a reduced order successive linear estimator for geostatistical inversion and its application in hydraulic tomography national natural science foundation of china 51779179 51609173 51479144 51522904 crdf daa2 15 61224 1 tianjin normal university from the thousand talents plan of tianjin city special fund for public industry research from ministry of land and resources of china 201511047

diagenesis and reservoir quality of the aldebaran sandstone denison trough east central queensland australia the lower permian aldebaran sandstone is the principal hydrocarbon reservoir in the denison trough bowen basin east central queensland australia it accumulated in a wide range of fluvio deltaic and nearshore marine environments detailed petrological study of the unit by thin section x ray diffraction scanning electron microscopy electron microprobe and isotopic analysis reveals a complex diagenetic history which can be directly related to depositional environment initial composition and burial temperature history early diagenetic effects included the precipitation of pyrite siderite and illite smectite rims o smow 8 9 to 11 3 deep burial effects included physico chemical compaction and the formation of quartz overgrowths siderite c pdb 34 0 to 11 5 o 0 7 to 22 7 illite illite smectite and ankerite c 9 3 to 4 9 o 7 6 to 14 4 involved fluids were in part connate meteoric water derived from compaction of the underlying freshwater reids dome beds important post maximum burial effects controlled by deep meteoric influx from the surface were ankerite and labile grain dissolution and formation of kaolinite o 7 8 to 8 9 d 115 to 99 calcite c 9 5 to 0 9 o 9 0 to 20 0 and dawsonite c 4 0 to 2 3 o 9 8 to 19 8 the formation of dawsonite reflecting eventual stagnation of the aquifer entrapment of contained hydrocarbons was a relatively recent event which may be continuing today reservoir quality varies from marginal to good in the west to poor in the east with predictable trends being directly linked to depositional environment and diagenesis

a bayesian approach for inversion of hydraulic tomographic data 1 hydraulic tomography is a promising methodology that shows the potential to map subsurface hydraulic properties at an unprecedented level of detail by interpreting a suite of hydraulic tests in the present work we apply the hydraulic tomography concept to a multiple pulse multiple receiver mpmr cross well configuration which consists of two boreholes subdivided into intervals by packers a short pressure or flow pulse is applied sequentially to all the intervals and for each perturbation the transient heads are recorded at the remaining intervals the resulting tomograms are inverted within the bayesian framework by using the pilot point approach in addition to the values of the hydraulic conductivity at the pilot points we assume that the stochastic parameters of the spatial variability model the structural parameters are unknown using synthetic two dimensional and three dimensional examples we demonstrate the effectiveness of the mpmr configuration and the inversion procedure for characterizing the spatial variability of the hydraulic conductivity with limited or no prior information we observed that increasing the number of source points the locations at which the pulse is alternatively applied provides more details on the spatial variability and that the parameters of the hydrogeological model of spatial variability are inferred with an acceptable although variable level of accuracy in particular the theoretical variance of the log conductivity is estimated with large errors while the estimate of the anisotropic integral scales depends on the distance between the boreholes inversion preserves the overall spatial pattern of hydraulic conductivity although low conductivity values are less connected in the inferred than in the true conductivity fields

packing in a clastic sediment concept and measures abstract packing has been defined as the effective utilization of space by mutual arrangement of the constituent grains of an aggregate the effective utilization of space is governed both by the material aspect of the constituent grains size range size ratio shape etc of a clastic sediment and the mechanism aspect the manner of deposition of the agent three new measures of packing have been introduced 1 intrinsic packability factor pf denoting the maximum packing attainable with a particular set of grains 2 packing efficiency pc denoting how far the agent is capable of attaining the said maximum and 3 packing index pi denoting the resultant of the material aspect and the mechanism aspect for proper appreciation of the packing of a clastic sediment all the three packing parameters need to be determined

particle packing from an earth science viewpoint abstract particle packings are relevant to many aspects of the earth sciences and there is a long history of the study of packings from an earth science viewpoint packings have also been studied in connection with other subjects and disciplines allen 1982 produced a major review which provides a solid base for earth science related studies this review complements allen s work and in particular focuses on advances in the study of random packings over the last ten years transitions from packing to packing may be as important as the packings themselves and possibly easier to model this paper places emphasis on certain neglected works in particular morrow and graves 1969 and the packing transition envelope kahn 1956 and the measurement of packing parameters griffiths 1962 on packings in one dimension and getis and boots 1978 on packings in two dimensions certain packing problems are relevant to current areas of study including structure collapse in loess hydroconsolidation flowslides in very sensitive soils wind erosion jewel quality in opals and the structure and functions of sand dunes the region where interparticle forces become active particles

geochemistry and provenance of the carboniferous baixo alentejo flysch group south portuguese zone abstract this work is focused on the turbiditic sediments from the carboniferous baixo alentejo flysch group bafg in the south portuguese zone an external zone of the iberian variscides the aim of this work is to constrain the provenance and tectonic setting of these sediments in a context of a complex evolution of sw iberian variscides for this purpose we performed a systematic study of petrographical and geochemical signatures of greywackes and shales from the three bafg formations mertola mira and brejeira major and trace element composition and ratios suggest heterogeneous source area composition for bafg shales and greywackes for the oldest mertola formation greywackes source area is dominated by granitoid rocks with minor mafic input the latter becomes residual in the mira formation the youngest brejeira formation greywackes show clear felsic affiliation associated with an increase in recycled components the shales of all three bafg formations denote a granodioritic affiliation chemical index of alteration cia and plagioclase index of alteration pia values suggest moderate weathering in the source areas of mertola and mira formations these indices together with a cn k relations point out to steady state weathering conditions in the source areas of both formations in contrast both cia and pia values for the brejeira formation indicate variable conditions of palaeoweathering from moderate to intense as a consequence of non steady state conditions probably triggered by tectonic instability in the provenance area compared to the greywackes the shales of all three bafg formations exhibit higher cia and pia values as well as low k2o al2o3 0 2 and index of compositional variability

new evidence concerning the thermal history of devonian and carboniferous rocks in the south portuguese zone the late palaeozoic rocks of southern portugal have a complex thermal history vitrinite reflectance determinations from 90 samples confirm that the organic maturity of late palaeozoic rocks in sw portugal is very high mainly corresponding to meta anthracite coal rank the optic fabric of vitrinite in oriented coal samples from the brejeira formation suggests maturation under simple non tectonic burial conditions with peak temperatures being attained prior to variscan deformation the lack of any increase in vitrinite reflectance with depth through c 1 km of section in borehole ac 1 is not consistent with conductive heat transfer and is interpreted as the result of late synorogenic to post orogenic advective heating this heating episode generated temperatures sufficiently high to produce levels of maturity corresponding to meta anthracite coal rank through much of the terrane now exposed but not high enough to result in overprinting of the pre deformation optic fabric of vitrinite in the thin coals the slightly lower maturity of older platform facies rocks in the aljezur bordeira area may reflect either deposition on a basement high followed by less burial than adjacent parts of the basin or the area being the site of a sink for descending relatively cool fluids

the thermal history of the upper palaeozoic rocks of southern portugal abstract vitrinite reflectance vr evidence suggests that palaeozoic rocks in the south portuguese zone of southwest portugal are strongly post mature with mean vr r r of 4 28 results from a thin carboniferous coal are very similar to those from associated mudrocks suggesting that the results from mudrocks in the region are not significantly influenced by the presence of reworked vitrinite particles integration of stratigraphic evidence with vr results from a field oriented carboniferous coal sample indicate that peak temperatures were attained post hercynian deformation within the late carboniferous late triassic interval results from the aureole of a minor mesozoic igneous intrusion suggest that these intrusions did not significantly increase the already high maturation level of the palaeozoic country rocks vr r r values from triassic jurassic and cretaceous sections that unconformably overlie the palaeozoic rocks are much lower 0 87 1 14 than those from the palaeozoic and are fully consistent with recorded stratigraphic thicknesses and burial at geothermal gradients of 20 30 c km 1

superimposed thermal histories in the southern limit of the ossa morena zone portugal the mississippian volcano sedimentary complex in the toca da moura cabrela areas represents remnants of intra volcanic marine sedimentary basins formed during the collision between the ossa morena zone with the south portuguese zone these rock units are unconformably overlain by the pennsylvanian intramontane coal bearing santa susana basin vitrinite reflectance determinations from rocks of these two basins indicate two episodes of thermal maturation during the first episode the toca da moura cabrela volcano sedimentary complexes attained high maturation levels equivalent to anthracite coal rank 3 0 3 5 r oran which pre dates the middle moscovian santa susana basin the santa susana basin attained moderate maturation levels equivalent to bituminous coal rank 1 35 1 5 r oran recording a second episode of thermal maturation here peak thermal conditions did not overprint the first maturation episode the observed effects of magmatic intrusion on the thermal maturity and the lack of any increase in vitrinite reflectance with depth through c 400 m of section in borehole sdj 1 indicate high geothermal gradients during the first maturation episode a contemporaneous magmatic event associated with the c 335 320 ma cuba alvito gabbros diorites of the beja massif was the possible cause for the high geothermal gradients postulated for the first maturation episode burial under a post upper moscovian sedimentary cover was the most likely process to account for the maturation levels determined for the santa susana basin and for the second episode of thermal maturation

sedimentary facies analysis mineralogy and diagenesis of the mesozoic aquifers of the central perth basin western australia abstract assessment and successful exploration for and exploitation of aquifers in the perth basin require knowledge of their petrophysical and sedimentological characteristics and geometries this study provides a sedimentological and lithofacies analysis of core from the mesozoic yarragadee formation cadda formation cattamarra coal measures eneabba formation and lesueur sandstone of western australia recovered from pinjarra 1 cockburn 1 gingin 1 and gingin 2 wells provide insights into changes in depositional environment over time and space in the central perth basin in studied sections nine different fluvial dominated lithofacies have been identified in the yarragadee formation cadda formation and cattamarra coal measures that occur in similar proportions whereas the lesueur sandstone is dominated by coarse grained deposits of high energy fluvial systems vertical variation in lithofacies on the order of 10 cm to approximately 2 m vertical scale is observed in all formations and wells changes in the lithofacies linked to local depositional environments are probably associated with fluvial alluvial to fluvio deltaic systems that have complex 3d architecture including braided and to probably meandering systems and are affected by channel avulsion point counting and automated mineral analysis of thin sections of core showed detrital mineralogy dominated by monocrystalline quartz with rare polycrystalline quartz a moderate amount of alkali feldspar and very minor amounts of garnet organic fragments muscovite and biotite these data show a lithofacies dependence of the proportion of minerals with little variation between equivalent lithofacies from different depths formations or wells grain size and sorting that have a first order control on porosity are strongly lithofacies dependent individual lithofacies types show a trend of decreasing porosity with depth due to the increasing effects of compaction quartz overgrowth cementation and authigenic clay mineral development lithofacies and depth are the main controls on permeability and so lithofacies distribution exerts a key control on hydraulic behaviour

estimation of fracture zone geometry from steady state hydraulic head data using iterative sequential cokriging the hydrogeology of fractured crystalline rock is often controlled by a few highly conductive features such as faults and or fractures zones accurate modeling of fluid flow and transport in these systems requires that the geometry of these conductive features be characterized explicitly a new method for estimating the geometry of these features is presented the method is an extension of the recently developed geostatistical technique of sequential cokriging in this extension the geometry of the fracture zone is iteratively updated until an update increases the discrepancy between the estimated and observed hydraulic heads results from two hypothetical examples demonstrate that the method can accurately estimate the geometry of highly conductive fracture zones

3 d transient hydraulic tomography in unconfined aquifers with fast drainage response we investigate through numerical experiments the viability of three dimensional transient hydraulic tomography 3dtht for identifying the spatial distribution of groundwater flow parameters primarily hydraulic conductivity k in permeable unconfined aquifers to invert the large amount of transient data collected from 3dtht surveys we utilize an iterative geostatistical inversion strategy in which outer iterations progressively increase the number of data points fitted and inner iterations solve the quasilinear geostatistical formulas of kitanidis in order to base our numerical experiments around realistic scenarios we utilize pumping rates geometries and test lengths similar to those attainable during 3dtht field campaigns performed at the boise hydrogeophysical research site bhrs we also utilize hydrologic parameters that are similar to those observed at the bhrs and in other unconsolidated unconfined fluvial aquifers in addition to estimating k we test the ability of 3dtht to estimate both average storage values specific storage ss and specific yield sy as well as spatial variability in storage coefficients the effects of model conceptualization errors during unconfined 3dtht are investigated including 1 assuming constant storage coefficients during inversion and 2 assuming stationary geostatistical parameter variability overall our findings indicate that estimation of k is slightly degraded if storage parameters must bemore jointly estimated but that this effect is quite small compared with the degradation of estimates due to violation of structural geostatistical assumptions practically we find for our scenarios that assuming constant storage values during inversion does not appear to have a significant effect on k estimates or uncertainty bounds less

porosity reduction in sandstone by quartz overgrowth a mathematical model for predicting porosity histories due to quartz overgrowth in quartz rich sandstone reservoirs has been developed the model neglects secondary dissolution porosity and other diagenetic processes such as compaction and precipitation of carbonate and clay minerals nevertheless the model is straightforward and easy to use to calculate porosity the calculated porosity corresponds to measured porosity of simple quartz cemented sandstones in 27 wells in north and south america the model is based on fluid flow through initially porous unlithified sands in which the fluid phase is saturated with si oh 4 and is always in equilibrium with quartz as the continuously circulating fluid migrates updip toward the basin edge it cools and quartz precipitates into the pore spaces causing a loss of porosity basinal fluid velocities may be calculated assuming 1 thermal convection and 2 hydrostatic pressure due to recharge at the edge of the basin porosity diagrams relating porosity to geothermal gradient burial rate and depth of burial are compared to thermal maturation models of source rocks fluid flow history and grain size distribution the rate of porosity reduction depends on the following variables in decreasing order of significance buria rate age initial porosity basin size dip angle fluid dynamics initial permeability and geothermal gradient

the ca 350 ma beja igneous complex a record of transcurrent slab break off in the southern iberia variscan belt abstract we report the results of an isotopic study of the large gabbro dioritic beja igneous complex bic in the boundary between the highly contrasting ossa morena om and south portuguese sp zones of the southern iberian variscan orogen this boundary is interpreted as a major suture zone materialized by discontinuous scattered strips of mafic ultramafic rocks the so called beja acebuches ophiolite complex baoc and by melange deposits of middle to late devonian age in the pulo do lobo accretionary prism plap the beja gabbro was interpreted either as part of the ophiolite like units or as a broadly arc related massif reflecting the northward subduction of oceanic lithosphere u pb zircon id tims dating of two diorites and a granodiorite points to igneous emplacement ages of 350 2 ma serpa 352 2 ma torrao and 353 4 ma sao pedro respectively whereas a felsic dyke yields a slightly younger age of 345 2 ma these results show that published ar ar dates do not represent igneous crystallization ages but merely reflect regional cooling below ca 500 c at least 10 ma after the major intrusive event probably as a result of uplift of the omz side of the suture zone relative to the subsiding spz 87sr 86sr350 and end350 display a large range of values from 0 7041 to 0 7093 and from 4 0 to 6 1 respectively which documents a rather complex petrogenetic history with an important role played by crustal contamination processes the more primitive sr and nd isotope signatures are measured in the mafic cumulates while radiogenic sr and unradiogenic nd isotope compositions occur in the more evolved rock types the broad trend of decreasing end350 with decreasing sm nd and increasing sio2 concentration is reminiscent of crustal assimilation combined with fractional assimilation afc end values of flasergabbros and associated cumulates ascribed to the ophiolite like unit in the guadiana valley are close to zero or even slightly negative irrespective of the age chosen for the correction for in situ radioactive decay of 147sm in the range 350 500 ma assumed to encompass the true geological age this observation conflicts with a truly oceanic derivation of these rocks which could rather represent early stage deformed and metamorphosed equivalents of the beja gabbro most metabasalts of the same area have positive albeit variable end consistent with mildly depleted mantle sources and or significant crustal assimilation only a few samples reach highly positive values end350 500 ca 8 similar to those typical for n morbs as do the acebuches amphibolites near aracena end350 500 ca 9 these data suggest that the baoc is not only disrupted but also composite since the gabbroic rocks are not cogenetic with the basalts based on the late devonian age of the collision between the omz and spz the emplacement of the beja gabbro cannot be related to an active subduction of oceanic lithosphere instead the generation in the mantle and emplacement in the overlying continental crust of copious volumes of mafic magmas with concomitant lp ht metamorphism is tentatively ascribed to a process of transcurrent slab break off that followed oblique subduction and collision

microfacies depositional environment and diagenetic evolution controls on the reservoir quality of the permian upper dalan formation kish gas field zagros basin abstract the upper permian upper dalan formation contains one of the largest gas reservoirs in the world the formation consists of carbonates with some evaporite intercalations that developed on a gently sloping homoclinal carbonate ramp facing the late permian paleo tethys ocean this study focuses on the kish gas field zagros offshore basin situated between iran and qatar and is based on a 222 m thick continuous core based on the integration of core and wireline log data coupled with petrographic analyses of 580 thin sections three major depositional environments facies belts with 11 carbonate microfacies are identified these include 1 sabkha to tidal flat laminated to massive anhydrite dolomudstone with anhydrite nodules dolomudstone and intraclastic dolowackestone 2 lagoon and leeward shoals bioclastic wackestone dolowackestone to packstone and peloid dolopackstone and peloid bioclastic dolopackstone and 3 mobile windward sand shoal ooid peloid dolograinstone ooid dolograinstone ooid intraclast dolograinstone ooid bioclast dolograinstone packstone and coarse bioclast intraclast dolograinstone diagenetic evolution of the upper dalan formation is associated with evaporative marine shallow water normal marine meteoric and burial diagenetic environments common diagenetic effects include dolomite and calcite cementation mechanical and chemical compaction dissolution dolomitization and evaporative anhydrite mineralization reservoir quality is strongly affected by variations in the original rock fabrics and subsequent diagenetic alterations the most common pore types include interparticle moldic and connected vug fracture and cavernous the interparticle porosity permeability relationship for the studied facies suggests that the reservoir quality is not affected by different crystal sizes and most samples plot in the low porosity and low to high permeability field or display lucia class 1 or 2 petrophysical relationships the study shows that the pervasive pore filling anhydrite mineralization lead to a significant decrease in porosity and permeability poikilotopic anhydrite cement reduced matrix porosity but the pore size was less affected

sulige field in the ordos basin geological setting field discovery and tight gas reservoirs abstract the sulige gas field in central ordos basin is one of the largest gas fields in china with about 860 7 billion cubic meters bcm of proven gas reserve this field covers an area of about 500 km 2 with largely tight clastic reservoirs the upper carboniferous lower permian deltaic sandstones and upper permian lacustrine mudstones deposited in a stable cratonic tectonic setting form an effective petroleum system that is favorable for gas accumulation in large scale stratigraphic lithologic traps based on wire line log response drilling stem test and core data a generalized classification system was developed for the gas reservoirs of the sulige field thus type i and ii rocks are capable of gas production without natural and or artificial fracturing type iii rocks are capable of gas production after artificial fracturing and type iv rocks are too tight to produce at commercial rates even with artificial fracturing the discovery of the sulige field not only adds large gas reserve in the ordos basin but strongly indicates the overlook potential of both tight sandstone reservoir rock and relatively porous and permeable sweet spots in it

characterization of aquifer heterogeneity using transient hydraulic tomography 1 hydraulic tomography is a cost effective technique for characterizing the heterogeneity of hydraulic parameters in the subsurface during hydraulic tomography surveys a large number of hydraulic heads i e aquifer responses are collected from a series of pumping or injection tests in an aquifer these responses are then used to interpret the spatial distribution of hydraulic parameters of the aquifer using inverse modeling in this study we developed an efficient sequential successive linear estimator ssle for interpreting data from transient hydraulic tomography to estimate three dimensional hydraulic conductivity and specific storage fields of aquifers we first explored this estimator for transient hydraulic tomography in a hypothetical one dimensional aquifer results show that during a pumping test transient heads are highly correlated with specific storage at early time but with hydraulic conductivity at late time therefore reliable estimates of both hydraulic conductivity and specific storage must exploit the head data at both early and late times our study also shows that the transient heads are highly correlated over time implying only infrequent head measurements are needed during the estimation applying this sampling strategy to a well posed problem we show that our ssle can produce accurate estimates of both hydraulic conductivity and specific storage fields the benefit of hydraulic tomography for ill posed problems is then demonstrated finally to affirm the robustness of our ssle approach we apply the ssle approach to a hypothetical three dimensional heterogeneous aquifer

burial diagenesis of illite smectite in shales and the origins of authigenic quartz and secondary porosity in sandstones several gram size samples of 0 1 mu m nearly monomineralic mixed layer illite smectite i s were isolated from nineteen whole cores of shale of the frio formation from the texas gulf coast between approximately 7 000 ft 2133 m and approximately 15 000 ft 4572 m burial depth i s changes from random interstratification r 0 with low 1 to ordered interstratification r 3 with high i the accompanying chemical changes are loss of si mg and fe sup 3 gain of k al and fe sup 2 and a shift in the ree content of the mineral there is no chemical or mineralogical evidence for a cessation of i s reaction at approximately 80 i as is commonly accepted both chemical and mineralogical changes occur throughout burial continuous change in the oxygen isotopic composition of i s implies that the conversion of smectite layers to illite layers is a dissolution and reprecipitation process mass balance calculations indicate that burial diagenesis of frio formation shales is an open system process that requires addition of k sub 2 o and al sub 2 o sub 3 and results in loss of sio sub 2 the amount of sio sub 2 made available by shale diagenesis is sufficient to be the source of the quartz overgrowth cements in the associated frio sandstones iron reduction in i s is amore significant source of the acid required for the diagenesis of both frio shales and sandstones 68 refs 12 figs 4 tabs less

comparison of aquifer characterization approaches through steady state groundwater model validation a controlled laboratory sandbox study 1 groundwater modeling has become a vital component to water supply and contaminant transport investigations an important component of groundwater modeling under steady state conditions is selecting a representative hydraulic conductivity k estimate or set of estimates which defines the k field of the studied region currently there are a number of characterization approaches to obtain k at various scales and in varying degrees of detail but there is a paucity of information in terms of which characterization approach best predicts flow through aquifers or drawdowns caused by some drawdown inducing events the main objective of this paper is to assess k estimates obtained by various approaches by predicting drawdowns from independent cross hole pumping tests and total flow rates through a synthetic heterogeneous aquifer from flow through tests specifically we 1 characterize a synthetic heterogeneous aquifer built in the sandbox through various techniques permeameter analyses of core samples single hole cross hole and flow through testing 2 obtain mean k fields through traditional analysis of test data by treating the medium to be homogeneous 3 obtain heterogeneous k fields through kriging and steady state hydraulic tomography and 4 conduct forward simulations of 16 independent pumping tests and six flow through tests using these homogeneous and heterogeneous k fields and comparing them to actual data results show that the mean k and heterogeneous k fields estimated through kriging of small scale k data core and single hole tests yield biased predictions of drawdowns and flow rates in this synthetic heterogeneous aquifer in contrast the heterogeneous k distribution or k tomogram estimated via steady state hydraulic tomography yields excellent predictions of drawdowns of pumping tests not used in the construction of the tomogram and very good estimates of total flow rates from the flow through tests these results suggest that steady state groundwater model validation is possible in this laboratory sandbox aquifer if the heterogeneous k distribution and forcing functions boundary conditions and source sink terms are characterized sufficiently

gondwana derived microcontinents the constituents of the variscan and alpine collisional orogens abstract the european variscan and alpine mountain chains are collisional orogens and are built up of pre variscan building blocks which in most cases originated at the gondwana margin such pre variscan elements were part of a pre ordovician archipelago like continental ribbon in the former eastern prolongation of avalonia and their present day distribution resulted from juxtaposition through variscan and or alpine tectonic evolution the well known nomenclatures applied to these mountain chains are the mirror of variscan resp alpine organization it is the aim of this paper to present a terminology taking into account their pre variscan evolution at the gondwana margin they may contain relics of volcanic islands with pieces of cadomian crust relics of volcanic arc settings and accretionary wedges which were separated from gondwana by initial stages of rheic ocean opening after a short lived ordovician orogenic event and amalgamation of these elements at the gondwanan margin the still continuing gondwana directed subduction triggered the formation of ordovician al rich granitoids and the latest ordovician opening of palaeo tethys an example from the alps external massifs illustrates the gradual reworking of gondwana derived pre variscan elements during the variscan and alpine tertiary orogenic cycles

pore characteristic responses to categories of depositional microfacies of delta lacustrine tight reservoirs in the upper triassic yanchang formation ordos basin nw china abstract primary depositional variations interact with diagenetic modifications to exert strong control on pore networks in tight hydrocarbon reservoirs however the linkage between pore characteristics and depositional microfacies remains enigmatic which restricts the prediction of high quality reservoir distributions the continental tight reservoirs of the yanchang formation in the ordos basin are targeted to clarify and estimate the sensitivity of pore characteristics to depositional microfacies a multi methodical approach utilizing petrographic assessments logging evaluations digital imaging analyses and high pressure mercury intrusion experiments enables us to reveal the high microheterogeneity of pore types pore size distribution and pore fractal features the results identified the microfacies including distributary channels dcs mouth bars mbs interdistributary bays ibs sheet sands sss turbidite fans tfs shallow lacustrine mudstones slms and semi deep lacustrine mudstones sdlms from the chang 8 to chang 6 members dominated by residual intergranular pores and microfractures the main storage spaces of the dc and mb microfacies are within mesopores which provide 62 92 and 81 of the total pore volume respectively however the micropores that are mainly composed of clay intercrystalline pores and feldspar dissolved pores provide 55 70 52 62 and 53 80 of the total pore volume for the ib slm and sdlm microfacies respectively in addition the pore fractal dimension results indicate that the mesoporous structure of the argillaceous microfacies ib slm and sdlm is more heterogeneous than that of the arenaceous microfacies dc mb and tf therefore the dominant reservoir spaces of the different depositional microfacies are distributed over diverse pore radius ranges and the varying degrees of mesoporous development are a crucial factor affecting the reservoir capacity moreover the fractal dimensions have a significant negative correlation with pore volume in the meso micropore range characterized by lower pore sorting coefficients broader skewness and more abundant rigid siliceous grains the arenaceous microfacies with lower fractal dimensions and higher pore volume have better reservoir capacity than argillaceous microfacies that are rich in ductile minerals microscopic observations show that the muddier reservoirs of interdistributary bays and lacustrine mudstones are more susceptible to pore filling chlorite and illite which can deteriorate the reservoir quality these results indicate that the controlling effect of depositional microfacies on pore characteristics is fundamentally caused by differences in mineralogical composition and depositional texture and these results could provide new insights into the mechanisms of microfacies controls on reservoir quality

the nature of porosity in organic rich mudstones of the upper jurassic kimmeridge clay formation north sea offshore united kingdom abstract analyses of organic rich mudstones from wells that penetrated the upper jurassic kimmeridge clay formation offshore united kingdom were performed to evaluate the nature of both organic and inorganic rock constituents and their relation to porosity in this world class source rock the formation is at varying levels of thermal maturity ranging from immature in the shallowest core samples to mature in the deepest core samples the intent of this study was to evaluate porosity as a function of both organic macerals and thermal maturity at least four distinct types of organic macerals were observed in petrographic and sem analyses and they all were present across the study area the macerals include in decreasing abundance 1 bituminite admixed with clays 2 elongate lamellar masses alginite or bituminite with small quartz feldspar and clay entrained within it 3 terrestrial vitrinite fusinite semifusinite grains and 4 tasmanites microfossils although pores in all maceral types were observed on ion milled surfaces of all samples the pores largely nanopores with some micropores vary as a function of maceral type importantly pores in the macerals do not vary systematically as a function of thermal maturity insofar as organic pores are of similar size and shape in both the immature and mature kimmeridge rocks if any organic pores developed during the generation of hydrocarbons they were apparently not preserved possibly because of the highly ductile nature of much of the rock constituents of kimmeridge mudstones clays and organic material inorganic pores largely micropores with some nanopores have been observed in all kimmeridge mudstones these pores particularly interparticle i e between clay platelets and intraparticle i e in framboidal pyrite in partially dissolved detrital k feldspar and in both detrital and authigenic dolomite are noteworthy because they compose much of the observable porosity in the shales in both immature and mature samples the absence of a systematic increase in organic porosity as a function of either maceral type or thermal maturity indicates that such porosity was probably unrelated to hydrocarbon generation instead much of the porosity within mudstones of the kimmeridge appears to be largely intraparticle and interparticle adjacent to inorganic constituents so the petroleum storage potential in these organic rich mudstones largely resides in inorganic pores

on the importance of geological data for three dimensional steady state hydraulic tomography analysis at a highly heterogeneous aquifer aquitard system abstract hydraulic tomography ht has been shown to map subsurface heterogeneity accurately through the joint interpretation of multiple pumping tests previous research has shown that smooth hydraulic conductivity k estimates are obtained beyond where pumping observation data are available using the geostatistical inversion approach when the inversion begins with a homogeneous k and when data densities are not high however geological data are typically available through outcrops and borehole logs to provide geological variability therefore we investigate the usefulness of geological data for ht analysis at a highly heterogeneous field site by 1 comparing calibrated geological models of two different resolutions to two homogeneous and four highly parameterized geostatistical inverse models in terms of both model calibration and validation performances as well as correspondence of estimated k values with permeameter estimated k profiles along boreholes and 2 using geological models as prior information for the geostatistical inversion approach results reveal that the simultaneous calibration of geological models to seven pumping test data yields k values that correctly reflect the general patterns of vertical distributions of permeameter estimated k we also find that the geostatistical inversion approach using a geological model as prior information performs better for both model calibration and validation than using a homogenous k as a prior and more importantly improves the correspondence of k estimates to permeameter test results along wells as well as in preserving geological features where drawdown measurements are lacking overall our results suggest the joint use of both geological and pumping test data for ht analysis when accurate geological data are available

three dimensional imaging of aquifer and aquitard heterogeneity via transient hydraulic tomography at a highly heterogeneous field site abstract previous studies have shown that geostatistics based transient hydraulic tomography tht is robust for subsurface heterogeneity characterization through the joint inverse modeling of multiple pumping tests however the hydraulic conductivity k and specific storage ss estimates can be smooth or even erroneous for areas where pumping observation densities are low this renders the imaging of interlayer and intralayer heterogeneity of highly contrasting materials including their unit boundaries difficult in this study we further test the performance of tht by utilizing existing and newly collected pumping test data of longer durations that showed drawdown responses in both aquifer and aquitard units at a field site underlain by a highly heterogeneous glaciofluvial deposit the robust performance of the tht is highlighted through the comparison of different degrees of model parameterization including 1 the effective parameter approach 2 the geological zonation approach relying on borehole logs and 3 the geostatistical inversion approach considering different prior information with without geological data results reveal that the simultaneous analysis of eight pumping tests with the geostatistical inverse model yields the best results in terms of model calibration and validation we also find that the joint interpretation of long term drawdown data from aquifer and aquitard units is necessary in mapping their full heterogeneous patterns including intralayer variabilities moreover as geological data are included as prior information in the geostatistics based tht analysis the estimated k values increasingly reflect the vertical distribution patterns of permeameter estimated k in both aquifer and aquitard units finally the comparison of various tht approaches reveals that differences in the estimated k and ss tomograms result in significantly different transient drawdown predictions at observation ports

sequential aquifer tests at a well field montalto uffugo scalo italy 1 this paper investigates our ability to characterize an aquifer using a sequential aquifer test in a well field that consists of six wells during the test we pumped water out from the aquifer at one well and monitored the water level changes at the rest of the wells to obtain a set of five well hydrographs by pumping at another of the six wells we obtained another set of five hydrographs this procedure was repeated until each of the six wells was pumped we then analyzed the six sets of hydrographs using the classical drawdown time the drawdown distance and the drawdown distance time methods results of the analysis confirm recent findings that the transmissivity estimates vary significantly at early time and stabilize at late time at late time the estimated values from all hydrographs are similar overall but vary slightly according to the locations of the pumping and observation wells in contrast storage coefficient estimates stabilized rapidly to distinct values associated with the well locations we subsequently used a hydraulic tomography approach to include all hydrographs from the sequential aquifer test to estimate the spatially varying transmissivity and storage coefficient fields the estimated fields appear to be realistic they reflect the geologic setting and the behaviors of the well hydrographs although more definitive confirmation is needed

organic maturation of the algarve basin southern portugal and its bearing on thermal history and hydrocarbon exploration abstract the algarve basin southern portugal is under explored in terms of petroleum geology organic maturation levels and the thermal history of this basin have been ascertained together with their implications for future exploration maturity was determined using vitrinite reflectance and spore fluorescence colour the succession was extensively sampled 158 onshore samples and 20 samples from two offshore wells thermal history was modelled using 1d petromod a palynostratigraphic study of two offshore wells was also completed showing thick marl limestone sequences of middle and upper jurassic age hiatuses were identified in the offshore wells within the jurassic section and between the jurassic and the miocene sections the mesozoic rocks of the algarve basin lie within the oil window vitrinite reflectance ranges from 0 52 0 7 r r in the lower cretaceous to 1 1 1 r r in the upper triassic hettangian miocene rocks that unconformably overlie the mesozoic strata are immature 0 42 0 47 r r maturation levels increase with increasing age of the strata indicating that burial was the main process controlling maturation thick marl limestone sequences of the middle jurassic callovian and the upper jurassic oxfordian are the main source rock intervals the miocene successions of both offshore wells contains reworked vitrinite and palynomorphs with maturation levels similar to the mesozoic rocks of the basin suggesting exposure and erosion of these rocks during miocene times palaeogeothermal gradients in the onshore algarve basin range from 52 c km to 24 7 c km with pre miocene exhumation estimated at 2000 2500 m the probable age for the removed cover is upper cretaceous to lower palaeocene and peak temperatures in the mesozoic rocks were attained during latest cretaceous early palaeocene times modelled palaeotemperatures suggest that the jurassic entered the oil window at the beginning of the cretaceous with peak oil generation in late cretaceous time

a travel time based hydraulic tomographic approach 1 hydraulic tomography is a method to identify the three dimensional spatial distribution of hydraulic properties in the subsurface we propose a tomographic approach providing the inversion of travel times of hydraulic or pneumatic tests conducted in a tomographic array the inversion is based on the relation between the peak time of a recorded transient pressure curve and the diffusivity of the investigated system the development of a transformation factor enables the inversion of further travel times besides the peak time of a transient curve as the early travel times of the curve are mainly related to preferential flow features while the inversion based on late travel times are reflecting an integral behavior it can be assumed that the different inversion results reflect the properties of the overall system by comparing the different reconstructions the system interpretation therefore becomes more comprehensive and reliable furthermore the similarity of the proposed hydraulic tomographic approach to seismic travel time tomography allows us to apply the inversion algorithms which are used for seismic tomography we therefore apply the method of staggered grids which enables to refine the grid resulting in a higher nominal resolution to data from a set of interference tests arranged in a tomographic array the tests were conducted in an unsaturated fractured sandstone cylinder in the laboratory the three dimensional reconstructions of the diffusivity distribution are found to be highly reliable and robust in particular the mapped fracture of the sandstone cylinder coincides with our reconstructed diffusivity distribution

steady state hydraulic tomography in a laboratory aquifer with deterministic heterogeneity multi method and multiscale validation of hydraulic conductivity tomograms summary hydraulic tomography potentially is a viable technology that facilitates subsurface imaging of hydraulic heterogeneity to date a comprehensive validation of hydraulic tomography has not been done either at the laboratory or field scales the main objective of this paper is to examine the accuracy of hydraulic conductivity k tomograms obtained from the steady state hydraulic tomography algorithm of yeh t c j liu s 2000 hydraulic tomography development of a new aquifer test method water resources research 36 2095 2105 we first obtain a reference k tomogram through the inversion of synthetic cross hole test data generated through numerical simulations the purpose of reference k tomogram generation is to examine the ability of the algorithm to image the heterogeneity pattern under optimal conditions without experimental errors and with full control of forcing functions initial and boundary conditions as well as source sink terms parallel to the generation of synthetic data we conduct hydraulic tests at multiple scales in a laboratory aquifer with deterministic heterogeneity to generate data that are used to validate k tomograms from hydraulic tomography measurements include multiple k estimates from core slug single hole and cross hole tests as well as several unidirectional flow through experiments conducted on the sandbox under steady state conditions validation of k tomograms involved a multi method and multiscale approach proposed herein which include 1 visual comparisons of k tomograms to the true sand distributions and the reference k tomogram 2 testing the ability of the k tomogram to predict the hydraulic head distribution of an independent cross hole test not used in the computation of the k tomogram 3 comparison of the conditional mean and variance of local k from the k tomograms to the sample mean and variance of results from other measurements 4 comparison of local k values from k tomograms to those from the reference k tomogram and 5 comparison of local k values from k tomograms to those obtained from cores and single hole tests the multi method and multiscale validation approach proposed herein further illustrates the robustness of steady state hydraulic tomography in subsurface heterogeneity delineation

on the importance of geological data for hydraulic tomography analysis laboratory sandbox study abstract this paper investigates the importance of geological data in hydraulic tomography ht through sandbox experiments in particular four groundwater models with homogeneous geological units constructed with borehole data of varying accuracy are jointly calibrated with multiple pumping test data of two different pumping and observation densities the results are compared to those from a geostatistical inverse model model calibration and validation performances are quantitatively assessed using drawdown scatterplots we find that accurate and inaccurate geological models can be well calibrated despite the estimated k values for the poor geological models being quite different from the actual values model validation results reveal that inaccurate geological models yield poor drawdown predictions but using more calibration data improves its predictive capability moreover model comparisons among a highly parameterized geostatistical and layer based geological models show that 1 as the number of pumping tests and monitoring locations are reduced the performance gap between the approaches decreases and 2 a simplified geological model with a fewer number of layers is more reliable than the one based on the wrong description of stratigraphy finally using a geological model as prior information in geostatistical inverse models results in the preservation of geological features especially in areas where drawdown data are not available overall our sandbox results emphasize the importance of incorporating geological data in ht surveys when data from pumping tests is sparse these findings have important implications for field applications of ht where well distances are large

the bucaco basin portugal organic petrology and geochemistry study abstract the bucaco basin includes a carboniferous permian sequence that comprises from bottom to top the following stratigraphic sequence algeriz formation vale da mo formation and monsarros formation algeriz formation is constituted by deposits of basal breccia with variable thickness and alternating layers of siltstone mudstone and conglomerate vale da mo formation corresponds to lacustrine deposits comprising massive red beds in the base that pass alternatively to silty mudstones shales and grey mudstones with organic matter this formation also includes a thin coal seam monsarros formation includes fluvial conglomeratic deposits prevalent in the base and top separated by layers of siltstone and mudstone redder to the top the bucaco basin opens as a pull apart basin into the porto coimbra tomar shear zone and later is affected by the clockwise dextral movement of this n10 w shear zone the petrographic study of samples from vale da mo formation showed that the organic matter corresponds to a type iii kerogen derived from higher land plants gas prone the thermal maturation level of the strata was determined using random vitrinite reflectance with values ranging from 0 72 to 0 80 rr rock eval pyrolysis showed that vale da mo formation is the only one with potential to generate hydrocarbons an observation consistent with the petrographic characteristics toc ranges from 0 08 to 1 52 monsarros formation reported the highest values for s1 toc index

a study of inherited zircons in granitoid rocks from the south portuguese and ossa morena zones iberian massif support for the exotic origin of the south portuguese zone abstract trace element and u pb isotopic analyses of inherited zircon cores from a sample of gil marquez granodiorite south portuguese zone spz and almonaster nebulite ossa morena zone omz in the aracena metamorphic belt have been obtained using laser ablation inductively coupled plasma mass spectrometry these data reveal differences in the age of deep continental crust in these two zones inherited zircon cores from the ossa morena zone range at 600 100 ma 1 7 2 ga and 2 65 2 95 ga while those from the south portuguese zone range at 400 500 and 700 800 ma these data support the exotic origin of the south portuguese zone basement relative to the rest of iberian massif the young ages of inherited zircon cores and nd model ages of magmatic rocks of the south portuguese zone are comparable to results from granulite facies xenoliths and granitic rocks from the meguma terrane and avalonia and support a correlation between the basement of the southernmost part of the iberian massif and the northern appalachians

experimental nucleation and growth of smectite and chlorite coatings on clean feldspar and quartz grain surfaces abstract laboratory experiments were performed to investigate high temperature 100 150 c authigenic formation of clay coatings smectites chlorites on clean feldspar and quartz surfaces artificial formation waters were used with mg concentrations in the range of north sea brines experiments were run for 21 50 days in brines composed of magnesium chloride and sodium carbonate adjusted to circum neutral ph the experiments suggest that the silica activity is the main factor determining if grain coating smectites or chlorite form the clay minerals form easily on both clean quartz and feldspar surfaces but chlorite coatings were formed only on feldspar surfaces while smectite coatings were formed on both feldspar and quartz the chlorite morphology varies between honeycomb edge to face and rosette patterns while all smectite formed with honeycomb like textures the clay coatings produced in this study are morphologically similar to naturally occurring diagenetic clay minerals in natural sediments and sedimentary rocks the formation of clay coatings is promoted by pre existing clay drapings on mineral grains the growth substrates used in this study were not coated with such a natural precursor materials this suggests that the nucleation of clay coatings in nature may be possible on clean quartz and feldspar surfaces but pre existing clay minerals may impact the allowed levels of supersaturations and thereby the formation of the grain coating phases

capturing aquifer heterogeneity comparison of approaches through controlled sandbox experiments 1 groundwater modeling has become a vital component to water supply and contaminant transport investigations these models require representative hydraulic conductivity k and specific storage ss estimates or a set of estimates representing subsurface heterogeneity currently there are a number of approaches for characterizing and modeling k and ss heterogeneity in varying degrees of detail but there is a lack of consensus for an approach that results in the most robust groundwater models with the best predictive ability the main goal of this study is to compare different heterogeneity modeling approaches e g effective parameters geostatistics geological models and hydraulic tomography when input into a forward groundwater model and used to predict 16 independent cross hole pumping tests we first characterize a sandbox aquifer through single and cross hole pumping tests and then use these data to construct forward groundwater models of various complexities both homogeneous and heterogeneous distributions two effective parameter models are constructed 1 by taking the geometric mean of single hole test k and ss estimates and 2 calibrating effective k and ss estimates by simultaneously matching the response at all ports during a cross hole test heterogeneous models consist of spatially variable k and ss fields obtained via 1 kriging single hole data 2 calibrating a geological model and 3 conducting transient hydraulic tomography zhu and yeh 2005 the performance of these parameter fields are then tested through the simulation of 16 independent cross hole pumping tests our results convincingly show that transient hydraulic tomography produces the smallest discrepancy between observed and simulated drawdowns

geodynamic settings and tectonic model of skarn gold deposits in china an overview seventy skarn type gold deposits including 1 super large 19 large and 24 medium sized are known from different geotectonic units of china they contain a total resource of approximately 1000 t of gold 625 t in south china and account for 20 of china s gold reserves these skarn deposits are sited in collisional orogenic belts fault controlled magmatic belts and reactivated cratonic margins all of the chinese skarn gold provinces were affected by phanerozoic collisional orogenesis the timing of the metallogenic events and the spatial temporal distribution of the chinese skarn gold deposits indicates that they were formed during ore forming processes linked to the transition from shortening to extension in the geodynamic evolution of a collision orogen and not to subduction systems as is commonly advocated for porphyry copper systems around the pacific rim

geochemical study of crude oils from the xifeng oilfield of the ordos basin china abstract the xifeng oilfield is the largest newly discovered oilfield in the ordos basin in order to determine the possible source crude oils collected systematically from the oilfield and an adjacent oilfield have been examined isotopically and molecularly the predominance of long chain n alkanes high abundance of c29 sterane lower ratios of c25 c26 tricyclic terpane and c25 tricyclic terpane c24 tetracyclic terpane and high c24 tetracyclic terpane c24 tetracyclic terpane c26 tricyclic terpanes ratio in the studied oils suggest generation from a source with mixed terrigenous and algal bacterial organic matter the presence of diterpenoid hydrocarbon with abietane skeletons is characteristic of the main contribution of higher land plants to the oils the biomarker distributions in the oils show that they were formed under a weakly reducing freshwater environment molecular maturity parameters indicate that the crude oils are mature the oil source rock correlation and oil migration investigation suggest that the oils in the xifeng oilfield originated from the source rocks of the yanchang formation deposited in a shallow to deep freshwater lacustrine environment especially chang 7 source rocks the data from the distribution of pyrrolic nitrogen compounds indicate that the charging direction of the chang 8 crude oils is mainly from the zhuang 12 well northeast of the oilfield toward the southwest this direction of oil migration is consistent with that indicated by regional geological data