Facies Types Research Articles

A detailed stratigraphic and taphonomic reassessment of the late Paleozoic fossil flora from Promontory Butte, Arizona

A late Paleozoic, likely early Late Pennsylvanian (Missourian/early Virgilian), flora from Promontory Butte, Arizona, USA is the westernmost assemblage of this age yet described from northern Pangea. The palynological species pool is similar to that typical of more central parts of the supercontinent; in contrast, the macroflora differs by facies, reflective of original habitat differentiation. The flora is preserved in a succession that includes sandstone, siltstone, shale, and conglomerate in an upward-fining series of beds. A break between the siltstone and shale is marked by an organic-shale bed, previously described as a coal, and its underclay/paleosol. This stratigraphic unit is interpreted as an active channel fill terminating in a lake. A detailed bed-by-bed facies analysis of the macroflora, focusing on the relationship between sedimentological features and fossil-plant composition reveals that the wetland floral elements are concentrated in the upper, fine-grained beds of the fill, including the organic shale and overlying mudrock, whereas the drought-tolerant, xeromorphic plants are concentrated in siltstones and sandy siltstones below the organic-shale/underclay couplet. Palynology, in contrast, suggests a uniform flora throughout the interval, indicating that macrofloral changes within the channel-fill sequence reflect microhabitat differences resulting from local changes in soil moisture conditions rather than climate change. The palynoflora is dominated by tree ferns and compositionally suggests a Missourian (Kasimovian) age, possibly early Virgilian; rare lycospore grains, characteristic of the Middle Pennsylvanian, are likely reworked from older sediments. Earlier collecting at this site did not sort the fossils by microstratigraphy and facies types, combining all floral levels into one assemblage that indicated possible co-occurrence of wetland plants and plants tolerant of seasonal moisture stress. Furthermore, a Pennsylvanian-Permian boundary age was inferred due to the abundance of xeromorphic, drought-tolerant taxa. In light of this investigation, a late Missourian age is inferred as most likely.

Depositional Architecture and Reservoir Quality Assessment of Abu Roash (G) Dolomite, as a Low Resistivity Pay, Razzak Oilfield, Western Desert, Egypt.

Abu-Roash (G) dolomite (A/R-G) is considered one of the most prolific oil-bearing reservoirs in the Western desert. In this study, Razzak Oilfield was selected to investigate the geological and petrophysical findings of these successions that were assigned stratigraphically to the upper Cretaceous (Late Cenomanian), in the Alamein basin. Sedimentologically, three main facies groups have been recognized in the studied successions of A/R-G and include dolostone, limestone and mudstone facies; and depositional; are divided into three parts: A) Back-reef to reef crest (Reefal depositional setting) - dolostone facies group; graded to B) Inner-ramp of limestone / dolomitic limestone facies types; then C) mud-flat (intertidal setting) of calcareous mudstone facies type. Petrophysically, most of the recorded pore sizes in the dolomite zone are mesopores (≈1 micron), with scattered macropores (2-10 microns), as identified by MICP on some selected 1.5” core plugs. In general; A/R-G dolomite displays low resistivity pay (high conductivity) due to: A) The heterogeneity of moldic and vuggy pore size distributions (macropores); associated with the dominant intercrystalline-dolomite mesopores; and B) Fe-rich minerals that increase the conductivity; where most of the identified dolomite crystals are secondary, late-diagenetic stage ferroan dolomite; and confirmed that petrographically by thin-section analysis.

Structures and fabric sedimentary of overland flow generated in laboratory experiments – fluids composed of low concentrations (≈ 3 vol %) of soil aggregates

The sedimentary arrangement generated by overland flows remains an open question, particularly due to the sediment concentration variations of this flow. We create a laboratory experiment to answer a question: what type of facies and structures can low concentration overland flows (≈ 3 vol%) generate in a steep-planar hillslope context with a gently sloped sand accommodation area? Our experiment revealed that noncanalized low sediments concentration are supercritical and turbulent. On the sedimentation plain, flows exhibited progressive deceleration implying three flow stages (arrival-flow, intermediate-flow and waning-water flow). In the first stages, flows remained supercritical and turbulent, and in the last stage, they became subcritical and turbulent. Parting lineation was the predominant surface feature for the three flow stages, followed by tool marks, rills and coarse aggregate accumulation. The recurrence of flows implicated in parting lineation reworking, scour-and-fill, and horizontal airscape structures. The arrival-flow stage developed erosive depression, in which sediments were incorporated into the flow. These flow characteristics and sedimentary structures can occur in the real world and are related to overland flow recurrence.

Study of the Hydrochemical Characterization of Drinking Water from the Aquifer of the Town of Guitté at Hadjer Lamis

A hydrogeological study was carried out in and around Guitté. This study aims to contribute to the understanding of the hydrochemical parameters of the waters of the Guitté aquifer. with a view to the sound and sustainable management of available water resources. A field mission to measure and sample borehole water was carried out from March 26 to 28. 2023 in and around Guitté. Physicochemical analyses were carried out on 28 water samples from human-driven pumps). The study showed that the groundwater exploited in this area has an average temperature of 29°C. Overall. the pH values measured in the sampled waters are not very heterogeneous and are around neutral. Electrical conductivity values are highly heterogeneous. Two types of chemical facies have been identified in Guitté groundwater: sodium or potassium bicarbonate facies. and calcium and magnesium bicarbonate facies. The overall quality of the groundwater obtained for consumption is 60.71% rated as good. 39.28% as poor. The origin of the mineralization could be linked. on the one hand. to water/rock contact. due to the dissolution of natron. limestone. gypsum and thenardite and on the other hand. to the phenomenon of intense evaporation.

Textural complications of banded iron formation and the potential production of nano-magnetite: a case study from the Central Eastern Desert of Egypt

The current work makes integrated value-added, geological and chemical studies on the texturally intricate banded iron formation “BIF” that is represented here, as a case in point, by the Um Nar BIF located in the Central Eastern Desert of Egypt. Geologically, the Um Nar BIF is composed mainly of oxide-rich facies and silicate-rich facies mostly expressed as bands of variable thickness (90–730 µm). Magnetite, martite, goethite, and quartz are detected as the main components of the oxide-rich facies, while epidote, stilpnomelane, and garnet occupy the other facies type. The studied ore can be classified as a low-grade iron ore containing 51.23 wt.% Fe2O3 and 39.64 wt.% SiO2 along with considerable phosphorous content (1.01 wt.% P2O5). These elemental concentrations do not match the recommended benchmarks for iron and steelmaking (e.g.75.78–95.8 wt.% Fe2O3, 5–7 wt.% SiO2, and 0.04 wt.% P2O5). Moreover, the studied BIF has a poor liberation behavior on crushing and grinding due to the complex interlocking of magnetite with quartz and stilpnomelane expressed as a sieve-like texture. This textural complication directed the current work to investigate the potential exploitation of the Um Nar BIF as a precursor of nano-magnetite that is commonly synthesized by ferrous and ferric chlorides. Accordingly, HCl-based agitation leaching followed by co-precipitation was carried out, resulting in ultrafine nano-magnetite (2.47–4.27 nm particle size) expected to serve in water treatment as an effective adsorbent for heavy metals.

Assessment of Groundwater for Drinking and Irrigation in Kalanaur Block (Rohtak) Haryana, India

Groundwater is an essential source of drinking and irrigation in rural areas across the globe. Water pollution is among the leading problem in causes of health-related disorders all over the world. Physico-chemical analysis of water gives an insight into the quality of water. Various physical and chemical parameters were examined to calculate the water quality index (W.Q.I.) in villages of the Kalanaur block of Rohtak district (Haryana), India. The suitability of groundwater for irrigation purposes was determined by calculation of Sodium Adsorption Ratio (S.A.R.), Sodium Percent (Na %), Residual Sodium Carbonate (R.S.C.) and Permeability Index (P.I.), U.S. salinity plot, Wilcox diagram, etc. Most water samples were of high W.Q.I., indicating poor water quality. A minimum value of W.Q.I. was 58.38 for S17 and the maximum was 454.41 for S12. Most of the parameters analyzed suggested that water was polluted due to very high concentrations of T.D.S., chloride, magnesium and bicarbonate ions. S.A.R., Na %, R.S.C. and P.I. values were in the excellent to good range. Piper trilinear plot indicated that most of the water samples belonged to mixed Ca-Mg-Cl and Ca-HCO-3 type of water facies. Gibbs plot suggested a significant interaction between water and rocks in the area. Almost 50% of the water samples were suitable for irrigation.

Devonian diamond reservoir of the Urals

Research subject. The Takata formation of the Emsian tier of the Lower Devonian (D1tk) in the Urals is a reservoir of Devonian diamonds. Aim. Confirmation and determination of the diamond-bearing conditions of the reservoir. Materials and Methods. Generalization of primary and interpreted geological information. Lithofacial analysis. Historical and geological reconstruction. Cartographic analysis and geological and cartographic modeling in the ArcMapESRY GIS environment using the ModelBuilder module. Results. The Takata formation is part of the Emsian tier of the Lower Devonian. Tectonically, the Takata formation is located in the West Ural Folded Zone. The diamond content in the Urals is spatially related to the outputs of the Takata formation. The industrial diamond-bearing capacity and the highest density of diamond placers are located in the Vishersky, Chykmansky and Chusovskoy diamond-bearing regions of the Northern and Middle Urals within the Perm Krai. In the early Devonian, the Takata Sea existed in the Vishera diamond-bearing area; a large river with a delta flowed in the direction from northwest to southeast. The sediments of the formation comprise the facies cycle: flood-plain - channel alluvium - delta sediments - underwater-delta - marine sediments. Diamonds are concentrated in the thickness of coarse-grained alluvium, small-pebble basal conglomerates that formed on the land-sea boundary of the paleocontinent of the Russian Plate. Three facies types of the Takata formation section are distinguished: continental, coastal-marine and marine. Its diamond-bearing capacity is associated with the continental and coastal-marine sediments of the formation within the Perm Region. To the north and south of the diamond-bearing areas of the Perm Krai, the Takata formation is represented by marine sediments. According to the geodynamic model based on the geological section of the Northern Urals, the alluvial and coastal-marine Takata diamond placers were formed in the early Devonian as a result of the demolition of material from the Russian Plate. The sources of destruction were rocks of the Precambrian, Ordovician and Silurian. The main spatial-geomorphological criterion for searching for diamond-bearing conglomerates of the Takata formation is the maximum distance of demolition from these conglomerations to placers, equal to 500 m.

Research on the Construction Method of a Training Image Library Based on cDCGAN

There is a close relationship between the size and property of a reservoir and the production and capacity. Therefore, in the process of oil and gas field exploration and development, it is of great importance to study the macro distribution of oil–gas reservoirs, the inner structure, the distribution of reservoir parameters, and the dynamic variation of reservoir characteristics. A reservoir model is an important bridge between first-hand geologic data and other results such as ground stress models and fracture models, and the quality of the model can influence the evaluation of the sweet spots, the deployment of a horizontal well, and the optimization of the well network. Reservoir facies modeling and physical parameter modeling are the key points in reservoir characterization and modeling. Deep learning, as an artificial intelligence method, has been shown to be a powerful tool in many fields, such as data fusion, feature extraction, pattern recognition, and nonlinear fitting. Thus, deep learning can be used to characterize the reservoir features in 3D space. In recent years, there have been increasing attempts to apply deep learning in the oil and gas industry, and many scholars have made attempts in logging interpretation, seismic processing and interpretation, geological modeling, and petroleum engineering. Traditional training image construction methods have drawbacks such as low construction efficiency and limited types of sedimentary facies. For this purpose, some of the problems of the current reservoir facies modeling are solved in this paper. This study constructs a method that can quickly generate multiple types of sedimentary facies training images based on deep learning. Based on the features and merits of all kinds of deep learning methods, this paper makes some improvements and optimizations to the conventional reservoir facies modeling. The main outcomes of this thesis are as follows: (a) the construction of a training image library for reservoir facies modeling is realized. (b) the concept model of the typical sedimentary facies domain is used as a key constraint in the training image library. In order to construct a conditional convolutional adversarial network model, One-Hot and Distributed Representation is used to label the dataset. (c) The method is verified and tested with typical sedimentary facies types such as fluvial and delta. The results show that this method can generate six kinds of non-homogeneous and homogeneous training images that are almost identical to the target sedimentary facies in terms of generation quality. In terms of generating result formats, compared to the cDCGAN training image generation method, traditional methods took 31.5 and 9 times longer. In terms of generating result formats, cDCGAN can generate more formats than traditional methods. Furthermore, the method can store and rapidly generate the training image library of the typical sedimentary facies model of various types and styles in terms of generation efficiency.

Sedimentary Facies Types and Their Control of Reservoirs in the Lower Jurassic Lacustrine Facies Shale of the Lianggaoshan Formation, Northeastern Sichuan Basin, China

In recent years, new breakthroughs have been made in the field of shale oil and gas exploration in the Lower Jurassic Lianggaoshan Formation in Sichuan Basin. At present, there is a lack of systematic studies on reservoir properties and sedimentary facies of the Lianggaoshan Formation shale. Therefore, in this study, taking the Lianggaoshan Formation in Sichuan Basin as an example, the sedimentary facies types of shale reservoirs and their control over shale oil and gas are systematically studied, based on a large number of outcrops, experimental testing, logging, and seismic interpretation methods. The results show that five sedimentary microfacies are developed in the Lianggaoshan Formation in the study area, namely, semi-deep lake mud, shallow lake mud, wave-influenced shallow lake mud, delta-influenced shallow lake mud, and underwater interbranch bay microfacies. The stratum thickness of the Lianggaoshan Formation is in the range of 26–315 m, and mainly distributed in the eastern region, but rapidly thinned in the northwestern region. The sedimentary sequence framework of the Lianggaoshan Formation has been constructed. Moreover, the lithology of the Lianggaoshan Formation shale has been divided into three types, including shale, massive mudstone and silty mudstone. The brittleness index and total organic carbon (TOC) value of three types of shale show a negative correlation. Silty mudstone has the highest brittleness, while that of black shale is the lowest. For porosity and permeability, massive mudstone is better than silty mudstone, and silty mudstone is better than black shale. There are many kinds of matrix pores in the Lianggaoshan Formation shale, and the development degree of inorganic pores is higher than that of organic pores. Finally, based on the analysis of oil-bearing, pore types, physical properties and productivity, it is considered that black shale facies is the most favorable lithofacies type. The deep–semi-deep lacustrine facies belt obviously controls the shale oil enrichment of the Lianggaoshan Formation.

Deposition, Diagenesis, and Geochemistry of Upper Cretaceous Carbonates (Sarvak Formation) in the Zagros Basin and the Persian Gulf, Iran

Upper Cretaceous carbonate rocks of the Sarvak Formation are among the most important hydrocarbon reservoirs of the Middle East. This paper summarizes the depositional history, diagenetic alteration, and geochemistry of this formation in south and southwest Iran. The combined effects of tectonic activities and the paleoclimate had remarkable control over the depositional–diagenetic evolution of this formation. Large changes in facies types, their frequency, and thickness were recorded across the study area and attributed to the tectonic activities. The complex diagenetic history of this formation includes minor marine, intensive meteoric, and burial diagenesis. Two pronounced paleoexposure events were recorded at the Cenomanian–Turonian boundary (CT-ES) and the middle Turonian (mT-ES), which are associated with remarkable changes in facies and diagenetic characteristics and special geochemical trends. Elemental (Mg, Fe, Rb, Mn, Sr), isotopic (carbon, oxygen), and 87Sr/86Sr ratios provide useful tools for delineating the paleoexposure surfaces, their associated diagenetic alterations, and chemo-sequence stratigraphic interpretation. Variable exposure durations resulted in immature to over-matured karstified profiles below the CT-ES and mT-ES, respectively. Meteorically dissolved rudist-dominated facies provided the best reservoir zone of the Sarvak Fm. in the regressive systems tract of the Cenomanian sequence, just below the CT-ES. Microporous and dolomitized mud-dominated facies formed the second important reservoir intervals, especially within the transgressive systems tracts. The results of this study revealed that the reservoir characteristics of the Sarvak Fm. were considerably controlled by paleoexposure events and, therefore, it can be considered as a typical paleokarst hydrocarbon reservoir in Iran.

“Tri-in-One” Accumulation Model of Lithologic Reservoirs in Continental Downfaulted Basins: A Case Study of the Lithologic Reservoir of Nantun Formation in Tanan Sag, Mongolia

This article analyzes the key controlling factors and hydrocarbon distribution rules of lithologic reservoirs in a continental downfaulted basin according to the structural features, sedimentary evolution, types of sedimentary facies, source rock features, diagenesis evolution, reservoir features, hydrocarbon formation mechanisms, exploration status, and hydrocarbon resource potential. The results show that three major controlling factors (sandbody types, effective source rocks, and effective reservoirs) and one coupled factor (fractures that act as a tie) influence hydrocarbon accumulation in the lithologic traps in the Nantun Formation in Tanan Sag. With the increase in depth, sufficient hydrocarbon is generated in the source rock with thermal evolution. When the depth threshold is reached and critical conditions of hydrocarbon supply are met, hydrocarbon generation and expulsion are more intensive. Traps that are surrounded or contacted by source rock or connected by faults are able to form reservoirs. As the buried depth increases, the intensity of hydrocarbon generation–expulsion grows, and the trap is more petroliferous. Hydrocarbon accumulation and reservoir formation are also controlled by sandbody accumulation conditions. When the critical conditions for hydrocarbon generation are met and concrete oil and gas are charged in, the better physical properties of the sandbody will always indicate more hydrocarbon accumulation in the trap. The allocation of sand type, effective source rock, and an effective reservoir is optimized under the effect of fractures and the coupled hydrocarbon reservoir with these three elements.

Geological Assessment of Turonian - Coniacian terrestrial sedimentation records during climatic recovery, Moreno Hill Formation, Zuni Basin

Understanding of Upper Cretaceous terrestrial sediments within the Western Interior Basin is advancing; however, the Turonian–Coniacian transition remains enigmatic. Recent chronometry of the Moreno Hill Formation indicates that sediment deposition took place during this interval of geodynamic upheaval and climatic recovery immediately following the peak of the Cretaceous Thermal Maximum (CTM). To decipher these effects, the sedimentary record of the Moreno Hill Formation was reassessed near the type section, and near Quemado, New Mexico (USA) using facies analysis and architectural reconstruction. Seven facies types (thirteen lithofacies codes), eleven architectural elements, and three facies associations were identified. Sedimentation within the floodplain of the lower Moreno Hill Formation was affected by the east-migrating forebulge of the Western Interior Basin. Furthermore, increasingly bedload-rich multi-story channel complexes and a transition from near-coastal to alluvial coals reflect gradual climatic cooling and overall regression of the Western Interior Seaway (with interruption by a regional [T2–R2] transgressive-regressive sequence). This is consistent with more subaerial conditions indicative of continued regression reflected within the floodplain sediments of the upper Moreno Hill Formation. Whilst diversion of westerly fluvial feeder systems by ongoing forebulge migration also affected sediment transport and deposition, a return to more suspended-load-rich single-story channels and thin coals are tied to an intervening (T3) transgression. Repetitive paleosol sequences throughout the Moreno Hill Formation indicate groundwater fluctuation in response to these base level changes. Together with detrital zircon-based geochronology, these slight sedimentary differences support a revised subdivision from three into two members: lower and upper. Beyond feeding the seaward Gallup Delta, the newly defined lower member correlates to the Toreva, Straight Cliffs (Smoky Hollow member), Ferron Sandstone, Funk Valley and Frontier formations (Dry Hollow Member) and the upper member to the Wepo and Straight Cliffs (John Henry Member) formations within the Kaiparowits, Notom, Last Chance and Vernal fluvio-deltaic systems. Landward sediments of the Cardium Formation (Canada) correlate with the lower and upper members of the Moreno Hill Formation.

Logging evaluation of petrophysical facies based reservoir quality prediction method for the volcanic rocks in the deep depth of Nanpu Sag, China

The volcanic rocks in the deep depth of Nanpu sag is the main formation of oil and gas enrichment. It has huge resource potential and prospects for exploration and development. Accurate characterization of lithology and pore space is the basis of reservoir quality prediction. Through petrography studies of cores and thin sections, explosive and sedimentary facies represent the dominant oil and gas-bearing reservoirs, and intergranular pores and fractures are major pore and seepage space. In order to predict favorable reservoirs and improve the efficiency of fracturing, according to composite well loggings and electrical images, logging response features of different lithofacies are characterized and five types of pore structure facies are classified. Further, five types of petrophysical facies are proposed. Among them, Type I and Type II are the most favorable petrophysical facies in the study area. The petrophysical facies typing approach show consistency with oil test data, which verifies that this approach can well predict reservoir quality and provide technical support for the exploration and development of the oil and gas-bearing volcanic rocks.

Assessment of Hydrochemical Facies on Groundwater Quality in Daenaa Village and its Surroundings, West Limboto District

The study is required to evaluate the groundwater condition, such as finding the relationship with the lithology, determining the facies of groundwater, and providing an overview of the present groundwater conditions, genetics, and groundwater quality. This study aims to explain the relationship between lithology and groundwater chemistry, groundwater quality, and the determination of the chemical facies of groundwater to determine the genetic type of groundwater. This study uses field survey methods and random sampling techniques, measurements of groundwater physical properties, trilinear piper diagrams, and laboratory analysis in the form of rock geochemical analysis (XRF) at the PSDMBP Laboratory and chemical analysis of groundwater at the PT Global Quality Analytical Laboratory. The results show that the lithology in the study area consists of clastic limestone, sandstone, breccia, and dacite. Lithology in the study area primarily plays an essential role in chemical ion enrichment in groundwater. Determination of groundwater quality is based on Permenkes, Permen ESDM, and ISDW, which obtained eleven well points in the good quality category, five well points in the poor quality category, and four other well points categorized as poor quality. Based on the analysis results in the trilinear piper diagram, there is one type of groundwater chemical facies (not varied), namely the Ca-Cl type facies. The presence of the Ca-Cl facies type is interpreted as a seawater intrusion phase.

The Best Scenario for Geostatistical Modeling of Porosity in the Sarvak Reservoir in an Iranian Oil Field, Using Electrofacies, Seismic Facies, and Seismic Attributes

Summary The lateral and vertical variations in porosity significantly impact the reservoir quality and the volumetric calculations in heterogeneous reservoirs. With a case study from Iran’s Zagros Basin Sarvak reservoir in the Dezful Embayment, this paper aims to demonstrate an efficient methodology for distributing porosity. Four facies models (based on electrofacies analysis data and seismic facies) with different geostatistical algorithms were used to examine the effect of different facies types on porosity propagation. Both deterministic and stochastic methods are adopted to check the impact of geostatistical algorithms on porosity modeling in the static model. A total of 40 scenarios were run and validated for porosity distribution through a blind test procedure to check the reliability of the models. The study’s findings revealed high correlation values in the blind test data for all porosity realizations linked to seismic facies, ranging from 0.778 to 0.876. In addition, co-kriging to acoustic impedance (AI), as a secondary variable, increases the correlation coefficient in all related cases. Unlike deterministic algorithms, using stochastic methods reduces the uncertainty and causes the porosity model to have an identical histogram compared with the original data. This study introduced a comprehensive workflow for porosity distribution in the studied carbonate Sarvak reservoir, considering the electrofacies, and seismic facies, and applying different geostatistical algorithms. As a result, based on this workflow, simultaneously linking the porosity distribution to seismic facies, co-kriging to AI, and applying the sequential Gaussian simulation (SGS) algorithm result in the best spatial modeling of porosity.

SEDIMENTOLOGY, PALAEOGEOGRAPHY AND DIAGENESIS OF THE UPPER PERMIAN (Z2) HAUPTDOLOMIT FORMATION ON THE SOUTHERN MARGIN OF THE MID NORTH SEA HIGH AND IMPLICATIONS FOR RESERVOIR PROSPECTIVITY

This paper provides an updated understanding of the reservoir stratigraphy, sedimentology, palaeogeography and diagenesis of the Upper Permian Hauptdolomit Formation of the Zechstein Supergroup (“Hauptdolomit”) in a study area on the southern margin of the Mid North Sea High. The paper is based on the examination and description of core and cuttings data from 25 wells which were integrated with observations based on existing and new 3D seismic.Based on thin‐section petrography of cuttings and core from the wells studied, it is evident that Hauptdolomit microfacies are distributed in a relatively predictable way, and well‐defined platform interior, platform margin, slope and basin settings can be distinguished. Platform margins are typically characterised by the development of ooid shoals and, to a lesser‐extent, by microbial build‐ups. High‐energy back‐shoal settings are characterised by a more complex combination of peloid grainstones, thrombolitic and microbial build‐ups, and fine crystalline dolomites. Lower energy lagoons which developed further behind the platform margin are characterised by a variety of microfacies types; fine crystalline dolomites are common in this setting as well as peloidal facies and local microbial build‐ups. Intertidal and supratidal settings are typified by increased proportions of anhydrite and the development of laminated microbial bindstones (stromatolites). Platform margins are in general relatively steep and pass into slope and basinal settings. Only a few wells have penetrated Hauptdolomit successions deposited in a slope setting, and these successions are characterised by a range of resedimented shallow‐water facies together with low‐energy laminated dolomicrites and fine crystalline dolomites. Slope zones in the study area are interpreted from seismic data to be typically 1‐1.5 km in width. Basinal Hauptdolomit deposits have been strongly affected by post‐depositional diagenesis and are dedolomitised to variable degrees. The original depositional facies are rarely preserved.Diagenetic studies show that dolomitisation has affected almost the entire Hauptdolomit Formation throughout the study area in both basinal and platform settings. The dolomite is considered to result from seepage‐reflux processes and is an early diagenetic phase. Mouldic porosity is present in many facies types as a result of dissolution, especially in ooid grainstones, thrombolitic build‐ups and peloidal facies. The dissolution cannot be associated with any one diagenetic phase but was most likely a result of the dolomitisation process itself. Stable isotope analyses indicate that all dolomites were precipitated from Permian marine‐derived pore fluids. Fluid inclusion analyses of dolomite cements indicate that cementation continued into the burial realm. Anhydrite cementation occurs in two phases: early anhydrite precipitation was associated with dolomitisation, and can be distinguished from a later, pore‐filling cement which is highly detrimental to reservoir quality.The Hauptdolomit succession in basinal wells (and in some slope wells) in the study area has undergone significant dedolomitisation. Dedolomitisation was a shallow burial process which affected precursor dolomites, whereby excess calcium from the transition of gypsum to anhydrite during burial combined with CO2 and organic acids derived from basinal sediments. The process was triggered by excess calcium reacting with excess carbonate ions from dissolution.3D seismic volumes supplemented by numerous 2D lines were available in the study area and allowed an interpretation to be made of Hauptdolomit gross depositional settings; platform margins and base‐of‐slope polygons were mapped, with the greatest confidence in areas of 3D seismic. The basin, slope and platform settings were distinguished using seismic data integrated with the results of micro‐facies analysis and incorporating seismic‐to‐well ties. The data shows that large parts of the study area are characterised by the presence of polyhalites within the overlying (Z2) Stassfurt Halite Formation, which may create particular seismic geometries at the Hauptdolomit slope. These are interpreted to be intra‐Stassfurt Halite features, providing an alternative model to the thickened, prograded Hauptdolomit which has been suggested in previous publications.Because few wells drilled in the study area had the Hauptdolomit as the primary target, cores were limited but significant data was obtained from cuttings analyses. More than 400 thin sections were evaluated, allowing depositional models based on microfacies observations to be developed, verifying the seismic‐scale observations.

Hydrogeochemical evolution and mineralization origin in a semi-arid shallow aquifer: a case study of the Barika area in northeast Algeria

Most Middle Eastern and North African regions are characterized by an arid and semi-arid climate. As such, the drinking water supply and management have become a challenging task for local and regional authorities. The Mio-Plio Quaternary aquifer of the Barika area is the only drinking and irrigation water reservoir in the region. The objective of this paper is to identify the origin and evolution process of the groundwater mineralization of this aquifer using major elements as indicators. To achieve this objective water samples were collected, from several boreholes drilled in the aquifer, in June 2018 and March 2019, and subsequently analyzed. The results obtained in terms of Gibbs plot, Piper, chemical correlation, and statistical analysis of chemical data identified the origins of groundwater mineralization. The dissolution of evaporated minerals, precipitation of carbonates, evapotranspiration, and ion exchange reactions have been identified as the primary processes of mineralization. The results of the physicochemical analysis showed that these waters consisted mainly of chloride, calcium sulfate, and magnesium facies types with a slight change of facies in some boreholes during the two sampling periods. This is due to the interactions with the-aquifer geology and to the water scarcity caused by climate change.

Geochemical and mineralogical evaluation of Libale iron- rich manganese deposit, North-central Nigeria

The iron-rich manganese deposits of Libale area is located within the basement complex of North-central Nigeria. Mineralogically, the major mineral phases are: goethite (Fe2O3.H2O), spessartine (Mn32+Al2(SiO4)3), hematite (Fe2O3), and quartz (SiO2), while minor mineral phases are orthoclase (Al2O3.K2O.6 SiO2), illite (KAl2Si3AlO10(OH)2), and manganite (Mn2O3.H2O) suggesting a trend of mineral assemblage attributed to the differential mineralization of the iron-manganese deposit that may have been caused by the geochemical tectonic activity during its formation. Geochemically, on average, the Fe2O3, SiO2, Al2O3, CaO, P2O5 content are 34.59 wt.%; 26.30 wt.%; 6.94 wt%, 2.60 wt%, 2.01 wt% correspondently while K2O and TiO2 are less than 1wt%. Suggesting oxide facies type for the deposit. The trace element composition of V (1040 ppm), Cr (100 ppm), Co (833.33 ppm), Cu (1740 ppm), Nb (1280 ppm), W (240 ppm), Ta (320 ppm) and Zr (302 ppm) were relatively high compared to Maro, Muro and Kakun BIFs in North-central Nigeria. Bivariate plot of Fe2O3 Vs. Al2O3, suggest enrichment of Fe2O3 but depleted in SiO2 and Al2O3, which possibly indicates replacement of precursor silica and kaolinite with goethite which are subsequently dehydrated to hematite. Al2O3-SiO2-Fe2O3 ternary diagram indicates Precambrian Banded Iron Formation (BIF) for the Libale iron- rich manganese deposits, this was confirmed by MnO Vs. FeO. Discriminative plots: FeO. SiO2 - (FeO + MnO) - Fe2O3 and Al2O3+ K2O + Na2O Vs. MnO + FeO confirmed mixed facies as the analyzed data plots between silicate facies and magnetic-silicate facies, this is linked to chemical association between Al2O3 and SiO2 for the iron-rich as it confirms a transitional grade of silicate facies to magnetite-silicate facies. SiO2 Vs. Al2O3 plot revealed hydrothermal and diagenetic processes for its deposition. The iron-rich manganese deposit is of low grade iron (Av. Fe=24.19%) characterized by ferruginous manganese (Av. MnO2=23.82%) based on the generalized percentages of element of major interest in assessing quality of iron and manganese ore, therefore, good for cast iron production.

Facies, Depositional Environment and Reservoir Quality of an Early Cambrian Carbonate Ramp in the Tarim Basin, NW China

The Xiaoerbulake Formation in the Tarim Basin is considered one of the most important deep to ultradeep hydrocarbon reservoirs in the world. The objective of the present study is to analyze the facies, depositional environment and reservoir quality of the Early Cambrian Xiaoerbulake Formation in the Tarim Basin through integrated analysis of 120 m of cores, 3240 m of well cuttings, wireline logs and over 1100 thin sections from 17 exploration wells. Early Cambrian Xiaoerbulake Formation deposits in the Tarim Basin were deposited on a ramp setting. The ramp was occupied by seven facies associations and ten facies types ranging from the inner ramp to the outer ramp. These facies associations include tidal flat, lagoon, high-energy shoal, sabkha, inter-shoal, low-energy shoal and open shelf. Their distribution was controlled by paleogeographic patterns, sea level changes and the paleoclimate. Reservoir quality is considerably affected by facies together with diagenetic processes, including dolomitization and anhydrite cementation. High-quality reservoirs are found in the dolograinstone of high-energy shoal environments, which are favorable exploration facies in the carbonate ramp. Their pore space types consist of interparticle pores, intraparticle pores, intercrystalline pores, vuggy pores and moldic pores, with a porosity of 1.4%–7.5%. This study will help with our understanding of the stratigraphic framework, sedimentary-facies evolution and high-quality reservoir distribution of the Early Cambrian carbonate ramp in the Tarim Basin, facilitating exploration and the production of hydrocarbons from the Xiaoerbulake Formation.

The Sedimentary records of the Hapcheon impact crater basin in Korea over the past 1.3 Ma

The Hapcheon impact crater is the only meteorite impact crater identified on the Korean peninsula. However, the morphology of the impact crater and the nature of the meteorite collision are unknown. In this study, we analyzed the sedimentary facies using grain size data; computed tomography images, 14C, 10Be, and optically stimulated luminescence dating on a >66-m-long sediment core (20HCL04) recovered from the Hapcheon Basin. Four sedimentary units and 10 types of facies were documented in the Hapcheon Basin sediment core. The sedimentary units comprise 1) a lower part (unit 1) that is dominated by moderately to well-sorted coarse gravel, which contains some impact-related sediments; 2) a middle part (units 2 and 3) dominated by well-laminated mud; and 3) an upper part (Unit 4) that is dominated by poorly sorted coarse gravel supplied from the surrounding mountain slopes by alluvial and fluvial processes. After the meteorite impact, the Hapcheon impact crater was filled with deposits from the crater wall after ca. 1.3 Ma and the Hapcheon Basin became a deep lake environment. After ca. 0.5 Ma, sediments were supplied from the surrounding mountains until the lake was filled. Finally, sediments were deposited in an alluvial fan setting. In addition, the Hapcheon Basin sedimentary cores contain a tephra layer and deformed soft sediments that can be used to investigate volcanic and seismic events on the Korean Peninsula over the past 1.3 Ma.