integrated computer aided basin modeling applied to analysis of hydrocarbon generation history in a northern italian oil field abstract the application of reaction kinetics to the analysis of hydrocarbon hc generation processes requires a detailed temperature history of potential source rocks in order to obtain optimum results the necessary accuracy can be obtained by employing integrated computer aided basin modeling techniques to simulate the depositional history resulting in a continuous record of temperatures throughout the study area the technique has been applied to the analysis of an on off structure hc generation problem in a northern italian oil field the simulation of the geologic processes shows that low sedimentation rates and more importantly the high thermal conductivities of the carbonate rocks resulted in low temperatures throughout most of the geologic history of the study area which were followed by a sudden rapid temperature increase in the off structure area during the last 6 5 ma the calculated temperature history enables an accurate determination of the hc generation history using a kinetic approach which shows how hc generation is closely controlled by the sedimentation history and structural development and which also describes its relation to trap formation it also shows why hcs are generated at very low vitrinite reflectance levels i e peak oil generation at approximately 0 6 r o determination of the hc generation rate gives additional critical information as even source rocks located in apparently good potential zones at present i e in the on structure area can be of minor importance for a trap due to slow generation rates and consequent low expulsion efficiencies

global marine gravity from retracked geosat and ers 1 altimetry ridge segmentation versus spreading rate 1 three approaches are used to reduce the error in the satellite derived marine gravity anomalies first we have retracked the raw waveforms from the ers 1 and geosat gm missions resulting in improvements in range precision of 40 and 27 respectively second we have used the recently published egm2008 global gravity model as a reference field to provide a seamless gravity transition from land to ocean third we have used a biharmonic spline interpolation method to construct residual vertical deflection grids comparisons between shipboard gravity and the global gravity grid show errors ranging from 2 0 mgal in the gulf of mexico to 4 0 mgal in areas with rugged seafloor topography the largest errors of up to 20 mgal occur on the crests of narrow large seamounts the global spreading ridges are well resolved and show variations in ridge axis morphology and segmentation with spreading rate for rates less than about 60 mm a the typical ridge segment is 50 80 km long while it increases dramatically at higher rates 100 1000 km this transition spreading rate of 60 mm a also marks the transition from axial valley to axial high we speculate that a single mechanism controls both transitions candidates include both lithospheric and asthenospheric processes

the donets basin ukraine russia coalification and thermal history the donets basin donbas is one of the major late paleozoic coal basins in the world the donbas foldbelt is an inverted part of the donets basin characterized by wnw ese trending folds and faults the age of basin inversion is under discussion large parts of the donets basin host anthracite and meta anthracite low rank coals are restricted to the western and northern basin margins vitrinite reflectance patterns along the gorlovka anticline indicate syn deformational coalification vitrinite reflectance isolines are displaced along thrusts clear evidence that main coalification predates late faulting 1 d and 2 d numerical models were applied to elucidate the factors that control coalification in the western donets basin krasnoarmeisk monocline kalmius torets depression south syncline the models indicate that the depth of the seams and the heat flow during maximum permian burial are the most important parameters the thickness of late carboniferous and permian rocks increased from the southwestern basin margin towards the basin center permian erosion along the krasnoarmeisk monocline and in the kalmius torets depression was on the order of 2 3 km more rocks were eroded southeast of the donetsk kadievka fault zone 4 5 km heat flow during maximum burial was in the range of 40 75 mw m2 heat flow in the krasnoarmeisk monocline and the kalmius torets depression increased in a northeastward direction from 40 to 55 mw m2 heat flow at the eastern edge of the kalmius torets depression and in the south syncline was in the range of 60 75 mw m2 and increased towards the southeast the resulting coalification pattern in this area was overprinted by thermal events in the northern krasnoarmeisk monocline and the south syncline these are probably related to permian magmatic intrusions coked coal occurs at the contact to presumed permian sills and dikes southwest of donetsk

syn rift evolution of the pripyat trough constraints from structural and stratigraphic modelling the pripyat trough is a late devonian rift basin it forms part of the larger pripyat dniepr donets rift system which has a length in excess of 800 km and separates the ukrainian shield from the voronezh massif the pripyat trough contains a well resolved stratigraphic sub division within the syn rift basin fill sequence which allows the duration and rate of rifting to be determined using 2 d forward and reverse structural and stratigraphic modelling the analysis shows that rifting was extremely rapid sequential decompaction and flattening of 2 d cross sections has been applied to six syn rift time horizons between top upper devonian 364 ma and top middle devonian 377 ma and used to quantify the syn rift development of basin cross sectional area in time the evolution of basin cross sectional area shows that some initial rifting had occurred prior to the middle frasnian 369 ma however most rifting occurred in the famennian 367 364 ma forward syn rift modelling using the flexural cantilever model of rift basin formation has also been applied to quantify the magnitude of extension within the pripyat trough in time forward syn rift models are constrained by the intra syn rift flattened and decompacted cross sections and the observed evolution of the cross sectional area most rapid rift basin formation is shown to have occurred in the famennian with over 66 of basin cross sectional area forming in less than 5 myr and with approximately 80 or more of total extension occurring in less than 3 myr this period of most rapid extension during the famennian coincides with the most active period of volcanicity total devonian extension across the pripyat trough is estimated to be of the order of 11 14 km with a maximum stretching factor of approximately 1 12 extensional strain rates are estimated to be of the order of 0 8 10 15 s 1

tectonic variation in the dniepr donets basin from automated modelling of backstripped subsidence curves abstract the multiphase rift evolution of the dniepr donets dd basin is analysed by 1d backstripping and tectonic modelling of 66 stratigraphic sections mostly from well data distributed throughout the basin the backstripping results illustrate strong temporal and lateral variations in tectonic subsidence it is minor during an inceptive pre rift phase givetian early frasnian 380 8 370 ma and does not show clear spatial correlations within the dd basin framework the main rift phase frasnian famennian 370 362 5 ma corresponds to an acceleration in subsidence rates with tectonic subsidence up to 1500 m along the basin axis displaying a slight increase from the northwest to the southeast strong lateral variations perpendicular to the basin axis reflect the effects of major basin border faults a rift phase in the visean 345 340 ma is characterised by relatively minor subsidence up to about 500 m except for some wells in the southeast following a stage of extremely low rates of deposition in the earliest carboniferous the end of this rift phase can be taken to mark the onset of convex subsidence patterns in the later carboniferous and permian typical in shape of post rift thermal subsidence but significantly increasing in magnitude from northwest to southeast in the basin this trend shows no one to one relationship with late devonian syn rift subsidence the tectonic subsidence curves have been modelled using lithospheric stretching assumptions allowing different stretching factors for the crustal and sub crustal lithosphere and the incorporation of finite and multiple stretching phases a numerical technique was developed that automatically finds best fit stretching parameters for part or all of the tectonic subsidence data given the specification of onset and duration of the various rifting events maps of the 1d modelling results display intrabasinal variations in terms of timing and magnitude of rifting the results indicate that the observed spatial and temporal variations of tectonic subsidence in the dd basin specifically the increasing ratio of carboniferous to late devonian subsidence from northwest to southeast cannot be explained by either a uniform or depth dependent stretching model adopting only a single frasnian famennian rift phase a two phase model in which a significant part of carboniferous tectonic subsidence is related to visean rift activity strongly dominated by sub crustal lithospheric attenuation provides a satisfactory fit to the data although the tectonic implications of such a model are not easily reconcilable by independent constraints a semi quantitative investigation of the possible role of withdrawal of underlying devonian salt during the carboniferous to produce additional post devonian rift phase sediment accommodation space suggests that the effects of such a mechanism could be significant but that they are unlikely to preclude the necessity of the visean rifting event to explain the carboniferous basin evolution

shale gas shale oil potential of upper visean black shales in the dniepr donets basin ukraine abstract upper visean rudov beds v 23 are considered as one of the main source rocks within the northwestern dniepr donets basin ddb average toc values within the srebnen bay northwestern ddb exceed 4 thickness up to 100 m average toc contents north and northwest of the srebnen bay up to 60 m are significantly lower 2 4 but still sufficient for unconventional hydrocarbon production whereas wells along the northeastern basin margin do not hold a shale oil gas potential 5 5 km although hydrogen index hi values of the most immature samples are 300 mghc gtoc basinal rudov beds host a potential to generate paraffinic naphthenic aromatic p n a low wax oil according to pyrolysis experiments a basinward maturity trend is visible but the maturity cut offs for shale oil gas production 0 8 rr 1 2 rr are reached at great depths 4 5 km 5 5 km only furthermore results of kinetic experiments do not argue for presence of type iis kerogen potentially triggering earlier hydrocarbon generation the mineralogy of rudov beds varies strongly in lateral and vertical directions limiting the predictability of mechanical behaviour samples from the siliceous basinal facies partly contain more than 60 of brittle minerals quartz feldspar carbonates etc suggesting a good fraccability this value is rarely reached by samples from the transitional and lagoonal calcareous and clayey facies the clay mineral fraction within many investigated rudov samples is dominated by kaolinite which is suggested to diminish the fraccability of shales apart from that expandable clay minerals ecm are present in samples from more than 5 km depth a result of low mesozoic heat flow

role of salt in restraining the maturation of subsalt source rocks abstract the presence of salt within a sedimentary basin can potentially modify its temperature distribution and history in particular the positive thermal anomaly associated with the top of salt domes has attracted considerable attention in the past the role of the lesser appreciated negative thermal anomaly associated with the base of salt domes in modifying the maturation history of subsalt source rocks is explored the finite element method was used to model the transient and steady state conductive temperature perturbations induced by salt layers domes and pillows the results indicate that the modification of the thermal regime due to evolving salt domes may significantly affect the maturation level of source rocks in the vicinity of the domes modelling the temperature structure of various salt structures has shown that in general the refraction of heat flow induces a dipole shaped temperature anomaly a positive anomaly located towards the top of the salt structure and a negative anomaly located towards its base these dipole anomalies can be strongly asymmetrical the degree of asymmetry depending on the shape of the salt structure and the proximity of the top of the salt structure to the surface of the basin however when the salt structure reaches the surface the dipole shaped temperature anomaly collapses to a monopole below the salt structure all sediments independent of their depth and lithology are colder relative to a section with no salt similarly salt domes that reach the surface very efficiently drain the heat from below and from the side of the dome these negative thermal anomalies may extend for a considerable depth beneath the base of the salt dome and may reach values of 85 c locally because of the large contrast in thermal conductivity between the highly porous sediments and salt at lower temperatures the efficiency of a salt dome to channel heat increases the closer the salt dome is to the surface these results indicate that deep sedimentary basins containing salt are more prospective than basins without salt and or salt diapirism in addition to the structural traps associated with salt tectonics salt domes and tongues connected to their source dissipate heat more efficiently and thus keep deeper regions of the basin relatively colder and potentially within the oil window for a longer time this cooling effect is maximized when the top of the salt dome remains close to the surface of the sedimentary basin for a significant period of time and may be especially important for continental margins such as brazil and offshore west africa where most of the source rocks lie beneath extensive evaporite deposits in contrast it was found that for the gulf of mexico basin pre and early tertiary salt diapirism and sheet emplacement may have caused significant delays in the maturation of subsalt source rocks in the deeper regions of the gulf basin but the maturation is likely to be relatively insensitive to the late miocene pliocene stage of salt mobilization because the time interval has been too short

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

the donbas foldbelt its relationships with the uninverted donets segment of the dniepr donets basin ukraine abstract the donbas foldbelt df is a thrust faulted and folded inverted segment of the dniepr donets basin ddb it lies between the scythian and east european platforms north of the black sea and is conventionally thought to have formed in the early permian as part of the late palaeozoic hercynian uralian orogenic frame of cratonic europe the ddb itself formed as a result of late devonian intracratonic rifting and contains a thick up to 22 km late palaeozoic and mesozoic sedimentary succession the deformed strata preserved at the erosional surface of the df are mainly carboniferous the donets segment of the ddb displays mild inversion structures that are transitional to those in the df recently acquired regional seismic reflection data in the donets part of the ddb allow these structures to be imaged in the subsurface for the first time a widespread early permian unconformity occurring throughout the ddb is much more pronounced on its southern margin than on its northern one and appears to be related to profound uplift of the southern flank of the basin and the neighbouring ukrainian shield rather than to crustal shortening faults associated with the early permian unconformity are extensional in style gentle folds and other local structures in the southern flank and axis of the donets segment are mainly located in areas associated with early permian salt movements no significant development of compressional structures of early permian age can be seen in the seismic data where it is available in contrast there is ample evidence of latest cretaceous earliest tertiary compressional deformation in the ddb including the subsurface expression of structures along strike of the main folds of the df a review of geological evidence in the df also indicates that the main period of shortening that can be definitely constrained in time is latest cretaceous earliest tertiary the eastern part of the df records intense late triassic aged cimmerian deformation but none of clearly permian age it is tentatively concluded that the main phases of trans compressional tectonics forming the df were cimmerian and especially alpine rather than hercynian uralian

style and timing of salt tectonics in the dniepr donets basin ukraine implications for triggering and driving mechanisms of salt movement in sedimentary basins abstract the ukrainian dniepr donets basin ddb is a late palaeozoic intracratonic rift basin with sedimentary thicknesses up to 19 km displaying the effects of salt tectonics during its entire history of formation from late devonian rifting to the tertiary hundreds of concordant and discordant salt structures formed during this time it is demonstrated in this paper that the variety of styles of salt structure formation in the ddb provide important constraints on understanding the triggering and driving mechanisms of salt kinematics in sedimentary basins in general salt movement in the ddb began during the devonian syn rift phase of basin development and exerted controls on the later distribution of salt structures though the geometry of basement faults is not directly responsible for the regular spacing of salt structures post rift salt movements in the ddb occurred episodically episodes of salt movement were triggered by tectonic events specifically two extensional events during the carboniferous an extensional reactivation at the end of carboniferous earliest permian and a compressional event at the end of the cretaceous extensional events that induced salt movement were thick skinned i e basement involved in deformation rather than thin skinned most overburden deformation related to salt movements is ductile regardless of sedimentary bulk lithology and degree of diagenesis while the deformation of sedimentary cover in areas where salt is absent is mainly brittle this implies that the presence of salt changes the predominant mode of deformation of overlying sedimentary rocks episodes of salt movement lasted longer than the periods of active tectonics that initiated them buoyancy erosion and differential loading all played a role in driving halokinesis once tectonic forces had pushed the salt overburden system into disequilibrium among these factors erosion of overburden above growing salt structures acted as a key self renewing force for development of salt diapirs very high sedimentation rates related to high post rift tectonic subsidence rates particularly during the carboniferous were able to bury diapirs and to load salt bodies such that buoyancy erosion and differential loading forces eventually became insufficient to continue driving diapirism until the system was perturbed by an ensuing tectonic event in contrast some salt anticlines and diapirs developed continuously during the entire mesozoic because of much reduced tectonic subsidence rates and sedimentation supply during this time however a lower permian salt series and overhangs of buried diapirs played an important role in preventing overburden piercing and fracturing during the mesozoic and specifically during the late cretaceous salt diapirism phase

soft sediment deformation structures induced by rapid sedimentation in early cretaceous turbidites lingshan island eastern china turbidites of the early cretaceous lingshandao formation on lingshan island eastern china show numerous soft sediment deformation structures the turbidites accumulated in a rift basin plain on the distal part of a low energy fan together with autochthonous fine grained sediments that settled from suspension occasionally sets of both types of sediments slumped down the basin slope the turbidites were studied in two sections paleocurrent directions measured from sole marks at the base of the sandy turbidites indicate a slope from se to nw this is consistent with the dip direction of the axial planes of the major slump folds among the numerous types of soft sediment deformation structures that are present two types are of special interest because of their specific genesis viz rip up clasts and dome structures it appears that rapid sedimentation must be considered as the main trigger behind these deformations the rapid accumulation of particularly the sandy turbidites resulted in overloading

guidelines for evaluating petroleum source rock using programmed pyrolysis rock eval pyrolysis is used to rapidly evaluate the petroleum generative potential and thermal maturity of rocks accurate conclusions require programs every 30 60 ft 9 18 m understanding of interpretive pitfalls and supporting data such as visual kerogen vitrinite reflectance and elemental analyses the generative potential of coals is commonly overestimated by pyrolysis and is best determined by elemental analysis and organic petrography most coals show high s2 s3 5 and low hi values 300 mg hc g toc migrated oil and mud additives which alter rock eval data can sometimes be removed by special processing for immature rocks bimodal s2 peaks and pi values over 0 2 indicate contamination pyrolysis downgrades organic poor clay rich rocks which show lower hi and higher tmax values than isolated kerogen because of adsorption of pyrolyzate on the clays tmax values for small s2 peaks 0 2 mg hc g toc are unreliable tmax is affected by maturation organic matter type contamination and the mineral matrix s3 is sensitive to inorganic and adsorbed carbon dioxide and to instrumentation problems acidification of carbonate rich samples and proper maintenance improves s3 measurement constant sample weights 100 mg are recommended below a threshold weight tmax increases by up to 10 c and other parameters decrease organic rich samples which overload the detector can be diluted with carbonate detector linearity is determined by pyrolyzing various weights of an organic rich rock

aulacogens and aulacogeosynclines regularities in setting and evolution abstract aulacogens and aulacogeosynclinal zones represent intra continental palaeorifts and inverted palaeorifts they were formed in the process of the break up of continents during the late proterozoic inversion of such basins occurred variably during the baikalian caledonian hercynian and alpine orogenic cycles in response to the build up of intraplate compressional stresses emanating from orogenic belts aulacogens were first recognized on the stable russian platform where they correspond to linear graben type depressions filled with proterozoic sediments often buried beneath a thick cover of palaeozoic and younger sediments some aulacogens have experienced a short period of reactivation during the palaeozoic aulacogeosynclines differ from the genetically related aulacogens by their greater dimensions and the amount of lithospheric extension that can go to the extent of opening of small ocean basins consequently they are characterized by a greater degree of destruction of the continental crust the depth of subsidence and the complexity of their post rift development which commonly terminates with their compressional deformation giving rise to the development of intracontinental linear folded and thrusted structures frequently associated with low grade metamorphism and small intrusions many ancient platforms are characterized by aulacogens metaplatforms are dissected by aulacogens and aulacogeosynclines whereas geosynclinal troughs are the precursors of geosynclinal mobil belts aulacogens aulacogeosynclines and geosynclinal troughs represent a group of negative linear structures which are characterized by an increasing degree of crustal destruction during rifting processes and increasing mobility during lithospheric contraction

structural features and evolution of the dniepr donets basin ukraine from regional seismic reflection profiles abstract a set of regional multichannel seismic reflection profiles crossing the dniepr donets dd basin in ukraine 100 200 km long and with a spacing of 10 15 km along strike illuminates the structure of the whole sedimentary cover the rift filled with pre and syn rift devonian sequences and overlain with post rift carboniferous permian mesozoic and palaeogene fill is clearly seen on all sections a basement layer previously identified as a riphean rift succession by refraction seismic studies constitutes in the main strata of the devonian and early carboniferous successions the structure of the rift is characterised by large scale rotational fault blocks and half grabens carried by basin parallel to normal marginal faults or by major horst blocks the total thickness of the devonian and younger succession is up to 19 km in the study area post rift carboniferous and mesozoic sediments cover the rift flanks and increase in thickness towards the rift axis and to the southeast the cumulative thickness of the carboniferous succession alone reaches 11 km with the maximum depth of their base at about 15 km major post rift tectonic events took place at the end of early visean in the middle of serpukhovian in permian times and between the mesozoic and cenozoic tectonic reactivations during carboniferous and early permian times were most pronounced in the southeastern part of the dd basin while they were least pronounced in the northwestern part of the basin merging with the pripyat trough where they are barely observed the most active development of salt structures and stocks corresponds with the periods of tectonic reactivation

two dimensional inverse modeling of sedimentary basin subsidence recently developed mathematical models of subsidence in extensional basins provide a good basis for forward modeling however the large number of parameters to be specified by the user makes it difficult not only to do the modeling itself but also to judge the meaning of the results we present a new method for automatic searching of the best fitting parameter set of a 2d basin formation model weighted goal functions are used in the minimization process by the inverse problem solver algorithm the nominal parameter set in the present case includes profiles of the crustal and subcrustal thinning factors and the level of lithosphere necking the method was tested on synthetic data with parameters that were perturbed beforehand with some restrictions the algorithms are capable of resolving such perturbations the inversion technique has been applied to two profiles crossing the dnieper donets basin ukraine the crustal thinning factors obtained argue for a scissors like style of basin opening high subcrustal thinning values are necessary in order to explain the abnormally thick carboniferous section in the basin these values should be treated as cumulative ones due to the currently unresolvable influence of other rifting related processes particularly phase transitions

magmatism and the geodynamics of rifting of the pripyat dnieper donets rift east european platform abstract the distribution of volcanism in the late devonian pripyat dnieper donets rift within the east european platform based upon the results of deep drilling indicates that pre existing basement structures and the major rift bounding faults played an important role in channelling the magmas towards the surface major and trace element and sr nd isotopic studies of the most primitive basic and ultrabasic magmas combined with estimates of the amount of extension 1 1 to 1 3 strongly suggest that magmatism was triggered by the upwelling of a thermally and geochemically anomalous mantle plume from the deep mantle during the late frasnian the peak of the magmatism occurred in the famennian coincident with the maximum amount of lithospheric extension magmatism rifting and domal basement uplife were contemporaneous at several localities within the eep suggesting that the thermal and geodynamic evolution of the platform could have been influenced by a cluster of mantle plumes during the late devonian

hydrocarbon habitat of the dniepr donets depression abstract basin inversion depending on its intensity can enhance the trapping potential of a basin or causes destruction of major hydrocarbon resources post inversion subsidence depending on its magnitude and the amount of syn inversion erosion can induce a second phase of hydrocarbon generation and the charging of inversion structures however this mechanism which contributed for instance to the hydrocarbon habitat of inverted basins in the southern north sea was not effective in the dniepr donets basin the dniepr donets depression forms part of the pripyat dniepr donets donbass karpinsky aulacogen that evolved as a devonian rift the post rift subsidence of this basin was interrupted during the late early permian when its southeastern parts were partly inverted further inversion pulses straddle the jurassic cretaceous and the cretaceous tertiary boundaries the dniepr donets depression hosts the most important hydrocarbon province of the ukraine at the beginning of 1994 ultimate recoverable reserves in established accumulations past production and remaining reserves amounted to about 170 10 6 t of oil and gas condensate and 980 10 9 m 3 gas the bulk of oil and gas accumulations is contained in carboniferous to early permian postrift series source rocks occur in devonian syn rift and carboniferous post rift series these attained maturity prior to basin inversion hydrocarbon accumulations are characterized by multiple reservoir seal pairs the mature syn rift devonian and the immature post inversion series contain only minor hydrocarbon accumulations oil and gas accumulations are mainly trapped in syn rift salt induced and inversion related structures the latter received their hydrocarbon charge mainly due to inversion induced destruction of pre existing accumulations and ensuing re migration of hydrocarbons

numerical modelling of the thermal evolution of the northwestern dniepr donets basin ukraine abstract the dniepr donets basin ddb is a late devonian rift structure located within the east european craton numerical heat flow models for 13 wells calibrated with new maturity data were used to evaluate temporal and lateral heat flow variations in the northwestern part of the basin the numerical models suggest that heat flow was relatively high during late carboniferous and or permian times the relatively high heat flow is probably related to an early permian re activation of tectonic activity reconstructed early permian heat flow values along the axial zone of the rift are about 60 mw m2 and increase to 90 mw m2 along the northern basin margin these values are higher than those expected from tectonic models considering a single late devonian rifting phase the calibration data are not sensitive to variations in the devonian carboniferous heat flow therefore the models do not allow deciding whether heat flows remained high after the devonian rifting or whether the reconstructed permian heat flows represent a separate heating event analysis of the vitrinite reflectance data suggest that the northeastern dniepr donets basin is characterised by a low mesozoic heat flow 30 35 mw m2 whereas the present day heat flow is about 45 mw m2

natural and artificial maturation of biological markers in a toarcian shale from northern germany steroid and terpenoid biological marker evolution was studied in a maturity sequence of lias toarcian shales and adjacent strata from three shallow boreholes in the hils syncline northern germany excellent facies control within the study area ensures the comparability of the organic matter type among the stratigraphically equivalent samples of the natural maturation series in the early hydrocarbon generation stage 0 68 r0 a strong facies dependence of some sterane and hopane isomerisation values was found within the same borehole at only a few metres depth difference the extent of sterane isomerisation at c 14 and c 17 was close to 80 in the toarcian shale and between about 55 and 65 in the adjacent dogger and lias sediments similar differences were observed for the 17 h hopane moretane and 22 29 30 trisnor 18 h neohopane 22 29 30 trisnor 17 h hopane ratios whereas the 20s 20s 20r sterane isomerisation ratio did not show this difference the observed differences mostly disappear by the end of the main oil generation phase 0 88 ro where several reactions appear to have reached completion hydrous pyrolysis experiments by variations of time and temperature were used to simulate the natural evolution of the biological markers results for sterane isomerisation in the high temperature range were compared to those published by mackenzie and mckenzie geol mag 120 417 470 1983 for natural sediments kinetic data derived for this reaction from the hydrous pyrolysis results alone or from the combination of hydrous pyrolysis and natural data sets differ markedly from those determined by mackenzie and mckenzie 1983 the hydrous pyrolysis data alone yield an activation energy for sterane isomerisation at c 20 of 131 kj mol the combined data of 170 kj mol the frequency factors are in the 105 108 s 1 range the significance of the data is discussed in detail

black shales in ukraine a review abstract as a result of a long lasting and complex geological history organic matter rich fine grained rocks black shales with widely varying ages can be found on ukrainian territory several of them are proven hydrocarbon source rocks and may hold a significant shale gas potential thick silurian black shales accumulated along the western margin of the east european craton in a foreland type basin by analogy with coeval organic matter rich rocks in poland high toc contents and gas window maturity can be expected however to date information on organic richness is largely missing and maturity patterns remain to be refined visean black shales with toc contents as high as 8 and a type iii ii kerogen accumulated along the axis of the dniepr donets rift basin ddb they are the likely source for conventional oil and gas oil prone serpukhovian black shales accumulated in the shallow northwestern part of the ddb similar black shales probably may be present in the lviv volyn basin western ukraine middle jurassic black shales up to 500 m thick occur beneath the carpathian foredeep they are the likely source for some heavy oil deposits toc contents up to 12 type ii have been recorded but additional investigations are needed to study the vertical and lateral variability of organic matter richness and maturity lower cretaceous black shales with a type iii ii kerogen toc 2 are widespread at the base of the carpathian flysch nappes but oligocene black shales menilite fm rich in organic matter 4 8 toc and containing a type ii kerogen are the main source rock for oil in the carpathians their thermal maturity increases from the external to the internal nappes oligocene black shales are also present in crimea maykop fm these rocks typically contain high toc contents but data from ukraine are missing