a first attempt at monitoring underground gas storage by means of time lapse multichannel transient electromagnetics two successive transient electromagnetic surveys were carried out over an underground gas storage site in france the idea was to monitor changes in the gas bubble from the differences in the data if successful the new methodology could help to reduce the number of monitoring wells and finally reduce costs preliminary 3d modelling indicated that the resistivity changes caused by movements of the gas water contact should be detectable in the electric field transients provided that the signal to noise ratio is at least 100 1 the surveys were performed with the teamex multichannel acquisition system adapted from a seismics system the highly redundant data were analysed by calculating the relative differences in the electric field transients the differences were common midpoint sorted and spatially stacked another approach was the calculation of electric field time derivatives in a log log domain to eliminate static shift effects which are present in the data even though the data quality is excellent from a classical point of view neither of the two approaches reveals changes in the data which might be caused by changes in the gas reservoir in future applications to monitoring transmitters and receivers should be installed permanently and the transmitter input waveform should be monitored continuously to avoid some of the problems encountered here moreover the signal to noise ratio will have to be further increased by at least one order of magnitude

analysis of the internal structure of a carbonate damage zone implications for the mechanisms of fault breccia formation and fluid flow abstract a segment of the salzach ennstal fault zone talhof fault eastern alps shows evidence for joint nucleation by layer parallel shear causing the formation of joint bounded slices oriented at high angles 65 85 with respect to the shear zone boundary szb subsequent slice rotation resulted in joint reactivation as antithetic shears slice kinking and breaking up of the individual slices into smaller fragments the latter process due to the longitudinal constraint of slices with impeded shear zone widening marked the transition to cataclasite formation and fault core evolution during shear localization cataclasites were subsequently cemented and underwent continuous shear deformation by re fracturing cement precipitation from fluids therefore played a fundamental role in the evolution of the fault zone with a cyclic change between an open and a closed permeability system during fault evolution stable isotope compositions 13 c 18 o of fault rock cements indicate a continuous equilibration between protolith derived fragments and cements precipitated from those fluids this points to limited fluid amounts only temporally replenished by meteoric water and a hydraulic gradient that directed fluid flow from the damage zone towards the fault core

multi method virtual electromagnetic experiments for developing suitable monitoring designs a fictitious co2 sequestration scenario in northern germany we present a numerical study for 3d time lapse electromagnetic monitoring of a fictitious co2 sequestration using the geometry of a real geological site and a suite of suitable electromagnetic methods with different source receiver configurations and different sensitivity patterns all available geological information is processed and directly implemented into the computational domain which is discretized by unstructured tetrahedral grids we thus demonstrate the performance capability of our numerical simulation techniques the scenario considers a co2 injection in approximately 1100 m depth the expected changes in conductivity were inferred from preceding laboratory measurements a resistive anomaly is caused within the conductive brines of the undisturbed reservoir horizon the resistive nature of the anomaly is enhanced by the co2 dissolution regime which prevails in the high salinity environment due to the physicochemical properties of co2 the affected portion of the subsurface is laterally widespread but very thin we combine controlled source electromagnetics borehole transient electromagnetics and the direct current resistivity method to perform a virtual experiment with the aim of scrutinizing a set of source receiver configurations with respect to coverage resolution and detectability of the anomalous co2 plume prior to the field survey our simulation studies are carried out using the 3d codes developed in our working group they are all based on linear and higher order lagrange and n ed elec finite element formulations on unstructured grids providing the necessary flexibility with respect to the complex real world geometry we provide different strategies for addressing the accuracy of numerical simulations in the case of arbitrary structures the presented computations demonstrate the expected great advantage of positioning transmitters or receivers close to the target for direct current geoelectrics 50 change in electric potential may be detected even at the earth s surface monitoring with inductive methods is also promising for a well positioned surface transmitter more than 10 difference in the vertical electric field is predicted for a receiver located 200 m above the target our borehole transient electromagnetics results demonstrate that traditional transient electromagnetics with a vertical magnetic dipole source is not well suited for monitoring a thin horizontal resistive target this is due to the mainly horizontal current system which is induced by a vertical magnetic dipole

mapping sea surface oil slicks using radarsat 2 quad polarization sar image 1 polarimetric sar decomposition parameters average alpha angle and entropy h are estimated for oil slick contaminated sea surfaces and slick free conditions using a radarsat 2 quad polarization sar image the values of h and within oil slick areas are significantly higher than those of the ambient sea surface indicating the dominance of bragg scattering for the slick free ocean and non bragg scattering for the oil slick area in land classification the conformity coefficient is often used to discriminate surface scattering with double bounce or volume scattering based on this rationale we also develop a method using as a logical scalar descriptor to map oil slicks under low to moderate wind conditions the proposed method is assessed using a radarsat 2 quad polarization sar image of oil slicks in the gulf of mexico analysis shows that when is positive the sea surface is slick free whereas is negative for oil slick areas this method provides a simple and effective mapping technique for oil slick detection

electromagnetic mapping of electrical conductivity beneath the columbia basalts sedimentary rocks beneath the columbia river basalt group are recognized as having potential for oil and gas production but the overlying layered basalts effectively mask seismic reflections from the underlying sediments four electromagnetic em methods have been applied on profiles crossing boylston ridge a typical east west trending anticline of the yakima fold belt in an attempt to map the resistivity interface between the basalts and the sediments and to map variations in structure and resistivity within the sediments the em surveys detected strong variations in resistivity within the basalts and in particular the continuous magnetotelluric array profiling emap revealed resistivity lows beneath the surface anticlines these low resistivity zones probably coincide with fracturing in the core of the anticlines and they appear to correlate well with similar zones of low seismic velocity observed on a nearby seismic profile the controlled source em surveys in loop transient long offset transient and variable offset frequency domain were designed in anticipation of relatively uniform high resistivity basalts and were found to have been seriously distorted by the intrabasalt conductors discovered in the field in particular the resistivity sections derived from 1d inversions were found to be inconsistent and misleading the emap survey provided the most information about themore subsurface resistivity distribution and was certainly the most cost effective however both controlled source and emap surveys call for accurate 2d or 3d inversion to accommodate the geological objectives of this project references 18 less

key factors controlling hydrocarbon accumulations in ordovician carbonate reservoirs in the tazhong area tarim basin western china abstract the tazhong area at the center of the tarim basin western china contains abundant hydrocarbon resources principally in ordovician carbonate reservoirs the geological conditions for hydrocarbon accumulation in the area are quite complicated and are characterized by multiple stages of hydrocarbon generation accumulation adjustment and alteration despite decades of exploration and production in the region the mechanisms of hydrocarbon accumulation and their controlling factors are still not well established the geological setting and the distribution characteristics of the reservoir have been used to investigate the mechanisms of accumulation to quantitatively describe the main controlling factors and to predict potential favorable hydrocarbon accumulation zones in ordovician carbonate rocks of tazhong our results show that the hydrocarbons in the ordovician reservoirs came from mixed sources including middle lower cambrian and middle upper ordovician source rocks within the majiaer sag four stages of accumulation are recognized and hydrocarbons migrated into the tazhong area along six intersections of ne and nw fault sets principally from the northeast to the southwest but then locally from the northwest to the southeast the ordovician carbonate reservoirs are typically lithologically defined and the dynamic force of hydrocarbon accumulation is primarily reflects differential capillary forces the accumulation and distribution of hydrocarbons was controlled by the petrophysical properties of the reservoir and by hydrocarbon supply charge energy the petrophysical properties of the reservoir controlled the hydrocarbon accumulation threshold with the maximum differential capillary pressure force on average approximately 13 mpa the supply or charge energy of the hydrocarbons controls the accumulation distribution range the daily production of individual wells decreases with increasing distance from the fault intersections and the maximum hydrocarbon migration distance is about 35 km reservoir properties and the hydrocarbon supply charge energy coupling index rei appear to control hydrocarbon accumulation and distribution accumulation does not occur when the value of rei is 0 6 but is favored when values are higher

crosshole electromagnetic tomography a new technology for oil field characterization with the advent of crosshole seismic technology in the 1980s a new generation of high resolution geophysical tools has become available for reservoir characterization the chief improvement is simply that the tools are deployed in boreholes so measurements take place much closer to the region of interest

dynamic monitoring of coalbed methane reservoirs using super low frequency electromagnetic prospecting abstract dynamic monitoring of coalbed methane cbm reservoirs plays an important role in reservoir evaluation production estimation exploitation and development planning in order to efficiently operate producing wells this paper proposes a passive super low frequency slf electromagnetic prospecting and monitoring method which helps us derive electromagnetic radiation emr anomalies from reservoirs to directly identify and dynamically analyze cbm reservoirs the modeling study shows that the slf magnetic responses are sensitive to high resistivity layers these responses turn out to be approximately stationary and can be seen as simply a component of the background field this stationary background field can be clearly distinguished and then dynamic anomaly extraction would be completed in order to suppress cultural noise and high frequency hf random noise the methods of empirical mode decomposition emd and wavelet transform are used in data processing the reconstructed curves are employed to identify emr anomalies at corresponding depths of reservoirs and subsequently help directly interpret and dynamically monitor reservoirs the slf prospecting method is validated using the field data observed from cbm wells in the years from 2007 to 2013 in qinshui basin china the results present that the high emr wave packets contribute conceivably to the cbm reservoir identification compared with audio magnetotelluric amt inversion results the slf identification resolution is greatly improved the dynamic characteristics of producing reservoirs are revealed using emr anomalies and agree with production histories and other surveys

theoretical analysis of long offset time lapse frequency domain controlled source electromagnetic signals using the method of moments application to the monitoring of a land oil reservoir 1 we present a sensitivity study applied to water front monitoring of an onshore oil reservoir using a remote controlled source electromagnetic method csem with electric dipoles and a borehole to surface configuration we have developed an optimized and parallelized code based on the method of moments in order to study the influence of several static or time varying background uncertainties on the time lapse csem signal also called 4 d csem analysis of the relative and absolute variations in phase or quadrature of the time lapse signal induced by the fluid substitution process inside the reservoir has shown that the vertical electric dipole allows the shape of the water front to be monitored while remaining less sensitive compared to a horizontal electric source dipole to the total volume of substituted fluid we have examined the influence of missed anomalies 1 d 3 d with more or less conductive properties near to the ground surface or the reservoir and with or without time varying properties in most cases the 4 d signal behaves like a reliable filter canceling almost all response anomalies however it can also lead to strong local perturbations of the time lapse signal we have also shown that in the presence of steel cased boreholes at the source location or with outlying steel cased boreholes the recording of exploitable data does not present insurmountable difficulties at low frequencies 1 hz and for a dense array of surface receivers these positive results with csem monitoring suggest that minimal coarse time 3 d explorations should be used to ensure reliable interpretation of the monitored data

from fractures to flow a field based quantitative analysis of an outcropping carbonate reservoir abstract fractures can play an important role in the fluid storage migration properties of fault damage zones in this present contribution we document the role exerted by fractures on fluid flow in carbonate damage zones of hydrocarbon bearing km long oblique slip normal faults with 10 s of m throw the carbonate fault damage zones were analysed by mean of scan line surveys conducted in both tar free and tar rich outcrops in this way the relationships among the individual fracture characteristics length spacing aperture orientation connectivity and distance from slip surfaces pertaining to small faults of the fault damage zones and hydrocarbons have been established data obtained by scan line surveys were also used to compute the amount of fracture porosity the degree of fracture connectivity and based upon simple assumptions the orientation of the local hmax at times of faulting additionally scan line surveys were also carried out along outcrops exposing unfaulted carbonate host rocks the results of our computation are consistent with a carbonate host rock made up of a quite isotropic fracture array comprised of isolated and coupled fractures in which individual fracture sets have negative exponential spacing distributions in terms of fluid flow the fracture array of the carbonate host rock enhances the fluid storage conversely the fracture array of the fault damage zones is characterized by a pronounced anisotropy due to interconnected fractures which enhance the fluid migration fractures in the fault damage zones include those inherited from background deformation and others related to the faulting processes the latter fracture sets are characterized by power law spacing distributions in conclusion counter intuitively both fracture length and fracture spacing do not have any correlation with hydrocarbons in the fault damage zones on the contrary fracture anisotropy fracture spread and fracture orientation are positively correlated with hydrocarbons

integrated geological geophysical characterizations of deeply buried fractured vuggy carbonate reservoirs in ordovician strata tarim basin abstract the central uplift region of the tarim basin contains a series of thick ordovician carbonates that form fractured vuggy hydrocarbon rich reservoirs along an unconformity these fractured vuggy reservoirs are difficult to characterize using traditional well logging and seismic interpretation methods because these carbonates feature complex and heterogeneous lithologies and variations in scale geometry and spatial distribution in this paper a series of deeply buried fractured vuggy carbonate reservoirs are characterized on micro macro and mega scales these characterizations are based on previous studies detailing the carbonate sedimentation diagenesis and tectonic processes in the study area and abundant geological and geophysical data including core samples thin sections and well logging and seismic datasets which have been obtained and upscaled using the choosing classification evaluation generalizing upscaling ccegu method in this area different facies can be identified at different scales 1 detailed core and thin section observations performed based on the dunham classification demonstrate that 7 lithofacies and 19 rock types are present at the micro scale 0 01 m 2 logging data and assorted reservoir characteristics indicate that these 19 different rock types consist of 9 different electro facies at the macro scale 0 1 m 1 m and the presence of electro facies in individual wells can be recognized and 3 these 9 different electro facies comprise 6 distinct seismic facies at the mega scale 10 m and can be used to delineate the spatial outlines of potential reservoirs and evaluate their properties the targets of particular interest in the study area are a series of partially dissolved dolomites located near large faults and a series of vuggy soluble limestones located near ne trending strike slip faults this study combines geological and geophysical response data from fractured vuggy carbonate reservoirs to achieve seamless connections among micro scale macro scale and mega scale observations to effectively characterize a series of strongly heterogeneous fractured vuggy reservoirs this method can also be applied to characterize other deeply buried paleokarst reservoirs in the tarim basin as well as other strongly heterogeneous reservoirs

segmentation and growth of an obliquely reactivated normal fault abstract detailed kinematic analysis of a large 1800 m maximum displacement reactivated normal fault in the taranaki basin new zealand has been conducted using high quality 3d seismic data the parihaka fault is approximately north south striking in basement where it accrued late cretaceous to early eocene displacements in response to east west extension and was obliquely reactivated by nw se extension in the pliocene reactivation resulted in upward propagation newly formed segmentation and up dip clockwise rotation of the fault surface by up to 20 from the strike of the basement fault fault segmentation and map view soft linkage by relay zones in post miocene strata was synchronous with the formation of antithetic faults in late miocene strata at bends in the fault surface fault segment lengths antithetic faults and relay zone dimensions were formed geologically instantaneously during initial reactivation of the main fault at 3 7 3 4 ma i e within the first 10 of faulting rapid formation of pliocene fault segments is followed by displacement accumulation without an increase in fault segment length until eventual relay breaching when continued ramp rotation is unsustainable this evolutionary history is consistent with a model in which arrays of fault segments are from inception components of a single coherent structure

joint inversion of geophysical data summary by jointly inverting several different kinds of geophysical measurements at a site we avoid some of the ambiguity inherent in the individual methods we show how this can be done for the combination of dc resistivity and magnetotelluric measurements on a layered medium by considering a simple 3 layer model the combination resolves the resistivity of the thin resistive second layer even though neither of the two methods can do so alone the method is then applied to field data from a shallow sedimentary basin a blind zone occurs beneath a thick near surface conductive shale by a study of the eigenvalue structure of the model it can be seen that resolution in this zone would be slightly enhanced by higher frequency magnetotelluric data but additional dc data at larger spacing would yield no improvement

field trials of lotem in a very rugged area geophysical surveys are difficult to carry out in southern china because the surface is covered by limestone the geology is complicated and the topography rugged conventional seismic methods are often less than satisfactory because the high velocity surface layer and great velocity variation in the subsurface

papua new guinea mt looking where seismic is blind hydrocarbon exploration in the papuan fold belt is made extremely difficult by mountainous terrain equatorial jungle and thick karstified miocene limestones at the surface the high velocity karstified limestones at or near the surface often render the seismic technique useless for imaging the subsurface in such areas magnetotellurics mt provides a valuable capability for mapping subsurface structure the main structural interface which can be mapped with mt due to the large electrical contrast is the contact between the resistive darai limestone and the underlying conductive sediments of the ieru formation in some areas the base of the darai can be mapped with reasonable accuracy by fitting 1d models to the observed mt data however in many cases where 2d and 3d effects are severe 1d interpretations can yield dramatically incorrect results numerical and field data examples are presented which demonstrate the severity of the 1d errors and the improvements in accuracy which can be achieved using a 2d inverse solution two mt lines over adjacent anticlines both with well control and seismic data are used to demonstrate the application of 1d and 2d inversions for structural models in both cases the seismic data provide no aid in the interpretations the example over the hides anticline illustrates a situation where 1d inversion of either te or tm mode provides essentially the same depth to base of darai as 2d inversion of both te and tm both models provide base darai depth estimates which are within 10 of that measured in the well the example over the angore anticline illustrates the inadequacy of 1d inversion in structurally complex geology complicated by electrical statics the te mode fits a 1d darai thickness of 800 metres while the tm mode fits a 1d darai thickness of 3500 metres bracketing the thickness of 2450 metres observed in the well the final 2d inversion model provides a depth estimate of 2250 metres four mt lines along the angore anticline have been interpreted using 2d inversion a high degree of correlation exists between lineaments observed on an airborne radar image and zones of low resistivity within the high resistivity material interpreted as darai limestone these low resistivity zones are interpreted as fault zones three dimensional modelling has been used to simulate 3d statics in an otherwise 2d earth these data were used to test the groom bailey gb decomposition for possible benefits in reducing static effects and estimating geoelectric strike in the papua new guinea png field data it has been found that the gb decomposition can provide improved regional 2d strike estimates in 3d contaminated data however in situations such as png where the regional 2d strike is well established and hence can be fixed the gb decomposition provides apparent resistivities identical to those simply rotated to strike

effects of structural segmentation and faulting on carbonate reservoir properties a case study from the central uplift of the tarim basin china abstract the largest condensate field of the ordovician reef shoal reservoirs in china was discovered along the n 1 fault zone in the tarim basin however current drilling activities are hindered by the low and unstable production from these carbonate reservoirs a detailed structural analysis of 3 d seismic data identified three segments along the n 1 fault zone characterized by differences in structural geometry and evolution segmentation of the n 1 fault zone has resulted in the variation of characteristics and distribution of the upper ordovician carbonate reservoirs due to fault induced differential uplift before the late ordovician a narrow and thick rimmed platform margin rich in reefs has developed in the eastern segment whereas wider and thinner shoals developed in the central and western segments we clearly identified a fault block uplift related erosional unconformity and associated karstification at the top of the upper ordovician carbonates in the eastern segment in this segment the karst caves resulted in the high and stable hydrocarbon production in the central segment good matrix reservoirs exist but due to the lack of fault related enhancement of the reservoirs quality only relatively low production is observed in the western segment where fracture vug reservoirs occurred in relation to later fault damage zones production is much greater but unstable large scale fracture caves reservoirs related to fault activity rather than the good unfaulted matrix reservoirs lead to the high production of oil and gas we classify these reef shoal reservoirs as faulting modified reservoirs further exploitation should focus more on the fault damage zone beyond the platform margin rather than the microfacies in the lower paleozoic carbonates

a borehole to surface electromagnetic survey the results of a limited field trial confirm the usefulness of borehole to surface electromagnetic em measurements for monitoring fluid extraction a vertical em profiling experiment was done at the university of california richmond field station where we simulated a brine spill plume by creating a saline water injection zone at the depth of 30 m the data acquisition mode was analogous to the reverse vertical seismic profiling vsp configuration used for seismic measurements in that the em transmitter traversed the pvc cased borehole used for fluid injection and extraction while the receivers were deployed on the surface the em measurements were made at 9 6 khz with an accuracy of 1 in signal amplitude and 1 in signal phase observations were taken at 5 m intervals along two intersecting profiles that were centered on the injection well and extended for 60 m on either side of it the presence of the injected salt water at the expected 30 m depth was indicated clearly by differences between the p

integrating 3 d seismic data field analogs and mechanical models in the analysis of segmented normal faults in the wytch farm oil field southern england united kingdom we propose a methodology for the analysis of normal fault geometries in three dimensional 3 d seismic data sets to provide insights into the evolution of segmented normal fault systems and to improve recovery efforts in fault controlled oil fields limited seismic resolution can obscure subtle fault characteristics such as segmentation and gaps in fault continuity that are significant for oil migration and thus accurate reservoir characterization detailed seismic data analyses that incorporate principles of normal fault mechanics however can reveal evidence of fault segmentation we integrate seismic attribute analyses outcrop analog observations and numerical models of fault slip and displacement fields to augment the use of 3 d seismic data for fault interpretation we applied these techniques to the wytch farm oil field in southern england resulting in the recognition of significant lateral and to a lesser extent vertical segmentation of reservoir scale faults slip maxima on fault surfaces indicate two unambiguous segment nucleation depths controlled by the lithological heterogeneity of the faulted section faults initiated preferentially in brittle sandstone and limestone units subsequent growth and linkage of segments predominantly in the lateral direction resulted in composite fault surfaces that have long lateral dimensions and multiple slip maxima reservoir compartmentalization is greatest at the level of prevalent segment linkages which corresponds at wytch farm with the predominant hydrocarbon producing unit the sherwood sandstone at relatively shallower depths fault segments are younger and less evolved resulting in a greater degree of segmentation with intact relay zones

implications of passive salt diapir kinematics for reservoir segmentation by radial and concentric faults abstract reservoirs associated with salt diapirs that are circular or elliptical in plan view can be segmented by radial faults concentric faults both or neither explanations for this variation are offered based on integration of fault kinematics published studies and seismic examples strata around diapirs can be divided into three structural domains with characteristic fault styles 1 roof zone between the present day depositional surface and crest of a buried inactive diapir this zone is characterised by doming radial faults and occasionally conic graben doming is usually caused by differential compaction and increases with depth 2 a steeply dipping sheath of strata surrounds the diapir out to a distance of less than one diapir radius recording near surface diapir growth in poorly lithified sediments these contain early gravity slumps and late concentric extensional faults regional layer bound polygonal fault systems form radial faults within approximately one diapir radius the only significant radial faulting mechanism below the roof zone 3 diapir root zone of strata whose structural architecture records the diapirs initiating mechanism typically rim synclines or graben that detach on the salt source layer concentric faults at radial distances of a kilometre or more have been found only in root zone rim synclines and sheared sheath strata these models and observations can assist seismic interpretation and structural model building in areas of poor geophysical imaging for instance below overhanging salt

internal structure of mount merapi indonesia derived from long offset transient electromagnetic data 1 a long offset transient electromagnetic lotem survey was carried out on merapi volcano indonesia in 1998 lotem data have been recorded at 41 receiver locations which cover a 10 km w e and a 15 km s n profile the signals were transmitted at four locations on the south west and north sides of merapi the data were interpreted with one dimensional 1 d inversions in addition two particular features were investigated with 3 d modeling on the south flank the magnetic field data show strong 3 d distortions consistently over the profile which can only be explained by a conductive near surface structure like a fracture filled with conductive fluids the simulation of topographic effects shows that the interpretation is not significantly affected on both profiles the most striking feature is a conductive layer of 20 m at depths of 500 1000 m below the surface and a thickness of 1 2 km the cause of the increased conductivity may be different for the summit area the intermediate zone and at the flanks below the summit in vicinity of the conduit the decrease in resistivity is produced either by hydrothermal fluids by partial melts or rocks altered by the hydrothermal system or by a combination in the intermediate zone between the conduit and the flanks either alteration or hydrothermal fluids may be the source of the conductivity increase fluids seem to be the most likely cause for the conductive layer at the flanks and the west east striking anomaly from the resistivity of the conductive layer and the typical porosity of volcanic rock we estimate fluid resistivities of 0 2 1 m

offset and evolution of the gowk fault s e iran a major intra continental strike slip system abstract we use drainage reconstructions to estimate long term offsets on the gowk fault an oblique right lateral strike slip fault in eastern iran on which there have been a number of recent large earthquakes a 3 km horizontal offset is inferred from well preserved geomorphology we further identify a total cumulative offset of 12 km which produces a simple reconstruction of geomorphology across the fault filling in pull apart basins restoring rivers to linear courses across the fault trace and aligning structural and bed rock features the probable age of the gowk fault and k ar dating of offset basalts north of the study region suggest an overall slip rate of 1 5 2 4 mm year this is small compared with the overall 10 20 mm year of shear expected between central iran and afghanistan and the deficit is likely to have been accommodated on other faults east of the gowk fault drainage displaced by dextral movement leads to the development of a series of basins along the fault and a longitudinal topographic profile that resembles an asymmetric saw tooth the geomorphic evolution of the fault zone at the surface includes both normal and reverse faulting components reflecting a probable ramp and flat structure in cross section this interpretation is consistent with evidence from the analysis of seismological radar and surface rupture data in recent earthquakes

influence of strike slip fault segmentation on drainage evolution and topography a case study the palomares fault zone southeastern betics spain abstract the palomares fault zone pfz is one of the main sinistral strike slip faults in the betics se spain with approximately 16 km of north south displacement the pfz initiated during the tortonian messinian as a transfer structure linking areas subject to nw se shortening during the plio quaternary the fault zone lengthened cutting previous fold structures and widened towards the east displacing the active mountain front to the western border of sierra almagrera sierra almenara these sierras which show moderate uplift rates of 0 05 0 15 m ka formed in response to the oblique slip regime of the pfz the drainage system in the vicinity of the pfz is asymmetric with respect to a main axial valley that runs parallel to the pfz on the downthrown fault block in this block the drainage density is lower and the streams are longer than in the uplifted block furthermore west of the main axial valley the streams describe eastward directed deflections indicating the progressive eastward migration of the main axial valley during the pleistocene the drainage system on the uplifted ranges shows a consequent pattern indicating recent uplift and folding under nnw sse convergence recent activity along segments of the pfz has increased topographical gradients favouring dissection of previous streams by headward erosion of streams transverse to the active fault segments

origin of deep strata gas of tazhong in tarim basin china abstract tazhong is located in the interior of the taklamakan desert in the tarim basin deep carbonates are targeted exploration areas with abundant gas and the largest ordovician gas condensate field has been discovered the hydrocarbon is mainly distributed in the reef shoal complex of the upper ordovician lianglitage formation and in the interbedded weathered reservoirs of the lower middle ordovician yingshan formation despite the deep burial depth of the reservoirs and strong heterogeneity the reservoir bodies are large multiple layered and enrichment in hydrocarbons indicates a great exploration potential the ordovician gas condensate reservoir in the tazhong consists mainly of methane with a gas dryness coefficient of 0 91 0 98 the ordovician gas in the tazhong belongs to secondary oil cracking gas the comprehensive analysis of natural gas composition stable carbon isotopes and adamantane content showed that the natural gas was from paleo reservoir cracking at depth basin geothermal history burial history fluid inclusion data and geological analysis show that the gas accumulation occurred 5 ma ago the sulfur isotope of sulfides the presence of 2 thia adamantane and existence of light co 2 carbon isotopes indicate that the h 2 s was formed via tsr the natural gas accumulated through migration along faults

low angle normal fault lanf zone architecture and permeability features in bedded carbonate from inner northern apennines rapolano terme central italy abstract fault zones have the capacity to be hydraulic conduits within upper crustal levels allowing migration of large volume of fluids through shallow and deeper geological environments low angle normal faults lanfs crosscutting carbonate rocks produce damaged volumes that may have a relevant role in channelling or hosting geothermal fluids therefore deserving of investigation to better predict mining targets deformation along lanfs zones dissecting carbonate successions produces permeable volumes presently exploited in the larderello and monte amiata geothermal areas italy in this paper the architectural and permeability features of an exhumed lanf zone exposed in the northern apennines rapolano terme central italy affecting cretaceous bedded limestone are presented such a fault was not affected by circulation of geothermal fluids but its features could reveal much on the potential impact on fluids migration in the active geothermal areas therefore resulting an intriguing analogue the study lanf zone consists of faults which enucleated at depth 4 km during its earlier stage of evolution dissolution seams often arranged in s c fabric characterised the whole damage zone dissolution seams developed under very low grade metamorphism t 100 150 c as indicated by illite crystallinty analyses fault zone architecture and permeability features changed during the fault growth and exhumation permeability heterogeneity and anisotropy characterised the lanf zone during its development if geofluids circulated within the fault zone it could be an effective barrier during its earlier evolution being accompanied by dissolution seams on the contrary it could play as combined barriers conduits during its later evolution progressively at shallower levels being characterised by intersecting fault planes which define pipe like conduits parallel to the direction of the tectonic transport such a configuration could have the capacity to impact on fluids migration for long paths across the upper crustal levels this adds significant information for predicting deeper geothermal circuits and the location of potential exploitable reservoirs in active tectonic environments

geometry and scale of fault segmentation and deformational bulging along an active oblique slip fault wairarapa fault new zealand the active dextral reverse wairarapa fault in the north island new zealand cuts ca 12 ka post last glacial maximum post lgm fluvial gravels with a highly segmented fault trace this

evolution of fracture and fault controlled fluid pathways in carbonates of the albanides fold thrust belt the process of fracture and fault formation in carbonates of the albanides fold thrust belt has been systematically documented using hierarchical development of structural elements from hand sample outcrop and geologic map scales the function of fractures and faults in fluid migration was elucidated using calcite cement and bitumen in these structures as a paleoflow indicator two prefolding pressure solution and vein assemblages were identified an overburden assemblage and a remote tectonic stress assemblage sheared layer parallel pressure solution surfaces of the overburden assemblage define mechanical layers shearing of mechanical layers associated with folding resulted in the formation of a series of folding assemblage fractures at different orientations depending on the slip direction of individual mechanical layers prefolding and folding related fracture assemblages together formed fragmentation zones in mechanical layers and are the sites of incipient fault localization further deformation along these sites was accommodated by rotation and translation of fragmented rock which formed breccia and facilitated fault offset across multiple mechanical layers strike slip faults formed by this process are organized in two sets in an apparent conjugate pattern calcite cement and bitumen that accumulated along fractures and faults are evidence of localized fluid flow along fault zones by systematic identification of fractures and faults their evolution and their fluid and bitumen contents along with subsurface core and well log data we identify northeast southwest trending strike slip faults and the associated structures as dominant fluid pathways in the albanides fold thrust belt

paleozoic fault systems of the tazhong uplift tarim basin china abstract this report presents interpretations developed from a detailed study of new three dimensional 3 d high resolution reflection seismic data in a portion of tarim basin the tectonic history began with oceanic spreading during the cambrian early ordovician and continues beyond the silurian devonian time of oceanic closure paleozoic faults of the tazhong uplift in the hinterland of tarim basin are capped by thick and undisturbed meso cenozoic sedimentary sequences four paleozoic fault systems have been recognized 1 the cambrian early ordovician extensional faulting 2 the late ordovician nww trending thrust faulting 3 the silurian devonian nne strike slip faulting and 4 the permian plutonism influenced by pre existing fault planes zones of weakness created during cambrian early ordovician extensional faulting influenced subsequent tectonic movements the late ordovician fault system divides the tazhong uplift into several deformation zones their mechanical characteristics vary across the study area with stronger thrusting in the east the silurian devonian strike slip fault system consists of three components main faults subordinate en echelon faults and fault troughs the main faults appear as steeply dipping almost vertical offsets on seismic map view with associated flower structures on seismic profiles together with other levels of faults the permian magmatic plugs have a spotty or bandy distribution and are interpreted to have utilized former faults