cycles have been recognized in cretaceous pelagic sequences as a marked periodicity in carbonate and or organic carbon content the estimated periodicities of these cycles resemble milankovitch type variations in orbital elements however during warm geologic periods the nature of the link between orbital variations and the sedimentary record has been problematic climate model studies show that the intensity of continental margin precipitation in specific low latitude regions is a function of land sea thermal contrast which is sensitive to orbital variations cretaceous climate model simulations are characterized by regions of intense precipitation the locations of which are controlled by geographic configuration in particular in the model simulation the northern margin of the tethys ocean has all the climatic characteristics necessary to exhibit a sensitivity to orbital variations detailed studies of the biota sedimentology and geochemistry of the bedding rhythms in greenhorn cyclothem in the western interior seaway of north america are best interpreted in terms of variations in precipitation runoff and stable stratification of the seaway combined the geologic and model studies support a link between orbital periodicities variations of intense precipitation associated with specific paleogeographic situations and cretaceous bedding patterns this hypothesis has important implications for the sensitivity of the atmosphere hydrosphere lithosphere system to external forcing

development of a papua new guinean onshore carbonate reservoir a comparative borehole image fmi and petrographic evaluation abstract the depositional and diagenetic controls on carbonate platform evolution are notoriously heterogeneous and difficult to determine from standard subsurface wireline logging techniques here a combined borehole image fmi fullbore formation microimager and petrographic study allowed evaluation of depositional and diagenetic trends across an australasian subsurface buildup that is a major recent gas discovery the elk and antelope gas fields are hosted in tertiary reefal platformal and associated deep water carbonates in the present day foothills region of the fold and thrust belt in the gulf province of papua new guinea a full suite of fmi logs 2800 m and 292 thin sections mainly from sidewall cores and cuttings from both platform flank and shallow water deposits were evaluated during this study despite the obvious scale differences between the datasets there was some correlation between the independent petrography and fmi studies for a picking major facies boundaries and b interpretation of depositional environments the latter particularly for slope and deep water deposits however thin section petrography proved critical in understanding primary depositional textures and secondary alteration features through the shallow water carbonates where complex diagenetic overprinting had strongly impacted original fabric and or in regions affected by gas smearing the petrographic study allowed more detailed examination of diagenesis and its impact on rock fabric which links to the fmi textures component analysis and depositional textures identified in thin section are good indicators of original depositional environment full fmi coverage allowed textural definition on a dm m scale identification and characterisation of vertical changes and likely large scale variations in depositional environments and sequences it was clear from combining the results of the two studies that diagenesis as well as depositional fabric had a strong impact on resultant fmi facies the diagenetic overprinting would have been difficult to extract from the fmi data without the benefit of the petrographic work this study shows the merits of selective petrographic analysis to calibrate the quality of facies interpretation from fmi images and proved critical for enhancing and in places revising initial fmi interpretations

stylolite controlled layering in an homogeneous limestone pseudo bedding produced by burial diagenesis it is often assumed that layering in many shelf and platform limestones at weathered outcrop is always bedding the layers always beds and the surfaces always bedding planes recognition of bedding is fundamental to facies and basin analysis examination of part of the lower carboniferous high tor limestone of the gower south wales shows that a totally diagenetic layering pseudo bedding resembling and parallel to primary depositional layering true bedding has been produced by the generation of parallel more or less evenly spaced stylolite surfaces during burial diagenesis these stylolite surfaces are picked out by weathering at outcrop and resemble bedding planes evidence that the stylolite surfaces do not mark original bedding planes includes a cross cutting relationship of a stylolite surface to a primary bedding surface lack of lithological change across or sedimentary structures associated with a stylolite surface original bedding that is not coincident with stylolite surfaces and has not suffered pressure dissolution and lack of sedimentological evidence that the layers defined by the stylolite surfaces are true primary depositional beds the generation of parallel and more or less evenly spaced stylolite surfaces could be explained by a mathematical kinetic model based on the relationship between pressure dissolution diffusion and reprecipitation recognition of true bedding depends upon presence of lithological changes and or sedimentary structures it is suggested that pseudo bedding could be confused with true bedding in some open platform shelf lagoon facies where lithological changes or sedimentary structures are scarce or absent

muddled or mixed inferring palaeoclimate from size distributions of deep sea clastics abstract one of the outstanding problems of palaeoclimate reconstruction from physico chemical properties of terrigenous deep sea sediments stems from the fact that most basin fills are mixtures of sediment populations derived from different sources and transported to the site of deposition by different mechanisms conventional approaches to palaeoclimate reconstruction from deep sea sediments do not distinguish between provenance and dispersal related variations and therefore often fail to recognise the true significance of variations in sediment properties we formulate a set of requirements that each proposed palaeo environmental indicator should fulfil and focus on the intrinsic coupling between grain size and chemical composition a critical review of past achievements in grain size analysis serves to introduce a conceptual model of spatio temporal grain size variation based on dynamic populations each dynamic population results from a characteristic combination of production and transport mechanisms that corresponds to a distinct subpopulation in the data analysed the mathematical statistical representation of the conceptual model can be obtained by means of the end member modelling algorithm emma applications of the model to several ocean basins are discussed as well as methods to examine the validity of grain size based palaeoclimate reconstructions palaeoclimate reconstructions of a high and low latitude basin illustrate the common degree of complexity of deep sea grain size records

spatial variation of overbank aggradation rate and its influence on avulsion frequency river avulsions are commonly considered to be driven by the aggradation and growth of alluvial ridges and the associated increase in cross valley slope relative to either the down channel slope or the down valley slope the latter is termed the slope ratio in the present paper therefore spatial patterns of overbank aggradation rate over stratigraphically relevant time scales are critical in avulsion dominated models of alluvial architecture detailed evidence on centennial to millennial scale floodplain deposition has to date been largely unavailable new data on such long term overbank aggradation rates from the rhine meuse and mississippi deltas demonstrate that the rate of decrease of overbank deposition away from the channel belt is much larger than has been supposed hitherto and can be similar to observations for single overbank floods this leads to more rapid growth of alluvial ridges and more rapid increase in slope ratios potentially resulting in increased avulsion frequencies a revised input parameter for overbank aggradation rate was used in a three dimensional model of alluvial architecture to study its effect on avulsion frequency realistic patterns of avulsion and interavulsion periods 1000 years were simulated with input data from the holocene rhine river with avulsions occurring when the slope ratio is in the range 3 5 however caution should be practised with respect to uncritical use of these numbers in different settings evidence from the two study areas suggests that the avulsion threshold cannot be represented by one single value irrespective of whether critical slope ratios are used as in the present study or superelevation as has been proposed by other investigators

paleoflooding reconstruction from holocene levee deposits in the lower meuse valley the netherlands this study investigates the holocene levee deposits and paleoflooding history of the lower meuse in the netherlands based on archeological investigations and sedimentary analyses grain size end member modelling magnetic susceptibility and thermogravimetric analyses the levee on the left bank in the study area near ooijen contains a continuous sedimentary record in the nw downstream part the archeological evidence and sedimentary results including a grain size based flood energy index lfei indicate that the lower meuse experienced a quiescent flooding period and low sedimentation rates during the mid late mesolithic when the levee was low and human influence was minor deposition during the mesolithic shows a fining upward trend and a highly developed soil containing abundant artefacts during the neolithic and bronze age the flooding intensity was low but gradually increased to a moderate level probably because of deforestation and increased runoff limited bronze age findings may reflect decreased human activity because of the increased flooding starting from the iron age the meuse experienced a generally enhanced flooding regime which is reflected by erosion and coarsened sedimentation in the iron age and roman period the high peak discharges during the iron age may have re opened a low lying paleochannel near to the levee during the intensified floods this general increasing trend is interrupted by the lower flooding phase in the early middle ages dark ages from the middle to the late middle ages the floods intensified again the coarsening deposition and higher sedimentation rates since the iron age resulted from increased floods and higher sediment supply by deforestation and soil erosion the findings of this study agree with a recent paleoflood reconstruction for the lower meuse by using a floodplain archive implying that levee sediment records have potential in paleohydrological studies if the completeness of the record and chronological information is guaranteed 2019 elsevier b v

an integrated and quantitative approach to petrophysical heterogeneity exploration in anything but the simplest of reservoirs is commonly more challenging because of the intrinsic variability in rock properties and geological characteristics that occur at all scales of observation and measurement this variability which often leads to a degree of unpredictability is commonly referred to as heterogeneity but rarely is this term defined although it is widely stated that heterogeneities are poorly understood researchers have started to investigate the quantification of various heterogeneities and the concept of heterogeneity as a scale dependent descriptor in reservoir characterization based on a comprehensive literature review we define heterogeneity as the variability of an individual or combination of properties within a specified space and or time and at a specified scale when investigating variability the type of heterogeneity should be defined in terms of grain e pore components and the presence or absence of any dominant features including sedimentological characteristics and fractures hierarchies of geologic heterogeneity can be used alongside an understanding of measurement principles and volumes of investigation to ensure we understand the variability in a dataset basic statistics can be used to characterise variability in a dataset in terms of the amplitude and frequency of variations present a better approach involves heterogeneity measures since these can provide a single value for quantifying the variability and provide the ability to compare this variability between different datasets tools measurements and reservoirs we use synthetic and subsurface datasets to investigate the application of the lorenz coefficient dykstraeparsons coefficient and the coefficient of variation to petrophysical data e testing assumptions and refining classifications of heterogeneity based on these measures 2015 the authors published by elsevier ltd this is an open access article under the cc by license