The aim of this study was to evaluate the water quality of Shatt Al-Arab River (SAR) and investigate the influences on the variations of heavy metals levels. The surface water and bed sediments samples at four stations have been collected (4 months) during 2017-2018, and seven heavy metals (Ni 2+ , Cr 3+ , Pb 2+ , As 3+ , Hg 2+ , U 4+ and Cd 2+), as well as 11 parameters including total dissolved solids, the concentration of hydrogen ions, dissolved oxygen, nitrate, chlorides, turbidity, total hardness, electrical conductivity and alkalinity were investigated. The results indicated that the water quality in the SAR depend on the combined effects of natural and anthropogenic factors. The variation of water quality of SAR influenced by the chemical ions inflow from the Tigris River and the marine salt from Arabian Gulf. The highest value of TDS was in S4 it reached to 42,844 mg/l. The results showed that most of the ions increase their concentration by more than 200%, especially in summer season at Fao area due to the effect of the seawater intrusions. In comparison to the sediments, low concentrations and a uniform distribution of most metals were observed in the river water. The river sediments were polluted with heavy metals, while pollution levels in the water were still within permissible limits for drinking, irrigation and aquatic life. These findings indicated that the major sources of river contamination with heavy metals were the atmospheric deposit of gaseous emissions from oil production and electric generators and the surface runoff from agricultural areas after rainfall. Additionally, the tide greatly controls the distribution heavy metals in the river.
The Zubair Formation is a prolific oil reservoir in several southeastern Iraq oil fields. The formation comprises thick sandstones with interbedded shales and siltstones of Lower Cretaceous age (Hauterivian to lower Aptian). The environment of the Zubair Formation consists of fluviodeltaic, deltaic, and marine sandstones. In southern Iraq, the area is subdivided into informal members (oldest to youngest). The Lower Shale, lower sand, middle shale, main pay upper sand, and the upper shale. At the W oilfield, the main pay member is an oil producer. The thickness is of the main reservoir about 100 meters thick. A recent study focused on the Main Pay upper sand, which is divided into three informal units. The upper unit H and lower unit L reservoir units are connected by shale intervals (K unit) that extend throughout the field area laterally. There exist four depositional lithofacies of Zubair Formation fluvial, channel, mouth bar, and prodelta depositional lithofacies. Four Facies were defined according to gamma-ray sandstone, shaly sand, sandy shale, and shale Facies. The Zubair formation has four types of rocks (RRT1, RRT2, RRT3, and RRT4) due to heterogeneity. The RRT1 is characterized by 10%-25% porosities and 10-1000 mD permeability. The RRT2 has a similar porosity range to RRT1, 15%–25%, but an order ofmagnitude lower permeability range from 10-100 mD. RRT3 is considered to have high porosity and low permeability is thought to have great storage but poor flow potential. RRT 3 is characterized by 6%-15% porosities and <10 mD permeability. Meanwhile, RRT4 is considered to have low porosity and low permeability. Various rock types showed in the H unit due to heterogeneity, which composed this unit. The K unit unveiled RRT4 due to shale Facies. The rocks types common of unit L are RRT1 and RRT2 where the L unit mostly ranged from sandstone to shaly sand Facies.
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