Formation Lower Jurassic Research Articles

Geochemical characteristics of dolomite: a case study from lower jurassic formations, imbricated zone, Iraqi Kurdistan region

Geochemical characteristics of dolomite: a case study from lower jurassic formations, imbricated zone, Iraqi Kurdistan region

Selective oil saturation of Verkhnechimidikeenskoe oil manifestation

The article considers the problem of possible oil-bearing of the section’s upper part in the area of permafrost’s distribution on the example of the north-east of the Siberian platform. The actual data testifying to the existence of permeable intervals in the permafrost rocks (PFR) are presented. The main attention is paid to the unusual «hanging» distribution of oil inside the sand formation. This low-thickness lower Jurassic formation contains a concentration of oil of a lensoid shape. At the same time unaltered areas of the sand formation (without saturation) surrounding top and bottom saturated part do not differ in lithological characteristics. The assumption about the relevance of the Verkhnechimidikeenskoe Oil Manifestation to the relic inter-permafrost aquifer is made. As a modern analogue, the sufficiently detailed distribution zone of inter-permafrost aquifers on the northern slope of the Aldanskaya anteclise with similar lithological-stratigraphic performance is briefly described.

Effects of overpressure on deep sandstone reservoir quality: A case study of the Medium and Lower Jurassic formation in the Shawan Sag, central Junggar Basin, western China

This study focuses on the Medium and Lower Jurassic sandstone reservoir in the Shawan Sag, central Junggar Basin to demonstrate the impacts of overpressure on deep reservoir quality. Based on thin section observation and mineral identification, compaction heterogeneity and different petrofacies were identified by mathematical statistics. The compaction degree and typical cements content of different petrofacies under different overpressure systems were analysed to qualitatively evaluate the heterogeneous influence of overpressure on reservoir quality. The evolution of palaeo-pressure and porosity for typical wells were restored using basin modelling, and then the effects of overpressure on reservoir quality were quantitatively analysed. The results reveal that deep sandstones exhibit compaction heterogeneity owing to petrological properties and calcite cement, resulting in different petrofacies: ductile-rich sandstone, calcite-cement sandstone, and ductile-lean sandstone. Ductile-rich sandstone and calcite-cement sandstone, which were nearly or already tight before the on-set of overpressure, were free from the effects of overpressure. Ductile-lean sandstone maintained better reservoir quality from overpressure. The effects of overpressure were heterogeneous, which were comprehensively controlled by grain size, the content of rigid grains, overpressure strength and the on-set and duration of overpressure. The basin modelling results show differences in grain size and the content of rigid grains for the Medium and Lower Jurassic formation, resulting in varying levels of porosity preservation. The Medium Jurassic formation, whose pressure coefficient is 1.9, shows 1.69% porosity preservation, whereas the Lower Jurassic formation, whose pressure coefficient is 1.3, shows 1.59% porosity preservation. With the development of overpressure, quartz overgrowth was restrained, whereas smectite-illitization and carbonate cements were free from the late overpressure effects. The research results deepen the existing understanding of the formation mechanism of deep effective reservoirs.

Geochemical characteristics and oil–oil correlation of the upper Cretaceous oils from the Iranian part of the Persian Gulf Basin

The Cenomanian Sarvak oil reservoirs are distributed over large areas of the Persian Gulf basin. The purpose of this study is analyzing the geochemical characteristics of the Sarvak oil reservoirs and their inter-relationships in the Persian Gulf, classification of the Sarvak oil samples and investigation of the possible causes of the genetic difference in oil families. In the previous studies, limited samples of Sarvak oil reservoir in scarce oilfields were studied individually and local interpretations are made accordingly. The current study employs a more complete set of geochemical from the Iranian part of Persian Gulf and regional interpretations are drawn. To achieve this goal, the geochemical data of 41 oil samples from 10 oilfields were collected and assessed based on gas chromatography (GC), gas chromatography–mass spectrometry (GC–MS), and stable carbon isotope analysis. It was demonstrated with the evaluations that the oils accumulated in the Upper Cretaceous Sarvak reservoirs in the Persian Gulf basin originate from different source rocks. The oil samples are genetically classified into four oil families based on the similarities and differences of parameters related to the depositional environment-dependent parameters using hierarchical cluster analysis (HCA), star diagram, and stable carbon isotope diagram. The source rocks were mainly deposited in anoxic marine carbonate environments. The thermal maturity of the oils was evaluated using steranes and trisnorhopanes. Oil families 2 and 4 (located at the center of the Persian Gulf) have the highest thermal maturity compared to the other samples; in contrast, oil family 1 (located at the west of the Persian Gulf) has the lowest thermal maturity. The possible source rocks of oil family 1 and family 3 (located at eastern Persian Gulf) using C28/C29 steranes are the upper Cretaceous successions; in contrast, the possible source rocks of oil families 2 and 4 are the upper Triassic and Lower Jurassic formations. Results of the study show a high similarity between the oils of families 2 and 4, which are located at the center of the Persian Gulf; these results also recognize the significant difference between these two oil families and oil families 1 and 3. The significant issue raised in this study is to find out the reason for this difference. The structural analysis of the central Persian Gulf shows that huge vertical faults created by salt domes intrusion provided the migration pathways for trapping oil in Sarvak reservoirs. The oils of the Surmeh, Fahliyan, and Dariyan reservoirs have migrated upwards through these faults to be trapped in the Sarvak Formation across the central Persian Gulf.

E&P Notes (December 2022)

E&P Notes (December 2022)

Structural development of the Korek and Pirat anticlines, Iraqi Kurdistan Region. A tectonic-geomorphological study

The Korek and Pirat mountains are two outstanding geomorphic features in the Iraqi Kurdistan Region (IKR), forming two anticlines. The two anticlines are separated by the Gulley Ali Beg stream. Both anticlines form right-hand en-echelon plunging as the Korek anticlines is concerned. The oldest exposed rocks in the core of both anticlines belong to the Lower Jurassic formations, whereas the Bekhme formation forms the bulk of both anticlines. The Korek anticline includes three domes and its southeastern plunge forms left-hand en-echelon plunge with the Ranya anticline. Whereas, the Pirat anticline includes two long domes with very faint indication. We have interpreted satellite images to indicate different geomorphological forms which are good indication for the lateral growth of the anticlines. Moreover, we have measured different geomorphological and structural aspects; accordingly, we have determined that both anticlines are Detachment Folds.

DetritalU–Pbzircon and40Ar/39Armuscovite geochronology of Triassic and Jurassic strata in the southern East Kunlun, northern Tibet Plateau and their geological implications

Geochronological dating of detrital minerals from sedimentary rocks can provide invaluable records of the erosional and unroofing history of orogenic systems and link specific sources with their sinks in sedimentary basins. Aiming to establish a better understanding of the thermal and erosional evolution of the East Kunlun Orogenic Belt (E‐KOB), northern Tibet Plateau during the Mesozoic, integrated detrital U–Pb zircon, and40Ar/39Ar muscovite dating was applied to Triassic and Jurassic strata in the southern E‐KOB in this study. Detrital U–Pb zircon ages of clastic rocks from Triassic and Jurassic formations show major age populations at 2,600–2,200 Ma, 2,000–1,700 Ma, 1,000–600 Ma, 530–340 Ma, and 320–220 Ma, while the40Ar/39Ar dating of detrital muscovite yield dominantly Devonian ages with uniform early‐middle Devonian peak ages (380–405 Ma). Our new detrital U–Pb zircon and40Ar/39Ar muscovite ages, combined with the previous palaeocurrent data and comparison with published U–Pb zircon, and40Ar/39Ar muscovite ages of potential source areas, suggest that the E‐KOB was the major source for Triassic and Jurassic strata in the southern East Kunlun. Devonian detrital muscovite40Ar/39Ar ages of the Triassic and Lower Jurassic strata are consistent with the age of syn‐ and post‐collisional magmatic activity in E‐KOB related with the post‐collisional thermal relaxation after closure of the Qimantagh back‐arc basin. The Lower Triassic sedimentary deposits were associated with the subduction of the Kunlun Ocean, which is part of the Palaeo‐Tethys Ocean. The E‐KOB‐derived material in Upper Triassic and Lower Jurassic formations implies that significant surface uplift, unroofing and erosion occurred during the Late Triassic and continued into the Early Jurassic in the East Kunlun region.

Geochemical Characteristics of Dolomite: A Case Study from Lower Jurassic Formations, Imbricated Zone, Iraqi Kurdistan Region

Geochemical Characteristics of Dolomite: A Case Study from Lower Jurassic Formations, Imbricated Zone, Iraqi Kurdistan Region

Модели строения и условия формирования глубокопогруженных региональных резервуаров нижнеюрских отложений Енисей-Хатангской и восточной части Гыданской нефтегазоносных областей

Модели строения и условия формирования глубокопогруженных региональных резервуаров нижнеюрских отложений Енисей-Хатангской и восточной части Гыданской нефтегазоносных областей

Variability of lithofacial parameters of Lower Jurassic geothermal aquifer in the Malanów region revealed by interpretation of geophysical well logs and seismic data

The Lower Jurassic aquifer is the main target for exploitation of geothermal waters in the Polish Lowlands as it covers over 80% of the area of Poland. Particularly favorable geothermal conditions dominate in the Mogilno-Łodź Trough (central part of the Polish Lowlands), where that aquifer occurs at greatest depth, which results in high temperatures of geothermal waters. The main Lower Jurassic reservoirs in that area are Sinemurian, Pliensbachian, and Upper Toarcian sandstones. These sediments show high lithofacial variability, which results in local changes of hydrogeothermal parameters. Such local variability can be effectively estimated using the seismic data and the interpretation of well logs. Both methods were used for determination of depths to the top surface of Lower Jurassic formation and of distribution of porosity, and clay content, which enabled the researchers to recognize the spatial arrangement of groundwater horizons. The study area is a local structure within the Mogilno-Łodź Trough, in the vicinity of Malanow village. This is a synclinal structure built of Lower Jurassic strata close to the Turek Salt Pillow. Temperature of groundwater in that structure exceeds 80 °C and favorable reservoir parameters ensure relevant discharge. Sandstone horizons show thicknesses over 50 m, low clay contents and porosity around 0.15–0.20.

Geochemical characteristics and accumulation of hydrocarbon in Lower Jurassic tight sandstone in Wenjisang area, Turpan Basin, NW China

In order to investigate the geochemical characteristics, sources and accumulation process of Lower-Jurassic Sangonghe Formation tight sandstone oil, multiple geochemical analyses were performed on source rocks, oil samples and sandstone particles from Wenjisang area in Turpan Basin. The results show that coal-measure source rocks have relatively higher organic matter abundance and type-II organic matter for Xishanyao and Badaowan Formations, with the potential of liquid hydrocarbon generation. Oil samples of Sangonghe Formation have the characteristics of coal-measure-formed oil. Higher maturity indicate the oil may be mainly generated by Lower-Jurassic Badaowan Formation source rocks. Quantitative fluorescence parameters also reflect that hydrocarbons charged into Sangonghe Formation through continuous migration from the bottom of sand body to the top gradually. In down dip direction of Wenjisang area may develope continuous tight oil and gas reservoirs in Lower Jurassic.

The quality of geothermal reservoir of the Lower Jurassic aquifer in the Mogilno-Łódź Trough (Polish Lowlands)

The assessment of the geothermal potential should always take an accurate identification of the geological conditions into account. Petrographic and petrophysical investigations of the aquifers allow to estimate their productivity and infectivity. The area of the Mogilno-Łódź Trough is next to the Podhale basin, one of the most prospective regions in terms of geothermal potential in Poland. The Lower Jurassic aquifers are characterized by the largest dispositional resources among geothermal aquifers in the Polish Lowlands. The Lower Jurassic geothermal reservoir consist of fine and mixed grain-size sands and sandstones layers from 10-650 m thick, depending on the depth. The water within the reservoir exhibits mineralization ranging from 2 to over 250 g/L and its temperature ranges from 30 to 100°C. Boreholes profiles selected for study consist Lower Jurassic formations of the Polish Lowlands, which are perspective for the heat production in Poland. Sandstones are represent mainly by quartz arenites and subordinate by quartz wackes. Parameters measured include among others porosity, permeability and surface area. The results of the petrographic and mineralogical studies of core samples confirmed the presence of rock with favorable parameters for geothermal water accumulation.

Геологическое строение и сейсмогеологические критерии картирования нефтегазоперспективных объектов нижнеюрских отложений Усть-Тымской мегавпадины

Геологическое строение и сейсмогеологические критерии картирования нефтегазоперспективных объектов нижнеюрских отложений Усть-Тымской мегавпадины

A pragmatic approach for identifying effective lacustrine shale payzones

Compared with the marine shale payzones, lacustrine shale payzones generally contain more interbed layers (e.g., sandstone interbeds and carbonate interbeds), bringing about a higher complexity to the identification of effective lacustrine shale payzones. In this work, a pragmatic but systematic approach is developed to identify the effective lacustrine shale payzones with commercial hydrocarbon-production potentials. Such identification approach is developed based on three easily accessible data sources that are obtained from multiple wells drilled in a given region: 1) well logging data; 2) measured properties of the core samples; and 3) production test data. In this approach, the first step is to identify shale-containing formations based on the lithology profile along a well that has been interpreted using the well logging data. Secondly, a shale-dominated formation is extracted from a given shale-containing formation if the ratio of total shale thickness to the total formation thickness exceeds 60%; this cut-off value is selected based on the consideration that such formation has a higher possibility of industrial production potential. Lastly, a shale-dominated formation can be classified as an effective shale payzone if the total organic carbon (TOC) content, porosity, and effective thickness are all greater than the given threshold values. By using this proposed method, one can obtain the total effective thickness and the regional distribution of effective lacustrine shale payzones, which could help to locate the sweet spot of the shale payzones as well as subsequently design proper methods for recovering the shale resources. The Lower Jurassic formations possess abundant lacustrine shale layers that are widely considered to be the potential lacustrine shale gas payzones in the northwest of Sichuan Basin in China. A case study in this formation is presented to demonstrate the efficacy of the newly developed approach in identifying the effective lacustrine shale payzones. Validation results prove that this new method can be used to effectively identify the effective lacustrine shale payzones with commercial production potentials.

Characteristics and sustainable utilisation prospects of geothermal waters of the liassic formations in the Mogilno\u2013Lodz Trough, Poland

Mogilno–Lodz Trough is located in central Poland. It is structural basin filled with Triassic-to-Quaternary sediments. Lower Jurassic formations in Poland have one of the best conditions for the heating purposes. Presently, on the area of the Trough, no geothermal plant operates, which utilises geothermal waters from Lower Jurassic formations. Sustainable use of geothermal waters covers, e.g., effective use of thermal energy from waters, before they are injected back to the deposit. Such sustainable use can be achieved in cascaded systems, utilising thermal energy of waters, which gradually lose temperature at following stages of cascaded systems. Geothermal waters and energy occurring in Lower Jurassic formations in Mogilno–Lodz Trough have been analysed in terms of chemical composition and temperature parameters. A dominant type of water is chloride-sodium waters, with specific components contents, such as iodine, bromine, and iron. Lower Jurassic formations are deposited at different depths, which affects, to a high extent, water mineralization and temperature, as well as some elements contents. It has been demonstrated which parameters are decisive about a possibility of using them at particular stages of a cascaded system and where one should expect to find suitable conditions for particular applications.

Prediction of shell content from thin sections using hybrid image process techniques

Shell content is an important indicator to evaluate the accumulation capability of carbonate reservoirs, but still needs to be estimated artificially. As such, some techniques that can automatically predict shell content only from stained thin section image are proposed. The processing procedures of those techniques include four steps: binarizing color thin section image; detecting edges of objects; using a special technique to extract shell areas; finally adjusting appearances of those extracted shells by dilating and eroding. Six thin sections used for validating techniques derive from the Lower Jurassic formations of the Sichuan Basin. For these six validated cases, the error between the expected and calculated shell content is 0.51%, 2.59%, 0.93%, 2.31%, 2.14% and 2.75% respectively. Moreover, within each thin section image, the main lithology predicted in accordance with the calculated shell content is consistent with that deduced from the expected shell content. The small errors and exact judgments of the lithology manifest that the proposed techniques are capable to provide the reliable shell content data, and compared to the conventional observation and analysis methods they are cost-efficient when dealing with a large amount of thin section images. Therefore, the proposed techniques have practical value and can be used as the handy tool for geologists in the work of observing and identifying thin section.

The origin and evolution of waters in the Jurassic formations of the Marginal Trough area (Poland)

The Permian–Mesozoic cover of the Western European Platform includes numerous aquifers containing mineralized water. An attempt has been made to determine both the genesis of water from the Jurassic formations of the Marginal Trough (tectonic unit in the Zechstein–Mesozoic structural floor, located in central Poland) and the processes to which they were subjected. The results of archival chemical analysis of waters from deep boreholes located in the Marginal Trough have been studied. Hydrogeochemical ratios of Na/Cl, Cl/Br, (SO 4 × 100)/Cl, HCO 3 /Cl and Na/(Ca + Mg), together with their variability depending on water depth, were presented and discussed. The majority of waters from the Jurassic formations are Na–Cl waters, typical for areas isolated from hypergene zones. Their mineralization is closely related to the depths of the Jurassic formations. The analyses of hydrochemical parameters of the Jurassic waters have shown that the vast majority of these waters are brines or chloride waters, genetically related to seawater. The diversity in mineralization and hydrochemical parameters, together with their dependence on the depth of occurrence of the analysed waters, indicate that waters from the Lower Jurassic formations originate from isolated geological structures, while the Middle and Upper Jurassic waters are/or were affected by infiltration waters.

3D stratigraphic forward numerical modelling approach for prediction of organic-rich deposits and their heterogeneities

The source rock characteristics (e.g. thickness, lateral extension, richness) are known to be highly variable in both time and space. The Lower Jurassic formations of north-western Europe contain source rocks with organic-rich intervals showing different characteristics from one region to another: the Paris Basin differs from the South-East Basin of France, but organic content and hydrogen index also vary within a single basin. During the Early Jurassic, the overall depositional environment of north-western Europe corresponded to an epicontinental domain at the western extremity of the Tethys Ocean. The early transgressive phase of the Jurassic induced flooding of this European realm. Because of the evolution of the connections and threshold of the European basins and their associated sedimentary settings, this domain occupied a key position for the deposition of organic-rich layers. Using a forward modelling approach, we aim to predict the heterogeneous characteristics of such sediments. It is widely accepted that primary productivity and preservation are key factors favouring the accumulation of organic-rich layers. However, the roles of these factors remain to be assessed and the processes leading to accumulation and preservation need to be quantified.We focus on the Lower Jurassic (Hettangian to Toarcian) in France, since this provides a vast amount of data to calibrate the 100-kyr time step model in terms of an accurate framework including paleogeography, stratigraphy, lithology, palaeontology, mineralogy and geochemistry.Results show that favourable conditions for the deposition of organic-rich sediment can occur even with moderate primary productivity and without requiring anoxic conditions. These windows are firstly dependent on internal factors directly linked to the basin morphology, such as sedimentation rate, bathymetry and distance from the coastline. We do not need to evoke external factors such as oceanic anoxic events or enhancement of primary production to account for the deposition of organic-rich sediments.

Hydrogeochemical Modelling of Forming of Geothermal Waters in the Synclinorium of Łódź

The Synclinorium of Łódź, is one of the most prospective areas of geothermal water in central part of Poland. Currently there are two geothermal centers in this region in Uniejów and Poddębice. Moreover, the use of geothermal energy projects have been developed for Łódź, Poddębice, Kleszczów, Piotrków Trybunalski, Radom, Zduńska Wola and Rogóźno. Geothermal water in the Synclinorium of Łódź may be used for the purpose of balneology, recreaction and heating. This unit has an asymmetric structure, which comprises permian-mesosoic sediments placed on the older rocks. First of the all thermal waters are accumulated in the Lower Cretaceous, where the temperature is more than 700C and Lower Jurassic formations with a temperature of about 1000C. Hydrogeochemical zonation of the study area is characterized by the increase of water mineralization and the water chemical type change: HCO3-Ca→ HCO3-Na→Na-Cl→ Cl-Na. All the waters studied have total dissolved solids TDS from 0,2 to 157 g/dm3. Minerals regulating the hydrogeochemical equilibrium in thermal waters in the basin of Łódź are principally quartz and calcite. The hydrogeochemical modelling study of these thermal waters can be explained by the polygenetic origin. In general, the chemical composition of thermal waters in this region is determined by the interaction between the groundwaters (meteoric waters of modern hydrological cycle), the rock environment and the brines from leaching chloride salt ions. The process may depend on pH, mineralization and the occcurrence of other ions and temperature.

Perspectives of using the geological subsurface for hydrogen storage in Poland

The increasing share of renewable energy in electricity production in Poland is part of the growing interest in the hydrogen underground storage. In the search for suitable locations for this purpose it is useful to have the knowledge on the geological structures for underground storage of gases, including carbon dioxide.This article presents the possibilities of geological storage of hydrogen in underground geological structures in Poland (salt caverns, depleted oil and natural gas fields, and deeply seated aquifers). The study results confirm that there are favorable conditions to achieve this goal – in many areas of Poland it is possible to realize some type of hydrogen underground storage.The paper presents prospective areas for different options of hydrogen underground storage at specified conditions. For locations in salt caverns, rock salt deposits from the following areas are proposed: Łeba Elevation, Fore-Sudetic Monocline, Carpathian Foredeep, and salt stocks in the Polish Lowlands. For depleted oil and natural gas fields in the Polish Lowlands, Carpathians and Carpathian Foredeep, a few tens of fields are indicated, most of them are natural gas deposits. In the Polish Lowlands, several anticlinal structures in the Lower Cretaceous and Lower Jurassic formations have been selected. These pre-designated locations may be the basis for further work and detailed considerations in order to find the best and most appropriate locations intended for hydrogen underground storage.