Polish Carpathian Foredeep Research Articles

Environmental perturbations around the Badenian/Sarmatian (Middle Miocene) boundary in the Central Paratethys: Micropalaeontological and organic geochemical records

The boundary between the two regional Middle Miocene stages (the Badenian and Sarmatian) of the Central Paratethys is associated with the largest faunal turnover event in the Paratethys realm. A recent study performed in the northern Polish Carpathian Foredeep revealed that the Badenian/Sarmatian boundary is coeval with a major change in benthic and planktonic foraminiferal assemblages that occurs a few metres below the beginning of the Anomalinoides dividens Interval Zone in our section. The lowermost Sarmatian biozone is the Elphidium angulatum Partial Range Zone, and its lower boundary corresponds to the disappearance of almost all Badenian foraminiferal species. Detailed analysis of a fully cored borehole in southern Poland using micropalaeontological tools (foraminifera and palynology) and a range of (inorganic and organic) geochemical methods indicated that during the late Badenian and almost the entire profile of Anomalinoides dividens Zone, oxic or suboxic sedimentary conditions prevailed. In the Elphidium angulatum Zone and the lowest part of the subsequent Anomalinoides dividens Zone, suboxic and anoxic conditions dominated the sea bottom. This research indicated that the sudden disappearance of marine Badenian species in the Polish Carpathian Foredeep was caused by a rapid change in basin chemistry although not necessarily it implies open marine conditions changing to brackish water environments.

Lithological zoning and stable O and C isotopes distribution in carbonates in the Polish native sulfur deposits: Implications for origin of the ores

The northern marginal part of the Polish Carpathian Foredeep hosts numerous native sulfur deposits associated with the Middle Miocene evaporite horizon. These deposits reveal lithological zoning, wherein both the barren and sulfur-bearing limestone zones are embedded within the gypsum basin area (zone). However, such zoning is incompatible with the bioepigenetic formation model of native sulfur deposits. Hence, their genesis remains enigmatic. Regional variations in stable oxygen and carbon isotope values of the limestones disclosed in the Osiek–Baranów Sandomierski native sulfur deposit are inconsistent with the molecular replacement of solid sulfate by calcium carbonate and native sulfur accumulations that expand from a fault zone into the gypsum basin. Instead, the distribution patterns of stable isotopes and sedimentological data suggest that a very shallow freshwater-dominated sedimentary–diagenetic environment developed in the hypersaline basin’s marginal zone, where the mixing of meteoric and highly saline water, as well as various bacterial processes, were responsible for lithological zoning and native sulfur distribution. The proposed results necessitate a reinterpretation of the epigenetic model of native sulfur ore formation.

A Technique of Hydrocarbon Potential Evaluation in Low Resistivity Gas-Saturated Mudstone Horizons in Miocene Deposits, South Poland

The petrophysical properties of Miocene mudstones and gas bearing-heteroliths were the main scope of the work performed in one of the multihorizon gas fields in the Polish Carpathian Foredeep. Ten boreholes were the subject of petrophysical interpretation. The analyzed interval covered seven gas-bearing Miocene horizons belonging to Sarmatian and Badenian deposits. The water saturation in shaly sand and mudstone intervals was calculated using the Montaron connectivity theory approach and was compared with Simandoux water saturation. Additionally, the Kohonen neural network was used for qualitative interpretation of four PSUs (petrophysically similar units), which represent the deposits of comparable petrophysical parameters. This approach allowed us to identify the sediment group with the highest probability of hydrocarbon saturation. Then, the spatial distribution of PSUs and reservoir parameters was carried out in Petrel. The resolution of the model was selected to reflect the variability of log-derived parameters. The reconstruction of the spatial distribution of shale volume, porosity, and permeability was performed with standard parametric modeling procedures using the Gaussian random function simulation stochastic algorithm, while PSU distribution and hydrocarbon saturation (SH) required a separate approach. The distribution into PSU groups was carried out by facies classification. Predefined ranges of clay volume, effective porosity, and permeability were used as discriminators to achieve spatial distribution of the PSU groups. The spatial distribution of hydrocarbon saturation was performed by creating the meta-attribute of this parameter and then reducing the derived pseudo-saturation model to physical values. Results included the creation of maps of hydrocarbon saturation that show the preferable areas with the highest hydrocarbon saturation for each gas horizon.

Foraminiferal and calcareous nannoplankton biostratigraphy of the upper Badenian–lower Sarmatian strata in the SE Polish Carpathian Foredeep

The Badenian/Sarmatian boundary in the Central Paratethys has been traditionally identified by the faunal turnover recording an important environmental change possibly controlled by the change from marine to brackish conditions. The strata below the Badenian/Sarmatian boundary in the northern Carpathian Foredeep are included into the Pecten beds, and those above it into the Syndesmya beds. Foraminiferal study of the Babczyn 2 borehole which is one of the crucial sections in the northern Carpathian Foredeep, well-known for the depositional age of rhyolite tuff within the Pecten beds dated by Śliwiński et al. (2012) at 13.06 ±0.11 Ma, indicated that in fact the boundary occurs within the Syndesmya beds. This conclusion is based upon the rapid change from a stenohaline foraminiferal fauna to a euryhaline one, and the appearance of the species Anomalinoides dividens , the taxon regarded as the marker for the Sarmatian. In the Babczyn 2 and Cieszanów 1 (located ~2.5 km basinward of Babczyn 2) boreholes, Anomalinoides dividens appears 3.1–3.8 m above the replacement of stenohaline by euryhaline foraminifers. The calcareous nannoplankton study shows that the upper Badenian and the lower Sarmatian strata in the studied sections represent the NN6, undivided NN6-NN7, and NN7 zones.

Seismic Identification of Unconventional Heterogenous Reservoirs Based on Depositional History—A Case Study of the Polish Carpathian Foredeep

An integrated geological and geophysical approach is presented for the recognition of unconventional targets in the Miocene formations of the Carpathian Foredeep, southern Poland. The subject of the analysis is an unconventional reservoir built of interlayered packets of sandstone, mudstone and claystone, called a “heterogeneous sequence”. This type of sequence acts as both a reservoir and as source rock for hydrocarbons and it consists of layers of insignificant thickness, below the resolution of seismic data. The interpretation of such a sequence has rarely been based on seismic stratigraphy analysis; however, such an approach is proposed here. The subject of interpretation is high-quality seismic data of high resolution that enable detailed depositional analysis. The reconstruction of the depositional history was possible due to the analysis of flattened chronostratigraphic horizons (Wheeler diagram). The identification of depositional positions in a sedimentary basin was the first step for the indication of potential target areas. These areas were also subject to seismic attribute analysis (sweetness) and spectral decomposition. The seismic attribute results positively verified the previously proposed prospects. The results obtained demonstrate that the interpretation of the Miocene sediments in the Carpathian Foredeep should take into account the depositional history reconstruction and paleogeographical analysis.

The evolution of the Carpathian Foredeep Basin during the latest Badenian and Sarmatian (Middle Miocene): inferences from micropalaeontological data

Seven Middle Miocene (Upper Badenian to Lower Sarmatian) sedimentary sections of the Central Paratethys, two from the Polish Carpathian Foredeep Basin (PCFB) and five from the Eastern Carpathian Foreland Basin (ECFB) of Romania and the Republic of Moldova have been analysed micropalaeontologically to better constrain the Badenian-Sarmatian Extinction Event, characterized by significant taxonomic impoverishment of both foraminifers and ostracods. Our studies show significant palaeoenvironmental changes in the basin including depth, salinity, oxygenation, and organic matter flux. The occurrence of moderately diverse planktonic foraminifera (Globigerina, Globigerinita, Globorotalia, Trilobatus, Orbulina, Velapertina) in the Upper Badenian deposits of the PCFB as well as in the ECFB and their rarity in the lowermost Sarmatian indicate an almost fully marine environment during the latest Badenian, followed by a significant regression and possible appearance of much more restricted marine conditions across the boundary. The taxonomic composition of the Sarmatian foraminifera, ostracoda and calcareous nannofossils indicate that during this interval the salinity fluctuated strongly, with the water regime varying from brackish to normal marine. In addition, the identified micropalaeontological assemblages identified show palaeoenvironmental similarity across different basins of the Central Paratethys. This supports a hypothesis of possible connections during the latest Badenian between different areas of the Central Paratethys, as well as of the existence of a gateway between the Central Paratethys and the Mediterranean realm

Origin of hydrocarbon and noble gases, carbon dioxide and molecular nitrogen in the Miocene strata of the eastern part of the Polish Carpathian Foredeep: Isotopic and geological approach

Fifteen natural gas samples were collected from the autochthonous Miocene strata between Dębica and Przemyśl towns in the eastern sector of the Polish Carpathian Foredeep. The samples were analysed for the molecular and stable isotope compositions of carbon (δ13C in CH4, C2H6, C3H8, i-C4H10, n-C4H10 and CO2), hydrogen (δ2H in CH4, C2H6 and C3H8), nitrogen (δ15N in N2), and all stable isotopes of noble gases (He, Ne, Ar, Kr and Xe) in order to reveal the origin and migration pathway of these gases. Methane concentrations usually exceeded 90 vol%. Methane was mainly generated by microbial carbon dioxide reduction. The rhythmic and cyclic deposition of clays, muds and sands in the Miocene marine basin facilitated and intensified microbial processes. Microbial ethane can be produced by methanogenic Archaea from acetate via reduction. Ethane partly contains a minor component generated from early mature thermogenic process. Propane and butanes were also generated thermogenically. The hydrocarbon gases in the Miocene horizons IIA and IIIA of the Góra Ropczycka field were generated at higher maturity thermogenic process than the rest of the analysed Miocene gases probably from the Middle Jurassic type III kerogen. They migrated to the Miocene horizons from the underlying Upper Jurassic horizon IV of the same field along a fault. Carbon dioxide of the analysed Miocene gases was mainly generated by primary microbial processes. Moreover, the total carbon constrained in the analysed Miocene gases from 0.1 to 6 wt% contained mantle-derived carbon, and thus carbon dioxide mantle component. Molecular nitrogen was mainly generated during low-temperature thermal transformation of organic matter. It might also involve a relatively insignificant component released from NH4-rich illites of the clayey facies of Miocene strata and an atmospheric component delivered by recharge of air-saturated seawater to the reservoir. Inorganic fluid supply from greater lithospheric depth would not be responsible for the promotion of thermal transformation of organic matter. Molecular nitrogen from Miocene horizons in the Góra Ropczycka field was generated during the thermal transformation of organic matter of higher maturity than the rest of Miocene gases, and migrated from the Upper Jurassic horizon along a fault. Helium is dominated by its radiogenic component, with a minor contribution from the mantle. The almost constant mixing ratios of the two helium components in the natural gases from Miocene horizons of various depths suggest that He migrated from a common inorganic deep-seated source in the lithosphere. The other noble gases are dominated by atmospheric components delivered to the hydrocarbon reservoirs by recharge of air-saturated seawater, with minor nucleogenic 21Ne, radiogenic 40Ar, and sedimentary Kr and Xe contributions. The atmospheric component is isotopically fractionated for Ne, and elementally fractionated with various degrees. The ratios of radiogenic 4He to nucleogenic 21Ne or radiogenic 40Ar are higher than the crustal production ratios, suggesting fractionation during thermal release from their host minerals and/or phase related fractionation during their transport to the gas reservoirs. The striking similarity in noble gas isotopic/elemental ratios of the Góra Ropczycka gas from the Miocene horizon IIIA to the nearby reservoir in Mesozoic strata is consistent with gas migration along a fault system.

Experimental insights into consolidation rates during one-dimensional loading with special reference to excess pore water pressure

Consolidation rate has significant influence on the settlement of structures founded on soft fine-grained soil. This paper presents the results of a series of small-scale and large-scale Rowe cell consolidation tests with pore water pressure measurements to investigate the factors affecting the consolidation process. Permeability and creep/resistance structure factors were considered as the governing factors. Intact and reconstituted marine clay from the Polish Carpathian Foredeep basin as well as clay–sand mixtures was examined in the present study. The fundamental relationship correlating consolidation degrees based on compression and pore water pressure was assessed to indicate the nonlinear soil behaviour. It was observed that the instantaneous consolidation parameters vary as the process progresses. The instantaneous coefficient of consolidation first drastically increases or decreases with increase in the degree of consolidation and stabilises in the middle stage of the consolidation; it then decreases significantly due to viscoplastic effects occurring in the soil structure. Based on the characteristics of the relationship between coefficient of consolidation and degree of dissipation at the base, the consolidation range that complies with theoretical assumptions was established. Furthermore, the influence of coarser fraction in clay–sand mixtures in controlling the consolidation rates is discussed.

Results of the comprehensive interpretation of well logs in carbonate and siliciclastic rocks – similarities and differences in the case studies of selected formations

This paper was made using geological and well logging data from the Cuban oilfield area and the Polish Carpathian Foredeep gas deposit to compare the interpretation process and underline similarities and differences between data analysis from two reservoir rocks of different lithology. Data from conventional hydrocarbon deposits, i.e. the Mesozoic Cuban carbonate formation and Miocene shaly-sandy sediments were processed and interpreted using Techlog (Schlumberger Co.) software. Selected approaches were used to determine the step by step volume of shale, total and effective porosity, water/hydrocarbon saturation (Quanti) and for the comprehensive interpretation of well logs (Quanti Elan). Brief characteristics of the carbonate and siliciclastic formations were presented to indicate that the interpretation methodology oriented to the determination of petrophysical properties depends strongly on the type of reservoir. Cross-plots were presented for primary mineral composition recognition, determination of m exponent and resistivity of formation water in the Archie equation. Effective intervals for the carbonate reservoir were calculated according to the Cumulative Hydrocarbon Column methodology. Finally, the results of the interpretation of well logs were presented as continuous curves of mineral composition, including shaliness, porosity and hydrocarbon saturation. The conclusions included recommendations for the effective comprehensive interpretation of well logs in the carbonate and siliciclastic reservoirs.

Radio-isotopic age and biostratigraphic position of a lower Badenian tuffite from the western Polish Carpathian Foredeep Basin (Cieszyn area)

The early Badenian interval in the Central Paratethys realm is characterized by a major marine transgression into the Pannonian and Carpathian Foredeep basins. In the western part of the Polish Carpathian Foredeep, Badenian sedimentation started generally with conglomerates (Debowiec Formation) passing into a thick succession of claystones and mudstones with rare sandstone interbeds (Skawina Formation). Profiles containing a full sequence of lower Badenian strata are relatively rare, and are mainly known from boreholes. In this paper, we present new results on samples taken from such a borehole (Kaczyce K2/07) located near the town of Cieszyn. We focus on reconstructing the chronology of the lower Badenian marine sediments at the beginning of the transgression in the Carpathian Foredeep (lower Skawina Fm.) using radio-isotopic dating ( 40 Ar/ 39 Ar) of a volcanoclastic layer (tuff and tuffite) and biostratigraphy of calcareous nannoplankton and foraminifera.The weighted mean 40 Ar/ 39 Ar age for sanidine separates from the tuff provided an age of 14.27 ± 0.03 Ma. This age is consistent with the NN5 and MNN5a nannofossil zones determined in this study. Our foraminiferal assemblages show that the basal beds of the Skawina Formation up to the tuffites correspond to the Orbulina suturalis–Praeorbulina glomerosa Zone (according to Cicha et al., 1975) and cover the interval of the Lower Lagenidae Zone–lowermost Upper Lagenidae Zone (Grill, 1941). The petrographic data from the tuffite allow correlation of the tuffite from the Kaczyce K2/07 borehole to the level of the Chelmek Tuffite Bed (Alexandrowicz, 1997) providing a regional correlation horizon for future studies.

Interpretation of a gas chimney in the Polish Carpathian Foredeep based on integrated seismic and geochemical data

AbstractGas chimneys are common in offshore petroliferous basins, but little known on land where seismic columnar anomalies are often attributed as poor data quality or processing artefacts. This study utilizes high‐quality 3D seismic data to document a seismic columnar anomaly penetrating through the Miocene heterolithic submarine fan‐deltaic infill of the Carpathian Foredeep. The interpreted gas chimney exhibits vertically clustered velocity push‐down features throughout the attenuated amplitude column accompanied by gas shows in well tests, has its root in gas‐bearing Palaeozoic interval and culminates in an anomalous geochemical gas record at soil level. The chimney system, ca 2 km in height and 500‐m wide, begins above the flank of a rotational bedrock fault‐block and extends vertically along a fault‐controlled conduit. At shallower levels, it passes upwards into amplitude wipeout zones that spread laterally around and partly across thin, gas‐charged reservoirs showing bright spots associated with an AVO response. At shallow levels, gas pathways through muddy slope and deltaic clinoforms are not imaged in low‐fold regions of the seismic volume. The surface geochemical anomalies, in contrast to the microbial methane signature of the Miocene succession, show significant enrichment in higher alkanes and alkenes with C2H6/C3H8 ratios indicative of a deep‐sourced, thermogenic gas or gas condensate. These anomalies form a semi‐enclosed halo around the chimney. Despite the juxtaposition of biogenic and thermogenic methane, the chimney structure imaged on seismic data supports a causal link of gases derived from Palaeozoic source rocks ascending to the surface.

A deep palaeovalley in the floor of Polish Carpathian Foredeep Basin near Pilzno and its control on Badenian (Middle Miocene) evaporite facies

The Pogorska Wola palaeovalley of combined tectonic and erosional origin dissects the Mesozoic floor of the Carpathian Foredeep Basin to a depth exceeding 1200 m. It formed during Paleogene times presumably due to fluvial and submarine erosion, concentrated along a local pre-Late Badenian graben system. All members of the foredeep’s Badenian-Sarmatian sedimentary fill attain distinctly greater values inside the palaeovalley than on top of elevated plateaux on palaeovalley shoulders. The fill comprises the Early to Late Badenian sub-evaporite Skawina Formation, the laterally equivalent Late Badenian evaporite Krzyzanowice and Wieliczka formations and the supra-evaporite Late Badenian to Early Sarmatian Machow Formation. Over the plateaux and in the highest palaeovalley segment, the evaporites are developed in the sulphate facies Krzyzanowice Formation, whereas in the lower palaeovalley segments chloride-sulphate facies evaporites of the Wieliczka Formation occur. The rock salt-bearing rocks are involved in thrusting and folding at the Carpathian orogenic front, which helps to assess the lateral extent of the Wieliczka Formation in seismic records. The deep palaeotopographic position of the evaporites inside the palaeovalley, combined with their lithological and sedimentary features, point to their formation via subaqueous gravity flow-driven redeposition of originally shallow-water evaporites, preferentially halite-bearing, presumably combined with precipitation from sulphate and chloride brines at the palaeovalley floor. Both the redeposited sediments and the brines must have come from the adjacent plateaux and from a thrust-sheet top basin, approaching from the south on top of the Cretaceous-Paleogene Carpathian flysch thrust wedge

Quantitative studies of the calcareous nannoplankton of Sarmatian deposits: case studies in the Sieniawa–Rudka area (Outer Carpathian Foredeep, Poland)

The aim of this study was the qualitative and quantitative analysis of the calcareous nannofossil assemblages of the Machow Formation, belonging to the supra-evaporitic complex of the Polish Carpathian Foredeep Basin (PCFB). The work was concentrated in the eastern part of the PCFB, in the Sieniawa–Rudka area (Ryszkowa Wola Horst). Samples were collected from the Rudka-13 and Wylewa-1 boreholes. On the basis of calcareous nannoplankton, these deposits were assigned to the upper part of the NN6 Zone combined with the NN7 Zone, which corresponds to the Sarmatian s.s. of the Central Paratethys (upper Serravallian of the Mediterranean scale). Conclusive determination of the biozone NN7 was problematic, owing to the absence of the rare zonal marker species Discoaster kugleri . The typical association of the undivided NN6–NN7 Zone was of low species diversity and usually dominated by Coccolithus pelagicus , C yclicargolithus floridanus and Reticulofenestra pseudoumbilica (> 7 µm). On the basis of the relative abundance of species, a significant amount of redeposition was deduced. The reworked nannofossils were mostly Eocene in age. The Oligocene, Early Miocene and Late Cretaceous species occurred much less frequently. The dominance of Eocene forms indicates the Carpathians as the main supply area. The Late Cretaceous taxa may have originated from the Senonian marly deposits of the Miechow Trough in the north. Statistical treatment of the quantitative data was performed using multivariate cluster analysis and Nonmetrical Multidimensional Scaling (nMDS). The composition of the calcareous nannofossil assemblages, together with the high percentage of allochthonous taxa, indicate a shallow, coastal environment with a high supply of nutrients.

Strontium isotope composition of Middle Miocene primary gypsum (Badenian of the Polish Carpathian Foredeep Basin): evidence for continual non‐marine inflow of radiogenic strontium into evaporite basin

AbstractStrontium isotope compositions of ancient sulphate deposits not only provide chemostratigraphic information but also offer insight into the system in which the evaporites precipitated. Primary gypsum from two Middle Miocene (Badenian) sections in southern Poland shows steadily higher 87Sr/86Sr ratios than those expected from a marine‐derived formation. The ratios are interpreted as the result of increasing inflow into the basin at the time of gypsum precipitation. Palaeogeographic reconstructions suggest that riverine runoff sources were situated in the West and East European platforms (to the north and east, respectively) and the Carpathians (to the south), which are mostly composed of Mesozoic sedimentary rocks; their dissolution cannot be responsible for the higher 87Sr/86Sr ratios recorded. We conclude that Archaean and Palaeoproterozoic igneous and supracrustal rocks of the Ukrainian Shield were the source of the higher 87Sr/86Sr ratios recorded in the Badenian primary gypsum. A distinctive decreasing trend of 87Sr/86Sr ratios from western Ukraine to southern Poland is explained by a consistent direction of brine inflow during gypsum crystallization (typical cyclonic circulation controlled by the Coriolis effect).

Dynamic stratigraphy of composite peripheral unconformity in a foredeep basin

AbstractThis study employs facies analysis and basic principles of sequence stratigraphy to correlate isolated outcrop sections and reveal the depositional history of the Chmielnik Formation – a prominent mid‐Serravalian clastic wedge formed on the basinward forebulge flank of the Polish Carpathian Foredeep. The coarse‐grained clastic wedge, up to 30 m thick and spanningca1·1 Ma within biozoneNN6, consists of fluvio‐deltaic, foreshore and shoreface deposits with a range of large littoral sand bars, all enveloped in muddy offshore‐transition deposits. Its dynamic stratigraphy indicates rapid shoreline shifts and environmental changes due to the interplay of forebulge tectonism, sediment supply and third‐order eustatic cycles. A similar interplay of tectonism and eustasy is recognizable in the whole middle Miocene sedimentary succession deposited on the forebulge flank, demonstrating an extreme case of an accommodation‐controlled shelf and indicating tectonic cycles of the forebulge uplift and subsidence spanningca800 to 900 ka. The episodes of forebulge uplift correlate with the main pulses of orogen thrusting. The resulting composite peripheral unconformity differs markedly from the idealized model of a ‘steady‐state’ stepwise onlap driven by forebulge continuous retreat. It is concluded that the foredeep peripheral unconformities, instead of being simplified in accordance with this idealized model, should rather be studied in detail because they bear a valuable high‐resolution record of regional events and give unique insights into the local role of tectonics, eustasy and sediment supply.

Reservoir properties and facies characterization from core data and well logging: autochthonous Miocene sediments in the Carpathian Foredeep case study

Laboratory results of total porosity and physical permeability were the basis to calculate Flow Zone Indicator and GR log and porosity log were used for facies identification in the Miocene sandy-shaly sediments in two wells in the Eastern Part of Polish Carpathian Foredeep. There was observed FZI increase with the total porosity from the comprehensive interpretation of logs in the regressive set of parasequences what can be interpreted as better reservoir and hydraulic abilities of them in comparison to transgressive ones. Combining laboratory origin information with well logging results on the basis of facies and FZI correlation worked also as a kind of data scaling.

Integration of core, well logging and 2D seismic data to improve a reservoir rock model: a case study of gas accumulation in the NE Polish Carpathian Foredeep

Geological models play a crucial role in the description and simulation of fluid flow of both hydrocarbon- and water-bearing strata. Methodology, based on the hydraulic flow unit build on the basis of core plug data combined with rock types determined from logs and 3D seismic cubes generated on the basis of 2D seismic sections is presented. It works as a possible exploration tool for the Miocene gas accumulations in the Carpathian Foredeep of Poland. Deterministic and stochastic, geostatistical methods were used to construct a static reservoir model from 2D seismic sections, lithological data and hydraulic flow unit data. A pseudo-3D seismic volume was generated from all of the 2D seismic data available, in order to aid the modelling of hydraulic flow units. This approach is applicable to other reservoirs, where the availability of seismic data is limited. This study demonstrates that even without 3D seismic data and with limited well log data, the proposed hydraulic flow unit approach can be successfully applied to reservoir modelling through the integration of diverse data sets for a wide range of scales

Foraminiferal record of marine transgression during deposition of the Middle Miocene Badenian evaporites in Central Paratethys (Borków section, Polish Carpathian Foredeep)

AbstractBenthic and planktonic foraminifera from a marly clay intercalation sandwiched between mid‐Badenian (Middle Miocene) gypsum deposited in an environment of an evaporitic shoal (<1 m deep) at Borków (southern Poland) indicate a major marine flooding event in the previously isolated Carpathian Foredeep Basin (Central Paratethys). After this very short‐term environmental change, benthic foraminifers started to colonize a new niche which was previously defaunated, and the pattern of benthic foraminiferal colonization is similar to that related to the reflooding which terminated the Badenian evaporite deposition. The benthic foraminifer assemblages are composed of pioneer, opportunistic, r‐selected species dominated by elphidiids. The connection of the Carpathian Foredeep Basin with the marine reservoir was short‐lived. The marly clay intercalations in evaporite sequences originating in bared basins can thus register major environmental changes.

Statistical analysis of petrophysical parameters of Middle Miocene rocks from the Polish Carpathian Foredeep

Normal 0 21 false false false PL X-NONE X-NONE MicrosoftInternetExplorer4 Sarmatian thin-bedded sandy-shaly formation was a subject of statistical studies to differentiate between good and poor reservoir rocks and to show gas-saturated layers in comparison to water-saturated formation. Statistical studies including fractal analysis were performed on well logging data from well S-34 drilled in a belt of hydrocarbon deposits that continued below the northern edge of the Carpathian-Stebnik overthrust. Lithological variability and porosity differentiation and changes in water saturation were traced on the basis of results of well logging interpretation. Basic statistics and histograms of petrophysical parameters were investigated. A generalized fractal correlation dimension of the second order was calculated for all parameters and analyzed in the same way as time series. Fractal dimensions did not correlated with the parameters, but good positive correlations between them and parameters were observed and proved that the analyzed curves had the same type of complexity. High correlation coefficients showed pairs of fractal dimensions for those parameters which had similar variability and the same curve roughness. Fractal correlation dimension described the type of complexity of the parameter (curve roughness) and indicated, for example, how shaliness influenced the reservoir properties of Middle Miocene. Therefore, the results had also the practical side, which gave extra information on thin-bedded reservoir rock formations. Sarmatian thin-bedded sandstone and shales have been a subject of statistical studies to differentiate between good and poor reservoir rocks and to show gas-saturated layers in comparison to water-saturated strata. Statistical studies including fractal analysis were performed on well logging data from the Sędziszów 34 borehole drilled in a belt of hydrocarbon deposits that continue below the northern edge of the Carpathian–Stebnik overthrust. Lithological variability and porosity differentiation and changes in water saturation were traced on the basis of the results of well logging interpretation. Basic statistics and histograms of petrophysical parameters have been analysed. A generalized second order fractal correlation dimension was calculated for all parameters and analysed as for a time series. Fractal dimensions did not correlated with the parameters, but good positive correlations between them and the parameters were observed and showed that the curves analysed had the same type of complexity. High correlation coefficients showed pairs of fractal dimensions for those parameters which had similar variability and the same curve roughness. The fractal correlation dimension described the type of complexity of the parameter (curve roughness) and indicated, for example, how shaliness influenced the reservoir properties of the local Middle Miocene. Therefore, the results were also useful in practice, which gave extra information on thin-bedded reservoir rocks.  

Structure and Miocene evolution of the Gdów tectonic “embayment” (Polish Carpathian Foredeep) – a new model based on reinterpreted seismic data

Analysis of previously available stratigraphic data coupled with the re-interpretation of seismic profiles calibrated by boreholes has allowed the construction of a new tectonic model of evolution of the Gdów “embayment” – a tectonic re-entrant located along the Carpathian front east of Kraków (southern Poland). This model shows that the main phase of localized fault-controlled subsidence took place in the Early Badenian and was associated with deposition of the locally overthickened Skawina Formation. Also, deposition of evaporites of the Wieliczka Formation seems to have been tectonically controlled by local basement faulting. Supra-evaporitic siliciclastic deposits have developed as a result of overall north-directed sediment progradation from the eroded Carpathian belt towards the Carpathian Foredeep. During the final stages of development of the Carpathian fold-and-thrust wedge the previously subsiding Gdów “embayment” area was uplifted and basement faults were reactivated either as reverse faults or as low angle thrust faults. Along the leading edge of this inverted structure a triangle zone developed, with backthrusting along the evaporitic level. As a result, overthickened evaporites, formed in local tectonically-controlled depressions within the area of the Gdów “embayment” area have been strongly folded and internally deformed Trailing edge of the Carpathian fold-and-thrust belt between Kraków and Tarnów has been subjected to intense studies because of its control over rich deposits of rock salt (Wieliczka and Bochnia salt mines) and hydrocarbon accumulations. In vicinity of Gdów, Carpathian orogenic front in the area south-east of Kraków recedes to the south, forming a “bay” or “embayment” filled with the Miocene deposits of the Carpathian foredeep basin. Over decades, numerous tectonic models of the Gdów “embayment” have been published. Originally, sedimentary infill of the “embayment” was identified as the Lower Badenian sub-evaporitic (Skawina Beds), with remnants of the Upper Badenian foredeep evaporites only locally preserved at the surface or shallow subsurface. Later, although without sufficiently presented micropalaeontological evidences, new models have been proposed that assumed dominance of the supra-evaporitic Machów Formation (Chodenice and Grabowiec Beds). Analysis of available stratigraphic data coupled with interpretation of good quality seismic profiles calibrated by deep wells allowed for construction of a new tectonic model of evolution of the Gdów “embayment”. Under this model, main phase of localized fault-controlled subsidence took place in Early Badenian and was associated with deposition of locally overthickened Skawina Formation. Also deposition of evaporites of the Wieliczka Formation was locally tectonically controlled, similarly to earlier models by Garlicki (1971). Supra-evaporitic siliciclastics have developed as a result of an overall north-directed sediment progradation from the eroded Carpathian belt towards the Carpathian foredeep. During final stages of development of the Carpathian fold-and-thrust wedge previously subsiding Gdów “embayment” area was uplifted, basement faults have been reactivated either as a reverse or low angle thrust faults. Along the leading edge of such inverted structure a triangle zone developed, with backthrust formed along the evaporitic level. As a result, overthickened evaporites, formed in local, tectonically-controlled depressions present within the Gdów “embayment” areahave been strongly folded and internally deformed. Analysis of previously available stratigraphic data coupled with the re-interpretation of seismic profiles calibrated by boreholes has allowed the construction of a new tectonic model of evolution of the Gdów “embayment” – a tectonic re-entrant located along the Carpathian front east of Kraków (southern Poland). This model shows that the main phase of localized fault-controlled subsidence took place in the Early Badenian and was associated with deposition of the locally overthickened Skawina Formation. Also, deposition of evaporites of the Wieliczka Formation seems to have been tectonically controlled by local basement faulting. Supra-evaporitic siliciclastic deposits have developed as a result of overall north-directed sediment progradation from the eroded Carpathian belt towards the Carpathian Foredeep. During the final stages of development of the Carpathian fold-and-thrust wedge the previously subsiding Gdów “embayment” area was uplifted and basement faults were reactivated either as reverse faults or as low angle thrust faults. Along the leading edge of this inverted structure a triangle zone developed, with backthrusting along the evaporitic level. As a result, overthickened evaporites, formed in local tectonically-controlled depressions within the area of the Gdów “embayment” area have been strongly folded and internally deformed