the variation of temperature with time and hydrocarbon maturation in sedimentary basins formed by extension abstract when a sedimentary basin is formed by extension both the subsidence history and the temperature gradient can be calculated hence the time temperature history of any stratum can be obtained three types of behaviour occur the temperature of material which never reaches depths greater than about 4 km increases at all times the time temperature history of material which finally sinks to greater depths reaches a maximum during the subsidence history the time at which this maximum occurs decreases as the depth increases at greater depths the maximum temperature occurs at the time the basin is formed the time temperature history is then used to calculate lopatin s maturation index for each stratum as a function of time and the index plotted as a function of depth and time for different amounts of extension the maximum temperature at a given depth and hence lopatin s index is almost independent of the amount of extension when the age of the basin is greater than about 150 ma similar calculations taking account of sediment compaction show the same behaviour though the maturity of the material at a given depth is increased because both lopatin s index and its calibration are empirical it is important to develop new maturation indices based on individual molecular reactions whose activation energies can be determined in the laboratory

upper bound solution for seismic bearing capacity of shallow foundations near slopes an upper bound technique of limit analysis is used to determine the bearing capacity of a shallow strip foundation near a slope the approach used is pseudo static and the seismic forces consist of a horizontal load applied to the foundation and the inertia of the soil mass the failure mechanism is composed of an active wedge a passive wedge and a shear transition zone between the two wedges the results are compared with those of other investigators

seismic bearing capacity of foundations on cohesionless slopes by applying the lower bound theorem of limit analysis in conjunction with finite elements and nonlinear optimization the bearing capacity factor n has been computed for a rough strip footing by incorporating pseudostatic horizontal seismic body forces as compared with different existing approaches the present analysis is more rigorous because it does not require an assumption of either the failure mechanism or the variation of the ratio of the shear to the normal stress along the footing soil interface the magnitude of n decreases considerably with an increase in the horizontal seismic acceleration coefficient kh with an increase in kh a continuous spread in the extent of the plastic zone toward the direction of the horizontal seismic body force is noted the results obtained from this paper have been found to compare well with the solutions reported in the literature c 2013 american society of civil engineers

calibration of resistance factors for geotechnical seismic design the next edition of the canadian highway bridge design code will contain a table of geotechnical resistance factors to be used for seismic design this paper will estimate the geotechnical resistan

influence of multistage oil emplacement on carbonate cementation in the eocene shahejie formation dongying sag bohai bay basin china abstract the influence of multi stage oil emplacement on carbonate cementation was investigated on the basis of determining the sequence of oil emplacement and carbonate cementation in the clastic reservoirs of the upper part of the fourth member of the eocene shahejie formation es4s in the yanxie 229 area dongying sag the sequence of multistage oil emplacement and carbonate cementation was determined by projecting the homogenization temperatures ths of two phase aqueous inclusions on a burial and thermal history plot the ratio of the number of quartz grains with yellow fluorescent oil inclusions therein to the total number of quartz grains ygoi and the ratio of the number of quartz grains with blue fluorescent oil inclusions therein to the total number of quartz grains bgoi were calculated to analyze the paleo oil saturation of each stage of oil emplacement the ygoi and bgoi values reflect the relative level of the paleo oil saturation of the first stage yellow fluorescent fsyf oil and the second stage blue fluorescent ssbf oil respectively a large number of primary pores were preserved in the oil layers whereas only a small number of dissolution pores and micropores were developed in the oil bearing water layers and dry layers calcite dolomite ferrocalcite and ankerite cementation and two stage oil emplacement occurred in the es4s reservoirs the fsyf oil emplacement occurred earlier than the ankerite cementation and ferrocalcite cementation but later than the calcite cementation and dolomite cementation the ssbf oil emplacement occurred later than all phases of carbonate cementation the dolomite cementation was not influenced by the fsyf oil emplacement because it occurred earlier than the fsyf oil emplacement the ankerite cementation was dominantly inhibited by the fsyf oil emplacement in the oil layers and the degree of inhibition increased with the increase in paleo oil saturation of the fsyf oil the ssbf oil emplacement further increased the paleo oil saturation in the oil layers which enhanced the inhibition of the ankerite cementation and even stopped it the ankerite cementation in the dry layers and oil bearing water layers was slowed down or stopped due to the lack of pores and the low transportation rate of external material which was caused by the intense ankerite cementation prior to the ssbf oil emplacement

isrm suggested methods for rock stress estimation part 3 hydraulic fracturing hf and or hydraulic testing of pre existing fractures htpf contents1 introduction 10112 summaryoftestmethods 10123 assumptionsandlimitations 10123 1 hydraulicfracturing hf 10123 2 hydraulictestsonpre existingfractures htpf 10124 apparatus 10134 1 fractureorientationdetectiondevices 10145 personnelquali cation 10146 equipmentperformance 10147 hydraulicfracturingtestprocedure 10148 hydraulic fracturedelineation 10168 1 impressionpackertechnique 10168 2 geophysicalimagingtechnique 10179 obtainingcriticalpressureparametersfromthepressure timerecords 101710 stresscalculations 101810 1 hydraulicfracturing hf 101810 2 hydraulictestsonpre existingfractures 101911 reportingofresults 1019references 1020

simulation of hydraulic fracturing using particle flow method and application in a coal mine abstract the purpose of hydraulic fracturing is to improve the gas permeability of a coal seam by the high pressure injection of fracturing fluid into cracks this paper simulates the hydraulic fracturing of a coal seam investigates relevant parameters and analyzes the connection between macroscopic mechanical parameters and mesoscopic mechanical parameters based on two dimensional particle flow code pfc2d furthermore the influence of macroscopic mechanical properties on the initiation and size of cracks is studied based on various combinations of particle flow calculations empirical formulae for the breakdown pressure and fracture radius are derived moreover the effect of the injection parameters on crack propagation is computed and analyzed after which the relevant empirical formula is proposed finally numerical simulation of the working face n3704 at yuyang coal mine ycm is conducted and the comparison of results from simulation empirical formulae and field observation is investigated the research findings of this paper may provide a reference for selecting injection parameters and forecasting the effect in practical hydraulic fracturing applications

evidence for resetting of fluid inclusion temperatures from quartz cements in oilfields abstract quartz is a major pore occluding cement in north sea oilfield reservoir sandstones fluid inclusions yield homogenization temperatures t h which have been thought to represent growth temperatures for the host quartz however early diagenetic inclusions from the detrital grain overgrowth boundary yield excessively high palaeotemperatures which do not match the growth temperatures calculated from the depth of cementation the temperatures of these inclusions increase with present day depth of burial and approach present day reservoir temperatures this suggests that the inclusions have begun to reset towards present day pressure temperature conditions the t h of the inclusions hence represent burial temperatures rather than growth temperatures for the quartz experimental studies indicate that the amount of resetting undergone by an inclusion varies depending on its size shape and fluid composition a relationship between inclusion t h and these variables has been observed in inclusions from deeply buried quartz cements in the north sea

diagenetic paths in the margin of a triassic basin nw zone of the iberian chain spain buntsandstein deposits generated in a slowly subsiding basin on the western margin of the iberian chain are represented by a stratigraphic succession of fluvial deposits less than 100 m thick conglomerates sandstones and shales diagenetic processes in sandstones can be grouped as eodiagenetic mesodiagenetic and telodiagenetic eodiagenesis can be associated with muschelkalk keuper and probably early jurassic times mesodiagenesis is probably related to jurassic times diagenetic chemical reactions suggest a maximum burial less than 1 5 km and low temperatures 120oc patterns of porosity reduction by compaction and cementation suggest four diagenetic stages 1 loss of primary porosity by early mechanical compaction 2 early cementation kfeldspar and dolomite 3 dissolution of cements and 4 framework collapse by re compaction these stages are manifested by the presence of two types of sandstone type i sandstones present high intergranular volume mean 30 type ii sandstones are characterized by high compactional porosity loss and exhibit low values of intergranular volume mean 16 9 type ii sandstones are associated with the dissolution of cement and later re compaction of type i sandstones an intermediate telodiagenetic phase is deduced and related to the sharp unconformity between lower cretaceous sediments and the underlying sediments this suggests that a mechanically unstable framework collapsed during the cretaceous generating type ii sandstones the analyzed diagenetic paths have a wide applicability on similar marginal areas of rift basins

geochemistry and origin of sour gas accumulations in the northeastern sichuan basin sw china significant natural gas reserves have recently been discovered in the lower triassic oolitic reservoirs from northeastern sichuan basin sw china in the wake of the december 2003 sour gas well blow out this study presents an overview on the petroleum geology and geochemistry of the sour gas accumulations in the study area two types of natural gas accumulations were identified in the lower triassic oolitic reservoirs both containing highly mature thermogenic gases with their hydrocarbon source rocks in upper permian strata natural gases from the area south of the ancient kaijiang liangping seaway are generally sweet gases formed as the result of thermal maturation whereas those discovered from north of the seaway are products of both thermal maturation and thermochemical sulfate reduction of early accumulated oils in the feixianguan formation reservoirs the proposed origins of the gases are supported by their chemical and stable carbon isotope compositions as well as the presence or absence of pyrobitumens in the reservoir the distribution of gas accumulations is controlled predominantly by the combination of lithologic and structural factors the regional variation in the concentrations of h2s in the gases appears related to the presence and thickness of anhydrite bearing evaporitic rocks interbedded or intercalated with the oolitic reservoirs

tectono thermal evolution of cambrian ordovician source rocks and implications for hydrocarbon generation in the eastern tarim basin nw china abstract the tectono thermal evolution is an important control on petroliferous basin development however this evolution is difficult to reconstruct in sedimentary basins subjected to multiple tectono thermal events the tarim basin is the largest petroliferous basin in northwestern china and hosts a complex oil gas system comprising several sets of source reservoir and cap rocks that have experienced multiple tectonic thermal and sedimentary events large oil and gas reserves have been discovered in the central and northern tarim basin during the last 30 years but none in the eastern part of the basin this is generally attributed to the high thermal maturity reached by source rocks during the late ordovician and subsequent hydrocarbon loss therefore reconstructing the cambrian ordovician tectono thermal evolution is critical in facilitating successful oil and gas exploration in this region we compiled equivalent vitrinite reflectance data n 178 of source rocks from seven wells in the tarim basin which for cambrian ordovician source rocks are 1 3 beyond the hydrocarbon generation threshold and in the main gas and dry gas generation stages the cambrian ordovician source rocks experienced rapid burial and heating during the caledonian period entered the hydrocarbon generation stage during the middle late ordovician and reached peak hydrocarbon generation at the end caledonian period they might have experienced secondary hydrocarbon generation after the jurassic homogenization temperatures of fluid inclusions n 616 from wells gc4 lx1 md1 and yd2 as well as the modeled thermal evolution reveal a main hydrocarbon generation event during the caledonian period and a secondary event in the yanshanian and himalayan period in other wells lx1 md1 and yd2 hercynian and indosinian uplift and exhumation in the eastern tarim basin controlled the main structures and faulting created favorable conditions for secondary hydrocarbon generation and migration at this time since the yanshanian and himalayan the tarim basin has experienced further sedimentation and heating and the tectono thermal evolution might have been related to the formation of the tibetan plateau in summary our reconstruction of the tectono thermal evolution of cambrian ordovician strata and the hydrocarbon generation history of the tarim basin suggests that the eastern tarim basin may also have hydrocarbon generation potential and can guide future oil and gas exploration

thermal history of sedimentary basins maturation indices and kinetics of oil and gas generation temperature is the most sensitive parameter in hydrocarbon generation thus reconstruction of temperature history is essential when evaluating petroleum prospects no measurable parameter can be directly converted to paleotemperature maturation indices such as vitrinite reflectance tmax from rock eval pyrolysis spore coloration thermal alteration index tai or concentration of biological markers offer an indirect approach all these indices are a function of the thermal history through rather complex kinetics frequently influenced by the type of organic matter their significance and validity are reviewed besides the problems of identification e g vitrinite and interlaboratory calibration it is important to simultaneously interpret kerogen type and maturation and to avoid difficult conversions from one index to another geodynamic models where structural and thermal histories are connected are another approach to temper ture reconstruction which could be calibrated against the present distribution of temperature and the present value of maturation indices kinetics of kerogen decomposition controls the amount and composition of hydrocarbons generated an empirical time temperature index tti originally introduced by lopatin does not allow such a quantitative evaluation due to several limitations no provision for different types of kerogen and different rates of reactions poor calibration on vitrinite reflectance it is of limited interest unless one has no access to a desk top computer kinetic models based on a specific calibration made on actual source rock samples can simulate the evolution of all types of organic matter and can provide a quantitative evaluation of oil and gas generated examples from the jurassic source rocks of the paris basin monterey formation of california green river shales of utah paleozoic source eds of the algerian sahara and miocene rocks of the mahakam delta indonesia illustrate various aspects of the discussion geological geochemical models are the most efficient way to integrate geological seismic and geochemical data and they should greatly help to reduce the risk in exploration

neoproterozoic cambrian petroleum system evolution of the micang shan uplift northern sichuan basin china insights from pyrobitumen rhenium osmium geochronology and apatite fission track analysis the neoproterozoic strata of the sichuan basin are a key target for oil and gas to evaluate the hydrocarbon evolution and its relationship with tectonic events in the micang shan uplift northernmost sichuan basin we apply solid bitumen geochemistry bitumen reflectance and fluorescence and re os geochronology the geochemistry of the solid bitumen indicates that it is highly mature pyrobitumen that formed contemporaneously with dry gas generation during oil thermal cracking the pyrobitumen is enriched in both re 106 191 ppb and os 3030 5670 parts per trillion the re os isotope data imply an early jurassic date for pyrobitumen formation which coincides well with age estimates from fluid inclusion data and basin modeling the re os date for pyrobitumen formation coupled with previously presented apatite fission track aft analysis show that exhumation of the neoproterozoic strata occurred during the cretaceous in the micang shan uplift this extensive uplift led to the erosion of any potential gas reservoirs and surface exposure of bitumen bearing neoproterozoic strata in contrast the more southern and central portions of the sichuan basin have experienced less severe exhumation and as a result neoproterozoic sourced gas systems are present this study shows that through the combined application of re os and aft methodologies the timing of gas generation and subsequent erosion of any potential gas reservoirs in the micang shan uplift northern sichuan basin can be quantified moreover the re os and aft data illustrate the potential to constrain the timing of gas generation in petroleum systems worldwide

seismic bearing capacity factors for spread foundations the effect of horizontal earthquake body forces on the bearing capacity of foundations has been examined computationally in a rigorous manner by employing the method of stress characteristics the bearing capacity factors n c n q and n y due to the components of soil cohesion ground surcharge pressure and soil unit weight respectively have been plotted as a function of earthquake acceleration coefficient a h for different values of soil friction angle phi the inclusion of earthquake body forces causes a considerable reduction in the bearing capacity factors the bearing capacity factors n c and n q are seen to be approximately of the same magnitude as those reported in the literature on the basis of different solution methods however the obtained values of n y are found to be significantly smaller than the available results the nature of the pressure distribution along the footing base and the geometry of the observed failure patterns vary with the consideration of earthquake body forces

synthetic saline aqueous and hydrocarbon fluid inclusions trapped in calcite at temperatures and pressures relevant to hydrocarbon basins a reconnaissance study abstract we conducted reconnaissance experiments to synthesize aqueous and hydrocarbon inclusions trapped in calcite at conditions relevant to petroleum basins and characterize the microthermometric properties of such inclusions fluid inclusions fis were synthesized in a system of saline aqueous solution 5 or 20 wt nacl coexisting with either heavy crude oil or gasoline under gas undersaturated conditions from 90 to 210 c and 200 550 bar the synthetic inclusions are not representative of gas bearing systems and methane ch 4 was not detected in any aqueous inclusions the fis are mainly distributed along planar healed cracks indicating that the inclusions formed by fracture healing in the calcite crystal microthermometric measurements were conducted on coeval aqueous and hydrocarbon inclusions and raman spectroscopic analyses were done on aqueous inclusions to determine the properties of fis trapped at these conditions homogenization temperatures of synthetic fis are mostly lower than the experimental trapping temperature although the fis show high variability in measured homogenization temperature results allow comparison of t h values for each sample with the expected t h isochores and pressure corrections calculated for the system h 2 o nacl the latter parameters are broadly consistent with the known pvtx properties of h 2 o nacl fluids suggesting little effect of hydrocarbons on the homogenization behavior although the low precision of the t h data limits this assessment nevertheless this result is not unexpected considering that light hydrocarbons gas is not present in the experiments as corroborated by raman spectroscopy a consequence of using dead oil in the experiments simulation of gas bearing petroleum basins will require additional protocols for producing gas either by in situ cracking of the starting hydrocarbon material or by other means the reconnaissance experiments documented here provide a basis for such future experiments

distinct element modeling of hydraulically fractured lac du bonnet granite 1 the aim of this study is to better understand the mechanics of fracture development and propagation during hydraulic fracturing this paper presents some development and applications of discrete particle modeling of this problem a discontinuum modeling approach idealizes the material as separate particles bonded together at their contact points and utilizes the breakage of individual structural units or bonds to represent damage the numerical models are correlated with existing hydrofracture laboratory experiments which are presented in other publications a simulation of a laboratory scale hydrofracture experiment and the acoustic emission ae data from the experiment is used to validate the synthetic aes produced in the hydrofracture model this technique has been used to examine the mechanics of fracture initiation and time and spatial distributions of ae the modeling results demonstrate that the mechanism of hydraulically induced fracture in the lac du bonnet ldb granite core sample is predominantly tensile failure and that the shear cracks recorded in the hydrofracture experiment were due to slip on preexisting fractures numerical modeling of hydrofracture on homogeneous and heterogeneous synthetic samples seems to capture much of the behavior observed in the laboratory hydrofracture experiments

oxygen isotope microanalysis by secondary ion mass spectrometry suggests continuous 300 million year history of calcite cementation and dolomitization in the devonian bakken formation calcite cementation and dolomitization are key diagenetic processes in many sedimentary systems unravelling detailed histories and timescales of cementation and replacement is however often compromised by the limited spatial resolution of many analytical techniques in some cases multiple grains are co analyzed so that diagenetic histories are blurred and reaction periods are difficult to establish in this study we have used 10 micrometer resolution in situ secondary ion mass spectrometry to determine the oxygen isotope composition of 197 individual 10 50 micrometer size crystals of dolomite and calcite from six samples in a single core of upper devonian middle bakken member siltstones and sandstones the major tight oil formation of the williston basin usa this amount of data places important constraints on the range of temperatures and times that carbonate cementation and replacement occurred petrographic data show that microcrystalline calcite cement is an early phase and combined with mineralogical data suggest that much of the dolomite replaces calcite over spatial scales of less than a centimeter analyses of individual calcite crystals have a range of 5 for 18o in the group of crystals and for the group of individual dolomite crystals 10 these sub centimeter ranges are as great as those observed in previous studies of carbonate cements sampled over many meters and remind us that previous low resolution studies may have inadvertently analyzed mixed phases there is no relationship between dolomite texture and isotopic composition at this spatial scale microscale backscattered electron imagery and scanning electron microscopy cathodoluminescence zoning is seen but cannot be resolved with a 10 micrometer spot size assuming since it is an early cement that calcite precipitated from seawater 18o 1 5 it formed at ca 15 40 c mainly at the lower temperatures present day formation waters in devonian rocks in this region have oxygen isotope compositions of 7 8 vsmow using these values as a likely dolomitizing fluid we suggest that dolomitization occurred continuously between 40 and 140 c over 150 200 million years most likely in a fluid with a high mg ca ratio resulting from gypsum formation in local evaporites we suggest that this exceptionally low rate of dolomitization was controlled by the low rate of supply of mg in a very sluggish flow regime dolomitization is incomplete because of a limited supply of mg

relationship between reservoir diagenetic evolution and petroleum emplacement in the ula field north sea abstract the diagenetic and petroleum filling histories of the ula field have been studied by analysing aqueous and petroleum inclusions occurring in authigenic cements this study shows that diagenesis continues actively after the arrival of petroleum in the sandstones although the reaction rates and petroleum saturation remain obscure microthermometric measurements of fluid inclusions in authigenic quartz suggest an onset of extensive quartz cementation at temperatures around 110 c i e 2 5 km and that this cementation has continued to the present day synchronously with quartz cementation authigenic albite was formed as inter and intragranular cements large amounts of petroleum inclusions locally occur in the albite and quartz cements these inclusions were trapped in the cements as the main charge of petroleum arrived at the structure diffusion through thin water layers between the petroleum and the mineral surface would probably have dominated mass transfer of solutes for the precipitation of authigenic quartz and albite it is evident from analysis of the petroleum inclusions in early formed k feldspar overgrowths that some secondary migrated petroleum probably arrived in the reservoir at a shallow burial depth before the rapid subsidence in the last 25 my compared with petroleum in the free porosity of the ula formation the petroleum in the k feldspar inclusions is evidently sourced from a different source facies and most maturity parameters testify to the latter being less mature later trapped petroleum inclusions in quartz and albite have characteristics found both in k feldspar and in the ula formation dst oil and thus is likely to reflect the progressive change in the ula field petroleum charge which occurred during the time period of quartz diagenesis

timing and mechanism of reservoir forming in the upper triassic halahatang formation yuqi block tarim basin northwestern china abstract the yuqi block is an important area for oil and gas exploration in the northern akekule uplift tarim basin northwestern china the upper triassic halahatang formation t 3 h within the yuqi block can be subdivided into a lowstand system tract lst a transgressive system tract tst and a highstand system tract hst based on a study of initial and maximum flood surfaces oil in the lowstand system tract of the halahatang formation is characterized by medium to lightweight 0 8075 g cm 3 0 9258 g cm 3 low sulfur content 0 41 1 4 and high paraffin content 9 65 10 25 the distribution of oil and gas is principally controlled by low amplitude anticlines and faults based on studies of fluorescence thin sections and homogenization temperatures of fluid inclusions reservoirs in the t 3 h were formed in at least two stages of hydrocarbon charge and accumulation during the first stage jurassic cretaceous both the structural traps and hydrocarbon reservoirs were initiated during the second stage cenozoic the structural traps were finally formed and the reservoirs were structurally modified the reservoir forming mechanism involved external hydrocarbon sources i e younger reservoirs with oil and gas sourced from old rocks two directions vertical and lateral of expulsion and multi stage accumulation this model provides a theoretical fundament for future oil and gas exploration in the tarim basin and other similar basins in northwestern china

evolution of quartz cementation and burial history of the eau claire formation based on in situ oxygen isotope analysis of quartz overgrowths abstract individual quartz overgrowths in siltstone of the late cambrian eau claire formation fm are systematically zoned in oxygen isotope ratio 18 o in situ analysis of 18 o was performed with 3 and 15 m beam spots by secondary ion mass spectrometer sims on detrital quartz grains and quartz overgrowths these results from thin lenses within impermeable mudstones reflect samples that were sealed from basin wide fluid flow and compliment previous studies of more permeable sandstones individual grains of detrital quartz dq are homogeneous in 18 o the average 18 o values in fine grained detrital quartz in mudstones and siltstones and in coarser grained quartz in the eau claire fm mt simon and st peter sandstones ss are essentially identical at 18 o 10 vsmow suggesting that detrital quartz is dominantly igneous in origin the 18 o values of overgrowth quartz oq of buried samples from the illinois basin are higher and quartz overgrowths are systematically zoned outward from the detrital cores these gradients are similar to those from the underlying mt simon ss and are best explained by increasing temperatures during burial pressure solution is evident in thin section and may have supplied significant silica for overgrowths in contrast to the deeply buried samples from the illinois basin quartz overgrowths in samples from the wisconsin arch are homogeneous and higher in 18 o those overgrowths are interpreted as quartz cements formed in a near surface environment based on these 18 o oq results and the modeled thermal history during burial of the basin the earliest formed quartz overgrowths were produced at low temperature from low 18 o water around 450 ma the 18 o values in traverses of single overgrowths decrease by up to 9 1 showing continued cementation with increased burial pressure solution and heating until 250 ma in traverses of the outermost zone of some overgrowths oxygen isotope values become constant or increase slightly possibly due to clay mineral dehydration reactions or later fluid infiltration we present a new cementation and basin evolution model in which the 18 o of cement correlates to the age of formation and the late overgrowths formed between 270 and 250 ma during and or after the migration of brines that formed the pb zn deposits of the upper mississippi valley district 270 ma cementation around 270 ma would have reduced permeability possibly ending the flow of ore forming brines

diagenesis thermal maturation and burial history of the upper cambrian bonneterre dolomite southeastern missouri an interpretation of thermal history from petrographic and fluid inclusion evidence abstract in this report fluid inclusion thermal alteration index tai and petrographic data are used to interpret thermal maturation and burial history of the bonneterre formation of southeastern missouri tai visual estimates based on indigenous upper cambrian acritarchs indicate maximum thermal exposure into the mid upper peak gas window this interpretation is in agreement with maximum fluid inclusion homogenization temperatures which average 235 c 455 f or an approximate vitrinite equivalent of 1 7 r0 thin section petrography and fluid inclusion evidence further indicate that three separate episodes of burial have occurred initial burial of unknown depth or thermal exposure culminated in a period of uplift and karstic subaerial exposure possibly during late ordovician time maximum burial and thermal exposure to the mid upper peak gas window followed and is represented in the rock by a high temperature 235 c randomly oriented two phase fluid inclusion population in matrix dolomite subsequent uplift possibly coincident with ouachita overthrusting resulted in a variety of diagenetic fabrics including late burial cements and fractures secondary two phase fluid inclusions within these late calcite cements and those occurring in linear trains that cut across matrix dolomite record lower average homogenization temperatures than their unoriented precursors average th 170 c or an approximate equivalent of 1 3 r0 further indicating that a significant amount uplift has occurred since maximum burial present day bottom hole temperatures of only 74 c an approximate equivalent of 0 7 r0 indicate that uplift has occurred after this second burial episode this event probably coincides with the development of the new madrid fault system during the tertiary which still active today these results demonstrate the utility of fluid inclusion microthermometry complex burial thermal histories

seismic bearing capacity of foundations on slopes the effect of pseudo static horizontal earthquake body forces on the bearing capacity of foundations on sloping ground has been assessed using the method of stress characteristics two failure mechanisms were considered based on the extension of the characteristics from the ground surface towards the footing base from either one side or both sides the magnitude of n gamma based on the both sides failure mechanism for smaller values of earthquake acceleration coefficient alpha h has been found to be significantly smaller than that obtained using the single side mechanism however in the presence of alpha h the both sides mechanism becomes kinematically inadmissible in many cases for higher values of phi only the single side mechanism was found statically admissible for computing the bearing capacity factors n c and n q on sloping ground all the bearing capacity factors reduce considerably with increase in ah for various ground inclinations

dynamics of fluid inclusion alteration in sedimentary rocks a review and discussion abstract fluid inclusions represent small volumes of interstitial fluids in crystal imperfections flaws during crystal growth and or deformation the entrapped fluids are commonly believed to preserve information on the composition pressure and temperature of fluid inclusion formation and later diagenetic alterations it is now known that fluid inclusions can be dynamic structures responsive to thermal and tectonic stresses by plastic and brittle deformation of the entrapping mineral wall these dynamic responses may include both morphologic and volumetric changes a comparison of measured fluid inclusion homogenization temperatures with sample burial depths for diagenetic studies from around the world show a strong positive correlation this correlation suggests that fluid inclusion stretching which results in increased homogenization temperatures is a common phenomenon associated with burial diagenesis burial diagenesis shifts and spreads the measured homogenization temperatures towards maximum burial conditions confining mineralogy shape size and composition of the fluid inclusions are important factors in determining the mode and degree of fluid inclusion deformation stretching classical fracture mechanics theory of predicts that plastic and brittle deformation of the surrounding mineral crystall will occur with burial and that annealing retrograde stretching of the strain in the inclusion walls will not occur in low temperature regimes experimental theoretical and field studies all indicate that fluid inclusions will react dynamically to burial diagenesis by increases in measured homogenization temperatures with increased burial it is suggested that this relationship can be selectively used to help determine the approximate maximum thermal exposures experienced by a sedimentary rock

quartz cementation history of sandstones revealed by high resolution sims oxygen isotope analysis abstract evaluating the timing and origin of quartz cement is central to understanding how porosity is lost in sandstones during burial kinetic models of quartz cementation have been calibrated using large scale datasets but have never been tested at the microscopic level at which cement forms here we use high precision in situ oxygen isotope analyses on sandstone from the jurassic ness formation from the north sea to reveal the growth history of single quartz overgrowths to a resolution of 2 m measured 18o cement range from 28 to 20 v smow in early to late cement and are consistent with quartz cementation models that propose the bulk of quartz precipitates as a continuous process beginning at 60 70 c quantitative x ray diffraction analyses and clay mineralogical analysis of interbedded shales are inconsistent with a silica source from shale implying that silica for the cement is sourced internally to the sand these isotope data are broadly consistent with predictive conceptual quartz cementation models and provide a critical link from micron scale measurements to basin scale predictions and observations

foundation models in seismic areas four case studies near the city of granada spain abstract this paper presents four case studies of the geotechnical characteristics of foundation design under seismic conditions in towns located in the province of granada spain much of this province is affected by seismic activity caused by active faults in the betic cordillera the alboran sea the atlantic ocean and the area around the northern border of africa from morocco to algeria although seismic activity in the region is moderate with peak accelerations of 2 4 m s 2 for a return period of 475 years it is the region with the highest seismic risk in the iberian peninsula the four study areas include the towns of atarfe albolote fuente vaqueros churriana de la vega and the district of la chana the nw sector of the city of granada churriana de la vega has a very homogeneous soil profile with a coarse granulometry high relative density high bearing capacity high field penetration test values and a deep water table in contrast the other three areas have a seasonally shallow water table and extremely variable soil profiles in terms of bearing capacity they are characterized by predominantly fine alluvial soils of low relative density and with low field penetration test values they are thus susceptible to seismic effects such as liquefaction and densification based on geotechnical reports dynamic penetration tests and direct shear and consolidation tests on disturbed samples we first defined the basic mechanical properties of the soil under static conditions and determined the features related to bearing capacity and foundation design the next step was to analyze the corresponding dynamic geotechnical parameters by using various empirical correlations between static and dynamic parameters for this purpose our research study took into account the definitions and criteria regarding bearing capacity under seismic conditions regulated by the spanish nsc 02 and european eurocode 8 technical codes the results obtained led us to propose new foundation types which would be capable of withstanding potential seismic action these improved foundations have a better load distribution and higher stiffness thanks to strip footing reinforced concrete plates and the occasional use of deep piling the dynamic actions of the terrain and the associated settlement effects due to soil liquefaction or densification showed that the areas most in need of deep foundations were located around albolote as a result a deeper foundation is necessary such as the type found in fuente vaqueros where geotechnical conditions are even more unfavorable

seismic bearing capacity of soils this paper derives the seismic bearing capacity factors for a c phi soil within the framework of the mohr coulomb theory horizontal and vertical accelerations and the effects of a inertia forces of the soil both below and above the footing and b the applied loads are all taken into consideration the method is used to derive the ultimate seismic bearing capacity for a square footing 2 5m wide founded 1 0m below a homogeneous soil with c soil cohesion parameter 7 kpa phi 25 degrees and a unit weight of 18 kn per cubic metre the results indicate that the horizontal accelerations as well as soil cohesion and vertical accelerations affect the bearing capacity coefficients considerably

dating diagenesis in a petroleum basin a new fluid inclusion method the final porosity and permeability of sandstone petroleum reservoirs is greatly affected by the diagenetic growth of minerals after deposition for example a sand may be deposited with a porosity of 25 and a permeability of 5 000 mdarcy md 1 diagenetic growth of quartz around detrital sand grains may leave a rock with only 10 porosity and later growth of clays may partly fill these remaining pores and block inter pore connections reducing permeability to 100 md ref 2 if the depth and timing of such diagenetic alteration can be measured and the extent of diagenesis estimated then prediction of the diagenetic state of undrilled sandstones may become possible and diagenesis related more closely to the timing of hydrocarbon migration and the formation of hydrocarbon traps we present an example of a new method for estimating the date of quartz diagenesis using a combination of techniques from thin section petrography fluid inclusion thermometry organic geochemical thermometry and sedimentary basin stratigraphic analysis these results suggest that quartz in the beatrice oilfield was precipitated from moving and cooling pore fluids at a temperature between 68 c and 94 c in the late jurassic

duration of quartz cementation in sandstones north sea and haltenbanken basins abstract evidence from fluid inclusions petrography and burial history modelling is used to estimate the duration of quartz cementation in sandstones the homogenization temperatures of primary fluid inclusions in quartz cements from samples from the brent group north sea and haltenbanken offshore norway show variations 4 of 17 4 and 20 2 c these are interpreted to reflect durations of less than approximately 9 and 17 ma low variances are general features of such data sets and suggest that quartz cementation usually takes place as events with durations of the order of 10 ma or possibly less confining the age of quartz cement growth using a combination of geological petrographical and radiometric dating methods that are independent of fluid inclusions also suggests that quartz cements grow over periods substantially shorter than the age of the sandstone it is not easy to reconcile this deduction with the suggestion that burial itself causes cementation

static and seismic passive earth pressure coefficients on rigid retaining structures the passive earth pressure problem is investigated by means of the kinematical method of the limit analysis theory a translational kinematically admissible failure mechanism composed of a sequence

isomerization and aromatization of hydrocarbons in stretched sedimentary basins we have calculated the progress of two reactions both involving biological marker compounds which occur in shales rich in organic matter both reactions are associated with the early stages of oil generation one of these reactions is an isomerization reaction of a sterane1 2 the other involves the aromatization of monoaromatic steroid hydrocarbons3 4 both reactions have recently been discussed by mackenzie et al 5 we demonstrate that the observed progress of these reactions within two basins formed by extension the north sea and the pannonian basin can be reproduced in some detail by a simple model of basin formation6 we used samples from basins formed by stretching the lithosphere because both the subsidence history and the variation of heat flux with time is principally controlled by the amount of extension6 10 in contrast the subsidence of the other major class of sedimentary basins which are formed by flexure of the continental lithosphere11 13 can only be modelled when the geological history of the region is known in detail13 and such models do not constrain the history of the heat flux