estimation of changes in water column velocities and thicknesses from time lapse seismic data sea bed diffractions are frequently observed for several of the fields in the norwegian sea and the barents sea this is a challenge in time lapse seismic analysis since diffracted multiples are difficult to remove by processing and therefore is a major source of poor time lapse data quality in this work we test if the diffractions can be used for enhanced 4d interpretation by analysing the time shift of the sea bed diffraction hyperbola between the base and monitor it is tested if changes in water velocity and tides can be estimated two models using time lapse diffraction analysis are tested the first one simply adds time shifts for the two branches of the diffraction hyperbola and this average time shift is then used to estimate the water velocity change the other method uses an inversion method based on the diffraction equation for a point diffractor to estimate the velocity change in line common midpoint shifts are estimated by subtracting the time shifts of both hyperbola branches followed by direct inversion the diffraction based time shifts are compared to time shifts estimated by standard cross correlation of the sea bed reflection the averaging method gives slightly higher uncertainties while the inversion using an exact traveltime equation gives similar uncertainties compared to the sea bed reflection method

changes in bulk properties and molecular compositions within new zealand coal band solvent extracts from early diagenetic to catagenetic maturity levels abstract the bulk properties and bitumen molecular compositions of a rank series of 38 humic coals from the new zealand coal band cretaceous cenozoic have been analysed to investigate early maturation processes affecting coaly organic matter through diagenesis to moderate catagenesis rank s r 0 0 11 8 r o 0 23 0 81 the samples comprise a relatively restricted range of vitrinite rich coal types formed largely from higher land plant material under relatively oxic conditions but with a significant contribution from microbial biomass with increasing rank total organic carbon contents show a general increase whereas moisture and asphaltene contents decrease bitumen yields also decrease through the stages of diagenesis and early catagenesis rank s r r o r 5 6 r o 0 40 as indicated by the constant occurrence and gradual increase of isoprenoids e g pristane and phytane and hopanoids in their more mature configuration this early phase of catagenesis not previously recognised in new zealand coals is followed at rank s r 9 r o 0 55 by the main catagenesis phase characterised by a more rapid increase in the generation of hydrocarbons including total n alkanes isoprenoids and hopanes changes in the maturity of new zealand coals can be traced by the carbon preference index and several hopane maturity parameters including 22 s 22 s 22 r and

carbon dioxide generation from coals in taranaki basin new zealand implications for petroleum migration in southeast asian tertiary basins elevated co2 levels in gas accumulations within the onshore area of the taranaki basin can be quantitatively accounted for by decarboxylation of vitrinite rich tertiary coals over the lignite to early high volatile bituminous coal rank range the highest levels are found within sandstone reservoirs vertically adjacent to eocene coal seams that have realized approximately 50 of their co2 generative potential the gas exists as a supercritical fluid under reservoir conditions and appears to be generated in significant amounts comparable to liquid hydrocarbons co2 may aid oil expulsion from coals directly when intense co2 generation coincides with major oil generation or indirectly by creating pressure induced microfractures du ing the relatively rapid generation of large amounts of co2 prior to the main phase of oil generation for these effects to be realized the rate of co2 production relative to removal is considered critical and favorable conditions are probably restricted to basins that have experienced relatively rapid heating in this respect the taranaki basin provides a model for co2 evolution in many southeast asian tertiary basins

pyrolytic assessment of oil generation and expulsion from a suite of vitrinite rich new zealand coals abstract pyrolysis gas chromatography py gc of tara 1 coals great south basin new zealand suggests a mean paraffinic oil potential of 85 kg t c range 70 130 kg t c based on n alkane alkene generation in the c6 c31 range and typical proportions of these compounds in related oils from new zealand this maximum in the depth trend of pyrolysate yield is reached at 0 75 0 80 r0 comparable to the previously reported maximum in hydrogen index hi thermal extraction gc te gc provided higher yields than rock eval s1pyrolysis but without the uniform trend exhibited by s1 c below the 3 0 km below sea floor 0 75 0 80 r0 onset of expulsion in addition the saturates aromatics ratio in the thermal extract decreased with depth indicating preferential retention of aromatics which may affect the expulsion efficiency of paraffins thermal extracts suggest that at most 15 kg t c of paraffinic oil is retained within the tara coals which is lower than previous estimates of saturation threshold however it is likely to be adversely affected lowered by loss of the least volatile components during recovery and storage of cuttings and incomplete recovery of high molecular weight components particularly c40 paraffins using te gc isopimarane generation appears to be restricted to the depth zone corresponding to the early oil window although it is unclear whether this is directly related to the maturity range required for such generation or that only the latest cretaceous coals in tara 1 exhibit particularly high abundances of such gymnosperm derived diterpanes

4 d constrained depth conversion for reservoir compaction estimation application to ekofisk field ekofisk field in the norweigian sector of the north sea is a remarkable example of a strongly compacted chalk reservoir since the start of production in 1971 the water bottom has subsided by over 8 m as a result of reservoir compaction hermansen et al the field wide waterflood begun in 1989 was expected to halt pressure depletion and reservoir compaction after a few years of waterflooding ekofisk reservoir pressure began increasing but compaction and subsidence continued laboratory studies on chalk cores indicated that high porosity oil filled chalk compacts strongly when flushed with seawater these studies along with reservoir flow simulation and geomechanic modeling led to a model of a water weakening compaction sylte et al ongoing efforts deployed to monitor the reservoir compaction and seabed subsidence include twice a year compaction logging in a monitoring well daily gps measurements at the platforms and periodic bathymetry surveys nine surveys from 1970 to 1999

impact of soil moisture and convectively generated waves on the initiation of a west african mesoscale convective system a mesoscale convective system mcs case study was observed over northeast mali as part of the african monsoon multidisciplinary analysis amma on 31 july 2006 observations of this case suggest that the soil moisture heterogeneity and atmospheric gravity waves emitted from a parent mcs were important trigger mechanisms for this system this study uses high resolution met office unified model metum simulations to assess the importance of the synoptic circulation land surface and gravity waves in the initiation and development of the mcs during the early afternoon shallow convection developed over a region of dry soil within a synoptic scale convergence zone which was caused by the confluence of the southerly monsoon flow with winds associated with the circulation around the saharan heat low two pronounced waves were emitted from a nearby parent storm and propagated towards the convergence zone when the second wave reached the location of the shallow convection deep convection was immediately initiated further convective cells developed later in the afternoon over dry soil many adjacent to strong soil moisture gradients these aggregated with the main storm which later developed into the case study mcs a comparison of model simulations with without the soil moisture heterogeneity and gravity waves shows that the synoptic scale circulation and convergence zones specified by the atmospheric analysis were the most important factors for the successful simulation of the mcs if the location of the initiation of the system is to be forecast accurately the land surface that is the soil moisture must be represented adequately in order to reproduce the timing of the secondary initiation of convection correctly the model must be able to capture gravity waves that are emitted by existing systems

deep basin gas new insights from kinetic modelling and isotopic fractionation in deep formed gas precursors abstract the formation and origin of high maturity gas from tertiary sediments in the mackenzie delta have been studied using programmed temperature closed system pyrolysis mssv different open system devices and numerical models for geological predictions a sample from the type iii taglu sequence was selected as being representative for one of the major hydrocarbon prone deltaic sediments in this area artificial maturation under closed system conditions was carried out at three different heating rates 0 2 0 7 and 5 0 k min the gas composition as well as carbon isotopes of formed methane were analysed using gc fid and gcirms structural characteristics of the residual macromolecules formed during these experiments were studied at different levels of thermal stress immature 360 412 and 470 c under closed system conditions the taglu sequence forms unusually high amounts of gas at extreme levels of thermal stress the recombination of previously formed hydrocarbons with residual kerogen coal through aromatisation polycondensation reactions is the best explanation for these high temperature features a feature previoulsy reported for the heather formation north sea when the neoformed material becomes active and forms gas at high levels of maturity carbon isotopes measured on methane fall to values that are 10 lighter than those from open system gas formation networks a kinetic model for hydrocarbon formation from this neoformed organic matter has been developed this predicts that the initial phase of the neoformation processes shift from post oil formation conditions at laboratory heating rates to peri oil formation conditions when it comes to geological heating rates this may indicate that recombination reactions through aromatisation polycondensation processes partly influence the major phase of petroleum formation in nature and also justifies an enhancement of gas prospectivity at great depths especially in deep basins where source rock maturities exceed 2 5 ro

using natural maturation series to evaluate the utility of parallel reaction kinetics models an investigation of toarcian shales and carboniferous coals germany abstract open system pyrolysis is routinely performed on immature samples in order to determine the kinetic parameters of petroleum generation at both bulk and molecular levels this study tested such predictions for type ii and type iii organic matter by making calibrations with both artificial and natural maturity sequences of toarcian shales posidonia shale 0 48 1 44 rr and carboniferous vitrains 0 74 2 81 rr both natural series showed little or no compositional variability attributable to kerogen type artificially matured samples were prepared by non isothermal heating 0 7 k min of the least mature samples up to end temperatures between 375 and 470 c under either closed or open system conditions measured generation rate versus temperature curves were analyzed assuming a distributed system of activation energies and a single frequency factor in each case the resulting kinetic parameters were then used to assess bulk petroleum formation rates for geological heating conditions in the case of all artificially matured samples measured and predicted bulk petroleum formation rate vs temperature curves for each maturation stage remain within the original envelope defined by the least mature sample despite an upward shift of tmax temperatures this confirms that the reactions taking place during both the pyrolysis measurements and simulated maturation processes are the same involving mainly homolytic cracking a similar pattern of measured and predicted rate curves is reproduced by the natural maturation sequence of the toarcian shales in the maturity range of 0 53 to 1 44 rr suggesting that petroleum generation within these natural systems also results from cracking reactions and therefore that petroleum generation over geological time can be reliably extrapolated from open system pyrolysis of the appropriate immature sample by contrast significant deviations are observed for the natural coal series with measured and predicted rate curves extending beyond the immature envelopes in accordance with the pronounced increase of frequency factors and of protonated aromatic carbon concentrations this behavior is attributed to solid state aromatization reactions which compete with product generation during natural coalification but which are not reproducible to the same extent by experimental heating it is concluded that petroleum generation from vitrinitic coals over geological time cannot be reliably extrapolated from open system pyrolysis of low rank samples

an estimation method for effective stress changes in a reservoir from 4d seismics data advances in seismics acquisition and processing and the widespread use of 4d seismics have made available reliable production induced subsurface deformation data in the form of overburden time shifts inversion of these data is now beginning to be used as an aid to the monitoring of a reservoir s effective stress past solutions to this inversion problem have relied upon analytic calculations for an unrealistically simplified subsurface which can lead to uncertainties to enhance the accuracy of this approach a method based on transfer functions is proposed in which the function itself is calibrated using numerically generated overburden strain deformation calculated for a small select group of reference sources this technique proves to be a good compromise between the faster but more accurate history match of the overburden strain using a geomechanical simulator and the slower less accurate analytic method synthetic tests using a coupled geomechanical and fluid flow simulator for the south arne field confirm the efficacy of the method application to measured time shifts from observed 4d seismics indicates compartmentalization in the tor reservoir more heterogeneity than is currently considered in the simulation model and moderate connectivity with the overlying ekofisk formation

guidelines for assessing the petroleum potential of coaly source rocks using rock eval pyrolysis abstract coaly source rocks are sufficiently different from marine and lacustrine source rocks in their organic matter characteristics to warrant separate guidelines for their assessment using rock eval pyrolysis the rank threshold for oil generation is indicated by the increase in bi s1 toc at rank sr 9 10 tmax 420 430 c ro 0 55 0 6 and the threshold for oil expulsion is indicated by the peak in qi s1 s2 toc at rank sr 11 12 5 tmax 430 440 c ro 0 65 0 85 the pronounced rank related increase in hi s2 toc prior to oil expulsion renders the use of immature samples inappropriate for source rock characterisation a more realistic indication of the petroleum generative potential and oil expulsion efficiency of coaly source rocks can be gained from samples near the onset of expulsion alternatively effective hi values i e his near the onset of expulsion can be estimated by translating the measured his of immature samples along the maturation pathway defined by the new zealand or other defined coal band coaly source rocks comprise a continuum of coaly lithologies including coals shaly coals and coaly mudstones determination of the total genetic potential of coaly source rock sequences is best made using lithology based samples near the onset of expulsion

mapping the fluid front and pressure buildup using 4d data on norne field norne field in the southern part of the nordland ii area in the norwegian sea approximately 100 km north of aasgard field is producing from an fpso the main field is a horst block approximately 9 3 km figure 1 the reservoir rocks are sandstones of lower and middle jurassic age the hydrocarbon reserves consist of a gas cap 75 m mainly situated in garn formation and an oil leg 110 m mainly situated in ile and tofte formations the sandstones are very good quality with porosities and permeabilities of 25 32 and 200 2000 md respectively net to gross is close to 1 for most reservoir zones oil production started in 1997 the first 4d seismic survey was acquired in 2001 and 4d information has been actively used in subsequent reservoir management

determining the dilation factor in 4d monitoring of compacting reservoirs by rock physics models hydrocarbon depletion and fluid injection cause compaction and stretching of the reservoir and overburden layers 4d prestack seismic data can be used to detect these changes because compaction stretching causes changes in traveltimes and seismic velocities we show that by using two different petro elastic models at varying effective pressures a good approximation is to assume that the fractional changes in layer

repeatability issues of 3 d vsp data increased repeatability is recognized as one major issue for improving the time lapse seismic technology as a reservoir management tool a 3 d vertical seismic profiling vsp data set acquired over a period of two days is used to analyze how repeatable a permanent installed geophone array can be and how repeatability changes with inaccuracies in source positioning it is found that for a frequency range between 3 5 and 50 hz the difference root mean square rms level between two recorded traces belonging to two different shots is about 8 this fact shows that there is a potential for acquiring very accurate time lapse seismic data by using a permanently installed downhole geophone array repeatability variation with increasing shot separation distances is analyzed showing a rapid decrease in repeatability as the accuracy of the positioning of the repeat survey decreases horizontal geophone components show approximately the same degree of repeatability compared to the vertical component but horizontal geophone data is slightly more sensitive to positioning errors the results show that repeated 3 d vsp surveys preferably using permanently installed geophone arrays might be an efficient tool for detailed and precise monitoring of fluid and pressure changes within a hydrocarbon reservoir

comparison of rate constants for some molecular tracers generated during artificial maturation of kerogens influence of kerogen type abstract the purpose of this work is to carry out artificial maturation of various kerogens under isothermal conditions in open and closed systems and to derive kinetic parameters for specific molecular tracers such as n c 12 and n c 24 alkanes results show that individual normal alkane generation from type i and type ii kerogens follows first order kinetics in both open and closed pyrolysis systems however the normal alkanes generated from type iii samples do not follow a first order mechanism for type i and type ii kerogens slightly different rate constants are obtained for n c 12 and n c 24 generation whereas for the two type iii kerogens n c 24 is produced much faster than n c 12 combining the rate constants derived from open and closed system pyrolysis arrhenius plots were obtained for the four samples under study from which accurate sets of kinetic parameters were calculated

the kinetics of thermal degradation of individual oil generating macerals calibration with microscopical fluorescence spectrometry and bulk flow pyrolysis abstract kinetic models for petroleum generation describe petroleum formation as either a discrete set of reactions or a continuous distribution of reactions the kinetic models are normally calibrated with data from laboratory experiments this paper discusses theoretical analytical and numerical problems encountered when results of laboratory experiments are extrapolated to geological conditions an alternative approach based on geologically matured samples is presented where quantitative petrological micro fluorometric and hydrogen index data are used in multiple regression analysis to estimate transformation ratios and genetic potentials of compositionally different oil generating entities in source rocks the data are further used in combination with reconstructed time temperature histories to calculate consistent kinetic parameters for the thermal degradation of individual macerals the results both for the genetic potentials and transformation ratios are within the expected range the important aspect of the analysis is that the results were obtained by expressing the transformation ratio as a function of a fluorescence maturity parameter and hence allow increased confidence in the application of fluorescence in maturity studies

mesoscale convective systems in weakly forced large scale environments part iii numerical simulations and implications for operational forecasting abstract during a 24 h period beginning 1200 utc 11 may 1982 a series of mesoscale convective systems developed within a weakly forced large scale environment two of these systems had a large component of motion against the midtropospheric flow and propagated in a direction nearly opposite to that of the travelling upper level disturbances this evolution of convection is very different from traditional ones in which convection develops and moves more or less in phase with traveling upper level disturbances it presents a tremendous challenge for three dimensional numerical models since the initiation and evolution of convection are tied to mesoscale features that are not well observed by the conventional upper air network and may not be well approximated in the model parameterization schemes mesoscale model simulations are conducted to evaluate the ability of the model to reproduce this complex event and to examine the model sensitivities to differences in the convective trigger function and model i

rough seas and time lapse seismic time lapse seismic surveying has become an accepted tool for reservoir monitoring applications thus placing a high premium on data repeatability one factor affecting data repeatability is the influence of the rough sea surface on the ghost reflection and the resulting seismic wavelets of the sources and receivers during data analysis the sea surface is normally assumed to be stationary and indeed to be flat the non flatness of the sea surface introduces amplitude and phase perturbations to the source and receiver responses and these can affect the time lapse image we simulated the influence of rough sea surfaces on seismic data acquisition for a typical seismic line with a 48 fold stack a 2 m significant wave height sea introduces rms errors of about 5 10 into the stacked data this level of error is probably not important for structural imaging but could be significant for time lapse surveying when the expected difference anomaly is small the errors are distributed differently for sources and receivers because of the different ways they are towed furthermore the source wavelet is determined by the sea shape at the moment the shot is fired whereas the receiver wavelet is time varying because the sea moves significantly during the seismic record

multiscale convective overturning in mesoscale convective systems reconciling observations simulations and theory abstract an analysis of how parameterized convection interacts with hydrostatic explicitly resolved precipitation processes to represent multiscale convective overturning in a mesoscale resolution numerical simulation is presented critically important ingredients of the successful simulation are identified and the degree to which simulations are consistent with observations and theoretical considerations is examined of particular concern is how convective parameterization routines reconcile the deep moist absolutely unstable structures that form in mesoscale convective systems it is found that these structures arise primarily from resolvable scale vertical motion and that the model responds to these structures not only by maintaining parameterized convection but also by developing a hydrostatic manifestation of convective overturning on its smallest resolvable horizontal scales the strongest and most distinctive mesoscale perturbations develop in regions where the mesoscale contribution to convectiv

numerical simulation of tornadogenesis in a high precipitation supercell part i storm evolution and transition into a bow echo abstract a nested grid primitive equation model rams version 3b was used to simulate a high precipitation hp supercell which produced two weak tornadoes six telescoping nested grids allowed atmospheric flows ranging from the synoptic scale down to the tornadic scale to be represented in the simulation all convection in the simulation was initiated with resolved vertical motion and subsequent condensation latent heating from the model microphysics no warm bubbles or cumulus parameterizations were used part i of this study focuses on the simulated storm evolution and its transition into a bow echo the simulation initially produced a classic supercell that developed at the intersection between a stationary front and an outflow boundary as the simulation progressed additional storms developed and interacted with the main storm to produce a single supercell this storm had many characteristics of an hp supercell and eventually evolved into a bow echo with a rotating comma head structure an analysi

changes in reservoir heterogeneity and quality as a response to high partial pressures of co2 in a gas reservoir new zealand abstract the kapuni field is the largest onshore petroleum field in new zealand and produces co2 rich gas c 40 45 mol co2 diagenesis within the reservoir is dominated by co2 related reactions that have resulted in localised precipitation of kaolin abundant quartz calcite dolomite and siderite along with localised generation of secondary porosity most of the co2 in the reservoir is thought to have been sourced from intraformational coals with subsequent up dip migration to the crest of the kapuni structure during migration co2 will have dissolved into undersaturated pore fluids and the resulting acidic pore fluids catalysed feldspar and minor carbonate dissolution thereby providing ions for precipitation of authigenic minerals timing of the diagenetic reactions as determined by paragenetic observations and fluid inclusion analysis suggests that both quartz and carbonate formed at a very late stage 100 c corresponding to 0 4 ma which is consistent with modelled maturation and expulsion of co2 from intraformational source rocks 5 ma to present the carbon isotope composition of carbonate cements median 13cpdb 12 4 is similar to that of the reservoired co2 13cpdb 14 5 and this is supportive of late stage cement formation with carbon sourced primarily from thermal maturation reactions the degree of co2 related reactions observed within the kapuni field appears dependent upon grain size lithofacies and stratigraphic position in the reservoir coarse grained high energy facies have undergone the most feldspar dissolution coupled with formation and local preservation of secondary porosity this is interpreted to be due to preferential migration of large volumes of co2 rich fluids through permeable beds thereby further enhancing reservoir quality by comparison much less feldspar reaction but locally significant authigenic mineral precipitation occurs within finer grained lower energy sandstone facies this is considered to be due to relatively low permeability prior to co2 circulation restricting the degree of fluid circulation and resulting in net mineral precipitation authigenic kaolin has precipitated close to the mineral source whilst ions required to precipitate calcite dolomite cements are likely to have migrated further resulting in a complex distribution of carbonate cements with pervasive cements observed at gas water contacts results from this study demonstrate how co2 related reactions are dependent on grain size and mineralogy we show that these reactions can affect vertical heterogeneity of a reservoir by increasing the degree of compartmentalisation through development of sweet spots due to mineral dissolution and tight beds due to mineral cementation

modelling petroleum formation from heterogeneous source rocks the influence of frequency factors on activation energy distribution and geological prediction abstract the application of basin modelling programs permits the prediction of organic matter transformation to oil and gas under variable geological conditions simplified kinetic models are commonly applied with a distribution of activation energies and a single average frequency factor here it will be shown that such simplified kinetic models are not sufficient to correctly predict organic matter transformation in heterogeneous kerogens under geological conditions in the present paper individual pairs of frequency factors and activation energies were calculated from the temperature shift of nine different levels of organic matter transformation ranging from 0 1 to 0 9 tr at different heating rates 0 1 0 7 and 5 0 k min this type of extended kinetic evaluation has been applied on samples from the green river shale the toarcian shale the duvernay formation the draupne formation a type ii s source rock petroleum asphaltenes and a tertiary coal from the mackenzie delta respectively for terrestrial and heterogeneous marine source rocks the frequency factors systematically increase with increasing level of transformation while such an increase was insignificant or absent when homogeneous source rocks were studied by applying geological heating rates it was possible to illustrate the significance of the extended calculation of individual frequency factors the predicted onset temperature of petroleum formation was displaced to 60 70 c in case of lignites coals and type ii s source rocks which was up to 30 40 c lower than predicted by the use of a conventional single frequency factor model to a lesser extend such a shift was also documented for some marine shales e g draupne formation and the duvernay formation the reason for this phenomenon is that an average single frequency factor suppresses the initial formation of petroleum at geological heating rates because high activation energies are needed to maintain the kinetic equation at low generation temperatures in contrast correct activation energies derive from individual frequency factors which keep the activation energies low at low levels of organic matter transformation and result in a more reliable description of the low energy bonds in the heterogeneous organic matter types

on the severe convective storm of 29 october 2013 in the balearic islands observational and numerical study on 29 october 2013 a severe squall line developed to the west of the balearic islands spain ahead of an advancing cold front and then crossed the archipelago we first provide an observational characterization of the event based on surface reports remote sensing products radiosoundings and synoptic information we also achieve by means of numerical experiments new insights into the kinematic and thermodynamic factors that governed the genesis and evolution of the linear convective system radar and satellite images confirm the fast movement and linear shape of the system with an indication of a possible transition into a bow echo structure during its later stages the synoptic setting at mid upper tropospheric levels was dominated by a cold trough extended over western europe associated with a jet stream located downstream convection evolved under the right entrance region of the jet and initiated under the crucial influence of a surface low that developed over the mediterranean sea ahead of the cold front the low not only cooperated with the upper level dynamical forcing to erode a capping inversion initially present over the balearics and moisten the atmospheric column above but also shaped and enhanced a convergence line along which the first convective cells grew and self aggregated this scenario is confirmed by numerical simulations of the case which also emphasize the important role of regional topography in the production of the aforementioned maritime convergence through the mesoscale modulation of the low level flow additional simulations show that i the destabilization of the low level air mass necessary for triggering and feeding an organized convective system on 29 october 2013 was attributable to prior evaporation from the mediterranean and ii sea surface temperatures appear to be critical for a successful fine grid numerical forecast of the mode degree of severity timing and track of the convective precipitation system

representing convective organization in prediction models by a hybrid strategy the mesoscale organization of precipitating convection is highly relevant to next generation global numerical weather prediction models which will have an intermediate horizontal resolution grid spacing about 10 km a primary issue is how to represent dynamical mechanisms that are conspicuously absent from contemporary convective parameterizations a hybrid parameterization of mesoscale convection is developed consisting of convective parameterization and explicit convectively driven circulations this kind of problem is addressed for warm season convection over the continental united states although it is argued to have more general application a hierarchical strategy is adopted cloud systemresolving model simulations represent the mesoscale dynamics of convective organization explicitly and intermediate resolution simulations involve the hybrid approach numerically simulated systems are physically interpreted by a mechanistic dynamical model of organized propagating convection this model is a formal basis for approximating mesoscale convective organization stratiform heating and mesoscale downdraft by a first baroclinic heating couplet the hybrid strategy is implemented using a predictor corrector strategy explicit dynamics is the predictor and the first baroclinic heating couplet the corrector the corrector strengthens the systematically weak mesoscale downdrafts that occur at intermediate resolution when introduced to the betts miller janjic convective parameterization this new hybrid approach represents the propagation and dynamical structure of organized precipitating systems therefore the predictor corrector hybrid approach is an elementary practical framework for representing organized convection in models of intermediate resolution

predicting the quantities of oil and gas generated fromaustralian permian coals bowen basin using pyrolyticmethods abstract the aim of the study was to establish kinetic parameters for gas and oil generation and totest the applicability of the kinetic models to petroleum generation through comparisons withnatural maturity coal sequences 433 c t max ro ro ro modelled ro calculated ro calculated

observable surface anomalies preceding simulated isolated convective initiation abstractidealized ensemble simulations of isolated convective initiation ci are analyzed to identify storm scale features in surface weather fields that precede initiation in a variety of background environments and the observations that would be needed to resolve these features precipitating storms are identified with an object based method and composites of surface anomalies are generated for the variables of interest surrounding times and locations of initiation correlation length scales and anomaly magnitudes throughout the ci process are examined in detail with the latter comparing favorably to anomaly estimates obtained from previous observational and modeling studies negative temperature anomalies due to cloud shadowing are found to be the most prominent storm scale feature prior to initiation significant spatial correlations are shown to extend from the surface throughout the boundary layer and even into the cloud bearing layer once deep convective clouds become established the findings are

quantitative estimation of compaction and velocity changes using 4d impedance and traveltime changes in some hydrocarbon reservoirs severe compaction of the reservoir rocks is observed this compaction is caused by production and it is often associated with changes in the overburden time lapse or 4d seismic data are used to monitor this compaction process since the compaction causes changes in both layer thickness and seismic velocities it is crucial to distinguish between the two effects two new seismic methods for monitoring compacting reservoirs are introduced one based on measured seismic prestack traveltime changes and the other based on poststack traveltime and amplitude changes in contrast to earlier methods these methods do not require additional empirical relationships such as for instance a velocity porosity relationship the uncertainties in estimates for compaction and velocity change are expressed in terms of errors in the traveltime and amplitude measurements these errors are directly related to the quality and repeatability of time lapse seismic data for a reservoir at 3000 m depth wit h9mo fcompaction and assuming a 4d timeshift error of 0 5 ms at near offset and 2 ms at far offset we find relative uncertainty in the compaction estimate of approximately 50 60 using traveltime information only

time lapse tomographic inversion using a gaussian parameterization of the velocity changes most seismic studies of changes in traveltimes are of a qualitative nature and a major challenge in four dimensions is to use the information contained in time shifts to quantify the nature of velocity changes in the subsurface layers we propose a 4d tomographic inversion method that uses time shifts from prestack seismic data to estimate parameters describing the 2d velocity field after changes have occurred prestack data allow for the usage of many offsets thus increasing the information input for the inversion the velocity changes are parameterized by a chosen number of gaussian functions in two dimensions and weighted least squares inversion is used to estimate the parameters describing these functions we have found that the parameters describing the position and shape of the gaussian velocity anomalies can be estimated with this method for simple synthetic cases for more complex cases with overlapping gaussian functions resolution of the parameters can be difficult and in these cases our recom

sea bed diffractions and their impact on 4d seismic data a sea bed reflection is used to estimate changes in water layer velocities between timelapse seismic surveys such corrections are crucial in order to obtain high quality 4d seismic data this might be a challenge in areas where rough sea bed topography creates sea bed diffractions that interfere with the sea bed reflection as in several of the northern fields in the norwegian sea these diffractions and diffracted multiples are difficult to attenuate during data processing and become a source of noise in time lapse data in this work we study how cross correlation analysis of time lapse seismic data at a sea bed reflection may be perturbed by the presence of diffractions the seabed topography from the norne field is used in 2d finite difference modelling to explain some of the observed variation in a water layer time shift in field data we find that a rough sea bed and the diffracted energy it induces cause residual noise on the 4d data the variation to the water layer time shift increases with sea bed complexity and is amplified by interaction with other sources of non repeatability like water column variations mis positioning and strength of the ice scours creating the diffracted energy time shift variations with mis positioning and velocity changes between the surveys seem to best explain the observed variation in the time shift for time lapse seismic field data from norne

properties of a lacustrine subbituminous k1 seam with special reference to the contact metamorphism soma turkey abstract the subbituminous k1 seam in the middle miocene soma formation of western turkey reaches a thickness of 24 m typical samples on an air dried basis have 9 5 14 2 moisture 4 3 13 8 ash and 0 57 2 54 total sulphur the coal rank parameters and non agglomerating behaviour show that the coals are of subbituminous a rank the k1 seam is huminite rich coal with a mean random ulminite reflectance rr between 0 46 and 0 49 fluorescence emission measurements show that the sporinite cutinite resinite and alginite present have typical fluorescence spectra between 460 and 700 nm the soma formation was intruded by an olivine basalt during the pliocene pleistocene which caused local contact metamorphism at the top of the k1 seam on the basis of proximate ultimate and petrographic analyses the intruded seam can be divided into normal coal transition zone and natural coke intervals each differing in their degree of metamorphism moisture volatile matter hydrogen and oxygen contents very rapidly decrease close to the contact point with the intrusion whilst calorific value carbon content and mean random reflectance value increase a diagram ofo c versus h c also shows a distinct increase in rank caused by the intrusion minor illite siderite and plagioclase feldspar are present in the natural coke samples butpyrrhotite is not observed mineralogical geochemical and reflectance studies indicate that the general temperature during formation of natural coke was probably relatively low

a proven method for acquiring highly repeatable towed streamer seismic data seismic reservoir monitoring has become an important tool in the management of many fields monitoring subtle changes in the seismic properties of a reservoir caused by production places strong demands on seismic repeatability a lack of repeatability limits how frequently reservoir changes can be monitored or the applicability of seismic monitoring at all in this paper we show that towing many streamers with narrow separation combined with cross line interpolation of data onto predefined sail lines can give highly repeatable marine seismic data results from two controlled zero time lag monitoring experiments in the north sea demonstrate high sensitivity to changing water level and variations in lateral positions after corrections by deterministic tidal time shifts and spatial interpolation of the irregularly sampled streamer data relative rms difference amplitude levels are as low as 12 for a deep structurally complex field and as low as 6 for a shallow structurally simple field reducing the deg

prediction of convective initiation and storm evolution on 12 june 2002 during ihop_2002 part i control simulation and sensitivity experiments abstract the 12 13 june 2002 convective initiation case from the international h2o project ihop 2002 field experiment over the central great plains of the united states is simulated numerically with the advanced regional prediction system arps at 3 km horizontal resolution the case involves a developing mesoscale cyclone a dryline extending from a low center southwestward with a cold front closely behind which intercepts the midsection of the dryline and an outflow boundary stretching eastward from the low center resulting from earlier mesoscale convection convective initiation occurred in the afternoon at several locations along and near the dryline or near the outflow boundary but was not captured by the most intensive deployment of observation instruments during the field experiment which focused instead on the dryline outflow boundary intersection point standard and special surface and upper air observations collected during the field experiment are assimilated into the arps at hourly inte

application of rank sr a maturity index based on chemical analyses of coals abstract the rank sr classification of suggate nz j geol geophys 43 2000 521 which uses data from standard coal industry chemical analyses is illustrated on interdependent diagrams with axes of atomic o c and h c and of calorific value and volatile matter the rank sr scale which is compensated for coal type is linear with depth under conditions of linear geothermal gradients so that the depth value for each unit increase in rank depends on the geothermal gradient at the time of maximum temperature normally that of maximum burial a general relation is established between rank sr and the temperature of attainment of rank temp c 10 rank sr 15 significant oil generation begins at rank sr 9 10 and expulsion at rank sr 11 5 12 5 a clear general relation exists between rank sr and vitrinite reflectance but rank sr is somewhat more accurate over the range from peat to the end of the oil window in the paleogene buller coalfield new zealand the use of rank sr aids interpretation of the geological history coals in the carboniferous nottinghamshire yorkshire coalfield in england probably contributed hydrocarbons including oil to the adjoining east midlands hydrocarbon fields vertical and lateral variations in rank sr in the coalfield and the rank sr values in coal measures at the base of the permian require a thick mesozoic tertiary cover in the oilfields of the mahakam delta indonesia and the taranaki basin new zealand rank sr depth gradients imply surface values that are close to zero where little or no cover has been eroded from above the wells and inferred temperatures that are reasonably close to present temperatures

maturity related variation in the bulk transformation kinetics of a suite of compositionally related new zealand coals abstract bulk hi transformation kinetics were determined by open system pyrolysis for a suite of compositionally related late cretaceous to paleocene coals from tara 1 well great south basin new zealand these coals span a maturity range encompassing the onset of significant oil generation and expulsion kinetic parameters were also obtained for one of the immature samples following artificial maturation by hydrous pyrolysis kinetic models were based on three modes of optimisation of kinetic parameters discrete e act distribution with single variable a value discrete e act distribution with fixed a 10 14 s 1 and gaussian e act distribution with single variable a value hi transformation rate vs temperature envelopes for the naturally matured coals exhibited an abrupt jump to higher temperature near rank s r 12 5 apparently coinciding with the onset of significant paraffinic oil expulsion for all optimisation modes the artificially matured sample does not predict this shift in transformation envelopes which suggests that certain of the reactions that occur under natural maturation do not occur during laboratory pyrolysis the structural rearrangements occurring up to the expulsion threshold some or all of which are responsible for the increase in hi up to rank s r 11 are not manifested in changes in hi transformation rate envelopes however the presence of adsorbed bitumen may mask the influence of structural rearrangements during optimisation of the kinetic data which could explain the behaviour of the transformation rate envelopes in the rank s r 11 0 12 5 range obtained from the discrete e act free a optimisation this behaviour involves a regression in transformation rate envelopes to lower temperatures as the amount of retained bitumen increases prior to expulsion the almost perfect nesting of transformation rate envelopes subsequent to oil expulsion suggests either that any further structural rearrangement does not produce a significant change in the a and e act distributions of hydrocarbon generating bonds or that the expulsion drastically reduces the degree of further rearrangements involving hydrocarbon generating moieties within the kerogen it follows that kinetic parameters for immature coals should not be considered ideal for modelling the whole phase of hydrocarbon generation nevertheless the kinetic parameters for the least mature tara coal rank s r 8 5 reproduced the normalised hi trend for the entire suite of coals with reasonable accuracy over the maturity range considered rank s r 8 5 15 0 only slightly underestimating conversion at the lower maturity levels and overestimating it slightly at the higher levels

simple kinetic models of petroleum formation part iii modelling an open system abstract the movement of petroleum from organic rich source beds to potential carrier beds is the net result of two processes expulsion the release of generated petroleum from kerogen within the source bed and primary migration flow of a petroleum phase through the inorganic void networks of the source bed and all other intervening fine grained rocks expulsion is by far the more important process within the source bed orgas a simple zero dimensional model of the source rock as an open system explicitly models expulsion concurrent with oil and gas generation and oi lgas cracking as a storage threshold problem oil and gas are retained adsorbed absorbed within kerogen until their concentrations exceed the respective sorptive capacity of the residual organic carbon 0 1 and 0 02 g g ck 1 the initial hydrogen index hl 0 controls the important balance between potential sorbate petroleum and sorbant residual carbon using simple geochemical measurements the initial organic carbon is divided into initial oil inert kerogen and oil and gas generative reactive kerogen components reactive kerogens are assigned to one of five global kinetic organofacies with pre determined kinetic parameter sets governing separately rates of oil and gas generation kinetic parameters governing the rates of oil cracking within the source rock are predicted from hl 0 the two most important determinants of source rock behaviour are organofacies and hl 0 at a reference constant heating rate of 2 c ma 1 the projected oil expulsion threshold for typical organofacies members increases in the order a de 100 110 120 135 c f typically expels no oil an order of magnitude increase decrease in heating rate increases decreases these thresholds by ca 15 c typical cumulative gas mass fractions in their ultimate expulsion products are a f 0 25 0 3 0 25 0 65 and 1 0 g g 1 a value of 200 mg hc g c 1 is an approximate minimum hl 0 prerequisite for oil expulsion irrespective of absolute petroleum potential p 0 as a family coals vary dramatically in their expulsion behaviour as their hl 0 ranges both above and velow this value primary migration is efficient for expulsive source rocks movement within the source bed is limited only at low p 0 a source rocks total genetic potential p 0 thickness becomes important during migration outside the source bed it potentially restricts the primary migration distance and the excess of petroleum available for secondary migration and entrapment we evaluate primary migration approximately using a small migration loss factor no more than about 10 saturation of porosity or 1 mg g 1 coupled with an understanding of fluid potential gradients which determine migration direction within the stratigraphic architecture ultimately kerogen degradation and oil to gas cracking in the source rock are the rate limiting processes in petroleum accumulation

sensitivity analysis and application of time lapse full waveform inversion synthetic testing and field data example from the north sea norway time lapse refraction can provide complementary seismic solutions for monitoring subtle subsurface changes that are challenging for conventional p wave reflection methods the utilization of refraction time lapse has lagged behind in the past partly due to the lack of robust techniques that allow extracting easy to interpret reservoir information however with the recent emergence of the full waveform inversion technique as a more standard tool we find it to be a promising platform for incorporating head waves and diving waves into the time lapse framework here we investigate the sensitivity of 2d acoustic time domain full waveform inversion for monitoring a shallow weak velocity change 30 m s or 1 6 the sensitivity tests are designed to address questions related to the feasibility and accuracy of full waveform inversion results for monitoring the field case of an underground gas blowout that occurred in the north sea the blowout caused the gas to migrate both vertically and horizontally into several shallow sand layers some of the shallow gas anomalies were not clearly detected by conventional 4d reflection methods i e time shifts and amplitude difference due to low 4d signal to noise ratio and weak velocity change on the other hand full waveform inversion sensitivity analysis showed that it is possible to detect the weak velocity change with the non optimal seismic input detectability was qualitative with variable degrees of accuracy depending on different inversion parameters we inverted the real 2d seismic data from the north sea with a greater emphasis on refracted and diving waves energy i e most of the reflected energy was removed for the shallow zone of interest after removing traces with offset less than 300 m the full waveform inversion results provided more superior detectability compared with the conventional 4d stacked reflection difference method for a weak shallow gas anomaly 320 m deep

chemostratigraphic evidence of higher plant evolution in the taranaki basin new zealand correlation between palynological and biomarker records of higher plant development during the cretaceous and paleogene in taranaki basin new zealand is good gymnosperms particularly podocarps were the chief members of coastal plain swamp flora during the late cretaceous and contributed significant quantities of diterpanes often dominated by isopimarane to organic rich sediments angiosperms increased in relative abundance through the paleocene and became the dominant higher plants in the eocene their contributions to coaly sediments are characterized by various triterpanes particularly 18 h oleanane and its c24 a ring degraded counterpart this change in dominance of higher plant groups can be followed by the use of an angiosperm gymnosperm index agi based on the relative concentrations of selected triterpanes and diterpanes in mz 191 and mz 123 mass chromatograms plant biomarker distributions do not provide as precise age indications as do pollen assemblages but they may be more representative of the vegetation growing in a particular area of a peat swamp

simulation of a serial upstream propagating mesoscale convective system event over southeastern south america using composite initial conditions abstract serial upstream propagating mesoscale convective system mcs events over southeastern south america are important contributors to the local hydrologic cycle as they can provide roughly half of the total monthly summer precipitation however the mechanisms of upstream propagation for these events have not been explored to remedy this situation a numerical simulation of the composite environmental conditions from 10 observed serial mcs events is conducted results indicate that the 3 day simulation from the composite yields a reasonable evolution of the large scale environment and produces a large region of organized convection in the warm sector over an extended period as seen in observations upstream propagation of the convective region is produced and is tied initially to the development and evolution of untrapped internal gravity waves however as convective downdrafts develop and begin to merge and form a surface cold pool in the simulation the cold pool and its interaction with the env