source rock and seep oil maturity in dorset southern england abstract analysis of the steranes and triterpanes in the oil seeps of the dorset coast of southern england mupe bay osmington mills shows both the oils to derive from a similar mid late mature source rock measured maturity of the jurassic source rocks at outcrop are uniformally immature 0 3 0 5 r despite a history of mesozoic burial and tertiary inversion and uplift evidence from oil cemented sandstone clasts within oil stained lower cretaceous fluviatile channel sands at mupe bay suggests that oil was already seeping during the lower cretaceous detailed work comparing the extracts of the oil stained clasts and the surrounding oil stained sandstones shows the clasts to contain oil derived from a slightly but significantly less mature source rock this is consistent with lower maturity oil seeping first into the sand that was then incorporated as rip up or bank collapse clasts into the channel sand at a later stage with further source rock burial more mature oil entered the matrix sandstone locally calibrated time temperature thermal geohistory modelling can just simulate source rock maturities appropriate to the seep oils if paleo geothermal gradients and surface temperatures were locally higher in the jurassic than at the present day a volumetric balance between oil in place in the wytch farm field and the available area of source rock draining into the structure suggests that an anomalously thick and or organic rich rhaeto liassic section must have developed in the bournemouth bay basin and that cretaceous palaeo geothermal gradients were higher in this specific area

in situ sand state from cpt evaluation of a unified approach at two canlex sites cet article est consacre a l analyse des donnees de cpt dans les sables afin de deduire l indice des vides a partir des resistances a la penetration au cone l on a etudie a l interieur d un nouveau cadre de reference deux sites de canlex l un appele site syncrude comprenant un depot de sable de steriles relativement homogenes a fort mcmurray alberta et l autre qui est un des sites de la phase ii constitue d un depot de sable naturel dans le delta du fleuve fraser pres du tunnel massey en colombie britannique l approche proposee considere que la resistance en pointe normalisee des sables est reliee a un parametre d etat normalise au niveau initial de contrainte et a la contrainte a l etat critique la methode d interpretation fournit l etat in situ d un depot de sable donne et requiert la connaissance des parametres a l etat critique qui peuvent etre determines en laboratoire sur des echantillons reconstitues cependant il est essentiel d obtenir ces parametres sur une plage etendue de contraintes incluant les contraintes pour lesquelles le broyage des grains est produit par cisaillement une concordance etroite a ete obtenue sur le site de syncrude qui est un depot relativement jeune cependant l analyse des donnees de cpt du site de massey suggere que le vieillissement et ou la cimentation influencent la resistance a la penetration au cone donc l etat in situ si les valeurs non corrigees du cpt sont utilisees

ground freezing and sampling of pleistocene sand near charleston south carolina abstractthe procedures used to freeze and sample a pleistocene sand deposit near charleston south carolina to preserve and study the effects of diagenesis are presented in this paper based on the results of geotechnical tests and a feasibility ground freezing study a freezing system with a central freeze pipe was installed to target a column of clean sand 1 m in radius and 2 3 m in length liquid nitrogen was continuously supplied to the freeze pipe fabricated to freeze the sand between depths of 1 8 and 3 8 m below the ground surface for 270 h frozen sand cores taken from five locations 0 65 to 0 7 m away from the central freeze pipe indicate the ground was frozen between depths of 1 8 and 3 8 m at all but one location ground temperature measurements growth of the frozen zone and the amount of liquid nitrogen consumed are presented and compared with predicted values recorded temperatures indicate that the freezing was influenced by the direction of groundwater flow the flow rate of liquid nitrog

peak shear strength and dilatancy of a pleistocene age sand abstractthis paper summarizes results of laboratory investigations performed to quantify the influence of diagenesis or aging processes on the peak shear strength and dilatancy of an uncemented pleistocene age sand sampled near charleston south carolina drained triaxial compression tests were performed on high quality intact specimens retrieved using the in situ freezing and sampling method and on remolded specimens prepared with matching densities the stress strain behavior of intact specimens is accompanied by dilation and a peak shear value whereas remolded specimens generally contracted throughout shearing an age dilatancy term is added to a dilatancy index equation to account for the difference between intact and remolded peak friction angles the resulting equation suggests that dilatancies due to age and density are suppressed with increasing confining pressure a profile of peak friction angle with depth is established from the results and compared with estimates from empirical relationships

liquefaction analysis of duncan dam using strength ratios b c hydro performed extensive seismic safety studies for duncan dam in the late 1980s and early 1990s the results of these studies indicated that duncan dam was reasonably safe from liquefaction induced failure a recently proposed liquefaction analysis procedure that uses strength ratios to assess liquefaction triggering and post triggering stability was used to revisit the liquefaction analysis of duncan dam when compared to the detailed field and analytical studies performed by b c hydro the proposed liquefaction analysis procedure predicts i similar zones of liquefaction within a contractive unit of foundation sand ii similar shear strengths at the triggering of liquefaction yield shear strength and at large strain liquefied shear strength and iii similar post triggering factors of safety for slope stability the good agreement suggests that the strength ratio based liquefaction analysis approach is relatively robust and is suitable for screening level studies for large projects or m

ground freezing and sampling of foundation soils at duncan dam in situ ground freezing to obtain undisturbed samples of a loose sand beneath the duncan dam in british columbia is described this was the first known use of ground freezing to assist in obtaining samples at depth greater than 10 m in canada once frozen the sand was cored and brought to the surface using a cold regions research and engineering laboratory core barrel which is used extensively in permafrost regions the design installation and performance of the liquid nitrogen freezing systems are described in detail the drilling sampling and preparation of the frozen core for transport to the testing facility are also outlined the quality of the core retrieved during the sampling was judged to be excellent and good agreement was found between the void ratios measured using both the frozen core and high quality gamma gamma density logging techniques which were performed adjacent to ground freezing and sampling locations key words ground freezing cohesionless soils undisturbed sampling

detection of ocean wave groupiness from spaceborne synthetic aperture radar 1 in recent years a number of remote sensing techniques capable to provide two dimensional information of the sea surface have been applied to describe sea states this information is obtained from the estimation of the directional wave number spectrum however the wave number spectrum is not sufficient for a complete description of sea states the analysis of some phenomena such as wave grouping detection of individual waves maximum wave heights etc needs a complementary study which has been carried out historically in the temporal domain from buoy records in two dimensions e g the spatial domain the complementary analysis of those phenomena can be carried out in the spatial domain rather than the temporal domain in this work two methods to analyze wave groupiness in the spatial domain from sea surface images are presented the first method is based on the two dimensional generalization of the smoothed instantaneous wave energy history siweh function which had been originally developed to analyze wave groupiness for wave elevation time series the second method uses the estimation of the wave envelope in two dimensions to extract wave grouping parameters assuming that the wave fields are gaussian stochastic processes both methods are applied to ers 2 synthetic aperture radar sar and envisat advanced sar asar images of the sea surface where only cases with almost range traveling waves are considered in order to avoid strong nonlinearities in the sar imaging mechanisms the obtained results shown that spaceborne sar can be used to extract wave grouping information on global scale

in situ ground freezing to obtain undisturbed samples of loose sand in situ ground freezing with liquid nitrogen can be an excellent technique for obtaining high quality undisturbed samples from a wide range of loose sand deposits with their in situ conditions preserved this paper describes the techniques used during the canlex project to carry out in situ ground freezing and undisturbed sampling of the loose sand deposits encountered at six test sites specific details with respect to the effects of difficult subsoil or ground water conditions encountered at the sites are provided modifications made to the ground freezing and sampling system to accommodate difficult ground conditions are described the actual advance of the freezing front and the consumption of liquid nitrogen are compared with theoretical predictions the dry coring technique utilized to recover undisturbed frozen sand samples is described the void ratios measured for the frozen core samples are compared with void ratio measurements obtained using geophysical logging in boreholes located within a 5 m radius of the freeze pipe the costs associated with in situ ground freezing utilizing liquid nitrogen and coring of the frozen sand at six test sites are presented

major erosion surfaces in the basal wealden beds lower cretaceous south dorset the transition from evaporitic and lagoonal purbeck beds into the fluviatile basal wealden beds ryazanian valanginian has in the past been interpreted as a continuous regressive succession mupe bay and bacon hole in south dorset are the only localities in the wessex basin of southern england at which the transition strata are well exposed and not extensively faulted on the basis of facies analysis the lowermost wealden beds are interpreted as a regressive transgressive regressive package environments fluctuated between lagoon inner lagoonal shoreline and fluvial flood plain the overlying succession is remarkable for the presence of two major erosion surfaces which based on field geometries and facies relationships are interpreted as unconformities the lower unconfor mity is overlain at mupe bay by sediments of lagoonal or lacustrine origin the upper unconformity is expressed as the celebrated mupe bay palaeo oilseep an oil cemented conglomeratic sand overlain by a thick succession of fluvial sediments a level near the basal sand and the two erosion surfaces are treated as candidate sequence boundaries wbl wb3 with the thin intervening lagoonal deposits representing peaks of transgression the pattern of one minor conformable sequence boundary followed by two major unconformable sequence boundaries bears a strong resemblance to the early cretaceous sequence stratigraphy suggested in recent global cycle charts however biostratigraphical calibration of the sections is currently inadequate to allow close correlation with candidate sequence boundaries in other areas

a magnetic solution to the mupe bay mystery abstract an outcrop of wealden beds at mupe bay uk is associated with a key piece of evidence for the timing of hydrocarbon migration in the wessex basin a conglomeratic bed contains oil stained clasts and matrix that appear different upon superficial observation conventional interpretations assign differences to the erosion and transport of oil cemented clasts by wealden rivers before their incorporation into a later stained conglomeratic bed this scenario constrains the onset of oil migration in the basin to the early cretaceous however arguments have been put forward for single phase staining magnetic information may provide new ways to examine the mupe bay record of oil migration migrating fluids such as hydrocarbons have been shown to cause chemical conditions suitable for the alteration or formation of authigenic magnetite resulting in associated chemical remanent magnetization crm magnetic characterization reveals both the matrix and clasts contain multi domain magnetite but abundant hematite only exists within the clasts hysteresis parameters show the matrix has more multi domain and likely larger magnetic grains than the clasts magnetic directions are different in the clasts and matrix supporting a two phase oil staining event moreover paleomagnetic directions for the clasts after tilt correction 82 6 n and 155 2 e are consistent with biodegradation processes in the early cretaceous consistent directions in separate clasts imply the biodegradation and magnetite formation took place following transportation and incorporation of the oil cemented clasts into the conglomerate bed magnetic directions reveal that the mupe bay matrix has a remanent magnetization corresponding to today s magnetic field confirming the matrix represents an active oil seep this study represents an unprecedented use of magnetic data to date the onset of oil migration in a basin the classic two stage oil staining scenario which constrains the onset in the wessex basin to the early cretaceous is supported by our data

shear wave velocity to evaluate in situ state of cohesionless soils shear wave velocity vs measurements were carried out in a triaxial testing program on three different cohesionless soils the vs was measured using bender elements during consolidation and at ultimate steady state after consolidation the soil samples were loaded in shear under constant strain rate triaxial compression either drained or undrained to determine their ultimate steady or critical state uss at large strains the vs measurements were used to develop relationships between the void ratio e mean normal effective stress p and vs the shear loading results were expressed within the framework of critical state soil mechanics the results of the vs and uss information were combined with the state parameter concept to develop an equation to use field measured vs to estimate the in situ consolidation state within a soil thus the contractive dilative boundary with respect to vertical effective stress for large strain loading can be determined from in situ measurements of vs these can then b

can the effect of sand fabric on plastic hardening be determined using a self bored pressuremeter at working levels of strain prior to peak strength soil fabric has a large effect on the mobilized stress strain response fabric is also known to affect the number of cycles to liquefaction in loose sands better quality analyses require that the effect of fabric on plastic hardening be included in any parameter selection but measurement of this fabric effect is difficult fabric is sensitive to soil disturbance and hence is most appropriately measured in situ but the effect of density and fabric may have similar effects on in situ tests which complicates the determination of each of these independent state variables this paper investigates whether the pressuremeter an in situ test whose loading may be idealized as simple cylindrical cavity expansion is able to differentiate between the effects of density and fabric a realistic critical state constitutive soil model norsand is used for the investigation in detailed finite element simulations of pressuremeter tests resolution of the competing

penecontemporaneous oil seep in the wealden early cretaceous at mupe bay dorset u k abstract investigation of an oil globule enveloped in laminated silty clay shows that oil derived from the lias impregnated early wealden alluvial sediments penecontemporaneously and later some of the earlier oil reached the surface of the floodplain and seeped from the eroding bank of an ephemeral river lag sediment in the channel comprising debris from the oilyalluvium was invaded by later oil or oils the palaeoseep was geologically short lived relevant geochemical and petrological data and the geological context are presented process models based on fault and or water table controls on oil migration are briefly proposed

the fossil oil seep in mupe bay dorset a myth investigated abstract the story of the mupe bay boulder bed has assumed mythical proportions in the british oil industry it is supposed to demonstrate a seep which was active at the time of deposition of the lowermost wealden sandstones indicating that the lias source rocks offshore to the south had already entered the oil window at that time the boulder bed contains sandstone clasts which are apparently oil cemented in a sandstone matrix which shows lighter oil staining the boulders were obviously soft when deposited as they were deformed during deposition this study suggests that there is no difference in the maturity or source of the oils from the clasts and the host channel sand that there is no significant difference in the diagenetic sequence or in the authigenic mineral assemblage of the two sandstones the conclusion is that the clasts are not contemporaneous oil cemented boulders as previously supposed the only differences noted in this study between the clasts and their host sandstone is in their grain sizes and the degree of biodegradation of the oils this difference in biodegradation can logically be ascribed to the difference in permeability associated with the change in grain size and the resulting penetration of meteoric water the source of the oil in both of the sandstones can be correlated to the lias aromatic biological markers for thermal maturity resistant to biodegradation indicate a maturity equivalent to about 1 vitrinite reflectance or higher for both oils these conclusions remove the constraint of early wealden generation of oil previously imposed on burial history reconstructions for the timing of oil generation and migration in south dorset it is further proposed that osmington bran point lulworth cove mupe bay worbarrow bay area was the site of a large oilfield with reservoirs within the wealden and extending down to the bencliff grits and bridport sandstones of the same order of size as the wytch farm accumulation this oilfield was uplifted and breached during the erosion which followed tertiary compression

improved geohydraulic characterization of river bed sediments based on freeze core sampling development and evaluation of a new measurement approach summary prior to hydraulic engineering work it is essential to know the geohydraulic properties of river bed sediments as precisely as possible in order to predict and minimize potential effects on adjacent aquifers many different methods are available but all have limitations some destroy the natural sediment structure others lack a small scale resolution and all fail to determine anisotropy in this study we present a new measuring approach to determine hydraulic conductivity k and anisotropy at a detailed scale frozen undisturbed sediment samples taken with the freeze core technique form the basis of our approach orientated core cutter samples are taken from the freeze cores at different depths and examined by means of falling head lab permeameter tests in order to obtain detailed profiles of vertical and horizontal k values and anisotropy the approach was tested with natural sediment samples from the bed of a channel near potsdam germany and with samples from an experimental container for comparison and evaluation hydraulic conductivities were also determined by means of in situ permeameter tests and empirically on the basis of grain size distribution gsd the results show a large discrepancy between the empirically determined hydraulic conductivities and the directly measured hydraulic conductivity with lab and in situ permeameter tests we conclude that empirical methods based on gsd are not suitable for determining in situ conductivity of river bed sediments our new approach enables an improved geohydraulic characterization of river bed sediments including the determination of anisotropy

petroleum geochemistry of the lower and middle jurassic in atlantic margin basins of ireland and the uk potential hydrocarbon source rocks of lower and middle jurassic age have been reported from outcrop shallow boreholes and exploration wells in atlantic margin basins of the uk hebrides west of shetlands and flanking the ne rockall trough and recently in the continuation of this trend offshore ireland slyne erris and porcupine basins previously these organic rich mudrocks were considered to be of little economic importance due largely to their perceived limited areal distribution and low maturity however recent geochemical studies of oils and shales from exploration drilling of these basins shows the lower and middle jurassic to have considerable potential as effective hydrocarbon source rocks supplanting the late jurassic early cretaceous kimmeridge clay formation equivalents as the only viable oil source rock in the region flanking the atlantic margin in the irish and uk sectors rich oil source potential occurs in two transgressive mudrock cycles of lower jurassic age these are the sinemurian pliensbachian interval and the overlying toarcian section present in basins such as the solan minch hebrides slyne north celtic sea st george s channel and central english channel the middle jurassic source rocks have a more limited areal distribution and occur in the faroe shetland solan west lewis west flannan hebrides slyne and north porcupine basins with oil source potential in regressive marginal marine to lacustrine facies mudrocks geochemical studies were undertaken on mudrocks from the lower and middle jurassic sections in atlantic margin basins outcrop shallow borehole core and exploration well cores and cuttings samples and on oils from drill stem test and shows core and cuttings extracts detailed analyses using gc gc ms and carbon isotopes allowed both characterization of the source rocks and oil to source correlation biomarker and carbon isotope studies of oils from the faroe shetland basin foinaven and schiehallion fields the porcupine basin connemara accumulation the wessex basin wytch farm and kimmeridge oil fields and wells in the slyne basin show strong correlations to the various source rock developments in the lower and middle jurassic the mixed biodegraded foinaven and schiehallion oils have a major waxy component and correlate with lacustrine middle jurassic source rocks in the solan and west lewis west flannan basins middle jurassic sourcing of the connemara oils is also suggested while oils in the slyne basin appear to have been largely sourced by the lower jurassic pabba shale formation oils in the wessex basin wytch farm and kimmeridge appear to have been sourced by hettangian sinemurian mudrocks and those in the north celtic sea basin by toarcian source rocks the results from this study in combination with previously published data show that rich effective oil prone source rocks occur in both the lower and middle jurassic of the atlantic margin basins offshore ireland and the uk these source rocks can be correlated with indigenous oils indicating the existence of a previously under evaluated petroleum system

interpretation of in situ test results from the canlex sites one of the primary objectives of the canadian liquefaction experiment canlex project was to evaluate in situ testing techniques and existing interpretation methods as part of the overall goal to