seismic fluid detection a review abstract since the advent of seismic imaging techniques the dream of geophysicists has been to identify the fluid effect and be able to accurately map hydrocarbon from the brine within a target reservoir the usage of bright spots strong reflection amplitudes as an indicator of hydrocarbon was the earliest recognition of the direct role played by the pore fluids in seismic signatures further development of new techniques had a strong correlation with the increase in computing power and advances in seismic acquisition and processing techniques in this review we touch upon the relevant theory developed more than 100 years ago and then review the methods developed over five decades leading to the quantitative interpretation of seismic data for fluid detection we also carried out a case study to compare selected fluid identification methods applied to a complex reservoir within an oil and gas field in the barents sea the impedance based methods cpei curved pseudo elastic impedance and lmr lambda mu rho inversion provided better results compared to other techniques highlighting the critical influence anomalous lithologies have on such screening attributes

nature and origin of seismic reflection fabric ruby east humboldt metamorphic core complex nevada seismic reflection profiling across exposed upper and middle crustal rocks of the ruby east humboldt metamorphic core complex delineates important characteristics of the crustal structure developed during tertiary extensional deformation the goals of this study were to trace a tertiary extensional shear zone from mylonitic surface outcrops into a seismic section and to characterize the deeper crustal fabric associated with the polyphase deformational history of the complex reflections in the shallow surface correlate with a plastic to brittle shear zone that formed during the tectonic unroofing of the middle crustal rocks constructive interference from strong planar layering in the mylonitic shear zone is considered chiefly responsible for generating the reflections east and southwest dipping reflectors in the seismic section appear to correlate with exposed opposing dipping mylonitic foliation domains the opposing dips of the mylonitic layering may reflect warping of the normal sense shear zone during tectonic exhumation coupled with an overall anastomosing character deeper in the section a heterogeneous reflection character correlates with increases in velocity shown from wide angle measurements in this region and is interpreted as penetrative fabric originating from extensional flow facilitated by broad scale pure shear and localized simple shear lower crustal rocks apparently achieved granulite facies metamorphism during extension a maximum of 6 8 km of mafic material could have been added to the crust during cenozoic extension the moho reflection has such a high amplitude that it may be caused by partially molten rocks interleaved with peridotite reflections from the moho show no significant upwarping of the base of the crust beneath the core complex this suggests that the lower crustal configuration is at least as young as the period of extensional activity that lasted from approximately 40 to 20 ma which was responsible for the exhumation of the metamorphic core complex

pre existing intra basement shear zones influence growth and geometry of non colinear normal faults western utsira high heimdal terrace north sea abstract pre existing intra basement shear zones can induce mechanical and rheological heterogeneities that may influence rifting and the overall geometry of rift related normal faults however the extent to which physical and kinematic interaction between pre existing shear zones and younger rift faults control the growth of normal faults is less well understood using 3d reflection seismic data from the northern north sea and quantitative fault analysis we constrain the 3d relationship between pre existing basement shear zones and the geometry evolution and synrift depositional architecture of subsequent rift related normal faults we identify ne sw and n s striking rift faults that define a coeval middle jurassic early cretaceous non colinear fault network ne sw striking faults are parallel to underlying intra basement shear zone the faults either tip out above or physically merge with the underlying shear zone for faults that merges with the basement shear zone a change from tabular to wedge shaped geometry of the hangingwall synrift strata records a transition from non rotational to rotational extension faulting which we attribute to the time of rift fault s linkage with the shear zone following downward propagation of its lower tip n s striking faults are oblique to and offset rather than link with intra basement shear zones these observations highlight the selective influence pre existing intra basement shear zones may or may not have on evolving rift related normal faults

interpretation of incised valleys using new 3 d seismic techniques a case history using spectral decomposition and coherency new 3 d seismic interpretation techniques such as spectral decomposition and coherency have been shown to enhance interpretation of stratigraphic features in tertiary poorly lithified rocks but their use has not been as well documented on older more consolidated sediments coherency images seismic discontinuities by calculating localized seismic trace similarity spectral decomposition uses the discrete fourier transform to image time thickness variability in the latter the amplitude spectrum computed from a short time window covering the geologic zone of interest is tuned by the rock properties within the analysis window when applied to 3 d seismic and presented in map form these spectral responses image lateral variability within the zone of interest

volume based curvature computations illuminate fracture orientations early to mid paleozoic central basin platform west texas volumetric curvature analysis is a simple but computationally intensive procedure that provides insight into fracture orientation and regional stresses until recently curvature analysis has been limited to computation along horizon surfaces that may be affected by unintentional bias and picking errors introduced during the interpretation process volumetric curvature is best estimated in a two step process in the first step we use a moving analysis subvolume to estimate volumetric reflector dip and azimuth for the best fit tangent plane for each sample in the full volume in the second step we calculate curvature from adjacent measures of dip and azimuth we use larger curvature analysis windows to estimate longer wavelength curvatures such a technique allows us to output full 3d volumes of curvature values for one or more scales of analysis we apply these techniques to a data set from the central basin platform of west texas and find lineaments not observable with other seismic attributes these lineaments indicate that in the lower paleozoic interval a left lateral shear couple oriented due east west controls the local stress regime such a model predicts that extension faulting and fractures will be oriented northeast southwest the example demonstrates the potential of this new technology to determine stress regimes and predict azimuths of open fractures

erratum kinematics of mylonites in the priest river metamorphic core complex northern idaho and northeastern washington spokane dome located in the southern priest river complex is defined by a zone of gently dipping mylonitic rocks about 4 km thick in contrast to more typical core complexes the mylonitic deformation gradually fades both above and below the zone without an intervening nearly concordant zone of chloritic brecciation thin younger mylonitic rocks within the synformal newport fault zone overlie spokane dome to the north and a younger low angle fault cuts the mylonites in the purcell trench to the east the mylonitic rocks within spokane dome contain c and s surfaces and other mesoscopic structures indicating in all cases top to the east movement in contrast the mylonitic rocks within the newport fault zone formed during normal movement on both the eastern and western limbs of the fault the mylonites of spokane dome probably formed during large scale mesozoic top to the east intracontinental shear whereas the newport fault records eocene extension and crustal megaboudinage

an integrated approach to define new plays in mature oil basins the example from the middle magdalena valley basin colombia an integrated approach to detect new areas of potential interest associated with stratigraphic traps in mature basins is presented the study was carried out in the middle magdalena valley basin colombia the workflow integrates outcrop and subsurface interpretations of facies activity of faults and distribution of depocenters and paleocurrents and makes use of them to construct a three dimensional exploration scale geocellular facies model of the basin the outcrop and well log sedimentological analysis distinguished facies associations of alluvial fan overbank floodplain and channel fill the last one constituting the reservoir rock the seismic analysis showed that tectonic activity was coeval with the deposition of the productive units in the basin and that the activity ended earlier before the middle miocene along the western margin than along the eastern margin paleogeographic reconstructions depict transverse and longitudinal fluvial systems alluvial fans adjacent to the active basin margins and floodplain facies dominating the structural highs and the southwestern depositional limit these reconstructions provided statistical data lateral variograms to construct the model the exploration scale facies model depicts the complete structure of the basin in three dimensions and the gross distribution of the reservoir and seal rocks the predictive capability of the model was evaluated positively and the model was employed to detect zones of high channel fill facies probability that form bodies that are isolated or that terminate upward in pinchouts or are truncated by a fault our approach can prove helpful in improving general exploration workflows in similar settings

scoring completion effectiveness in unconventional horizontal wells using 3d seismic attributes abstract using a multihorizontal well completion pilot in an unconventional oil field in the lower 48 contiguous united states midcontinent a workflow is proposed to evaluate the effectiveness of horizontal well completions through 3d surface seismic attributes and microseismic data three dimensional surface seismic is often continuous over unconventional fields and provides a measurement in areas where no other data are available in addition microseismic is the only geophysical data that allows us to see the apparent hydraulic fracture zone around a wellbore using these two geophysical tools integrated with engineering and geologic data such as image logs total proppant number of stages estimates of fracture length and height permeability chemical tracers and production rates a geophysical completion scorecard is developed to evaluate a multiwell horizontal pilot and apply it to additional wells drilled outside the pilot in an effort to predict their completion effectiveness a postdril

ductile and brittle deformations in the northern snake range nevada abstract the northern snake range east central nevada is one of the metamorphic core complexes of the sevier hinterland within the range a major decollement separates an upper plate composed of brittlely deformed paleozoic sedimentary rocks mostly carbonates from a lower plate composed of metamorphic upper precambrian lower cambrian rocks intruded by gneissic granites a study of the geometry and kinematics of structures and fabrics at outcrop scale and in thin sections indicates that the northern snake range decollement has been a zone of intense non coaxial e vergent shear and transport in a n115 e direction outstanding asymmetric boudinage within the marble sheet capping the lower plate testifies for late ductile shear strains of at least 20 the interface between brittlely and ductilely deformed rocks seems too sharp to represent a regional rheological transition but might result from two distinct phases of deformation ductile deformation in and below the decollement could have occurred before brittle deformation in the upper plate brittle faulting in the upper plate related to basin and range extension reactivated the upper surface of the ductile shear zone high topographic relief on the normal faults bounding the range triggered the slide of olistolites from the upper plate into the adjacent oligo miocene basins

3 d seismic horizon based approaches to fracture swarm sweet spot definition in tight gas reservoirs in this article we will discuss some horizon attribute based methods that we have been exploring to help identify productive fracture swarms in tight gas reservoirs

complex seismic trace attributes interpretation of seismic reflection records is a blend of quantitative science and visual art an interpreter uses the rules of wave propagation realistic limits on impedances of rocks and accepted principles of stratigraphic deposition and structural deformation to arrive at a geologic understanding of a seismic section this application of science however seldom produces a unique answer and the obligation to consider alternative interpretations provides plenty of latitude for creative imagining

a provisional structural thickness map of the otago schist new zealand metamorphic zones terranes and lithologic associations provide a subdivision of the lithologically monotonous otago schist on a 10 to 50 kilometer scale in this study form line maps of schist foliation have been used to construct a provisional structural thickness map of the otago schist that allows a more detailed 1 5 km scale subdivision of the entire schist the map shows the macroscopic thickness of schist measured orthogonal to dominant foliation relative to the datum of the caples rakaia terrane boundary the structural thickness map provides a new spatial reference frame for the otago schist that depicts the differing levels of exhumation of penetratively deformed metamorphic rocks the structural thickness parameter shows a good correlation with metamorphic grade white mica grain size and k ar and ar ar ages thus justifying the simplifying assumptions behind the map s construction the map reveals several hitherto little highlighted features including along and across strike correlations interference patterns between mesozoic and cenozoic macroscopic folds net displacement across known and inferred major faults and relative structural position of mesothermal gold deposits

structural study of intra oceanic thrusting in the klamath mountains northern california implications on accretion geometry the kinematics of the basal intra oceanic thrust of the trinity preston peak seiad and josephine ultramafic bodies of the klamath mountains are deduced from microstructural and mineral preferred orientation studies when corrected of possible postthrusting rotations these kinematics are thought to reflect the paleoconvergence geometry of the pacific plate relative to the north american continent at the time of intra oceanic thrusting we first detail the kinematics of thrusting for each studied massif these results are then integrated in a plate tectonics reconstruction and a model of continuous ne sw convergence for mesozoic times is proposed

kinematics of pre miocene ductile deformation in the santa catalina core complex and adjacent regions this paper describes structures within mylonites and metamorphic rocks from the santa catalina and tortolita suizo metamorphic core complexes southeastern arizona united states in these areas mylonitic rocks constitute an easterly low dipping slab more than 4 km thick mapping of principal strain directions and analysis of shear sense have been carried out through the whole pile of mylonites it is shown that although the stretching lineation appears to have a uniform mean sw ne trend three successive shearing events are involved the first shearing event is toward the west and is accompanied in part by the emplacement of the leatherwood quartz diorite dated at 64 ma the second shearing event is toward the ne and is accompanied by the emplacement of the wilderness granitic suite dated at 49 ma the third shearing event is localized and directed toward the sw the top to west shearing and top to ne shearing are possibly related to laramide thrusting the last ductile shearing is related to post eocene extension

reply to comment on low frequency microtremor anomalies at an oil and gas field in voitsdorf austria by marc andre lambert stefan m schmalholz erik h saenger and brian steiner geophysical prospecting 57 393 411

the low frequency gas shadow on seismic sections about six years ago greg partyka and his colleagues at amoco research showed how an old technique the fourier transform could be used effectively for seismic interpretation and visualization this idea has come to be known as spectral decomposition in recent years many spectral decomposition techniques have been developed and utilized for stratigraphic analysis and direct hydrocarbon detection with the refined spectral decomposition techniques now available the low frequency shadow beneath gas reservoirs is another old idea that has renewed importance and interest in the exploration community almost a decade ago dan ebrom studied a variety of possible mechanisms for the low frequency shadow and why it might be associated with hydrocarbons he presented his analysis at the 1996 seg summer research workshop

the pre cretaceous deep seated tectonics of the abukuma massif and its place in the structural framework of japan abstract the structures and microstructures of the takanuki and hitachi areas in the abukuma massif northeast japan are described in the takanuki area the basic gosaisho series thrusts the pelitic takanuki ones in a hp metamorphic context the nappe structure is afterwards refolded by a migmatitic dome the samegawa dome in a ht metamorphic context microtectonic analysis shows that the nappe was transported from south to north along the stretching lineation geometric features suggest that the samegawa dome was emplaced by diapirism the role of the thrust surface as an instable interface promoting the doming is emphasized the hitachi metamorphic rocks composed of basic schist limestone and sandstone shist thrust the pelitic rocks of the western hitachi gneisses as for the takanuki area the thrusting occurred in ductile synmetamorphic conditions with a north or northeastward displacement owing to lithologic petrologic structural similitudes the nappe of the hitachi metamorphic rocks and that of the gosaisho series are unified into a unique nappe with a northward motion the emplacement occurred between late permian and late cretaceous likely in late jurassic the allochthonous units of the abukuma massif are correlated with the green schist nappe described in southwest japan since they are surrounded by the same zones namely the tanba zone and the kurosegawa kitakami one moreover both in southwest and northeast japan the emplacement of the green schist nappes is due to a shear deformation inducing rotational structures along the stretching lineation indicating the same sense of transport that is eastward in southwest japan and northward in northeast japan owing to the late bending of the japanese islands the late jurassic nappe structure is obliquely overprinted by a ht metamorphism ryoke in southwest japan abukuma in northeast japan and afterwards cut by late faults as the median tectonic line or the tanakura fault giving rise to the present complexity

a tutorial on complex seismic trace analysis complex seismic trace analysis treats a seismic trace as the product of two independent and separable functions instantaneous amplitude and cosine of the instantaneous phase at any given time instantaneous amplitude is the maximum value the seismic trace can attain under a constant phase rotation and instantaneous phase is the phase angle required to rotate the trace to the maximum defining these two attributes in this way permits complex seismic trace analysis to be founded without reference to the complex trace all other complex seismic trace attributes derive from amplitude and phase through differentiation averaging combination or transformation the chief derived attributes are frequency relative amplitude change wavelength dip and azimuth at any point on a seismic trace the instantaneous attributes describe a sinusoid that locally matches the trace most instantaneous attributes are improved through filtering or weighted averaging the phase wavenumber vector provides a convenient basis for quantifying 3d seismic properties such as reflection parallelism

potential risks when using seismic attributes as predictors of reservoir properties the advance of our ability to generate seismic attributes and the growing emphasis on production geophysics has led to the widespread use of seismic attributes as predictors of reservoir properties in many cases we can show using seismic modeling or rock physics a physically justifiable relationship between a seismic attribute and the reservoir property of interest when this is true we are able to greatly reduce the uncertainty of interwell predictions of reservoir properties

seismic sedimentologic study of facies and reservoir in middle triassic karamay formation of the mahu sag junggar basin china abstract the top sandstone s1 of the middle triassic karamay formation t2k is one of the major pay zones in the mahu field junggar basin northwestern china both spatial distribution and internal architecture of the reservoirs are important for resource evaluation and petroleum production in the field seismic sedimentology an integrated study of seismic geomorphology and seismic lithology was applied to well and three dimensional 3 d seismic data to analyze distribution of sedimentary facies and reservoirs lithologies in the study area consist of conglomerate sandstone and mudstone acoustic impedance ai of mudstone 6 9 106 kg s m2 is lower than the other two lithologies which have similar ai values 9 14 106 kg s m2 therefore seismic amplitude can distinguish mudstone from conglomerate and sandstone but fails to differentiate conglomerate from sandstone seismic geomorphology was employed to qualitatively predict distribution of sandstone and conglomerate respectively using frequency decomposition seismic attribute extraction and red green blue rgb color blending techniques in the seismic lithologic study principal component analysis pca was utilized to transfer multiple seismic attributes into principal components selected principal components were then fit with cumulative reservoir thickness interpreted from porosity log data resulting in quantitative estimation of interwell thin 10 m or thinner reservoir distribution meandering fluvial facies were recognized for the first time in the previously interpreted fan delta facies zone meandering channels formed when the lake level rose in relatively humid climate during a time with few tectonic activities the previously formed fan delta was substituted by a later formed meandering channel which flowed into the southwestern lake from the north sediment distribution was controlled by accumulation space or paleogeomorphology restored by cast method sediment is thick in paleolow terrains and thin in paleohigh areas locality of reservoir rock is basically coincident with sandstone distribution thick reservoir rocks with high porosity greater than 10 are located mainly in areas with moderately thick sandstones formed in point bar subfacies of fluvial systems and in lower fan subfacies of the fan delta system higher petroleum production in individual wells drilled in the fluvial system indicates superior physical properties there as a result locating point bar subfacies is key to improving hydrocarbon exploration and development

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

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

seismic attribute technology for reservoir forecasting and monitoring during the 1970s and 1980s the seismic attributes most used in petroleum exploration were amplitude based instantaneous attributes however in the 1990s seismic attribute technology has dramatically advanced in several directions techniques now range from single trace instantaneous event attribute computations to more complex multitrace windowed seismic event attribute extractions to the generation of seismic attribute volumes applications run from simple amplitude anomaly detection to monitoring fluid front movement over time

alpine model for the internal metamorphic zones of the north american cordillera the tectonic significance of the internal metamorphic zones of the north american cordillera remains elusive we propose a general interpretation in which the tectonic features pervasive unidirectional transverse lineation recumbent folding eastward thrusting of the shuswap complex canada are related to a large scale intracontinental alpine type eastward shearing this shearing results from the jurassic collision between the allochthonous stikine block and the north american craton after a westward triassic subduction we extend this model to the united states cordillera despite some differences due to the late occurrence of a major extension

evaluating the structure characteristics of epikarst at a typical peak cluster depression in guizhou plateau area using ground penetrating radar attributes abstract epikarst defined as the skin of karst environment is widely developed in southwest china largely as a result of the subtropical monsoon climate typical sw china karst accommodates a dual hydrogeological structure with surface and subsurface hydrological systems the epikarst ecosystem of karst environments plays a key role in biogeochemical cycling and energy and material storage and transport due to low rates of soil formation derived from carbonate rock weathering the soil layer is shallow and scattered presenting interlocked features within carbonate rock research on epikarst structure is primarily based on section field survey with semi quantitative characterization often lacking a fully quantitative description of soil rock structural characteristics we utilized ground penetrating radar gpr attributes to interpret the structure of epikarst at a peak cluster depression in the guizhou karst plateau two typical types of epikarst slope profiles and one peak cluster depression in maguan town puding county were selected for study we used mala gpr equipment with 500 mhz and 50 mhz antennas to acquire data gpr data was processed conventionally and then average energy attributes average amplitude attributes and coherence attributes were extracted to interpret the structure of the two epikarst profiles and the soil depth of the depression the results show that i energy and coherence attributes can highlight the soil rock structure of the epikarst profiles with relative ease ii compared to the original returned image the energy attributes visualise the soil and rock medium more effectively and iii the coherence attributes can identify the reflection interface between complete bedrock and bedrock containing fissure and grikes epikarst in addition using the 50 mhz antenna we were able to determine the soil depth in depression with coherence attributes indicating a depth of 3 6 m very close to the real depth 3 58 m measured by our auger verification work gpr attributes provide evidence that the epikarst has developed a large number of fissures filled with soil or other materials but that the bedrock under the epikarst has few fractures gpr attributes are therefore helpful for increasing our confidence of studying the structure of slope epikarst structure and depression soil depth

two stage evolution of the cenozoic kunbei fault system and its control of deposition in the sw qaidam basin china the structural relationship between the qaidam basin and qimen tagh eastern kunlun range holds important implications for evaluating the formation mechanism of the tibetan plateau various models have been proposed to reveal the structural relationship although controversies remain to address these issues we analysed the seismic and lithologic data of the kunbei fault system i e the kunbei arlar and hongliuquan faults which lies to the north of the qimen tagh eastern kunlun range within the sw qaidam basin based on the regional geological framework and our kinematic analyses we propose that the cenozoic tectonic evolution of the kunbei fault system can be divided into two stages from the early eocene to the middle miocene the system was characterized by left lateral strike slip faults and weak south dipping thrust faults based on the flower structure in the seismic section which is an apparent strike slip deformation that was identified in the 1510 ms time slice and the root mean square amplitude attribute slice this strike slip motion was generated by the uplift of the tibetan plateau caused by the onset of the indian eurasian collision since the middle miocene the kunbei fault system has undergone intense south dipping thrusting and a nearly 2 2 km uplift has been observed in the hanging wall in the arlar fault the south dipping thrusting is the far field effect of the full collision that occurred between the indian eurasian plates the lake area in the sw qaidam basin has been shrinking since the middle miocene and presents widespread delta and fluvial deposits which are consistent with the proposed tectonic evolution

lidar based digital outcrops for sedimentological analysis workflows and techniques f rarity x m t van lanen d hodgetts r l gawthorpe p wilson i fabuel perez j redfern

metamorphism of the spokane dome mylonitic zone priest river complex constraints on the tectonic evolution of northeastern washington and northern idaho metamorphic rocks in the core of the southern priest river complex record two distinct metamorphic events the earliest metamorphism occurred above 5 kb near the amphibolite granulite boundary and accompanied the formation of a steep crystalloblastic foliation the second less pronounced metamorphism was at lower pressure 3 5 kb in the middle amphibolite facies and accompanied mylonitization within a 4 km thick zone retrograde reactions during the second event include the formation of andalusite muscovite secondary green biotite and the breakdown of garnet biotite garnet geothermometry yielded widely variable and unrealistically high temperatures plagioclase garnet geobarometry is partially reset by the retrograde event and therefore provides minimum pressures the p t path is not known precisely but may include two episodes of prograde metamorphism perhaps related to continued accretion of terranes to the west the first metamorphism probably accompanied the jurassic accretion of quesnell

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

vertical circulation revealed by diurnal heating of the upper ocean in late winter part i observations abstract during a 5 day period in late winter 1984 temperature were measured at 9 depths beneath a drifting spar buoy to a relative accuracy of 2 mk the depths ranged from 15 to 145 m in a mixing layer that was nearly homogeneous to over 250 m a diurnal temperature signal was observed whose maximum amplitude decreased from 40 mk at 15 m to 20 mk at 145 m surface heat fluxes in particular the diurnal variation in solar radiation are too small to account for the diurnal variations in mixed layer heat content instrumental errors are ruled out the lagrangian experiment minimized horizontal advection which had in any case been quantified using a towed ctd seasoar the seasoar was used to survey the upper 380 m on horizontal scales from 1 40 km around the drifting spar but revealed no advection that could account for the diurnal signal it is concluded that the spar was trapped in a convergence zone where vertical velocities possibly as large as 0 04 m s 1 carried diurnally heated surface water down

kinematic evolution and fracture prediction of the valle morado structure inferred from 3 d seismic data salta province northwest argentina the valle morado structure located in northwest argentina is an approximately 7 km long and 4 km wide north northeast south southwest trending anticline cut by faults that involve paleozoic basement and mesozoic cenozoic sedimentary cover geological interpretation of a three dimensional seismic survey that covers the structure plus a well and two dimensional regional scale seismic lines indicates that the valle morado is an andean pop up structure formed by foreland directed faults resulting from reverse reactivation of cretaceous extensional faults dipping westward and newly formed hinterland directed reverse faults dipping eastward the orientation of the preexisting extensional faults is nearly perpendicular to the andean tectonic transport direction in the northern part of the structure and oblique toward the south resulting in almost pure contraction in the north and transpression southward curvature analysis performed on two interpreted reservoir seismic horizons suggests that the maximum density of open fractures is likely to occur along the anticline axis in the northern portion of the fold and along the northeast southwest striking foreland directed reactivated faults to the south the direction of the open fractures interpreted from ultrasonic borehole image data along the well coincide with that of the open fractures predicted from the curvature analysis

porosity prediction from seismic attributes of the ordovician trenton black river groups rochester field southern ontario this article integrates three dimensional 3 d seismic attributes and log data to determine porosity distribution of the ordovician trenton black river groups within the rochester field southern ontario the rocks are composed of tight limestone parts of which were dolomitized to form porous reservoir rock previous studies of the trenton black river dolomite reservoirs have indicated a close relationship between faulting and reservoir development but few published studies have attempted to examine these relationships using 3 d seismic data this study explores the stratigraphy and structure of the rochester fault related dolomite reservoir using 3 d seismic data and neural networks to predict porosity by predicting porosity using seismic attributes vertical and lateral distributions of porosity that can be used to guide development and exploration drilling for optimal hydrocarbon recovery were obtained the sites of highest porosity were found to be along and within the fault zones faults extending from the basement into overlying paleozoic rocks are composed of several short plane vertical and subvertical fault segments however some of these faults appear to have originated and died within the paleozoic rocks they cannot be traced to the basement because of little or no offset where they penetrate the basement although the five identified attributes are considered important in exploration for fault related dolomite reservoirs the single most important attribute to employ is the amplitude envelope because the other attributes are mathematically related to it furthermore the sags that are seen in the rochester field are due to the combined effects of low velocity pushdown and faulting methods and results presented in this study can be used to explore and develop fault related dolomite reservoirs elsewhere in similar geologic settings

seismic facies analysis based on speech recognition feature parameters abstractseismic facies analysis plays an important role in seismic stratigraphy seismic attributes have been widely applied to seismic facies analysis one of the most important steps is to optimize the most sensitive attributes with regard to reservoir characteristics using different attribute combinations in multidimensional analyses will yield different solutions acoustic waves and seismic waves propagating in an elastic medium follow the same law of physics the generation process of a speech signal based on the acoustic model is similar to the seismic data of the convolution model we have developed the mel frequency cepstrum coefficients mfccs which have been successfully applied in speech recognition as feature parameters for seismic facies analysis information about the wavelet and reflection coefficients is well separated in these cepstrum domain parameters specifically information about the wavelet mainly appears in the low domain part and information about the reflection coefficients

recumbent folds key structural elements in orogenic belts abstract this review has two main parts the first of them presents existing ideas and data related to recumbent folds reviewing aspects such as the physical conditions of the development of these folds the strain inside the folded layers the kinematic mechanisms of their formation the role of gravitational forces the tectonic context of their development and the structures associated with them in the second part the above ideas are discussed and possible mechanisms for the development of these folds are presented it is proposed that initial perturbations of the layers are essential to give rise to the asymmetry of recumbent folds these perturbations may be non planarities of the layering or may be linked to the existence of a core or basement of competent rock that hinders the normal propagation of the deformation this could explain why many large recumbent folds have a root zone deformation with an important component of simple shear is a general condition for the formation of recumbent folds in areas with very low grade metamorphism competent layers often play an active role during the deformation and undergo buckling with the development of an overturned fold limb which can be stretched and thinned to finally produce a pair of recumbent folds separated by a thrust in areas with low or medium metamorphism buckling under a simple shear regime is probably the most important mechanism for producing large folds with gentle or moderately dipping axial surfaces subsequent kinematic amplification by coaxial strain components with vertical maximum shortening is important for the formation of recumbent folds these components involve a sub horizontal stretching that can cause a problem of strain compatibility and give rise to a basal thrust in areas deformed under high p and t conditions recumbent folds can develop by flow perturbations and kinematic amplification of folds this is probably a common mechanism in ductile shear zones

complex seismic trace analysis of thin beds displays of complex trace attributes can help to define thin beds in seismic sections if the wavelet in a section is zero phase low impedance strata whose thicknesses are of the order of half the peak to peak period of the dominant seismic energy show up as anomalously high amplitude zones on instantaneous amplitude sections these anomalies result from the well known amplitude tuning effect which occurs when reflection coefficients of opposite polarity a half period apart are convolved with a seismic wavelet as the layers thin to a quarter period of the dominant seismic energy thinning is revealed by an anomalous increase in instantaneous frequency this behavior results from the less well known but equally important phenomenon of frequency tuning by beds which thin laterally instantaneous frequency reaches an anomalously high value when bed thickness is about a quarter period and remains high as the bed continues to thin in this paper complex trace analysis is applied to a synthetic model of a we

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

mountain building strike parallel motion and mantle anisotropy abstract geophysical and geological evidence indicates that tectonic movements parallel to the strike of orogenic belts and suture zones are the most important mode of displacement during continental collision and oblique subduction several hundred to a few thousand kilometers of displacement may have occurred this way resulting in a pervasive ductile deformation of the lithosphere consequently both crustal and mantle fabrics may reflect these movements and their study using both geological and geophysical methods could supply important clues to lithosphere behavior during mountain building on the basis of kinematic analysis of ductilely deformed crustal rocks in zones of movement a variety of tectonic models have been proposed which differ in 1 1 the timing of strike parallel motions early before or during continental accretion or late after accretion was completed 2 2 the geometric pattern of strike parallel displacement zones low angle or high angle and 3 3 the location of orogen parallel movement zones in outboard terranes on the subducting plate along the suture zone or within the continental hangingwall large scale displacements parallel to mountain belts also suggest that they occurred along lithospheric faults rooted in the upper mantle although few studies have been carried out from this view point thermal structural and petrological data support the conclusion that lithospheric faults involving the upper mantle may be discriminated from crustal faults rooted in some crustal decoupling zone where available data on mantle flow beneath orogenic belts are in agreement with mountain parallel displacements inferred from crustal studies this has an important bearing on the seismic anisotropy pattern which can be predicted in the lithospheric mantle below mountain belts the fast velocity direction which is parallel to the flow direction should therefore be recorded parallel to the strike of the belt

3d avo crossplotting an effective visualization technique crossplots visual representations of the relationship between two variables are used to a visually identify outliers that may bias a correlation b gain a visual sense for the strength of the correlation between variables c detect if the relationship between variables is linear or nonlinear d identify trends which may indicate multiple populations within the same data set and e detect significant departures from a background trend in other words to detect anomalies crossplotting is widely used in avo analysis because it facilitates the simultaneous and meaningful evaluation of two attributes generally common lithology units and fluid types cluster together in avo crossplot space allowing identification of background lithology trends and anomalous off trend aggregations that could be associated with hydrocarbons initially avo crossplotting typically used the intercept and gradient however in 1997 goodway et al used crossplots of elastic parameters lambda rho and mu rho to improve petrophysical discrimination of rock properties other attributes have also been used as avo anomaly indicators castagna and smith 1994 crossplotting appropriate pairs of attributes so that common lithologies and fluid types generally cluster together allows for straightforward interpretation the off trend aggregations can then be more elaborately evaluated as potential hydrocarbon indicators this is the essence of successful avo crossplot analysis and interpretation all of which is based on the premise that data that are anomalous statistically are interesting geologically this article describes attempts to extend crossplotting to three dimensions and assess any advantages that result ross and sparlin 2000 made this extension by using the intercept gradient and inlines for a 3d seismic volume as the three dimensions on a 3d crossplot our procedure begins by first visualizing different combinations of the measured well log parameters p velocity s velocity density porosity and gamma ray in two and three dimensions next observed patterns are visualized and compared in the

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

kinematics of compressional and extensional ductile shearing deformation in a metamorphic core complex of the northeastern basin and range abstract analysis of shear criteria enables the kinematics of two main ductile shearing events d 1 and d 2 to be established in the raft river grouse creek and albion metamorphic core complex the first event d 1 is a nne thrusting and corresponds to mesozoic shortening a well developed non coaxial ductile deformation d 2 of cenozoic age is marked by the occurrence of opposing eastward in raft river and westward shear criteria in albion grouse creek these characterize an arch structure where the shear strain increases outwards in the axial zone of the complex d 2 seems coaxial cenozoic extension is considered to be related to gravitational instability induced by mesozoic overthickening of the crust involving uplift erosion and abnormal heating brittle extension occurs in the upper part of the uplifted domain it is transformed laterally above undeformed basement towards stretched domains of the middle and lower crust through the ductile shear zones localized at the precambrian paleozoic interface this extension of the middle and lower crust occurred in the vicinity of the root zones of the former mesozoic thrusts which may thus have been reactivated as ductile normal faults during cenozoic extension

application of multi seismic attributes analysis in the study of distributary channels abstract during the exploration of stratigraphic reservoirs the key to locating these reservoirs is to identify the sandstone distribution seismic data can be used to recognize large scale distributary channel sedimentary bodies however depiction of sedimentary bodies in small distributary channels using traditional interpretation data from seismic profiles is extremely difficult in the upper cretaceous first sandstone bed of the third member of the nenjiang formation called the nen 3 member for simplicity in the xb area of the southern songliao basin distributary channels are the main sedimentary facies the distributary channels migrate frequently therefore it is difficult to precisely depict the morphology of the channel and the distribution of sandstone in this study we investigated the deposition of distributary channels using equal scale formation plane seismic attributes such as post stack amplitude instantaneous amplitude and seismic waveform classification analyzed well logging data from target formations and mapped the distribution of distributary channels this study shows that seismic sedimentological study and stacking multiple attribute analysis can identify the distribution of distributary channels precisely and effectively the attributes of equal scale strata slices are evidently superior to those of time and horizon slices attribute extraction and selection of equal scale formation slices is an essential step the comprehensive selection of seismic attributes that show a good correlation to a single well can be used to clearly depict channel bodies the overlap of the 40 hz single frequency energy and the rms amplitude depicts the sedimentary characteristics and shapes of sandstone bodies in main channels as well as small scale distributary channels more clearly than a single attribute these attributes show that the first sandstone bed of the nen 3 member was from distributary channels with complex shapes the distributary channels cut across each other vertically and laterally it indicates that during the deposition of the nen 3 member in xb area the direction of the main channel is from north to south and the provenance could be from north and east the method of this paper may provide some helpful suggestions to the geologist using seismic attributes to undertake research on sedimentary environment at other places in the world

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 computer model of sheath nappes formed during crustal shear in the western gneiss region central norwegian caledonides abstract the eastern western gneiss region of central norway is part of the deepest exposed norwegian caledonides where basement gneisses and an overlying thrust nappe sequence have been folded into large fold nappes structural analysis of a fold nappe within the central part of the district the grovudal area suggests that it has a strongly sheath like form and that other fold nappes of the western gneiss region may also have sheath like forms the structural history within the grovudal area is dominated by intense east directed subhorizontal shear in an overthrust sense followed by asymmetric refolding with an easterly vergence a computer generated kinematic model was developed to test whether the regional interference patterns could be explained by sheath fold development during this type of deformation the computer model shows that the major regional interference patterns could have been formed by such a kinematic history but does not rule out other possibile histories the proposed kinematic history is however compatible with the regional tectonic history of the main caledonian nappe pile suggesting that the complex nappe interference patterns typical of the region were formed in a kinematically simple but intense ductile deformation associated with caledonian continental imbrication

a genetic algorithm for filter design to enhance features in seismic images abstract we present a novel method to enhance seismic data for manual and automatic interpretation we use a genetic algorithm to optimize a kernel that when convolved with the seismic image appears to enhance the internal characteristics of salt bodies and the sub salt stratigraphy the performance of the genetic algorithm was validated by the use of test images prior to its application on the seismic data we present the evolution of the resulting kernel and its convolved image this image was analysed by a seismic interpreter highlighting possible advantages over the original one the effects of the kernel were also subject to an automatic interpretation technique based on principal component analysis statistical comparison of these results with those from the original image by means of the mann whitney u test proved the convolved image to be more appropriate for automatic interpretation

on the relationship between kilometer scale sheath folds ductile thrusts and minor structures in the basal high pressure units of the cabo ortegal complex nw spain abstract large sheath folds in the basal high pressure nappes of the cabo ortegal complex are described and a kinematic interpretation provided the principal penetrative and map structures relate to regional d2 deformation which produced foliations s2 bearing mineral and stretching lineations l2 and several types of folds a type sheath like and folded folds the latter structures are subparallel to the trend of the orogen their attitude suggests that the units involved shared a common tectonic evolution during progressive ductile deformation of an anisotropic medium reconstruction of major geological structures was accomplished through projection of map scale features onto the ductile flow plane and the plane perpendicular to the ductile flow direction the structures reconstructed illustrate their development in the deeper structural levels of an orogenic channel subjected to high pressure metamorphism during the early phases of the hercynian orogeny in nw iberia we argue that orogen normal tectonic displacements of up to a few hundreds of kilometers represent the minor components of the transpression with possibly thousands of kilometers along strike dextral displacement between the intervening plates during subduction collision

strike slip deformation reflects complex partitioning of strain in the nankai accretionary prism se japan abstract previous studies have suggested predominant extensional tectonics acting at present on the nankai accretionary prism nap and following a parallel direction to the convergence vector between the philippine sea and amur plates however a complex set of thrusts pop up structures thrust anticlines and strike slip faults is observed on seismic data in the outer wedge of the nap hinting at a complex strain distribution across se japan three dimensional 3d seismic data reveal three main families of faults 1 ne trending thrusts and back thrusts 2 nnw to n trending left lateral strike slip faults and 3 wnw trending to e w right lateral strike slip faults such a fault pattern suggests that lateral slip together with thrusting are the two major styles of deformation operating in the outer wedge of the nap both styles of deformation reflect a transpressional tectonic regime in which the maximum horizontal stress is geometrically close to the convergence vector this work is relevant because it shows a progressive change from faults trending perpendicularly to the convergence vector to a broader partitioning of strain in the form of thrusts and conjugate strike slip faults we suggest that similar families of faults exist within the inner wedge of the nap below the kumano basin and control stress accumulation and strain accommodation in this latter region

extensional shearing deformation and kilometer scale a type folds in a cordilleran metamorphic core complex raft river mountains northwestern utah cordilleran metamorphic core complexes are characterized by ductile mylonitic deformation and regional stretching lineations in the raft river mountains a mylonitic zone and a late superimposed detachment fault separate precambrian crystalline and metasedi mentary basement rocks from an upper plate made of allochthonous paleozoic rocks which suffered a brittle extensive deformation we suggest that the mylonitic ductile deformation is the result of tertiary extensional tectonics strain analysis shows that 1 strain results from large scale progressive shearing deformation in a non coaxial regime 2 e w regional stretching lineations represent the direction of shearing and transport 3 shear criteria indicate an east directed movement 4 strain magnitude is increasing eastward 5 kilometer scale folds parallel to the lineations are interpreted as a type folds formed by eastward shearing of a previously northward dipping layering measurement of striated faults in the upper plate gives an e w direction of extension parallel to the lineations thus ductile and brittle deformations are closely related to the same regional scale extensional tectonics a model is proposed to explain the observed geometry and kinematics of the structures the mesozoic to paleocene cordilleran compressional tectonics induced an overthickening of the crust in the hinterland belt at the future emplacement of the complexes important uplift abnormal heating and granite emplacement occurred later during the collapse of the former belt the combined effects of thermal and gravitational instabilities during tertiary extensional tectonics enabled the development of a ductile shear zone localized at the precambrian basement paleozoic cover interface the brittle extension of the upper crust is displaced laterally along this flat shear zone and transformed farther east into the extended regions of the middle and lower crust

structure of the high grade opatica belt and adjacent low grade abitibi subprovince canada an archaean mountain front plutonic gneisses in the archaean opatica belt in canada record crustal scale wsw vergent i e longitudinal high temperature d1 ductile shearing similar structures occur in adjacent greenstone belts but only in narrow amphibolite facies zones near the base metavolcanics in the greenschist facies portions do not record penetrative d1 structures the greenstone belts are interpreted as allochthonous on the gneisses they form the uppermost d1 thrust sheets sse vergent i e approximately transverse d2 thrusting imbricated the opatica belt and formed a large antiform either a culmination or an antiformal stack in the southern opatica the imbricated opatica belt wedged under the northern part of the abitibi subprovince and created a tight syncline with nnw vergent d2 thrusts interpreted as backthrusts on its northern limb the opatica belt abitibi subprovince contact therefore resembles some phanerozic mountain fronts further southwards propagating imbrication of the crust beneath the abitibi subprovince created a s vergent foreland fold and thrust belt in the overlying greenstones high grade opatica gneisses and adjacent low grade abitibi greenstones contain complementary structural patterns and may therefore represent the internal and foreland parts of an archaean mountain belt similar in many respects to phanerozoic examples

kinematics of ductile shearing from outcrop to crustal scale in the monte rosa nappe western alps significant ductile deformation has produced widespread mylonitic structures in the basement orthogneisses and the mesozoic cover quartzites and marbles of the monte rosa nappe in the inner part of the western alps we summarize here the results of a detailed microstructural study at several scales of observation in the northern part of the nappe and discuss the kinematic significance and compatibility of such results most of the observed deformations can be accounted for by progressive wnw vergent shearing during and after the late eocene within a ductile shear zone of crustal scale the displacement of the hanging wall may have been in excess of several tens of kilometers however some ese vergent shear criteria cannot be reconciled with this general picture and suggest that local backthrusting occurred later near the toe of the monte rosa nappe

multiattribute seismic analysis on avo derived parameters a case study prospecting for reservoir zones in mature trends sometimes requires unconventional exploration tools avo has been successfully used as a direct hydrocarbon indicator in some clastic rocks lately avo inversion for lame parameters and has been shown to enhance identification of reservoir zones furthermore integration of avo derived attribute volumes with other non avo derived seismic attribute volumes can provide meaningful geologic information when tied back to well data and verified as correlating with rock properties this paper provides a case study of a 3d seismic survey in southern alberta canada where a probabilistic neural network solution was employed on avo attributes the results were integrated with other seismic attributes to develop a more comprehensive interpretation

3 d instantaneous frequency used as a coherency continuity parameter to interpret reservoir compartment boundaries across an area of complex turbidite deposition in previous unpublished work we found that anomalous values of instantaneous frequency that is frequency values that are negative or that have positive magnitudes greater than nyquist limit are valuable indicators of alterations in reflection waveshape that occur commonly at stratigraphic terminations inspection of 3 d seismic data across nash draw field on the northwest slope of the delaware basin showed that appreciable wavelet alterations occurred at the boundaries of distinct seismic facies within the targeted brushy canyon reservoirs that are being produced in this field based on this observation we used instantaneous frequency as the fundamental database to define the edge positions and areal shapes of individual reservoir facies within this complex slope basin distribution of siltstones and sandstones commonly thought to be a succession of turbidite depositions we compared the compartmentalization detail derived from this frequency based approach with compartmentalization models provided

mapping spatial variation in rock properties in relationship to scale dependent structure using spectral curvature maps of the three dimensional geometry of geologic surfaces show that structural curvature commonly varies with scale of observation this fact can be viewed as superposition of structures at different wavelengths rock properties such as fracture density and orientation reflect the contribution of superimposed structures for this reason characterization of geologic surfaces is fundamentally different from purely geometrical characterization for which local description of surface properties is sufficient we show that measured curvature decays according to a power law with increasing size of measurement window so short wavelength curvatures do not obscure long wavelength curvatures in the same data set this property can be taken advantage of in a simple technique for automatically mapping multiwavelength curvatures at each point on a surface curvature is measured at a range of wavelengths this curvature spectrum can be analyzed in map view or collapsed into a single value at each point in space the results indicate that complex geologic surfaces can be characterized without any prior knowledge of structural wavelengths and orientation the method should prove useful in applications requiring knowledge of spatial variation in rock properties from remotely sensed data such as exploration for hydrocarbon reservoirs or nuclear waste repositories

methods for source rock identification on seismic data an example from the tanezzuft formation tunisia abstract source rocks occurrence extension and quality in the subsurface are usually characterized directly from well data seismic characterization is however becoming an emerging technique for extending source rock properties beyond well locations and an effective tool for mapping their lateral and vertical heterogeneities the tanezzuft formation in tunisia an extremely organic rich source rock was used as a test for applying and comparing different seismic methods aimed at organic rich sequences characterization the data used consist of a 2d seismic line shot in the northern flank of the ghadames basin tunisia pre stack gathers extracted from an inline of a 3d survey and four wells with a complete set of wireline and petrophysical logs impedance inversion avo and seismic attributes were computed on the seismic lines and compared to well data impedance inversion together with a rock physics model of the formation generated a quantitative estimate of total organic carbon toc content in the studied 2d seismic line avo analysis showed a class iv and a base class iv response for the upper and lower reflectors delimiting the organic rich interval respectively seismic attributes analyzed the formation by exploiting its high impedance contrast and intrinsic anelastic attenuation the three methods here discussed showed coherent results both when compared each other and when compared with the well data and the regional geological model in particular avo and seismic attribute analysis are methods that can be applied without the need of well information and are then feasible methods for the investigation of source rock properties in undrilled basins

integrating 3d seismic curvature and curvature gradient attributes for fracture characterization methodologies and interpretational implications abstractin 3d seismic interpretation curvature is a popular attribute that depicts the geometry of seismic reflectors and has been widely used to detect faults in the subsurface however it provides only part of the solutions to subsurface structure analysis this study extends the curvature algorithm to a new curvature gradient algorithm and integrates both algorithms for fracture detection using a 3d seismic test data set over teapot dome wyoming in fractured reservoirs at teapot dome formed by tectonic folding and faulting curvature helps define the crestal portion of reservoirs that is associated with strong seismic amplitude and high oil productivity in contrast curvature gradient helps define the regional northwest trending and the cross regional northeast trending lineaments that are associated with weak seismic amplitude and low oil productivity in concert with previous reports from image logs cores and outcrops an integrated seismic curvature and curvature gradient analysis suggests t

the role of the shuswap metamorphic complex in cordilleran tectonism a review the shuswap metamorphic complex consists of three parts each with unique stratigraphy and orogenic evolution separated by major faults of diverse nature and having in common only a post late mesozoic tectonic history the first part the monashee complex is a possible extension of the precambrian shield that contains limited evidence of mesozoic orogenesis and that was rapidly uplifted during the cretaceous to paleogene the monashee decollement a warped mylonite zone interpreted as a regional thrust fault active through the middle jurassic separates this complex from the second part which contains rocks correlative with hadrynian to late paleozoic strata of the pericratonic prism the third part the okanagan complex straddling the 49th parallel from the okanagan valley to kootenay lake contains the probable exhumed roots of a mesozoic magmatic arc built upon possible north american continental and transitional crust and includes late paleozoic and early mesozoic suspect terranes the columbian or

seismic imaging of the solfatara crater campi flegrei caldera southern italy new evidence of the fluids migration pathways in the shallow structures abstract seismic imaging is used in this work to reconstruct the shallow structure of the solfatara crater a surface marker of deep magmatic activity inside campi flegrei caldera southern italy we analyze the 1d orthogonal seismic arrays deployed in nne ssw directions for 400 m through the solfatara crater during the recent active experiment ricen repeated induced earthquake and noise performed in the framework of the eu project medsuv seismic data have been edited in the pre stack stage by removing the noisy traces low frequency noise and reduce the ground roll phases then a velocity analysis has been carried out starting from the velocity spectrum to obtain a rms velocity model which has been followed by nmo residual statics and dmo corrections we used the post stack kirchhoff migration technique before the extraction of the energy root mean square envelope and sweetness attributes defining the highest amplitude zones the time gain attribute in order to interpret the deep reflectors and the variance attribute to define the faults discontinuities and chaotic zones amplitude versus offset avo analysis has been performed to identify the gas saturated zone using partial angle stacks which is a benchmark to verify the presence of gas the main contribution of this work is to provide a more detailed and improved seismic reflection image of the shallow depth of the solfatara crater the reliability of our velocity model has been assessed through the use of the vp velocity model previously obtained by the non linear bayesian technique this provides a final stack showing that the shallower minor faults and the extension of the major faults represent the main pathways for the uprising fluids we present the visual evidence for the fluids trapped in the shallower part of the crater at depths between 20 and 50 m below the surface of the crater

lithofacies control on reservoir quality of the viola limestone in southwest kansas and unsupervised machine learning approach of seismic attributes facies classification the hydrocarbon development of the viola limestone in southern kansas usa has encountered challenges regarding the development of a robust data based model of the reservoir quality controls the legacy understanding that hydrocarbon entrapment and reservoir quality are controlled by structure has resulted in less than optimal drilling results in this study an integration of petrographic and geophysical well logs analyses established the main reservoir quality control as dolomitization induced porosity the dolomitization control is supported by comparing best fit trends on density porosity well log values with typical model trends of limestone and dolomite density porosity furthermore this study presents unsupervised artificial neural network ann classification based on five seismic attributes instantaneous frequency energy band width absorption quality factor seismic amplitude that comes in agreement with ca mg ratio and the observed sonic transit time dt log variation with dolomitization porosity increase the hydrocarbon reservoir facies identified by the attributes classification explains the drilling results with high accuracy match to facies class centers and can be used effectively in other settings the integration of multi scale multi data analysis and modeling has provided a solid understanding of the reservoir quality control and distribution this study can be considered as a reliable platform for placing future infill wells in the study area to lower the risk of drilling dry holes