threshold height h f c for the meridional wind to play a deterministic role in the bottom side equatorial spread f and its dependence on solar activity 1 detailed investigations have been carried out on the occurrence of bottom side equatorial spread f esf and the thermospheric meridional wind characteristics just before the former s initiation using ground based ionospheric data corresponding to the equinoctial periods of 1993 1998 from trivandrum 8 5 n 76 5 e dip 0 5 n and sriharikota 13 7 n 80 2 e dip 10 n in the indian longitudes critical analysis of the base height of the f region h f at the time of triggering of esf and the polarity of the meridional winds revealed that if the h f is above a certain level esf occurred under both equatorward and poleward wind conditions below that level esf occurred only when equatorward winds were present implying that the equatorward winds must somehow be able to offset the reduced growth rate of the plasma instability responsible for esf a plausible explanation linking equatorial ionization anomaly eia and the consequent equatorial temperature and wind anomaly etwa and the consequent neutral dynamics effectively enabling the instability even at lower height has been offered the threshold height h f c gleaned out on the basis of the polarity of the meridional winds has been shown to bear a linear relation to the solar activity and sheds light on the enigmatic short and long term variability of esf

the origin of natural gas in the hutubi gas field southern junggar foreland sub basin nw china abstract the hutubi gas field is the largest field discovered in the southern junggar foreland sub basin at present the origin and generation of gas in the field have been discussed based on the geochemical data the carbon isotopic composition of methane and ethane in the hutubi gas field is relatively enriched in 13 c with 13c1 values ranging from 32 8 to 30 5 average value 31 2 and 13c2 values ranging between 23 0 and 21 6 average value 22 0 the hydrogen isotope is lighter with d1 from 200 to 196 methylcyclohexane is abundant and the content is the highest among c7 light hydrocarbons ranging from 49 6 to 59 4 with an average value of 55 5 the 13c values of individual c6 c7 light hydrocarbons are heavier with the 13c values from 25 2 to 17 9 the results show that gas in the hutubi field is coal derived gas and sourced from the middle and lower jurassic coal measures the result of gas generation kinetics from jurassic coal measures show that the gas generation began 10 ma and the methane generation transformation ratio is very high up to 87 at present the time of gas generation is consistent with that of the hutubi structural trap and shows that the formation time of the hutubi gas field is very late it is concluded that gas preservation in the southern junggar foreland sub basin is excellent and gas exploration potential is favorable

possible atmospheric origin of the 7 may 2007 western black sea shelf tsunami event 1 the paper examines the possibility that tsunami event recorded in the western black sea on 7 may 2007 was triggered by a traveling atmospheric disturbance as meteotsunamis are favored by specific synoptic conditions we inspected available ground and sounding observations european centre for medium range weather forecasts reanalysis fields and satellite based products and compared them to the documented mediterranean meteotsunamis we found an atmospheric disturbance traveling toward 30 nne with amplitude of 2 3 hpa and propagation speed of about 16 m s passing through few tens of kilometers wide pathway over the region affected by the tsunami this disturbance occurred in the lower troposphere but it was capped by instable convective cell that preserved gravity disturbance s coherence over a region at least 150 km long an ocean modeling study showed that such a disturbance is capable of generating large tsunami waves and strong currents over the shallow regions following the observations over the region where maximum sea level oscillations have been documented therefore this event has a potential to be classified as a meteotsunami the first of such kind in the black sea

impacts of the tectonic stress field on natural gas migration and accumulation a case study of the kuqa depression in the tarim basin china stress fluid and temperature are three of the major factors that impact natural gas migration and accumulation in order to study the influences of tectonic stress field on natural gas migration and accumulation in low permeability rocks we take the kuqa depression as an example and analyze the evolution of the structure and tectonic stress field at first then we study the influences of tectonic stress field at different tectonic episodes on fractures and fluid potentials through the numerical simulation method on the section across the kl2 gas field we summarize two aspects of the impact of the tectonic stress field on natural gas migration and accumulation firstly under the effects of the tectonic stress field the rock dilation increases with the added stress and strain and when the shear stress of rock exceeds its shear strength the shear fractures are well developed on one hand the faults which communicate with the hydrocarbon source rocks become the main pathways for natural gas migration on the other hand these positions where fractures are well developed near faults can become good reservoirs for natural gas accumulation secondly because fluid potentials decrease in these places near the faults where fractures are well developed natural gas can migrate rapidly along the faults and accumulates the impact of tectonic stress fields on natural gas migration and accumulation allows for hydrocarbon migration and accumulation in the low permeability rocks in an active tectonic compressive setting

impact of meridional winds on equatorial spread f revisited 1 the impact of meridional winds on the onset and evolution of equatorial spread f esf is studied using the nrl ionosphere model sami3 esf the prevailing belief is that meridional winds have a stabilizing effect on the onset of esf in this letter it is shown that this is not necessarily the case and that meridional winds can be destabilizing we find that a wind profile with a positive gradient as a function of latitude v m 0 is a stabilizing influence on the generalized rayleigh taylor instability a wind profile with a negative gradient v m 0 is a destabilizing influence here a northward wind is positive and increases in the northward direction it is suggested that meridional wind profiles may account for in part the longitudinal and day to day variability of esf

guidelines for evaluating petroleum source rock using programmed pyrolysis rock eval pyrolysis is used to rapidly evaluate the petroleum generative potential and thermal maturity of rocks accurate conclusions require programs every 30 60 ft 9 18 m understanding of interpretive pitfalls and supporting data such as visual kerogen vitrinite reflectance and elemental analyses the generative potential of coals is commonly overestimated by pyrolysis and is best determined by elemental analysis and organic petrography most coals show high s2 s3 5 and low hi values 300 mg hc g toc migrated oil and mud additives which alter rock eval data can sometimes be removed by special processing for immature rocks bimodal s2 peaks and pi values over 0 2 indicate contamination pyrolysis downgrades organic poor clay rich rocks which show lower hi and higher tmax values than isolated kerogen because of adsorption of pyrolyzate on the clays tmax values for small s2 peaks 0 2 mg hc g toc are unreliable tmax is affected by maturation organic matter type contamination and the mineral matrix s3 is sensitive to inorganic and adsorbed carbon dioxide and to instrumentation problems acidification of carbonate rich samples and proper maintenance improves s3 measurement constant sample weights 100 mg are recommended below a threshold weight tmax increases by up to 10 c and other parameters decrease organic rich samples which overload the detector can be diluted with carbonate detector linearity is determined by pyrolyzing various weights of an organic rich rock

thermal history of sedimentary basins maturation indices and kinetics of oil and gas generation temperature is the most sensitive parameter in hydrocarbon generation thus reconstruction of temperature history is essential when evaluating petroleum prospects no measurable parameter can be directly converted to paleotemperature maturation indices such as vitrinite reflectance tmax from rock eval pyrolysis spore coloration thermal alteration index tai or concentration of biological markers offer an indirect approach all these indices are a function of the thermal history through rather complex kinetics frequently influenced by the type of organic matter their significance and validity are reviewed besides the problems of identification e g vitrinite and interlaboratory calibration it is important to simultaneously interpret kerogen type and maturation and to avoid difficult conversions from one index to another geodynamic models where structural and thermal histories are connected are another approach to temper ture reconstruction which could be calibrated against the present distribution of temperature and the present value of maturation indices kinetics of kerogen decomposition controls the amount and composition of hydrocarbons generated an empirical time temperature index tti originally introduced by lopatin does not allow such a quantitative evaluation due to several limitations no provision for different types of kerogen and different rates of reactions poor calibration on vitrinite reflectance it is of limited interest unless one has no access to a desk top computer kinetic models based on a specific calibration made on actual source rock samples can simulate the evolution of all types of organic matter and can provide a quantitative evaluation of oil and gas generated examples from the jurassic source rocks of the paris basin monterey formation of california green river shales of utah paleozoic source eds of the algerian sahara and miocene rocks of the mahakam delta indonesia illustrate various aspects of the discussion geological geochemical models are the most efficient way to integrate geological seismic and geochemical data and they should greatly help to reduce the risk in exploration

genetic classification of petroleum basins rather than relying on a descriptive geologic approach this genetic classification is based on the universal laws that control processes of petroleum formation migration and entrapment petroleum basins or systems are defined as dynamic petroleum generating and concentrating physico chemical systems functioning on a geologic space and time scale a petroleum system results from the combination of a generative subsystem or hydrocarbon kitchen essentially controlled by chemical processes and a migration entrapment subsystem controlled by physical processes the generative subsystem provides a certain supply of petroleum to the basin during a given geologic time span the migration entrapment subsystem receives petroleum and distributes it in a manner that can lead either to dispersion and loss or to concentration of the regional charge into economic accumulations the authors classification scheme for petroleum basins rests on a simple working nomenclature consisting of the following qualifiers 1 charge factor undercharged normally charged or supercharged 2 migration drainage factor vertically drained or laterally drained and 3 entrapment factor low impedance or high impedance examples chosen from an extensive roster of documented petroleum basins are reviewed to explain the proposed classification

thermal histories and hydrocarbon generation example from utah wyoming thrust belt the thermal history of the utah wyoming thrust belt in the vicinity of the pineview oil and gas field is studied with a detailed thermal model the model incorporates a heterogeneous thermal conductivity structure radioactive heat generation in the crust sediment compaction variable basal heat flow through time and thermal effects of sedimentation erosion and thrust faulting the analysis is constrained by 206 corrected bottom hole temperatures 660 thermal conductivity measurements and 10 new vitrinite reflectance measurements present surface heat flow in this part of the utah wyoming thrust belt is estimated to be 60 8 mw m2 surface heat flow in the late cretaceous about 70 ma is inferred to have been 38 8 mw m2 from an lysis of vitrinite reflectance data about half of the apparent difference between ancient and present surface heat flow may be attributed to transient thermal effects of sedimentation erosion and thrusting the hypothesis of a constant background thermal state in this part of the thrust belt for the last 70 m y may not be ruled out however thermal history simulations in which the background thermal state changes through time better match constraints imposed by estimated present surface heat flow and vitrinite reflectance data application of the thermal history analysis to hydrocarbon generation is illustrated with a kinetic model of organic maturation oil and gas at the pineview field may have been generated in two stages first stage just before and during thrusting and the second stage during cenozoic warming

neutral temperature anomaly in the equatorial thermosphere a source of vertical winds data obtained from the wats wind and temperature spectrometer instrument on de 2 dynamics explorer during high solar activity show new evidence for the presence of vertical winds of a significant magnitude in the equatorial thermosphere they reveal a latitudinal structure that can be related to the recently discovered phenomena of the equatorial temperature and wind anomaly etwa in the local evening hours the vertical winds usually are downward around the dip equator and collocated with the temperature minimum of etwa in general they are upward at about 24 dip latitude away from the dip equator and are collocated with the etwa temperature crests the magnitude of the vertical winds is in the 10 40 m s range it is proposed that the temperature and pressure ridges formed by the excess ion drag on the zonal winds around the two crests and ordered by the relatively lower ion drag at the trough of the well known equatorial ionization anomaly eia drive a new wind system in the meridional plane and that the measured vertical winds form part of this wind system

geochemical characteristics and origins of noble gases of the kela 2 gas field in the tarim basin china abstract research on noble gases is important which can provide more information on gas origins and sources due to their special chemical inertness and genesis related to nuclear processes however few studies have been carried out on noble gases in the largest un compartmentalized gas field in the tarim basin in this study molecular and isotopic compositions of noble gases and hydrocarbon gases in the kela 2 gas field were analyzed hydrocarbon gases are the dominant gases accompanied by minor n 2 co 2 and extremely low contents of noble gases in the kela 2 gas field he content is generally 1 order of magnitude higher comparing to that of air while ne ar kr and xe contents are 1 3 orders of magnitude lower than corresponding atmospheric values the 13 c 2 value indicates natural gases in the kela 2 gas field are typical coal derived gases noble gases in the kela 2 gas field are typical crustal derived source mainly originating from decay of crustal radioactive elements natural gases in the kela 2 gas field are speculated to be derived from the coal measures source rocks of triassic to jurassic with major contribution from coals and secondary contribution from mudstones

the prereversal enhancement of the zonal electric field in the equatorial ionosphere the electric fields in the ionospheric e and f regions near the magnetic equator often show a strong eastward enhancement shortly after sunset and before the eastward normally daytime field reverses to westward several theoretical models of the low latitude fields suggest that this enhancement is caused mainly or entirely by f region winds the f region dynamo but some authors have suggested that it could be produced solely by e region tidal winds we give here additional calculations and arguments in support of the f region source the enhancement of the eastward field for an eastward f region wind turns out to be a simple direct consequence of the fact that after sunset the ionospheric conductivity decreases far more rapidly in the e region than in the f region

substratum transverse faults in kuqa foreland basin northwest china and their significance in petroleum geology abstract the importance of transverse faults in basin evolution and petroleum geology has been often emphasized however the transverse faults in the kuqa foreland basin the most important gas producing area in china have rarely been studied interpreted seismic sections and earthquake focal mechanism solutions as well as other geological and geophysical data allow us to identify a few widely spaced approximately ns trending transverse strike slip faults separating major structural units and to clarify the geometry and kinematics of these transverse faults hidden below thrust faults in the kuqa foreland basin two major structural domains can be distinguished transverse faults in the northern kuqa foreland basin are mainly nne trending sinistral indicating clockwise rotation of fault bounded blocks in contrast the predominant nw trending dextral faults in the southern kuqa foreland basin imply counterclockwise rotation of fault bounded blocks we propose a tectonic model in which crustal blocks are bounded by strike slip faults in a zone of simple shear rotation about vertical axis the strike slip faulting and thrust faulting in the kuqa foreland basin suggest that some of the convergence between south tianshan and tarim blocks may have been accommodated not only by obvious crustal shortening and thickening along thrust faults but also by rotation and possible lateral movement of the crust along transverse faults controlled by the remote collision of indian block with eurasian block since the miocene these reactivated substratum faults which may inherit from paleozoic deformation control various elements relevant to gas accumulation in the kuqa foreland basin which should expect to be paid more attention in the future these elements include maturity of tertiary and jurassic source rocks a difference in the regional cap of kumugelimu salt beds from east to west reservoir bed properties gas migration channels and traps formation in addition the strike slip faulting of the transverse faults may affect deformation of the sedimentary cover including making the western qiulitag structural belt to form an arcuated structure curved to the ssw

deep burial diagenesis and reservoir quality evolution of high temperature high pressure sandstones examples from lower cretaceous bashijiqike formation in keshen area kuqa depression tarim basin of china the deep high temperature high pressure lower cretaceous bashijiqike sandstone buried to depths as great as 6 5 7 1km is an important natural gas reservoir in keshen gas field kuqa depression of the tarim basin reservoir quality is a critical risk factor in the development of these ultradeep reservoirs integrated approaches incorporating routine core analyses mineralogical petrographic and geochemical analyses have been used to investigate the diagenetic history of these rocks and their impact on reservoir quality with the aim to unravel the mechanisms for maintaining anomalously high porosities in sandstones that are buried to such a great depth these sandstones are dominantly fine to medium grained moderately to good sorted lithic arkoses and feldspathic litharenite most primary pores have been lost by mechanical compaction or carbonate cementation and the reduction of porosity by mechanical compaction was more significant than by cementation dissolution of framework grains contributed to the enhancement of reservoir quality eogenetic diagenetic alterations mainly include mechanical compaction precipitation of calcite cements and grain coating clays mesogenetic diagenesis is characterized by dissolution of framework grain by organic acids and subsequent precipitation of clay minerals and quartz infiltration of meteoric water related to teleodiagenesis would result in dissolution of the framework grains the meteoric leaching events during teleodiagenesis are of great importance for the bashijiqike sandstones grain coating clay minerals mixed layer illite smectite clays help to preserve porosity at depth by retarding quartz cementation and pressure solution the unique burial regime as early stage shallow burial with late stage rapid deep burial contributes to porosity preservation in eodiagenesis fluid overpressure caused by intense structural compression in the middle himalayan movement retarded compaction and helped preserve porosity in the late rapid deep burial stage anomalously high porosities are mainly found in medium grained good sorted sandstones with grain coating clays but with low clay and carbonate cement content of which the porosity is preserved primarily and enhanced secondarily the lowest porosities are associated with sandstones that are tightly compacted or cemented with carbonates or rich in detrital matrix porosity depth trends may vary significantly with lithofacies due to its differences in textural and compositional attributes five lithofacies are defined in terms of detrital composition and texture type and degree of diagenesis the reservoir quality prediction models of various lithofacies are constructed and the results of this study provide insights into mechanisms for maintaining anomalously high porosity and permeability in high temperature high pressure sandstone reservoirs and may help explain hydrocarbon distribution

stable carbon isotopes of coal derived gases sourced from the mesozoic coal measures in china coal derived large scale gas fields derived from the mesozoic coal measures in china are mainly distributed in the middle lower jurassic coal measures in the tarim junggar and turpan hami basins in northwest china and the upper triassic xujiahe formation coal measure in sichuan basin central china in 2011 the annual production was 21 6 109 m3 and the proved geological reserves were 2485 109 m3 accounting for 21 and 30 of the total in china respectively based on analyses of gas composition and stable carbon isotopes ratios of 203 samples and stable carbon isotopes of 102 co2 samples the following conclusions were made a based on diagnostic plots using the stable carbon isotopic and molecular composition of gas samples alkane gas from the mesozoic coal measures in china is shown to be coal derived b according to the 13c2 vs c2h6 plot of a great number of oil derived and coal derived gases in china it is concluded that gases with 13c2 28 5 are coal derived and those with 13c2 28 5 are oil derived in most cases c among the natural gases from the mesozoic coal measures in china primary coal derived gases with normal carbon isotopic distribution pattern among the c1 c4 alkanes i e 13c1 13c2 13c3 13c4 are dominant d carbon isotopic pattern reversal mainly results from the mixing of coal derived gases having different maturities but the same source and secondly from microbial oxidation of propane e g mu 3 and mu 4 wells in the gumudi gas field junggar basin e co2 in the coal derived gases from the mesozoic coal measures in china has both biogenic and abiogenic origins the biogenic origin is dominant and the abiogenic co2 is mainly found in the kuqa depression in the tarim basin and western sichuan basin f isotopic differences between heavy hydrocarbon gases and methane become less with increasing maturity

observations of mesocale wave disturbances during the genesis of atlantic lows experiment abstract the portable automated mesonet pam data obtained during the genesis of atlantic lows fxperiment gale are used to document mesoscale wave activity during the 3 day period from 4 to 6 february 1986 from the surface pressure analyses four cases of wave activity are identified with wavelengths of 200 400 km phase speeds of 20 40 m s 1 and trough to crest pressure amplitudes of 0 5 3 5 mb precipitation was associated with the waves in two of the four cases detailed analyses of the horizontal structure show that the waves do not have the pressure wind relationship expected from linear gravity wave theory the wind vectors are oriented from high to low pressure with a maximum amplitude between the high and low pressure areas low level inversions were present in three of the four cases in the raw without a low level inversion the amplitude rapidly decreased as the wave moved towards the east in the case which lasted for the longest time period at least 8 h and had the largest pressure amp

a multiple sounding technique for the study of gravity waves radiosondes released in rapid succession with a time separation of a few minutes were launched during a field experiment in central wales u k to study orographic gravity waves rate of ascent fluctuations were used to infer the existence of vertical velocity fluctuations associated with orographic gravity waves and differences between consecutive ascents provided information on the steadiness and phase line slope of the waves the potential of the multiple sounding technique is examined here and an analysis strategy proposed three triple sounding cases from the field experiment are used to illustrate the strengths and weaknesses of the technique in one case it was possible to estimate a phase line tilt with height and this combined with the inferred vertical velocity amplitude allowed the estimation of the vertical momentum flux it is suggested that the near simultaneous release of between three and five sondes upstream of mountainous terrain could provide a useful method for calculating the vertical flux of momentum due to gravity waves

relationship between petroleum composition and depositional environment of petroleum source rocks crude oils of nonmarine source can be distinguished from those of marine shale source and from oils originating in marine carbonate sequences by using a battery of geochemical parameters as demonstrated with a sample suite of nearly 40 oils a novel parameter based on the presence of c30 steranes in the oil was found to be a definitive indication of a contribution to the source from marine derived organic matter a second novel parameter based on monoaromatized steroid distributions was effective in helping to distinguish nonmarine from marine crudes and can be used to gauge relative amounts of higher plant input to oils within a given basin sterane distributions were similarly useful for detecting higher plant input but were less effective than monoaromatize steroid distributions for making marine versus nonmarine distinctions concentrations of high molecular weight paraffin can also be effective nonmarine indicators but are influenced by maturation and biodegradation processes certain algal derived nonmarine oils may show little high molecular weight paraffin response oils from carbonate sources with a few exceptions can be distinguished by having low pristane phytane ratios low carbon preference indexes and high sulfur contents gammacerane indexes and carbon isotope ratios of the whole crude are not effective in distinguishing these types of environmental differences on a global basis

thermal and burial history of the cracow silesia region southern poland assessed by conodont cai analysis abstract conodont colour alteration cai data have been applied in the reconstruction of palaeothermal conditions in the cracow silesia region southern poland the analysis of conodont cai values supplemented by electron spin resonance esr data provided a complex maturity pattern which coincides well with the tectonostratigraphical divisions of this region during the variscan and alpine diastrophic cycles the palaeozoic rocks in the upper silesian coal basin attained the observed thermal maturity during late carboniferous or permian time just after the tectonic inversion of the basin vertical maturity trends suggest that palaeo geothermal gradients were significantly higher than the present values the irregular maturity pattern recognized in the cracow myszkow zone is related to the thermal overprint of intrusive igneous rocks on the maturity field resulting from the relatively shallow burial this pattern has not been modified by mesozoic hydrothermal events the low maturity level of devonian and early carboniferous rocks in the substrate of the carpathian foredeep is a product of the subsidence during miocene time the implications for hydrocarbon generation and further exploration are discussed the cai data are consistent with other indicators of organic metamorphism previously used in this region the study highlights also features about the conodont colour alteration such as the influence of silica mobilization on conodont colour which limit the application of the cai method

evolution of porosity and pore geometry in the permian whitehill formation of south africa a fe sem image analysis study abstract since the advent of technologically efficient exploitation of economic hydrocarbon reservoirs in shales increasingly more research has been devoted to identifying and characterizing pore systems within shales however only a handful of these studies focused on the development of porosity in thermally mature unconventional reservoirs in this study the evolution of porosity and pore geometry in the permian whitehill formation is addressed with the aid of ultrathin sections 2 3 cm 10 20 m thick and field emission scanning electron microscopy fe sem on samples with mean random vitrinite reflectance values ranging from 1 03 to 4 07 ro we document a strong positive covariation of porosity and total organic carbon content toc in all localities however for samples with vitrinite reflectance values greater than 2 88 ro porosity per unit toc decreased by over 25 relative to samples with lower thermal maturities the positive covariation of thermal maturity and total porosity recorded here is unsurprising and have been documented previously in many gas shales however the dramatic decrease in porosity restricted to samples from localities that experienced advanced maturation ro 2 88 is viewed as an evidence that porosity decrease is directly related to late thermal decarboxylation of organic matter this is supported by the presence of pores and micro fractures infilled by fibrous grains including carbonates clays silicates and phosphates and residual fluid inclusions these grains were likely generated from re precipitation of framework grains previously dissolved by organic acids carboxylic phenolic that were generated during thermochemical decarboxylation of the om our findings do not only fill important gaps in the understanding of organic pore development including processes that create preserve and destroy porosity the porosities described here are also key to gas transfer from shale matrix to induced fractures during fracture stimulation programs

tectono thermal evolution of cambrian ordovician source rocks and implications for hydrocarbon generation in the eastern tarim basin nw china abstract the tectono thermal evolution is an important control on petroliferous basin development however this evolution is difficult to reconstruct in sedimentary basins subjected to multiple tectono thermal events the tarim basin is the largest petroliferous basin in northwestern china and hosts a complex oil gas system comprising several sets of source reservoir and cap rocks that have experienced multiple tectonic thermal and sedimentary events large oil and gas reserves have been discovered in the central and northern tarim basin during the last 30 years but none in the eastern part of the basin this is generally attributed to the high thermal maturity reached by source rocks during the late ordovician and subsequent hydrocarbon loss therefore reconstructing the cambrian ordovician tectono thermal evolution is critical in facilitating successful oil and gas exploration in this region we compiled equivalent vitrinite reflectance data n 178 of source rocks from seven wells in the tarim basin which for cambrian ordovician source rocks are 1 3 beyond the hydrocarbon generation threshold and in the main gas and dry gas generation stages the cambrian ordovician source rocks experienced rapid burial and heating during the caledonian period entered the hydrocarbon generation stage during the middle late ordovician and reached peak hydrocarbon generation at the end caledonian period they might have experienced secondary hydrocarbon generation after the jurassic homogenization temperatures of fluid inclusions n 616 from wells gc4 lx1 md1 and yd2 as well as the modeled thermal evolution reveal a main hydrocarbon generation event during the caledonian period and a secondary event in the yanshanian and himalayan period in other wells lx1 md1 and yd2 hercynian and indosinian uplift and exhumation in the eastern tarim basin controlled the main structures and faulting created favorable conditions for secondary hydrocarbon generation and migration at this time since the yanshanian and himalayan the tarim basin has experienced further sedimentation and heating and the tectono thermal evolution might have been related to the formation of the tibetan plateau in summary our reconstruction of the tectono thermal evolution of cambrian ordovician strata and the hydrocarbon generation history of the tarim basin suggests that the eastern tarim basin may also have hydrocarbon generation potential and can guide future oil and gas exploration

atmospheric gravity waves and the rissaga phenomenon the atmospheric forcing of large sea level oscillations up to 1 5 m amplitude with about a 10 min period in some bays and inlets of the balearic islands is described using simultaneous measurements of pressure and sea level elevation in the port of ciutadella at the end of a large and narrow inlet during 5 7 july 1989 the influence of atmospheric pressure oscillations on these large sea level variations locally known as rissaga is investigated coherence and cross correlation functions reveal that the large oscillations in the inlet are associated with and probably forced by a 10 min gravity wave in the atmosphere the effect of longer period waves on the inlet is seen in the well known inverted barometric effect forcing small oscillations in the water level of just some centimetres these latter waves have a period of around 50 min and an unusually large amplitude of some 3 mb the phase spectrum between sea level and pressure suggests that the inlet may behave as a damped harmonic oscillator which during rissaga is externally forced by the atmospheric pressure oscillations

origin evolution and finescale structure of the st valentine s day mesoscale gravity wave observed during storm fest part ii finescale structure abstract this paper presents observations of the finescale three dimensional kinematic and thermodynamic structure of a long lived mesoscale gravity wave that occurred on 14 15 february 1992 during the storm scale operational and research meteorology fronts experiment systems test storm fest in part i of this series of papers it was shown that the wave was generated just behind the leading edge of an advancing dry air mass that originated as a foehnlike downslope flow over the rocky mountains of southern colorado and new mexico surface pressure signatures of wave motion began as the dry air mass ascended a warm front east of a lee cyclone and a rainband developed along its leading edge the wave and rainband intensified remaining near the leading edge of the dry air mass as the dry air mass advanced northeastward over the warm frontal inversion after 7 h of evolution the leading edge of the dry air mass passed over the dual doppler network in northeast kansas it was at this point in the evolution

investigation of pore structure and petrophysical property in tight sandstones abstract laboratory measurements include porosity permeability high pressure mercury intrusion hpmi nuclear magnetic resonance nmr measurements and microscopic analysis of thin sections and scanning electron microscope sem were used to gain insight into the nature of the pore throat structure including pore geometry pore size distribution and pore connectivity of bashijiqike tight gas sandstones in keshen 5 keshen 6 keshen 8 keshen 9 and keshen 13 wellblock of kuqa depression the relationships between microscopic pore structure parameters and macroscopic petrophysical behaviors were investigated by regression analysis the results show that various types of pores with wide ranges of pore radius are observed the pore throats are very small commonly rapex controls permeability in tight gas sandstones the nmr pore size distribution is broader than the hpmi pore throat distribution in the nmr analysis only the pore systems connected by the relatively large pore throats should be accounted as movable and some portion of large pores which are not connected by effective large pore throats are not effectively movable the effective movable porosity is calculated by excluding those pores restricted by the tiny pore throats the content of effective movable porosity from nmr measurements shows good correlation relationship with the porosity connected by large pore throats in hpmi analysis three typical types of pore structures are recognized through thin section sem analysis combined with the capillary curve and nmr t2 spectrum and the microscopic and macroscopic characteristics of the three pore structures are investigated the pore structure were comprehensively evaluated and characterized by linking nmr t2 spectrum with hpmi analysis

regional source rock mapping using a source potential rating index a method has been developed to combine sediment thickness organic carbon content and thermal maturity data from potential source rock units into a single mappable parameter that can be used to indicate areas of potential hydrocarbon generation this parameter is computed by multiplying the average percent organic carbon by the effective source rock thickness of a formation this yields a richness factor that is then multiplied by maturity scaling factors to give source potential ratings for oil and or gas generation the rating values can be combined with kerogen type data if available to refine these assessments of generating potential the rating index can also be used with burial history curves and thermal maturation modeling to look at source potential during geol gic time an example is given of the rating index mapping applied to the bakken formation in the williston basin the source potential rating index provides objective semiquantitative measures by which the source potential of a single formation can be compared within an area or by which the source potential of two or more formations can be compared in the same or different basins in conjunction with structural analysis of a basin the resulting maps can help the explorer explain known hydrocarbon accumulations trace migration pathways and point toward new areas for exploration

analytical simulation of edge waves observed around the balearic islands the research is also partly supported by national science foundation grants to cornell university cytmar mar95 1863 project provided the necessary funding for the acquisition of the data

the depletion of oil abstract the trend of previous estimates of the world s ultimate recovery of oil suggests a figure of 1650 bbo of which 1438 bbo have been discovered and 978 bbo remain to be produced some large reported reserve figures are questioned importance is attached to the mid point of depletion when rising production tends to give way to decline the share of the world s supply coming from six middle east countries is set to continue to rise from its 1986 low of 16 to as much as 50 by 2010 with the likely consequence of higher oil prices and serious political implications the world is rapidly approaching a turning point when it has to face the consequences of an irreversible decline in oil production

gravity wave observations using an array of microbarographs in the alearic islands time series of surface pressure from an array of microbarographs in the balearic islands western mediterranean are used to obtain wavelength phase speed and direction of propagation of gravity waves on the balearic islands these pressure waves are commonly found during the summer and they force the large seal level oscillations observed in the inlet of ciutadella a phenomenon locally known as rissaga four events are described here each of which has a duration of between 30 and 48 hours radiosonde data from palma de mallorca are used to relate the waves to the vertical structure of the atmosphere the various source mechanisms of these waves and also the possibility of the existence of a duct layer trapping the wave energy near the surface are discussed the waves are found to have no significant variation of phase speed with frequency and so they are basically non dispersive this is an indicator pointing either to a local generation of gravity waves by wind shear instability or to the existence of neutral trapped waves in the lower troposphere

magnetic declination control of the equatorial f region dynamo electric field development and spread f we have carried out a comparative study of the evening prereversal enhancements in the equatorial f region vertical ionization drift velocities vz over fortaleza 4 s 38 w brazil and jicamarca 12 s 77 w peru two magnetic equatorial stations in the american zone the results show profound dissimilarities in the seasonal trends in the times and widths of the vz prereversal peak which reflect in the spread f characteristics as well at the two stations the dissimilarities are shown to be arising mainly from the difference in the magnetic field declination angles that causes differences in the conjugate e region sunset durations and hence in the f region polarization electric field development rates at the two stations

a case study of gravity waves convective storms interaction 9 may 1979 abstract an analysis is presented of a series of severe storms which occurred in the north central united states on 9 may 1979 and whose spatial distribution and movement correlate well with observed gravity waves two gravity wave trains of 2 1 3 mb amplitude 2 5 3 3 h period and 240 265 km horizontal wavelength were isolated through power spectra analysis and cross correlation techniques applied to national weather service barograph traces the wave trains propagated in the 200 direction which coincided with the jet axis with a phase velocity of 20 30 m s 1c and within a 300 km wide band the storms were identified on enhanced infrared goes satellite pictures with the help of radar summaries these convective systems initially developed in nebraska and propagated north northeast at 25 m s 1 revealing wave like characteristics with a separation of 300 400 km the convective systems were closely linked to the observed wave trains with cell intensity height and associated rainfall maximized at the wa

generation of nitrogen and methane from sedimentary organic matter implications on the dynamics of natural gas accumulations nitrogen n2 contents of natural gases in rotliegend and buntsandstein reservoirs of the north german basin regionally approach 100 a review is given of the various hypotheses primordial origin volcanic or magmatic origin radiogenic origin atmospheric origin organic origin inorganic nitrogen in sedimentary rocks presented to account for nitrogen anomalies in this area and other parts of the world the objective of the present study was to investigate sedimentary organic matter in particular coals as a potential source of molecular nitrogen in the subsurface comparison of reservoir sizes and gas generation potentials indicates that carboniferous coal measures which are considered as the source of the natural gas in the north german basin can readily account for the nitrogen quantities found in present day reservoirs laboratory pyrolysis experiments were carried out to investigate the kinetics of generation of methane and molecular nitrogen from coals of different type and rank under experimental conditions nitrogen is formed at higher temperatures than methane supporting the concept of a fractional generation of methane and nitrogen in natural systems based on the kinetic parameters derived from laboratory experiments methane and nitrogen generation rates from coals were calculated for geologic heating rates gas containing more than 50 nitrogen is generated under these conditions at temperatures in excess of 300 c nitrogen rich gases are thus formed only in the final stage of gas generation after methane generation has practically ceased it is concluded that the amounts of gas encountered in nitrogen rich gas accumulations represent only a small fraction possibly 1 of the total gas generation potential of this area while the bulk of the generated gas has escaped to the atmosphere the present day composition of the reservoir gases reflects the composition of only the most recently generated gas on a geologic time scale

molecular nitrogen in natural gas accumulations generation from sedimentary organic matter at high temperatures the occurrence of natural gas accumulations with high percentages up to 100 of molecular nitrogen in various hydrocarbon provinces represents a largely unresolved problem and a serious exploration risk in this context a geochemical and basin modeling study was performed to evaluate the potential of sedimentary organic matter to generate molecular nitrogen the masses of nitrogen present in coals if converted into molecular nitrogen are sufficient to fill commercial gas reservoirs a calculation for gas accumulations in northern germany where percentages of molecular nitrogen range from less than 5 to greater than 90 reveals that the molecular nitrogen generated in underlying coal bearing strata is sufficient to account for the nitrogen gas even in the largest fi lds in addition much of the total nitrogen in clay rich rock types such as shales and mudstones is fixed in sedimentary organic matter and may add to the nitrogen generation capacity of the coals a kinetic interpretation of the nitrogen and methane generation characteristics of humic coals during laboratory pyrolysis indicates that nitrogen is generated from organic matter in sedimentary basins at higher temperatures than methane minimum temperatures for preferential nitrogen generation are in excess of 300 c for extremely low heating rates or isothermal conditions lasting over 300 m y thus nitrogen rich gases are mainly formed in the final stage of gas generation when sedimentary rocks grade into metamorphic rocks applications of the kinetic parameters for the generation of nitrogen and methane from coaly organic matter in carboniferous sedimentary rocks are presented for part of the northwest german basin in this area immense volumes of the methane rich gas gener ted during the late paleozoic and mesozoic were lost to the atmosphere the present gas composition mainly reflects the latest cenozoic gas generation this cenozoic gas is nitrogen rich where the carboniferous source rock sequences are highly mature and deeply buried

study of equinoctial asymmetry in the equatorial spread f esf irregularities over indian region using multi instrument observations in the descending phase of solar cycle 23 1 in this paper we present the results of a morphological study of equatorial spread f esf irregularities over indian region based mainly on observations of 1 amplitude scintillations on gps l band signal and rate of tec index roti obtained using a network of gps receivers and 2 amplitude scintillations on a vhf signal using spaced receivers at tirunelveli an equatorial station occurrence of both amplitude scintillations on the gps l1 signal and occurrence of significant roti recorded at several stations has been investigated the latitudinal extent of l band scintillations shows that their strength is weak over the dip equator but stronger over equatorial ionization anomaly eia region preferentially during vernal equinox we find an equinoctial asymmetry in both the occurrence of scintillations and roti wherein their occurrence is greater in the vernal equinox than in the autumn equinox attempts have been made to understand the asymmetry in latitudinal extent using maximum cross correlation ci of intensity fluctuations obtained from the vhf spaced receivers observations the observations suggest that occurrence of ci less than 0 5 is more in the vernal equinox than in the autumn equinox suggesting that the maximum height of the equatorial plasma bubbles epbs during vernal equinox may be higher than that during autumn equinox timed guvi retrieved peak electron density during the same period also indicates that background electron density is higher and more symmetric during vernal equinox than autumn equinox hence our results suggest that background electron density may be playing a vital role in creating the equinoctial asymmetry

remote trigger of deep convection by cold outflow over the taiwan strait in the mei yu season a modeling study of the 8 june 2007 case abstractin this study the heavy rainfall event over central taiwan during the mei yu season on 8 june 2007 is investigated with an emphasis on the triggering mechanism for the deep convection that produced the rain observations indicate that there existed two lines of forcing with convection prior to the rain one over the northern taiwan strait along the mei yu front and the other over the southern taiwan strait yet the convection in question developed over the central strait between these two lines in an unstable environment with strong westerly vertical wind shear this motivated the authors to carry out the present study the cloud resolving storm simulation cress of nagoya university was used and the event was reproduced at a horizontal grid size of 2 km including the initiation of new convection over the central strait at the correct location and time the model results suggest a crucial role played by the series of active persistent and propagating storms in the southern strait along the

onset conditions for equatorial spread f the problem of day to day variability in the occurrence of equatorial spread f esf is addressed using multidiagnostic observations and semiempirical modeling the observational results are derived from a two night case study of esf onset conditions observed at kwajalein atoll marshall islands using the altair incoherent scatter radar and all sky optical imaging techniques the major difference between nights when esf instabilities did not occur august 14 1988 and did occur august 15 1988 in the kwajalein sector was that the northern meridional gradient of 6300 a airglow was reduced on the night of limited esf activity modeling results suggest that this unusual airglow pattern is due to equatorward neutral winds previous researchers have shown that transequatorial thermospheric winds can exert a control over esf seasonal and longitudinal occurrence patterns by inhibiting rayleigh taylor instability growth rates we present evidence to suggest that this picture can be extended to far shorter time scales namely that surges in transequatorial winds acting over characteristic times of a few hours to a day can result in a stabilizing influence upon irregularity growth rates the seemingly capricious nature of esf onset may thus be controlled in part by the inherent variability of low latitude thermospheric winds

insights into the damage zones in fault bend folds from geomechanical models and field data abstract understanding the rock mass deformation and stress states the fracture development and distribution are critical to a range of endeavors including oil and gas exploration and development and geothermal reservoir characterization and management geomechanical modeling can be used to simulate the forming processes of faults and folds and predict the onset of failure and the type and abundance of deformation features along with the orientations and magnitudes of stresses this approach enables the development of forward models that incorporate realistic mechanical stratigraphy e g the bed thickness bedding planes and competence contrasts include faults and bedding slip surfaces as frictional sliding interfaces reproduce the geometry of the fold structures and allow tracking strain and stress through the whole deformation process in this present study we combine field observations and finite element models to calibrate the development and distribution of fractures in the fault bend folds and discuss the mechanical controls e g the slip displacement ramp cutoff angle frictional coefficient of interlayers and faults that are able to influence the development and distribution of fractures during fault bend folding a linear relationship between the slip displacement and the fracture damage zone the ramp cutoff angle and the fracture damage zone and the frictional coefficient of interlayers and faults and the fracture damage zone was established respectively based on the geomechanical modeling results these mechanical controls mentioned above altogether contribute to influence and control the development and distribution of fractures in the fault bend folds

origin evolution and finescale structure of the st valentine s day mesoscale gravity wave observed during storm fest part i origin and evolution abstract on 14 15 february 1992 a long lived mesoscale gravity wave was observed over the storm scale operational and research meteorology fronts experiment systems test observational network a precipitation band formed and intensified as the wave moved across kansas and missouri the disturbance was tracked for 14 h surface dual doppler radar and wind profiler analyses as well as isentropic analyses derived from a special rawinsonde network are used to examine the origin and evolution of this wave the wave originated at the leading edge of a dry air mass associated with downslope flow in the lee of the rockies the earliest surface pressure signatures of wave motion began as a dry air mass associated with the downslope flow ascended a warm front east of a lee cyclone a weak rainband developed simultaneously with the wave at the leading edge of the dry air mass the mesoscale gravity wave and convection remained tied to the leading edge of the advancing dry air mass during the first 8 10 h of

geochemical and petrographic characterization of campanian lower maastrichtian calcareous petroleum source rocks of hasbayya south lebanon abstract santonian paleocene marls and fine grained carbonates have been sampled in hasbayya locality south lebanon in order to evaluate their organic matter om content petroleum source rock potential and assess their depositional environment methods included total organic carbon toc total inorganic carbon tic total sulphur ts rock eval pyrolysis organic and inorganic petrography x ray fluorescence xrf gas chromatography mass spectrometry gc ms and curie point pyrolysis gas chromatography mass spectrometry cp py gc ms toc rock eval and vitrinite reflectance vrr results reveal excellent immature petroleum source rocks within the campanian lower maastrichtian interval with toc up to 11 6 wt hydrogen index hi up to 872 mg gtoc tmax up to 433 c and vrr average of 0 36 biomarker ratios and maceral analysis suggest a marine depositional environment with a dominance of algal as well as submicroscopic om original sediment composition and redox sensitive geochemical parameters suggest deposition of the om rich intervals under an oxygen minimum zone omz that was emplaced and controlled by primary productivity and nutrient supply pyrolysate composition shows an important content of organic sulphur compounds thiophenes increasing with toc and thus indicating the presence of type ii and type iis kerogen in the analysed sample set which is consistent with the presence of immature solid bitumen in the hasbayya region the data produced in this study coupled with regional correlations allow us to construct a conceptual depositional model for the upper cretaceous om rich rocks of the eastern mediterranean suggesting deposition under a productivity belt localized along the inner and outer shelf leading to a decrease in source rock quality and a shift in kerogen type toward the deeper parts of the levant basin

large amplitude pressure oscillations in the western mediterranean pressure oscillations with unusually large amplitude of some 3 mb and periods of about 50 min have been registered in the balearic islands western mediterranean sea during summer 1989 these large pressure oscillations are maintained over several hours and have been recorded on several occasions the synoptic pattern and vertical structure of the atmosphere simultaneous with these oscillations is described the large amplitude waves described here do not appear to be directly related to convective activity some of the characteristics of these waves are described however their source mechanism remains unclear

source of the 2007 ist meteotsunami adriatic sea 1 siroka bay on the island of ist in the northern adriatic was struck by a severe inundation around 1530 utc on 22 august 2007 the maximum wave height reached 4 m and substantial material damage was induced this paper investigates the generating force of the inundation data analysis indicates that the inundation was provoked through a double resonance mechanism with initiation by a pronounced atmospheric disturbance that generated open ocean waves through the proudman resonance the waves were then further amplified inside the affected bay the air pressure disturbance which propagated at a speed of about 21 24 m s 1 over the northern adriatic shelf was investigated through both data analysis and atmospheric numerical modeling apparently the air pressure disturbance was a surface manifestation of a ducted gravity wave which propagated through the atmosphere from the apennines to the eastern adriatic coast over the northern adriatic according to the model simulation the wave was trapped in a stable layer adjacent to the ground which was capped by a dynamically unstable layer with wind speeds of about 22 m s 1 this made the unstable layer also a critical layer for gravity waves propagating with the same speed and allowed for their ducting in the layer below

migration effects on the composition of hydrocarbon accumulations in the oml 67 70 areas of the niger delta systematic changes in gas oil ratios in the oml 67 70 area joint venture acreage of the niger delta nigeria illustrate the effects of hydrocarbon migration on the compositional changes observed in the accumulations over large depth intervals one interpretation is that the reservoirs are currently both filling and leaking hydrocarbons indicating that trap styles affect the migration pathways in this region of the niger delta the accumulations are more liquid prone with depth based on the bubble point of the fluids in the reservoir applying these results to regional exploration opportunities indicates that fluid contacts in the normally pressured section are controlled by leaking seals class iii traps the potential exists for pressure controlled filled to spill traps class ii traps in the overpressured section where a high quality seal impedes the vertical flux of hydrocarbon fluids although these conclusions apply to a specific portion of the niger delta combining the concept of trap style with compositional changes resulting from migration processes is useful in identifying new play concepts and opportunities in other regions of the world

depositional environment and thermal maturity of the coal bearing longtan shale in southwest guizhou china implications for shale gas resource potential abstract significant knowledge has been assembled on the marine longmaxi shale in the sichuan basin over the past ten years however the distribution of shale gas resources on the periphery of the sichuan basin and in other source rock formations are still not sufficiently understood to improve our understanding on the depositional environment and thermal maturity and their relevance to the source rock quality and shale gas potential of the thick coal bearing longtan shale 36 organic rich shale samples were selected from a single borehole located in the southwestern guizhou province for geochemical and petrographic analysis total organic carbon toc contents are high with 7 7 wt on average reaching partly up to 28 21 wt while carbonate contents are low vitrinite reflectance vrr values and rock eval tmax temperatures range from 1 48 to 1 84 and 482 to 583 c respectively indicating a high thermal maturity which is in accordance with aromatic molecular parameters the remaining present day hydrocarbon generation potential rock eval s2 is rather low due to the high maturity microscopic investigations further show that the organic matter in the rocks is mainly composed of higher land plant particles present as large and poorly rounded vitrinite and inertinite particles indicating a rather short transport distance toc vs total sulfur ts relationships as well as specific hydrocarbon ratios e g pristane phytane and framboidal pyrite size distributions indicate a variable either marine or freshwater environment for the shales in the coal bearing sequence and suggest that original kerogen was either type iii or type ii iii bottom water during deposition was probably oxygen depleted but not anoxic high sedimentation rates can be assumed for the now 700 m thick compacted sequence favorable for the preservation of organic matter overall the present results are in accordance with previous studies of the longtan shale which initially had a high hydrocarbon mainly gas generation potential furthermore the thickness of the formation is much larger in the here studied southwestern part of the guizhou province than in the previously studied northern parts

climatology of postsunset equatorial spread f over jicamarca 1 we use radar observations from 1996 to 2006 to study the climatology of postsunset equatorial 3 m spread f irregularities over jicamarca during all seasons we show that the spread f onset times do not change with solar flux and that their onset heights which occur near the altitude of the evening f region velocity vortex increase linearly from about 260 to 400 km from solar minimum to solar maximum higher onset heights generally lead to stronger radar echoes during the equinox spread f onset occurs near vertical drift evening reversal times while during the december solstice they occur near the drift reversal times close to solar minimum and near the time of the prereversal velocity peak for high solar flux conditions on average radar plume onset occurs earlier with increasing solar flux in all seasons plume onset and peak altitudes increase with solar activity and the peak heights are generally highest during the equinox the f region upward drift velocities that precede spread f onset increase from solar minimum to solar maximum and are approximately proportional to the maximum prereversal drift peak velocities

conjugate point equatorial experiment copex campaign in brazil electrodynamics highlights on spread f development conditions and day to day variability 1 a conjugate point equatorial experiment copex campaign was conducted during the october december 2002 period in brazil with the objective to investigate the equatorial spread f plasma bubble irregularity esf development conditions in terms of the electrodynamical state of the ionosphere along the magnetic flux tubes in which they occur a network of instruments including digisondes optical imagers and gps receivers was deployed at magnetic conjugate and dip equatorial locations in a geometry that permitted field line mapping of the conjugate e layers to dip equatorial f layer bottomside we analyze in this paper the extensive digisonde data from the copex stations complemented by limited all sky imager conjugate point observations the sheffield university plasmasphere ionosphere model supim is used to assess the transequatorial winds tew as inferred from the observed difference of hmf2 at the conjugate sites new results and evidence on the esf development conditions and the related ambient electrodynamic processes from this study can be highlighted as follows 1 large scale bottomside wave structures satellite traces at the equator followed by their simultaneous appearance at conjugate sites are shown to be indicative of the esf instability initiation 2 the evening prereversal electric field enhancement pre vertical drift presents systematic control on the time delay in sf onset at off equatorial sites indicative of the vertical bubble growth under weak transequatorial wind 3 the pre presents a large latitude height gradient in the brazilian sector 4 conjugate point symmetry asymmetry of large scale plasma depletions versus smaller scale structures is revealed and 5 while transequatorial winds seem to suppress esf development in a case study the medium term trend in the esf seems to be controlled more by the variation in the pre than in the tew during the copex period competing influences of the evening vertical plasma drift in favoring the esf development and that of the tew in suppressing its growth are discussed presenting a perspective on the esf day to day and medium term variabilities

fracture systems and petrophysical properties of tight sandstone undergoing regional folding a case study of the cretaceous reservoirs in the kuqa foreland thrust belt tarim basin abstract the kuqa foreland thrust belt of the tarim basin hosts a prolific hydrocarbon system the main reservoirs are characterized by tight sandstone with low porosity and ultra low permeability buried presently at more than 5000 m depth natural fracture systems have a significant impact on reservoir performance and it may form paths for fluid flow in tight sandstone reservoirs and therefore plays an essential role in controlling high production rates with the aim of analyzing the distribution of favorable reservoir we studied subsurface fracture patterns and petrophysical properties of the bashijiqike formation with data collected from dabei structure and keshen structure we document the presence of four fracture systems whose distribution is related to far field stress thrusting and folding in the keshen anticlines higher fracture intensities are observed in the limbs with principal east west hinge parallel fracture system direction the hinge parallel fracture system includes a moderate dipping fracture set and a vertical fracture set crosscutting relationships stress field inversion and fracture surface textures suggest that the moderate dipping fracture set consists of shear fractures and can be explained by intra layer shear caused by thrusting the vertical fracture set may be formed due to the local outer arc extension during folding the oblique fracture system shows scattering in strike and is supposed to be related to a shear event of locally left lateral strike slip whereas in the dabei anticlines the major system is hinge perpendicular fracture system nw se showing a trending of increasing fracture intensity from limbs to hinge the hinge perpendicular fractures system in the dabei anticlines consist of shear fractures and tension fractures stress inversion result shows it corresponds to northwest southeast orientation compression stage besides we analyzed petrophysical properties include porosity permeability young s module poisson ratio and compressive strength of the bashijiqike formation concerning their structural position within folds it indicates that the highest porosity and permeability are associated with dissolution and fracturing the compressive strength of different structural positions also restrict the variations of mechanical properties of rocks the best reservoir quality is suggested in the hinge zone and areas close to thrust the findings have given maybe helpful for providing favorable reservoir targets for prospecting in the compressional basin

fracture detection in oil based drilling mud using a combination of borehole image and sonic logs abstract the deeply buried 5 5 7 1 km lower cretaceous bashijiqike sandstones are important fractured reservoirs in the kuqa depression in these high temperature high pressure drilling environments oil based muds are used to limit drilling risks and improve efficiency making facture detection using resistivity based image logs difficult the maximum horizontal stress sh max trends close to north south 0 10 based on orientations of the drilling induced fractures and borehole breakouts core descriptions thin sections and image logs used to describe the fractures in the bashijiqike sandstone reservoirs show that opening mode natural fractures are common and the fractures range from fully open to sealed by calcite and clay minerals the open fractures are dominantly steeply dipping or vertical and primarily strike north south locally horizontal fractures or fractures with low angle dip are detected we compare fracture visibility on image logs acquired in the same ks 2 2 12 key well in oil based mud and water based mud fmi hd logs successfully detect large 0 1 mm aperture vertical fractures in oil based mud better than obmi image logs and the two imaging tools have a similar ability in detecting the high dip angle fractures since the ubi tool is not affected by oil based muds most of the fractures can be picked out on ubi images minor negative deviations of bulk density could be observed in fractured zones and the presence of fractures obviously causes an increase in sonic transit time full waveforms from dsi tools combined with electrical image logs detect fractured zones both the velocity and amplitude of the sonic waves are sensitive to fractures and the fractured zones could be identified according to the attenuation of stoneley waves the combination of cores image logs and full wave sonic logs offers comprehensive detection of fractures in oil based mud environments

studies of internal gravity waves at halley base antarctica using wind observations at halley base which is situated on the brunt ice shelf in antarctica internal gravity waves are frequently observed in the stably stratified atmospheric boundary layer in this paper time series of wind speed and direction at a height of 8 m observed from three meteorological masts are used to determine some of the physical properties of the waves such as their wavelengths phase speeds and directions of propagation the relationship of the results to various theories of the generation of internal gravity waves is considered it is shown that the waves do not usually propagate in the direction of the surface wind typically the direction of propagation is rotated about 45 clockwise from the wind vector the waves most frequently propagate from a direction of about 135 which is perpendicular both to the hinge line line where the ice shelf meets the land and to the ridges in the ice shelf suggesting a topographic influence it is shown that the waves obey a dispersion relation similar to that for neutral trapped internal gravity waves

influence of overthrusting on maturation of hydrocarbons in phosphoria formation wyoming idaho utah overthrust belt geochemical analyses were performed on 11 phosphoria formation samples collected throughout the wyoming idaho utah overthrust belt maturation models incorporating the thermal effects of thrust faulting with lopatin s techniques were then used to interpret these geochemical data in particular four of the sample sites were selected for detailed thermal modeling these four sites include one sample site in an area unaffected by thrusting two sites located in the hanging walls of major thrusts and one site in the footwall of the darby thrust the detailed thermal modeling shows overthrusting did affect the thermal history of the phosphoria formation the effect of thrusting was to cool the overriding sheet and warm the sediments being overridden thus the hanging wall samples had a different post thrusting thermal history than the footwall sample cooling of the hanging wall slowed post thrusting maturation in the two thrust sheet samples in contrast the footwall sample was exposed to higher temperatures after thrusting and the maturation process was accelerated results of this study indicate that tectonism influences the thermal history of the rocks and should be included in any reliable source rock evaluation program involving overthrust strata a simple evaluation based only on the thickness of the overburden in general will not be sufficient to explain fully the maturation data in the absence of actual geochemical information such as ro tai or cai the models described in this paper appear to be sufficiently accurate to give a reasonable estimate of thermal maturity of a potential source bed

the synoptic setting and possible energy sources for mesoscale wave disturbances abstract thirteen case studies of mesoscale wave disturbances characterized by either a singular wave of depression or wave packets with periods of 1 4 h horizontal wavelengths of 50 500 km and surface pressure perturbation amplitudes of 0 2 7 0 mb are reviewed to isolate common synoptic features for these cases and to shed light on possible energy sources for the waves a strong thermal inversion in the lower troposphere north of a frontal boundary and a jet streak propagating toward a ridge axis in the upper troposphere are commonly observed in all the cases in general the area of wave activity is bounded by the jet axis to the west or northwest a surface front to the southeast an inflection axis between the trough and ridge axes to the southwest and the ridge axis to the northeast the conditions specified by lindzen and tung as being necessary to form a wave duct which include the existence of the lower tropospheric inversion seem to be met in many of these cases this suggests that a du

thermal and maturation history of jurassic source rocks in the kuqa foreland depression of tarim basin nw china abstract kuqa foreland depression of the tarim basin is one of the largest gas production provinces in china thermal history reconstruction using vitrinite reflectance data indicates that the palaeo heat flow in kuqa depression was relatively high 50 55 mw m 2 during the mesozoic but gradually decreased during the cenozoic to reach the present value of 40 50 mw m 2 the cooling of the kuqa depression is probably attributed to the crust thickening and the rapid sedimentary rate the jurassic source rocks entered conventional oil window at 100 ma and began to generate gas at approximately 75 ma in the kelasu area thermal maturation of the jurassic source rocks accelerated significantly since 23 3 ma especially in the recent 5 2 ma in this foreland depression source rock maturation which is likely controlled mainly by burial history also influenced by the presence of fault thrusting and salt bearing formations

impact of geomorphological changes to harbor resonance during meteotsunamis the vela luka bay test case in engineering studies harbor resonance including quality and amplification factors is typically computed for swell and waves with periods shorter than 10 min however in various locations around the world such as vela luka bay in croatia meteotsunami waves of periods greater than 10 min can excite the bay or harbor natural modes and produce substantial structural damages in this theoretical study the impact of some geomorphological changes of vela luka bay i e deepening of the bay dredging the harbor adding a pier or a marina to the amplification of the meteotsunami waves are presented for a set of 6401 idealized pressure wave field forcing used to derive robust statistics the most substantial increase in maximum elevation is found when the vela luka harbor is dredged to a 5 m depth which is in contradiction with the calculation of the quality factor showing a decrease of the harbor natural resonance it has been shown that the forcing energy content at different frequency bands should also be taken into account when estimating the quality and amplification factors as their typical definitions derived from the peak frequency of the sea level spectrum fail to represent the harbor response during meteotsunami events new definitions of these factors are proposed in this study and are shown to be in good agreement with the results of the statistical analysis of the vela luka bay maximum elevation results in addition the presented methodology can easily be applicable to any other location in the world where meteotsunamis occur

oil and gas developments in western canada in 1989 there were 5513 wells drilled in western canada during 1989 30 fewer than in 1988 total meterage drilled was 6 459 797 m for an average well depth of 1172 m exploratory drilling in 1989 dropped by 13 and development drilling by 40 from 1988 levels british columbia was the only area in western canada with increased activity the industry continued to acquire more acreage for less total bonus at provincial crown sales throughout western canada during 1989 3 564 827 ha were acquired for a total bonus of 484 872 000 footnote 5 although the total disposition of crown lands decreased only 4 the average bonus dropped to 136 ha down 26 from 1988 in alberta the most active exploration areas were the southern and eastern mesozoic gas play the western deep devonian gas play the oil plays on and adjacent to the peace river arch and the middle devonian carbonate oil plays in the northwest in british columbia the most active exploration areas were the mesozoic and paleozoic gas plays in the northeastern portion of the province for the first time in 5 years crown drilling rights were issued within the fraser valley in the southwest there was a focus on gas exploration in the province as pipeline reversal was implemented permitting access to canadian and california markets through the alberta transportation network in manitoba exploration and development activity continued to decline in northern canada exploratory drilling success offering of crown lands for exploration approval of gas exports and indications that many of the native lands claims may be approaching settlement all provided exploration encouragement for the next decade exploration activities occurred throughout the northwest territories from the offshore beaufort to the southern border in saskatchewan active exploration areas were shallow mesozoic gas plays in the western portions of the province and deep paleozoic oil plays in the south

organic geochemistry of oil and gas in the kuqa depression tarim basin nw china abstract the kuqa depression in the tarim basin nw china contains significant natural gas and condensate resources with only small amounts of black oil this study demonstrates that the primary reason for the accumulation of large natural gas reserves in the kuqa depression is the high maturity level of the jurassic coal bearing sequence that is currently at the peak stage of dry gas generation from the combined stable carbon isotopes and molecular biomarker data it is possible to identify two separate source rocks for the discovered hydrocarbon fluids the gases were primarily from the middle lower jurassic coals and associated clastic rocks and the oils were from the upper triassic lacustrine mudstones peak oil generation from the triassic source rocks occurred during the early miocene 23 12 ma b p these oils migrated laterally over relatively long distances 20 50 km reaching the outer periphery of the depression peak gas generation took place more recently perhaps during the past 5 ma the gases migrated mainly along faults over relatively short lateral distances resulting in accumulations adjacent to the over matured source kitchens different timings for the trap formation along the north and south margins and a late injection of gas into early oil accumulations provided favorable conditions for the formation of evaporative condensates and the preservation of gas pools in the more down dip reservoirs and oil pools in the more up dip locations

a theoretical study of large sea level oscillations in the western mediterranean large sea level oscillations up to 1 m amplitude and around 10 min period have been observed in several bays and harbors of the western mediterranean these oscillations appear to be associated with short period 10 min atmospheric pressure fluctuations amplitude of 1 5 mbar using a model with a flat shelf and a sloping bottom harbor we found that these oscillations were the result of a three way resonant coupling between an atmospheric gravity wave a coastally trapped edge wave and the normal modes of a harbor the amplification mechanism was studied for the harbor of ciutadella good agreement between the predicted and the observed frequencies and amplitudes is found

open shear fractures at depth in anticlines insights from the kuqa foreland thrust belt tarim basin shear fractures that close under compressive stress regime were described by previous workers here we show the existence of hinge parallel shear opening mode fractures at a certain depth within an anticline structure through core observations formation micro imager fmi log interpretations and production data studied reservoir is a tight sandstone body of cretaceous age which is emplaced in ks2 anticline with depth ranging between 6000 and 8100 m we explore the mechanism of hinge parallel shear fractures by stereographic technique and backtilting as well as show field evidences for opening displacements these shear fractures mainly consist of vertical tension set moderate dipping shear set steeply dipping shear set and sub horizontal shear set crosscutting relationships and surface textures suggest that although the moderate dipping shear set is older and maybe sealed by cements it may have been opened by local stress due to outer arc extension through folding calcite bridges with rhombohedral structures may support fracture walls helping them to remain open in case of compressive stress our work documents shear fracture openings in the anticline at depth and fluid flow in subsurface reservoirs

global geologic history and distribution of hydrocarbon reserves a review of global geologic history during seven major periods between the cambrian and the holocene reveals the principal factors influencing the distribution of world hydrocarbon reserves the paleozoic reserves located mainly in north america and europe are mostly related to stable platform environments the mesozoic and tertiary reserves are found in more diverse tectonic environments represented mainly by the mesogean tethyan realm passive margins and the western american mobile belts the mesogea tethys formed a latitudinal feature separating gondwana and laurasia the mesogean realm contains 69 of the world oil and gas reserves divided almost equally between the gondwana and laurasia areas the voluminous reserves in the mesogean realm reflect the history of repeated opening and closing of the mesogea ocean that resulted in several phases of basin development the comparative isolation of the basins from the global ocean circulation favored preservation f organic matter because of diagenesis the thermal history and migration the ultimate hydrocarbon reserves generally decrease as the ages of the reservoir and source rocks increase migration is usually directed toward the higher parts of the stratigraphic section concentrations of reserves within particular age ranges apparently reflect development of two major categories of basins 1 marine platform basins which were dominant in the devonian jurassic and cretaceous periods and 2 rapidly subsiding basins which were dominant in the late tertiary and probably during the late carboniferous pennsylvanian the middle east has an exceptional volume of sediments prolific source rocks and well preserved hydrocarbons and it is not likely that another hydrocarbon province of comparable importance will be found moreover these middle east reserves do not give any anomalous weight to the total reserves of the gondwanian areas when compared to those in the laurasian areas

numerical modelling of the destructive meteotsunami of 15 june 2006 on the coast of the balearic islands a destructive tsunami like event locally known as rissaga waves occurring on 15 june 2006 in ciutadella harbour menorca balearic islands is reproduced by a numerical model forced by a travelling atmospheric disturbance the disturbance is reconstructed from microbarograph measurements being the only available instrumental data at the time of the event the model is verified based on two weaker 1997 events which were recorded by a number of bottom pressure recorders operating at that time on the menorca shelf in ciutadella inlet and adjacent platja gran inlet both 1997 events are numerically simulated and good agreement is achieved with observations in time frequency including eigenfrequencies of the affected inlets and wave heights subsequently the same model is applied to simulate the 2006 event the vigorous currents with speeds up to 400 cm s are found to occur specifically at those areas of the harbour where the most severe damage and sinking of boats had been reported maximum simulated sea level heights of 2 5 m were about one half of those reported by eyewitnesses this difference is apparently caused by quality and spatial resolution of bathymetry data however in general the model is capable of reproducing the event fairly well and can probably be used for future assessment and mitigation activities on the coasts of the balearic islands

thermal effects of thrust faulting abstract calculations based on simple models of overthrust sheets in crystalline basement rocks show that significant thermal effects may result from their movements if rates are sufficiently high e g plate tectonic rates the thrust sheets sufficiently thick 5 10 and 15 km are modelled here the distances moved sufficiently large and for reasonable values of the coefficient of friction along the thrust plane overthrusting can cause metamorphic mineral zonations and heat flow anomalies observable in the field regions where large scale overthrusting has occurred should be characterized by a decrease with depth of grade of metamorphic mineral assemblages and anomalously low heat flow the theoretical effects are presented as a series of maximum temperature vs depth and heat flow vs time plots

evolutionary phases of equatorial spread f including l band scintillations and plumes in the context of gps total electron content variability a case study 1 the evolution of large scale few kilometers medium scale few hundreds of meters and small scale meters size plasma density irregularities in the postsunset equatorial f region in the context of characteristic gps total electron content gtec variations are reported from indian longitudes the ionograms and gtec from a gps receiver installed as a part of the gps aided geo augmentation network gagan project for satellite based navigation are obtained from an equatorial station at trivandrum 8 5 n 76 91 e dip latitude 0 5 n the variations in the gtec with respect to tec are considered to represent the seed perturbations for the plasma instability that results in the equatorial spread f esf irregularities and are treated as a perturbation factor p the vhf radar at gadanki 13 5 n 79 17 e dip latitude 6 4 n provided the small scale structures of esf the background thermospheric conditions that affect the growth of the plasma instability through ion neutral collision frequency in are estimated using the f region base height h f and the representative scale height of the neutral atmosphere and are represented by a growth factor g the present case study reveals a close coupling between the background ionospheric conditions and the baseline perturbations in deciding the evolutionary phases of esf it has been shown that although large scale kilometer scale irregularities are formed without any constraints when the background ionospheric thermospheric conditions are favorable in the presence of fluctuations in gtec consistently the medium scale and small scale irregularities show remarkable similarity with the variations in the product of the perturbation and growth factors

the mad sea phenomenon in the strait of sicily sea level observations at cape bon tunisia and mazara del vallo sicily show that large coherent oscillations exist across the strait of sicily with significant energy bands centered at periods of 35 3 41 6 50 6 75 8 and 134 5 min whose possible structure is confirmed by a numerical approximation to the gravitational barotropic normal modes with realistic topography it is observed that these oscillations are related to the passage of synoptic weather systems over the region an investigation on the configuration phase velocity and direction of approach of atmospheric disturbances over the region suggests that the oscillations in the strait of sicily could be forced by instabilities that develop in large scale low pressure fronts that propagate as pressure gravity waves with an approximate phase speed between 24 and 30 m s21

meteorological tsunami of 19 march 2017 in the persian gulf observations and analyses on 19 march 2017 destructive tsunami like waves impacted the northeast shore of the persian gulf pg the maximum surveyed runup of about 3 m was observed at dayyer in southern iran where damaging waves inundated the land for a distance of 1 km and resulted in the deaths of five people because the pg has always been considered safe from extreme oceanic waves the event was totally unexpected in this study we examined sea level data from 12 stations across the pg and a variety of meteorological information including satellite imagery high altitude isohypse maps and high resolution air pressure records from 47 instruments along the pg our results show that the event was very local with recorded maximum trough to crest wave heights of 197 cm at dayyer and 234 cm at asaluyeh near field cities in iran located 80 km apart the dominant wave periods were in the range of 15 20 min at all distant tide gauges the observed wave heights were 35 cm no earthquakes or landslides were evident at the time of the event on the other hand atmospheric processes during 18 22 march were very active and 10 distinctive tsunamigenic air pressure disturbances were observed propagating over the pg suggesting that the event of 19 march 2017 was a meteorological tsunami atmospheric conditions over the pg were highly favourable for the generation of meteotsunamis and very similar to those that caused a chain of strong meteotsunamis in the mediterranean and black sea regions during 23 27 june 2014 based on the 500 hpa wind we evaluated that the disturbances had propagation speeds of 21 38 m s with the disturbance at dayyer having a speed of 26 m s toward 77 true the froude number fr estimated as the ratio of the air disturbance speed to the long wave speed on 19 march 2017 in the dayyer asaluyeh region was close to resonance fr 0 9 to 1 1 which is highly favourable for meteotsunami generation our findings indicate that the dayyer asaluyeh area is a hot spot that is highly vulnerable to extreme weather induced tsunami like waves

pressure forced seiches of large amplitude in inlets of the balearic islands 2 observational study in part 1 of this study gomis et al 1993 proposed a possible mechanism for the generation of large amplitude seiches observed in inlets of the balearic islands in part 2 we revise the proposed mechanism in light of recent observations these consist of simultaneous records of sea level bottom pressure measured at three locations inside and outside ciutadella inlet and atmospheric pressure measured at four sites inland nearby first results that support the existence of offshore surface waves of atmospheric origin are shown next a detailed analysis of atmospheric data reveals the passage of non dispersive waves with a predominant direction and phase speed that seem to be about the same during seiche events finally coherence phase difference and admittance functions estimated for different pairs of instruments are compared with the theoretical results all observations indicate that large amplitude seiches observed in ciutadella are likely the result of a resonant coupling between offshore surface waves generated by atmospheric disturbances and the fundamental mode of that inlet as suggested in part 1 however the analytical model used in part 1 is clearly too simple to explain the observed characteristics of the offshore surface waves

genetic classification of petroleum systems our genetic classification of petroleum systems is founded on a simple working nomenclature that consists of combining qualifiers from each of the following three categories 1 charge factor supercharged normally charged or undercharged 2 migration drainage style vertically drained or laterally drained and 3 entrapment style high impedance or low impedance the charge factor is estimated on the basis of the richness and volumetrics of mature source rocks the source potential index spi which combines source rock richness and thickness into a single parameter is a convenient shortcut for comparing the petroleum potential of diverse source rocks containing dissimilar kerogen types and for rapidly estimating regional charging capacity in extensively explored basins a positive correlation exists between the magnitude of spi and basin wide petroleum reserves the migration drainage style is determined from the structural and stratigraphic framework of a basin vertical migration drainage which occurs mainly through faults and fracture systems breaching a seal is characteristic of petroleum systems contained within rift basins deltaic sequences salt dome provinces wrench basins and fold and thrust belts in contrast lateral migration drainage is dominant wherever stratigraphically continuous seal reservoir doublets extend over a very large area in a tectonically stable province e g commonly foreland or intracratonic platform basins recognition of the dominant migration style helps to predict the location of zones of petroleum occurrence in relation to the hydrocarbon kitchens the entrapment style which is also dependent on the structural framework and the presence and effectiveness of seals describes the degree of resistance i e impedance working against dispersion of the petroleum charge application of these working concepts should help to significantly reduce geologic risk particularly in new ventures type exploration

influence of syntectonic sedimentation and decollement rheology on the geometry and evolution of orogenic wedges analog modeling of the kuqa fold and thrust belt nw china

influence of retained bitumen in oil prone shales on the chemical and carbon isotopic compositions of natural gases implications from pyrolysis experiments abstract retained bitumen in oil prone source rocks has a significant impact on late gas generation but such influence is still poorly quantified because it is quite difficult to restore the bitumen content retained in a mature source rock in this study a suite of artificially matured samples were prepared from a moderate maturity shale sample to represent shales with different amount of retained bitumen these samples were then pyrolyzed in sealed gold tubes to investigate how the amount of retained bitumen affects the changes in chemical and carbon isotopic compositions of generated gases and the uncertainty of the evaluation of gas maturity and source identification the results indicate that the decrease in yields of hydrocarbon gases is proportional to the reduction of retained bitumen content however a progressive enrichment in heavier carbon isotope 13c of gaseous hydrocarbons occurs while less amount of bitumen is retained in shales this experimental observation partly explains the heterogeneity of methane carbon isotopes for shale gases that have identical thermal maturity levels although the amount of retained bitumen can significantly change the carbon isotopic ratios of individual gas 13c1 13c2 and 13c3 the difference in carbon isotopic composition between gaseous components such as ethane and methane 13c2 13c1 or propane and ethane 13c3 13c2 are not significantly affected and therefore these differential values can be potentially used as maturity indicators for overmature natural gases exhibiting no carbon isotopic reversals geochemical and carbon isotopic diagrams that are widely used for the identification of oil and kerogen cracking gases are also found to be affected by the retained bitumen content these results illustrate that it is necessary to take into account the retained bitumen content of shales when thermal maturity and genetic origin of natural gases derived from oil prone source rocks are being evaluated

geochemical evidence for coal derived hydrocarbons and their charge history in the dabei gas field kuqa thrust belt tarim basin nw china abstract large to middle scale thrust structures are important reservoir plays for coal derived hydrocarbons in the foreland basins of nw china with both gas and some accompanying oil in the dabei gas field of the kuqa thrust however the oil and gas pools are vertically distributed in a quite unique way 1 liquid oil and some dissolved gas are present in the dawanqi anticline with the reservoir at 300 700 m depth forming the only oil field in the kuqa thrust 2 gas and minor accompanying oil are found in the deep reservoir of the dabei 1 and dabei 2 thrust traps around 5000 6000 m depth 3 an extremely dry gas pool is found in the dabei 3 thrust trap where the depth of the reservoir is over 7000 m geochemical data suggest that the hydrocarbons in the dawanqi anticline and the dabei thrust traps originated from a similar source i e the underlying jurassic coal measures with some contribution from jurassic lacustrine shales the jurassic source rocks did not start to generate oil until the miocene around the kangcun stage and extended into the pliocene the kuche stage with the main gas generation period in the pliocene the kuche stage and the quaternary because the traps formed relatively early the dabei 1 and dabei 2 thrusts could trap some of the early generated oils but most of the early charged oil was redistributed to the shallower dawanqi anticline during the kuche stage the dabei 3 thrust trap formed concurrently with major gas generation and thus could not trap liquid hydrocarbons the difference in the vertical distribution of the hydrocarbon accumulations in the dabei gas field resulted from a complex interplay of source variability structural evolution of the basin and thermal maturation

petroleum geology of kela 2 the most productive gas field in china abstract the kela 2 gas field located in the kuqa depression of tarim basin is the most productive gas field in china based on per unit surface acreage the gas trap is a subsurface anticline formed along an e w trending thrust belt in front of the southern tianshan mountains the gas pay zones are located in fine grained sandstones of a fan delta front facies in the lower cretaceous bashijiqik formation k l bs and eogene evaporitic rocks serve as regional cap rocks the gases were derived primarily from over mature jurassic coal measures peak gas generation and final shaping of the kela 2 structure occurred relatively late in the late himalayan orogeny 5 0 ma thrust faulting appears to have played a significant role in the hydrocarbon generation migration accumulation and preservation in this foreland basin detailed delineation of the kela 2 gas field indicates that high quality regional cap rocks are essential for the formation of the super rich abnormally pressured giant gas fields while buried anticlines under the overthrust zone are the favorable gas habitat late gas accumulation is considered to be decisive for the conservation of the giant gas fields

salt structures and hydrocarbon accumulations in the tarim basin northwest china the tarim basin is one of the most important hydrocabon bearing evaporite basins in china four salt bearing sequences the middle and lower cambrian the mississippian the paleogene and the neogene have various thickness and areal distribution they are important detachment layers and intensely affect the structural deformation in the basin the kuqa depression is a subordinate structural unit with abundant salt structures in the tarim basin salt overthrusts salt pillows salt anticlines salt diapirs and salt withdrawal basins are predominant in the depression contraction that resulted from orogeny played a key function on the formation of salt structures growth strata reveal that intense salt structural deformation in the kuqa depression occurred during the himalayan movement from oligocene to holocene with early structural deformation in the north and late deformation in the south growth sequences also record at least two phases of salt tectonism in the yingmaili tahe and tazhong areas low amplitude salt pillows are the most common salt structures and these structures are commonly accompanied by thrust faults the faulting and uplifting of basement blocks controlled the location of salt structures the differences in the geometries of salt structures in different regions show that the thickness of the salt sequences has an important influence on the development of salt cored detachment folds and related thrust faults in the tarim basin salt sequences and salt structures in the tarim basin are closely linked to hydrocarbon accumulations oil and gas fields have been discovered in the subsalt intrasalt and suprasalt strata salt deformation has created numerous potential traps and salt sequences have provided a good seal for the preservation of hydrocarbon accumulations large and small scale faults related with salt structures have also given favorable migration pathways for oil and gas when interpreting seismic profiles special attention needs to be paid to the clastic and carbonate interbeds within the salt sequences because they may lead to incorrect structural interpretation in the tarim basin the subsalt anticlinal traps are good targets for hydrocarbon exploration

analytical studies of low level internal gravity waves over the kanto plain associated with a stationary front abstract an observational analysis of the low level internal gravity waves over the kanto plain in japan on 17 october 1998 was performed the data from the doppler radar for airport weather draw as well as aircraft communications addressing and reporting system acars data of wind and temperature provided unique observations with high spatial and temporal resolutions and were used to analyze detailed wave structures and environmental conditions especially the wave trapping mechanism according to the data analysis the horizontal wavelength was approximately 7 km the ground relative phase speed of the waves was approximately 1 m s 1 and the direction of propagation was toward 50 ne the profiles from acars revealed that the scorer parameter decreased rapidly with height above 1500 m agl and became less than the horizontal wavenumber near 2600 m agl these results indicate that the atmosphere acts as a duct and the waves were trapped vertically and reflected downward the observed horizontal wa

deterministic prediction of post sunset esf based on the strength and asymmetry of eia from ground based tec measurements preliminary results 1 this paper provides the first observations of eia asymmetry by receiving beacon transmissions onboard low earth orbiting satellites from a single station ground based receiver the eia strength and asymmetry are derived from the latitudinal profiles of tec obtained from a radio beacon receiver at trivandrum 8 5 n 77 e diplat 0 5 n these two parameters obtained well ahead of the onset time ol esf are shown to have a definite role on the subsequent esf activity in the present paper both these factors are combined to define a new threshold parameter for the generation ol esf it has been shown that this parameter can define the state of the background ionosphere conducive for the generation of esf irregularities much prior to its onset

atmospheric origin of the devastating coupled air sea event in the east adriatic enhanced sea level oscillations with devastating effects occurred on 26 27 june 2003 in the east adriatic the phenomenon was recognized as a resonantly coupled air sea interaction where the sea wave is forced by the propagating atmospheric pressure disturbance this study examines the dynamics and predictability of the atmospheric component of the coupled system first the initiation amplification and maintenance of the system are examined the source of the perturbation is traced back to the alpine region where the potentially unstable air in the westerly current lifts over the alps resulting in convection and wave development the wave and convective activity apparently couple in a wave cisk manner and propagate southeastward down the eastern adriatic coast due to the potentially unstable air above the adriatic the system additionally amplifies along its track the dissipation of the system occurs after the landfall second the performance of the numerical model at the resolution that is similar to operational nwp model resolution is examined this severe event is highly susceptible to the details of the model configuration presumably due to the sensitivity in coupling of the wave and mcs thus although the model is able to reproduce and forecast this kind of event at a fairly coarse resolution the details of the spatial structure as well as the time of onset are questionable in this case the greatest sensitivity is primarily in the treatment of moist and convective processes

meteotsunami marrobbio of 25 26 june 2014 on the southwestern coast of sicily italy a major tsunami like event locally known as marrobbio impacted the southwestern coast of sicily on 25 26 june 2014 the event was part of a chain of hazardous episodes in the mediterranean and black seas during the last week of june 2014 resulting from an anomalous atmospheric system tumultuous atmosphere propagating eastward over the region the synoptic patterns and vertical structure of the atmosphere over sicily at the time of the event indicate that atmospheric wave ducting was responsible for the generation of tsunamigenic air pressure disturbances that produced especially high sea level responses meteotsunamis at certain sites along the sicilian coast the strongest sea level oscillations were observed at mazara del vallo where a 1 m meteotsunami bore propagating upstream in the mazaro river was generated the combined effects of external resonance proudman resonance on the western sicilian shelf and internal resonant conditions bathymetric and topographic characteristics of specific sites were found to be the key factors that caused the meteotsunami marrobbio phenomenon on the coast of sicily and the meteobore at mazara del vallo

effects of the vertical plasma drift velocity on the generation and evolution of equatorial spread f we use radar observations from the jicamarca observatory from 1968 to 1992 to study the effects of the f region vertical plasma drift velocity on the generation and evolution of equatorial spread f the dependence of these irregularities on season solar cycle and magnetic activity can be explained as resulting from the corresponding effects on the evening and nighttime vertical drifts in the early night sector the bottomside of the f layer is almost always unstable the evolution of the unstable layer is controlled by the history of the vertical drift velocity when the drift velocities are large enough the necessary seeding mechanisms for the generation of strong spread f always appear to be present the threshold drift velocity for the generation of strong early night irregularities increases linearly with solar flux the geomagnetic control on the generation of spread f is season solar cycle and longitude dependent these effects can be explained by the response of the equatorial vertical drift velocities to magnetospheric and ionospheric disturbance dynamo electric fields the occurrence of early night spread f decreases significantly during equinox solar maximum magnetically disturbed conditions due to disturbance dynamo electric fields which decrease the upward drift velocities near sunset the generation of late night spread f requires the reversal of the vertical velocity from downward to upward for periods longer than about half an hour these irregularities occur most often at 0400 local time when the prompt penetration and disturbance dynamo vertical drifts have largest amplitudes the occurrence of late night spread f is highest near solar minimum and decreases with increasing solar activity probably due to the large increase of the nighttime downward drifts with increasing solar flux

gas systems in the kuche depression of the tarim basin source rock distributions generation kinetics and gas accumulation history abstract six petroleum source beds have been developed in the kuche depression also known as kuqa depression of the tarim basin including three lacustrine source rocks middle and upper triassic kelamayi and huangshanjie formations and middle jurassic qiakemake formation and three coal measures upper triassic taliqike formation lower jurassic yangxia formation and middle jurassic kezilenuer formation while type i ii organic matter occurs in the middle jurassic qiakemake formation j2q other source beds contain dominantly type iii organic matter gas generation rates and stable carbon isotopic kinetics of methane generation from representative source rocks collected in the kuche depression were measured and calculated using an on line dry and open pyrolysis system combined with hydrocarbon generation history modelling the formation and evolution processes of the jurassic triassic highly efficient gas kitchens were established high sedimentation rate in the neogene and the fast deposition of the kuche formation within the pliocene 5 ma in particular have led to the rapid increase in mesozoic source rock maturity resulting in significant dry gas generation the extremely high gas generation rates from source kitchens have apparently expedited the formation of highly efficient gas accumulations in the kuche depression because different mesozoic source rocks occur in different structural belts the presence of both lacustrine and coaly gas kitchens during the cenozoic time can be identified in the kuche depression as shown by the chemical and stable carbon isotope compositions of the discovered gases the formation of the giant gas pools in the kela 2 dina 2 yaha and wucan 1 have involved very different geological processes due to the difference in their gas source kitchens

isotopic reversals with respect to maturity trends due to mixing of primary and secondary products in source rocks abstract carbon isotopic composition 13 c reversals with respect to maturity trends have been reported for ethane and propane in barnett shale gas in the fort worth basin u s a this trend also exists in some conventional gas reservoirs such as in the ordos basin china and appalachian basin u s a fractionation during mass transport is unlikely to be a significant mechanism because its effect is minor under geological conditions it would have caused more obvious reversal for methane than for ethane and propane and mass transport can not account for the occurrence of the trend both inside and outside source rocks this paper demonstrates that the reversal may result from mixing of indigenous primary gas generated directly from kerogen and secondary gas generated from oil and condensate within source rocks and presents deconvolution results using end members derived from a kinetic isotope fractionation model the results including the wetness and mixing ratio of primary and secondary gases are consistent with geological conditions condensates may be the major precursor of the secondary gas in shale when the reversal occurs a complete trend of 13 c variations in methane and ethane with maturity is proposed that is based on the indigenous mixing mechanism

global basin classification system a proposed system classifies sedimentary basins worldwide into specific as well as general categories the geologic history of each basin may be subdivided into cycles using three parameters basin forming tectonics depositional sequences and basin modifying tectonics sedimentary basins may be simple with one or two tectonic sedimentary cycles or they may be complex polyhistory basins with many different cycles and events there are eight simple cycle types in this classification which cover continental continental margin and oceanic areas the eight basic cycle types their depositional fills and tectonic modifiers have been given letter and number symbols so that the specific geologic history of each basin may be written as a formula these formulas may then e compared and similarities or differences between basins noted

pressure forced seiches of large amplitude in inlets of the balearic islands large amplitude harbor seiches usually occur in summer in the balearic islands a significant correlation between sea level oscillations and atmospheric pressure disturbances has been found though a proved physical mechanism to account for this atmosphere ocean interaction is still missing using a flat bottom shallow water model we show that a direct coupling between atmospheric pressure and the free mode of an inlet is unlikely but that an oceanic wave of atmospheric origin can act as an intermediate mechanism and adequately force the inlet by resonance the phase relationship derived from this mechanism is in good agreement with observations provided the whole spectrum of oceanic waves is in opposite phase to the generating atmospheric disturbance we also show that the very large oscillations observed at ciutadella an elongated shallow inlet in the west coast of menorca balearic islands can be explained in terms of the particular shape of this inlet