radionuclide diffusion rates in igneous crystalline rocks abstract previous work on diffusion in geologic materials indicates that diffusion may be a significant radionuclide transport and retardation mechanism in igneous crystalline rocks a study of the pore structure of igneous rocks and theoretical and experimental diffusion was initiated in 1978 under the canadian nuclear fuel waste management program theoretical predictions of diffusion based on modifications of fick s laws and pore structure information show excellent agreement with experimental results this suggests that methods are available to predict radionuclide diffusion rates over prolonged periods of time in excess of 0 1 ma in rocks that could form the barriers required to isolate nuclear fuel waste a parameter termed diffusion radius rd has been developed which can be used to predict diffusion rates and contribute in comparing rock types in terms of their suitability for isolating nuclear fuel waste according to results obtained thus far radionuclides are not expected to travel more than a few hundred metres in a period of 0 1 ma the results also indicate that diffusion distances in gabbros are smaller than in granites on the other hand retardation effects may be greater in granites than in gabbros some pore parameters that may play an important role in predicting retardation have been identified

petroleum origin and accumulation in basin evolution a quantitative model basin data geologic geophysical geochemical hydrodynamic and thermodynamic can be combined for quantified hydrocarbon prediction a three dimensional deterministic dynamic basin model can be constructed to calculate all the measurable values with the help of mass and energy transport equations and equations describing the physical and or physicochemical changes in organic matter as a function of temperature input data consist of heat flux initial physical and thermal properties of sediments paleobathymetric estimates sedimentation rate and amount and type of organic matter subsequently the model computes pressure temperature physical and thermal properties of sediments maturity of organic matter and the hydrocarbon potential of any source rock as a func ion of space and time thus the complex dynamic processes of petroleum formation and occurrence in a given sedimentary basin can be quantified for example hydrocarbon potential maps for any given source rock and any geologic time slice of the basin evolution can be provided as computer printouts the computer model can be applied to any stage of an exploration campaign and updated as more information becomes available

diffusivity measurements and electrical resistivity measurements in rock samples under mechanical stress if radionuclides are released from an underground repository and enter the groundwater they would be transported with the moving groundwater in fissures in the rock besides fissures the rock also contains micropores filled with stagnant groundwater if the nuclides are able to diffuse into these micropores a significant retardation of the nuclides can be expected at repository depths the rock is exposed to rather high stresses caused by the large overburden of rock when drill cores are taken up from the gound this overburden no longer exists as a result of this there might be an increase in the porosity of the rock samples the effective diffusivity measured in rock samples under atmospheric pressure in the laboratory would then be higher than the effective diffusivity in the rock in situ to simulate the stress that may exist in the bedrock at large depths diffusion experiments with iodide and electrical resistivity measurements in rock materials under mechanical stress have been performed it was found that the diffusivity in rock samples at 300 350 bars stress was reduced to 20 70 of the value in the samples under atmospheric pressure this reduction of the diffusivity in stressed rock is probably of minor importance because of the rather large variation in diffusivity between samples

a new carboniferous coal shale driven gas play in the western black sea region turkey the sedimentary sequence in the western black sea region of turkey both onshore and offshore offers many possibilities for different hydrocarbon plays this study presents a new play which considers carboniferous coals and shales as source beds cretaceous sandstones as reservoirs and cretaceous shales and marls as seal rocks the evaluation of this play is performed using the petroleum system approach results suggest that the coals and shales have a good to very good source rock potential for gas that the cretaceous synrift sandstones are good reservoirs on the other hand the sealing efficiency of respective cretaceous units is assumed to be sufficient based on their lithological shales and carbonaceous marls characteristics stratigraphic traps which formed by transgression and by onlap on paleohighs were sealed and potentially available at 97 million years ma before present structural traps related to early cretaceous extension were also sealed around 97 ma on the contrary traps formed by folding and thrusting during the alpine orogeny only formed during the last 50 ma the timing of gas generation and migration was determined by one and two dimensional basin modeling in one well and along a cross section the modeling results indicated that during the period between 90 and 42 ma large volumes of gas were generated from the carboniferous source rocks comparison with the age of stratigraphic and structural traps showed that stratigraphic and normal fault traps were potentially available for the entire volume of generated gas and that the other structural traps associated with alpine orogeny were available only for gas generated and or re migrated during the last 50 ma the evaluation of this new play results in the conclusion that the western black sea region is worthy of further exploration for conventional accumulations of thermogenic gas

thermal basin modelling of the arauco forearc basin south central chile heat flow and active margin tectonics abstract the arauco basin is part of the coastal forearc domain in south central chile during its evolution since the late cretaceous it was subject to multiple deposition cycles and the erosion of lower bathyal to beach and lagoon sediments these different environments were established in alternating accretional and erosive subduction tectonic settings along the south andean active margin whereas the general development is well understood inconsistencies arise regarding the origin of the high thermal maturity of eocene coals and the estimates of vertical movements of the whole area during the cenozoic thermal modelling of this forearc basin provides new insights regarding its thermal evolution and evaluation of the magnitudes of subsidence and inversion results are based on the analysis of coal samples from surface outcrops mines and drill cores of ten onshore wells from enap sipetrol newly derived vitrinite reflectance vr r measurements indicated a temperature in the range of 135 150 c for the oldest sediment unit of the arauco basin which was reached in post eocene times furthermore 1d basin modelling techniques indicate scenarios that could explain the coalification values in the basin s sediments the models were calibrated against vr r data from drill core samples supplied by enap sipetrol a miocene and an oligocene subsidence inversion scenario were considered while neither could be securely discarded based on the modelling results furthermore it can be shown that the current thermal maturity was not reached by an increased heat flow hf or a deep subsidence only consequently a structural inversion accompanied by the erosion of 3 0 0 4 km depending on the locality in combination with a high hf of 64 4 mw m 2 is the best explanation of the available data the hf which is high for a forearc setting can be attributed to the increased temperature of the relatively young subducted nazca plate and an additional influence of ascending hot fluids from the subduction zone the maximum temperature gradient inferred is

integrating geophysical and geostatistical techniques to map the spatial variation of clay abstract the development of subsoil models represents an important aspect of land resource evaluation because they can provide an accurate description of the spatial variability in soil properties although direct soil sampling provides the best information in terms of soil properties sample density is rarely adequate to accurately describe the horizontal and vertical variability of the physical properties of soil geophysical methods such as ground penetrating radar gpr and electromagnetic induction emi sensors provide rapid non invasive and exhaustive ways for subsoil characterization moreover geophysical methods can be integrated with geostatistics to map soil properties this study investigates the capability of geostatistics to incorporate auxiliary geoelectrical information for the prediction of soil properties the prediction model of clay content used was kriging with external drift ked with emi and gpr data as auxiliary information soil clay contents were computed for a 1 1 m grid maps at two depths 0 0 20 m and 0 20 0 40 m the spatial trend map and the standard error maps were shown separately maps of the clay content at the two depths were compared with the ordinary kriging estimates through cross validation the results showed that the model using the auxiliary variables can be preferred to univariate kriging in terms of correlation between true and estimated values and capability of interpretation of spatial variability

petroleum generation and accumulation in the golfo san jorge basin argentina a basin modeling study abstract the golfo san jorge basin located in patagonia is very important for the oil and gas production of argentina in spite of the long history of exploration and production few geochemical studies were performed until now for this study a set of possible source rocks was analyzed by organic geochemical and petrographical methods the samples of the pozo d 129 fm range from mature to overmature and contain from less than 0 5 to 2 45 toc there is some evidence indicating an algal origin of the more hydrogen rich kerogen present in part of the basin almost all the samples of pozo anticlinal aguada bandera and pozo cerro guadal fm are overmature toc values range from less than 0 5 to 2 5 the maturation of source rocks and generation expulsion and migration of hydrocarbons was evaluated by means of 1d and 2d basin models the 1d models constructed for the western part of the basin and 2d models applied for the eastern part both indicate maximum burial in miocene times the thickness of the tertiary at times of maximum burial ranged from 1000 to 1500 m and the generally small tertiary thickness now present in the fold belt region is assumed to be the result of erosion the main tectonic inversion took place in the late neogene the models strongly suggest that a magmatic event between 20 and 30 ma combined with the maximum burial at miocene times produced a very important pulse in hydrocarbon generation within the major part of the basin dated intrusive and extrusive magmatic rocks extended all over the basin account for this period of elevated heat flow migration pathways are extensively discussed for the 2d model probably major faults acted as important conduits for petroleum

thermal history hydrocarbon generation and migration in the horn graben in the danish north sea a 2d basin modelling study in this study a 2d basin model has been built along a transect crossing the horn graben in wnw ese direction the aim of the investigation was to improve the understanding of the thermal evolution of the basin and its influence on possible petroleum systems the 2d model of the subsurface is based on one seismic line and data from two exploration wells both wells td ed in triassic sediments the updoming of the ringkobing fyn high began during late carboniferous early permian at the end of the permian the horn graben became active due to regional extension the subsequent sedimentation history from triassic to date is well recorded by well reports a matter of debate has been whether or not significant amounts of pre permian sediments exist in this area of the north sea since organic material rich paleozoic sediments serve as source rocks in widespread areas of north germany and the southern north sea it would be of great importance to know whether the same deposits exist in the horn graben nielsen et al bull geol soc denmark copenhagen 45 1 10 1998 introduced a model which shows paleozoic sediments covering the basement at a maximum depth of 6 5 km assuming paleozoic sediments are underlying the permian salt deposits there should be an active petroleum system present the 2d model includes the paleozoic source rock and tries to explain why two exploration wells have not found petroleum

profiles of chloride in matrix porewater as natural tracer for matrix diffusion in crystalline rocks abstract matrix porewater from low permeable grimsel granodiorite was successfully characterised using indirect methods applied to originally saturated core samples core samples were taken from a 17 m long borehole originating from a tunnel of the grimsel test site into the crystalline bedrock intersecting a tectonic shear zone with a water conducting fracture matrix porewater chloride profiles on the meter scale were determined on both sides of the water conducting fracture to evaluate transport processes within the bedrock formation a series of diffusive model calculations were performed which to fit the porewater data boundary and initial conditions were varied according to the geological conditions whereas other required parameters such as the connected porosity and pore diffusion coefficients were determined by laboratory experiments on the cores and extrapolated to in situ conditions the main conclusions can be summarized as follows 1 chloride porewater profiles at the meter scale can be simulated using diffusive transport models this provides evidence that diffusive exchange with active fractures occurs over a range of a few meters in the low permeable crystalline bedrock 2 the best fit of the diffusion profile was achieved by a model approach which takes asymmetric initial cl concentrations into account this indicates that prior to the activation of the present water conducting fracture the porewater system in the bedrock was already active showing a concentration gradient in chloride 3 the water conducting fracture was activated at least between 850 and 1700 years before present with a best fit 1200 years before present and 4 the hydraulic were affected by the construction of the rock laboratory 20 years ago resulting in a rapid dilution of the fracture groundwater by advection

hydrocarbon expulsion model and its application to niigata area japan a one dimensional process response type model has been set up to simulate geologic processes of compaction heat transfer source rock maturation and hydrocarbon generation and expulsion during a basin s development the model can be used to calculate the quantity of oil and or gas expelled from a source rock under certain conditions although the model simplifies chemical and physical conditions within sedimentary rocks it may be used as a first approximation in geologic reconstructions of sedimentary basins when applied to the niigata area japan the model predicted the most significant parameters associated with hydrocarbon expulsion including the rate of burial and the quantity of hydrocarbons generated the model also revealed that the time of hydrocarbon expulsion varied from place to place even within the small northern niigata basin major petroleum fields formed when expulsion favorable timing coincided with the development of structure thus a realistic estimate of the timing of expulsion is a key to hydrocarbon exploration

thermodynamic analysis and simulation of coal metamorphism in the fushun basin china abstract taking the fushun basin as an example this paper analyses the relation of coal metamorphism to the normal geothermal field and additional geothermal field and establishes the thermodynamical model for the paleogeothermal field and corresponding coal metamorphism of the basin the 2 d simulation of the superimposition of coal geothermal metamorphism and telemagmatic thermal metamorphism has also been preliminarily accomplished the computer simulation results have shown that the coal formed in the paleogene in the fushun basin had an ro m value of only 0 3 and the intrusion of diabase sills in the later oligocene increased the coal rank to the low metamorphism stage ro m 0 5 1 0 it has been found in the simulation that the way in which the thermal flow in basement rock is controlled using the results from paleogeothermal structural analysis is obviously better than the method in which a value is artificially selected for the thermal flow according to the basin basement in addition the former can be used to study the variation of ro m itself so it is also better than the method to perform back confining analysis using ro m values

thermal and compaction processes in a young rifted basin containing evaporites gulf of lions france the gulf of lions northwestern mediterranean is a young oligocene miocene rifted basin characterized by the presence of a thick evaporitic sequence observed data surface heat flow well temperatures geopressures below the evaporites crustal thinning are used to model 1 the basin forming mechanisms and 2 the intrasedimentary processes that influence the temperature history and thus the maturation of source rocks a two dimensional finite difference basin model temispack simulates the sedimentation compaction and overpressures related to the low permeability of the post rift sequence the heat transfer from the rifted lithosphere into the sediments and the level of maturation by using a kinetic approach the classic passive margin model which relates the history of heat flow and the rate of subsidence to a uniform thinning factor yields subsidence and heat flow predictions that agree with observations the recently accelerated subsidence observed in the deep margin is probably an effect of recent regional compression rather than the consequence of alternative rifting mechanisms the history of maturation of organic matter was influenced by the variation of the regional heat flow due to the rifting the effect of sedimentation or blanketing and the variability of the lithologies and porosities the undercompaction of sediments underlying the evaporites is accounted for by the model which suggests that hydraulic fracturing is taking place at present in the overpressured sediments fluid flow associated with the compaction disequilibrium has negligible thermal effect undercompacted shales below the evaporites have lower thermal diffusivity and thus higher temperatures which has a significant effect on maturation

markov chain simulation of soil textural profiles abstract the spatial change of textural layers is an important feature of alluvial soils it influences soil water transport and solute movement in the field data from one or several soil profiles cannot explain processes of field water and solute movement in a large region because of spatial variability within textural layers two stochastic models the mc markov chain model and the mc ln markov chain lognormal distribution model were developed in this study using markov chain theory to simulate textural profiles of regional alluvial soils soil textural layers were divided into six types namely sand sandy loam light loam medium loam clay loam and clay the two models reflect vertical changes of textural layers of soil profiles in the research region excluding the data related to clay loam layers which are quite rare element values of tpm transition probability matrix of textural layers simulated by the mc model deviate less than 15 from measured and those by the mc ln model less than 27 the mc model shows a larger deviation in the probability distribution of textural layer thickness because the simulated textural layer thickness is inclined to be exponentially distributed but the mc ln model is consistent to the measured data which are similar to a lognormal distribution for each textural type simulated mean thicknesses of textural layers from the mc ln model deviate less than 21 1 from measured and those from the mc model less than 7 1 these two models will be useful for further constructing a regional model of field water transport with a consideration of the spatial variability of soil textural layers

modelling petroleum generation of late cretaceous dabut formation in the jiza qamar basin eastern yemen abstract the jiza qamar basin in eastern yemen is still undergoing hydrocarbon exploration and hydrocarbon potential has not been assigned yet in this study subsurface samples from two onshore and offshore wells were collected to characterize the source rocks of dabut formation and to incorporate into basin modelling in order to know and determine the timing of petroleum generation and expulsion of the dabut source rocks based on organic geochemical analysis the dabut sediments have variable toc content in the range of 0 5 2 5 wt indicating fair to good source rock generative potential the organic matter of dabut source rock is dominated by type iii kerogen with minor mixed iii ii kerogen contributions and is thus considered to be mainly gas prone and some oil prone this is supported by hi values in the range of 50 212 mg hc g toc vitrinite reflectance in the range of 0 63 0 88 ro and pyrolysis tmax in the range of 427 454 c generally indicate that the dabut source rocks contain mature organic matter one dimensional basin modelling was performed to analyse the hydrocarbon generation and expulsion history of the dabut source rocks in the jiza qamar basin based on the reconstruction of the burial and thermal maturity histories in order to improve our understanding of the hydrocarbon generation potential calibration of the model with measured vitrinite reflectance ro and borehole temperature bht data indicates that the paleo heat flow was constant during the late cretaceous paleogene but increased during the late paleogene neogene and then decreased exponentially from neogene to present day the modelled maturity history predicts that the oil generation 0 5 ro in the dabut source rock began from about 56 ma to 42 ma and the peak hydrocarbon generation 0 86 ro occurred approximately from 14 ma to 13 ma these models also indicate that the main phase of oil generation was at 56 ma to 25 ma whereas the main phase of gas generation began from about 25 ma to 14 ma and still generated in the present day

basin modeling of tadla basin morocco for hydrocarbon potential the tadla basin morocco is the easternmost major structural subdivision of the meseta south of the central massif after the basin remained relatively stable through the paleozoic movements during the variscan orogeny divided the basin into two subbasins a western subbasin where compressional forces formed large anticlines and an eastern subbasin where intense folding and faulting are associated with uplift and erosion the sedimentary basin fill includes numerous organic shales which provide the source beds also deposited were numerous shallow water to continental clastics and to a lesser extent carbonates providing several possible reservoir rocks for hydrocarbons the results from computer modeling show that the chief formations of hydrocarbon generation are carboniferous and silurian most of these formations may have generated hydrocarbons before variscan movements which probably destroyed preexisting oil and gas traps the only source rocks in the generation stage from mesozoic to the present are the upper visean shales the western part of the tadla basin was the most favorable area for the generation and maturation of hydrocarbons of the upper visean shales

numerical modelling of burial and temperature history as an approach for an alternative interpretation of the bramsche anomaly lower saxony basin the lower saxony basin germany is one of the several sedimentary basins within the central european basin system in its southwestern part anomalously high maturity of organic matter has been observed to reach 4 5 vrr in upper jurassic and lower cretaceous sedimentary rocks in an area which coincides with a magnetic and a positive gravimetric anomaly this anomaly was often interpreted as the consequence of a deep seated igneous intrusion the so called bramsche massif however results obtained from calibrated numerical modelling are not in accordance with this scenario instead a burial by approximately 4 km of now eroded cretaceous rocks was revealed to be the probable cause for the anomaly data and modelling results from six boreholes and two pseudo wells support this view

2d petroleum system analysis of the tarfaya basin on offshore morocco north africa abstract this study presents a 2d basin model along a transect crossing the on and offshore tarfaya basin morocco in se nw direction the aim of the project is to investigate the thermal evolution of the basin fill and its influence on the petroleum system the modelling is based on a recently interpreted seismic section and includes new and published geochemical and organic petrological data from five wells core samples and cuttings provide information which was used for thermal calibration of the model vitrinite reflectance in the jurassic offshore basin fill reaches more than 1 the modelled subsidence history in combination with kinetic and geochemical data were used to model hydrocarbon generation in order to investigate the temperature hydrocarbon generation and its timing two 1d geohistory curves were extracted one for the onshore inner shelf and one for the offshore deep water area the modelling results suggest that deepest burial in the modern offshore area occurs at present day whilst deepest burial in the onshore area occurred during the oligocene depending on the location on the inner shelf based on the burial and thermal evolution significant hydrocarbon generation from lower jurassic source rocks took place from the early cretaceous until the neogene in the offshore area in the onshore area petroleum generation ceased in the late cretaceous as salt deposition may play an important role in the thermal history in the tarfaya basin a second model including salt was built indicating increased early cretaceous hydrocarbon generation in the offshore area

numerical modelling of abnormal fluid pressures in the navarin basin bering sea abstract the navarin basin located in the bering sea alaska is composed of three major units 1 a thick late eocene and oligocene overpressured shaly section 2 a miocene sandy section and 3 a late miocene to pliocene section characterized by high porosity and a possible zone of abnormal pressure due to the presence of diatomaceous shales the basin was affected by folding during the early stages of basin filling whereas strike slip faulting occurred until mainly miocene time to model the fluid flow and compactional history of the basin a cross section was used controlled by four wells for which porosity and pressure data were available a first approximation used a one dimensional model to bracket the range of parameter values which govern the fluid flow compaction equations using data from the arco cost no 1 well a sensitivity analysis then allowed 1 determination of the best set of parameters of the model 2 the behaviour of each parameter and its relative importance to be assessed and 3 the role of an erosion event in influencing the evolutional history of the basin to be tested with a slight readjustment of the parameters to allow for lateral fluid flow a two dimensional model was then constructed the model reproduced correctly the variation of porosity and pressure data with depth for the four wells the main overpressure in the deeper part of the basin arose during the earliest stages of basin filling by shale because of strong undercompaction in the shallower part of the basin high porosity values were obtained in agreement with the data whereas some overpressure was developed in association with the undercompaction and low permeability of the diatomaceous shales different assumptions have been investigated such as the permeable or impermeable nature of faults the role of a rock fracturing coefficient and the anisotropy of permeability but because of the location of the wells on structural highs no major variations were observed relative to the well data so that the impact of such different assumptions on the total dynamic history of the basin cannot be determined from presently available data

thermal maturity history and petroleum generation modelling for the upper jurassic madbi source rocks in the marib shabowah basin western yemen abstract widely exposed in the marib shabowah basin the early upper jurassic madbi formation is divided into two units lam and meem youngest to oldest believed to be major source rocks the madbi source rocks are characterized by relatively high total organic carbon contents toc ranging from 0 5 to 10 0 wt meeting the standard as a fair to excellent source rock generative potential they contain type ii kerogen grading to mixed type ii iii kerogens and type iii kerogen with hi values between 40 and 620 mg hc g toc vitrinite reflectance values range from 0 41 to 2 61 r o indicating sufficient thermal maturity for both oil and gas generation burial thermal history models indicate that the upper jurassic madbi source rocks passed the peak of oil generation stage and convert the oil to dry gas in the late jurassic to late cretaceous time oil generation began immediately after deposition in the late jurassic time 150 145 ma and maximum rates of oil with significant gas have been generated during late cretaceous time 110 65 ma the peak gas generation occurred during the early tertiary the modelled hydrocarbon expulsion evolution suggests that the timing of hydrocarbon expulsion from the madbi source rocks began in the early cretaceous 140 ma persisted to present day the modelling results also indicate that the peak hydrocarbon generation and expulsion from madbi source rocks in the studied area occurs well after deposition of the seal rock and formation of traps ensuring entrapment and preservation of migrated hydrocarbons

hydrologic issues associated with nuclear waste repositories significant progress in hydrology especially in subsurface flow and solute transport has been made over the last 35 years because of sustained interest in underground nuclear waste repositories the present paper provides an overview of the key hydrologic issues involved and to highlight advances in their understanding and treatment because of these efforts the focus is not on the development of radioactive waste repositories and their safety assessment but instead on the advances in hydrologic science that have emerged from such studies work and results associated with three rock types which are being considered to host the repositories are reviewed with a different emphasis for each rock type the first rock type is fractured crystalline rock for which the discussion will be mainly on flow and transport in saturated fractured rock the second rock type is unsaturated tuff for which the emphasis will be on flow from the shallow subsurface through the unsaturated zone to the repository the third rock type is clay rich formations whose permeability is very low in an undisturbed state in this case the emphasis will be on hydrologic issues that arise from mechanical and thermal disturbances i e on the relevant coupled thermo hydro mechanical processes the extensive research results especially those from multiyear large scale underground research laboratory investigations represent a rich body of information and data that can form the basis for further development in the related areas of hydrologic research

sensitivity analysis in thermal and maturity modelling abstract knowledge about the present and past thermal structure in sedimentary basins is central to understanding the evolution of sedimentary basins and for success in hydrocarbon exploration the possibilities and limitations in resolving the palaeothermal structure by inversion of downhole temperature and vitrinite reflectance data are discussed by means of an example from the danish central trough the prediction of petroleum generation is sensitive to uncertainties in source rock temperature history and the kinetic parameters of kerogen degradation the effects of uncertainties in surface temperature heat flow depth of burial thermal resistivity structure and kinetic parameters are investigated using a previously developed stochastic method regarding the state of petroleum generation the number of safe statements based on numerical modelling essentially are reduced to three 1 the source rock has not generated significant amounts of petroleum 2 the source rock has released most of its petroleum potential or 3 the source rock has released some of its petroleum potential in the latter case the state of petroleum generation is best described by a cumulative distribution function of source rock transformation which reflects the effects of uncertainties in the basic modelling parameters the probability of occurrence of a particular transformation ratio value like those derived in traditional deterministic modelling is zero an example of application from the danish central trough is given

characterisation of pore water in crystalline rocks abstract the mass of pore water present in the rock matrix of a crystalline rock mass is significant and its influence on fracture groundwater and future deep repositories needs to be understood yet the rock matrix has a hydraulic transmissivity generally well below 10 10 m 2 s 1 inhibiting sampling of pore water by conventional sampling techniques various innovative techniques for the chemical and isotopic characterisation of pore water in crystalline rocks are applied and evaluated direct sampling of pore water was facilitated by collecting seepage water in a specially designed borehole located at a depth of 420 m in the aspo underground research laboratory aspo hrl sweden over a period of 7 5 a during the entire time span seepage waters collected from different sampling sections showed constant but individual chemical and isotopic compositions compositional differences compared to nearby fracture groundwaters indicate that the collected waters originated from the low permeability rock mass without mutual influence via more conductive microfractures within the metre scale they are interpreted as representing pore water in a transient state of diffusive interaction with different types of old palaeowaters which have periodically characterised the fracture network at the aspo hrl over geological times thousands to hundreds of thousands of years pore water compositions derived by indirect methods out diffusion and diffusive isotope equilibration experiments from originally saturated drillcore samples collected at the laxemar and forsmark sites sweden can be interpreted within a wider palaeohydrogeological framework the chemical and isotope compositions of the pore water show distinct trends related to rock type and with depth becoming more saline at greater depth at both sites concentration gradients established between pore water and fracture groundwater commonly coincide with higher fracture frequency and transmissivity in the host rocks differences developed in the attainment of near steady state conditions between pore water and fracture water from laxemar and forsmark support a different hydrogeological and therefore hydrogeochemical evolution at least during holocene times the observed compositional differences between pore water and fracture groundwater support diffusion dominated solute transport in the low permeable rock masses which is consistent with measured and experimentally derived hydraulic properties from the present investigations it can be concluded that in such rock masses the diffusion accessible porosity extends over significant distances of at least metres to tens of metres

oil and gas play maps in exploration and assessment geologic note play summary maps show the superimposed boundaries of favorable areas for all key geologic controls of oil and gas occurrence source migration reservoir trap timing seal preservation and recovery for a genetic group of prospects or fields these maps are invaluable for high grading the best areas thereby reducing exploration risks and for quantitatively estimating hydrocarbon volume and success factors in both prospect and play assessment play summary maps are based on standard exploration map suites but demand a systematic integration of all the essential geologic controls none of which can safely be ignored

dynamic hydrocarbon predictions for the northern part of the danish central graben an integrated basin analysis assessment abstract geohistory thermal history source capacity and oil generation have been examined in the north west part of the danish central graben using a one dimensional fluid flow compaction model the burial history suggests that this part of the danish central trough developed through three stages of subsidence a late jurassic differential stage a late cretaceous early tertiary uniform stage and a late miocene quaternary uniform stage pseudo wells drilled on seismic sections in areas without well data are used to improve the spacial distribution of wells the palaeotemperature and palaeoheat flow have been modelled by inversion of vitrinite reflectance data the inversion was carried out on wells with available vitrinite reflectance data and was based on known bottom hole temperature some temperature measurements with depth and the surface temperature the thermal history assessed by inversion of vitrinite reflectance data gives a consistently cooler past the available data s resolution of the thermal history is discussed the modelled maturation history of the upper jurassic shale in terms of vitrinite reflectance suggests that the shale reached maturity some 5 50 ma ago a geochemical study of the upper jurassic shales shows that these shales contain a mixture of type ii and type iii kerogens and have good to excellent source capacity modelling of the hydrocarbon generation data indicates that the peak generation took place some time between 10 ma bp and the present day possible migration paths are determined from modelled excess fluid pressure and four areas of possible accumulation of hydrocarbons are indicated the hydrocarbon potential of the areas are evaluated and an area along the eastern boundary fault between the tail end graben and the ringkobing fyn high is suggested as a new target area for further exploration

carboniferous coals of the zonguldak basin northwest turkey implications for coalbed methane potential we investigated the carboniferous coals in the zonguldak basin northwest turkey using a multidisciplinary approach including petrographical and geochemical analyses gas adsorption and gas content measurements artificial maturation experiments on selected coals and one dimensional 1 d modeling of the basin evolution and hydrocarbon generation the main emphasis was set on the definition of coalbed methane cbm generation capability and adsorption capacity of the coals considering these properties of coals and the amount and composition of gas within the coal seams we carried out a comprehensive evaluation of the cbm potential of the basin three areas in the basin namely armutcuk zonguldak and amasra were investigated separately for their cbm potential from the standpoint of petroleum oil and or gas generation the coals in the armutcuk and amasra areas are located within the oil generation window the coals of the zonguldak area are located within the oil and gas generation window computer aided basin modeling using a basin specific kinetic data set of hydrocarbon generation from coals suggests that significant quantities of gas have been generated only in the zonguldak area modeling results also indicate that major gas generation from the base of the westphalian a kozlu formation in the zonguldak area occurred between 80 and 42 ma during the late cretaceous early eocene prior to basin inversion that started at 42 ma and continues at present the predicted amount of generated coalbed gas from coal seams in the gas generation zone is several times higher than the adsorption capacity of the respective seams a certain amount of this gas controlled by the adsorption capacity is stored within the coal seams where it is generated gas generated in excess of storage capacity obviously would have been expelled from the coal part of the expelled gas is accumulated in coal seams located above the gas generation zone however the coal seams within and above the gas generation zone are undersaturated with respect to their adsorption capacity the undersaturation is probably caused by remigration of gas that is desorbed because of pressure decrease during basin inversion of more than 2500 m 8203 ft over the last 42 m y the rest of the gas generated within the coal seams and expelled first because of the overflow of adsorption capacity and then because of the desorption during basin inversion has either migrated to source conventional gas reservoirs or has been lost to the surface during basin inversion because the basin has not been explored for conventional gas reservoirs a conclusive mass balance cannot yet be performed despite basin inversion and remigration of gas some coal seams still contain gas amounts of up to 10 cm 3 g of coal indicating a cbm potential

basin modelling a new comprehensive method in petroleum geology abstract integrated basin modelling is used to understand and reconstruct the geological and thermal evolution of a sedimentary basin to quantify this information and hence to derive among other results the history of generation migration and accumulation of petroleum this new methodical approach is rapidly gaining world wide recognition throughout the geo scientific community because it offers two distinct advantages when addressing geological problems firstly it enables a logical quantitative treatment of very complex interrelated geological processes and secondly it permits these processes to be examined on the basis of an absolute geological time scale the prerequisites for basin modelling are 1 the translation of logical and consistent geological concepts into numerical form and then into suitable computer programs and 2 the application of these programs using high speed computers with large memories using such an approach is an important part of modern petroleum exploration because 1 1 provision is made for total coverage of the basin by allowing extrapolation to non drilled often deeper parts of the basin accessible only by using seismic data 2 2 a three dimensional view of the basin can be constructed and followed through geological time 3 3 an internal logic is utilised which is consistent with physical and chemical laws 4 4 geological geophysical and geochemical data are integrated and modelled iteratively and therefore control each other this paper shows the rapidly widening scope of basin modelling and points out some of the present day limitations and necessary research directions for the future it describes concepts for modelling of tectonic processes and for simulating expulsion of liquid petroleum

petroleum generation modeling of the organic rich shales of late jurassic early cretaceous succession from mintaq 01 well in the wadi hajar sub basin yemen late jurassic early cretaceous shales of the naifa safer and madbi formations were studied to evaluate source rock characterization the results of the source rock were then incorporated into basin modeling to understand the timing of hydrocarbon hc generation and expulsion the late jurassic early cretaceous shales have low to high organic matter with total organic carbon toc values in the range of 0 50 28 01 indicating fair to excellent source rock potential main oil and gas are anticipated to be generated from the naifa safer and lam shale samples with types i and or ii and types ii iii kerogens in contrast the meem samples are dominated by type iii kerogen hydrogen index hi 200 mg hc g toc and are thus considered to be gas prone the late jurassic early cretaceous shale samples have temperatures of maximum pyrolysis yield tmax in the range of 337 515 c consistent with immature to post mature stages the tmax data also indicate that the safer and madbi shale samples h

estimating tectonic history through basin simulation enhanced seismic inversion geoinfomatics for sedimentary basins summary a data assimilation approach is demonstrated whereby seismic inversion is both automated and enhanced using a comprehensive numerical sedimentary basin simulator to study the physics and chemistry of sedimentary basin processes in response to geothermal gradient in much greater detail than previously attempted the approach not only reduces costs by integrating the basin analysis and seismic inversion activities to understand the sedimentary basin evolution with respect to geodynamic parameters but the technique also has the potential for serving as a geoinfomatics platform for understanding various physical and chemical processes operating at different scales within a sedimentary basin tectonic history has a first order effect on the physical and chemical processes that govern the evolution of sedimentary basins we demonstrate how such tectonic parameters may be estimated by minimizing the difference between observed seismic reflection data and synthetic ones constructed from the output of a reaction transport mechanical rtm basin model we demonstrate the method by reconstructing the geothermal gradient as thermal history strongly affects the rate of rtm processes operating in a sedimentary basin variations in geothermal gradient history alter the present day fluid pressure effective stress porosity fracture statistics and hydrocarbon distribution all these properties in turn affect the mechanical wave velocity and sediment density profiles for a sedimentary basin the present day state of the sedimentary basin is imaged by reflection seismology data to a high degree of resolution but it does not give any indication of the processes that contributed to the evolution of the basin or causes for heterogeneities within the basin that are being imaged using texture and fluid properties predicted by our basin rtm simulator we generate synthetic seismograms linear correlation using power spectra as an error measure and an efficient quadratic optimization technique are found to be most effective in determining the optimal value of the tectonic parameters preliminary 1 d studies indicate that one can determine the geothermal gradient even in the presence of observation and numerical uncertainties the algorithm succeeds even when the synthetic data has detailed information only in a limited depth interval and has a different dominant frequency in the synthetic and observed seismograms the methodology presented here even works when the basin input data contains only 75 per cent of the stratigraphic layering information compared with the actual basin in a limited depth interval

understanding of hc migration in sedimentary basins present state of knowledge abstract great advances were made during the decade of 1975 1985 in the understanding of hc migration by establishing that the main mechanisms were polyphasic flow whatever its stage and that migration in solution in water and or by molecular diffusion was insignificant except for methane ethane and benzene research is now focusing on points which still have not been satisfactorily answered such as 1 1 behaviour of source rocks during hc expulsion the main driving force for fluid expulsion has been recognized to be excess fluid pressure within the source rock with respect to its surrounding environment of permeable beds the pressure build up is due mainly to accommodation by the fluids of part of the mechanical stresses which are exerted on the rock mainly sedimentary load but also stresses developed by tectonics to thermal expansion of water and to hc formation from kerogen in response to increasing temperatures however it is not clear whether or not petroleum expulsion proceeds preferentially along oil wet networks kerogen or oil wet mineral surfaces nor it is not clear whether or not microfracturing provoked by an internal fluid pressure higher than allowed by the mechanical strength of source rocks is necessary for hc expulsion 2 2 modifications of the compositions of hc phases e g oil versus gas or the distribution of biomarkers during migration and losses of hydrocarbons along the migration pathways although careful observations of natural sample series and also experimentation have been done no clear picture has emerged for the moment however compositional effects seem to be due more to changes in thermodynamic conditions along migration pathways which provoke inter alia hydrocarbon phase separation retrograde condensation than to differential retention by mineral surfaces it is likely that while careful observations on a large variety of source rock samples are needed to more clearly understand source rocks functioning progress in understanding hc migration will come increasingly from modeling and experimentation models which mathematically simulate natural processes are necessary to help the human mind in handling such complex phenomena and therefore are of precious help to focus research on the most important points they replace migration in its geological and historical dimensions with numerical or conceptual tools while observation only describes the present state models are also the tools by which knowledge on migration can be applied to exploration problems however quantitative applications of models require numerous and precise geological data that are difficult to gather at early stages of exploration in the field of experimentation it will be easier to design crucial experiments now that hc migration mechanisms are better understood thanks to experimentation it should also be possible to validate models however so as to reach such aims substantial progress has to be made in the technology of experimental systems

diffusion in the matrix of granitic rock field test in the stripa mine three field experiments in granitic rock were performed at 360 m depth in a mine to investigate diffusion in the undisturbed rock matrix the results from all three experiments showed that tracers had migrated through the disturbed zone close to the injection hole and a distance into the undisturbed rock matrix these results show that it is possible for dissolved compounds to migrate into the rock matrix in its natural stress environment diffusivities and hydraulic conductivities obtained in this in situ experiment compare well with those obtained in laboratory experiments

comparative organic petrology of interlayered sandstones siltstones mudstones and coals in the upper carboniferous ruhr basin northwest germany and their thermal history and methane generation in the coal mining ruhr area upper carboniferous rocks ca 4000 m consist of interlayered sandstones siltstones mudstones and coals they were deposited in a tropical paralic environment where alternating fluvial sedimentation occasional marine ingressions and swamp growth resulted in an irregular cyclic succession the total sedimentary package contains on an average 6 vol of organic matter about 70 vol of the organic matter occurs in coal seams the rest as dispersed organic matter in clastic rocks the organic matter is autochthonous in the coals and allochthonous in associated sandstones and siltstones it consists of about 70 vitrinite 20 inertinite and 10 liptinite the overall maceral group composition is the same for coals and dispersed organic matter this surprising similarity is caused by a nearly exclusive input of land plant derived organic matter to swamps and fluvial systems and a similar degree of preservation highest average liptinite contents of total macerals were found in unrooted mudstones highest average inertinite contents in coarse grained siltstones and highest average vitrinite percentages in sandstones

deep petroleum occurrences in the lower kura depression south caspian basin azerbaijan an organic geochemical and basin modeling study abstract high sedimentation rates as much as 2500 m ma during pliocene pleistocene with a resultant undercompacted section as thick as 10 000 m and lower than normal geothermal gradients are the main characteristics which have created all the means for generation and preservation of oil at deep layers in the lower kura depression oils collected from eight different oil fields for analyses seem to have originated from a common source rock which probably is clastic deposited in relatively subanoxic to suboxic transitional marine environment receiving low to moderate input of terrestrial organic matter oils from shallow a computer aided basin modeling study has been carried out to outline the spatial variation of the oil window and thus help in further identification of possible source rocks for the reservoired oil in the lower kura depression results suggest that the potential hydrocarbon source horizons of the miocene and pliocene red bed series of the so called productive succession are even at depocenter areas immature with respect to oil generation and thus are very unlikely to have been source rocks for the reservoired oils however the oligocene lower miocene maykop rocks are marginally mature to mature depending on locality and the eocene and older rocks are mature with respect to oil generation at all representative field locations oil generation commenced at the end of pliocene and continues at present at depths between 6000 and 12 000 m an unusually deep 10 000 m oil window in the depocenter areas has been caused by the depressed isotherms due to extremely high sedimentation rates up to 3000 m ma for the last two million years the main phase of oil generation is taking place at depths greater than what most of the wells in the study are have reached

basin analysis predictions of known hydrocarbon occurrences the north sea viking graben as a test case abstract basin analysis can assimilate structural burial and thermal histories to predict hydrocarbon prone zones in speculative areas the validity of the modelling approach was field tested in the north sea viking graben an area for which good data are available a recent birps deep seismic reflection profile across tectonic strike of the graben was interpreted and depth converted with good well control the burial and structural histories were determined by backstripping the chronostratigraphic layers using a one dimensional fluid flow compaction model on pseudo wells after removal of each sequence the section was manually reconstructed the thermal history was examined using thermal indicator tomography extensional models and calculations of depth to detachment lack of resolution required that three different paleo heat flow trends be tested to encompass the range in variability a gradual warming trend a constant heat flow through time and a low heat flow until the cretaceous tertiary boundary where a heat pulse occurred basement subsidence extension depth to detachment calculations and thermal indicator inversions all suggest that the uk side of the graben has developed differently to the norwegian section the generation modelling predicts the position of the oil window in the cross section the areas where this window enveloped the draupne formation kimmeridge clay source rock broadly correlate with the positions of the gullfaks statfjord and thistle oilfields of the uk sector however in the norwegian sector the draupne formation was generally overmature except in the area around the troll oilfield predicted middle to late cretaceous generation in the rift axis may have caused updip oil migration towards the horda platform the correct prediction of oil prone zones validates the use of quantitative basin analysis as a tool for evaluating frontier areas where data are limited

a large scale flow and tracer experiment in granite 2 results and interpretation water and tracer flow has been monitored in a specially excavated drift in the stripa mine several new experimental techniques and equipment were developed and used the whole ceiling and the upper part of the walls were covered with 375 individual plastic sheets where the water flow into the drift could be collected eleven different tracers were injected at distances between 11 and 50 m from the ceiling of the drift the flow rate and tracer monitoring was kept up for more than 2 years the tracer breakthrough curves and flow rate distributions were used to study the flow paths velocities hydraulic conductivities dispersivities and channeling effects in the rock in a companion paper the experimental design and performed experiments are described the present paper describes the interpretation of flow and tracer movement in the rock outside the drift the tracer movement was measured by the more than 160 individual tracer curves the tracer experiments have permitted the flow porosity and dispersion to be studied the possible effects of channeling and the diffusion of tracers into stagnant waters in the rock matrix and in stagnant waters in the fractures have also been addressed

quantitative dynamic geology of the pineda anticline wyoming u s a an application of a two dimensional simulation model abstract vertical line fault behavior is allowed for within a two dimensional basin simulation model the fault model permits relative movement of the faulted blocks normal and reverse and open or closed fluid flow conditions simultaneous simulation of a number of vertical line faults horst and graben is included making the 2 d model of great flexibility application of this model to the pinedale anticline green river basin wyoming showed that the model can 1 simulate sedimentation processed including normal sedimentation erosion and hiatus 2 simulate structural development including general structural styles anticlinal or synclinal faults and horst and grabens and 3 predict the geothermal history and the evolution of geological parameters such as formation temperature fluid pressure abnormal pressure and vitrinite reflectance from these parameters maturation of organic matter is assessed finally 4 the model can quantify oil generation migration and accumulation through geological time the model behaviors are shown to be consistent with downhole data taken at the present time the results can be output as graphs either in one dimension or in two dimensions providing a pictorial representation of evolution of the pinedale anticline

spatial analysis of clay content in soils using neurocomputing and pedological support a case study of valle telesina south italy the spatial analysis of soil properties by means of quantitative methods is useful to make predictions at sampled and unsampled locations two most important characteristics are tackled namely the option of using complex and nonlinear models in contrast with also very simple linear approaches and the opportunity to build spatial inference tools using horizons as basic soil components the objective is to perform the spatial analysis of clay content for validation purposes in order to understand whether nonlinear methods can manage soil horizons and to quantitatively measure how much they outperform simpler methods this is addressed in a case study in which relatively few records are available to calibrate train such complex models we built three models which are based on artificial neural networks namely single artificial neural networks median neural networks and bootstrap aggregating neural networks with genetic algorithms and principal component regression bagap we perform a validation procedure at three different levels of soil horizon aggregations i e topsoil profile and horizon pedological supports the results show that neurocomputing performs best at any level of pedological support even when we use an ensemble of neural nets i e bagap which is very data intensive bagap has the lowest rmse at any level of pedological support with hbox rmse mathrm bagap topsoil 7 2 hbox rmse mathrm bagap profile 7 8 and hbox rmse mathrm bagap horizon 8 8 we analysed in depth artificial neural parameters and included them in the appendix to provide the best tuned neural based model to enable us to make suitable spatial predictions

petroleum generation kinetics single versus multiple heating ramp open system pyrolysis some recent publications promote one run open system pyrolysis experiments using a single heating rate ramp and fixed frequency factor to determine the petroleum generation kinetics of source rock samples because compared to multiple ramp experiments the method is faster less expensive and presumably yields similar results some one ramp pyrolysis experiments yield kinetic results similar to those from multiple ramp experiments however our data for 52 worldwide source rocks containing types i ii iis ii iii and iii kerogen illustrate that one ramp kinetics introduce the potential for significant error that can be avoided by using high quality kinetic measurements and multiple ramp experiments in which the frequency factor is optimized by the kinetic software rather than fixed at some universal value the data show that kinetic modeling based on a discrete activation energy distribution and three different pyrolysis temperature ramps closely approximates that determined from additional runs provided the three ramps span an appropriate range of heating rates for some source rocks containing well preserved kerogen and having narrow activation energy distributions both single and multiple ramp discrete models are insufficient and nucleation growth models are necessary instrument design thermocouple size or orientation and sample weight likely influence the acceptable upper limit of pyrolysis heating rate caution is needed for ramps of 30 50 c min which can cause temperature errors due to impaired heat transfer between the oven sample and thermocouple compound volatility may inhibit pyrolyzate yield at the lowest heating rates depending on the effectiveness of the gas sweep we recommend at least three pyrolysis ramps that span at least a 20 fold variation of comparatively lower rates such as 1 5 and 25 c min the product of heating rate and sample size should not exceed 100 mg c min our results do not address the more fundamental questions of whether kinetic models based on multiple ramp open system pyrolysis are mechanistically appropriate for use in basin simulators or whether petroleum migration through the kerogen network rather than cracking of organic matter represents the rate limiting step in expulsion

three dimensional mapping of clay content in alluvial soils using hygroscopic water content the three dimensional 3d spatial distribution of soil clay content or texture is important to water and solute e g salt and pollutants transport studies land planning and remediation of contaminated soils however accurate soil texture analysis is costly and time consuming the objective of this study is to map the 3d spatial distribution of clay content in alluvium using easily measured hygroscopic water content data as source data a total of 542 soil samples were collected from 57 soil profiles within a piece of farmland of 1 68 ha near tai an city in the north china plain hygroscopic water content was measured for all samples but clay content was determined only for 106 randomly selected samples from 13 soil profiles clay content data of other 436 samples were derived using a recently established model for the relationship between clay content and hygroscopic water content 3d ordinary kriging was applied to map the spatial pattern of soil clay content results showed that 1 spatial correlation ranges of soil clay content are 55 0 and 1 16 m in the horizontal and vertical directions respectively and 2 the subsoil clay content is low in the northeast part of the study area while the soil layers with high clay content are mainly distributed in the upper section of soil profiles in the southern part of the study area this reflects that the fluvial deposits in the study area have a fining upward tendency cross validation showed that the 3d kriging method could effectively capture the spatial distribution characteristics of soil clay content in alluvial soils in the north china plain

representation of normal slant faults in a 2d burial history model a discussion is given of the impact of normal slant faults on basinal structure compaction fluid overpressure development and thermal effects in sedimentary basins faults which are hydraulically closed or open to fluid flow are examined in a dynamical two dimensional fluid flow compaction model from this numerical investigation three dominant factors characterize the effects of single and multiple faults with open or closed hydraulic behaviours i there is a difference in excess pressure for fault planes with open or shut hydraulic conditions but the neighbourhood where the effect of the fault is dominant is fairly localized to within about half a kilometre or so laterally from the fault plane ii the lateral and vertical motion of sediments between faulted blocks induces a thermal difference prior to during and post faulting which can play a role in influencing hydrocarbon generation migration and accumulation iii porosity retention and permeability modification by fault development could influence hydrocarbon exploration decisions regarding sealing migration pathways and fluid retention the general patterns of slant fault effects described here should prevail in most geological situations because the numerical experiments are designed to illuminate sharply the dominant response characteristics within the framework of simplified situations

origin of marginal basins of the nw pacific and their plate tectonic reconstructions abstract geometry of basins can indicate their tectonic origin whether they are small or large the basins of bohai gulf south china sea east china sea japan sea andaman sea okhotsk sea and bering sea have typical geometry of dextral pull apart the java makassar celebes and sulu seas basins together with grabens in borneo also comprise a local dextral transform margin type basin system similar to the central and southern parts of the shanxi basin in geometry the overall configuration of the philippine sea resembles a typical sinistral transpressional pop up structure these marginal basins except the philippine sea basin generally have similar or compatible rift history in the cenozoic but there do be some differences in the rifting history between major basins or their sub basins due to local differences in tectonic settings rifting kinematics of each of these marginal basins can be explained by dextral pull apart or transtension these marginal basins except the philippine sea basin constitute a gigantic linked dextral pull apart basin system formation of the gigantic linked dextral pull apart basin system in the nw pacific is due to nne to ene ward motion of east eurasia this mainly was a response to the indo asia collision which started about 50 ma ago the displacement of east eurasia can be estimated using three aspects 1 the magnitude of pull apart of the dextral pull apart basin system 2 paleomagnetic data from eastern eurasia and the region around the arctic and 3 the shortening deficits in the large tibetan plateau all the three aspects indicate that there was a large amount 1000 to 1200 km of northward motion of the south china block and compatible movements of other blocks in eastern eurasia during the rifting period of the basin system such a large amount of motion of the eastern eurasia region contradicts any traditional rigid plate tectonic reconstruction but agrees with the more recent concepts of non rigidity of both continental and oceanic lithosphere over geological times based on these three estimates the method developed for restoration of diffuse deformation of the eurasian plate and the region around the arctic and the related kinematics of the marginal basins we present plate tectonic reconstructions of these marginal basins in global plate tectonic settings at the four key times 50 35 15 and 5 ma the plate tectonic reconstructions show that the first order rift stage and post rift stage of the marginal basins are correlated with the first order slow uplift stage and the rapid uplift stage of the tibetan plateau respectively the proto philippine sea basin was trapped as a sinistral transpressional pop up structure at a position that was 20 south of its present position at about 50 ma ago or earlier while the japan arc migrated eastward during the rifting period of the japan sea basin the shikoku basin opened and the parece vela basin widened