Arabian Journal of Geosciences最新文献

Geological formations rich in clay tend to undergo expansion upon contact with water-based drilling fluids. The principal mechanism responsible for the disintegration and swelling of these formations is the migration of hydrogen ions into the nano-scale gaps between layers of shale platelets. Effectively mitigating the challenge of clay swelling involves introducing various materials tailored for shale stabilization into water-based drilling mud. In this article, flaxseed mucilage is used as an environmentally friendly drilling fluid additive in a water-based mud system, with the goal of enhancing the rheological, filtration, and hydrophobic characteristics of the water-based mud. The flaxseed extract was added in the mud in four different concentrations (5 mL, 10 mL, 20 mL, and 50 mL). The result of the study reveals that the rheological properties at 38 and 65 degree centigrade after the addition of 10 mL and 20 mL flaxseed extract remained well within the recommended range set by the American Petroleum Institute (API). Both these samples also demonstrated transport index (> 1.5) at both the temperatures. Moreover, the flaxseed extract was also effective in minimizing the fluid loss from the base mud. The 20 mL of flaxseed extract causes only 15 mL of fluid loss from the base mud, which was also three times lower than the base mud. Additionally, the flaxseed extract muds were also tested on the Ranikot shale sample for its stability. According to the immersion test, samples collected from flaxseed mud demonstrated a smooth surface with no cracks and fractures. Furthermore, these immersed shale pellets also revealed high hydrophobic behavior when tested through contact angle measurement. The 20-mL sample showed the highest hydrophobic behavior with contact angle of 56.056 degrees. Besides this, the 20-mL sample also displayed the highest cutting recovery of 70% out of all the samples. In addition, the 20-mL flaxseed sample also showed less shale swelling behavior in linear dynamic swell-meter test. Almost 1.5 times reduction in shale swelling was recorded with the addition of 20 mL flaxseed extract in the base mud. In light of these compelling findings, the study underscores flaxseed’s potential as an eco-friendly and sustainable alternative to traditional clay stabilizers in drilling operations, with the aim of minimizing formation damage.

Microwave treatment is one of the research topics to solve cutting problems of hard rocks such as low cutting rate and high tool wear. Microwave irradiation creates fractures in the rock body and decreases its strength. Numerous studies have been conducted to ascertain how microwaves affect the strength of rocks. Ten carbonate rocks are examined in this paper to see how microwaving affects their strength. First, unconfined compression and tensile strength tests were conducted on unirradiated dry and saturated core specimens. Following that, the two tests were performed again on samples that had been exposed to radiation for varying amounts of time—between 2 and 6 min—at a microwave power of 6 kW. The results showed that the uniaxial compressive strength loss due to microwave irradiation was between 9.0 and 90.0% and 7.3 and 92.0% for the dry and saturated samples, respectively. Tensile strength loss was between 15.6 and 62.7% and 23.2 and 63.1% for the dry and saturated samples, respectively. The efficiency of treating carbonate rocks with microwaves is significantly impacted by density, porosity, and impurities. Multiple regression equations were derived to estimate the strength losses. Concluding remark is that the strength reductions due to microwaves are significant for carbonate rocks.

Soil erosion poses a severe threat to water quality and soil health in semi-arid regions. Assessing soil erosion and sedimentation at the watershed-scale is crucial for managing water resources and soil. In Iran, empirical models, e.g., the erosion potential method (EPM), modified Pacific Southwest Inter-Agency Committee (MPSIAC), and universal soil loss equation (USLE), have drawn more attention than other models, due to the availability of input data and lack of reliable hydrometric station, especially for a long time span. In the present article, we evaluated the soil erosion intensity and sediment yield in the Chehelgazi mountainous watershed (western Iran) utilizing the EPM, MPSIAC, and USLE, combined with the sediment delivery ratio (SDR) module, and then compared them with the observations. The required input data for EPM, MPSIAC, and USLE models all were created in ArcMap 10.8 and ENVI 5.5. The sediment yield amount and soil erosion zonation map were then obtained by the models mentioned and validated by the hydrometric data. According to the results, most portions of the watershed were subject to moderate erosion risk. Moreover, the annual average sediment yield of 196.86, 99.30, and 84.84 kt year⁻¹ assessed by EPM, MPSIAC, and USLE combined with SDR, respectively, suggested the superiority of USLE-SDR and MPSIAC. As compared with the observed amounts of 86.46 kt year ⁻¹, the efficiency of USLE-SDR was astonishing. Overall, we conclude that the USLE model coupled with the Boyce (1975) SDR formula is the best for estimating sediment yield at Chehelgazi mountainous watersheds, while MPSIAC is better suited for mapping soil erosion state.

The geochemistry of Paleogene strata (sandstones and shales) of the N’kapa Formation in part of the western Douala Basin has been studied through major, trace, and rare earth elements (REEs) in order to understand their provenance and tectonic settings. The NF sandstones and shale are clustered around granodiorite with minor contributions from granitic source. The samples show high and fairly constant Th/Sc ratios 0.64–6.9 for sandstone and 1.01–8.7 for shale that strongly indicate provenance from a relatively evolved igneous source (mafic) also different geochemical signatures of Eu/Eu*, La/Sc, La/Co, Th/Sc, Th/Co, Zr/Sc, Cr/V, and Y/Ni ratios, and their plots suggest a mafic igneous provenance with substantial sediment recycling. Geochemical signatures from plots of The La/Th–Hf diagram, La/Sc vs Ti/Zr, and Fe2O3 + MgO vs TiO2 tectonic discrimination diagrams show that the studied rocks were deposited mainly in a passive continental margin setting. The large quantities of alkalis classify the rocks as wackes, Fe-sand, shale, and Fe-shale. The studied lithofacies have been classified based on Al–Fe-Mn enrichment as follows: terrigenous and metalliferous rocks.

An investigation was done to determine the texture, organic matter content, and geochemical characteristics of sediments collected from the continental shelf of the South Western Bay of Bengal. The present study portrays the abundance of sand followed by slightly muddy sand, muddy sand, sandy mud, sandy, and slightly sandy mud in the study area. The mean size of the sediment ranges from 0.40 to 3.57 mm (coarse sand to very fine sand). The sediments are very well to very poorly sorted, coarsely skewed to fine skewed, and platykurtic to very leptokurtic in nature. Trace metals, such as Cu, Co, Fe, Mn, Pb, Zn, Cr, and Ni were analyzed. A relatively high percentage of organic matter is attributed to the predominance of finer sediments entering through the minor and major rivers. The higher trace metal concentration in the study area is closely associated with mud content and Fe is the most abundant trace metal in the study area. Formation of Fe- and Mn-hydroxides in the near-shore regions is responsible for scavenging Pb, Zn, Cu, Ni, and Cr and effectively incorporating them into the inner shelf sediments. Among all the trace metals, the concentration of Co, Pb, Cr, and Ni is found to be higher than the average crustal abundance value marking the role of anthropogenic sources predominantly from industrial, agricultural, scrap metal recycling, sewage, and tourism activities.

The lithofacies and pedogenic features in the Late Oligocene–Early Pleistocene formations provide evidence of changing paleoclimate in the northeastern Sahara region. The strata of the Katkut Formation and the lower Member of the Madamud Formation consist predominantly of coarse and fine-grained siliciclastic lithofacies deposited by braided and sinuous streams that formed under the influence of humid paleoclimate during the Late Oligocene–Late Miocene time. Paleosol horizons with mature calcretes in the overlying upper member of the Madamud Formation suggest increasing aridity by the end of Late Miocene through Pliocene time. This trend of aridification continued during the Early Pleistocene lacustrine deposition of Issawia and Armant formations, as indicated by the predominance of palustrine carbonates displaying different pedogenic features. The climate change may have resulted from the southward movement of Asian monsoons and the uplifts of the Red Sea Mountain chains, as the African continent drifted northeastward. This paleoclimate transition generated variations in basin sedimentation rates that were controlled by base level and tectonics.

Transportation systems support economic activity by facilitating the mobility of people and goods. The main weather-related impact on the transportation industry is flooding, particularly due to heavy rainstorms. Therefore, considering the flooding in Kuwait that occurred in November 2018, this research aims to identify the effect of the floods on the transportation system by estimation and comparison of two models: propensity score matching and difference-in-differences. The impact of flooding has been verified for frequency, time of travel, and car expenses. The results showed that the parameters of the transportation system such as frequency of travel, its duration, and car expenses are significantly affected by the floods in a negative way. Moreover, floods are negatively associated with only two governates, which are Al Asimah Governate and Hawalli Governate. However, flood risk and expectation of flood severity have a significant positive impact on the flood experience. The propensity score matching was more reliable since it describes the data better. Based on experts’ opinion, the design of the roads is the main cause of flooding in Kuwait. It is recommended to construct precast box culvert to prevent floods.

The Pan-African domain of Batouri shows many generations of post-collisional granitoids emplaced between 640 and 500 Ma. They are affected by secondary Riedel faults systems R⁓N084E, R′⁓N016E P⁓N140E and T⁓N060E arranged into en-echelon systems oblique to the prominent Y shear bands directed N091E or to the related C′ or Y⁓N091E. The description and analysis of these brittle-ductile faults are based on classic structural geological methods, including structural surveys, analysis and stereographic projection of mesostructures (planar and linear fabrics) and microscopic observation. The results show two Riedel fault systems with two major bands, C′ and Y, oriented E-W with dextral and sinistral polarities. There are two shortening directions (Z) oriented: NW–SE, which accounts for dextral shear bands, and NE-SW, which develops the sinistral shear bands. The high values of dihedral angles (⁓78°–80°) between the R and R′ faults indicate a compressive tectonic regime of the basement, confirmed by the presence of the B_n and B_n+1 boudins stretching NE-SW and NW–SE. These faults likely interact with the neighbouring and regional scale CCSZ, which control gold mineralization in the Batouri granitoids. The mineralization is hosted by Qz-Fk veins in the R, R′, P and C′ Riedel faults. These mark the late-D₃ phase of deformation, which correlates with the nappes stacking event on the WAC at 600 Ma. The relative chronology of deformation at the regional scale suggests that gold mineralization is controlled by Qz-Fk veins in the R, R′, P and C′ Riedel faults, which correlate with the post-collisional phase of the CAFB around 585–580 Ma.

The challenge in modeling complex-heterogeneous reservoirs is to accurately represent dimensions, trends, and quality for each facies type and to avoid overestimating or underestimating the reservoir elements. NEAG-2 Field has a highly heterogeneous reservoir system of the Albian-Cenomanian age; it is the main reservoir system in the East Abu Gharadig Basin, and it is the main oil contributor in the north Western Desert of Egypt. Therefore, developing a water-tight model for such a complex system can act as an analog for any similar complex-heterogenous system worldwide. In the NEAG-2 Field, a representative reservoir model and dynamic simulation for its reservoir are required to restore the field’s production. The field has an excellent yet unique performance, and it recorded an average production rate of 9000 bbl/d from five producer wells in 2018. Since that peak, production has been declining, with a current total of 1390 bbl/d from four wells. This production behavior was not modeled nor predicted in the previous modeling trials. Therefore, we introduce a mature model to improve production forecasts and optimize recovery while giving an example of how the complex heterogeneous reservoirs should be properly modeled. An object-based geostatistical algorithm was applied in modeling the reservoir facies, and a truncated Gaussian algorithm was applied for the background (non-reservoir) facies. The property models were distributed using Gaussian simulation algorithms, with the guidance of variogram analysis. Three reservoir facies were distinguished, with specific geometry, orientation, and porosity–permeability characteristics to model their flow behavior. The highest-quality facies (type 1) were tidal channels, followed by moderate-quality (type 2) tidal sand bars, which had smaller lateral dimensions compared to the channels. The lowest quality sand facies (type 3) were embodied as mixed tidal flats. Each facies body, reservoir zone, and field segment was modeled distinctly to ensure a representative statistical range for each. The integrated workflow developed a flow-unit-based model that preserved the reservoir heterogeneity and fluid flow complexity, which improved the forecasting for reviving the field production. The final results of this static model were validated by the production data and the history matching of each well.