prerift and synrift sedimentation during early fault segmentation of a tertiary carbonate platform indonesia abstract eocene carbonate deposits of the barru area sulawesi indonesia provide a rare insight into sedimentation prior to and during propagation of normal faults to the surface three main successions late prerift latest prerift earliest synrift and synrift are characterised by distinctive facies associations and sequence development shallow water foraminiferal shoals and intervening lower energy depositional environments occurred during the late prerift in areas which latter formed footwall highs and hangingwall depocentres respectively during the latest prerift earliest synrift shallow water shelves deepened laterally into slope environments in developing hangingwall depocentres in both these sequences sections in developing hangingwall areas are thickest deepen up section and thin laterally towards growing footwall highs active faulting resulted in rapid drowning of hangingwall depocentres and massive reworking of material derived from collapse of the platform margin and adjacent shallow water emergent footwall highs differential subsidence controlling water depths and accommodation space types of carbonate producers and active faulting were the main factors affecting depositional environments and facies distributions carbonate producers are extremely sensitive indicators of depositional water depth and energy hence rapid lateral and vertical facies variations in the barru area provide quantifiable insight into environmental changes prior to and during active faulting

a reappraisal of the 1894 atalanti earthquake surface ruptures central greece this article presents the results of new field and aerial photo surveys of the atalanti fault and of the mesoseismal area of the 20 and 27 april 1894 earth quakes coupled with a reanalysis of contemporary reports and previous investiga tions these are used to gain a better understanding of the faults responsible for these events and their seismic behavior the first shock was smaller and probably located inshore or offshore the malessina peninsula no resolving field evidence has been found to locate the seismogenic structure responsible for this shock on the basis of the limited information available we suggest the malessina escarpment a 12 km long ene trending nw dipping fault as a possible structure responsible for this event on the other hand the second and largest shock is definitely related to the atalanti fault sensu stricto a main wnw trending n dipping active fault extending between the platirema valley a few km nw of the town of atalanti and larymna the total length of the rupture recognized in the field is about 32 km but it can be extended further se up to 40 km no evidence for a longer rupture extending some other 20 km to the nw between the karagiozis river and ag kostantinos is found the complex geometry of the fault with bends and step overs appears to be controlled by preexisting transverse structures minimum coseismic vertical throws measured in the field after more than a century elapsed from the earthquake are 30 80 cm thus consistent with contemporary reports indicating 1 m average slip rates are not well constrained the available estimates fall in the range 0 1 0 5 mm yr confirming the smaller amount of crustal extension taking place in this area with respect to other nearby regions such as the corinth gulf no new data are available to define the average recurrence interval typical of the atalanti fault however a reconsideration of the existing information induced us to rule out the possibility that the famous 426 b c earthquake occurred on the atalanti fault on the basis of the extent and size of the rupture recognized in the field a m 6 8 is estimated for the second and largest shock

three dimensional quantitative modeling of clinoform development abstract clinoform geometry pervades stratigraphic sequences across a variety of scales it is a composite surface which records the complex interplay between accommodation sediment supply physiography and hydrodynamics much of the sequence stratigraphic technique employs clinoform geometry to discriminate between the various systems tracts that constitute depositional sequences however many sequence stratigraphic models treat the generation of accommodation and the input of sediment supply as a two dimensional problem by assuming a line source of sediment entering a system impacted by relative sea level fluctuations one common attribute of clinoforms regardless of size and or shape is that their formation is inherently three dimensional therefore the clinoform geometry varies spatially and temporally throughout a region depending on the proximity to the sediment source and the character of the hydrodynamic regime we present a three dimensional stratigraphic model that combines both diffusion and advection to simulate across and along margin sediment transport and deposition this model allows us to examine how the morphology and internal clinoform geometry of deltas vary away from the sediment source in this application we simulate the development of a delta in a low energy environment to understand the importance of along shelf diffusion on clinoform geometry and the morphology of the delta we predict the three dimensional geometry and how it varies throughout a relative sea level cycle our model indicates that when the clinoform rollover is spatially coincident with the shoreline position the clinoform geometry changes dramatically along strike away from the sediment source region throughout a relative sea level cycle for example oblique clinoforms develop near the source region and evolve into an onlapping sequence along strike on the basis of stratal geometry and the technique of sequence stratigraphy this deposit would be interpreted as two different sequences with very different connotations for their formation we surmise that when the clinoform rollover and the shoreline position are separated e g a subaqueous delta the along strike variability of the clinoform geometry diminishes because of the hydrodynamic forces operative across the shelf consequently it is important to determine how clinoforms develop in three dimensions and to ensure that our window of observation is sufficient to discern between local and regional variability

modelling of hydrocarbon generation in the cenozoic song hong basin vietnam a highly prospective basin abstract the cenozoic song hong basin situated on the northern part of the vietnamese shelf has been only sporadically explored for hydrocarbons a review of the results of the exploration efforts so far shows that the distribution of potential source rocks and their time of hydrocarbon generation are the critical risks for finding commercial amounts of hydrocarbons in the song hong basin including the hanoi trough the rocks most likely to have source potential are 1 oil prone eocene lower oligocene lacustrine mudstones and coals 2 oil and gas prone middle miocene coal beds 3 gas prone upper oligocene lower miocene coals and 4 gas and oil prone miocene marine mudstones to assess the time of hydrocarbon generation from these units relative to the formation of traps the generation history was modelled at 32 well and pseudo well locations the modelling demonstrates that the two first mentioned source rock units are especially important in the northern and northeastern part of the basin and along its western margin traps may have been charged by eocene lower oligocene source rocks in the hanoi trough the excellent middle miocene coal beds have probably generated hydrocarbons within the last few million years thus the huge and still underexplored song hong basin provides attractive areas for further exploration

influence of pre existing pervasive fabrics on fault patterns during orthogonal and oblique rifting an experimental approach abstract pervasive mechanical anisotropy e g metamorphic foliation in the pre rift basement rocks often appears to control the orientation of new faults in natural rift systems and thus tend to influence formation of fault bounded sedimentary basins however the extent to which this influence works in nature has remained debatable and contrasting ideas exist regarding the issue of structural inheritance in natural rifts like the east african rift system earlier experimental works have investigated different kinematic aspects of faulting in simulated orthogonal and oblique rift systems including the role of a crustal scale pre existing zone of weakness on continent scale rifting these experiments have tested the influence of discrete pre existing weak zones e g pre existing faults or an ancient orogenic belt on localization of subsequent rifting but have not considered the control of pervasive fabric anisotropy e g metamorphic foliation etc in pre rift basement rocks on the fault patterns during rifting here we present a series of simple roughly scaled analog model experiments where pervasive strength anisotropy in the basement was created by brushing plaster of paris on a viscous pitch substratum this way a transverse anisotropy of tensile strength was generated in the plaster of paris layer due to thickness variation across the brush marks the basement was overlain by a dry sand pack simulating weak sedimentary rocks overlying a foliated crystalline basement orthogonal and oblique extension of the models at various angles and with differently oriented strength anisotropy exhibited the control of the anisotropy on the orientations of new faults in the sand layer in general anisotropy could significantly control the fault pattern only when it was at a high angle 45 with respect to the maximum instantaneous horizontal stretching direction e h1 otherwise they largely disregarded the anisotropy and formed orthogonal to e h1 faults never formed orthogonal to the displacement vector d in oblique rifting unless the fault controlling anisotropy was perpendicular to d faults strongly following the anisotropy were much longer than those not following that trend faults oblique to the anisotropy were short segmented and tortuous in nature and mainly grew by segment linkage the experimental results support many field observations made in the east african rift system and are likely to be applicable to other rift systems like gondwana basins of india where field data on such structural inheritance are meager

sublacustrine gravity induced deposits the diversity of external geometries and origins abstract our current knowledge of deep water depositional systems is mainly built of extensive achievements obtained from marine basins although lacustrine basins are important oil gas productive areas of the world gravity induced deposits in these basins are poorly understood in the literature when compared with those documented in marine basins based on new insights from 3d seismic data this paper attempts to investigate the effect of the interaction between gravity induced flows and lake floor topography on the resulting external geometry of gravity induced deposits in the cretaceous qingshankou and nenjiang formations of the songliao basin slb eight different shapes of gravity induced deposits were identified in the slb and which were in turn grouped into four distinct categories according to external shape internal architecture and spatial assembly 1 channel fan complexes 2 fan form complexes 3 strip form complexes and 4 pond form complexes furthermore fan form complexes can be subdivided into four subcategories isolated fan with compressional ridges isolated fan without compressional ridges mother son fans and stacked fans strip form complexes can be subdivided into two subcategories including strip form controlled by gully system and strip form controlled by growth faults sediment transport mechanism density flows or mass transport flows and lake floor topography together influence the pathways runout distances discharge places and internal characteristics of gravity induced deposits which could ultimately influence external geometries of gravity induced deposits in the slb consequently sublacustrine gravity induced deposits does not exhibit classic fan like geometry frequent and powerful hyperpycnal flows associated with flood events are fairly common and develop channel distal fan complexes mtds exhibit various external geometries which are significantly affected by growth faults slope gullies gradient and basin floor irregularities the new depositional model built from the slb is vital to understanding the distribution of gravity flow deposits in a sublacustrine slope

relating petroleum system and play development to basin evolution west african south atlantic basins abstract sedimentary basins can be classified according to their structural genesis and evolutionary history and the latter can be linked to petroleum system and play development we propose an approach in which we use the established concepts in a new way breaking basins down into their natural basin cycle division then defining the characteristics of each basin cycle including the type of petroleum systems and plays they may contain and comparing them with similar basin cycles in other basins thereby providing a means to learn through a greater population of perhaps not immediately obvious analogues furthermore we introduce the use of the trajectory plot as a new tool in such an analysis this methodology has been applied to the west african south atlantic marginal basins between cameroon and angola and we demonstrate that the similar tectonostratigraphic evolution of the individual basins along this margin has led to the development of similar types of petroleum systems and play level s consequently we can make analogue comparisons among these basins in order to evaluate and predict the presence of potential yet undiscovered hydrocarbon accumulations in less well explored parts of the margin

application of organic facies studies to sedimentary basin analysis a case study from the yitong graben china abstract an organic facies is defined in this paper as a mappable stratigraphic unit containing organic matter om of a particular genetic type in certain abundance several concepts concerning organic facies are proposed and their significance in basin analysis is discussed in detail a combined sedimentological and organic geochemical investigation has been carried out in the yitong graben and four organic facies and one organic parafacies have been recognized distinct organic basin fill sequences obfs and organic facies association ofa were developed in different sub units of this graben which indicates that the yitong graben had undergone two tectonic subsidence cycles such tectonic subsidence patterns could not have been found out without detailed organic facies analysis confirming that organic facies especially obfs and ofa study is a very useful tool not only for prediction and three dimensional mapping of petroleum source rocks but also for sedimentary basin analysis

generation of gas and oil from coal and other terrestrial organic matter abstract late carboniferous permian sedimentary rocks contain the world s largest coal reserves which have generated and released gas but little if any oil in comparison organic matter deposited in lacustrine fluvial deltaic or brackish water sediments has sourced large quantities of waxy oils in countries such as china australia the u s a argentina venezuela and indonesia plus gas and condensate in deltas worldwide why is more oil coming from land derived organic matter disseminated in sediments than from the carboniferous permian coal beds which also are land deposits the answer appears to be in the hydrogen content and the ease of migration when organic matter and coals have high hydrogen contents relative to carbon they can form oil when the hydrogen is low mainly gas is formed most of the world s coal is low in hydrogen whereas much of the terrestrial organic matter disseminated in sediments is higher in hydrogen so it forms more oil also both gas and oil are adsorbed on coal more strongly than on the disseminated kerogen of sedimentary rocks this makes migration of oil out of the coal more difficult compared to migration from conventional shale source rocks

investigation and dynamic analysis of the long runout catastrophic landslide at the shenzhen landfill on december 20 2015 in guangdong china at 11 40 a m december 20 2015 a catastrophic landslide occurred in shenzhen guangdong southeast china seventy seven people were killed and 33 buildings were buried or damaged which were in the direct path of the landslide at the guangming new district the landslide involved 2 73 million m3 of the municipal solid waste msw and had a horizontal runout distance of 1100 m over a vertical distance of 113 m which was equivalent to a fahrboschung of 6 and covered an area of 0 38 km2 basic post failure characteristics are described in this study dynamic simulation software danw and rheological models were used to simulate the runout behavior of the displaced landslide material in order to provide information for the hazard zonation of similar types of potential msw landslides the simulated results revealed that a combination of the frictional model and voellmy model is able to provide the best performance in simulating this landslide also the results showed that this landslide had a duration of about 50 s with a maximum velocity of 22 4 m s it was expected that these models and parameters could improve the accuracy of future hazard assessments of areas with geological topographical and climatic features similar to the shenzhen hong ao landfill

uncertainty analysis of tunnel squeezing for two tunnel cases from nepal himalaya abstract weak rocks such as shale slate phyllite and schist and the rock mass of weakness fault zones are incapable of sustaining high tangential stress severe tunnel squeezing is therefore common in the tectonically active himalayan rock mass and is one of the major areas of concern regarding stability a reliable prediction of the extent of squeezing is essential so that a strategy can be established regarding stabilizing measures and for optimizing the support well in advance during planning and design in this paper a probabilistic approach to uncertainty analysis that focuses on the effect of the variations in each input parameter of squeezing is used for analyzing and predicting the extent of tunnel squeezing for two tunnel cases in nepal kaligandaki a completed and middle marsyangdi under construction a semi analytical method suggested by hoek and marinos predicting tunnel squeezing problems in weak heterogeneous rock masses tunnels tunnell int 2000 32 11 and 12 45 51 and 34 36 for predicting squeezing an empirical formula proposed by panthi analysis of engineering geological uncertainties related to tunnelling in himalayan rock mass conditions phd thesis department of geology and mineral resources engineering norwegian university of science and technology ntnu norway 2006 and the palisade s 2002 version of risk statistical software program have been used for the uncertainty analysis the analysis results for kaligandaki indicate fairly good correlation between predicted and actually measured squeezing the same approach has been used for predicting the degree of tunnel squeezing at middle marsyangdi tunnel it is concluded that the methodology proposed in this paper has potential for predicting the squeezing of future tunnel projects in weak rock mass conditions

post rift anomalous thermal flux in the songliao basin ne china as revealed from fission track thermochronology and tectonic analysis abstract the songliao basin in northeastern china contains a nearly complete cretaceous sedimentary record it offers an unparalleled opportunity for studying the thermal behavior of a rifting basin adjacent to a subduction zone during various stages of its evolution the post rift thermal history of the songliao basin is here documented by systematic apatite and zircon fission track analyses on newly exhumed sandstone samples from the upper cretaceous quantou and qingshankou formations the combination of thermochronology results and stratigraphic records indicates that there was an unambiguous post rift thermal overprinting event in the songliao basin during the deposition of the nenjiang formation at 85 80 ma this fossil thermal anomaly has not been previously recognized from organic maturity indicators and or subsidence modeling the zircon fission track results indicate an estimated maximum paleo temperature as high as 170 220 c near the daqing placanticline fission track analyses of sampled apatites further define a restricted thermal anomaly in the central part of the basin based on the context of local lithospheric structure and adjacent plate tectonic history we conclude that the late cretaceous westward subduction of the paleo pacific plate not only produced vertical motions and directly controlled the topography of the songliao lake but also dominated the mantle heat flow beneath east asia this finding has significant implications for the evolution of thermal flux in the basin

sea ice roughness from airborne lidar profiles light detection and ranging lidar data acquired during the amsr ice03 arctic flights are used to observe and characterize the spectral behavior of sea ice roughness height distributions and roughness spectral densities are derived from surface profiles measured over a variety of sea ice types the spectral densities are fit to lorentzian curves to obtain the correlation length and root mean square height of roughness within the sampling bandpass of the lidar profiler the utilization of these spectral parameters outside of their bandpass is also discussed

numerical simulation of the thermal maturation oil generation and migration in the songliao basin northeastern china abstract the discovery of the giant daqing oil field in the songliao basin led to the realisation of the significant petroleum potential of non marine basins in order to reconstruct the basin evolution and oil formation an integrated organic geochemical basin modelling study along a regional transect across the songliao basin was conducted it provided a regional heat flow evolution model and revealed post orogenic or late syn orogenic maturation in the central depression and pre orogenic maturation in the southeast uplift zone kinetic parameters of petroleum generation for the lacustrine source formations are the basis for the simulation of oil generation and migration in the songliao basin using the principle activation energy peaking at 54 kcal mol and a pre exponential factor of about 4 2 1027 ma 1 the simulation obtained a relatively good match with the measured transformation ratios the qingshankou formation in the west and east central depressions constituted the major source in the basin major oil generation migration and accumulation occurred during the early tertiary in the west central depression the generated oils migrated upwards into the yaojia formation followed by the updip migration into the daqing anticline and towards the local structural high along the west slope in contrast the oil migration in the east central depression was dominated by the downward movement from the lower member of the qingshankou formation followed by the updip migration towards the caoyang anticline the simulated oil accumulations are in good agreement with discovered oil fields implying a potential application of the model for prediction and evaluation of new exploration targets in the basin

rock magnetic records of the qingshankou formation of sk 1 south borehole in songliao basin northeast china and their paleoclimate implications abstract the south borehole sk 1s of the china cretaceous continental scientific drilling project songke 1 penetrated the late cretaceous lacustrine sediments in the central depression of the songliao basin northeast china in order to reveal the terrestrial records of the cretaceous climate changes high resolution rock magnetic records were obtained on the qingshankou formation k 2 qn of sk 1s the results indicate that detrital magnetite is the main remanence carrier of the k 2 qn formation while both magnetite and paramagnetic minerals including clay minerals and pyrite dominantly contribute to magnetic susceptibility although reductive diagenesis may have more or less effect on the magnetic signals of the k 2 qn formation they recorded ancient lake level changes well resulting both from the tectonic development of the basin and from the milankovitch astronomical paleoclimatic changes the first order vertical trends of the rock magnetic records were controlled by the shallowing upwards of the lake level caused by the tectonic uplift of the basin the short term variations of the rock magnetic records were controlled by the lake level periodical drift caused by the fluctuations of the rainfall of the catchment area of the basin which were controlled by astronomical orbital forcing in addition the magnetic records also distinguished two most anoxic periods during the lacustrine anoxic event 1 lae1 the sections of 1758 1761 m and 1769 1771 5 m which may suggest the two most active periods of surface productivity of the lake

structural style and its relation to hydrocarbon exploration in the songliao basin northeast china the songliao basin in northeast china is a mesozoic rift basin characterized by mesozoic and cenozoic hydrocarbon systems the songliao basin was initiated by southeast to northwest lithospheric extension during the late jurassic the extensional phase was dominated by two fault sets l shallow to moderately dipping normal faults and 2 steeply dipping transfer faults the extensional structures are characterized by half grabens a second short extensional tectonic overprinting phase occurred during the early qingshankou early albian 100 to 97 ma faults that occur in the quantou formation and the qingshankou formation are growth faults t2 faults which trend mostly nnw and occur predominantly at the sites of basement faults and structural bend zones located between sag and uplift and basement uplifts the basin broadly subsided during the denglouku quantou aptian 125 to 100 ma and the late qingshankou late albian 97 to 94 ma to yaojia nenjiang cenomanian to campanian 94 to 73 ma respectively positive inverted structures developed during the late cretaceous to the cenozoic in the songliao basin these are classified into two types positive inversion structures controlled by reactivation of early normal faults and inversion structures not controlled by earlier faults the major extensional structures exerted a range of controls on both sedimentation and deformation during the subsequent phases of basin evolution two thermotectonic rifting events during the late jurassic and early qingshankou play a major role in organic matter thermal evolution the timing of formation of structural traps in the basin matches that of hydrocarbon generation and migration structural traps formed during late jurassic early qingshankou and late cretaceous to paleocene 73 to 56 ma late jurassic organic rich source rock reached its peak oil generation from the time of deposition of member deng 3 4 of the denglouku formation 119 to 116 ma to that of member qing 1 of the qingshankou formation 100 to 97 ma qing 1 of the qingshankou formation and nen 1 of the nenjiang formation organic rich source rocks reached their peak oil generation from the time of deposition of the upper mingshui formation to that of the upper yi an formation and from the time of deposition of the taikang formation to that of deposition of the quarternary respectively

a new geodynamical thermal model of rift evolution with application to the dnieper donets basin ukraine abstract a model of the lithosphere incorporating both dynamic and thermal processes has been developed by solving a coupled system of differential equations governing stress and temperature in a 2 d block structured geophysical medium designed to study the roles of tectonic and geothermal factors in continental rift formation and evolution the model incorporates syn sedimentary and or erosional faulting of an upper crustal layer and allows the thermal regime of the lithosphere to be calculated through time the method has been applied to the formation and evolution of the northwest dnieper donets basin ddb along one regional profile controlled by seismic and other geophysical and subsurface data the results are compared with those published earlier for the same profile using different methods of modelling the rift and early post rift development of the region the final basement geometry at the end of the rifting stage predicted by the new model satisfactorily corresponds with geological data and is qualitatively similar to that predicted by the previously published models however the new results imply an important role for an active mechanism during rifting that generates greater mantle thinning than crustal thinning and elevated temperatures in the upper mantle beneath the rift

architecture and depositional sequences of tertiary fault block carbonate platforms an analysis from outcrop miocene gulf of suez and computer modelling abstract this study combines outcrop with seismic data and tectonostratigraphic modelling to characterise the stratigraphy of tertiary fault block carbonate platforms seismic sections from the middle east and southeast asia indicate that carbonate platforms commonly develop on fault blocks in the late syn rift to post rift stage of basin evolution they are characterised by retrogradational or drowning morphologies with deep water clastics evaporites sealing the platforms a new tectono stratigraphic modelling program simulates the development of carbonate platforms on domino style fault blocks and predicts a distinctive tectonic control on the evolving syn rift stratigraphy detailed field work from a three dimensionally exposed miocene syn rift platform from the gulf of suez gebel abu shaar egypt shows the existence of unconformity bound depositional sequences which are predicted by the program and are interpreted to have formed in response to fault block rotation the sequences are characterised by synchronous hangingwall subsidence and footwall uplift and erosion the seismic images the modelling and the outcrop study provide different levels of information on fault block platforms and their characteristic stratigraphy the scale of the modelling is of particular value as it provides a link between the seismic scale imaging and outcrop data

fault linkage patterns and their control on the formation of the petroleum systems of the erlian basin eastern china abstract fault linkage patterns in rift basins are very common while the process of fault linkage may be very short it changes sedimentation patterns before and after linkage and controls the development of half grabens the propagation and growth of boundary faults can be divided into a simple fault propagation pattern and a fault growth linkage pattern based on structural style sedimentation patterns and oil source correlations in the erlian basin three types of grabens and petroleum systems can be identified the abei graben is controlled by a single boundary fault and forms an independent petroleum system the saihantala graben is controlled by several linked faults which also has an independent petroleum system the wuliyasitai depression controlled by two boundary fault segments which results in two petroleum systems as not all half grabens develop one petroleum system they may therefore have two or more systems the relay ramps between fault segments before linkage are the locations of deposition of sands and conglomerates and consequently are the focus areas for stratigraphic lithologic trap exploration

numerical investigation of the hydromechanical response of a natural fracture during fluid injection using an efficient sequential coupling model hydraulic fracturing is a complicated hydromechanical coupled process especially in shale gas and deep geothermal reservoirs in which natural fractures exist due to the geological complexity caused by invisibility and the challenge and high cost in field investigations numerical modeling becomes an alternative in this paper an integrated numerical model is developed to investigate the hydromechanical behavior of a natural fracture during the fluid injection in the developed model the mechanical behavior of the fracture including fracture opening closure shear dilation and shear failure is described by proposed constitutive equations meanwhile the hydraulic process is simplified as the fluid flows through two parallel planes the coupled mechanical and hydraulic equations are sequentially formulated in an implicit schema by combining the finite different method and the finite volume method the advantage of this numerical schema is that the two coupled processes are solved separately and only one sub iteration is needed thus the solution is efficient and stable than that formulated in a monolithic coupling besides the implicit formulation of the flow equation makes it possible to set a relative large time step the developed model is verified through three numerical examples then it is used to investigate the hydromechanical behavior of a natural fracture during the fluid injection with a fictive reservoir sensitivity studies with variations in the stress state the fluid injection rate the fluid viscosity and the injection form are conducted the simulation results show that the mechanism in the far field is mainly dominated by shear dilation in contact condition whereas the mechanism near the injection could be mixed shear tension in either the contact or the separation conditions with the increase in the shear stress and the injection length decrease in the injection rate and the fluid viscosity the fracture state near the injection will change from separation to contact the injection pressure will decline below the primary normal stress and the dominated mechanism is shear dilation the findings in this study give a better understanding of the mechanical mechanism and the pressure response of a natural fracture during the fluid injection

cross section restoration and one dimensional basin modeling of the central subbasin in the southern kunsan basin yellow sea the petroleum system of the kunsan basin in the northern south yellow sea basin is not well known compared to other continental rift basins in the yellow sea despite its substantial hydrocarbon potential restoration of two depth converted seismic profiles across the central subbasin in the southern kunsan basin shows that extension was interrupted by inversions in the late oligocene middle miocene that created anticlinal structures one dimensional basin modeling of the iih 1xa well suggests that hydrocarbon expulsion in the northeastern margin of the depocenter of the central subbasin peaked in the early oligocene predating the inversions hydrocarbon generation at the dummy well location in the depocenter of the subbasin began in the late paleocene most source rocks in the depocenter passed the main expulsion phase except for the shallowest source rocks hydrocarbons generated from the depocenter are likely to have migrated southward toward the anticlinal structure and faults away from the traps along the northern and northeastern margins of the depocenter because the basin fill strata are dipping north faulting that continued during the rift phase middle miocene of the subbasin probably acted as conduits for the escape of hydrocarbons thus the anticlinal structure and associated faults to the south of the dummy well may trap hydrocarbons that have been charged from the shallow source rocks in the depocenter since the middle miocene

new insights on the green river petroleum system in the uinta basin from hydrous pyrolysis experiments the tertiary green river petroleum system in the uinta basin generated about 500 million bbl of recoverable high pour point paraffinic crude oil from lacustrine source rocks a prolific complex of marginal and open lacustrine source rocks dominated by carbonate oil shales containing up to 60 wt type i kerogen occur within distinct stratigraphic units in the basin petroleum generation is interpreted to originate from source pods in the basal green river formation buried to depths greater than 3000 m along the steeply dipping northern margin of the basin producing fields in the altamont bluebell trend have elevated pore fluid pressures approaching 80 of lithostatic pressure and are completed in strata where open fractures provide permeability active hydrocarbon generation is one explanation for the origin of the overpressured reservoirs in this study experiments were undertaken to examine the mechanisms of hydrocarbon generation and accumulation in the uinta basin we combined analyses of representative source rocks from the entire green river stratigraphic section with detailed laboratory simulation experiments using both open and closed system pyrolysis this information provides new insights on lacustrine source rock lithofacies gas oil source rock correlations hydrocarbon generation kinetics and basin modeling the results show that the basal green river formation contains a unique type i source facies responsible for generation of paraffinic crude oils the classic type i oil shales in the upper green river formation correlate well with low maturity aromatic asphaltic samples we determined kinetic parameters for the source rocks and used them to develop basin models for hydrocarbon generation the models show that hydrous pyrolysis kinetic parameters are more consistent with the natural data in terms of predicted timing and extent of oil generation as compared to models using rock eval kinetics begin page 1334

hydrocarbon charging and accumulation history in the niudong buried hill field in the baxian depression eastern china abstract the niudong buried hill field which lies in the baxian depression of the bohai bay basin is the deepest oil gas accumulation in eastern china its precambrian dolomite reservoir occurs at burial depths of 5860 m 6027 m this paper attempts to document the hydrocarbon charging and accumulation history in this field which could greatly enhance the understanding of the mechanisms for the formation of deep hydrocarbon accumulations our previous study of oil trapped in fluid inclusions has demonstrated that the ratio parameters of the fluorescence spectral intensities at 425 nm and 433 nm q 425 433 ratio and at 419 nm and 429 nm q 419 429 ratio can be more effective for revealing hydrocarbon charging history than the previously used fluorescence parameters such as lambda max and red green quotient as well as fluorescence colors the hydrocarbon charging and accumulation history in the niudong buried hill field was studied with an integrated approach involving the application of these two spectral parameters of petroleum inclusion fluorescence as well as utilization of other data including homogenization temperatures of aqueous inclusions coeval with petroleum inclusions and cross cutting relationships of cements and oil veins in pores and fractures the results indicate that the dolomite reservoir in the niudong buried hill field experienced three episodes of hydrocarbon charging in the first two episodes between 38 5ma and 25ma the low mature and mature oils which were derived from source rocks in the sha 4 member of the eocene shahejie formation migrated into the reservoir but part of them leaked out due to normal faulting at the updip margin of the buried hill these early charged oils were preserved mainly in small pores in micritic dolomites by oil wettability and capillary pressure in the neogene the basin subsided as a whole and local faults at the updip margin became inactive and played a sealing role by approximately 13ma the source rocks became highly mature and the generated hydrocarbons then migrated into the reservoir and accumulated therefore the last charging is the most important for hydrocarbon accumulation in the niudong buried hill field

immature oil and condensate modification of hydrocarbon generation model for terrestrial organic matter petroleum has been found in canadian frontier basins in reservoirs which have undergone low levels of thermal alteration vitrinite reflectance 0 6 ro paraffin indices stable carbon and hydrogen isotope contents pristane to nc17 ratios and diterpenoid biologic markers have been used to assess the level of maturity of the hydrocarbons in the reservoir independently of the level of maturity of the reservoir itself and of the surrounding shale units in the tertiary of the beaufort mackenzie basin naphthenic oils and condensates have been generated from terrestrially derived organic matter in source rocks juxtaposed with the reservoir at reflectance levels of 0 4 to 0 6 ro however condensates discovered in reservoirs which are th rmally immature on the labrador shelf have undergone extensive vertical migration and can be classed as conventional mature to overmature condensates hydrocarbons discovered in the lower cretaceous of the beaufort mackenzie basin and also those of the scotian shelf are more or less in place in that they are at a level of thermal alteration about equivalent to that of the reservoirs in which they are trapped the source for the early oils and condensates is considered to be resinite occurring dispersed in coal fragments the proportion of resinite liptinite and vitrinite in the organic matter of terrestrial source rocks strongly controls both the level of thermal alteration necessary for the section to function as an effective source rock and the ultimate product gas oil or condensate which will be generated

airborne scanning lidar measurement of ocean waves abstract a scanning lidar system provides high resolution three dimensional measurements of ocean wave displacement the airborne operation further enhances the speed of data acquisition these properties allow rapid characterization of the ocean wave environment in addition to active ranging the scanning optics can obtain passive measurements of surface emissivity yielding a digital image of surface brightness in real time processed into a binary image these measurements can provide information on the average statistics and the spatial distribution of breaking waves technical specifications of the system and examples of application are presented published by elsevier science inc

combined escape tectonics and subduction rollback back arc extension a model for the evolution of tertiary rift basins in thailand malaysia and laos the tertiary rift basins of thailand and adjacent countries show considerable variability in the timing of rift initiation termination the timing and magnitude of thermal subsidence and the timing and intensity of inversion episodes the rift basins developed on continental blocks that were extruded southeastwards hence their development must be tied into himalayan extrusion tectonics current tectonic models propose that the tertiary basins opened up as pull apart basins associated with strike slip faults published geochronology of strike slip fault zone rocks mapping of fault patterns in the tertiary basins and mapped releasing restraining bend geometries all indicate that in thailand major sinistral strike slip motion ceased at about 30 ma prior to the formation of most rift basins the thailand the effects of later dextral slip were minor and probably a result of reactivation during episodes of inversion during nw se to ne sw himalayan compression dextral slip was not responsible for opening most of the rift basins in thailand an alternative mechanism to open the rift basins is subduction rollback of the indian plate to the west of thailand it is proposed that subuction rollback can help explain some of the characteristics of the rift basins such as non uniform lithospheric extension deep sag basins and the diachronous onset and termination of rifting

an observation of the directional wave spectrum evolution from shoreline to fully developed abstract the surface contour radar scr is a 36 ghz computer controlled airborne system which produces ocean directional wave spectra with much higher angular resolution than pitch and roll buoys scr observations of the evolution of the fetch limited directional wave spectrum are presented which indicate the existence of a fully developed sea state the jonswap wave growth model for wave energy and frequency was in best agreement with the scr measurements the model of donelan et al correctly predicted the propagation direction of waves in the asymmetrical fetch situation nearshore the donelan et al parameterization is generalized to permit other growth algorithms to predict the correct direction of propagation in asymmetrical fetch situations

petroleum systems in the offshore xihu basin on the continental shelf of the east china sea xihu basin is one of the cenozoic sedimentary basins within the continental shelf of the east china sea within which eight oil and gas fields and four hydrocarbon bearing structures have been found our systematic analysis of potential petroleum systems in the basin has identified the eocene pinghu formation as the most important source rock in the basin the eocene pinghu formation consists of mudstone and coal deposited in an embayment and tidal flat environment and is characterized as containing type iii kerogen the pinghu formation is mature and at the present time is within the oil and wet gas windows with determined vitrinite reflectance values in the range of 0 55 2 2 measured vitrinite reflectance rom modeling results suggest that the main stage of hydrocarbon expulsion occurred during the miocene the main reservoir consists of fine grained sandstones of the huagang and pinghu formations deposited within shallow lacustrine and estuarine environments the measured porosity from core samples of reservoir rock ranges from 10 to 35 whereas permeability values range from 1 to 4000 md both porosity and permeability decrease with depth the mudstones of the upper huagang and longjing formations also occur as regional seals which developed overpressure zones as determined by two way sonic transit times the overburden includes all the oligocene miocene pliocene and quaternary strata the hydrocarbon traps in the basin are mainly structural traps including faulted blocks faulted structural noses and anticlines most traps were developed at the ends of the eocene or oligocene hydrocarbons produced from the xihu basin are predominantly natural gases with minor amounts of crude oil the crude oil in the basin is characterized by a low density low sulfur low wax low vanadium nickel ratio a low resin and asphaltene content and a high proportion of saturated hydrocarbons the natural gas in the basin is composed predominantly of methane with an average c1 c1 5 ratio of 0 89 and a c1 c2 5 ratio of 8 6 two petroleum systems have been identified in the basin the known pinghu huagang and the hypothetical huagang huagang systems the pinghu huagang is the major petroleum system and most important for oil and natural gas exploration in the basin

formation and evolution of nonmarine petroleum in songliao basin china in large lake basins source rocks containing sapropelic kerogen have a high transformation ratio and a high potential for petroleum and they offer the material basis for the formation of a large nonmarine oil field on the basis of geologic and geochemical data and the results of thermal simulation of kerogen it is confirmed that the maturation sequence of kerogen is type i type ii and type iii

characterisation of oil and potential source rocks in the northeastern song hong basin vietnam indications of a lacustrine coal sourced petroleum system oil discovered in the b10 stb 1x well in the northeastern song hong basin vietnam has typical lacustrine coaly geochemical features indicating the existence of a principally lacustrine sourced petroleum system with minor contributions from a coal source the presence of lacustrine source rocks in the basin is indicated by distinct high amplitude seismic reflectors in undrilled half grabens and outcrops of oligocene immature mudstones and humic coals at dong ho and on bach long vi island the mudstones from dong ho generally have a toc content of 8 17 wt and hi values 500 mg hc g toc the organic matter is principally composed of fluorescing amorphous organic matter and liptodetrinite alginite with botryococcus morphology is present the organic matter corresponds to type i kerogen the bach long vi island mudstones contain 2 7 wt toc and have hi values from 200 700 mg hc g toc the organic matter is largely similar to that in the dong ho mudstones but in addition may contain some marine organic material the b10 stb 1x oil shows features common to both the dong ho and bach long vi island mudstones but was probably principally generated from a source similar to the dong ho mudstones with contributions from higher land plant organic matter a prominent activation energy peak dominates the activation energy distributions of the mudstones and upon artificial maturation hydrous pyrolysis the mudstones show extensive hydrocarbon generation over a narrow temperature range hydrocarbon expulsion has been estimated to occur at a vitrinite reflectance of 0 75 ro the source of the b10 stb 1x oil may be located in the thuy nguyen graben and maturity modelling shows that the lacustrine mudstones will be thermally mature in this graben

petroleum geochemistry and depositional setting of lacustrine source rocks abstract lacustrine sequences are increasingly being recognised as hosts for commercial reserves of petroleum petroleum source rocks in lacustrine sequences have organic carbon contents ranging from 20 and kerogen types range from type i to type iii the organic matter can be of land plant algal or bacterial origin most undegraded lacustrine oils are extremely paraffinic and waxy but a few are asphaltic and rich in sulphur the crude oils and source rocks contain a wide diversity of biological marker compounds reflecting different source inputs the diversity of chemistries displayed by lacustrine source rocks and crude oils reflect the wide variety of organic source materials and depositional conditions operative in lakes lacustrine sequences preserved in the geological record represent sediments deposited in fluvial lakes on humid flood plains and tectonic lakes in humid semi arid and arid environments preservation of organic matter in lakes is dependent on the formation of anoxic or micro oxic bottom waters this is favoured by stratification of lake waters brought about by temperature and salinity contrasts organic material preserved in oligotrophic lakes is largely of land plant origin which has been extensively modified by bacteria under mildly oxidizing conditions and supplemented by the bacterial remains source rocks of this type are found in 1 fluvial lacustrine settings e g jurassic of eromanga basin australia and 2 the oligotrophic phase of larger tectonic lakes e g early stages of green river formation uinta basin usa as these freshwater lakes become productive algal remains are contributed to the sediment and anoxic bottom waters can become more firmly established the green algae pediastrum and botryococcus appear to be particularly important although land plant detritus is still significant e g cretaceous source rocks songliao basin china saline lakes conditions tend to restrict the diversity of the source biota although preservation may be enhanced through anoxia brought about by salinity stratification and inhibition of bacterial decay e g later stages green river formation uinta basin usa sulphate rich and hypersaline lacustrine systems result in the formation of sulphur rich sources and oils e g jianghan basin china because of the diversity of organic matter types maturation criteria for hydrocarbon generation in lacustrine sequences also vary however in most cases higher maturation levels are required for significant hydrocarbon generation at present it is uncertain the extent to which algal and bacterial organic matter contribute to the source for the waxy hydrocarbons which are characteristic of lacustrine oils organic rich rocks formed in large freshwater and saline lakes are the most productive type of lacustrine source rock although sources formed in lakes of flood plains and deltas are also widespread

high resolution geochemical analysis of organic matter accumulation in the qingshankou formation upper cretaceous songliao basin ne china abstract in the well known continental songliao basin the oil shale successions of the cretaceous qingshankou formation are excellent source rocks for oil the oil shale layers with high toc total organic carbon contents developed at the bottom of the formation they are divided into the lower oil shale toc up to 18 3 and the upper oil shale layer toc up to 14 4 the oil shale layers and accompanying mudstones are investigated by high resolution analyses of drill cores by pyrolysis organic petrology organic and inorganic geochemistry the results demonstrate the predominance of type i kerogen derived from algal microbial mats i e lamalginite however increased proportions of plant derived organic matter are indicated by rock eval parameters and the presence of vitrinite in the upper oil shale as evidenced from lower concentrations of hopanes higher sinking rates of organic matter om are suggested to have been responsible for a lower extent of microbial degradation during accumulation of the lower oil shale unit the environmental conditions are characterized by anoxic saline bottom water overlain by an extended zone of freshwater favorable for om production and preservation under these preconditions oil shale thickness and quality are governed by primary productivity related to accommodation space and nutrient supply redox conditions within the water column are the key factor controlling organic matter preservation

patterns of displacement along large normal faults implications for basin evolution and fault propagation based on examples from east africa seismic reflection data across six boundary faults from east africa have revealed information about the way boundary faults develop with respect to the synkinematic basin fill previous models of basin fill assume that lateral fault propagation and deposition occur simultaneously which gives rise to along axis onlap of the basin fill onto the prerift basement propagating basin model seismic reflection data from boundary faults in east africa show only rare evidence for along axis broadening of the basins instead the basin margins appear to be fixed from a very early stage in the basin history nonpropagating basin model depocenters shift not by gradual lateral propagation but by abrupt changes in location such observations indicate that boundary fault propagation to near maximum length occurs rapidly during the very early stages of rifting probably by linkage of numerous small faults displacement then builds following the b value earthquake model along the fault during basin development out of phase with the main propagation phase mature fault systems may have experienced several phases of jumps in fault length or the location of fault activity major boundary faults exhibit three basic patterns of evolution these patterns of evolution can have many variants and include 1 simple displacement where maximum displacement is approximately at the center of the fault and decreases gradually toward the fault tips 2 variable along strike displacement that incorporates linkage of in line or en echelon relatively large displacement faults of similar age leaving transverse anticlines and synclines and 3 asymmetric propagation where one tip of a fault remains more or less fixed while the other tip propagates a relatively long distance asymmetric propagation can occur smoothly and gradually or alternatively there can be a jump in the location of the fault and a new fault of different age can form along strike from the older fault eventually the new fault propagates and links with the older fault segment reactivating the older fault to some extent addition ally long lived faults may be composites of fault types 1 3

anomalous subsidence on the rifted volcanic margin of pakistan no influence from deccan plume abstract the role of hotter than ambient plume mantle in the formation of a rifted volcanic margin in the northern arabian sea is investigated using subsidence analysis of a drill site located on the seismically defined somnath volcanic ridge the ridge has experienced 4 km of subsidence since 65 ma and lies within oceanic lithosphere we estimate crustal thickness to be 9 5 11 5 km curiously 600 c especially considering the rapid northward drift of india relative to the deccan reunion hotspot we suggest that this reflects very slow lithospheric growth possibly caused by vigorous asthenospheric convection lasting 28 m y and induced by the steep continent ocean boundary post rift slow subsidence is also recognized on volcanic margins in the ne atlantic and se newfoundland and cannot be used as a unique indicator of plume mantle involvement in continental break up

the floating astronomical time scale for the terrestrial late cretaceous qingshankou formation from the songliao basin of northeast china and its stratigraphic and paleoclimate implications abstract the upper cretaceous qingshankou formation k 2 qn in the songliao basin slb of northeast china consists of up to 550 m thick lacustrine mudstone and shale that constitute one of the most important source rocks of the daqing oil field a high resolution cyclostratigraphic analysis of the natural gamma ray logging from 10 wells of the qingshankou formation k 2 qn reveals orbital cycles of precession 20 ka obliquity 40 ka and eccentricity 100 ka and 405 ka providing strong evidence for astronomically driven climate changes in the late cretaceous terrestrial environments floating astronomical time scales ats are established for all sections which demonstrate variable durations of k 2 qn across the basin 1 09 ma 5 20 ma and strong diachroneity of the lacustrine strata four periods of high depositional rates can be identified in the central parts of the basin possibly recording deposition during times of sustained wet climate and high chemical weathering an ats established from well m206 in the central depression zone of the basin where the most complete and stable milankovitch cycles are present suggests that the maximum duration of the k 2 qn is 5 20 ma from 94 27 ma to 89 07 ma late cenomanian to early coniacian the lacustrine anoxic event 1 lae1 at the cenomanian turonian boundary lasted 210 310 ka during which the most prolific petroleum source rocks in slb were deposited the onset 94 21 94 18 ma and duration 210 310 ka of lae1 in slb are comparable to those of the oceanic anoxic event 2 oae2 onset at 94 21 ma and duration of 320 900 ka suggesting that the same trigger mechanism such as increased atmospheric co 2 from large scale igneous activity may have initiated high primary productivity and organic carbon burial in both marine and terrestrial systems

geochemistry of natural gases in deep strata of the songliao basin ne china chemical composition and stable carbon isotopic studies were undertaken for 27 gas samples from deep strata of the xujiaweizi depression in the songliao basin to investigate their origin gas molecular and carbon isotopic compositions show great variety methane is the main component for all studied samples and its content ranges from 57 4 to 98 2 with an average of 90 1 gas wetness ranges from 0 8 to 16 7 with an average of 2 7 the main non hydrocarbon gases are carbon dioxide and nitrogen with an average of 4 0 and 3 2 respectively carbon isotope data suggest that these deep strata gases are mainly coal type gases mixed with minor amounts of associated oil type gases coal type gases are characterized by heavier carbon isotopic values and drier chemical compositions these gases were generated from the lower cretaceous shahezi formation coals interbedded shales with type iii kerogen during the postmature stage of hydrocarbon generation oil type gases are characterized by lighter carbon isotope and higher wetness which were generated from the lower cretaceous shales with type ii kerogen in the shallow strata during the early mature stage of hydrocarbon generation mixing of two different gases causes unusual carbon isotopic distribution patterns with lighter isotopic values in higher numbered carbons in most gases the discovery of coal type gases in the songliao basin provides new prospects for the exploration in this region

comparative sequence stratigraphy of low latitude versus high latitude lacustrine rift basins seismic data examples from the east african and baikal rifts abstract lakes baikal malawi and tanganyika are the world s three largest rift valley lakes and are the classic modern examples of lacustrine rift basins all the rift lakes are segmented into half graben basins and seismic reflection datasets reveal how this segmentation controls the filling of the rift basins through time in the early stages of rifting basins are fed primarily by flexural margin and axial margin drainage systems at the climax of syn rift sedimentation however when the basins are deeply subsided almost all the margins are walled off by rift shoulder uplifts and sediment flux into the basins is concentrated at accommodation zone and axial margin river deltas flexural margin unconformities are commonplace in the tropical lakes but less so in high latitude lake baikal lake levels are extremely dynamic in the tropical lakes and in low latitude systems in general because of the predominance of evaporation in the hydrologic cycle in those systems evaporation is minimized in relation to inflow in the high latitude lake baikal and in most high latitude systems and consequently major sequence boundaries tend to be tectonically controlled in that type of system the acoustic stratigraphies of the tropical lakes are dominated by high frequency and high amplitude lake level shifts whereas in high latitude lake baikal stratigraphic cycles are dominated by tectonism and sediment supply variations

airborne remote sensing of breaking waves abstract airborne scanning laser ranging provides rapid measurements of the ocean wave topography in addition to active ranging the scanning optics can obtain passive measurements of the surface emissivity yielding a digital image of the surface brightness the brightness data contain information on the statistics and spatial distribution of whitecaps combining active measurements of the 3d surface topography and passive brightness data the phase distribution of breaking events along a wave profile can be examined from the phase distribution analysis it is found that in deep water the whitecap coverage in the windward phase is slightly higher than that in the leeward phase 51 17 vs 49 14 and more whitecaps are found on the crests than in the troughs 57 13 vs 44 16 such quantitative information on wave breaking and whitecap coverage is important to remote sensing applications and air sea interaction studies

lacustrine basin unconventional resource plays key differences abstract there has been a revival in hydrocarbon source rock characterization and development associated with growing interest in unconventional resources where these fine grained organic rich rocks act as both source and reservoir to date the exploration focus on shale reservoirs has been largely on marine systems lacustrine source rocks for conventional resources are geographically important dominating regions such as china indonesia and brazil s resource base however they have been generally untested for unconventional resources there are a number of key differences in the nature of these hydrocarbon systems that should be considered when assessing whether lacustrine systems may represent future unconventional opportunities in areas where the conventional resource base is dominated by lacustrine sourced oil among the key differences between these depositional systems is the greater sensitivity to high frequency climatic variability within lacustrine systems lacustrine systems are highly sensitive to changes in the balance between precipitation and evaporation which may lead to rapid changes in lake level potentially exceeding 600 m these changes in depositional conditions are geologically rapid and may occur over periods of thousands of years such changes can reduce the areal extent of potentially thick source rock intervals to only those portions of a basin where a permanent deep lake was present thus the core unconventional target area may be geographically limited compared with their marine counterpart although potentially areally limited a review of many lacustrine source rocks suggests that their thicknesses are often significantly greater than marine source rocks an examination of the more distal portions of lacustrine systems where better source rock potential is present reveals that there is generally limited connectivity between source and conventional reservoir in these settings such as the wind river basin waltman shale the hydrocarbons remain trapped within the shales potentially leading to over pressured hydrocarbon charged systems such conditions suggest that although areally limited viable unconventional targets may exist if suitable reservoir conditions are present finally the character of the oils produced is different in these settings with lacustrine oils being waxy and displaying different hydrocarbon generation and cracking kinetics high wax oils display distinct flow characteristics being more viscous and may offer different production challenges than their non waxy marine equivalents additionally differences in their cracking kinetics may indicate that the timing of gas generation for shale gas plays may differ significantly from marine systems

countermeasures to treat collapse during the construction of road tunnel in fault zone a case study from the yezhuping tunnel in south qinling china to ensure the safety of the tunnel construction it is very important to take the appropriate treatment measures after the collapse happened especially the tunnel goes through the fault fracture zone this paper sets forth the process of the collapse that occurred in the yezhuping tunnel affected by the fault fracture zone and introduces the treatment for the collapse the deformation characteristics of the surrounding rock are analyzed according to the monitoring results based on the research regarding the effect of the fault on the tunnel by using the general hoek brown failure criterion and the field monitoring results it is shown that the fault is the main reason for the collapse it induces the attenuation of the young modulus and the compressive strength and the enlargement of the plastic zone the research results have some reference significance for similar projects

characteristics of seismic disasters and aseismic measures of tunnels in wenchuan earthquake over the past few years accompanied by big and frequent earthquakes more attention was paid to the tunnel earthquake resistance to reduce tunnel seismic damage and explore the reasonable aseismic measures the tunnel earthquake disaster investigation was employed to analyze and summarize the tunnel seismic damage on the basis of wenchuan earthquake fifty two tunnels near the epicenter of sichuan province were investigated only 7 tunnels did not show structure damage 6 tunnels suffered the most serious damage and the rest appeared damage to various extents it indicates that most serious seismic damage happens to fault fracture zone followed by entrance and common section of the tunnel additionally the results display that the typical seismic damage of tunnels is lining cracking collapsing dislocation construction joints cracking and uplifting of invert and usually lining cracking and collapsing account for a larger proportion therefore the tunnel aseismic design should emphasize the fault fracture zone and tunnel entrance tunnel design should adopt the composite lining structure with shock absorber and whole chain alternative grouting to prevent the lining cracking and collapsing in the seismic fortification zone

airborne measurements of the wavenumber spectra of ocean surface waves part i spectral slope and dimensionless spectral coefficient an airborne scanning lidar system acquires 3d spatial topography of ocean surface waves from the spatial data wavenumber spectra are computed directly the spectral analyses of two distinctively different wave fields are presented the first one is a quasi steady wave field under active wind generation and the second one is a decaying wave field following a slackening of the wind field subtle differences in different representations of the one dimensional spectrum omnidirectional marginal and traverse are illustrated the spectral properties in terms of the dimensionless spectral coefficient and spectral slope in the equilibrium range are investigated using the wavenumber spectra directly computed from the 3d topography of the ocean surface the results are in excellent agreement with existing data the rapid data acquisition afforded by an airborne system provides an enhanced capability for studying the spatial variation of a wave field with minimal temporal changes in the environmental forcing conditions the data of the 3d surface topography are also ideal for the quantitative investigation of the directional properties of a random wave field

directional wave spectra measured with the surface contour radar abstract the surface contour radar is a 36 ghz computer controlled airborne radar which generates a false color coded elevation map of the sea surface below the aircraft in real time and can routinely produce ocean directional wave spectra with post flight data processing which has much higher angular resolution than pitch and roll buoys when compared with waveriders and the xerb and edeco pitch and roll buoys there is good agreement among the nondirectional spectra there is also good agreement among the angles associated with a1 b1 and a2 b2 fourier coefficients of the spreading function for xerb endeco and the surface contour radar there are indications that the pitch and roll buoys in this study may have calibration problems with the magnitudes of the fourier coefficients of the spreading function and that the radar system determines the fourier coefficients with significantly less noise and bias the high spatial resolution and rapid mapping capability over extensive areas make the surface

investigating the spatial distribution of water levels in the mackenzie delta using airborne lidar airborne light detection and ranging lidar data were used to map water level wl and hydraulic gradients h x in the mackenzie delta the lidar wl data were validated against eight independent hydrometric gauge measurements and demonstrated mean offsets from 0 22 to 0 04 m 0 1 m was observed at a channel constriction entering a meander bend suggesting a localized modification of the channel hydraulics furthermore water levels in the anabranch channels of the peel river were almost 1 m higher than in middle channel of the mackenzie river this suggests i the channels are elevated and have shallower bank heights in this part of the delta leading to increased cross delta and along channel hydraulic gradients and or ii a proportion of the peel river flow is lost to middle channel due to drainage across the delta through anastamosing channels this study has demonstrated that airborne lidar data contain valuable information describing arctic river delta water surface and hydraulic attributes that would be challenging to acquire by other means copyright 2011 john wiley sons ltd

comparison of surface slip and focal mechanism slip data along normal faults an example from the eastern gulf of corinth greece abstract focal mechanism and surface slip data are used to investigate whether kinematics are similar at depth and at the surface along an active normal fault in the gulf of corinth greece we present a new database of slip data from the lateral termination of the south alkyonides fault segment safs and the en echelon stepover between it and an adjacent fault and use published data on surface slip and focal mechanism data pertaining to slip at depth during the 1981 alkyonides earthquake sequence the focal mechanisms exhibit similar fault plane orientations and kinematics to those measured at the surface within the stepover both data sets show that contemporaneous c n s and c e w extension is being accommodated by c e w and c n s oriented normal faults and the overall deformation is distributed oblate vertical flattening the deviation of the surface slip direction from 350 increases with distance from the centre of the safs the deviation of the focal mechanism t axes from 350 fit well with the surface data implying that the coseismic slip on the safs at depths of 7 10 km exhibits a similar kinematic pattern as that observed at the surface our results imply that it is critical to know the along strike position of data on a fault if either focal mechanisms or surface slip are to be used to infer regional strain and stress trajectories

productivity and paleoclimatic controls on source rock character in the aman trough north central sumatra indonesia abstract the central sumatra basin csb is a prolific oil producing basin in indonesia where a single source rock has been identified the brown shale formation of the paleogene pematang group despite the presence of a single source rock the oils in the central sumatra basin and particularly in the aman trough exhibit variable molecular and isotopic compositions previously described as reflective of lateral facies variations within the source rock analyses by gas chromatography gc gas chromatography mass spectrometry gc ms and gas chromatography isotope ratio mass spectrometry gc irms of 15 oil samples from the aman trough allowed identification of vertical and lateral facies changes within the brown shale formation as well as paleoproductivity and paleoclimatic changes that took place during deposition of this prolific source rock the molecular and isotopic data indicate the source rock for these oils was deposited in a fresh to brackish water stratified lake in which co 2 limiting conditions prevailed compound specific isotopic data also indicate that changes in paleoclimatic conditions possibly associated with the eocene oligocene paleoclimatic transition had an effect on the geochemical composition of the source rock in the aman trough

floodplain friction parameterization in two dimensional river flood models using vegetation heights derived from airborne scanning laser altimetry two dimensional 2 d hydraulic models are currently at the forefront of research into river flood inundation prediction airborne scanning laser altimetry is an important new data source that can provide such models with spatially distributed floodplain topography together with vegetation heights for parameterization of model friction the paper investigates how vegetation height data can be used to realize the currently unexploited potential of 2 d flood models to specify a friction factor at each node of the finite element model mesh the only vegetation attribute required in the estimation of floodplain node friction factors is vegetation height different sets of flow resistance equations are used to model channel sediment short vegetation and tall and intermediate vegetation the scheme was tested in a modelling study of a flood event that occurred on the river severn uk in october 1998 a synthetic aperture radar image acquired during the flood provided an observed flood extent against which to validate the predicted extent the modelled flood extent using variable friction was found to agree with the observed extent almost everywhere within the model domain the variable friction model has the considerable advantage that it makes unnecessary the unphysical fitting of floodplain and channel friction factors required in the traditional approach to model calibration copyright 2003 john wiley sons ltd

30 norhopanes their occurrence in sediments and crude oils abstract sediments and crude oils have been analysed using gc ms techniques and shown to contain two homologous series of hopanes namely 30 nor 17 h hopanes and 25 30 bisnor 17 h hopanes as well as the common 17 h hopanes homologues c28 to c34 of the 30 nor 17 h hopane series have been identified in crude oils associated with carbonate source rocks the abundances of these hopanes relative to the 17 h hopanes in the soluble organic matter from carbonate sediments has been shown to depend upon sample maturity the more mature samples having higher relative abundances of these norhopanes a comparison of the relative abundances of the norhopanes in the soluble organic matter of sediments and in the hydrocarbon fraction released when the extracted sediments were pyrolysed showed that the 30 nor 17 h hopanes were more abundant in the pyrolysis product these observations indicate that the proportion of norhopanes relative to normal 17 h hopanes in bound form in the kerogen is greater than that present in the soluble form and so kerogen cracking proceeds with increased maturity of the sediments and a relative enrichment of these norhopanes occurs in the soluble fraction the series of 25 30 bisnor 17 h hopanes has been identified in a severely biodegraded crude oil from a putative carbonate source this observation together with the reported occurrence of enriched 25 norhopanes in severely biodegraded crude oils suggests that 25 30 bisnor 17 h hopanes may be biomarkers for severely biodegraded crude oils from carbonate rich source rocks

lake type controls on petroleum source rock potential in nonmarine basins based on numerous empirical observations of lacustrine basin strata we propose a three fold classification of lacustrine facies associations that accounts for the most important features of lacustrine petroleum source rocks and provides a predictive framework for exploration in nonmarine basins where lacustrine facies are incompletely delineated 1 the fluvial lacustrine facies association is characterized by freshwater lacustrine mudstones interbedded with fluvial deltaic deposits commonly including coal shoreline progradation dominates basin fill resulting in the stacking of indistinctly expressed cycles up to 10 m thick in map view the deposits may be regionally widespread but laterally discontinuous and contain strong facies contrasts transported terrestrial organic matter contributes to mixed type i iii kerogens that generate waxy oil type i kerogen is hydrogen rich and oil prone type iii kerogen is hydrogen poor and mainly gas prone the luman tongue of the green river formation wyoming and the honyanchi formation junggar basin china provide examples of this facies association which is also present in the songliao basin of northeastern china the central sumatra basin and the cretaceous doba doseo basins in west central africa 2 the fluctuating profundal facies association represents a combination of progradational and aggradational basin fill and includes some of the world s richest source rocks deposits are regionally extensive in map view having relatively homogenous source facies containing oil prone type i kerogen examples include the laney member of the green river formation wyoming the lucaogou formation junggar basin china the bucomazi formation offshore west africa and the lagoa feia formation campos basin brazil 3 the evaporative facies association represents dominantly aggradational fill related to desiccation cycles in saline to hypersaline lakes and may include evaporite and eolianite deposits sublittoral organic rich mudstone facies are relatively thin but may be begin page 1034 quite rich and widespread the highest organic enrichment coincides with the deepest lake stages low input of land plant organic matter results in minimal lateral contrasts in organic content in some cases a distinctive type i s sulfur rich kerogen may generate oil at thermal maturities as low as 0 45 vitrinite reflectance equivalent examples include the wilkins peak member of the green river formation wyoming the jingjingzigou formation junggar basin china the jianghan and qaidam basins china and the blanca lila formation argentina

extensional fault related folding northwestern red sea egypt the duwi and hamadat areas on the northwestern margin of the red sea rift system exhibit superb outcrop examples of kilometric scale extensional fault related folds in this area the nakheil and hamadat faults of the rift border fault system consist of a series of wnw and nw trending segments that link through breached relay ramps the fault hanging walls are characterised by a series of offset synclines with non linear axial traces sub parallel to the faults the synclines are doubly plunging and in the immediate hanging wall to the normal faults the strata dip sub parallel to the fault these folds result from along strike displacement variations on the individual fault segments together with extension related fault propagation folding as the faults propagated upwards through a highly anisotropic pre rift sedimentary section in the duwi area the axial traces of the synclines are offset and bend in the regions of relay ramps in the hamadat area the synclines associated with individual fault segments are separated by transverse hanging wall anticlines that formed where segment linkage occurred numerical simulations of extension related fault propagation folding using a trishear model produce geometries that closely match those of the duwi and hamadat folds the dimensions of these hanging wall synclines and their relationships to fault displacement variations indicate that they are formed by extensional fault propagation folding rather than by frictional drag along the fault surface

airborne remote sensing applications to coastal wave research airborne sensors provide effective coverage of a broad region and are suitable for large scale experiments in this paper two scanning sensors that use the direct ranging technique to measure surface wave displacement are described on a nasa p 3 aircraft the sensors can complete one run across a 100 km continental shelf in 17 min a case study is presented using radar measured two dimensional surface topography to derive wave damping due to bottom friction the results are in good agreement with an analytical model based on a quadratic formulation of bottom shear stress this study demonstrates that remote sensing measurements can be used for rapid characterization of surface waves on the continental shelf and in coastal regions examples illustrated in this paper include the derivation of wavenumber spectra and estimation of the dissipation rate of shoaling ocean swell

tertiary deltaic and lacustrine organic facies comparison of biomarker and kerogen distributions abstract biological marker and kerogen compositional data in tertiary deltaic and lacustrine settings were compared and contrasted the two settings are represented by a coals and organic carbon rich shales in a ick deltaic sequence from the far east constituting three distinct organic facies and b humic coals and spropelic oil shales in a restricted intermontane freshwater lacustrine sequence from western montana u s a constituting two distinct organic facies wedistinguish the organic facies in each depositional setting by systematic differences in gross compound class distributions kerogen and infrared spectral characteristics molecular character of pyrolyzates sterane carbon number distribution and sterane hopane ratios the kerogens of the three deltaic organic facies are characterized by varying quantities of vitrinite resinite sporinite cutinite and fluorescent amorphinite triterpane distributions reveal numerous terrigenous compounds including oleanane oleanenes and unidentified c 30 presumably resin derived components the two organic facies of the freshwater lacustrine setting are distinguishedased upon either a vitrinite or an alganite fluorescent amorphinite predominance in the kerogen numerous characteristics facies related markers are also present including dehydroabietane land plant resins and 4 methylsteranes perhaps from freshwater dinoflagellate input the available molecular and petrographic data are evaluated and characteristics are proposed for distinguishing five organic facies of these two depositional settings the successful simultaneous use of molecular geochemistry and organic petrography in this study provides a format for refining the organic facies concept

extreme deformation characteristics and countermeasures for a tunnel in difficult grounds in southern shaanxi china the qingling bashan qb mountain region in southern shaanxi mainly consists of strongly compressive zones from east to west with tight folds and compressive fractures there is a wide distribution of soft rocks of various types such as phyllite and slate accompanied by complex geological structures ironically tunnel construction in these difficult grounds with complicated geological conditions embraces a high risk of extreme deformation due to various unpredictable reasons which can frequently cause collapse and result in budget overruns during the construction period therefore it is crucial to conduct effective countermeasures to eliminate or avoid such adverse impacts this paper provides a case study on the yingfeng tunnel a tunnel constructed in soft rock consisting of a slate ground based on a geological survey indoor experiments and in situ monitoring a successive rock mass deformation resulted in the tunnel lining seriously intruding into construction clearance and some other sections even collapsing during the construction the maximum displacement amount was 62 5 cm while the maximum deformation speed reached as high as 34 18 mm day additionally to evaluate the construction impacts of tunnelling induced geo hazards an investigation on extreme deformation was conducted considering the time dependent features of the rock mass deformation the constraint convergence method was used to put forward applicable countermeasures in this paper finally from the feedbacks of monitoring results extreme deformation of the yingfeng tunnel was effectively controlled

sedimentary architecture during carboniferous rift initiation the arid billefjorden trough svalbard analysis of the sedimentary architecture of the early billefjorden trough an exceptionally well exposed carboniferous half graben located in svalbard arctic norway allows detailed reconstruction of fault development and basin geometry sedimentary facies distribution reveals facies variability in an early synrift fill when an array of meso scale intra basinal faults segmented the basin into rotated blocks with differential subsidence growth of these faults into larger systems impacted the distribution of accommodation space and the drainage pattern expressed in fluvial and deltaic sandstone dominated units an axially back stepping character of the early synrift facies associations stages 1 3 is reflected in aggrading homogenous facies types of continental depositional stage 1 which evolved into back stepping facies belts of deltaic to nearshore depositional environment stages 2 and 3 due to the opening of a connection to the sea the drainage pattern and accommodation distribution in the early synrift deposits reflect a relatively symmetrical basin that predates a later prominent half graben configuration of the basin supplementary material figures presenting lithostratigraphic columns of the well data supplementary material 1 location of logs in ragnardalen supplementary material 2 and geological map used in figure 2b supplementary material 3 are available at https doi org 10 6084 m9 figshare c 4293077

relative role of accommodation zones in controlling stratal architectural variability and facies distribution insights from the fushan depression south china sea in sedimentary basins a better understanding of the controlling effect of accommodation transfer zones on stratal architecture and facies distribution can improve the success rate of locating hydrocarbon reservoirs the fushan depression is a half graben rift sub basin located in the southeast of the beibuwan basin south china sea in this study comparative analysis of seismic reflection palaeogeomorphology fault activity and depositional facies distribution indicates that three different types of inner basin slopes i e multi level step fault slope in the western area slope flexure zone in the accommodation zone area and gentle slope in the eastern area were developed along the southern slope of the fushan depression together with a large scale accommodation zone located at the intersection of the western and eastern fault systems further analysis shows that the accommodation zone played an important role in controlling not only stratal architectural variability in the southern slope but also depositional facies distribution in the accommodation zone area during the high stand stage the deposition of depositional systems was mainly controlled by sediment supply and the nw trending transfer faults major drainage systems entered the fushan depression through the accommodation zone along the direction of sediment supply and sedimentary flow paths were parallel to the accommodation zone axis with sedimentary flows constrained to the adjacent areas of the nw trending transfer faults by contrast during the low stand stage the transfer faults had little control over depositional facies distribution and the sublacustrine fan sediments diverted away from the accommodation zone and flew down along the northeast oblique to the accommodation zone axis the flow division in the lowstand stage might be greatly influenced by flow type and topography in addition the accommodation zone area demonstrated unique hydrocarbon accumulation models different from the western and eastern areas suggesting that the future exploration should be conducted at different levels in the fushan depression

late oligocene recent stress evolution in rift basins of northern and central thailand implications for escape tectonics abstract the tertiary rift basins of thailand are known through sub surface seismic and borehole data collected for hydrocarbon and coal exploration outcrops in open cast coal mines and a few natural outcrops these data provide mixed perspectives on how the basins evolved some providing data on ages and structural geometries others palaeostress data in general the region evolved under approximately e w extension although the extension direction probably changed periodically within basins extension was episodically interrupted by inversion events associated with sub horizontal nw se to ne sw 1 direction there is no evidence to suggest that the string of rift basins running from n thailand and laos into the gulf of thailand evolved in a similar way on the contrary the evolution of each basin seems different although certain regional trends along the rift system are apparent as follows 1 oligocene lower miocene extension is widespread in the region 2 in central and northern thailand middle miocene extension is also important and extension persisted into the upper miocene pliocene 3 in the extreme south of the area w natuna basin penyu basin malay basin extension ceased in the earliest miocene 4 in the northern gulf of thailand extension ceased in the middle miocene 5 thermal subsidence is greatest up to 4 km in the south malay pattani w natuna and penyu basins and least in northern thailand a few tens to hundreds of metres 6 inversion in the southern gulf of thailand was intense and occurred during the lower and middle miocene in the northern gulf of thailand inversion is very mild and occurred during the lower and middle miocene onshore inversion is patchy during the miocene but is strongest in the northwestern rift basins particularly the li basin the most widespread inversion event that affects the north occurred during the plio pleistocene it might be associated with the change from left to right lateral motion on the red river fault the relationship between strike slip faults and rift basins in terms of timing of extensional and inversion events and palaeostress orientation and evolution is more complex than can be explained by simple escape tectonic models

control of extensional transfer zones on syntectonic and post tectonic sedimentation implications for hydrocarbon exploration the gulf of suez red sea rift system exhibits superb outcrop examples of extensional transfer zones and displays the control of these zones on syntectonic and post tectonic sedimentation hard and soft linkage transfer zones were identified at variable scales hard linkage transfer zones form inward and outward fault kinks whereas soft linkage transfer zones form relay ramps between overlapping rift parallel faults the two types of transfer zones invariably exerted fundamental control on the deposition of syn and post tectonic sediments flow direction of drainage systems and locations of sediment entry points as well as the intensity of erosion patterns of the structurally high sediment source areas this study highlights the close relationship between the transfer zones and hydrocarbon accumulations in clastic syntectonic reservoirs in rift basins

estimation of in situ stress along deep tunnels buried in complex geological conditions abstract the headrace tunnels of the jinping ii hydropower station are 16 7 km in length and have a maximum depth of 2525 m many difficulties have been encountered in estimation of virgin rock stresses along the tunnels one method was presented including the macroscopic analysis of the region geological structures and topography and the integrated analysis of in situ stresses based on the multi source information in local tunnel sections the characteristics of geological structures and tectonic movement were studied to determine the orientations of the tectonic stresses within the jinping ii tunnel project region the influences of the topography on the distribution of in situ stress were analyzed using numerical methods the virgin stress regimes were preliminarily estimated based on the geological and topographical analysis and the world stress map under the guidance of these results multi source information was collected regarding rock brittle failures edzs core disking and large scale deformation of soft rock several techniques were adopted including multivariate regression numerical simulation and stereographic projection an iterative method for the orientations and magnitudes of in situ stresses is presented the in situ stress regimes orientations and magnitudes in tunnel sections of different depths were obtained and verified they can provide the basic conditions for analysis of the stability of surrounding rock mass during excavation

effect of ductile and frictional decollements on style of extension abstract scaled analogue models were used to study the effect of frictional and ductile detachments on thin skinned extension models consisted of two halves one half is the ductile and the other has a frictional detachment extension occurred above two different basal configurations a stretchable rubber sheet and a folded banded sheet intended to produce homogeneous and heterogeneous extension respectively model parameters varied systematically and included the brittle ductile thickness ratio rheologies and bulk strain structures in the two halves are compared in profiles and plan views a series of graben developed above both halves of models extended above a banded sheet although there were differences in style propagation rate and width of the deformation zone between the two halves different rates of propagation of structures in the two halves led to the formation of an accommodation or transfer zone parallel to the extension direction most relay ramps and inflection of normal faults in this zone indicate differential extension between the two halves in contrast in models extended above a stretchable rubber sheet extensional structures such as horst and graben developed only above the ductile detachment model results indicate that heterogeneous mechanical stratigraphy and displacement rate have no effect on extensional structure above a rubber sheet however above 20 bulk extension deformation becomes heterogeneous along multiple sets of conjugate faults oblique to the extension direction

the subsurface structure and stratigraphic architecture of rift related units in the lishu depression of the songliao basin china abstract this contribution reports the basin configuration feature stratigraphy and sedimentary architecture of the lishu depression in the songliao basin china the activity rate distribution and style of local faulting demonstrate the timing and extent of regional rifting distinct episodes of compressional tectonic activity caused uplift and exposure of strata evident as the traditional syn and post rift stages of basin evolution these episodes led to the sequential denudation of the upper jurassic huoshiling formation lower cretaceous yingcheng and denglouku formations and corresponding regional unconformities acting in tandem with regional compression activity along the major boundary faults influenced the evolving basin configuration as well as seismic sequences and sedimentary patterns seismic well log and drill core data described here show subdivision sections of the lishu depression strata according to discrete phases of the traditional syn rift stage of deposition we refer to these sub stages as the initial rifting the intensive rifting and the recession phases the basin configuration shifted from a graben half graben configuration during the initial rifting phase to a dustpan shaped half graben pattern during the subsequent phase of intensive rifting and finally into a gentle sedimentary basin during the final recession phase the early seismic sequence divides into a lowstand systems tract lst transgressive systems tract tst and highstand systems tract hst evidence of the lst within the seismic sequence becomes less apparent with the intensive rifting phase while the hst occupied an increasing proportion of the section the shallow water depositional fill formed during the final recession phase consists only of tst and hst components depositional environment then shifts from alluvial fan and shallow lacustrine systems to fan delta braided delta lake and finally to a braided fluvial setting the vertical stacking pattern shifts from retrogradational to progradational to aggradational identification of sub structural units and interpretation of their genetic relationships helps clarify basin evolution and thus serves larger scale continental basin analysis

numerical evaluation of a yielding tunnel lining support system used in limiting large deformation in squeezing rock large deformation in squeezing soft rock is a significant challenge that complicates the safety of underground construction engineering a yielding tunnel support system allows a certain amount of over excavation thereby accommodating large deformation in severely squeezing rock in this study a special yielding support system has been developed with a type of newly developed foamed concrete material which has a cushion effect the special yielding support uses pre cast foamed concrete blocks which are mounted in the primary lining and an in situ cast foamed concrete layer which is placed between the primary lining and the secondary lining the effect of the special yielding support on squeezing rock tunnels has been validated by comparing the numerical results with those of a lining strengthened stiff support system the incorporation of the foamed concrete blocks can both reduce the maximum and minimum principal stress in the primary lining relative to the stiff support the maximum and minimum principal stress in the primary lining are about 50 and 60 of those of the stiff support respectively thereby improving the stress state of the primary lining further compared with that in the stiff support the plastic zone in the secondary lining in this yielding support is significantly improved and the deformations at the roof and the sides of the secondary lining are 40 and 46 less than that of the stiff support respectively resulting in a better stress state and less deformation in the secondary lining

investigation of oil pool formation from the homogenization temperatures of fluid inclusions and biomarkers in reservoir rocks a genetic model for the deng 2 oil pool in the jiyuan depression abstract the jiyuan depression is a frontier area for oil and gas exploration in henan province china in recent years oil was discovered in the deng 2 well in the lower tertiary though the tectonics and petroleum geology of the depression are very complex a series of experiments on fluid inclusions in the oil bearing sandstones from the deng 2 well were made that included measurement of the homogenization temperatures of gas liquid inclusions and gc ms analysis of biomarkers either in the sandstone pores or in the fluid inclusions the deng 2 oil reservoir was formed at about 78 c corresponding to a burial depth of about 2200 m the present burial depth is about 700 m because of erosion and fault block uplift in oligocene time although oil in the sandstone pores is now heavily biodegraded the biomarkers in the inclusions show slight biodegradation representing a watering and biodegradation process that did not occur before formation of the deng 2 oil pool having investigated the structural evolution of the deng 2 trap it is concluded that the oil discovered in the tertiary reservoir of deng 2 well migrated from mesozoic reservoirs through active faults around the deng 2 trap as the oil migrated from the mesozoic to the tertiary reservoir the deng 2 trap was uplifted close to the depth of active biodegradation subsurface temperature lower than 80 c and to a burial depth shallower than 2250 m from the thermal gradient of 3 1 c 100 m so that the oil in the inclusions shows a slight biodegradation because of the continuous uplift of the deng 2 trap during the tertiary and quaternary the reservoired oil has been more heavily biodegraded compared to that in the inclusions

genetic features of petroleum systems in rift basins of eastern china abstract most oil bearing basins in eastern china are mesozoic cenozoic continental rifts which have played a habitat for oil and gas in china investigation of the petroleum systems may give a better understanding of the oil and gas habitats in these basins of the essential elements of the petroleum system the source rock is the most important in rift basins however rift tectonic evolution controls all the essential elements and processes necessary for a petroleum system a four stage evolution model is suggested for the controls in the rift basin a rift basin may consist of sub basins depressions and sub depressions and major moderate and minor uplifts a depression or sub depression has its own depocentre mainly occupied by source rock and all kinds of lacustrine sediments and thus has all the essential elements of a petroleum system however only those depressions or sub depressions which are rich in organic matter and deeply buried to generate oil and gas form petroleum systems immature oil another characteristic complicates the petroleum system in the rift basins three types of oil and gas habitats are described as a result of this analysis of the petroleum systems of the 26 largest oil and gas fields discovered in eastern china rift basins uplifts between oil source centres are the most prospective areas for oil and gas accumulations slopes connecting oil source centres and uplifts are the second and the third type is subtle traps in the oil source centre

greenland ice sheet thickness changes measured by laser altimetry precise airborne laser altimetry surveys at locations on the greenland ice sheet that had been accurately surveyed in 1980 and 1981 reveal a thickening in western greenland of up to two meters between 1980 and 1993 we cannot yet state whether this represents a long term trend or the cumulative effects of interannual variability of snow accumulation rates nevertheless the information presented here provides an indication of ice thickness changes across southern greenland in unprecedented detail laser altimetery surveys have now been made over all the major ice sheet drainage basins and will be repeated at regular intervals to provide detailed estimates of ice thickening thinning rates over the entire ice sheet

the effect of multiple pre existing weaknesses on formation and evolution of faults in extended sandbox models abstract high resolution three dimensional seismic data show that fault distribution and evolution in rift basins can be very complicated and inconsistent with the classic model of fault formation and propagation fault development in the presence of multiple pre existing weaknesses is still not clearly studied trying to understand the role of multiple pre existing weaknesses in sand models two series of experiments were prepared in the first series of models the mechanical properties of pre existing weaknesses were the same but their orientations were different whereas in the second series of models both mechanical properties and orientations were different the basic characteristics of fault formation and evolution in a rift basin revealed by the models are as follows 1 weakness reactivated faults faults that formed directly along and above the pre existing weaknesses and weakness related faults faults which are not located above the pre existing weaknesses but have similar orientation form much earlier than weakness unrelated faults the order of formation of different weakness reactivated faults is determined by the relative reactivation tendency factors fa of the weaknesses 2 weakness reactivated faults and weakness related faults develop mainly along or parallel to pre existing weaknesses in contrast weakness unrelated faults develop nearly perpendicular to the extension direction 3 a complicated fault system can form during a single extension phase in the presence of multiple pre existing weaknesses and 4 the mode of fault formation and propagation and the increase in length and number of faults have close ties to the nature of pre existing weaknesses fault displacement and length do not have a power law relationship for the majority of faults and there is no unique relationship for different kinds of faults in addition to providing new insights to the formation of complex fault systems the experiment results presented here could be reasonably explained using the reactivation tendency theory they can also be applied to the complicated fault system in rift basin

hydrocarbon potential of the meso cenozoic turkana depression northern kenya ii source rocks quality maturation depositional environments and structural control abstract source rocks identified by drilling loperot 1 well in the lokichar basin of the northern kenya rift were evaluated for source potential using rockeval pyrolysis and palynofacies analysis results indicate moderate to good oil source potential from algal prone source rocks the original sediments accumulated in a large freshwater lake similar to some modern rift lakes in the loperot 1 well the section with the highest source potential lies within the lokhone shale member up to 17 total organic carbon toc average 2 4 toc from well log calculation the other potential source interval is the deeper loperot shale member which is highly mature to post mature r 0 1 1 average 1 2 toc from well log calculation the poorer quality of the lower shale interval while partly due to maturity is thought to be largely a result of the basin evolution the loperot shale member was restricted to the lokichar basin while the lokhone shale member was deposited during a time when displacement on the main boundary fault system was greater and adjacent basins had been established consequently lacustrine conditions appear to have extended into adjacent basins thus allowing the accumulation of relatively higher concentrations of algal material in sediment starved parts of the basin