pore characterization of isolated organic matter from high matured gas shale reservoir abstract knowledge of pore structure of isolated organic matter om provides guidance for better understanding the origin distribution and characterization of pore system in gas shale reservoir and can be used to better comprehend the storage and transport mechanism of natural gas in shale reservoir pore structure characteristics of isolated organic matters and its corresponding bulk shales were investigated for five high matured marine shale samples from the lower silurian longmaxi formation in south china using x ray diffraction xrd total organic carbon content toc tests field emission scanning electron microscope fe sem observation and ultra low pressure nitrogen gas physisorption the results indicate that om hosted pores are abundant in bulk shale samples under fe sem observation the bet surface area and the bjh pore volume of isolated om are approximately three times greater than that of bulk shale samples pore size distribution psd of isolated om from five shale samples show a consistent variation pattern additionally with increasing toc content the psd curves of isolated om gradually grow down as result of the ductility of om bimodal psd in surface area and unimodal psd in pore volume exist in both isolated om and bulk shale samples indicating surface area is mainly associated with micropores and fine mesopores

the role of earthquakes in inducing sediment mass movements in the eastern korinthiakos gulf an example from the february 24 march 4 1981 activity abstract korinthiakos gulf is a narrow arm of the sea connecting the ionian and the aegean seas through the rion antirion strait and the korinth canal respectively the eastern part of korinthiakos was surveyed by the marine geology department of the institute of geology and mineral exploration of greece using a 3 5 khz subbottom profiler the survey was carried out a short time after intensive earthquake activity which occurred in the area from february 24 to march 4 1981 during this activity three major shocks of magnitudes ranging from 6 4 to 6 7 took place the subbottom profiles reveal a sediment mass which was deposited by submarine slumping in the alkyonides basin which lies at the eastern end of the studied area the slump is about 10 km long 1 5 to 2 0 km wide and its areal extent is about 16 km2 the scarp area occurs at a bathymetric depth of about 100 to 250 m in the northeastern part of the basin the scarp faces are from 10 to 15 m high and have a total areal extent of about 4 km2 the destruction of fishing nets of trawling boats and other evidence indicates that the triggering of the mass flow was effected by the earthquake activity and probably by the first major shock scarp areas and scarp faces from which sediment masses have been removed were detected in other shallow and deep sectors of the studied area indicating that mass transport processes are very common in this area of high seismicity

spectrum of pore types and networks in mudrocks and a descriptive classification for matrix related mudrock pores matrix related pore networks in mudrocks are composed of nanometer to micrometer size pores in shale gas systems these pores along with natural fractures form the flow path permeability network that allows flow of gas from the mudrock to induced fractures during production a pore classification consisting of three major matrix related pore types is presented that can be used to quantify matrix related pores and relate them to pore networks two pore types are associated with the mineral matrix the third pore type is associated with organic matter om fracture pores are not controlled by individual matrix particles and are not part of this classification pores associated with mineral particles can be subdivided into interparticle interp pores that are found between particles and crystals and intraparticle intrap pores that are located within particles organic matter pores are intrap pores located within om interparticle mineral pores have a higher probability of being part of an effective pore network than intrap mineral pores because they are more likely to be interconnected although they are intrap om pores are also likely to be part of an interconnected network because of the interconnectivity of om particles in unlithifed near surface muds pores consist of interp and intrap pores and as the muds are buried they compact and lithify during the compaction process a large number of interp and intrap pores are destroyed especially in ductile grain rich muds compaction can decrease the pore volume up to 88 by several kilometers of burial at the onset of hydrocarbon thermal maturation om pores are created in kerogen at depth dissolution of chemically unstable particles can create additional moldic intrap pores

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

sedimentary processes on the atlantic continental slope of the united states abstract until recently the sedimentary processes on the united states atlantic continental slope were inferred mainly from descriptive studies based on the bathymetry and on widely spaced grab samples bottom photographs and seismic reflection profiles over the past 6 years however much additional information has been collected on the bottom morphology characteristics of shallow subbottom strata velocity of bottom currents and transport of suspended and bottom sediments a review of these new data provides a much clearer understanding of the kinds and relative importance of gravitational and hydrodynamic processes that affect the surface sediments on the rugged slope between georges bank and cape lookout n c these processes include 1 small scale mass wasting within submarine canyons and peripheral gullies 2 density flows within some submarine valleys 3 sand spillover near the shelf break 4 sediment creep on the upper slope and 5 hemipelagic sedimentation on the middle and lower slope the area between georges bank and hudson canyon is further distinguished by the relative abundance of large scale slump scars and deposits on the open slope the presence of ice rafted debris and the transport of sand within the heads of some submarine canyons between cape lookout and southern florida the slope divides into two physiographic units and the topography is smooth and featureless on the florida hatteras slope offshelf sand spillover and sediment winnowing related to gulf stream flow and possibly to storm driven currents are the major processes whereas hemipelagic sedimentation is dominant over the offshore slope along the seaward edge of the blake plateau north of the blake spur slumping generally is absent south of cape lookout although one large slump scarp related to uplift over salt diapirs has been identified east of cape romain future studies concerning sedimentary processes on the atlantic slope need to resolve 1 the ages and mechanisms of mass wasting 2 the accumulation rates and thicknesses of hemipelagic sediments and 3 the causes and variability of offshelf sand spillover sediment winnowing and canyon transport

processes and rates of recent holocene basin filling in an active transform margin santa monica basin california continental borderland abstract santa monica basin an inner basin of the california continental borderland is a deep margin basin presently receiving sediments under high sea level conditions since the slowing of the last transgression the basin has been receiving primarily suspended load contributions with rare turbidites except in the most headward parts of the two principal canyons one turbidite found throughout the basin was laid down about 200 years bp and was probably deposited by a turbidity current generated by mass movement of slope sediments in the slope apron adjacent to the major active canyons similar basin wide events have occurred throughout holocene time at intervals of about 500 1000 years and these represent the effects of big earthquakes major floods or other exceptional happenings not commonly recorded in historic time except for these exceptional events the basin has received fine clastic sedimentation derived from the mainland rivers and transported by nepheloid plumes near bottom and in the surface mixed layer biogenic carbonate and organic carbon input from areas of high productivity fed by upwelling is masked by the fine detrital influx over the major fans by dilution from the rain of particulates from the major surface and near bottom turbid plumes that pass over the basin center a maxima of carbonate and organic content occurs in the basin floor sediments most distant from the combined diluting effects of these two major detrital inputs the basin slope fan and shelf bank top sediments are differentiated on the basis of mean particle size and skewness changes in sand and silt content are related to the pattern of the prevailing surface and near bottom water circulation with their reservoirs of fine suspended particulates the principal process removing the fine particles from the surface plumes is biological filtering and pelleting sedimentation rates of major sediment components show that near bottom nepheloid plumes are trapped by the closed deep basin and their load settles out as the turbid waters circle over the central basin floor sedimentation rates vary from 40 80 cm 1000 years average sediment delivery is about 106 tons but exceptional floods can deliver several fold more sediment at 10 30 year intervals

simulated thermal maturation of type i and iii kerogens in the presence and absence of calcite and montmorillonite abstract the effects of a mineral matrix on hydrocarbon generation from different types of kerogen were examined simulated thermal maturation of type i iii a and iii b kerogens alone and mixed with minerals was investigated using anhydrous pyrolysis both calcite and montmorillonite modified the products of simulated thermal maturation of the kerogens montmorillonite slightly reduced and calcite slightly enhanced the formation of oil like products from the coals type iii a and iii b kerogens at higher levels of maturation however the catalytic effect of calcite resulted in cracking of the pyrolysates for retention of the pyrolysis products of type i kerogen montmorillonite proved to be a very active matrix whereas the products were less affected by calcite the amount of soluble bitumen extracted from heated type i kerogen was higher in the presence of minerals than in their absence on the contrary the amount of soluble bitumen obtained from heated type iii a kerogen was smaller in the presence of minerals in the case of type iii b kerogens this effect of minerals changed as a function of the temperature of simulated thermal maturation

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

pore structure and spontaneous imbibition characteristics of marine and continental shales in china the pore structure of shale has a significant effect on hydrocarbon migration and the long term gas supply of shale gas wells the present study investigates the spontaneous imbibition characteristics to evaluate the pore connectivity and wettability of marine longmaxi shale samples from the southeastern chongqing area and continental yanchang shale samples from the ordos basin the pore size distribution obtained from n2 adsorption and mercury intrusion porosimetry field emission scanning electron microscopy and focused ion beam scanning electron microscopy photos are used to interpret the imbibition behaviors our results show that the difference in dominant pore type between marine and continental samples which is dominated by thermal maturity controls on their imbibition behaviors as well as their wettability organic matter om pores within yanchang samples are poorly developed because of their low thermal maturity and a large amount of water wet inorganic pores are preserved in these samples because of relatively weak compaction oil wet om pores are well developed in longmaxi samples with higher thermal maturity and inorganic pores have been largely eliminated because of strong compaction the low pore connectivity to water for both the longmaxi and yanchang samples is indicated by the low water imbibition slopes furthermore the more oil wet property of the longmaxi samples and more water wet characteristics of the yanchang samples are obtained by comparing the directional water oil imbibition slopes in addition the positive meaning of quartz in the protection of pore spaces is found in both the longmaxi and the yanchang samples used in this study

seismic stratigraphy of the fault controlled submarine canyon valley system on the shelf and upper slope of anamur bay northeastern mediterranean sea abstract high resolution shallow seismic reflection uniboom and echosounding profiles obtained on the shelf and upper slope areas of anamur bay turkey northeastern mediterranean were studied together with previous data on the onshore geology of the area to investigate the origin and related seismic stratigraphy of the submarine anamur canyon it was found that the main axial trend of the submarine anamur canyon is aligned with the offshore projection of the n s orientated onshore anamur thrust fault of late cretaceous senonian to early tertiary age interpretation of the distinct reflection configurations observed on the seismic profiles reveals the presence of various seismic facies comparable with the depositional sequences resulting from the relative sea level changes during the late quaternary the acoustic basement probably miocene in age is overlain by a sedimentary column mainly plio quaternary which in turn can be divided into two major seismic sequences and 12 seismic facies that show considerable variations in both their lateral and horizontal extent a palaeo deltaic environment sequence i with its typical topset and foreset facies was recognized and the corresponding deposits are interpreted to be indications of coastal deltaic progradation during late pleistocene sea level highstands or during the early phases of the last major eustatic lowering reflections of sequence ii which includes nine distinct facies are marked by onlap configuration and are believed to be marine deposits of the flandrian transgression at least four transgressive cycles are evident from the seismic profiles at 70 90 60 45 and 40 m water depths the two sequences i and ii are now covered with the most recent facies

sedimentology of rift climax deep water systems lower rudeis formation hammam faraun fault block suez rift egypt abstract in most marine rift basins subsidence outpaces sedimentation during rift climax times typically this results in sediment starved hangingwall depocentres dominated by deep marine mudstones with subordinate local development of coarser clastics in the immediate hangingwall derived from restricted catchments on the immediate footwall scarp to highlight the spatial variability of rift climax facies and the controls upon them we have investigated the detailed three dimensional geometry and facies relationships of the extremely well exposed miocene rift climax lower rudeis formation in the immediate hangingwall to the thal fault zone suez rift egypt detailed sedimentological analyses allows the lower rudeis formation to be divided into two contemporaneous depositional systems 1 a laterally continuous slope system comprising hangingwall restricted interpretation of individual facies facies relationships and their spatial variability indicate that deposition in the immediate hangingwall to the thal fault occurred via a range of submarine concentrated density flows surge like turbidity flows mass wasting and hemipelagic processes major controls on the spatial variability and stratigraphic architecture of the depositional systems identified reflect the influence of the steep footwall physiography accommodation and drainage evolution associated with the growth of the thal fault the under filled nature of the hangingwall depocentre combined with the steep footwall gradient result in a steep fault controlled basin margin characterised by either slope bypass or erosion with limited coastal plain or shelf area sediment supply to the slope apron deposits is controlled in part by the evolution and size of small footwall drainage catchments in contrast the localized submarine fan is interpreted to have been fed by a larger antecedent drainage network the structural style of the immediate footwall is also believed to exert a control on facies development and stratigraphic evolution in particular fault scarp degradation is enhanced by fault propagation folding which creates basinward dipping bedding planes in the pre rift footwall strata that large pre rift blocks slide on

evolution of veatch washington and norfolk submarine canyons inferences from strata and morphology abstract investigations of veatch washington and norfolk submarine canyons on the eastern continental margin of the united states resulted in a detailed assessment of their past and present geologic processes norfolk and washington canyons share such characteristics as similar levee geometry stratigraphy and mineralogy veatch canyon differs from norfolk and washington canyons in these respects seismic reflection profiles of all three submarine canyon heads indicate an erosional origin seismic profiles of veatch canyon s lower continental slope indicate a formation by depositional processes in contrast the continental slope profiles of washington and norfolk canyons reveal a history of alternating episodes of deposition and erosion cored sediments from washington and norfolk canyons disclose recent intermittent down canyon transport of sand to the continental rise bathymetric and seismic profiles suggest veatch washington and norfolk canyons have all been subjected to a minimum of two periods of development similar axial trends of washington and norfolk canyons imply a common structural influence

the structures stratigraphy and evolution of the gulf of corinth rift greece summary a multichannel seismic and bathymetry survey of the central and eastern gulf of corinth goc greece reveals the offshore fault geometry seismic stratigraphy and basin evolution of one of earths most active continental rift systems active right stepping en echelon north dipping border faults trend ese along the southern gulf margin significantly overlapping along strike the basement offsets of three akrata derveni sithas and xylocastro are linked the faults are biplanar to listric typically intermediate angle 35 in the centre and 45 48 in the east near the surface but decreasing in dip and or intersecting a low or shallow angle 15 20 in the centre and 19 30 in the east curvi planar reflector in the basement major s dipping border faults were active along the northern margin of the central gulf early in the rift history and remain active in the western gulf and in the subsidiary gulf of lechaio but unlike the southern border faults are without major footwall uplift much of the eastern rift has a classic half graben architecture whereas the central rift has a more symmetric w or u shape the narrower and shallower western gulf that transects the 40 km thick crust of the hellenides is associated with a wider distribution of overlapping high angle normal faults that were formerly active on the peloponnesus peninsula the easternmost sector includes the subsidiary gulfs of lechaio and alkyonides with major faults and basement structures trending ne e w and nw the basement faults that control the rift architecture formed early in the rift history with little evidence other than the vrachonisida fault along the northern margin in the marine data for plan view evolution by subsequent fault linkage several have maximum offsets near one end crestal collapse graben formed where the hanging wall has pulled off the steeper onto the shallower downdip segment of the derveni fault the dominant strikes of the corinth rift faults gradually rotate from 090 120 in the basement and early rift to 090 100 in the latest rift reflecting a 10 rotation of the opening direction to the 005 presently measured by gps the sediments include a locally 1 5 km thick early rift section and a late rift section also locally 1 5 km thick that we subdivide into three sequences and correlate with seven 100 ka glacio eustatic cycles the gulf depocentre has deepened through time currently 700 mbsl as subsidence has outpaced sedimentation we measure the minimum total horizontal extension across the central and eastern gulf as varying along strike between 4 and 10 km and estimate full values of 6 11 km the rift evolution is strongly influenced by the inherited basement fabric the regional nnw structural fabric of the hellenic nappes changes orientation to ese in the parnassos terrane facilitating the focused north south extension observed offshore there the basement penetrating faults lose seismic reflectivity above the 4 14 km deep seismogenic zone multiple generations and dips of normal faults some cross cutting accommodate extension beneath the goc including low angle 15 20 interfaces in the basement nappes the thermally cool forearc setting and cross orogen structures unaccompanied by magmatism make this rift a poor analogue and unlikely precursor for metamorphic core complex formation

sequence stratigraphy in active extensional basins implications for the interpretation of ancient basin fills abstract systematic variations in sequences their component units and their stacking patterns exist within rift basins these variations can be related to displacement gradients associated with the large scale 12 50 km segmentation of normal fault zones which control accommodation sediment supply and basin physiography sediment supply is also strongly influenced by the nature of pre rift drainage networks and variations in bedrock lithology high rates of hangingwall subsidence close to the centre of normal fault segments may cancel out the effects of glacio eustatic sea level fall so that accommodation development is normally characterized by the continual addition of new space the resulting sequences lack type 1 sequence boundaries and lowstand systems tracts and stack into aggradational sequence sets the adjacent footwall is subject to uplift which may lead to subaerial exposure and incision generating a composite type 1 sequence boundary away from the fault zone and near segment boundaries slip rates are much lower and hence relative sea level change is dominated by eustasy here falls in relative sea level are important resulting in type 1 sequences sequence stacking patterns reflect not only eustasy and local fault controlled subsidence but also the interaction of these with adjacent uplifting footwalls and or regional uplift tectonic influence on sequence development will be more pronounced during greenhouse times than icehouse times

architecture and depositional sequences of tertiary fault block carbonate platforms an analysis from outcrop miocene gulf of suez and computer modelling abstract this study combines outcrop with seismic data and tectonostratigraphic modelling to characterise the stratigraphy of tertiary fault block carbonate platforms seismic sections from the middle east and southeast asia indicate that carbonate platforms commonly develop on fault blocks in the late syn rift to post rift stage of basin evolution they are characterised by retrogradational or drowning morphologies with deep water clastics evaporites sealing the platforms a new tectono stratigraphic modelling program simulates the development of carbonate platforms on domino style fault blocks and predicts a distinctive tectonic control on the evolving syn rift stratigraphy detailed field work from a three dimensionally exposed miocene syn rift platform from the gulf of suez gebel abu shaar egypt shows the existence of unconformity bound depositional sequences which are predicted by the program and are interpreted to have formed in response to fault block rotation the sequences are characterised by synchronous hangingwall subsidence and footwall uplift and erosion the seismic images the modelling and the outcrop study provide different levels of information on fault block platforms and their characteristic stratigraphy the scale of the modelling is of particular value as it provides a link between the seismic scale imaging and outcrop data

depositional processes of uniform mud deposits unifites hedberg basin northwest gulf of mexico new perspectives structureless mud deposits unifites are a common depositional phenomenon in the intraslope basins of the continental slope of the northwest gulf of mexico high resolution acoustic data and long sediment cores from hedberg basin middle slope were used to provide a better insight into the origin of these enigmatic depositional units the unifite occurring in hedberg basin is structureless under visual observations but x ray radiographs reveal that it consists of three divisions 1 u1 division representing waning sequences of fine grained mud turbidites 2 u2 division characterized by faint normally graded mud layers with occasionally wispy silty interlaminae and 3 u3 division characterized by a uniform appearance with no obvious sedimentological structures other than a faint banding of slightly siltier and slightly more clayey layers high resolution geophysical data reveal that there is no connection between intrabasinal sediment failures and the occurrence of unifites we suggest that unifites have resulted from the deposition of a long lasting 1 53 months pulsating showing internal surges fine grained turbidity current dated at 28 629 ka that originated from the flow transformation of a series of massive sediment failures on the shelf edge and or upper continental slope the fine grained nature of the turbidity current is probably caused by the depositional segregation of the flow by depositing its coarsest material in intraslope basins in more proximal locations we propose that the uniform texture of the unifite is attributed to the development of a stratification interface lower stratified layer generated by the continuous introduction of a turbulent sediment cloud in the intraslope basins the lowest two unifite divisions are considered to develop prior to and during the development of the stratified layer

impact of rock fabric on water imbibition and salt diffusion in gas shales abstract understanding water uptake of gas shales is critical for designing fracturing and treatment fluids previous imbibition experiments on unconfined gas shales have led to several key observations the water uptake of dry shales is higher than their oil uptake furthermore water imbibition results in sample expansion and microfracture induction this study provides additional experimental data to understand the effects of rock fabric complex pore network clay swelling and osmotic potential on imbibition behavior we systematically measure and compare the imbibition rates of deionized water and oil into wet dry and confined unconfined rock samples from different shale members of the horn river basin we also measure the ion diffusion rate from shale into water during imbibition experiments the results show that initial water saturation decreases the water uptake of shale samples however it has no effect on oil imbibition rates the liquid imbibition and ion diffusion rates along the lamination are higher than those against the lamination the results also suggest that confining the shale samples decreases the water imbibition rate parallel to the lamination however it has a negligible effect on water uptake perpendicular to the lamination furthermore confining does not significantly affect the ion diffusion rates the comparative study suggests that for both confined and unconfined samples water uptake is higher than oil uptake however previous experiments on crushed shale samples show that the oil uptake of crushed packs is higher than their water uptake xu and dehghanpour 2014 the data suggest that the connected pore network of the intact samples is water wet while the majority of rock including poorly connected pores is oil wet this argument is backed by bse images and complete spreading of oil on fresh break surfaces of the rock

the role of minerals in the thermal alteration of organic matter iii generation of bitumen in laboratory experiments abstract a series of pyrolysis experiments utilizing two different immature kerogens from the monterey and green river formations mixed with common sedimentary minerals calcite illite or namontmorillonite was conducted to study the impact of the mineral matrix on the bitumen that was generated calcite has no significant influence on the thermal evolution of bitumen and also shows virtually no adsorption capacity for any of the pyrolysate in contrast montmorillonite and illite to a lesser extent alter bitumen during dry pyrolysis montmorillonite and illite also display strong adsorption capacities for the polar constituents of bitumen by this process hydrocarbons are substantially concentrated within the pyrolysate that is not strongly adsorbed on the clay matrices the effects of the clay minerals are significantly reduced during hydrous pyrolysis the strong adsorption capacities of montmorillonite and illite as well as their thermocatalytic properties may in part explain why light oils and gases are generated from certain argillaceous source rock assemblages whereas heavy immature oils are often derived from carbonate source rocks

organic matter hosted pore system marcellus formation devonian pennsylvania the marcellus formation of pennsylvania represents an outstanding example of an organic matter om hosted pore system most pores detectable by field emission scanning electron microscopy fe sem are associated with om instead of mineral matrix in the two wells studied here total organic carbon toc content is a stronger control on om hosted porosity than is thermal maturity the two study wells span a maturity from late wet gas vitrinite reflectance ro 1 0 to dry gas ro 2 1 samples with a toc less than 5 5 wt display a positive correlation between toc and porosity but samples with a toc greater than 5 5 wt display little or no increase in porosity with a further increasing toc in a subset of samples 14 across a range of toc 2 3 13 6 wt the pore volume detectable by fe sem is a small fraction of total porosity ranging from 2 to 32 of the helium porosity importantly the fe sem visible porosity in om decreases significantly with increasing toc diminishing from 30 of om volume to less than 1 of om volume across the range of toc the morphology and size of om hosted pores also vary systematically with toc the interpretation of this anticorrelation between om content and sem visible pores remains uncertain samples with the lowest om porosity higher toc may represent gas expulsion pore collapse that was more complete as a consequence of greater om connectivity and framework compaction whereas samples with higher om porosity lower toc correspond to rigid mineral frameworks that inhibited compactional expulsion of methane filled bubbles alternatively higher toc samples may contain om low initial hydrogen index relatively unreactive that is less prone to development of fe sem detectable pores in this interpretation om type controlled by sequence stratigraphic position is a factor in determining pore size distribution

laboratory measurement of water imbibition into low permeability welded tuff abstract laboratory imbibition and vapor diffusion experiments were developed and conducted to measure accurately water imbibition and vapor condensation into welded tuff of low permeability automatically recorded balance readings were used to quantify the uptake of water into rock cores by imbibition and or vapor condensation the total uptake of water was checked against independent weighings of the sample before and after each experiment as water was imbibed into the sample and evaporated from the reservoir the buoyant force on the sample decreased balance readings corrected for the buoyancy effect agreed very well with independently measured total uptake sorptivity was calculated from the slope of a plot of corrected cumulative imbibition versus square root of time vapor condensation can provide a significant contribution to the water uptake into cores during imbibition experiments rock cores were coated with epoxy on the sides and covered on the top except for a small hole that allowed air to escape to minimize the vapor condensation contribution comparison of the sorptivity values between different core treatments shows that a consistent fraction about 20 of water uptake actually enters the core by vapor condensation overall methods for separating the confounding effects of buoyant force change and vapor condensation result in more accurate measurement of sorptivity as exhibited by the consistent and reproducible results of triplicate measurements these methods for buoyancy and vapor condensation correction are expected to be very useful for measuring imbibition rates on a wide range of porous materials especially very low permeability materials

hydrocarbon generation and shale gas accumulation in the longmaxi formation southern sichuan basin china abstract the gas bearing longmaxi formation fm records a complex tectonic history in which variations in structural and burial history directly effect the hydrocarbon maturation process through analysis of the tectonic burial history hydrocarbon maturity and easy r o numerical simulations we examine three areas representing the full spectrum of geological variability in the southern sichuan basin the changning area the luzhou area and the zigong area zishen well 1 following deposition of the longmaxi fm all three areas underwent five major tectonic events of subsidence and uplift showing an overall long term oscillation of the basin the longmaxi fm has undergone three major heating stages caledonian hercynian orogenesis time the high geothermal gradient field of hercynian and indosinian time approximately 200 300 ma and the yanshanian himalayan stage the high geothermal gradient stage is associated with extensive emeishan flood basalts or concealed basalts which could have played an important role in hydrocarbon maturation the maturation process can be divided into five stages caledonian hercyninan indosinian yanshanian and himalayan in the yanshan period the highest heating temperature of organic matter exceeded 200 c and the maturation level was more than 2 4 producing large amounts of natural gas which is the main accumulation period of shale gas in the longmaxi fm due to the large amount of hydrocarbon generated a large number of micropores were formed from organic matter evolution especially nanoscale pores during the middle diagenesis stage the longmaxi fm shale gas accumulation process is divided into four periods the source reservoir cap deposition period the initial accumulation period the main accumulation period and the adjustment period in the main accumulation period pyrolysis gas was dominant which was stored within the pores diagenetic fractures and structural fractures in adsorbed and free state ways forming the basic pattern of the longmaxi fm shale gas the current burial depth and structural stability of the longmaxi fm are critical to gas reservoir protection

active geologic processes in barrow canyon northeast chukchi sea abstract circulation patterns on the shelf and at the shelf break appear to dominate the barrow canyon system the canyon s shelf portion underlies and is maintained by the alaska coastal current a c c which flows northeastward along the coast toward the northeast corner of the broad chukchi sea offshelf and onshelf advective processes are indicated by oceanographic measurements of other workers these advective processes may play an important role in the production of bedforms that are found near the canyon head as well as in processes of erosion or non deposition in the deeper canyon itself coarse sediments recovered from the canyon axis at 400 to 570 m indicate that there is presently significant flow along the canyon the canyon hooks left at a point north of point barrow where the a c c loses its coastal constriction the left hook as well as preferential west wall erosion continues down to the abyssal plain of the canada basin at 3800 m a possible explanation for the preferential west wall erosion along the canyon at least for the upper few hundred meters is that the occasional upwelling events which cause nutrient rich water to flow along the west wall would in turn cause larger populations of burrowing organisms to live there than on the east wall and that these organisms cause high rates of bioerosion this hypothesis assumes that the dominant factor in the canyon s erosion is biological activity not current velocity sedimentary bedforms consisting of waves and furrows are formed in soft mud in a region on the shelf west of the canyon head their presence there perhaps reflects a the supply of fine suspended sediments delivered by the a c c from sources to the south probably the yukon and other rivers draining northwestern alaska and b the westward transport of these suspended sediments by the prevailing beaufort gyre which flows along the outer shelf

bathymetry and sediment dispersal dynamics along the yallahs fan delta front jamaica abstract the shallow offshore yallahs fan delta serves as a model for the interaction of littoral processes and bathymetry and how they influence sedimentation on steep submarine slopes and in deep marine basins in tectonically active areas bottom reflection profiles show that the yallahs delta front is characterized by two bathymetric zones a narrow island shelf and a steep slope dissected by the heads of at least three submarine canyons the refraction and diffraction of waves across these canyons and shelf control sediment distribution and the alternation of erosional and depositional beaches a dominantly westward longshore drift transports coarse grained sediments until they are trapped in the heads of the submarine canyons or temporarily stored on steep unstable slopes between the canyons mass gravity processes presumably move these sediments downslope where they are deposited as turbidites in the yallahs basin and out onto the colombian abyssal plain

active faulting within the offshore western gulf of corinth greece implications for models of continental rift deformation discrimination between different lithospheric extension models focusing on the roles of low angle vs high angle faulting and how strain is distributed requires high fidelity imaging of brittle deformation high resolution seismic reflection and multibeam bathymetric data in the western gulf of corinth continental rift were collected to establish the contribution of offshore faults to extension onshore fault slip here is significantly less than expected from geodetic strain rates the rift at this location is a half graben tilted to the north by s dipping faults within the uppermost crust a basement horst on the northern margin is uplifted by the north and south eratini faults and the axial channel is fault controlled subsided lowstand shorelines in the hanging wall of the north eratini and the well studied aigion fault suggest that the faults have similar displacements summed extension from the four major faults across this part of the rift eliki subchannel south eratini north eratini is 8 16 mm yr thereby reconciling geologic and geodetic data sets distributed deformation across isolated multiple faults can model this part of the rift without recourse to and potentially incompatible with an underlying low angle detachment

sedimentation and basin evolution of the oligocene miocene mesohellenic basin greece the oligocene miocene mesohellenic basin of northern greece and southern albania is filled with up to 4 km of marine turbidites and basin margin strata surface outcrops include fan deltas prodeltaic facies and sandy and shaly submarine fan facies all these facies in outcrop can be directly correlated with seismic facies in the subsurface which in turn are compared with seismic facies in modern sandy submarine fans twelve seismic markers provide a stratigraphic framework that has been dated by new nannofossil biostratigraphy lowstand facies include erosional channels on the basin slope that aggrade basinward with sandy overbank levees to give composite sand bodies with an overall lobelike character distally these pass into sandy channel termination depositional lobes highstand facies are characterized by shaly basin slopes and shaly turbidites in the basin with irregular reflections interpreted to represent shallow channels and slumps the stratigraphic occurrence of lowstand facies compares closely with published eustatic sea level curves the basin has the potential for significant gas principally in stratigraphic traps the mesohellenic basin developed as a strike slip half graben synchronous with the ionian foreland basin to the west of a mountain belt formed by the pindos nappes

experimental investigations on the geometry and connectivity of pore space in organic rich wufeng and longmaxi shales abstract the nano scale pore systems of organic rich shale reservoirs were investigated from upper ordovician wufeng and lower silurian longmaxi formations in southeast sichuan basin these two formations are the most important target plays of shale gas development in china the purpose of this article is to assess the geometry and connectivity of multi scale pore systems and to reveal the nature and complexity of pore structure for these over mature gas shales to achieve these objective total organic carbon mineralogy image analyses by focused ion beam sem low pressure nitrogen adsorption mercury injection capillary pressure micp and spontaneous fluid deionized di water and n decane imbibition were performed most of the visible pores from sem work in wufeng and longmaxi shales are within nm and m size regimes and belong to organic matter om pores the shapes of om pore in longmaxi samples are elliptical bubble like irregular or rounded wufeng pores are mainly irregular linear and faveolated even though two shales have small depth difference as well as similar thermal maturity kerogen type and toc content nano scale pores in longmaxi are mainly associated with narrow platelike or slitlike pores with pore size of 3 50 nm while inkbottle pores are dominant in wufeng samples and over 88 of the pore volume is contributed by pores with diameter

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

tectonics and sedimentation in the gulf of corinth and the zakynthos and kefallinia channels western greece abstract single channel seismic reflection profiling data are presented from the gulf of corinth and from the continental margin outside the gulf of patras different tectonic styles are exhibited in the two regions the gulf of corinth is occupied by a complex asymmetrical graben structure with major faults trending nearly perpendicular to the local tectonic zones of the internal hellenides the gulf is interpreted to have formed during the quaternary in response to approximately north south extensional stress the deep floor of the gulf is underlain by a sequence of turbidites up to 1 km thick affected by normal growth faulting that extends up to the sea floor the sea areas inside the ionian islands of zakynthos and kefallinia zakynthos and kefallinia channels occupy a broad structural depression that trends parallel to the local tectonic zones of the external hellenides and is situated on the continental side of the strophades continental margin rise the channels contain local nw se trending structural basins zakynthos and kefallinia basins whose geometry is controlled by reverse faults or thrusts with associated diapirism in triassic evaporites hydra bank is interpreted as a tilted fault block with a diapiric core and its faulted western margin can be traced into the zone of thrusting and diapirism in southeast kefallinia at the boundary between the ionian and pre apulian paxos zones of the external hellinides the zakynthos and kefallinia structural basins are filled with a variety of sediments including prodeltaic deposits in front of the modern delta complex of the acheloos river slumped masses and debris flow deposits and in the zakynthos basin occasional turbidites the boundary separating zones of extensional and compressional focal mechanisms for shallow earthquakes crosses the gulf of patras the inner part of which exhibits wnw ese trending graben tectonics apparently related to the gulf of corinth tectonic province onshore neotectonic studies around the gulf of patras are required in order to understand the nature and cause of the westward tectonic transition from wnw ese graben structures in the gulfs of corinth and patras to nw se oriented zones of subsidence with associated compressional tectonics and diapirism in the zakynthos and kefallinia channels

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

dispersion of bauxitic red mud in the gulf of corinth greece abstract bauxitic red mud slurry discharged by an aluminium processing factory on the shelf of the gulf of corinth greece is used as a tracer to examine sediment transport and dispersion processes in a tectonically active deep basin the gulf of corinth is a silled elongate basin with a maximum depth of 860 m it is characterised by high seismicity the red mud is discharged through a pipeline at a depth of 100 m where it forms an extensive deposit grab sampling has shown that the red mud extends over the slope and the abyssal plain up to a distance of 17 km from the mouth of the pipeline it forms small scattered sheet like deposits of up to 3 cm in thickness the structures observed in the scattered patches of the red mud which in some places are overlain by a thin veneer of grey olive green natural sediments suggest that the red mud is transported from the shelf to the abyssal plain by gravitative sediment flows the flows are triggered by earthquakes granulometric and geochemical analyses of the red mud samples show that the red mud during its transport from the shelf to the abyssal plain is subjected to mixing with the surrounding sediments a different mixing ratio is determined however by reference to the various trace metals fe ni co pb

submarine and coastal sediment failure triggered by the 1995 ms 6 1 r aegion earthquake gulf of corinth greece on june 15th 1995 a locally destructive earthquake of magnitude ms 6 1 on the richter scale occurred offshore 7 5 km nne of the town of aegion in the western gulf of corinth greece an offshore survey using 3 5 khz subbottom profiling system and a remote operated vehicle rov has shown that the earthquake caused small sized subaerial to submarine sediment failure in at least four sites in three fan delta deposits the rododafni the eliki and the tolofonas the fan deltas were located within a radius of about 9 km from the epicentre the areal size of the four sediment failure sites ranged from 2 104 m2 to 6 105 m2 whilst the volume of the failed masses ranged from 4 103 to 3 106 m3 the sediment deformation types identified at the failure sites consist of ground cracking rotational slides elongated slides sediment gravity flows and extrusion of mixtures of water and sand sand boils the sediment failure in the four sites affected the upper 5 6 m of well layered holocene topset and foreset fan delta deposits the failure occurred on slopes ranging from 0 2 to 23 and the slip planes were all bedding planes which have a gradient from 0 2 to 21 the dominant instability mechanism that caused the sediment failure in the rododafni and eliki fan deltas is considered to be liquefaction of a shallow sub surface horizon the liquefaction was caused by elevated pore pressure enhanced perhaps by the presence of gas resulting from the cyclic loading induced by the earthquake the liquefied layer is assumed to have temporarily provided a failure surface for sliding to take place on and caused movement of sand that was ejected onto the surface in the tolofonas fan delta the causative mechanism in the case of the multi block rotational slide is considered to be deformation of the underlying sediments caused by remoulding and or liquefaction while in the case of the elongated slide it is considered to be the result of a combination of shear stress increase and or strength degradation of the unconsolidated sediment both of these conditions could have been generated during the cyclic loading resulting from the aegion earthquake the study of historical documents reveals that sediment failure like those described above have also occurred at least four times during the past 2500 years in the same locations therefore it is suggested that they could be repeated in the future by any earthquake event with a magnitude greater than 6 r depending upon the proximity of the site to the earthquake epicentre

experimental investigations of the wettability of clays and shales 1 wettability in argillaceous materials is poorly understood yet it is critical to hydrocarbon recovery in clay rich reservoirs and capillary seal capacity in both caprocks and fault gouges the hydrophobic or hydrophilic nature of clay bearing soils and sediments also controls to a large degree the movement of spilled nonaqueous phase liquids in the subsurface and the options available for remediation of these pollutants in this paper the wettability of hydrocarbons contacting shales in their natural state and the tendencies for wettability alteration were examined water wet oil wet and mixed wet shales from wells in australia were investigated and were compared with simplified model shales single and mixed minerals artificially treated in crude oil the intact natural shale samples preserved with their original water content were characterized petrophysically by dielectric spectroscopy and nuclear magnetic resonance plus scanning electron optical and fluorescence microscopy wettability alteration was studied using spontaneous imbibition pigment extraction and the sessile drop method for contact angle measurement the mineralogy and chemical compositions of the shales were determined by standard methods by studying pure minerals and natural shales in parallel a correlation between the petrophysical properties and wetting behavior was observed these correlations may potentially be used to assess wettability in downhole measurements

sediment transport processes on an active submarine fault escarpment gulf of corinth greece abstract sediment transport processes on the escarpment of a listric fault in the tectonically active and terrigenous sediment dominated corinth graben in greece are studied using 3 5 khz and airgun profiles and sidescan sonar images the whole of the slope area is affected by gravitational mass movements slumps debris mud flows and liquified and turbidity flows in canyon fan systems large volumes of sediment are transported through slumping debris mud and turbidity flows into the basin here they build coalescing fans which consist of intercalations of debris flow deposits and turbidites in delta front slope fan apron systems sediments are transported radially downslope through slumping debris mud flows liquified flows and high density turbidity flows into the basin where they build coalescing fan aprons these consist of massive homogenized deposits fluxoturbidites in shelf slope systems retrogressive rotational slumping is the dominant instability feature however due to the sharp increase in the slope gradient caused by the slumping debris and turbidity flows are triggered the major factors responsible for triggering gravitational mass movements in the region are earthquakes high sedimentation rates off the river mouths and heavy rainfalls and high seas these mass movements appear to occur at least once every 2 yrs as indicated by the failure of submarine cables

the seismicity geomorphology and structural evolution of the corinth area of greece in the eastern gulf of corinth geological structure is closely reflected in the topography in the 1981 corinth earthquakes ground deformation accentuated existing geomorphological patterns we explore the relationship between seismicity and landforms in space and time the area examined extends beyond the epicentral region of the 1981 events and its evolution is traced over the last 40000 years to understand the relation between deep and superficial structures we discuss processes that occurred in the 1981 earthquakes and go on to propose that surface faulting appears only above linear faults at depth that move in earthquakes with magnitudes m s greater than six where faults at depth intersect or bend the faulting becomes distributed and prim ary faulting does not reach the surface here the surface manifestation of faulting at depth is surface folding and secondary faulting such regions are identified in maps of the eastern gulf of corinth evidence for the evolution of the fault systems is provided by eyewitness accounts of shoreline changes following the recent earthquakes historical and archaeological data pertaining to old sea levels and 14 c dates for molluscs collected from fossil shorelines the results of these studies broadly confirm an earlier view of j a jackson et al earth planet sci lett 57 377 397 1982 that motion has shifted from faulting south of the city of corinth to faulting in the perachora peninsula but the transfer is not complete areas lying between the two fault systems have moved up and down in historical and archaeological times indicating that both systems are still active the evidence for activity of the northern system points to a repeat time of 300 years for earthquakes com parable with those of 1981 the work discussed in this paper suggests that some of the features previously described as m arine terraces are fault controlled continental surfaces furtherm ore beach deposits at a num ber of different levels long regarded as successive shorelines are in fact contemporaneous the critical ages were obtained by radiocarbon dating of shell carbonate a technique which yields dependable results if applied to samples which have been carefully selected and pretreated palaeontological dating of the terraces in contrast is found to be misleading because the faunas are environm entally controlled and consequently diachronous

alternating marine and lacustrine sedimentation during late quaternary in the gulf of corinth rift basin central greece abstract the gulf of corinth in central greece has a maximum depth of about 900 m and is separated from the open sea by the rion strait with a sill depth of 62 m marked by an extensive submarine terrace during eustatic sea level lowstands the gulf of corinth was a lake under lacustrine conditions stratified sediments accumulated in the deep water basins and turbid underflows from rivers eroded the basin slopes as the sea level rose marine waters flooded the gulf and deltas prograded across the shelves in shallow water areas two key reflectors termed z and x are terrace surfaces commonly erosional which mark the base of the overlying deltaic sequences in deep water basins z and x mark the top of the acoustically stratified sediments interpreted as lacustrine turbidites reflectors y and w mark the base of these stratified intervals and overlie acoustically transparent sections similar to the holocene section the last lacustrine conditions in the gulf z to y were during isotopic stage 2 and terminated about 12 000 yr ago age estimates based on sedimentation rates suggest that the x to w interval corresponds to the stage 4 lowstand of sea level in the western gulf of corinth shoreline transgressive surfaces corresponding to minor transgressions in stage 5 and to major transgression at the end of stage 6 are recognised this seismic stratigraphy permits a detailed interpretation of the history of the gulf of corinth in the past hundred thousand years it also provides a general model for sedimentation in rift basins in which marine and lacustrine sediments alternate

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

wettability and connectivity of overmature shales in the fuling gas field sichuan basin china the fuling gas field in sichuan basin china has produced greater than 1 5 1010 m3 0 53 tcf of natural gas from overmature upper ordovician wufeng and lower silurian longmaxi shales to systemically investigate the characteristics of wettability and connectivity and to understand the underlying causes of production behavior we study five samples of wufeng and longmaxi shales with different total organic carbon contents and mineral compositions complementary approaches include mercury intrusion capillary pressure micp contact angle measurement spontaneous imbibition and saturated diffusion and tracer both nonsorbing and sorbing migration mapped via laser ablation inductively coupled plasma mass spectrometry according to measured contact angles and imbibition tests conducted on aqueous deionized water and brine and oleic n decane phases wufeng and longmaxi shales are strongly oil wet and moderately strong water wet the lower boundary of estimated permeability obtained from n decane imbibition can reach 137 nd which is higher than the geometric mean permeability derived from the micp method 5 5 68 8 nd effective diffusion coefficients of the wufeng and longmaxi shales are in the range of 10 13 m2 s 1 1 10 12 ft2 s tests of imbibition and saturated diffusion using tracer containing brine show that concentrations of nanometer sized tracers decrease rapidly a factor of 10 over a migration distance of a few millimeters from the sample edge suggesting the presence of poorly edge connected water wet pores sparsely connected hydrophilic pores mixed wettability and highly restricted pathways collectively contribute to the limited migration of nano sized tracers which probably results in the production behavior of initial steep decline and low overall recovery in the fuling gas field

geometric and depositional responses of carbonate build ups to miocene sea level and regional tectonics offshore northwest australia abstract the geometric and depositional responses of isolated carbonate build ups to miocene sea level change and regional tectonics are investigated using 3d seismic and borehole data from the browse basin north west australia combined with outcrop information from the cariatiz reef southeast spain the interpreted seismic volume documents five 5 miocene sequence boundaries and five 5 main seismic facies seismic attribute analyses proved to be a highly effective tool for interpreting carbonate facies but when compared with outcrop information from southeast spain attribute data are limited to features larger than 16 4 m vertically and 18 75 m horizontally estimations of reservoir potential are thus significantly underestimated when only based on the interpretation of seismic data as a corollary of the structural analysis in this work growth patterns suggest messinian structural partitioning across the browse basin with deformation associated with plate collision focused on preferentially oriented faults i e only influencing carbonate build up evolution at a local scale

geochemical characteristics of marine and terrestrial shale gas in china abstract although the annual production of shale gas in china was 13 10 8 m 3 in 2014 a systematic study on geochemical and isotopic characteristics of these unconventional gases has not been well addressed in the present study almost all shale gas samples available in china including marine shale gas from the wufeng longmaxi formation in the sichuan basin o 3 w s 1 l and terrestrial shale gas from chang 7 member t 3 y 7 in the ordos basin were collected and analyzed for their geochemical and isotopic compositions the shale gas from the wufeng longmaxi shale is dry gas with an average methane content of 98 38 and records a highest content of ch 4 in the world 99 59 which is consistent with the very high thermal maturity levels of the gas shales that have equivalent vitrinite reflectance eqvro values between 2 4 and 3 6 the 13 c 1 values are correspondingly heavy and record a heaviest 13 c 1 values 26 7 for the shale gases found in the world as well the average values of 13 c 1 13 c 2 and 13 c 3 for the wufeng longmaxi shale gas are 31 3 35 6 and 47 2 respectively displaying a complete carbon isotopic reversal i e 13 c 1 13 c 2 13 c 3 2 h ch4 and 2 h c2h6 has an average value of 148 and 173 respectively also yielding a hydrogen isotopic reversal i e 2 h ch4 2 h c2h6 the chang 7 shale has an average toc content of 13 81 with vitrinite reflectance vro values between 0 7 and 1 2 the chang 7 shale gas is wet gas with an average methane content of 84 90 and is rich in heavy gaseous hydrocarbons c 2 c 5 the respective values of 13 c 1 13 c 2 and 13 c 3 are 48 7 36 4 and 31 3 displaying a positive carbon isotopic distribution pattern i e 13 c 1 13 c 2 13 c 3 the average 2 h ch4 2 h c2h6 and 2 h c3h8 values are 256 244 and 188 respectively and are characterized by a positive distribution pattern i e 2 h ch4 2 h c2h6 2 h c3h8 the differences in gas wetness and carbon and hydrogen isotopic distribution patterns between the shale gases from the wufeng longmaxi and chang 7 shale are attributed to variations in thermal maturity levels co 2 is present in low content in both the wufeng longmaxi and chang 7 shale gases mostly less than 1 13 c values for the co 2 in the wufeng longmaxi formation are between 8 9 and 9 2 indicating an inorganic origin from the cracking of carbonate mineral in the shales under high temperatures in contrast 13 c values of the co 2 in the chang 7 shale gas range from 8 2 to 22 7 indicating an organic origin from the thermal degradation of organic matter helium in both the wufeng longmaxi and chang 7 shale gases is dominantly of curst origin in terms of their r ra ratios that vary from 0 01 to 0 08 positive carbon isotopic distribution pattern is typical of primitive thermogenic gas however it can be converted into complete or partial carbon isotopic reversal patterns due to secondary alteration the causes that yield carbon isotopic reversal include 1 mixing of gases with the same source but different thermal maturity levels 2 secondary cracking of oil or wet gas 3 formation water involved reactions 4 gas diffusion and 5 carbon isotope exchange between alkane gases at high temperature among them carbon isotopic exchange between alkane gases at high temperature is a key factor nine plots have been drawn based on the shale gases from china usa and canada among them the plot of 13 c 2 versus wetness demonstrates a lying s shape with two inflection points on the gas wetness axis the wetness value of 1 4 represents a critical point from pyrolytic gas primary cracking gas to cracking gas secondary cracking gas and whereas the wetness value of 6 marks the end of oil generation on the diagram of wetness versus 13 c shale gases with wetness values greater than 1 6 are characterized by positive carbon isotopic distribution pattern whereas a complete or partial carbon isotopic reversals are observed for shale gases with wetness values less than 1 6

morphology of a submarine slide kitimat arm british columbia a digitally acquired scale corrected side scan sonar survey yielded high resolution imagery of a submarine landslide in british columbia the landslide in a fjord head setting at kitimat was last active in 1975 and created a wide area of deformed sea floor the sediment failure involved shallow rotational movements on the slopes of a fjord head delta marginal tearing translational sliding compressional folding and block gliding of fjord bottom marine clays the slide is shallow and elongate and appears to have been produced by failure in mobile low strength sediments

submarine fan systems i characterization and stratigraphic prediction submarine fan and related deep marine clastic systems such as submarine ramps and slope aprons are important hydrocarbon reservoirs in many parts of the world the origin and character of these systems reflect a complex interplay between a range of autocyclic and allocyclic controls including sea level fluctuations basinal tectonics and the rate type and nature of sediment supply these controls are commonly interdependent this paper reviews the characteristics which distinguish different submarine fans and their subsurface prediction then proposes a classification framework for fans which discriminates between different systems on the basis of their fundamental controls the proposed classification is discussed in terms of its value as a predictive tool in hydrocarbon exploration development and production a modus operandi is developed which uses the classification for reservoir description and prediction and involves three stages of investigation basin screening fan delineation and fan characterization each stage demands the integration of a range of tools and techniques including sequence stratigraphy seismic facies analysis seismic redisplay and geophysical modeling these stages of analysis are linked in turn with core and wireline log data to constrain the range of possible fan types within a basin fill and assess the implications for reservoir seal and trap development this structured approach to stratigraphic analysis is also valuable in constraining the range of reservoir architectural options in appraisal development and production

characterizing the pore structure of low permeability eocene liushagang formation reservoir rocks from beibuwan basin in northern south china sea abstract the hydrocarbon exploration from low permeability 50 nm mainly contribute to the total pore spaces for most samples with lower shale content mesopores 2 50 nm dominate the pore spaces of samples with higher shale content which leads to the relatively large surface area of these samples permeability of these low permeability rocks is positively related with average pore throat radius and negatively related with relative sorting coefficient while no such a close relationship exists between permeability and porosity fractal dimension has a negative relationship with average pore throat radius and permeability in summary this work comprehensively investigates the pore structure characteristics of low permeability liushagang formation reservoir rocks from beibuwan basin using multiple complementary approaches which helps to further understand the hydrocarbon migration and accumulation mechanism of these low permeability reservoirs

controls and evolution of fan delta systems in the miocene pohang basin se korea abstract the miocene pohang basin southeastern korea occurs in the eastern part of the ne sw trending yangsan fault which has experienced right lateral strike slip deformation since the eocene during the miocene however the strike slip movement was negligible and instead was under extensional regime large scale drainage systems were developed at the junction between the strike slip zone and the oblique transfer faults acting as major sources for coarse grained sediments high rate of sediment supply and rapid subsidence of the hanging wall resulted in the progradation of large scale gilbert type fan deltas doumsan duksung and gohyun systems which all show a radial distributional pattern along the steeply inclined footwall scarps created by ne sw trending faults the drainage systems were relatively small here low rate of sediment supply formed scree apron type malgol and yugye systems and steep faced slope type maesan system fan deltas based on variations in sedimentary facies and distribution architecture and overlapping patterns the fan delta systems in the pohang basin can be divided into four stages of evolution during the early stage early miocene alluvial fans prograded into shallow marine setting in the doumsan and duksung systems high rate of sediment supply and rapid rise of relative sea level resulted in the transformation of shoal water type to gilbert type foresets in the malgol and maesan systems rapid sea level rise accompanied with low rate of sediment supply caused transformation of alluvial fans to scree apron type and steep faced slope type fan deltas respectively in the second stage subsidence of the hanging wall formed large scale truncation surfaces in the doumsan and duksung fan deltas coarse grained sediments were continuously supplied in the doumsan system whereas only fine grained sediments were deposited in the duksung system in the malgol system sediment supply was almost terminated in this stage in the third stage middle miocene sediment supply rate of the doumsan fan delta decreased abruptly and the system was overlain by fine grained gilbert type deposits the duksung fan delta was overlain by the maesan and gohyun systems the maesan system prograded further basinward during the last stage late miocene sediment supply of the doumsan and maesan systems was also terminated and the entire basin was draped by fine grained biogenic materials mainly diatoms

basinal setting and origin of thick 1 8 km mass flow dominated grand conglomerat diamictites kamoa democratic republic of congo resolving climate and tectonic controls during neoproterozoic glaciations

porosity of devonian and mississippian new albany shale across a maturation gradient insights from organic petrology gas adsorption and mercury intrusion the evolution of porosity in shales with increasing maturity was examined in a suite of five new albany shale samples spanning a maturity range from immature vitrinite reflectance ro 0 35 to postmature ro 1 41 devonian to lower mississippian new albany shale samples from the illinois basin used in this study contain marine type ii kerogen having total organic carbon contents from 1 2 to 13 0 wt organic petrology co2 and n2 low pressure adsorption and mercury intrusion capillary pressure techniques were used to quantify pore volumes pore sizes and pore size distributions increasing maturity of the new albany shale is paralleled by many changes in the characteristics of porosity the total porosity of 9 1 vol in immature new albany shale decreases to 1 5 vol in the late mature sample whereas total pore volumes decrease from 0 0365 to 0 0059 cm3 g in the same sequence reversing the trend at even higher maturity the postmature new albany shale exhibits higher porosity and larger total pore volumes compared to the late mature sample with increasing maturity changes in total porosity and total pore volumes are accompanied by changes in pore size distributions and relative proportions of micropores mesopores and macropores porosity related variances are directly related to differences in the amount and character of the organic matter and mineralogical composition but maturity exerts the dominant control upon these characteristics we conclude that organic matter transformation due to hydrocarbon generation and migration is a pivotal cause of the observed porosity differences

2d and 3d nanopore characterization of gas shale in longmaxi formation based on fib sem abstract studying complex pore structures is the key to understanding the mechanism of shale gas accumulation fib sem focused ion beam scanning electron microscope is the mainstream and effective instrument for imaging nanopores in gas shales based on this technology 2d and 3d characteristics of shale samples from lower silurian longmaxi formation in southern sichuan basin were investigated 2d experimental results show that the pores in shale are nanometer sized and the structure of those nanopores can be classified into three types organic pores inorganic pores and micro fractures among the three types organic pores are dominantly developed in the om organic matter with three patterns such as continuous distributed om om between clay minerals and om between pyrite particles and the size of organic pores range from 5 nm to 200 nm inveresly inorganic pores and micro fractures are less developed in the longmaxi shales 3d digital rocks were reconstructed and segmented by 600 continuous images by fib cutting and sem imaging simultaneously the pore size distribution and porosity can be calculated by this 3d digital core showing that its average value is 32 nm and porosity is 3 62 the 3d digital porosity is higher than its helium porosity which can be regarded as one important parameter for evaluation of shale gas reserves the 2d and 3d characterized results suggest that the nanometer sized pores in organic matter take up the fundamental storage space for the longmaxi shale these characteristics have contributed to the preservation of shale gas in this complex tectonic area

micro and nano size pores of clay minerals in shale reservoirs implication for the accumulation of shale gas abstract a pore is an essential component of shale gas reservoirs clay minerals are the adsorption carrier second only to organic matter this paper uses the organic maturity test field emission scanning electron microscopy fe sem and x ray diffraction xrd to study the structure and effect of clay minerals on storing gas in shales results show the depositional environment and organic maturity influence the content and types of clay minerals as well as their structure in the three types of sedimentary facies in china clay minerals develop multi size pores which shrink to micro and nano size by close compaction during diagenesis micro and nano pores can be divided into six types 1 interlayer 2 intergranular 3 pore and fracture in contact with organic matter 4 pore and fracture in contact with other types of minerals 5 dissolved and 6 micro cracks the contribution of clay minerals to the presence of pores in shale is evident and the clay plane porosity can even reach 16 close to the contribution of organic matter the amount of clay minerals and pores displays a positive correlation clay minerals possess a strong adsorption which is affected by moisture and reservoir maturity different pore levels of clay minerals are mutually arranged thus essentially producing distinct reservoir adsorption effects understanding the structural characteristics of micro and nano pores in clay minerals can provide a tool for the exploration and development of shale gas reservoirs

slope failures and stability analysis of shallow water prodeltas in the active margins of western greece northeastern mediterranean sea sediment instabilities are common on the prodeltas of the seismically active continental margins of western greece sediment failures on the low angle 0 5 2 prodelta slopes manifest themselves as successions of peripheral rotational block slumps restricted to the foresets of the late highstand systems tract hst the individual slump blocks are about 80 150 m long and are bounded by growth faults acting as curved slip planes that extend to a mean depth of 10 15 m below seafloor shear planes develop in the lower part of muddy and or gas charged hst foresets deeper basal transparent muddy layers of the early hst bottomset together with the late pleistocene transgressive systems tract sequences tst are mostly unaffected on the steeper 2 6 fan delta slopes of the western gulf of corinth debris flows and avalanches with a significant retrogressive component dominate slope destabilisation sediment cores taken from landslide scarps and slide planes penetrated gas bubble releasing sediments thereby indicating that failure planes are in the late hst foresets upper part of the early hst bottomsets gas charged zone the foresets of the hst prodelta deposits display high water content 30 80 low bulk density 1 4 1 9 g cm 3 and relatively low values of undrained shear strength 3 20 kpa the water content of the hst distal muddy bottomsets is relatively higher 50 110 and bulk density relatively lower 1 3 1 7 g cm 3 with low values of shear strength 2 10 kpa the shear strength of the gas releasing sediment layer displays lower values 2 9 kpa relative to the overlying post failure muddy sediments of the late 100 300 years slope stability was calculated using the normalised soil parameter nsp method under undrained conditions for normally consolidated prodelta sediments this analysis indicates that instabilities could be induced by critical earthquake ground accelerations of 26 6 29 6 g for the hst foresets and 12 4 14 1 g for the basal transparent layer belonging to the early hst bottomsets consequently the early hst bottomsets has to be considered a potentially unstable layer since the regional peak ground accelerations pgas for the next 50 years are expected to range from 19 to 30 g moreover our results show that new glide planes in the prodeltaic sediment bodies of the seismically active continental margins of western greece will likely develop from the gas charged sediments of the lower part of the hst foresets to the upper part of early hst bottomsets

the effects of pore structure on wettability and methane adsorption capability of longmaxi formation shale from the southern sichuan basin in china the lower silurian longmaxi formation shale in the sichuan basin is one of the most promising shale gas plays in china pore structure has a significant impact on hydrocarbon migration within shales this study conducts systematic experiments to analyze the pore structure wettability and methane adsorption capacity of the longmaxi formation shale samples from the southern sichuan basin the pore size distributions obtained from n2 adsorption high pressure mercury intrusion porosimetry and statistical analysis of representative field emission scanning electron microscopy photographs of organic matter om are compared to evaluate the contribution of om pores to total pore spaces shale wettability was determined by contact angle measurements and spontaneous imbibition experiments the results reveal that these samples could be divided into three wettability categories more water wet samples z1 more oil wet samples z4 and intermediate wet samples z2 and z3 although samples z1 and z4 have similar total organic carbon toc contents om pores within sample z4 have a larger average pore size and occupy a greater proportion of the total pore spaces compared with sample z1 whereas inorganic pores contribute more to the total pore spaces of sample z1 sample z4 has a larger methane adsorption capacity than sample z1 with a higher brunauer emmett teller bet surface area which may be caused by the difference in their om pore types samples z2 and z3 with less toc content have lower porosities and bet surface areas as well as lower methane adsorption capacities consequently the pore structure significantly affects the wettability and methane adsorption capacity of the longmaxi shale

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

wettability of mississippian barnett shale samples at different depths investigations from directional spontaneous imbibition because of its significant impact on relative permeability capillary pressure stimulation methods and ultimate recovery the wettability of reservoir rocks is a critical factor of the petroleum recovery process however characterizing the wettability of shale with extremely low matrix permeabilities is a challenging task because of the dominant presence of nanopores in shale and high heterogeneity of shale compositions at multiple scales from spontaneous imbibition behavior that uses two types of imbibing fluid water and n decane the present study examines the wettability characteristics of gas window barnett shale samples taken from four different depths of texas united 1 blakely core in wise county in texas imbibition experiments were conducted in two directions parallel and transverse to the lamination of the samples a scaling method was used to analyze imbibition data and observed imbibition behaviors were interpreted to infer the different wettability conditions of four samples with different mineralogy total organic carbon content and pore throat size distribution our results show that wettability significantly affects fluid imbibition behavior and that four tested samples can be divided into three wettability categories more water wet mixed wet and more oil wet overall the variable wettability of barnett samples will affect hydrocarbon storage distribution and production

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

effect of lithofacies on pore structure and new insights into pore preserving mechanisms of the over mature qiongzhusi marine shales in lower cambrian of the southern sichuan basin china abstract research on shale pore structures has furthered the understanding of shale oil and gas accumulation however understanding of mechanisms of shale lithofacies that affect pore structures remains poor restricting evaluations of marine shale and accurate estimations of gas content this study focuses on the over mature qiongzhusi marine shales in lower cambrian of the southern sichuan basin a series of laboratory experiments were conducted on core samples including x ray diffraction xrd scanning electron microscopy sem low pressure gas adsorption n2 and co2 and high pressure mercury intrusion porosimetry mip xrd results show that four main types of shale lithofacies are found in the qiongzhusi formation according to the content of siliceous carbonate and clay minerals including silica rich argillaceous shale lithofacies sal argillaceous rich siliceous shale lithofacies asl carbonate argillaceous containing siliceous shale lithofacies c asl and argillaceous siliceous mixed shale lithofacies a sml sem images reveal that three kinds of pores within the shale samples organic matter intergranular and dissolved pores with the majority being slit like and narrow slit like pores silica rich argillaceous shale lithofacies exhibit the highest pore surface areas and volumes while other shale lithofacies and carbonate clay containing siliceous shale lithofacies exhibit relatively lower pore surface areas and volumes it can be inferred that silica rich argillaceous shale lithofacies facilitate shale gas storage and flow both toc and clay mineral content are more positively correlated with the microscopic pore structure parameters of micropores than that of mesopores and thus further interpreted as two dominant factors controlling the development and distribution of micropores a relatively high quartz content in qiongzhusi shale of lower cambrian are conductive to contribute a large macropore volume but most importantly the development of rigid frameworks established by authigenic quartz pyrite and clay minerals are favorable for the preservation of primary organic matter micropores by providing effective grain supporters clay rich siliceous shale could be deemed as one of the most typical lithofacies types displaying this unique pore preserving mechanism shale lithofacies with different toc and mineral compositions exhibit distinct differences in pore structures

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

channelled erosion through a marine dump site of dredge spoils at the mouth of the puyallup river washington state usa abstract channels are relatively common on river mouth deltas but the process by which they arise from river sediment discharge is unclear because they can potentially be explained either by negatively buoyant hyperpycnal flows produced directly from the river outflow or by flows generated by repeated failure and mobilisation of sediment rapidly deposited at the delta front channels eroded through a dump site of dredge spoils are described here from multibeam and older sonar data collected in commencement bay at the mouth of the puyallup river shallow channels on the seaward upper surface of the dump site away from any flows that could have been produced by delta front failures suggest that at least some hyperpycnal flows were produced directly from the positively buoyant river outflow up to 200 m from the edge of the river mouth platform the form of channel bed erosion is revealed by the longitudinal shape of the main eroded channel compared with the adjacent dump site profile it suggests that the channel evolved by its steep front retreating rather than by simple vertical entrenchment or diffusive like evolution of the profile a geometry interpreted as evidence that repeated failure of the bed occurred in response to shear stress imposed by bottom travelling flows model calculations based on shear strengths back calculated from the geometry of channel wall failures suggest that if the main channel were eroded solely by hyperpycnal flows their generation was remarkably efficient in order to create flows vigorous enough to cause channel bed failure besides the sediment concentration and discharge characteristics that have been considered to dictate the ability of rivers to produce hyperpycnal flows it is suggested that the timing of floods with respect to the tidal cycle should also be important because extreme low tides may be needed to ensure that coarse sediment is transferred vigorously to the edge of river mouth platforms

mechanisms of sediment transport and dispersion in a tectonically active submarine valley canyon system zakynthos straits nw hellenic trench abstract physical oceanographic and geophysical data sets are used to examine sediment transport processes currents were directed generally along the axis of the valley canyon system and in an area of low tidal range are attributed to regional weather patterns near bed and near surface currents are opposed both in terms of instantaneous observations and net lagrangian drift near bed down canyon water movement provides a mechanism for the offshore movement of fine grained sediment slope failures have been identified in the geophysical records and are considered to be controlled by earthquakes and salt diapirism in a tectonically active area these failures as mass displacement or slow down slope creep result in debris infill and the generation of turbidity currents fine grained sediments resuspended by the turbidity currents would be transported down canyon by the slowly moving near bed residual water movement hence the dominant transport mechanisms in the valley canyon system are 1 frequent mass sediment failure and 2 nearly continuous down channel fine grained suspended sediment movement

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