subduction induced pore fluid venting and the formation of authigenic carbonates along the cascadia continental margin implications for the global ca cycle abstract pore fluid venting associated with subduction induced sediment deformation causes precipitation of calcium carbonate as prominent carbonate chimneys or cement in the accreted sediments across the active continental margin off oregon and washington a depletion of interstitial ca 2 with a maximum decrease of 50 relative to seawater ca 2 over only 1 5m depth and reduction in porosity in the deformed sediments suggest that interstitial ca 2 is removed to form calcium carbonate cement in contrast the pore waters of the undeformed abyssal plain sediments show no depletion in dissolved ca 2 they are either enriched to a maximum of 5 or show no change in dissolved ca 2 here the background level of caco 3 content in the sediment is only 0 1 to 1 calcium carbonate precipitation in the deformed sediments probably occurs as the result of upward migration and oxidation of biogenic methane and of the increase in carbonate saturation due to release of excess pore pressure during fluid venting upward advection of fluids at rates of 1 28 cm y 1 is predicted from diffusion advection reaction models applied to the downcore concentration profiles of dissolved ca 2 and nh 4 in the tectonically deformed sediments the range of predicted flow rates is related to the type of calcium carbonate lithification i e slow rates generate cement and fast rates generate chimneys carbonate mineral precipitation associated with pore fluid venting requires direct transfer of ca 2 from the oceanic basement to the accretionary complex such a mechanism leads us to propose that the accretionary complexes of the global plate subduction zones are a major sink for crustal ca 2 a global flux of crustal ca 2 that is removed by carbonate mineral precipitation may be as muc3 as the hydrothermal ca input this significant ca flux not previously considered in the global geochemical budget implies that pore fluid venting in subduction zones may also act as a global sink or source for other elements

the madden julian oscillation barotropic dynamics and north pacific tropical cyclone formation part i observations low level barotropic dynamics may help to explain the modulation of eastern and western north pacific tropical cyclones by the madden julian oscillation mjo during northern hemisphere summer the mjo is characterized by alternating periods of westerly and easterly 850 mb zonal wind anomalies across the tropical pacific ocean when mjo 850 mb wind anomalies are westerly small scale slow moving eddies grow through barotropic eddy kinetic energy eke conversion from the mean flow these growing eddies together with strong surface convergence 850 mb cyclonic shear and high mean sea surface temperatures create a favorable environment for tropical cyclone formation periods of strong mjo easterlies over the pacific are characterized by lesser eke and negligible eddy growth by barotropic conversion the term 2 x is a leading contributor to low level barotropic eke conversion during mjo westerly 2 u9 u periods across the pacific indicating the importance of zonal variations in the westerly jet for producing concentrations of eddy energy this mechanism can be described as wave accumulation associated with variations of the low level zonal flow the conversion term 2 y contributes a smaller portion of the total conversion u9y9 u over the eastern pacific but is of comparable importance to 2 x during westerly mjo events in the 2 u9 u western pacific

the fluid regime during fracturing of the embla field central trough north sea abstract the deep embla field located in the central trough north sea represents the first oil reservoir in paleozoic rocks to be developed on the norwegian shelf the reservoir consists of braided fluvial and alluvial fan sandstones interlayered with floodplain lacustrine mudstones and volcanics and intrusives extensive fracturing of the reservoir has led to the formation of numerous mineralised veins three main types of mineralised fractures can be identified 1 early diagenetic veins and veins which occur in and around mafic igneous rocks 2 carbonate dominated veins 3 barite clay minerals and bitumen veins this article presents fluid inclusion evidence from fracture filling minerals suggesting that the fractures were important fluid conduits of both petroleum and brine migration the petroleum inclusion data are consistent with an undersaturated oil composition a range in salinity between 23 and 12 wt nacl eq is found for the aqueous inclusions the variation in salinity indicates mixing between a high saline fluid related to evaporites and a fluid with lower salinity microthermometry data suggest that the fracturing events occurred at deep basinal levels at temperatures in excess of 100 c

structure of the musandam culmination sultanate of oman and united arab emirates and the straits of hormuz syntaxis the musandam mountains form a link both in time and space between the late cretaceous ophiolite obduction tectonics of the oman mountains and the late tertiary continental collision tectonics of the zagros fold belt of iran culmination of the musandam shelf carbonates occurred after the turonian maastrichtian thin skinned thrusting of the oman mountains was completed the basal hagab thrust cuts up section to the west from at least mid permian level up to the late cretaceous aruma group and breached up into the overlying previously allochthonous cretaceous hawasina cherts in the hagil window ras al khaimah the shelf carbonates show from 4 to 15 km of westward translation extrapolation of foreland sequences suggests that upper cretaceous aruma group and hawasina complex sediments could occur in the subsurface along the footwall east of the mountain front the hagab thrust and musandam structures plunge south southwest at increasingly greater depth and with decreasing amount of translation and carry all overlying late cretaceous thrust sheets of the oman mountains in a piggy back fashion the eocene lr oligocene pabdeh foredeep developed as a result of loading in front of the musandam thrust sheets wedging out to the south the trailing south eastern edge of the musandam culmination is a hinged listric normal fault downthrowing to the south east up to 2 5 km at bayah and less than 500 m at the western end of batha mahani and is interpreted as a dorsal culmination collapse feature

thermo chronological approach to reservoir diagenesis in the offshore angola basin a fluid inclusion 40 ar 39 ar and k ar investigation 1 microthermometric analyses of fluid inclusions and geochronological surveys of authigenic silicates in neocomian sandstones and albian dolomitic reservoirs from the offshore angola basin have allowed determination of the age and the physical chemical conditions for fluid migration in a late diagenetic stage the 40 ar 39 ar laser probe dating of adularia overgrowths from the albian reservoirs shows that the trapping of primary aqueous and oil inclusions occurred during the early miocene 25 6 or 3 2 ma the k ar age of authigenic illites from the neocomian sandstones is slightly younger 19 or 1 ma and the crystallization of regular illite smectite mixed layers is related to a previous eocene to paleocene diagenetic stage 51 58 ma there appears to have bee both a regional and vertical variation in the salinity of aqueous fluids during the miocene the fluid inclusion trapping temperatures were estimated by correcting the homogenization temperatures of aqueous fluids assuming that pressures during the miocene were close to the present reservoir pressures and by intersecting the isochores of aqueous and oil inclusions assuming they were trapped at strictly similar pressure and temperature conditions the fluid inclusion temperatures are consistent with those derived from the tetrahedral aluminum content aliv of authigenic chlorites 168 206 degrees c in the albian reservoirs at depths between 2350 and 3580 m and 175 237 degrees c in the neocomian sandstones at depths between 2770 and 4470 m in both reservoir formations miocene tempe atures were higher than the present ones and related either to deeper burial or higher geothermal gradient

petroleum migration and mixing in the northwestern junggar basin nw china constraints from oil bearing fluid inclusion analyses abstract abundant oil bearing fluid inclusions are present in four reservoir sandstone samples from the slope and fault zone areas in the northwestern margin of the junggar basin nw china free oil in intergranular pores adsorbed oil on grain surfaces and petroleum in inclusions hosted by mineral grains of these samples were analyzed by gas chromatography and gas chromatography mass spectrometry analytical results indicate similar biomarker distributions in the three bitumen fractions of the samples collected from the slope area which correlate well with characteristic of the source rocks in the lower permian fengcheng formation this is in contrast to the fault zone where the three bitumen fractions vary significantly in their geochemical signatures suggesting that all of the three permian source sequences rocks including the lower permian jiamuhe and fengcheng formations and the middle permian lower wuerhe formation have been mature and contributed to the oils in the fault zone the presence of an unresolved hydrocarbon hump and a full range of unaltered n alkanes in the gas chromatograms of samples collected from the fault zone indicate an earlier hydrocarbon biodegradation and subsequent injection of fresh oils distinctly different from that in the slope area petrographic and microthermometric investigations of oil bearing fluid inclusions suggest a single oil charge in the slope area to the lower triassic reservoir occurring during the late triassic to early jurassic time in the fault zone oil migration and mixing took place mainly during the late triassic to early jurassic and cretaceous followed by gas migration in the tertiary period the different petroleum migration and mixing histories in the slope and fault zones are attributed to the effect of fault controlled oil and gas migration

radiative dynamical consequences of dry tongues in the tropical troposphere abstract dry layers are frequently observed in atmospheric soundings from the climatologically humid western pacific warm pool region some 2400 soundings from the toga coare field program were objectively examined for humidity drops layers in which relative humidity decreases rapidly with height indicative of the bases of dry layers these occur throughout the lower and middle troposphere with frequency peaks near 550 the 0 c level 800 and 950 mb a composite constructed from these sounding data indicates the following almost all dry layers are too dry and not warm enough to be interpreted as conservative vertical displacements rather they apparently consist of filaments or tongues of low moist static energy air advected into the column often from the subtropics dry tongues are anomalously virtually warm near their bases with a slight cool layer below that is they sit atop sharp stable layers or inversions the authors hypothesize that radiation is responsible for the thermal structure o

mjo signals in latent heating results from trmm retrievals abstract four tropical rainfall measuring mission trmm datasets of latent heating were diagnosed for signals in the madden julian oscillation mjo in all four datasets vertical structures of latent heating are dominated by two components one deep with its peak above the melting level and one shallow with its peak below profiles of the two components are nearly ubiquitous in longitude allowing a separation of the vertical and zonal temporal variations when the latitudinal dependence is not considered all four datasets exhibit robust mjo spectral signals in the deep component as eastward propagating spectral peaks centered at a period of 50 days and zonal wavenumber 1 well distinguished from lower and higher frequency power and much stronger than the corresponding westward power the shallow component shows similar but slightly less robust mjo spectral peaks mjo signals were further extracted from a combination of bandpass 30 90 day filtered deep and shallow components largest amplitudes of bo

the petroleum characteristics and filling history of the froy field and the rind discovery norwegian north sea abstract the brent group reservoirs of the froy field and the rind discovery norwegian north sea show complex distributions of petroleum and aqueous fluids multiple fluid contacts are present in the rind discovery and the fields show various extent of compartmentalisation due to faulting geochemistry data of core extracts indicate that the two fields have different petroleum sources bhullar karlsen holm backer owe tran 1998 late diagenetic modifications of the reservoir quality consist of quartz cementation followed by carbonate and kaolinite cementation and dissolution of k feldspar fluid inclusion results indicate that filling of the reservoirs occurred after the main phase of quartz cementation at pressure temperature conditions close to the present differences in fluid properties between fault compartments in both fields have been identified fluid inclusion data have proved especially valuable for evaluation of the sealing capacity of faults through time and given evidence for the fault lineament north of both fields to be a time integrated pressure seal except for a lower gas condensate zone in the 25 2 13 compartment of rind the present reservoir fluids are volatile oils close to gas saturation the previous presence of an oil in the lower reservoir zone of 25 2 13 has also been demonstrated the fluid inclusion data indicate that the condensate in 25 2 13 represents a second episode of migration filling rather than phase separation

uv raman spectroscopy of hydrocarbon bearing inclusions in rock salt from the dongying sag eastern china abstract compositions of hydrocarbon bearing inclusions in rock salt halite from the shahejie formation in the dongying sag bohai bay basin eastern china have been analysed by raman spectroscopy coupled with a 244 nm uv laser source the fluorescence effect caused by the conventional visible laser excitation of the aromatic fractions of hc bearing inclusions can be effectively avoided six types of hc bearing inclusions belonging to two generations have been identified in halite according to their hydrocarbon types and petrographic characteristics the presence of hc bearing inclusions in halite provides evidence of crystal fracturing and healing plastic deformation and dynamic recrystallization of rock salt in the dongying sag this proves that rock salt may have repeatedly lost and then recovered its sealing capacity during two stages of oil emplacement water and hydrocarbons were detected by uv raman spectroscopy in the studied samples in both hc bearing inclusions and aqueous inclusions these results are important for understanding the formation conditions of these fluid inclusions and the interactions between the formation water and petroleum in reservoirs our results show that uv raman spectroscopy has a potential to become a powerful tool for analyzing hydrocarbon bearing fluid inclusions trapped in various elements of a petroleum system

hydrocarbon water interactions during brine migration evidence from hydrocarbon inclusions in calcite cements from danish north sea oil fields abstract crude oils in primary and secondary fluid inclusions in calcite from fractures in seven offshore oil fields associated with diapiric salt structures in the danish sector of the north sea were analyzed by capillary column gas chromatography and compared with crude oils produced from the same reservoirs oils from fluid inclusions in all fields show evidence of biodegradation decreased n c17 pristane and n c18 phytane ratios and loss of n c7 2 methyl hexane and 3 methyl hexane relative to methyl cyclohexane and water washing absence of benzene and depletion of toluene some oils in inclusions are extremely enriched in c6 and c7 cyclic alkanes suggesting that these samples contain hydrocarbons exsolved from ascending hotter formation waters compared to inclusion oils the produced oils are less biodegraded but are water washed indicating that both types of oil interacted with large volumes of formation water the carbon isotopic composition of the calcite host of the fluid inclusions in the dagmar and skjold fields is as light as 16 5 pdb and the sulfur isotopic composition of pyrite in and adjacent to the calcite veins in the skjold field is as light as 39 6 cdt indicating that biodegradation of the oils was a source of some of the carbon in the calcite and sulfate reduction was the source of sulfur for the pyrite the evidence for microbial degradation of petroleum is consistent with present day reservoir temperatures 65 96 c but is not consistent with previous estimates of the temperatures of calcite vein filling 95 130 c which are much higher than the temperatures of known occurrences of biodegraded oil

westerly wind bursts and their relationship with intraseasonal variations and enso part ii energetics over the western and central pacific abstract the mechanism of synoptic scale eddy development in the generation of westerly wind bursts wwbs over the western central pacific and their relationship with the el nino southern oscillation enso and the madden julian oscillation mjo were examined in the wwb occurrences barotropic structures of equatorial eddy westerlies with cyclonic disturbances were found from the surface to the upper troposphere the dominant contributions to substantial eddy kinetic energy eke were the barotropic energy conversion kmke in the lower and middle tropospheres and the conversion from eddy available potential energy peke in the upper troposphere low frequency environmental westerlies centered near the equator preceded strong zonal convergence and meridional shear resulting in the substantial kmke the activation of synoptic convection also contributed to an increase in eke through peke these energies were redistributed to the lower equatorial troposphere through energy flux convergence gke the

assessing the maturity of oil trapped in fluid inclusions using molecular geochemistry data and visually determined fluorescence colours abstract the thermal maturity of oils extracted from inclusions and the fluorescence colours of oil bearing fluid inclusions have been measured in 36 sandstone samples from australasian oil fields the inclusion oils were analysed using an off line crushing technique followed by gc ms a maturity assessment was made for each inclusion oil using 25 molecular maturity ratios including a newly defined dimethyldibenzothiophene ratio dmdr each inclusion oil was placed in one of 4 maturity brackets approximately equivalent to early mid peak and post oil generation windows the fluorescence colours of oil inclusions were visually discriminated into blue white and yellow plus orange and their proportions estimated using point counting techniques sixteen samples have 85 of oil inclusions with blue fluorescence whilst other samples have more variable fluorescence colours one sample has 100 of oil inclusions with yellow plus orange fluorescence the results show that samples containing mainly blue fluorescing oil inclusions have thermal maturities anywhere within the oil window in particular the molecular geochemical data strongly suggests that oil inclusions with blue fluorescence can have relatively low maturities calculated reflectance

hydrocarbon generation in the permian irati organic rich shales under the influence of the early cretaceous parana large igneous province abstract the increasing global demand for natural gas and petroleum byproducts is turning organic rich shales into an important target for hydrocarbon exploration and production current understanding about hydrocarbon generation in unconventional plays such as oil shales and gas shales is still evolving especially in sedimentary basins where hydrocarbon generation is influenced by magmatism this is the case for the permian oil shales of the irati formation in the parana basin southern south america the irati shales are considered an atypical petroleum system due to thermal effects of the parana large igneous province lip emplaced during the early cretaceous in this context the focus of this study was to characterize the thermal conditions of hydrocarbon generation in the irati formation as well as the composition of related aqueous diagenetic fluids the kerogen from the irati organic rich shales has an aromaticity around 30 ar 30 as determined by carbon nuclear magnetic resonance 13c nmr and vitrinite reflectance ro of around 0 6 fluid inclusions in calcite and quartz veins present aqueous fluids with salinity of 0 5 wt of nacl equivalent and homogenization temperatures greater than 250 c hydrocarbon fluid inclusions were classified as black oil through their vapor fraction volumes fv 1 6 9 1 and homogenization temperatures th in the 60 80 c range methane ch4 or carbon dioxide co2 fluid inclusions were absent within the analyzed calcite and quartz veins the pvt model for trapped fluid inclusions suggests a shallow hydrocarbon petroleum system 2 5 km depth active during the early cretaceous synchronous with the parana lip

simulation of the intraseasonal variability over the eastern pacific itcz in climate models during boreal summer convective activity over the eastern pacific epac inter tropical convergence zone itcz exhibits vigorous intraseasonal variability isv previous observational studies identified two dominant isv modes over the epac i e a 40 day mode and a quasi biweekly mode qbm the 40 day isv mode is generally considered a local expression of the madden julian oscillation however in addition to the eastward propagation northward propagation of the 40 day mode is also evident the qbm mode bears a smaller spatial scale than the 40 day mode and is largely characterized by northward propagation while the isv over the epac exerts significant influences on regional climate weather systems investigation of contemporary model capabilities in representing these isv modes over the epac is limited in this study the model fidelity in representing these two dominant isv modes over the epac is assessed by analyzing six atmospheric and three coupled general circulation models gcms including one super parameterized gcm spcam and one recently developed high resolution gcm gfdl hiram with horizontal resolution of about 50 km while it remains challenging for gcms to faithfully represent these two isv modes including their amplitude evolution patterns and periodicities encouraging simulations are also noted in general spcam and hiram exhibit relatively superior skill in representing the two isv modes over the epac while the advantage of spcam is achieved through explicit representation of the cumulus process by the embedded 2 d cloud resolving models the improved representation in hiram could be ascribed to the employment of a strongly entraining plume cumulus scheme which inhibits the deep convection and thus effectively enhances the stratiform rainfall the sensitivity tests based on hiram also suggest that fine horizontal resolution could also be conducive to realistically capture the isv over the epac particularly for the qbm mode further analysis illustrates that the observed 40 day isv mode over the epac is closely linked to the eastward propagating isv signals from the indian ocean western pacific which is in agreement with the general impression that the 40 day isv mode over the epac could be a local expression of the global madden julian oscillation mjo in contrast the convective signals associated with the 40 day mode over the epac in most of the gcm simulations tend to originate between 150 e and 150 w suggesting the 40 day isv mode over the epac might be sustained without the forcing by the eastward propagating mjo further investigation is warranted towards improved understanding of the origin of the isv over the epac

fluid flow and mass flux determinations at vent sites on the cascadia margin accretionary prism fluid venting from the toe of the accretionary prism off oregon was measured in situ during a series of dives with dsrv alvin in 1987 and 1988 a benthic chamber was placed over active vent sites to sequentially collect samples of venting fluids and to make direct measurements of discharge rates calibrated flow meter measurements and flow rates determined from dissolved methane transfer indicate that discharge from two vent sites alvin 1428 and alvin 1900 ranges roughly between 100 and 500 l m 2 d 1 with the most reliable estimates falling in the range of 125 150 l m 2d 1 these rates imply subsurface advective flow on the order of 100 m yr 1 comparison of observed discharge rates with rates calculated for steady state expulsion supported by accretion related compaction indicates that the observed flow is greater than predicted flow by several orders of magnitude the disparity dictates that fluids are not derived locally but are transported laterally within the prism or that flow is not steady state and that individual vents are short lived features in the ongoing accretion process

relationship between the fluorescence color of oil inclusions and thermal maturity in the dongying depression bohai bay basin china part 1 fluorescence evolution of oil in the context of hydrous pyrolysis experiments with increasing maturity abstract the fluorescence evolution of oils has been measured by simulation of petroleum generation and expulsion in a half closed system using hydrous pyrolysis based on four oil prone source rocks type i and ii kerogens from the dongying depression bohai bay basin china the results suggest that the fluorescence characteristics of expelled oil are independent of oil prone kerogen types but are strongly related to oil generation and expulsion processes which are controlled by thermal maturity of source rocks the fluorescence spectral parameters max q650 500 and qf 535 of expelled oils show no obvious variation or even show gradual redshifts when the highest max occurs at peak bitumen generation depending on the expulsion process a blueshift of fluorescence color occurs only during the main oil generation and expulsion stage which immediately follows the peak bitumen generation stage however the expelled oil mainly exhibits green to yellow fluorescence colors 500 nm

the intraseasonal 30 50 day oscillation of the australian summer monsoon abstract the tropical intraseasonal 30 50 day oscillation manifests itself in the australian summer monsoon by a pronounced modulation of the monsoonal westerlies these 30 50 day fluctuations of the monsoonal westerlies are coherent with rainfall and olr across northern australia the olr fluctuation originates in the indian ocean and systematically propagates eastward at 5 m s 1 consistent with previous studies of the intraseasonal oscillation the detailed evolution of the intraseasonal oscillation of the monsoon is studied via composites of upper air data in and about the australian tropics during the summer periods 1957 87 91 events were identified at darwin australia the composite oscillation at darwin has a very deep baroclinic structure with westerlies extending up to 300 mb the westerly phase lasts about ten days and lags a similar duration rainfall event by about four days during the westerly phase the upper troposphere is warm and the extreme lower troposphere is cool this structure

hydrocarbon bearing fluid inclusions in calcite filled horizontal fractures from mature posidonia shale hils syncline nw germany abstract hydrocarbon bearing fluid inclusions in calcite filled horizontal fractures from mature posidonia shale 0 88 r o were investigated by microscopic microthermometric and chemical methods the fluid inclusions predominantly contain both a liquid hydrocarbon phase which shows bright uv fluorescence colours yellow brownish light blue and a non fluorescent hydrocarbon gas phase the different uv fluorescence colours probably reflect the different gross chemical compositions of the trapped liquid hydrocarbons the saturated hydrocarbon fraction of the fluid inclusions mostly secondary inclusions predominantly consists of low molecular weight n alkanes c 9 c 12 while c 12 c 22 n alkanes are more abundant in the adjacent rock matrix the molecular composition of the fluid inclusions appears to reflect a mobile hydrocarbon phase which was entrapped within the calcitic fill of the horizontal fractures pressure corrected trapping temperatures were estimated for primary fluid inclusions 123 162 c this temperature range is in agreement with the results from numerical simulation studies which indicate a maximum temperature of 148 c coinciding with the period of fracture formation calcite filling and entrapment of primary fluid inclusions

satellite observations of the wind jets off the pacific coast of central america part i case studies and statistical characteristics measurements of near surface winds by the nasa scatterometer nscat from october 1996 through june 1997 are analyzed to investigate the three major wind jets along the pacific coast of central america that blow over the gulfs of tehuantepec papagayo and panama each jet is easily identifiable as locally intense offshore winds in the lee of low elevation gaps through the sierra madre mountain range the jets have relatively narrow cross stream width but often extend several hundred kilometers or more into the pacific the tehuantepec and papagayo jets sometimes merge with the northeast trade winds of the pacific the tehuantepec jet was highly energetic with characteristic timescales of about 2 days events were triggered by high pressures associated with cold surges into the gulf of mexico that originated over the great plains of north america the papagayo and panama jets were much more persistent than the tehuantepec jets the winds at both of these lower latitude locations exhibited a strong seasonal variation with almost exclusively offshore flow from late november 1996 through late may 1997 and periods of onshore flow in october and november during the late stages of the 1996 central american monsoon season superimposed on this low frequency seasonal variation were events with characteristic timescales of a few days based on nscat data the spatial and temporal evolution of major wind events is described in detail for three representative case studies in december 1996 the jets developed sequentially from north to south consistent with the notion that wind events in the two lower latitude jets are associated with cold air outbreaks that trigger the tehuantepec jet a day or so earlier in november 1996 and march 1997 the papagayo and panama jets were strongly influenced by tropical phenomena that had little apparent association with the tehuantepec jet these latter two case studies together with the distinction between the statistical characteristics of the three jets suggest that the papagayo and panama jets are predominantly controlled by a mechanism that is very different from the across gap pressure gradients associated with high pressure systems of midlatitude origin that control the tehuantepec jet

surface fluxes and ocean coupling in the tropical intraseasonal oscillation abstract sensitivity of tropical intraseasonal variability to mixed layer depth is examined in the modified national center for atmospheric research community atmosphere model 2 0 1 cam with relaxed arakawa schubert convection coupled to a slab ocean model som whose mixed layer depth is fixed and geographically uniform but varies from one experiment to the next intraseasonal west pacific precipitation variations during boreal winter are enhanced relative to a fixed sst infinite mixed layer depth simulation for mixed layer depths from 5 to 50 m with a maximum at 20 m interestingly near the observed value in the regions where the madden julian oscillation mjo is active but are strongly diminished in the 2 m depth simulation this nonmonotonicity of intraseasonal precipitation variance with respect to mixed layer depth was predicted by sobel and gildor using a highly idealized model further experiments with the same idealized model help to interpret results derived from the modified ncar c

energetics of east pacific easterly waves during intraseasonal events abstractthe background atmospheric state of the east pacific warm pool in which easterly waves develop varies dramatically on intraseasonal time scales east pacific intraseasonal variability is well known to modulate local convective and circulation patterns westerly easterly intraseasonal phases are associated with westerly easterly low level wind and positive negative convective anomalies this study investigates the perturbation available potential energy pape and perturbation kinetic energy pke budgets of easterly waves composited during westerly easterly and neutral intraseasonal phases respectively the mechanisms magnitudes locations and vertical structures of easterly waves are shown to strongly vary as a function of intraseasonal phase easterly waves draw energy from low level barotropic conversion regardless of phase although the location and magnitude of the conversion varies strongly during neutral and westerly intraseasonal phases the generation of pape associated with

the interaction of planetary scale tropical easterly waves with topography a mechanism for the initiation of tropical cyclones abstract the interaction of a basic state flow consisting of a planetary scale easterly wave superimposed on a uniform easterly zonal wind with an isolated topographic feature is examined by numerical integration of the shallow water equations in an equatorial beta plane channel the topographic parameters are chosen to represent the sierra madre mountains of mexico the zonal wavelength and phase speeds of the basic state easterly waves are chosen to correspond with previously published observations the topographic modification of a slow rossby mode in which the basic state vorticity maximum is located near 15 latitude is characterized by the generation of a cyclonic vorticity maximum in the lee of the mountain which extends the entire length of the ridge and a secondary maximum which propagates downstream a fast mixed rossby gravity mode in which the vorticity maximum is located at the equator interacts less strongly with the mountain with a lee vorticity maximum that is confined near the southern

influence of the madden julian oscillation and caribbean low level jet on east pacific easterly wave dynamics abstractthe east pacific warm pool exhibits basic state variability associated with the madden julian oscillation mjo and caribbean low level jet cllj which affects the development of easterly waves ews this study compares and contrasts composite changes in the background environment eddy kinetic energy eke budgets and ew tracks during mjo and cllj events while previous studies have shown that the mjo influences jet activity in the east pacific the influence of the mjo and cllj on the east pacific and ews is not synonymous the cllj is a stronger modulator of the itcz than the mjo while the mjo has a more expansive influence on the northeastern portion of the basin anomalous low level westerly mjo and cllj periods are associated with favorable conditions for ew development paralleling the central american coast contrary to previous findings about the relationship of the cllj to ews easterly mjo and cllj periods support enhanced itcz ew development although the cllj is a greater modulato

mjo related sst variations over the tropical eastern pacific during northern hemisphere summer abstract the madden julian oscillation mjo significantly modulates eastern tropical pacific sea surface temperatures ssts during northern hemisphere summer typical sst variations during an mjo life cycle are 0 4 0 5 c considerably higher variations occur with the strongest events 1 2 c the magnitudes of these variations are comparable to those associated with west pacific mjo variability during nh winter sst anomalies to the north of 4 n where the strongest modulation of east pacific convection by the mjo occurs are 180 out of phase with equatorial anomalies these sst variations are responsible for variations in surface saturation equivalent potential temperatures of greater than 3 c the highest ssts lead maximum convection by about 10 days and ssts begin to cool with the onset of enhanced convection off equatorial sst anomalies are most likely due to variations in surface latent heat flux although shortwave flux anomalies are important in the heart of the mjo convective region decrea

petroleum inclusions in sedimentary basins systematics analytical methods and applications abstract fluid dynamics in sedimentary basins is of tremendous interest both from a scientific and an economic point of view integration between fluid inclusion and present day fluid data provides the time aspect necessary for reconstruction of fluid flow paths and can be used for mapping fluid dynamics both on a regional basin scale or on the more local scale of petroleum reservoirs this paper presents a review of analytical and modelling methods for petroleum in fluid inclusions essentially four types of data for petroleum inclusions can be established through analysis and modelling 1 textures which give indirect information of the time aspect 2 fluid composition 3 fluid properties and 4 pressure temperature of trapping during the last decade development of analytical methods for determination of inclusion fluid compositions has taken place traditional correlation studies for characterisation of maturity and source facies may now therefore include fluid inclusion data the development has also been directed towards an improved understanding of the physical properties of petroleum inclusions although these methods are in their early stages concerning precision and accuracy data necessary for fluid flow modelling such as fluid densities viscosities pressure and temperature can be estimated

the amplification of east pacific madden julian oscillation convection and wind anomalies during june november abstract madden julian oscillation mjo wind and convection anomalies are locally amplified over the northeast pacific warm pool during june november composite analysis using ncep reanalysis data indicates that perturbation available potential energy pape production through the positive correlation of intraseasonal temperature and convective diabatic heating anomalies supports the local intensification of mjo related east pacific warm pool wind anomalies pape production is maximum during periods of strong mjo convection and low level westerly wind perturbations pape is converted to perturbation kinetic energy through positive correlations between intraseasonal temperature and vertical velocity microwave sounding unit msu temperature and noaa outgoing longwave radiation data support the energy budget results derived from ncep reanalysis the amplified east pacific circulation enhances surface convergence and latent heat flux anomalies during mjo convective periods the surface convergence anomalie

the madden julian oscillation observed during the toga coare iop global view abstract during the toga coare intensive observing period november 1992 february 1993 two pronounced madden julian oscillation mjo events associated with super cloud clusters and westerly wind bursts were observed this paper presents a global view of the mjos including the origin of the super clusters in the indian ocean their migration into the maritime continent and the toga coare large scale soundings array lsa in the western equatorial pacific and their rapid decay over cold water of the eastern pacific the structure and evolution of the mjo are examined with emphasis on the coupling between large scale motion and convection because of differences in propagation speeds the positions of maximum zonal wind perturbations relative to deep convection undergo systematic changes during the travel of the mjo however the centers of deep convection always coincide with those of large scale ascent the super cloud cluster accompanies a wide area of warm air in the upper troposphere over the warm

synthetic saline aqueous and hydrocarbon fluid inclusions trapped in calcite at temperatures and pressures relevant to hydrocarbon basins a reconnaissance study abstract we conducted reconnaissance experiments to synthesize aqueous and hydrocarbon inclusions trapped in calcite at conditions relevant to petroleum basins and characterize the microthermometric properties of such inclusions fluid inclusions fis were synthesized in a system of saline aqueous solution 5 or 20 wt nacl coexisting with either heavy crude oil or gasoline under gas undersaturated conditions from 90 to 210 c and 200 550 bar the synthetic inclusions are not representative of gas bearing systems and methane ch 4 was not detected in any aqueous inclusions the fis are mainly distributed along planar healed cracks indicating that the inclusions formed by fracture healing in the calcite crystal microthermometric measurements were conducted on coeval aqueous and hydrocarbon inclusions and raman spectroscopic analyses were done on aqueous inclusions to determine the properties of fis trapped at these conditions homogenization temperatures of synthetic fis are mostly lower than the experimental trapping temperature although the fis show high variability in measured homogenization temperature results allow comparison of t h values for each sample with the expected t h isochores and pressure corrections calculated for the system h 2 o nacl the latter parameters are broadly consistent with the known pvtx properties of h 2 o nacl fluids suggesting little effect of hydrocarbons on the homogenization behavior although the low precision of the t h data limits this assessment nevertheless this result is not unexpected considering that light hydrocarbons gas is not present in the experiments as corroborated by raman spectroscopy a consequence of using dead oil in the experiments simulation of gas bearing petroleum basins will require additional protocols for producing gas either by in situ cracking of the starting hydrocarbon material or by other means the reconnaissance experiments documented here provide a basis for such future experiments

the onset of convection in the madden julian oscillation abstract an observational study of the onset of convection in the madden julian oscillation mjo was performed composites of radiosonde data from the comprehensive aerological reference data set were constructed for an ensemble of tropical stations located in the indian ocean maritime continent and western pacific ocean the composites suggest that for the off equatorial stations used in this study the mjo period may be set by the buildup and discharge of the low level moist static energy this result supports the discharge recharge hypothesis of blade and hartmann mjo events appear to begin when the off equatorial atmosphere has been destabilized through a combination of low level moist static energy buildup and concurrent drying of the middle troposphere by subsidence in the wake of the previous cycle of mjo convection the low level moist static energy buildup is controlled by a corresponding increase in low level moisture the increase in low level moisture is not caused by the 1000 mb convergen

modulation of eastern north pacific hurricanes by the madden julian oscillation abstract hurricane and tropical storm statistics verify the modulation of eastern pacific tropical systems by the madden julian oscillation mjo as hypothesized by maloney and hartmann over twice as many named tropical systems hurricanes and tropical storms accompany equatorial 850 mb westerly anomalies than accompany equatorial easterly anomalies and the systems that do exist are stronger hurricanes are over four times more numerous during westerly phases of the mjo than during easterly phases the current study constructs a composite life cycle of the mjo during may november 1979 95 using an index based on the 850 mb equatorial zonal wind equatorial kelvin waves propagating eastward from convective regions of the western pacific ocean alter dynamical conditions over the eastern pacific ocean westerly easterly equatorial 850 mb wind anomalies are accompanied by enhanced suppressed convection over the eastern pacific hurricane region convection locally amplifies the wind anomalies over the ea

cretaceous flexural history of northern oman mountain foredeep united arab emirates an important feature of the middle cretaceous arabian continental margin was the regional upwarping in the foreland of the northern oman mountains we interpret this upwarp as an early expression of a cratonward migrating peripheral swell associated with the emplacement of the semail ophiolite onto the margin subsurface stratigraphic data indicate that the swell was expressed during the cenomanian and attained its maximum relief during the turonian by the santonian further downflexure of the margin took place around an axis west of the study area burying the then inactive turonian swell beneath the deposits of the westward expanding foreland basin we suggest that establishment of the later more cratonward flexural regime took place abruptly rather than as a continuo sly migrating wave the middle cretaceous swell axis paralleled the present day axis of the oman mountains the upwarp was slightly asymmetric to the east and loosely constrained estimates of its width and height are 150 km and 244 93 mi and 800 ft respectively the dimensions suggest an anomalously low flexural rigidity 1022 n m for the middle cretaceous continental lithosphere we attribute this low apparent rigidity to the combined effects of remnant thermal and mechanical processes of an earlier rifting event and compression of the margin during the cretaceous emplacement of the semail ophiolite the small dimensions of the middle cretaceous swell suggest that other continental margins with similar geologic histories may also have narrow extinct swells buried beneath foreland deposits such swells may have significant impact on the entrapment of hydrocarbons as we propose for the sajaa margham trend

fluid inclusion petrography and tectonic burial history of the al ali no 2 well evidence for the timing of diagenesis and oil migration northern oman foredeep cores cut in shallow marine lower and middle cretaceous carbonates in the al ali no 2 well umm al qaiwain united arab emirates display a five stage sequence of calcite cementation fracturing and stylolitization these stages are correlated with the tectonic history of the northern oman orogeny occurrence of fluorescent hydrocarbon fluid inclusions is restricted to stage 2 and stage 3 fracture filling calcites that are crosscut by stylolites stylolite formation during rapid burial beneath abyssal campanian foredeep sediments restricts hydrocarbon migration to post mid cenomanian and pre mid campanian time

on the role of sea surface temperature gradients in forcing low level winds and convergence in the tropics abstract we examine the importance of pressure gradients due to surface temperature gradients to low level p 700 mb flow and convergence in the tropics over time scales 1 month the latter plays a crucial role in determining the distribution of cumulonimbus convection and rainfall our approach is to consider a simple one layer model of the trade cumulus boundary layer wherein surface temperature gradients are mixed vertically consistent with ecmwf analyzed data the top of the layer is taken at 700 mb the influence from higher levels is intentionally suppressed by setting horizontal pressure gradients and frictional stresses to zero at the top of the layer horizontal convergence within the layer is taken up by cumulonimbus mass flux however the development of the cumulonimbus mass flux is associated with a short relaxation time o hr roughly the development time for such convection during this short time horizontal convergence acts to redistribute mass so as to reduce horizontal pressur

variability in the southerly flow into the eastern pacific itcz abstract during boreal summer and fall there is a strong southerly boundary layer flow across the equator into the east pacific intertropical convergence zone itcz the modulation of this flow on synoptic to seasonal time scales is studied using an index of meridional pressure difference between the equator and the itcz along 95 w two complementary datasets from the east pacific investigation of climate epic are used to study eastern pacific variability daily measurements of sea level pressure slp from tropical atmosphere ocean toa array buoys from may to november 2001 provide temporal coverage and eight flights by a c 130 aircraft during september to october 2001 document the associated modulation of lower tropospheric vertical structure the principal mode of variability of the perturbation slp along 95 w from 1 s to 12 n derived by principal component analysis from either the eight flights pc1c 130 or from daily tao buoy observations pc1 explains 77 of the meridional pressure gradien

reply to comment by oxtoby on assessing the maturity of oil trapped in fluid inclusions using molecular geochemistry data and visually determined fluorescence colours the authors welcome the opportunity to respond to some of the comments of oxtoby 2002 regarding their recent paper george et al 2001 we will respond to the two main topics that have been raised by oxtoby 2002 firstly the petrological procedures used and secondly the possible causes for the wide maturity range of blue fluorescing oil inclusions the issue of the relationship of fluorescence colour and api gravity raised by oxtoby 2002 was not discussed in the paper

diagenesis of the palaeo oil water transition zone in a lower pennsylvanian carbonate reservoir constraints from cathodoluminescence microscopy microthermometry and isotope geochemistry abstract oil water transition zones in carbonate reservoirs represent important but rarely studied diagenetic environments that are now increasingly re evaluated because of their potentially large effects on reservoir economics here data from cathodoluminescence and fluorescence microscopy isotope geochemistry microthermometry and x ray tomography are combined to decipher the diagenetic history of a 5 m long core interval comprising the oil water transition zone in a lower pennsylvanian carbonate reservoir the aim is to document the cementation dynamics prior during and after oil emplacement in its context of changing fluid parameters intergrain porosity mean values of 7 are present in the upper two sub zones of the oil water transitions zone but values sharply increase to a mean of 14 in the lower sub zone grading into the water saturated portions of the reservoir and a very similar pattern is observed for permeability values in the top of the water filled zone cavernous porosity with mean values of about 24 is found carbonate cements formed from the earliest marine to the late burial stage five calcite ca 1 through 5 and one dolomite dol phase are recognized with phase ca 4b recording the onset of hydrocarbon migration carbon and oxygen cross plots clearly delineate different paragenetic phases with ca 4 representing the most depleted 13c ratios with mean values of about 21 during the main phase of oil emplacement arguably triggered by far field alpine tectonics carbonate cementation was slowed down and eventually ceased in the presence of hydrocarbons and corrosive fluids with temperatures of 110 140 c and a micro hiatal surface formed in the paragenetic sequence these observations support the oil inhibits diagenesis model the presence an earlier corrosion surface between phase ca 3 and 4 is best assigned to initial pulses of ascending corrosive fluids in advance of hydrocarbons the short lived nature of the oil migration event found here is rather uncommon when compared to other carbonate reservoirs the study is relevant as it clearly documents the strengths of a combined petrographic and geochemical study in order to document the timing of oil migration in carbonate reservoirs and its related cementation dynamics

hydrocarbon migration and accumulation of the suqiao buried hill zone in wen an slope jizhong subbasin bohai bay basin china abstract the hydrocarbon migration and accumulation of the suqiao deep buried hill zone in the jizhong subbasin the bohai bay basin eastern china was investigated from the perspective of paleo fluid evidence by using fluid inclusions quantitative fluorescence techniques qgf total scanning fluorescence method tsf and organic geochemical analysis results show that the current condensate oil gas reservoirs in the study area once were paleo oil reservoirs in addition the reservoirs have experienced at least two stages of hydrocarbon charge from different sources and or maturities during the deposition of the oligocene dongying formation ed the deep ordovician reservoirs were first charged by mature oils sourced from the lacustrine shale source rocks in the fourth member of shahejie and kongdian formations es4 ek and then adjusted at the end of ed period subsequently by virtue of the tectonic movement since the deposition of the neogene minghuazhen formation nm the reservoirs were mainly charged by the gas that consisted of moderate to high maturity condensate and wet gas sourced from the es4 ek lacustrine shale source rocks and mature coal derived gas sourced from the carboniferous permian c p coal bearing source rocks meanwhile the early charged oil was subjected to gas flushing and deasphalting by the late intrusion of gas the widely distributed hydrocarbon inclusions the higher qgf index and foi the frequency of oil inclusions values in both gas oil and water zone are indicative of early oil charge in addition combined with the homogenization temperatures of the fluid inclusions

a geologic deconstruction of one of the world s largest natural accumulations of co2 moxa arch southwestern wyoming geologic sequestration of anthropogenic carbon dioxide co2 is one of the most promising approaches to safely and effectively reduce emissions of co2 created through the oxidation of fossil fuels methods used by the petroleum industry in the characterization of hydrocarbon accumulations can be used to assess potential subsurface traps for sequestration purposes in this article we use these approaches to evaluate the characteristics of a naturally occurring accumulation of co2 in western wyoming the moxa arch is a 200 km 124 mi long basement involved anticline the mississippian madison formation and the ordovician bighorn dolomite contain the most co2 within the structure relict anhydrite in these and other paleozoic units was an important factor in evolving hydrocarbons into co2 through inorganic thermal sulfate reduction and more importantly in creating a seal to hold large columns of buoyant gas fluid inclusion data sets have been particularly useful in understanding the sealing characteristics of the units within the moxa arch and affirming that the devonian jefferson mississippian amsden and triassic dinwoody and woodside formations have been very effective seals existing pressure data reveal that the two gas columns in the madison and bighorn formations lie on a similar gradient and share a common gas water contact yet are likely not in hydraulic communication currently all available data suggest that both reservoirs share a fault dependent spill point by reconciling the spill points of the gas in the madison and bighorn reservoirs their compositions their initial and current pressures their seal and the uncertainties associated with injection of co2 can be identified and potentially derisked with additional information if the madison and bighorn are filled to their fault dependent spill point it implies that additional storage capacity in the reservoir can only be obtained by production of the original gas column this uncertainty may be abated if data from future drilling demonstrates that neither the madison formation nor the bighorn dolomite have a fault dependent spill point suggesting that these structures are underfilled with respect to their closure and possess additional storage capacity

dynamics of fluid inclusion alteration in sedimentary rocks a review and discussion abstract fluid inclusions represent small volumes of interstitial fluids in crystal imperfections flaws during crystal growth and or deformation the entrapped fluids are commonly believed to preserve information on the composition pressure and temperature of fluid inclusion formation and later diagenetic alterations it is now known that fluid inclusions can be dynamic structures responsive to thermal and tectonic stresses by plastic and brittle deformation of the entrapping mineral wall these dynamic responses may include both morphologic and volumetric changes a comparison of measured fluid inclusion homogenization temperatures with sample burial depths for diagenetic studies from around the world show a strong positive correlation this correlation suggests that fluid inclusion stretching which results in increased homogenization temperatures is a common phenomenon associated with burial diagenesis burial diagenesis shifts and spreads the measured homogenization temperatures towards maximum burial conditions confining mineralogy shape size and composition of the fluid inclusions are important factors in determining the mode and degree of fluid inclusion deformation stretching classical fracture mechanics theory of predicts that plastic and brittle deformation of the surrounding mineral crystall will occur with burial and that annealing retrograde stretching of the strain in the inclusion walls will not occur in low temperature regimes experimental theoretical and field studies all indicate that fluid inclusions will react dynamically to burial diagenesis by increases in measured homogenization temperatures with increased burial it is suggested that this relationship can be selectively used to help determine the approximate maximum thermal exposures experienced by a sedimentary rock

on the convective coupling and moisture organization of east pacific easterly waves abstractprocesses associated with the local amplification of easterly waves ews in the east pacific warm pool are explored developing ews favor convection in the southwest and northeast quadrants of the disturbance in nascent ews convection favors the southwest quadrant as the ew life cycle progresses convection in the northeast quadrant becomes increasingly prominent and southwest quadrant convection wanes the ew moisture budget reveals that anomalous meridional winds acting on the mean meridional moisture gradient of the itcz produce moisture anomalies supportive of convection in the southwest quadrant early in the ew life cycle as ews mature moisture anomalies on the poleward side of the ew begin to grow and are supported by the advection of anomalous moisture by the mean zonal wind in the southwest and northeast portions of the wave where convection anomalies are favored lower tropospheric vorticity is generated locally through vertical stretching that supports a horizontal tilt of the wav

planetary and synoptic scale influences on eastern pacific tropical cyclogenesis abstract the structure and evolution of lowpass filtered background flow and synoptic scale easterly waves were examined during the 1991 eastern pacific hurricane season active and inactive cyclogenesis periods conformed well to the sign of the near equatorial lowpass filtered 850 mb zonal wind anomaly consistent with the recent results of maloney and hartmann this behavior emphasizes the importance of westerly wind bursts associated with the madden julian oscillation mjo in creating an environment favorable for eastern pacific tropical cyclogenesis synoptic scale easterly waves reached the western caribbean and eastern pacific regularly from upstream usually from africa the amplitude of waves leaving africa had little correlation with the likelihood of a wave producing an eastern pacific storm rather easterly waves intensified and tropical depressions formed during the convectively active phase of the mjo in the western caribbean and eastern pacific wave growth measured by strengthening o

frictional moisture convergence in a composite life cycle of the madden julian oscillation abstract a composite life cycle of the madden julian oscillation mjo is constructed using an index based on the first two eofs of the bandpass filtered 20 80 days 850 mb zonal wind averaged from 5 n to 5 s every 2 5 around the equator precipitation 1000 mb convergence 850 mb wind and 200 mb wind are composited for the period 1979 95 water vapor integrated from the surface to 300 mb is composited for the period 1988 92 frictional moisture convergence at the equator is shown to play an important role in the life cycle of the madden julian oscillation mjo regions of boundary layer convergence foster growth of positive water vapor anomalies to the east of convection this convergence coincides with 850 mb easterly wind anomalies as is consistent with kelvin wave dynamics drying of the atmosphere occurs rapidly after the passage of convection with the onset of 850 mb westerly perturbations possible mechanisms for this drying include boundary layer divergence and subsidence or horizontal advect

paleotemperatures from fluid inclusions advances in theory and technique fluid inclusions in diagenetic minerals can be used to determine paleotemperatures three sets of observations are necessary to make accurate interpretations 1 detailed petrography to establish the relative time of formation of the inclusions 2 careful analysis of the burial and tectonic history of the host rocks to tie diagenesis to the geologic history of the basin and finally 3 analysis of the phase behavior and chemical composition of individual inclusions to define the pressure volume temperature pvt properties of the trapped fluids

basin evaluation using burial history calculations an overview burial history calculations available to the petroleum geologist include plots of burial history and geohistory porosity and conductivity as a function of depth and lithology as well as the results obtained from algorithms to handle unconformities and backstripped crustal subsidence calculations that predict the breakdown of kerogen to hydrocarbons in terms of time and temperature and methods for determining heat flow from geologic models and vitrinite reflectance data inputs required for these calculations include depths of formation tops ages of formation tops lithologies of formations depths of water at deposition of the different formations porosities of the formations as a function of depth bottom hole temperatures and or formation temperatures and any ke ogen content and vitrinite reflectance values as functions of depth sources of many of these data may be well logs well reports geologic papers and or seismic sections the paper considers how parameters can be extracted from burial history calculations to construct maps that can be compared to the current locations of oil and gas fields and so used to locate and rank prospective acreage these parameters include the potential source rock maturity of a formation plotted as a function of time and depth the thermal history of any hydrocarbons associated with the potential source rock the rate of sediment accumulation of a formation as a function of time and subsidence rate of a formation as a function of time subsidence rate includes total subsidence compaction induced subsidence isostatic response to sediment load and backstripped crustal subsidence total subsidence minus the effects of compaction and isostatic response

the permian hybrid petroleum system in the northwest margin of the junggar basin northwest china in this paper we define the concept of a hybrid petroleum system for the permian petroleum system in the northwest margin of the junggar basin by documenting the complexity in its formation and evolution it is termed hybrid because there are three source rock sequences seven reservoir caprock combinations and three petroleum events and multiple source rocks source the same reservoir and the same source rocks also feed multiple reservoirs the mahu sag centre is the petroleum source area with three sets of source rocks dark shale of the lower permian jiamuhe formation black shale of the lower permian fengcheng formation and black shale of the middle permian lower wuerhe formation the reservoir rocks include volcanic and clastic rocks of upper carboniferous to lower cretaceous age mainly characterized by alluvial conglomerate and sandstone there are three sets of ultimate caprocks among which the mudstone of the upper triassic baijiantan formation is the most important due to its wide distribution throughout almost the whole northwest margin and greatest thickness up to 300 m whereas the lower jurassic and lower cretaceous mudstone acts as an effective seal oil and gas were generated mainly during the middle late permian late triassic and middle jurassic early cretaceous the reconstruction of the oil filling history shows that the three source rocks charged reservoirs mainly in three geologic intervals with common mixing of oils from different sources and or with different maturities these three hydrocarbon charges coincide with the three main stages of petroleum generation related to the hercynian indosinian and yanshannian orogenies during these three petroleum events oil and gas migrated along the migration framework controlled by faults unconformities and good permeability reservoir rocks the faults are mainly well developed and episodically active thrust faults and secondary faults as a result the permian petroleum system in the northwest margin of the junggar basin is hybrid

an intraseasonal oscillation composite life cycle in the ncar ccm3 6 with modified convection abstract the ncar ccm3 6 with microphysics of clouds with relaxed arakawa schubert convection produces an intraseasonal oscillation that is highly dependent on lower tropospheric moistening by surface convergence model intraseasonal convection is most highly correlated with surface convergence at zero lag causing enhanced convection to be associated with 850 mb easterly anomalies where surface convergence is strongest the tendency for surface convergence to maximize within 850 mb easterly anomalies is consistent with meridional frictional convergence into equatorial surface pressure troughs associated with planetary scale tropical wave circulations anomalous vertical advection associated with meridional surface convergence influences model convection by moistening the lower troposphere observed madden julian oscillation mjo convection and lower tropospheric specific humidity are also significantly correlated with surface convergence although correlations are weaker than in the model and converge

quantitative fluorescence techniques for detecting residual oils and reconstructing hydrocarbon charge history abstract two new fluorescence techniques quantitative grain fluorescence qgf and quantitative grain fluorescence on extract qgf e can detect palaeo oil zones and current residual oil zones in petroleum wells respectively qgf and qgf e measure the fluorescence emission spectra of trace fluorescence from reservoir grains and their extracts qgf is measured on dry disaggregated reservoir grains after a cleaning procedure involving solvent hydrogen peroxide and acid whereas qgf e is measured on the solvent extract from the qgf cleaned grains palaeo oil zones have distinct qgf spectra with spectral peaks between 375 and 475 nm and elevated fluorescence intensities compared with spectra for rocks that have always been water saturated current and residual oil zones have distinct qgf e spectra with spectral peaks at around 370 nm and elevated qgf e intensities compared with that for current water zones both qgf and qgf e responses increase upwards from the palaeo oil water and residual oil water contacts respectively an oil producing well from timor sea nw australia was investigated in detail using the qgf and qgf e techniques to illustrate how they can be used to reconstruct hydrocarbon migration history

intraseasonal behavior of clouds temperature and motion in the tropics abstract the spectral character of tropical convection is investigated in an 11 yr record of outgoing longwave radiation from the advanced very high resolution radiometer to identify interaction with the tropical circulation along the equator in the eastern hemisphere the space time spectrum of convection possesses a broad peak at wave numbers 1 3 and eastward periods of 35 95 days significantly broader than the dynamical signal of the madden julian oscillation mjo this quasi discrete convective signal is associated with a large scale anomaly that propagates across and modulates time mean or climatological convection over the equatorial indian ocean and western pacific outside that region the convective signal is small even though under amplified conditions coherence can be found east of the date line and in the subtropics having a zonal scale of approximately wavenumber 2 anomalous convection propagates eastward at some 5 m s 1 and suppresses as well as reinforces climatological convection

the application of fluid inclusions to migration of oil and diagenesis in petroleum reservoirs abstract fluid inclusions can be used to interpret thermal history and petroleum maturation and migration relative to burial history temperature pressure and composition data collected from fluid inclusions are used to determine the environment of diagenesis and the timing of cementation and migration cements in petroleum reservoirs contain both oil and aqueous fluid inclusions fluorescence spectroscopy is used to identify oil inclusions and to determine the maturity of entrapped oil the lifetime of fluorescence induced by a pulsed laser is related to the api gravity of entrapped oil interpretation of fluid inclusion data depends on knowing the origin of fluid inclusions and the probability that they survive in the burial environment those aspects of fluid inclusion study are investigated by synthesizing oil and aqueous inclusions in calcite crystals in laboratory experiments examples of how fluid inclusions are used to determine the physico chemical environments of diagenesis in petroleum reservoirs and the timing of cementation and migration are given for the wealden basin england the mishrif formation dubai the smackover formation gulf coast u s a and jurassic sandstones offshore norway in the wealden basin temperature data from fluid inclusions are used to determine that oil migration occurred in the cretaceous and that the reservoir rocks have been uplifted to varying degrees at a time after migration distribution of oil inclusions indicates that generation and migration of oil was principally in the western part of the basin the geochemistry of oil inclusions in calcite cements from the mishrif formation dubai are used to determine the type and maturity of entrapped oil temperature data from oil and water inclusions are used to relate reservoir diagenesis to burial history and the migration of oil in deep smackover reservoirs oil contains h 2 s the origin of the h 2 s is examined by study of fluid inclusions containing h 2 s in jurassic sandstones offshore norway fluid inclusion studies show that silica cementation is related to burial depth whereas a later calcite cementation originated from invasion of a hot fluid

high temperature diagenesis in shallow chalk reservoir skjold oil field danish north sea evidence from fluid inclusions and oxygen isotopes samples of calcite filled fractures from the chalk reservoir of the skjold oil field were studied by fluorescence microscopy cathodoluminescence microscopy fluid inclusion microthermometry and oxygen and carbon stable isotope and trace element analyses two generations of calcite infilling are tentatively related to two major phases of faulting caused by salt movements owing to recrystallization of the first generation of infillings the chemical isotopic and fluid inclusion data only apply to the later generation results of the fluid inclusion studies suggest a precipitation temperature of the infilling calcite significantly above what it should be applying today s geothermal gradient 52 c km or 2 85 f 100 ft to the past this higher temperature indic tes that hot water ascending from deeper strata may have flushed the reservoir apparently during a late miocene to pliocene faulting phase when ring faults guided the water to the reservoir this feature may be typical of most chalk reservoirs in the danish central graben where diapirs have penetrated the chalk

the midsummer drought over mexico and central america abstract the annual cycle of precipitation over the southern part of mexico and central america exhibits a bimodal distribution with maxima during june and september october and a relative minimum during july and august known as the midsummer drought msd the msd is not associated with the meridional migration of the intertropical convergence zone itcz and its double crossing over central america but rather with fluctuations in the intensity and location of the eastern pacific itcz during the transition from intense to weak weak to intense convective activity the trade winds over the caribbean strengthen weaken such acceleration in the trade winds is part of the dynamic response of the low level atmosphere to the magnitude of the convective forcing in the itcz the intensification of the trade winds during july and august and the orographic forcing of the mountains over most of central america result in maximum precipitation along the caribbean coast and minimum precipitation along the pacific

relationship between the location of chemosynthetic benthic communities and geologic structure on the cascadia subduction zone chemosynthetic benthic communities which live symbiotically with microbes capable of metabolizing nutrients dissolved in water seeping out of the seafloor are widespread along the cascadia subduction zone these seeps and vents are therefore indicative of one mode of fluid migration out of the subduction zone sediments the authors have used deep towed seismic methods including hydrophones mounted on alvin to examine the detailed geologic structure under two of these vent sites at one of the sites located on a seaward dipping thrust zone the benthic communities are associated with a disruption of the subsurface acoustic layering in the thrust zone it appears that at this site dewatering is occurring along fractures in the disrupted sediments which connect to permeable layers in the undeformed sediments and not along the main thrust fault the other site is located near the top of a ridge which has been uplifted by thrusting along a landward dipping thrust most of the benthic communities are found to exist at the outcrop of a steeply dipping unconformity between recent slope basin sediments and the older uplifted sediments with the unconformity serving as the fluid pathway underlying this unconformity at the most active dewatering location is a complexly deformed structuremore which appears to enhance the flow of fluid to the unconformity the source of the fluids could be the older uplifted sediments or the recent slope basin turbidites in either case the source is shallow less than about 1 km less