attribute mapping of variable thickness incised valley fill systems abstract whether we realize it or not seismic amplitude is the composite expression of multiple frequency components spectral components tuned to a given thickness often exhibit a high signal to noise ratio and thus provide the highest lateral resolution giving clear images of channels and other stratigraphic features that otherwise might be buried in broadband data for the same reason coherence and other edge sensitive attributes provide correspondingly sharper images when computed from spectral magnitude or voice components multiple stages of incisement are preserved in a survey acquired over the red fork formation of the anadarko basin oklahoma color blended images of 20 35 and 50 hz spectral components and corresponding coherence images are used to map the valley fill at different stages

comparison between active sensor and radiosonde cloud boundaries over the arm southern great plains site 1 in order to test the strengths and limitations of cloud boundary retrievals from radiosonde profiles 4 years of radar lidar and ceilometer data collected at the atmospheric radiation measurements southern great plains site from november 1996 through october 2000 are used to assess the retrievals of wang and rossow 1995 and chernykh and eskridge 1996 the lidar and ceilometer data yield lowest level cloud base heights that are on average within approximately 125 m of each other when both systems detect a cloud these quantities are used to assess the accuracy of coincident cloud base heights obtained from radar and the two radiosonde based methods applied to 200 m resolution profiles obtained at the same site the lidar ceilometer and radar cloud base heights agree by 0 156 0 423 km for 85 27 of the observations while the agreement between the lidar ceilometer and radiosonde derived heights is at best 0 044 0 559 km for 74 60 of all cases agreement between radar and radiosonde derived cloud boundaries is better for cloud base height than for cloud top height being at best 0 018 0 641 km for 70 91 of the cloud base heights and 0 348 0 729 km for 68 27 of the cloud top heights the disagreements between radar and radiosonde derived boundaries are mainly caused by broken cloud situations when it is difficult to verify that drifting radiosondes and fixed active sensors are observing the same clouds in the case of the radar the presence of clutter e g vegetal particles or insects can affect the measurements from the surface up to approximately 3 5 km preventing comparisons with radiosonde derived boundaries overall wang and rossow 1995 tend to classify moist layers that are not clouds as clouds and both radiosonde techniques report high cloud top heights that are higher than the corresponding heights from radar

3 d broad band estimates of reflector dip and amplitude estimates of seismic coherence of 3 d data sets have provided a radically new way of delineating detailed structural and stratigraphic features covariance matrices provide the natural formalism to extend the original three trace crosscorrelation algorithm to larger analysis windows containing multiple traces thus providing greater fidelity in low signal to noise environments by use of 3 d phase compensation using radon transforms we exploit advances made in the high resolution multiple signal classification music algorithms originally developed for the defense industry all three families of multitrace attributes coherence amplitude and phase are coupled through the underlying geology such that we obtain three families of complimentary images of geologic features that result in lateral changes in wave form the phase attributes of dip azimuth and curvature allow us to image areas that have undergone folding or draping that can not be seen on coherence or amplitude images the amplitude attribu

suppression of the acquisition footprint for seismic sequence attribute mapping seismic coherency has proven to be very effective in delineating geologic faults as well as considerably more subtle stratigraphic features including channels canyons slumps levees glacial gouges dewatering patterns and pinnacle reefs unfortunately seismic coherency estimates which quantitatively measure the similarity or dissimilarity of adjacent traces in 3 d are particularly sensitive to coherent noise that passes through the acquisition and processing flow they are also sensitive to dissimilarities in fold offset and azimuth distribution introduced through the 3 d acquisition and binning processes edge enhancement algorithms further exacerbate these linear artifacts we define the acquisition footprint to be any pattern of noise that is highly correlated to the geometric distribution of sources and receivers on the earth s surface while the strong acquisition footprints such as those caused by normal moveout nmo stretch on vintage single fold data have been largely ameliorated by mode

an improved cylindrical surface fitting related method for fault characterization abstracton the basis of the similarity of seismic waveforms and shapes of the reflectors the coherence and curvature attributes can be derived respectively to characterize faults coherence is effective for characterizing relatively large faults when the distortion of seismic waveforms at a fault is not obvious the curvature attribute may play a complementary role in detecting the fault according to geometric features of the faulted strata the rate of change of curvature has recently been developed to improve fault characterization through an application to the real seismic data from the western tazhong area of the tarim basin china it was demonstrated that curvature change rate has advantages in detecting subtle faults having quite small throws and heaves however when the dip angle of a faulted stratum is smaller than 45 the curvature change rate derived from its fitted surface has multiple extreme values associated with one fault plane which cause a low signal to noise ratio s n of a co

cloud vertical structure and its variations from a 20 yr global rawinsonde dataset abstract a global cloud vertical structure cvs climatic dataset is created by applying an analysis method to a 20 yr collection of twice daily rawinsonde humidity profiles to estimate the height of cloud layers the cvs dataset gives the vertical distribution of cloud layers for single and multilayered clouds as well as the top and base heights and layer thicknesses of each layer together with the original rawinsonde profiles of temperature humidity and winds the average values are cloud top height 4 0 km above mean sea level msl cloud base height 2 4 km msl cloud layer thickness 1 6 km and separation distance between consecutive layers 2 2 km multilayered clouds occur 42 of the time and are predominately two layered the lowest layer of multilayered cloud systems is usually located in the atmospheric boundary layer below 2 km height msl clouds over the ocean occur more frequently at lower levels and are more often formed in multiple layers than over land latitudinal variations o

case story time lapse seismic crosswell monitoring of co2 injected in an onshore sandstone aquifer summary we present a case study of time lapse seismic monitoring of carbon dioxide co2 injection by traveltime delay tomography unlike standard tomography based on the ray theory this tomographic method applies the 3 d finite frequency wavefield theory which in seismology is known as the banana doughnut theory to monitor 4 d changes in the subsurface during co2 injection crosswell seismic data were measured before the injection was initiated and after injection of 3200 6200 and 10 400 tons co2 into a porous reservoir sandstone at 1100 m depth the estimated tomographic velocity images compiled with the finite frequency wave theory show a clear time lapse velocity anomaly on the order of 18 per cent below the co2 injection well head which is in agreement with 4 d sonic logging

saturation path dependency of p wave velocity and attenuation in sandstone saturated with co2 and brine revealed by simultaneous measurements of waveforms and x ray computed tomography images abstractwe performed a laboratory experiment to measure compressional p wave velocity and its attenuation in low permeability striped sandstone at ultrasonic frequency during drainage co2 injection and imbibition brine injection x ray computed tomography ct images of the rock sample were simultaneously recorded during the injections on the basis of the ct images we calculated the co2 saturation inside a prolate spheroid shaped volume the first fresnel zone that enclosed the wave propagation path the relationship of p wave velocity and that of attenuation to the co2 fraction were then obtained both relationships showed nonuniqueness with remarkable hysteresis in a drainage imbibition cycle to explain the nonunique relationship of p wave velocity to the co2 fraction we investigated the continuous random patchy saturation model by using exponent type autocorrelation the nonunique relationship of velocity to the co2 fraction was explained by the model with a correlation length from an order

stratocumulus cloud top height estimates and their climatic implications a depth dependent boundary layer lapse rate was empirically deduced from 156 radiosondes released duringsixmonth longresearchcruisestothe southeastpacificsamplingavarietyofstratocumulusconditions thelapse ratedependenceonboundarylayerheightisweak decreasingfromabestfitof7 6to7 2k km 21 as theboundarylayerdeepensfrom800mto2km ship basedcloud baseheightsupto800mcorrespondwellto liftingcondensationlevels indicatingwell mixedconditions withcloud bases 800moften 200 600m higher than the lifting condensation levels the lapse rates were combined with moderate resolution imaging spectrometer 11 mm derived cloud top temperatures and satellite microwave derived sea surface temperatures to estimate stratocumulus cloud top heights the october mean cloud top height structure of the southeast pacific was then spatially and diurnally characterized coastal shoaling is apparent but so is a significant along coast cloud top height gradient with a pronounced elevation of the cloud top heights above thearicabightat 208s diurnalcloud topheightvariations inferredfromirregular4 times dailysampling can locally reach 250 m in amplitude and they can help to visualize offshore propagation of free tropospheric vertical motions a shallow boundary layer associated with the chilean coastal jet expands to its north and west in the afternoon cloud top heights above the arica bight region are depressed in the afternoon which may mean that increased subsidence from sensible heating of the andes dominates an afternoon increase in convergence upward motion at the exit of the chilean coastal jet in the southeast atlantic during october thestratocumuluscloud topheightsaretypicallylowerthanthoseinthesoutheastpacific acoastaljetregion can also be identified through its low cloud top heights coastal shoaling of the south atlantic stratocumulus region is mostly uniform with latitude in keeping with the more linear namibian angolan coastline the southeast atlantic shallow cloudy boundary layer extends farther offshore than in the southeast pacific particularly at 158s

detection and extraction of fault surfaces in 3d seismic data we propose an efficient method for detecting and extracting fault surfaces in 3d seismic volumes the seismic data are transformed into a volume of local fault extraction lfe estimates that represents the likelihood that a given point lies on a fault surface we partition the fault surfaces into relatively small linear portions which are identified by analyzing tilted and rotated subvolumes throughout the region of interest directional filtering and thresholding further enhance the seismic discontinuities that are attributable to fault surfaces subsequently the volume of lfe estimates is skeletonized and individual fault surfaces are extracted and labeled in the order of decreasing size the ultimate result obtained by the proposed procedure provides a visual and semantic representation of a set of well defined cleanly separated one pixel thick labeled fault surfaces that is readily usable for seismic interpretation

normal fault 3d geometry and displacement revisited insights from faults in the norwegian barents sea abstract utilizing seismic attributes we image fault 3d geometry for 21 normal faults of different sizes in the norwegian barents sea we revisit the published models of fault shape and growth using the new dataset based on the maximum accumulated length l m a x of faults we have classified them into two classes medium size 1 l m a x 1000 m and long faults l m a x 1000 m the common characteristics of these faults are i the medium size faults show mainly irregular shapes while long faults show a variety of shapes including irregular rectangular and elliptical ii in medium size faults maximum displacement is located close to the fault upper tip line iii no lateral segmentation was observed for most of the medium size faults while long faults contain several internal segments at each depth iv linkage with other faults is less common in medium size faults in comparison to the long ones v long faults with an elliptical shape have several displacement maxima located near the fault centre or close to the upper tip line vi long faults with irregular to rectangular shapes show the displacement maxima close to either upper or lower fault tip line our results show that for many of the analyzed faults the maximum displacement is located on the faults longest segment however this is not the case for some of the faults we found that power law fits well with the displacement length and displacement height relations of the faults furthermore the aspect ratio the ratio between fault maximum accumulated length and height is high for the studied faults and ranges between 1 5 and 16 the results can shed light on the understanding of fault geometry and growth for a variety of applications including geological and mechanical models incorporating faults

extreme curvature and extreme flexure analysis for fracture characterization from 3d seismic data new analytical algorithms and geologic implications abstractfracture characterization is fundamental to the reliable prediction of fractured reservoirs however it is difficult and expensive to obtain detailed fracture information required for reservoir prediction due to the lack of direct observational data in the subsurface here we develop seismic analysis methods to characterize fractured reservoirs based on reflection geometry related to bending and shearing of reservoir formations among various geometric attributes we focus on extreme curvature and extreme flexure that are considered effective at detecting fractures extreme curvature refers to the signed absolute maximum curvature at a specific azimuth where the curve shape is the tightest whereas extreme flexure refers to the signed absolute maximum gradient of curvature at a specific azimuth where the curve shape changes the most we implement new algorithms based on analytical equations to calculate extreme curvature and extreme flexure along with the corresponding azimuth from 3d seismic dat

the effect of 3 d prestack seismic migration on seismic coherence and amplitude variability we compare the effect of 3 d poststack versus 3 d prestack imaging on seismic coherence seismic amplitude and seismic amplitude variation we find that the improved resolution and amplitude preservation of the prestack imaging result in more sharply defined terminations and hence better delineation by coherence and amplitude gradients even though the macro velocity models used in both imaging approaches are laterally invariant v z

poststack velocity analysis by separation and imaging of seismic diffractions small geologic features manifest themselves in seismic data in the form of diffracted waves which are fundamentally different from seismic reflections using two field data examples and one synthetic example we demonstrate the possibility of separating seismic diffractions in the data and imaging them with optimally chosen migration velocities our criteria for separating reflection and diffraction events are the smoothness and continuity of local event slopes that correspond to reflection events for optimal focusing we develop the local varimax measure the objectives of this work are velocity analysis implemented in the poststack domain and high resolution imaging of small scale heterogeneities our examples demonstrate the effectiveness of the proposed method for high resolution imaging of such geologic features as faults channels and salt boundaries

3d seismic flexure analysis for subsurface fault detection and fracture characterization seismic flexure is a new geometric attribute with the potential of delineating subtle faults and fractures from three dimensional 3d seismic surveys especially those overlooked by the popular discontinuity and curvature attributes although the concept of flexure and its related algorithms have been published in the literature the attribute has not been sufficiently applied to subsurface fault detection and fracture characterization this paper provides a comprehensive study of the flexure attribute including its definition computation as well as geologic implications for evaluating the fundamental fracture properties that are essential to fracture characterization and network modeling in the subsurface through applications to the fractured reservoir at teapot dome wyoming usa specifically flexure measures the third order variation of the geometry of a seismic reflector and is dependent on the measuring direction in 3d space among all possible directions flexure is considered most useful when extracted perpendicular to the orientation of dominant deformation and flexure offers new insights into qualitative quantitative fracture characterization with its magnitude indicating the intensity of faulting and fracturing its azimuth defining the orientation of most likely fracture trends and its sign differentiating the sense of displacement of faults and fractures

diffraction imaging by uniform asymptotic theory and double exponential fitting seismic diffracted waves carry valuable information for identifying geological discontinuities unfortunately the diffraction energy is generally too weak and standard seismic processing is biased to imaging reflection in this paper we present a dynamic diffraction imaging method with the aim of enhancing diffraction and increasing the signal to noise ratio the correlation between diffraction amplitudes and their traveltimes generally exists in two forms with one form based on the kirchhoff integral formulation and the other on the uniform asymptotic theory however the former will encounter singularities at geometrical shadow boundaries and the latter requires the computation of a fresnel integral therefore neither of these methods is appropriate for practical applications noting the special form of the fresnel integral we propose a least squares fitting method based on double exponential functions to study the amplitude function of diffracted waves the simple form of the fitting function has no singularities and can accelerate the calculation of diffraction amplitude weakening coefficients by considering both the fitting weakening function and the polarity reversal property of the diffracted waves we modify the conventional kirchhoff imaging conditions and formulate a diffraction imaging formula the mechanism of the proposed diffraction imaging procedure is based on the edge diffractor instead of the idealized point diffractor the polarity reversal property can eliminate the background of strong reflection and enhance the diffraction by samephase summation moreover the fitting weakening function of diffraction amplitudes behaves like an inherent window to optimize the diffraction imaging aperture by its decaying trend synthetic and field data examples reveal that the proposed diffraction imaging method can meet the requirement of high resolution imaging with the edge diffraction fully reinforced and the strong reflection mostly eliminated

geometric characterization of igneous intrusions 3 d seismic insights from the campos basin se brazil abstract igneous intrusions are important for the exploration and appraisal phases of an oilfield due to their impact on petroleum systems their presence can be associated with the generation migration accumulation and entrapment of hydrocarbons in particular 1 sills with low permeability might form barriers to fluid flow and migration 2 sills may re use fracture networks providing insights on fluid migration and interaction s 3 sills may influence source rock maturation 4 sill induced uplifting of overburden and faulting may generate traps and 5 their geometric complexities enables the understanding of the interconnectedness of sill complexes which is the focus of this study therefore we provide a systematic characterization of sill geometries and their morphometric parameters we used three dimensional seismic data calibrated with well logs to interpret sills in the southern campos basin brazil throughout the late cretaceous until the paleogene sills intruded into the cretaceous to the eocene post salt sedimentary sequence including shallow platform carbonates transgressive marls and shales a morphometric analysis assisted by seismic attributes allowed the geometric characterization of sills namely 1 saucer shaped 2 slightly saucer shaped 3 climbing saucer shaped 4 transgressive and 5 rough layer parallel the documented sills comprise a wide range of sizes 0 43 14 35 km2 that increase with depth up to 3 18 km extend vertically from 0 06 to 0 23 km and vary from low 1 82 3 31 to high dip 6 05 15 74 the sill complex area extends over 67 35 km2 this study suggests that a thorough characterization of sill intrusions may have a substantial influence on the prediction of other igneous occurrences the mapped sills might have implications not just on the acoustically similar shallow platform albian carbonates of the macae group but may also provide insightful geometric constraints on the brazilian pre salt igneous intrusions

wavelet transform based seismic facies classification and modelling application to a geothermal target horizon in the ne german basin at the geothermal test site near gros sch onebeck ne german basin a new 3d seismic reflection survey was conducted to study geothermal target layers at around 4 km depth and 150 c we present a workflow for seismic facies classification and modelling which is applied to a prospective sandstone horizon within the rotliegend formation signal attributes are calculated along the horizon using the continuous morlet wavelet transform we use a short mother wavelet to allow for the temporal resolution of the relatively short reflection signals to be analysed time frequency domain data patterns form the input of a neural network clustering using self organizing maps neural model patterns are adopted during iterative learning to simulate the information inherent in the input data after training we determine a gradient function across the self organizing maps and apply an image processing technique called watershed segmentation the result is a pattern clustering based on similarities in wavelet transform characteristics three different types of wavelet transform patterns were found for the sandstone horizon we apply seismic waveform modelling to improve the understanding of the classification results the modelling tests indicate that thickness variations have a much stronger influence on the wavelet transform response of the sandstone horizon compared with reasonable variations of seismic attenuation in our interpretation the assumed thickness variations could be a result of variable paleo topography during deposition of predominantly fluvial sediments a distinct seismic facies distribution is interpreted as a system of thicker paleo channels deposited within a deepened landscape the results provide constraints for the ongoing development of the geothermal test site

the steepbank crosswell seismic project reservoir definition and evaluation of steamflood technology in alberta tar sands two crosswell seismic surveys were conducted at chevron canada s oil sand lease 49 steepbank located about 60 km northeast of fort mcmurray alberta this is the site of the hasdrive commercial pilot project in which steam is circulated through a horizontal well in order to preheat the tar sand prior to conventional steam injection the objective of the crosswell survey was to define the geology and to monitor the movement of the injected steam as part of the hasdrive evaluation the first survey was conducted 25 september 6 october 1991 just prior to steam injection the second was acquired 7 14 january 1992 after 72 days of continuous steam injection

poststack diffraction imaging using reverse time migration abstract we propose a method for imaging small scale diffraction objects in complex environments in which kirchhoff based approaches may fail the proposed method is based on a separation between the specular reflection and diffraction components of the total wavefield in the migrated surface angle domain reverse time migration was utilized to produce the common image gathers this approach provides stable and robust results in cases of complex velocity models the separation is based on the fact that in surface angle common image gathers reflection events are focused at positions that correspond to the apparent dip angle of the reflectors whereas diffracted events are distributed over a wide range of angles the high resolution radon based procedure is used to efficiently separate the reflection and diffraction wavefields in this study we consider poststack diffraction imaging the advantages of working in the poststack domain are its numerical efficiency and the reduced computational time the numerical results show that the proposed method is able to image diffraction objects in complex environments the application of the method to a real seismic dataset illustrates the capability of the approach to extract diffractions

3 d seismic attributes using a semblance based coherency algorithm seismic coherency is a measure of lateral changes in the seismic response caused by variation in structure stratigraphy lithology porosity and the presence of hydrocarbons unlike shaded relief maps that allow 3 d visualization of faults and channels from horizon picks seismic coherency operates on the seismic data itself and is therefore unencumbered by interpreter or automatic picker biases we present a more robust multitrace semblance based coherency algorithm that allows us to analyze data of lesser quality than our original three trace cross correlation based algorithm this second generation semblance based coherency algorithm provides improved vertical resolution over our original zero mean crosscorrelation algorithm resulting in reduced mixing of overlying or underlying stratigraphic features in general we analyze stratigraphic features using as narrow a temporal analysis window as possible typically determined by the highest usable frequency in the input seismic data in the limit one may confidently apply our new semblance based algorithm to a one sample thick seismic volume extracted along a conventionally picked stratigraphic horizon corresponding to a peak or trough whose amplitudes lie sufficiently above the ambient seismic noise in contrast near vertical structural features such as faults are better enhanced when using a longer temporal analysis window corresponding to the lowest usable frequency in the input data the calculation of reflector dip azimuth throughout the data volume allows us to generalize the calculation of conventional complex trace attributes including envelope phase frequency and bandwidth to the calculation of complex reflector attributes generated by slant stacking the input data along the reflector dip within the coherency analysis window these more robust complex reflector attribute cubes can be combined with coherency and dip azimuth cubes using conventional geostatistical clustering and segmentation algorithms to provide an integrated multiattribute analysis

evolution of seismic interpretation during the last three decades the ingredients of seismic interpretation include the right mix of geological and geophysical knowledge together with a liberal dose of imagination tempered with a considerable amount of patience seismic interpretation is a skill that one acquires with experience but is constantly reinvigorated with new ideas and tools provided by younger university graduates the prime ingredients for seismic interpretation are seismic reflection data coupled with a geologic depositional and tectonic model which together provide the framework for integrating borehole microseismic and production data resulting in a good reservoir model although commonly used in both engineering and environmental applications most seismic reflection surveys are acquired for oil and gas exploration in both land and offshore areas around the world hydrocarbon accumulations are found at varying depths of a few thousand meters below the earth s surface which are ultimately confirmed by drilling because the cost of drilling closely sp

analysis of fault scaling relations using fault seismic attributes we have studied three dimensional fault geometries through a geologically integrated analysis of fault seismic attribute volumes we used a series of coherence semblance and filtered coherence attribute volumes with parameters optimised for imaging faults in the studied seismic volumes fault geometric attributes such as along strike segment length and displacement were measured on fault seismic attributes the scaling relationships of fault geometric attributes were studied using statistical methods such as the bayesian information criterion the likelihood ratio test and the bootstrap method univariate distributions of fault segment length and maximum displacement show a truncated power law for most of the fault data the statistical results indicate a piecewise linear relation with two slopes between depth and fault segments lengths depth and mean displacement for these relations we observe consistent increases in fault segment lengths and mean displacements from the lower tip of the fault at depth toward a point of inflection at shallower depth at the vertical section from that point a reduction in fault segment lengths and mean displacements toward the upper tip of the fault at the shallower depth occurs fault segmentation along strike increases toward the lower and upper tips of the fault but the maximum number of segments are located near the lower tip of the fault in two of the studied faults the fault segment length is maximum where the number of segments along strike is least close to the middle of the fault in the vertical section

arctangent function based third derivative attribute for characterisation of faults using seismic attributes such as coherence and curvature to characterise faults not only can improve the efficiency of seismic interpretation but also can expand the capability to detect faults the coherence and curvature have been widely applied to characterising faults for years these two methods detect faults based on the similarity of seismic waveforms and shapes of the reflectors respectively and they are complementary to each other and both have advantages and disadvantages in fault characterisation a recent development in fault characterisation based on reflector shapes has been the use of the rate of change of curvature through an application to the seismic data from western tazhong of the tarim basin china it was demonstrated that the rate of change of curvature is more capable of detecting subtle faults having quite small throws and heaves however there often exist multiple extreme values indicating the same fault when applying the rate of change of curvature which significantly degrades the signal to noise ratio of the computation result for multiple extrema interfering with each other to resolve this problem we propose the use of a linear combination of arctangent and proportional functions as the directrix of a cylindrical surface to fit the fault model and calculate its third derivative which can then be used to characterise the fault through an application to the 3d seismic data from western tazhong of the tarim basin the results show that the proposed method not only retains the same capability to detect subtle faults having small throws as the curvature change rate but also greatly improves the signal to noise ratio of the calculated result

normal faults and gas migration in an active plate boundary southern taranaki basin offshore new zealand the function of normal faults in upsequence flow of gas has been examined using two dimensional and three dimensional seismic reflection data from the southern taranaki basin new zealand the spatial distributions of late stage normal faults gas chimneys thickness of the oligocene mudstone rich seal otaraoa formation and modeled hydrocarbon expulsion volumes are compared gas chimneys are most common above cretaceous source rocks modeled to have expelled hydrocarbons most 70 of the observed gas chimneys follow and or are rooted in late stage normal faults these faults are the primary seal bypass mechanism for hydrocarbons where they displace the seal or intersect faults that displace the seal and the seal is thick e g more than 340 m 1115 ft active vertical gas flow through the seal commenced after the onset of faulting 3 6 ma whereas subseal lateral flow started significantly earlier at approximately 15 ma and resulted in an early charge of structural highs gas flow up along faults in low permeability mudstones 1 md is channelized with steep chimneys commonly occurring close to fault tips and relay ramps in these cases gas flow may be focused by the presence of high densities of open fractures locally elevating upsequence bulk permeabilities to approximately 1 to 400 md

dynamics of geologic co2 storage and plume motion revealed by seismic coda waves quantifying the dynamics of sequestered co2 plumes is critical for safe long term storage providing guidance on plume extent and detecting stratigraphic seal failure however existing seismic monitoring methods based on wave reflection or transmission probe a limited rock volume and their sensitivity decreases as co2 saturation increases decreasing their utility in quantitative plume mass estimation here we show that seismic scattering coda waves acquired during continuous borehole monitoring are able to illuminate details of the co2 plume during a 74 h co2 injection experiment at the frio ii well dayton tx our study reveals a continuous velocity reduction during the dynamic injection of co2 a result that augments and dramatically improves upon prior analyses based on p wave arrival times we show that velocity reduction is nonlinearly correlated with the injected cumulative co2 mass and attribute this correlation to the fact that coda waves repeatedly sample the heterogeneous distribution of cumulative co2 in the reservoir zone lastly because our approach does not depend on p wave arrival times or require well constrained wave reflections it can be used with many source receiver geometries including those external to the reservoir which reduces the risk introduced by in reservoir monitoring wells our results provide an approach for quantitative co2 monitoring and plume evolution that increases safety and long term planning for co2 injection and storage

cloud layer thicknesses from a combination of surface and upper air observations abstract cloud layer thicknesses are derived from base and top altitudes by combining 14 years 1975 1988 of surface and upper air observations at 63 sites in the northern hemisphere rawinsonde observations are employed to determine the locations of cloud layer top and base by testing for dewpoint temperature depressions below some threshold value surface observations serve as quality cheeks on the rawinsonde determined cloud properties and provide cloud amount and cloud type information the dataset provides layer cloud amount cloud type high middle or low height classes cloud top heights base heights and layer thicknesses covering a range of latitudes from 0 to 80 n all data comes from land sites 34 are located in continental interiors 14 are near coasts and 15 are on islands the uncertainties in the derived cloud properties are discussed for clouds classified by low mid and high top altitudes there are strong latitudinal and seasonal variations in the layer thickness only for high

control of internal structure and fluid migration pathways within the barbados ridge decollement zone by strike slip faulting evidence from coherence and three dimensional seismic amplitude imaging the application of three dimensional seismic reflection and coherence imaging to the study of the decollement zone of the barbados ridge accretionary complex has provided new insights into the relationships among internal structure fluid flow and previously unrecognized strike slip faulting combined coherence and seismic amplitude imaging of the decollement zone reveal anomalous northeast trending lineaments parallel to and abutting zones of high amplitude negative polarity reflections analysis of these lineaments shows them to be penetrative structures dipping southeast with apparent reverse dip slip offset isopach mapping of the accretionary wedge indicates significant right lateral displacement across these structures these faults apparently channel fluid flow within the decollement zone and the prominent northeast trending conduits so formed are readily visible as high amplitude negative polarity reflections additionally north northeast trending zones of variable coherence and high positive amplitude are inferred barriers to up structure fluid migration pathways movement along strike slip structures probably alternates with displacement along the decollement zone northeast trending strike slip faults extend for 13 km crossing the length of the survey area and into the incoming oceanic plate active arc oblique strike slip faulting of the decollement zone beneath the barbados ridge accretionary wedge implies a stress regime in that 1 is fixed and 2 and 3 either transpose with time or are nearly equal this state of stress may be a common occurrence in forearc tectonism and may have led to the formation of many as yet unrecognized arc oblique strike slip faults at convergent margins

numerical simulation of first order backscattered p and s waves for time lapse seismic imaging in heterogeneous reservoirs summary first order elastic wave scattering theory validated in general features by deep borehole seismic coda wave observations is used to numerically simulate time lapse borehole seismic data aimed at monitoring oil water substitution in heterogeneous hydrocarbon reservoirs a first order perturbation solution of the vector wave equation leads to p p and s s backscattered displacement vector motion expressed as the angular summation of the second radial derivative of p and s wave velocity and density fluctuations over expanding spherical wave fronts of radii t 2 and t 2 p and s wave velocity and density spatial heterogeneity is modelled as long range correlated random fluctuations consistent with the power law scaling character of crustal rock physical properties measured by borehole logs the spectra of model scattering displacement seismograms for a power law scaling volumetric noise distribution duplicate the frequency enrichment observed in the spectra of broadband earthquake coda waves recorded in a deep well modelling of time lapse scattering in power law scaling permeability structures suggests that a stable borehole seismic source can locate oil water substitution in reservoir volumes tens of metres on a side at distances of up to a few hundred metres from an observation well using currently available borehole seismic technology time lapse tracking of oil water substitution and the monitoring of reservoir stress conditions can lead to spatially well constrained reservoir models despite large scale large amplitude correlated random heterogeneity

mass transport deposits and gas hydrate occurrences in the ulleung basin east sea part 1 mapping sedimentation patterns using seismic coherency abstract seismic coherency measures such as similarity and dip of maximum similarity were used to characterize mass transport deposits mtds in the ulleung basin east sea offshore korea using 2 d and 3 d seismic data several slope failure masses have been identified near drill site ubgh1 4 the mtds have a distinct seismic character and exhibit physical properties similar to gas hydrate bearing sediment elevated electrical resistivity and p wave velocity sediments recovered from within the mtds show a reworked nature with chaotic assemblage of mud clasts additionally the reflection at the base of mtds is polarity reversed relative to the seafloor similarly to the bottom simulating reflector commonly used to infer the presence of gas hydrates the mtds further show regional seismic blanking absence of internal reflectivity which is yet another signature often attributed to gas hydrate bearing sediments at the drill site ubgh1 4 no gas hydrate was recovered in sediment cores from inside a prominent mtd unit instead pore filling gas hydrate was recovered only within thin turbidite sand layers near the base of the gas hydrate stability zone with the analysis of seismic attributes the seismic character of the prominent mtd unit 3 was investigated the base of the mtd unit exhibits deep grooves interpreted as gliding tracks from either outrunner blocks or large clasts that were dragged along the paleo seafloor similar seismic features were identified on the seafloor although the length of the gliding tracks on the seafloor is much shorter a few hundred meters to 1 km compared to over 10 km long tracks at the base of the mtd the seismic coherency attributes allowed to estimate the volume of the failed sediment as well as the direction of the flow of sediment tracking the mtd and extrapolating its spatial extent from the 3 d seismic volume to adjacent 2 d seismic profiles a possible source region of this mass failure was defined 50 km upslope of site ubgh1 4

seismic attributes a historical perspective a seismic attribute is a quantitative measure of a seismic characteristic of interest analysis of attributes has been integral to reflection seismic interpretation since the 1930s when geophysicists started to pick traveltimes to coherent reflections on seismic field records there are now more than 50 distinct seismic attributes calculated from seismic data and applied to the interpretation of geologic structure stratigraphy and rock pore fluid properties the evolution of seismic attributes is closely linked to advances in computer technology as examples the advent of digital recording in the 1960s produced improved measurements of seismic amplitude and pointed out the correlation between hydrocarbon pore fluids and strong amplitudes bright spots the introduction of color printers in the early 1970s allowed color displays of reflection strength frequency phase and interval velocity to be overlain routinely on black and white seismic records interpretation workstations in the 1980s provided

analysis of normal fault populations in the kumano forearc basin nankai trough japan 1 multiple orientations and generations of faults from 3 d coherency mapping 1 analyses of normal faults in the kumano forearc basin of the nankai trough reveal multiple normal fault populations in a region generally thought to be under compression most faults have offsets of less than 20 m and dips of 60 70 and show no growth structures indicating that the faults were active for short periods of time the oldest generation of faults is older than 0 9 ma and strikes 50 60 the next oldest faults strike 160 170 are older than 0 44 ma and are related to local uplift along the western edge of the region the youngest faults cut the seafloor shallow faults near the se margin of the basin curve from 100 in the middle of the survey area to 145 at the se corner of the area the pattern of the two youngest fault populations is consistent with the regional stress pattern maximum horizontal stress subparallel to the trench orientations of older fault populations are caused by uplift of the underlying accretionary prism implying that the forearc basin region is not as stable as previously thought reconstruction of displacements on the youngest faults shows that the overall horizontal extension is less than 2 concentrated near the seaward edge of the basin the active normal faults distributed throughout the basin support the idea that the horizontal stress parallel to the plate convergence direction does not reach the critical stress to activate or form thrust faults and produce horizontal shortening within the shallow portion of the inner wedge

an introduction to this special section chronostratigraphy in 1977 we saw the publication of aapg memoir 26 seismic stratigraphy applications to hydrocarbon exploration in this book peter vail and his colleagues in a series of papers introduced the industry to the concepts of seismic sequences the construction of chronostratigraphic charts and how the seismic data could be used to estimate the global rise and fall of sea level in this work they also showed how the shape of the reflections and their lapping relationships could be used to predict depositional environment which could be used to predict sediment type and facies

semi automatic fault fracture interpretation based on seismic geometry analysis abstract fault and fracture interpretation is a fundamental but essential tool for subsurface structure mapping and modelling from 3d seismic data the existing methods for semi automatic automatic fault picking are primarily based on seismic discontinuity analysis that evaluates the lateral changes in seismic waveform and or amplitude which is limited by its low resolution on subtle faults and fractures without apparent vertical displacements in seismic images this study presents an innovative workflow for computer aided fault fracture interpretation based on seismic geometry analysis first the seismic curvature and flexure attributes are estimated for highlighting both the major faults and the subtle fractures in a seismic volume then fault probability is estimated from the curvature and flexure volumes for differentiation between the potential faults and non faulting features in the geometric attributes finally the seeded fault picking is implemented for interpreting the target faults and fractures guided by the knowledge of interpreters to avoid misinterpretation and artefacts in the presence of faulting complexities as well as coherent seismic noises applications to two 3d seismic volumes from the netherlands north sea and the offshore new zealand demonstrate the added values of the proposed method in imaging and picking the subtle faults and fractures that are often overlooked in the conventional seismic discontinuity analysis and the following fault interpretation procedures

visualization of active faults using geometric attributes of 3d gpr data an example from the alpine fault zone new zealand three dimensional ground penetrating radar gpr data are routinely acquired for diverse geologic hydrogeologic archeological and civil engineering purposes interpretations of these dataareinvariablybasedonsubjectiveanalysesofreflectionpatterns such analyses are heavily dependent on interpreter expertiseandexperience usingdataacquiredacrossgravelunitsoverlyingthealpinefaultzoneinnewzealand wedemonstratethe utilityofvariousgeometricattributesinreducingthesubjectivity of3dgprdataanalysis weuseacoherence basedtechniqueto compute the coherency azimuth and dip attributes and a graylevel co occurrence matrixglcmmethod to compute the texture basedenergy entropy homogeneity andcontrastattributes a selection of the gpr attribute volumes allows us to highlight key aspects of the fault zone and observe important features not apparent in the standard images this selection also provides information that improves our understanding of gravel deposition andtectonicstructuresatthestudysite anewdepositional structuralmodellargelybasedontheresultsofouranalysisofgprattributes includes four distinct gravel units deposited in three phases and a well defined fault trace this fault trace coincides with a zone of stratal disruption and shearing bound on one side by upward tilted to synclinally folded stratified gravels and on the other side by moderately dipping stratified alluvial fan gravelsthatcouldhavebeenaffectedbylateralfaultdrag whenused in tandem the coherence and texture based attribute volumes can significantly improve the efficiency and quality of 3d gpr interpretation especially for complex data collected across activefaultzones

application of a linear finite frequency theory to time lapse crosswell tomography in ultrasonic and numerical experiments time lapse seismic monitoring is the geophysical discipline whereby multiple data sets recorded at the same location but at different times are used to locate and quantify temporal changes in the elastic parameters of the subsurface we validate a time lapse monitoring method by crosswell tomography using two types of wavefield modeling experiments 1 a 3d real ultrasonic waveform experiment and 2 2d synthetic finite difference wavefield simulations for both wavefield experiments a time lapse structure simulating a fluid sweep in a reservoir layer is applied the time lapse tomographic monitoring approach is based on the standard ray theory and a finite frequency wavefield theory where the latter takes into account the finite frequency properties of recorded wavefields the inverted time lapse models compiled with either the ray theory or the finite frequency wavefield theory locate and correctly quantify the flooding zone in the simulated fluid sweep model both wavefield theories provide an adequate result because the flooding zone is comparable in size to the fresnel volume

the spatial distributions of faults and deep sea carbonate mounds in the porcupine basin offshore ireland localised populations of deep water carbonate mounds occur throughout the ne atlantic margin of ireland the uk and norway but the mechanisms responsible for their nucleation and growth are not well known based in part on the interpretation of seismic data from the porcupine basin offshore ireland it has been proposed previously that deeply rooted faults are present immediately beneath mounds and act as conduits for the vertical migration of mound feeding hydrocarbons several discrete carbonate mound populations or provinces are present in the porcupine basin above a number of distinct fault systems at different levels in the stratigraphy however detailed mapping of the distributions of both mounds and faults for two of these provinces in the northern part of the basin using 3d and 2d seismic data demonstrates that there is a poor spatial relationship between the two furthermore virtually all the reflector offsets directly beneath the mounds which have previously been interpreted as faults can be attributed to seismic artefacts such as velocity pull ups and diffraction cones therefore our findings strongly suggest that seismically mappable faults do not play a pivotal role as conductive fractures in the evolution of the mounds however mounds located towards the nw margin of the porcupine basin are underlain by a shallow intensely faulted slide package which provides one potential association between faults and mounds

diffraction imaging in depth high resolution imaging is of great value to an interpreter for instance to enable identification of small scale faults and to locate formation pinch out positions standard approaches to obtain high resolution information such as coherency analysis and structure oriented filters derive attributes from stacked migrated images since they are image driven these techniques are sensitive to artifacts due to an inadequate migration velocity in fact the attribute derivation is not based on the physics of wave propagation diffracted waves on the other hand have been recognized as physically reliable carriers of high or even super resolution structural information however high resolution information encoded in diffractions is generally lost during the conventional processing sequence indeed migration kernels in current migration algorithms are biased against diffractions we propose here methods for a diffraction based data oriented approach to image resolution we also demonstrate the different behaviour of diffractions compared to specular reflections and how this can be leveraged to assess characteristics of subsurface features in this way a rough surface such as a fault plane or unconformity may be distinguishable on a diffraction image and not on a traditional reflection image we outline some characteristic properties of diffractions and diffraction imaging and present two novel approaches to diffraction imaging in the depth domain the first technique is based on reflection focusing in the depth domain and subsequent filtering of reflections from prestack data the second technique modifies the migration kernel and consists of a reverse application of stationary phase migration to suppress contributions from specular reflections to the diffraction image both techniques are proposed as a complement to conventional full wave pre stack depth migration and both assume the existence of an accurate migration velocity

shaded relief seismic attribute shaded relief is employed throughout geophysics to display digital data as illuminated apparent topography such displays facilitate geologic understanding because apparent topography often suggests true geology first developed for elevation data batson et al 1975 shaded relief has long been used with gravity and magnetic data paterson and reeves 1985 kowalik and glenn 1987 it is a natural product of synthetic aperture radar and side scan sonar and it is routinely applied to interpreted seismic horizons hoetz and watters 1992

seismic attributes for monitoring of a shallow heated heavy oil reservoir a case study in production geophysics detecting the zones of production or constraining the in situ conditions within a reservoir are often of greater importance than obtaining highly resolved seismic structural images standard seismic data processing distorts the signal and limits the potential for extracting additional information especially for shallow targets an alternative shift stack procedure is applied in the processing of a shallow 12 fold 1 m common midpoint cmp spacing reflection profile acquired over a heated athabasca heavy oil sand reservoir the shift stack involves summing of cmp traces which have been flattened to an appropriate reference event simple modeling confirms that the prestack waveforms are better preserved by this process amplitude and frequency attributes are extracted from the reflection profile amplitudes of a continuous reservoir event vary by 600 over 35 m intervals along the profile bright spots correlate with heated regions apparent frequencies as measured by the instantaneous frequency and by short time window power spectral estimates of the subreservoir event are 20 30 hz lower in these same regions these diminished apparent frequencies most probably result from interference of the subreservoir reflection with events related to structural changes within the reservoir a complete interpretation of the results has not been attempted as knowledge of the in situ conditions is incomplete however changes in the seismic response at the well locations suggest that these attributes are useful in detection and mapping of heated zones the shiftstack procedure may also be useful in environmental and geotechnical applications

wavelet spectral probe for seismic structure interpretation and fracture characterization a workflow with case studies conventional amplitude images are routinely and often exclusively used to interpret subsurface structures however the amplitude images are composite seismic response to various geologic features at different scales the interference makes it difficult to investigate structural details that are not visually discernible in the amplitude images this paper presents a new algorithmic workflow to unravel seismic structural details by differentiating waveform characteristics at varying scales using a wavelet model as a spectral probe the algorithm performs a least squares linear regression between the model and data at each sample location to calculate the absolute correlation coefficient the resulting absolute correlation coefficient attribute which is indicative of instantaneous waveform similarity relative to the wavelet spectral probe provides a superior image with enhanced precision and resolution of the structural grain two case studies in the powder river and the appalachian basins demonstrate that the new algorithm helps investigate kinematic relationships among structural elements and differentiate between structural styles in particular the algorithm helps better define the along strike structural variation and segmentation associated with cross strike lineaments in the foreland basins comparative analysis indicates that the wavelet spectral probe algorithm helps shed new light on subtle but critical structural fabrics not easily discernible from conventional amplitude images revealing such information has important implications for better defining basin structural complexities and reservoir heterogeneity detecting faults and fractures at different scales and modeling fractured reservoirs

3d volumetric multispectral estimates of reflector curvature and rotation one of the most accepted geologic models is the relation between reflector curvature and the presence of open and closed fractures such fractures as well as other small discontinuities are relatively small and below the imaging rangeofconventionalseismicdata dependingonthetectonic regime structural geologists link open fractures to either gaussian curvature or to curvature in the dip or strike directions reflector curvature is fractal in nature with different tectonic and lithologic effects being illuminated at the 50 m and1000 m scales untilnow suchcurvatureestimateshave been limited to the analysis of picked horizons we have developed what we feel to be the first volumetric spectral estimates of reflector curvature we find that the most positive and negative curvatures are the most valuable in the conventional mapping of lineations including faults folds and flexures curvatureismathematicallyindependentof andinterpretatively complementary to the well established coherence geometric attribute we find the long spectral wavelengthcurvatureestimatestobeofparticularvalueinextracting subtle broad features in the seismic data such as folds flexures collapse features fault drags and under and overmigrated fault terminations we illustrate the value of these spectral curvature estimates and compare them to other attributes through application to two land data sets a salt domefromtheonshorelouisianagulfcoastandafractured karsteddatavolumefromfortworthbasinofnorthtexas

diffraction imaging of sub vertical fractures and karst with full resolution 3d ground penetrating radar abstract vertical fractures with openings of less than one centimetre and irregular karst cause abundant diffractions in ground penetrating radar gpr records gpr data acquired with half wavelength trace spacing are uninterpretable as they are dominated by spatially undersampled scattered energy to evaluate the potential of high density 3d gpr diffraction imaging a 200 mhz survey with less than a quarter wavelength grid spacing 0 05 m 0 1 m was acquired at a fractured and karstified limestone quarry near the village of cassis in southern france after 3d migration processing diffraction apices line up in sub vertical fracture planes and cluster in locations of karstic dissolution features the majority of karst is developed at intersections of two or more fractures and is limited in depth by a stratigraphic boundary such high resolution 3d gpr imaging offers an unprecedented internal view of a complex fractured carbonate reservoir model analogue as seismic and gpr wave kinematics are similar improvements in the imaging of steep fractures and irregular voids at the resolution limit can also be expected from high density seismic diffraction imaging

edge preserving frequency offset denoising of seismic data fil gomez julian luis consejo nacional de investigaciones cientificas y tecnicas centro cientifico tecnologico conicet la plata argentina universidad nacional de la plata facultad de ciencias astronomicas y geofisicas argentina

autotracking of faults on 3d seismic data manual fault mapping in 3d seismic interpretation is labor intensive and time consuming complex fault geometries and the distortion of the seismic signal close to faults complicate full automation of the fault mapping process we present a semiautomatic fault tracking method for 3d seismic data that consists of fault highlighting followed by model based fault tracking fault highlighting uses log gabor filters for emphasizing oriented amplitude discontinuities at faults in the presence of noise subsequent fault tracking fits an active contour to the highlighted fault voxels the active contour searches for a connected smooth curve which fits the data and disambiguates misleading or missing information the fault tracker requires the interpreter to place the active contour close to a fault on one initial seismic inline 2d pick the active contour deforms to the closest amplitude dis continuity highlighted this tracking result is then projected forward to the next inline providing an initial fault pick on this section that is again optimized by the active contour tracking results on a series of successive seismic sections finally constitute a 3d fault surface user interaction is solely required for an approximate fault pick on the first inline and in cases where the fault line is lost due to insufficient signal use of the autotracker prototype provides a fast solution for the mapping of complete 3d fault surfaces of constant dip and for the automated tracking of fault portions within distinct dip domains if fault surfaces are curved i e listric the method was applied to a series of high quality reflectivity sections extracted from a 3d seismic volume from shallow offshore nigeria with the tracking results generated within seconds comparing well with manually interpreted fault surfaces

surface based observations of mesoscale cumulus stratocumulus interaction during astex abstract data obtained from the island of santa maria in the azores during the atlantic stratocumulus transition experiment astex are used to describe cloud and boundary layer structure for a 24 h period on 15 june 1992 over the east central atlantic 37 n 25 10 w the evolution of the mesoscale cloud structure during a 24 h period in the vertical column above the surface site was characterized using a 94 ghz radar a laser ceilometer 3 h radiosonde ascents and surface micrometeorological instrumentation mesoscale circulations and drizzle were found to be key elements of the boundary layer clouds observed in this region during the late night and predawn hours of the study period a single layer of stratocumulus that averaged 200 m in thickness topped a well mixed marine boundary layer mesoscale cellular convection mcc which had ascending regions with horizontal dimensions of 7 km was observed during this period at sunrise decoupling was imposed on this mcc and extreme mesoscale variatio

do peatland microforms move through time examining the developmental history of a patterned peatland using ground penetrating radar using ground penetrating radar gpr to map subsurface patterns in peat physical properties we investigated the developmental history of meso scale surface patterning of microforms within a raised bog common offset gpr measurements were obtained along a 45 m transect at frequencies ranging from 100 to 900 mhz we found that low frequency central frequency 240 mhz showed a striking pattern of subsurface reflections that dip consistently in a northerly direction the angle of these dipping reflectors is calculated using a semblance algorithm and was shown to average 3 9 degrees between a depth of 1 0 and 2 5 m these dipping reflectors may indicate downslope migration of surface microforms during the development of the peatland based on the estimated angle and the rate of peat accumulation the average rate of downslope propagation of these surface microforms is calculated at 9 8 mm per year further survey work is required to establish whether the downslope migration is common across the peatland

3 d seismic discontinuity for faults and stratigraphic features the coherence cube seismic data are usually acquired and processed for imaging reflections this paper describes a method of processing seismic data for imaging discontinuities e g faults and stratigraphic features one application of this nontraditional process is a 3 d volume or cube of coherence coefficients within which faults are revealed as numerically separated surfaces figure 1 compares a traditional 3 d reflection amplitude time slice with the results of the new method to our knowledge this is the first published method of revealing fault surfaces within a 3 d volume for which no fault reflections have been recorded

a workflow to skeletonize faults and stratigraphic features abstractimproving the accuracy and completeness of subtle discontinuities in noisy seismic data is useful for mapping faults fractures unconformities and stratigraphic edges we have developed a workflow to improve the quality of coherence attributes first we apply principal component structure oriented filtering to reject random noise and sharpen the lateral edges of seismic amplitude data next we compute eigenstructure coherence which highlights the stratigraphic and structural discontinuities we apply a laplacian of a gaussian filter to the coherence attribute that sharpens the steeply dipping faults attenuates the stratigraphic features parallel to the seismic reflectors and skeletonizes the unconformity features subparallel to the reflectors finally we skeletonize the filtered coherence attribute along with the fault plane the filtered and skeletonized seismic coherence attribute highlights the geologic discontinuities more clearly and precisely these discontinuous features can be colo

seismic analysis of polygonal fault systems in the great south basin new zealand abstract polygonal fault systems pfs consisting of networks of layer bound normal faults are analyzed for eocene strata in the great south basin new zealand an advanced fault enhancement and skeletonization method is applied to delineate faults using 3d seismic data from the great south basin the process sharpens structural and stratigraphic discontinuities and smears the incoherent noise on coherence to obtain a skeletonized fault probability volume which can be directly used to extract and map fault geometries the characteristics of the polygonal faults in cross section planform and 3d space were studied the faults dip approximately 50 with displacements on a single fault ranging from tens of meters to a hundred meters the fault planform patterns are polygonal but also related to the regional horizontal stress anisotropy caused by slope changes of the basal unit the patterns vary from linear for high slopes rectangular for moderate slopes and polygonal for low slopes two preferred orientations may reflect the superposition of deep cretaceous trends on the polygonal system in the eocene strata a local concentric pattern with outward dipping normal faults is related to passive or active draping above a circular plutonic volcanic structure the genetic mechanism of the polygonal fault systems is interpreted to be related to volume loss and shear failure related to opal a ct transition within the sediments

seismic evidence for repeated vertical fluid flow through polygonally faulted strata in the canterbury basin new zealand abstract seismic imaging techniques are widely used to determine fluid migration pathways in the subsurface understanding the timing and distribution of focused fluid migration pathways is important for assessing reservoir seal quality and hydrocarbon exploration risk as well as seafloor biogeochemical processes in the case of fluid venting from the seafloor the frontier canterbury basin southeast of new zealand is well studied but questions remain regarding the dynamic movement of fluids through the basin using 3d seismic data combined with high resolution boomer seismic data we characterise focused fluid migration and sediment remobilisation events in the canterbury basin we show how polygonal fault formation and nucleation is affected in the vicinity of vertically ascending fluids and sediments a cylindrical region devoid of polygonal faulting around the feeder system of a buried sediment volcano points to the possible existence of an axisymmetrical stress field induced by upward migrating fluids and sediments sediment remobilisation and intrusions of permeable stingers i e sand injectites could enable dewatering of their host strata and thereby prevent polygonal faults from nucleating amplitude variations with angle ava and a detailed analysis of two tiers of polygonal faults reveal three phases of fluid migration and sediment remobilisation and intrusion through and into low permeability sediments our integrated conceptual model provides insights into vertical fluid migration mechanisms and the implications for polygonal fault formation

rock property and seismic attribute analysis of a chert reservoir in the devonian thirty one formation west texas u s a in west texas fractured chert reservoirs of devonian age haveproducedmorethan700millionbarrelsofoil aboutthe same amount of mobile petroleum remains in place these reservoirsarecharacterizedbymicroporosity theyareheterogeneous and compartmented which results in recovery of less than 30 of the oil in place in this case study the objective was to use cores petrophysical logs rock physics and seismic attributes to characterize porosity and field scale fractures therelationsamongporosity velocity andimpedancewereexploredandalsoreactionsamongproduction impedance and lineaments observed in 3d attribute volumes laboratory core data show that gassmann s fluid substitution equation works well for microporous tripolitic chert also laboratry measurements show excellent linear correlation between p wave impedance and porosity volumetric calculations of reflector curvature and seismic inversion of acoustic impedance were combined to infer distribution of lithofaciesandfracturesandtopredictporosity statisticalrelationswereestablishedbetweenp wavevelocityandporosity measured from cores between p wave impedance and producing zones and between initial production rates and seismic fracture lineaments the strong quantitative correlation between thick bedded chert lithofacies and seismic impedance was used to map the reservoir a qualitative inverse relation between the first 12 months of production and curvaturelineamentswasdocumented

gravity data as a tool for detecting faults in depth enhancement of subtle almada s basement faults brazil we demonstrate the potential of gravity data to detect and to locate in depth subtle normal faults in the basement relief of a sedimentary basin this demonstration is accomplished by inverting the gravity data with the constraint that the estimated basement relief presents local abrupt faults and is smooth elsewhere we inverted the gravity data from the onshore almada basin in northeastern brazil and we mapped several normal faults whose locations and plane geometries were already known from seismic imaging the inversion methoddelineatedwellboththediscontinuitieswithsmallor largeslipsandasequenceofstepfaults usingsyntheticdata weperformedasystematicsearchofnormalfaultslipsversus fault displacement depths to map the fault detectable region inthisspace thismappinghelpstoassesstheabilityofgravityinversiontodetectnormalfaults mappingshowsthatnormalfaultswithsmall0 5 km mediumabout1 km and large about 2 km vertical slips can be detected if the maximummidpointdepthsofthefaultplanesaresmallerthan1 8 3 8 and6 8 km respectively

finite frequency effects in global surface wave tomography summary we compare traditional ray theoretical surface wave tomography with finite frequency tomography using 3 d born sensitivity kernels for long period fundamental mode dispersion measurements the 3 d kernels preserve sidelobes beyond the first fresnel zone and fully account for the directional dependence of surface wave scattering and the effects of timedomain tapering and seismic source radiation tomographic inversions of love and rayleigh phase delay measurements and synthetic checkerboard tests show that 1 small scale s wave velocity anomalies are better resolved using finite frequency sensitivity kernels especially in the lowermost upper mantle 2 the resulting upper mantle heterogeneities are generally stronger in amplitude than those recovered using ray theory and 3 finite frequency tomographic models fit long period dispersion data better than ray theoretical models of comparable roughness we also examine the reliability of 2 d phase velocity sensitivity kernels in global surface wave tomography and show that phase velocity kernels based upon a forwardscattering approximation or previously adopted geometrical simplifications do not reliably account for finite frequency wave propagation effects 3 d sensitivity kernels with full consideration of directional dependent seismic scattering are the preferred method of inverting long period dispersion data finally we derive 2 d boundary sensitivity kernels for lateral variations in crustal thickness and show that finite frequency crustal effects are not negligible in long period surface wave dispersion studies especially for paths along continent ocean boundaries unfortunately we also show that in global studies linear perturbation theory is not sufficiently accurate to make reliable crustal corrections due to the large difference in thickness between oceanic and continental crust

high resolution satellite measurements of the atmospheric boundary layer response to sst variations along the agulhas return current abstract the marine atmospheric boundary layer mabl response to sea surface temperature sst perturbations with wavelengths shorter than 30 longitude by 10 latitude along the agulhas return current arc is described from the first year of sst and cloud liquid water clw measurements from the advanced microwave scanning radiometer amsr on the earth observing system eos aqua satellite and surface wind stress measurements from the quikscat scatterometer amsr measurements of sst at a resolution of 58 km considerably improves upon a previous analysis that used the reynolds sst analyses which underestimate the short scale sst gradient magnitude over the arc region by more than a factor of 5 the amsr sst data thus provide the first quantitatively accurate depiction of the sst induced mabl response along the arc warm cold sst perturbations produce positive negative wind stress magnitude perturbations leading to short scale perturbations in the wind stress curl and divergence fields that are li

efficient volumetric extraction of most positive negative curvature and flexure for fracture characterization from 3d seismic data most positive negative curvature and flexure are among the most useful seismic attributes for detecting faults and fractures in the subsurface based on the geometry of seismic reflections when applied to fracture characterization and modelling of a fractured reservoir their magnitude and azimuth help quantify both the intensity and orientation of fracturing respectively however previous efforts focus on estimating only the magnitude of both attributes whereas their associated azimuth is ignored in three dimensional 3d seismic interpretation this study presents an efficient algorithm for simultaneously evaluating both the magnitude and azimuth of most positive negative curvature and flexure from 3d seismic data the approach implemented in this study is analytically more accurate and computationally more efficient compared with the existing approach the added value of extracting most positive negative curvature and flexure is demonstrated through the application to a fractured reservoir at teapot dome wyoming first the newly extracted attributes make computer aided fault fracture decomposition possible this allows interpreters to focus on one particular component for fracture characterization at a time so that a composite fractured reservoir could be partitioned into different components for detailed analysis second curvature flexure azimuth allows interpreters to plot fracture histogram and or rose diagram in an automatic and quantitative manner compared with the conventional plotting rose diagram based on manual measurements automatic plotting is more efficient and offers unbiased insights into fracture systems by illuminating the most likely orientations of natural fractures in fractured reservoirs

geomechanical restoration as a tool for fractured reservoir characterization application to the permian basin west texas we present a three dimensional 3 d geomechanical restoration method as a reservoir characterization tool in the permian basin west texas the oates sw field produces gas from the lower devonian thirtyone formation within structural traps the thirtyone is a brittle chert with characteristics of a fractured reservoir field development has experienced variable production trends for decades to assess the impact of deformation on reservoir properties we employ 3 d geomechanical restorations to model strain patterns associated with fault displacement and fold growth we correlate these model strains with independent measures of natural rock strain to assess the viability of the restoration results a semblance volume generated from 3 d seismic reflection data illuminates secondary faults and fracture zones that are not incorporated in the geomechanical restorations our analysis yields strong correlations between low semblance and elevated strain throughout the thirtyone reservoir these correlations indicate that restoration strains may be used to describe the distribution of secondary faults and fractures that are not represented in our models providing predictive capabilities for defining fractured reservoir properties we integrate strain and semblance with production data to evaluate these correlations at the borehole scale in the study area we describe how tectonic strain likely enhanced permeability directly impacting observed production trends our characterization of the thirtyone reservoir demonstrates the ability to accurately predict strain distributions with geomechanical restorations where structure has been a significant factor in the development of reservoir permeability we suggest that these methods show promise as a reservoir characterization tool for conventional and unconventional development operations

improved estimates of seismic curvature and flexure based on 3d surface rotation in the presence of structure dip abstractfracture characterization is critical to reliable prediction of fractured reservoirs fractures formed by folding and or shearing of reservoir formations can be detected using seismic curvature and flexure analysis previous curvature and flexure analysis methods often have limitations in accuracy and efficiency in the presence of structural dip we have developed new algorithms for volumetric curvature and flexure analysis based on 3d surface rotation using the local reflector dip to improve the accuracy and efficiency for curvature and flexure analysis in structurally complex settings among the various measures of curvature and flexure in 3d space we have focused on signed maximum curvature and flexure that are considered to be most effective for predicting intensity and orientation of faults and fractures in fractured reservoirs the application of the algorithms to a 3d seismic survey from teapot dome wyoming demonstrated that the new methods help resolve subtle structural details that ar

cross well seismic waveform tomography for monitoring co2 injection a case study from the ketzin site germany seismic full waveform inversion waveform tomography is a method to reconstruct the underground velocity field in high resolution using seismic data the method was first introduced during the 1980 s and became computationally feasible during the late 1990 s when the method was implemented in the frequency domain this work presents three case studies and one synthetic benchmark of full waveform inversion applications two of the case studies are focused on time lapse cross well and 2d reflection seismic data sets acquired at the ketzin co2 geological storage site these studies are parts of the co2sink and co2man projects the results show that waveform tomography is more effective than traveltime tomography for the co2 injection monitoring at the ketzin site for the cross well geometry for the surface data sets we find it is difficult to recover the true value of the velocity anomaly due to the injection using the waveform inversion method but it is possible to qualitatively locate the distribution of the injected co2 the results agree well with expectations based upon conventional 2d cdp processing methods and more extensive 3d cdp processing methods in the area a further investigation was done to study the feasibility and efficiency of seismic full waveform inversion for time lapse monitoring of onshore co2 geological storage sites using a reflection seismic geometry with synthetic data sets the results show that waveform inversion may be a good complement to standard cdp processing when monitoring co2 injection the choice of method and strategy for waveform inversion is quite dependent on the goals of the time lapse monitoring of the co2 injection the last case study is an application of the full waveform inversion method to two crooked profiles at the forsmark site in eastern central sweden the main goal of this study was to help determine if the observed reflections are mainly due to fluid filled fracture zones or mafic sills one main difficulty here is that the profiles have a crooked line geometry which corresponds to 3d seismic geometry but a 2d based inversion method is being used this is partly handled by a 3d to 2d coordinate projection method from traveltime inversion the results show that these reflections are primarily due to zones of lower velocity consistent with them being generated at water filled fracture zones

robust estimates of 3d reflector dip and azimuth much of seismic stratigraphy is based on the morphology of seismic textures the identification of reflector terminations and subtle changes in dip and azimuth allows us to infer coherent progradational and transgressive packages as well as more chaotic slumps fans and braided stream complexes infill of karsted terrains gas seeps and of course faults and angular unconformities a major difficulty in estimating reflector dip and azimuth arises at discrete lateral and vertical discontinuities across which reflector dip and azimuth change the smearing across these boundaries produced by traditional dip and azimuth estimations is avoided by using temporally and spatially shifted multiple windows that contain each analysis point this more robust estimation of dip and azimuth leads to increased resolution of well established algorithms such as coherence coherent amplitude gradients and structurally oriented filtering more promising still is the analysis of high resolution dip and azimuth through vol

salt diapirs without well defined boundaries a feasibility study of semi automatic detection prestack depth imaging of seismic data in complex areas such as salt structures requires extensive velocity model updating in many cases salt boundaries can be difficult to identify due to lack of seismic reflectivity traditional amplitude based segmentation methods do not properly tackle this problem resulting in extensive manual editing this paper presents a selection of seismic attributes that can reveal texture differences between the salt diapirs and the surrounding geology as opposed to amplitude sensitive attributes that are used in case of well defined boundaries the approach consists of first extracting selected texture attributes then using these attributes to train a classifier to estimate the probability that each pixel in the data set belongs to one of the following classes near horizontal layering highly dipping areas and the inside of the salt that appears more like a low amplitude area with small variations in texture to find the border between the inside of the salt and the highly dipping surroundings the posterior probability of the class salt is input to a graph cut algorithm that produces a smooth continuous border an in line seismic section and a timeslice from a 3d north sea data set were employed to test the proposed approach comparisons between the automatically segmented salt contours and the corresponding contours as provided by an experienced interpreter showed a high degree of similarity

variability of cloud vertical structure during astex observed from a combination of rawinsonde radar ceilometer and satellite the macroscale cloud vertical structure cvs including cloud base and top heights and layer thickness and characteristics of multilayered clouds is studied at porto santo island during the atlantic stratocumulus transition experiment astex by using rawinsonde radar ceilometer and satellite data the comparisons of cvs parameters obtained from four different approaches show that 1 by using the method developed by wang and rossow rawinsonde observations raob s can sample all low clouds and determine their boundaries accurately but oversample low clouds by about 10 mistaking clear moist layers for clouds 2 cloud base heights less than 200 m in the radar data are ambiguous but can be replaced by the values measured by ceilometer and 3 the practical limit on the accuracy of marine boundary layer cloud top heights retrieved from satellites appears to be about 150 300 m mainly due to errors in specifying the atmospheric temperature and humidity in the inversion layer above the cloud the vertical distribution of clouds at porto santo during astex is dominated by low clouds below 3 km a cloud free layer between 3 and 4 km and 20 high clouds with a peak occurrence around 7 8 km low clouds have mean base and top heights of 1 0 km and 1 4 km respectively and occur as single layers 90 of the time for double layered low clouds the tops of the uppermost layers and the bases of the lowermost layers have similar distributions as those of single layered clouds the temporal variations of low clouds during astex are apparently dominated by advecting mesoscale 20 200 km horizontal variations coherent time variations are predominately synoptic timescale 4 5 6 8 days and diurnal variability on the diurnal timescale all cloud properties show maxima in the early morning around 0530 lst decreasing to minima in the late afternoon diurnal variations appear to be altered when high clouds are present above low clouds the general characteristics of cvs in three astex and the first isccp regional experiment fire87 regions derived from a 20 yr rawinsonde dataset are also presented the results suggest that cvs characteristics obtained from data collected at porto santo during astex june 1992 are not representative of other marine stratiform cloud regions

characterization of the shallow structures of active fault zones using 3 d ground penetrating radar data 1 where they can be correlated with geological exposures and trenches 3 d ground penetrating radar gpr data can contribute critical subsurface information to paleoseismic investigations because active faults are typically characterized by complicated near surface structures that vary with the styles of faulting and the types of rock that are ruptured gpr data can be difficult to interpret we have acquired 3 d gpr data sets across three active fault zones within new zealand that have different deformation styles the strike slip wellington fault zone reverse faults of the ostler fault zone and normal faults of the maleme fault zone to improve our interpretation of the processed gpr volumes we employed two suites of geometric attributes the first suite was computed using a coherence based algorithm it provided estimates of the coherency azimuth and dip of reflections the second suite quantified the volumetric textures of reflections which allowed different reflection facies to be defined objectively we have demonstrated how some attributes were more successful at visualizing certain structural or depositional characteristics than others for example the coherency attribute was an excellent tool for highlighting normal faults within volcanic deposits of the maleme fault zone whereas the texture based attributes were most useful for discriminating between the gravel and metasediment units juxtaposed by the wellington fault zone our gpr data sets and associated attribute volumes showed details of near surface fault geometry that were not obvious from surface mapping and they revealed evidence of off fault deformation gravitational collapse and topple structures

an analysis of cloud cover in multiscale modeling framework global climate model simulations using 4 and 1 km horizontal grids 1 over the past few years a new type of global climate model gcm has emerged in which a two dimensional or small three dimensional cloud resolving model is embedded into each grid cell of a gcm this approach is frequently called the multiscale modeling framework mmf but is also known as a cloud resolving convection parameterization or a superparameterization in this article we compare joint histograms of cloud top height and optical depth from the mmf with those being produced by the international satellite cloud climatology project isccp and from the multiangle imaging spectroradiometer misr while the form of the isccp and misr data sets is conceptually similar the satellite sensors and the algorithms differ with the result that the joint histograms can differ quite significantly even when viewing exactly the same clouds the analysis takes advantages of the strengths of each data set as well as the differences in these data which for example allow one to characterize the amount of some multilayer clouds mmf simulation runs with three different resolutions are analyzed one simulation is run using a 4 km horizontal grid with 26 vertical levels on a stretched grid a second simulation is run with a 1 km horizontal grid and the same 26 vertical levels and a third simulation is run with a 1 km horizontal grid and 52 vertical levels the analysis shows that the mmf reproduces the broad pattern of tropical convergence zones subtropical belts and midlatitude storm tracks as observed by isccp and misr however the model has several significant shortcomings perhaps most seriously it significantly underpredicts the amount of low level cloud in most regions the simulation with a 1 km horizontal grid and 52 vertical layers is found to improve modestly several aspect of the mmf low level cloud cover the model output is obtained using isccp and misr instrument simulators and the role of horizontal resolution in the instrument simulators is examined