Diagenesis and reservoir quality analysis in the Lower Cretaceous Qishn sandstones from Masila oilfields in the Sayun–Masila Basin,eastern Yemen

Lower Cretaceous sandstones of the Qishn Formation have been studied by integrating sedimentological, petrological and petrophysical analyses from wells in the Masila oilfields of eastern Yemen. These analyses were used to define the origin, type of diagenesis and its relation to reservoir quality. The sandstones of the Qishn Formation are predominately quartz arenite to subarkose arenite with sublitharenite and quartz wackes displaying a range of porosities, averaging 22.33%. Permeability is likewise variable with an average of 2844.2 mD. Cementation coupled with compaction had an important effect on porosity destruction after sedimentation and burial. The widespread occurrence of early calcite cement suggests that the sandstones of the Qishn Formation lost significant primary porosity at an early stage of its diagenetic history. In addition to poikilotopic calcite, several different cements including kaolinite, illite, chlorite and minor illite–smectite occur as pore‐filling and pore‐lining cements, which were either accompanied by or followed the development of the early calcite cement. Secondary porosity development occurred due to partial to complete dissolution of early calcite cements and feldspar grains. The new data presented in this paper suggest the reservoir quality of Qishn sandstones is strongly linked to their diagenetic history; hence, the reservoir quality is reduced by clay minerals, calcite and silica cements but is enhanced by the dissolution of the unstable grains, in addition to partial or complete dissolution of calcite cements and unstable grains. Copyright © 2015 John Wiley & Sons, Ltd.     

Engineering-geological and geotechnical investigation for risk assessment

Before construction activities could begin, engineering geological and geotechnical investigations had to be approved in order to establish a map with suitable areas for safe construction. The example used in this study is Tunis City which has complex geology and geomorphology. The risk analysis was based on a large-scale land-suitability map that was prepared using Geographic Information Systems (GIS). The approach used in this study combined physical data with the geotechnical properties of Tunis City. The adopted methodology and analyses were performed to assess the risk of urban expansion and landscape management. Results are presented as a zoning map that shows the suitable area for safe extension of the urban area. The data used and multi-criterion analysis of geotechnical and geological data seems to be useful for similar case studies and the adopted methodology can be used successfully for identifying similar cities for risk assessment.     

The prolate Bok globules evidence for the existence of dark matter sub-halo

Although the existence of dark matter is generally accepted by the mainstream scientific community, there is no generally agreed direct detection of it. Also, observations show that some Bok globules are prolate in some regions without suitable explanation for its cause. In this paper, we investigate the effect of dark matter sub-halo in transformation of the Bok globules from spherical to the prolate shape. We limit the investigation to a particular case that the magnetic field and turbulent effects are negligible through the Bok globule. We consider the gravitational effect of dark matter sub-halo on the isothermal Bok globule that is exposed to suitable distance of it. The results show that the dark matter sub-halo can justify the transformation of Bok globules in some regions. In this paper, we introduce a new method for proving the existence of dark matter sub halo.     

United Arab Emirates limestones: impact of petrography on thermal behavior

The thermal behavior of selected limestones from representative localities of the United Arab Emirates is investigated for their suitability for soft-burnt lime production. The limestone samples were collected from the Ghalilah, Musandam, Shauiba, Muthaymimah, Dammam and Asmari formations. The samples were characterized for petrography, mineral and chemical composition, together with physico-mechanical characteristics. Investigative methods included transmitted light microscopy (TLM), cathodoluminescence (CLM) and scanning electron microscopy (SEM), as well as X-ray micro-tomography (μ-CT), XRD, XRF and Archimedes method. The limestone samples were fired in an electrical muffle furnace for 0.25, 0.5, 1 and 2 hours at 800, 900, 1,000 and 1,100 °C. After firing the lime grains were tested to determine their hydration rate and microfabric. The Ghalilah and Musandam limes show the lowest and highest maximum hydration rates, respectively, due mainly to the impure nature of the former, and the smaller lime crystallites and dominance of post-calcination micro-cracks of the latter. The Dammam and Asmari limes preserve a “ghost” microfabric of the original limestone. Higher allochem contents impose lower activation energy requirements for calcination, which implies earlier calcination of the allochems. The Musandam, Shauiba and Muthaymimah limestones may be useful for the production of reactive soft-burnt lime under the applied firing conditions, however, the Dammam and Asmari limestones need more advanced calcination conditions than the applied ones. The Ghalilah limestone was found to be unsuitable for the production of lime.     

Improved Pile Geometry to Reduce Negative Skin Friction on Single Driven Pile and Pile Groups Subjected to Lateral Loads

Geotechnical and Geological Engineering - Negative skin friction on piles represents a severe problem when piles were installed in soft clay due to consolidation process. It reduces the bearing...     

Mapping Oolitic Iron Ore Deposits in the Ashumaysi Formation,Western Saudi Arabia,Using Different Remote Sensing Techniques Applied to Landsat 7 Enhanced Thematic Mapper Plus Data (ETM+)

Mapping the surficial extent of oolitic iron ore deposits hosted in the Oligo–Miocene sedimentary rocks of the Ashumaysi Formation, western Saudi Arabia, was carried out using Landsat 7 Enhanced Thematic Mapper Plus (ETM+) data. Ore samples were collected from four various locations in the study area, and were studied in the laboratory using the GER 3700 Spectroradiometer (0.4–2.5 µm) and X-ray diffraction (XRD). Principal component analysis (PCA), minimum noise fraction (MNF), and minimum distance classification were used and assessed to map mineralization zones in the study area. Good correspondences were observed between the results obtained from the above mentioned techniques, spectral reflectance analyses, and XRD. The confusion matrix results revealed that mapping of iron ores using MNF is better and more accurate than using PCA. Good matching was also observed between the spectral reflectance curves of the collected samples and the corresponding pixels from Landsat 7 ETM+. The results demonstrated the usefulness of the image processing and interpretation of Landsat 7 ETM+ data for the detection and delineation iron ore deposits in arid and semi-arid areas.     

Synoptic patterns leading to hailstorm in Chaharmahal and Bakhtiari province,Iran

The purpose of this study was to extract the synoptic patterns of 500 mb geopotential height and the sea level pressure leading to form hail in Chaharmahal and Bakhtiari province, Iran. To this end, at first, we explored hail occurrence in different areas of the province under investigation. Then, using sea level pressure and 500 mb geopotential height data, the patterns of hail occurrence were investigated through hierarchical clustering and Ward’s method. The level of 500 mb patterns resulting in hail formation in the area include: (1) settlement of a cut-off low pressure blocking in Turkey and Iran’s position in downstream of trough and injection of humidity coming from the Red Sea; (2) settlement of low ridge in northern Europe and Iran lying in downstream of the trough and injection of humidity of the Mediterranean Sea; (3) settlement of a cut-off low pressure in east of Europe and Iran lying in downstream of the trough; and (4) settlement of a deep trough in the Mediterranean Sea, formation of an omega-shaped blocking in Northern Europe and Iran lying in downstream of the trough. At sea level, the following patterns have caused hail formation in Chaharmahal and Bakhtiari province: (1) settlement of low pressure in Iran and Russia accompanying high pressure in Taklimakan Desert and east of Europe; (2) settlement of low pressure in Iran and high pressure in Egypt, northern Europe, and Taklimakan Desert; and (3) settlement of low pressure in Iran, Saudi Arabia and south of Italy and high pressure in Egypt and Siberia.     

Estimating of water erosion in semiarid regions using RUSLE equation under GIS environment

Water erosion is one of the main forms of land degradation in Algeria, with a serious repercussion on agricultural productivity. The purpose of this study is to estimate the soil loss of Wadi El-Ham watershed in the center of Algeria, this study aims also to evaluate the effectiveness and reliability of the use of the Revised Universal Soil Loss Equation (RUSLE) under a Geographic Information System in this field. The RUSLE model involves the main factors of erosion phenomena, namely, rain aggressiveness, soil erodibility, topographic factor, land cover index and the anti-erosive practices factor. Using this approach, the specific erosion in Wadi El-Ham watershed is estimated as 5.7 (t/ha/yr) in the entire watershed area. This result is compared to the measured suspended sediment at the Rocade-Sud gauging station situated outlet the watershed. These data consist of 1293 instantaneous measures of the water discharge and the suspended sediment concentration recorded during 21 years. Through this comparison, the used approach of RUSLE under GIS estimates the soil loss in Wadi El-Ham in Hodna region of Algeria with an error of 7.5%. Consequently, the results obtained in cartographic format make it possible to target the areas requiring priority action for a larger scale analysis to find appropriate solutions to combat erosion and to protect the natural environment.     

Mineralogy and geochemistry studies on the Nusab El Balgum granitic batches,South Western Desert,Egypt

Igneous rocks of Nusab El Balgum are formed as an elongated complex mass covering an area of about 4 km?×?12.5 km (50 km²), in the NNE-SSW direction of the Tarfawi-Qena-South Sinai trend, which is a branch of the Trans-African shear zone at the intersection with the Kalabsha fault, which is a branch from Guinean-Nubian lineaments. The continuous reactivation of these two major weakness zones from the late Triassic to recent times has created many generations of the magma batches. The exposed granitic rocks of these batches at Nusab El Balgum were represented by the fresh peralkaline granite (youngest) and hydrothermally altered granites (oldest). The fresh peralkaline granite takes the form of a small stock composed essentially of perthites, quartz, sodic pyroxenes, amphiboles (secondary), and rare albite according to the proportion of presence, respectively. The accessory minerals are zircon, bastnaesite-(Ce), columbite-(Fe), magnetite, barite, and sphalerite. The geochemical study indicated that this granite is peralkaline, ferroan, A-type (specifically belongs to the A1-subgroup), anorogeny, emplaced in a within-plate, and crystallized at relatively shallow depth from the alkali basaltic magma similar to the OIBs. Furthermore, it is enriched in the HFSE (e.g., Th, U, Nb, REE, and Zr). The hydrothermally altered granites are formed as an incomplete ring shape and a small stock. They were formed during the late Cretaceous age and were altered due to the hydrothermal solutions from the continuous reactivation affected weakness zones and the new magmatic batches. The hydrothermally altered granites are extremely rich in HFSE found in the accessory minerals such as zircon (different in shape, size, and contains inclusions of bastnaesite and columbite), columbite-(Fe&Mn), rare gittinsite, pyrochlore minerals (ceriopyrochlore and plumbopyrochlore) carlosbarbosaite, changbaiite, bastnaesite-(Ce), monazite-(Ce), stetindite, cerianite-(Ce), thorite, and uranothorite. These rocks were subjected to many highly superimposed hydrothermal alteration types, including propylitic, sericitic, potassic, silicification, argillic, and Fe-Mn oxy-hydroxides. The hydrothermal solutions with low temperatures and containing F^1? and CO₃^2?, PO₄^3? and H₂O caused redistribution; transportation and redeposition of the HFSE in these rocks, in addition to the clay minerals and K-metasomatism, were formed. The relations between the silicification index (SI?=?SiO₂/(SiO₂ + Al₂O₃) and Zr, Nb, Th, U, LREE, and HREE are positive but they become negative with the K-metasomatism.