Mudstone Microfacies Research Articles

Mineralogical, petrographical, geochemical, diageneses and provenance of the Cretaceous Black Shales, Duwi Formation at Quseir-Safaga, Red Sea, Egypt

The Duwi Formation in the Quseir-Safaga area is conformably overlain by the Quseir variegated shales and underlain by the Dakhla shales. Detailed mineralogical and geochemical studies were carried out on the middle member of the black shales of the Duwi Formation in Quseir-Safaga province to infer their source rocks, paleo-weathering and provenance of the sources. The studied black shales are highly fossiliferous and fissile. They are texturally classified as phosphatic marly mudstone microfacies. Mineralogically, they are composed mainly of calcite, apatite, quartz, pyrite and clay minerals. The studied clay fraction reveals that the well-crystalline Na-montmorillonite is the dominating clay mineral with mixed layer montmorillonite-illite and minor kaolinite. These shales could be used as a source for the sodium bentonite. The studied black shales are highly mature, detrital and authigenic in origin. They are most probably derived from basic volcanic rocks by intensive chemical weathering. The provenance constituted a part of passive and active continental margins similar to those the Devonian/Mississippian shales in USA. The Cretaceous black shales of the Duwi Formation in Quseir-Safaga area are part of Mes-Neoarchean Shales, and are typically comparable to the Archean Shale Average.The average values of Cu, Ni, Zn, Cr, V, As and Se and, with the ratios Rb/Sr and Cr/Ni, are enriched with respect to those of the PAAS values. This could be attributed to the abundance of mafic components. The felsic source rocks were considered as an added source similar to Cretaceous and Cambrian black shales in India and China; respectively. The ratios V/Cr, V/(V+Ni) and Mo/Al and the high concentrations of the redox sensitive elements revealed that the studied black shales were deposited under relatively euxinic to anoxic reducing marine environments coupled with hydrothermal solutions. They were found comparable to the Cretaceous Gulf of California, Posidonia, Cretaceous/Tertiary black shales, and those in the Black Sea. The studied black shales can be classified as good to excellent source of oil and trace elements. The chemical composition of the studied black shales of the Duwi Formation (Cretaceous) was correlated to published data at different localities and ages.

Microfacies Analysis and Cyclostratigraphy of the Upper Cretaceous-Lower Paleogene Succession of Bir Dakhl Section, North Eastern Desert, Egypt

Abstract: The Bir Dakhl section which is located in the southern Galala plateau, north eastern desert was sampled for microfacies analysis of the upper Cretaceous–lower Paleogene succession. Microfacies analysis led to the recognition of eight mixed clastic-carbonate facies types (black shale lithofacies MF-1, pure shale lithofacies MF-2, sandy shale lithofacies MF-3, marly shale lithofacies MF-4, mudstone microfacies MF-5, foraminiferal wackestone microfacies MF-6, bioclastic wackestone microfacies MF-7, and bioclastic packstone microfacies MF-8) of the studied interval. These microfacies can be grouped into three depositional environments: inner, middle and outer ramp. The interpreted depositional environments have been suggested to range from neritic to middle bathyal (∼ 700 m). Based on cyclostratigraphy, five deepening upward cycles and three shallowing upward cycles have been differentiated in Bir Dakhl section.

Electrical, mineralogical, geochemical and provenance of Cretaceous black shales, Red Sea Coast, Egypt

Detailed mineralogical and geochemical studies were carried out on the middle members of the black shales of the Duwi Formation (Quseir–Safaga province) to define their source rock, paleo-weathering, pollution impact and provenance of the sources. The studied black shales are highly fossiliferous and fissile. They are texturally classified as phosphatic marly mudstone microfacies. The black shale mineral composition is mainly composed of calcite, apatite, quartz, pyrite and clay minerals. The average values of Cu, Ni, Zn, Cr, V, As and Se and the ratios Rb/Sr and Cr/Ni in black shale are enriched compared to those of the Post-Archean Australian Shale (PAAS) values. Electrical properties of samples were measured using a non-polarizing electrode, at room temperature (∼18°C), and relative atmospheric humidity of (∼35%), in the frequency range from 42 Hz to 5 MHz. The changes in electrical properties were argued to be due to the change in mineral composition. Generally, the electrical properties of rocks are changed due to many factors such as grain size, mineral composition, grain shape and inter-granular relations between grains. The dielectric constant decreases with frequency, and increases with conductor concentration. Also, the conductivity increases with the increase of conductor continuous paths between electrodes.

Application of imaging logging in reservoir geological research

With the ability to provide complete profiles of pseudocolor image formation, IL (imaging logging) measures directionally, thereby offering a possible alternative to drilling and coring. This paper, relying mainly on IL information but also referring to formation dip angle logging information, details sandstone lamina dips and identifies sedimentary body dips, and sums up a practical palaeo-provenance direction judgment method using heavy mineral data analysis. By identifying a fine sandstone reservoir through an IL lithological model, a bedding model and a rhyme model, a 1D pseudoresistivity curve (named the 'IL rhythm curve') is, according to IL image analysis, extracted to assist in the interpretation of sedimentary microfacies and to establish an IL single-well facies analysis profile, overcoming an observance difficulty of IL in silty sandstone regions and intuitively displaying whole-horizon sedimentary evolution. As for a glutenite formation, calibrating IL information by rock cores, a single-well facies sequence of IL is established by identifying the Bouma sequence, high-density turbidity succession, the middle fan braided channel, the outer fan mudstone and other microfacies sequences, finely dividing the sedimentary facies sequence about sedimentary stage.

Microfacies and environmental study of the lower cretaceous yamama formation in Ratawi field

The Yamama Formation is the main Lower Cretaceous (late Berriasian–Valangenian) carbonate reservoir in southern Iraq. Petrographic study from thin-section examination shows that the skeletal grains included calcareous algae from both red and green algae. Red algae is concentrated in the upper part of the Formation, and the most important of this algae species is Permocalculus ssp. Green algae is less common, and its concentration is in the middle part of the Formation. The most species found in the Yamama Formation is dasycladeans, and both small and large species of benthonic foraminifera such as Nautiloculina, Textularia, Trocholina, Pseudocyclammina, and Everticyclammina are also present. The non-skeleton grains included oolites, pellets, and micrite. Six cyclic type microfacies have been recognized for Yamama Formation in Ratawi-3 (Rt-3) and Ratawi-4 (Rt-4) Wells, namely peloidal packstone–grainstone, algal wackestone–packstone, oolitic–peloidal grainstone, bioclastic wackestone–packstone, foraminiferal wackestone, and mudstone microfacies. The latter has been divided into two submicrofacies: argillaceous lime mudstone and fossiliferous lime mudstone. The lateral extension of these microfacies has been identified by integrating the thin-section data and well logs’ character variations with similar characteristic for microfacies. The Yamama Formation was affected by five diagenetic processes, which are micritization, cementation, recrystallization, silicification, and stylolites. The Yamama Formation was deposited during a regressive period within the outer ramp, shoal, and inner ramp setting.

Geotechnical Behavior of Pliocene Sedimentary Rocks Exposed along Qena-Safaga Road at Qena region, Egypt

Geotechnical properties of Pliocene sedimentary rocks (Durri Formation) exposed along Qena-Safaga road were investigated to evaluate their geotechnical behaviour. The purpose of this research was to interpret a real reason of cracks occurring in the asphalt layer and in the area around the road and to suggest the suitable treatment of theses cracks. Durri Formation lies under the asphalt layer as sub-grade and exposed along the road at the study area. Mineralogical analysis of the studied samples showed that the Pliocene sedimentary rocks were mainly composed of calcite and clay minerals. Petrographical investigation showed that the studied Pliocene sedimentary rocks of Durri Formation at the studied area were mainly composed of five sedimentary microfacieses including mudstone, marlstone, marly, dolomitic and detrital limestone. Unconfined compressive strength of the studied sedimentary microfacieses was ranging from 155.92 to 291.92kg/cm<SUP>2</SUP>. Mudstone and detrital limestone microfacieses had the lowest values (155.92 to 197.50kg/cm<SUP>2</SUP>); in contrast, marlstone, marly limestone and dolomitic limestone microfacieses had the highest values (218.29 to 291.92kg/cm<SUP>2</SUP>). Swelling pressure value of the mudstone microfacies was 6.50kg/cm<SUP>2</SUP> and the swelling pressure of the marly limestone microfacieses was ranging from 0.44 to 2.10kg/cm<SUP>2</SUP>. Marlstone microfacies had the highest swelling pressure value (16.00kg/cm<SUP>2</SUP>). In contrast, dolomitic and detrital limestone microfacieses had not swelling pressure. Retained percent of the slaking durability test of the studied sedimentary microfacieses was ranging from 88.70 to 94.60% having medium to high durability according to slake durability classification of Gamble, except one high expansive marlstone microfacies had low retained percent (58.00%) and was described as low durability microfacies. Expansive sedimentary rock microfacieses of Durri Formation including mudstone, marlstone and marly limestone microfacieses which represent the sub-grade of the road were swollen due to water coming from the damaged old water pipe that runs parallel to the road and that led to a heave of both the road and the damaged old water pipe. The heave of the old water pipe led to an increase of the damage and the amount of the water coming from this pipe. In addition, drying the saturated Pliocene sedimentary microfacieses due to solar radiation led to a formation of large scale mud cracks having triple junction, polygonal and randomly oriented forms. These cracks occurs on the asphalt layer and in the area around the road at the study area. Grouting of the cracks using cement and chemical stabilization of the expansive sub-grade sedimentary microfacies utilizing lime were suggested to treat these cracks and to reduce the swelling pressure respectively. In addition, monitoring system of the cracks using total station was suggested to evaluate the displacement of these cracks and to determine the relationship between cracks origin and recent tectonic movement at the study area.

Petrography and paleoecology of carbonate- phosphatic rocks of Ratga formation (Damlouk member) Akashat Area, western desert of Iraq

This research covers the detail petrographic study of the rocks of Damlouk member, which represented the middle part of Ratga formation (Eocene) of Akashat area in the western desert of Iraq. This study including the knowldgment of the lithologic and microfacies aspects of this member and also the determination of environmental deposition for each of these microfacies obtained from petrographic analysis. From the field observations and study the rocks in thin sections under the microscope,it is clear that the studied member consist generally of about 40 meter of carbonat_dominated sequence_Rocks types are chalky,marly limestone,fossiliferous limestone with ocasional phosphatic horizons.Detailed petrographic examination of these rocks show that they are characterized by nine distinctive microfacies which include: 1 - L ime mudstone microfacies. 2 - S helly lime wackstone packstone microfacies. 3-Nummulitic lime packstone microfacies . 4-Nummulitic lime packstone to grainstone microfacies . 5-Shelly nummulitic lime packstone microfacies . 6-Foraminiferal lime wackstone microfacies. 7-Oyster_shelly lime packstone microfacies. 8-Bioclastic lime packstone microfacies. 9-a-Phosphatic lime wackstone microfacies . 9-b-Phosphatic wackstone and packstone microfacies . 9-c-Shelly phosphatic lime packstone microfacies.

Facies Analysis and Depositional Environments of the Euphrates Formation Between Fuhaimi and Al-Qaim Valleys, in Western Desert-Iraq

The study involves the Euphrates Formation in the area between Fuhaimi and Al-Qaim valleys in the western desert of Iraq. The Formation was divided into six informal units depending on various lithological properties. Facies analysis reveals the presence of the following microfacies, from bottom to top respectively; pelletal lime packstone, pellitoidal lime grainstone, oolitic lime grainstone, benthonic lime packstone and dolomitized lime mudstone microfacies. These microfacies, in addition to some geochemical properties were used to interpret the depositional environments, which are ranging from shelf, low water energy restricted and lagoonal environment to relatively high water energy open marine.