Physico-chemical Characterization and Salinity Distribution of the Oilfield Water in the Upper Member of Zubair Sandstones in Rumaila North Oilfield, Southern Iraq
Publish Year: 1397
نوع سند: مقاله ژورنالی
زبان: English
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شناسه ملی سند علمی:
JR_IJOGST-7-1_002
تاریخ نمایه سازی: 18 اسفند 1397
Abstract:
The oilfield water in the upper member of Zubair reservoir (Barriemian-Hauterivian) in Rumaila North oil field is investigated for the interpretation of salinity and geochemical evolution of brine compositions. The interaction of the oilfield water with reservoir rocks resulted in a brine water, which is derived from the marine water and is partially mixed with meteoric water; the composition of the water is similar to that of formation water from the offshore/onshore Mesozoic reservoirs of the Gulf of Mexico. The high average of total dissolved solid (TDS) (215625 mg/l) is consistent with the average electrical conductivity (351024 μs), and is predominantly represented by Cl (123679 mg/l), Na (29200 mg/l), and Ca (14674 mg/l). The main contributing cations (epm%) are Na (70.2), Ca (18.9), Mg (8.1), and K (1.7). The main anions include Cl (99.7), SO4 (0.25), HCO3 (0.07), and CO3 (0.005). The sodium content is six times greater than that of seawater; calcium and magnesium contents are three times greater, and chloride is 6.5 times greater. The sulfate is depleted to one sixth, due to a sulfur release from sulfates into the hydrocarbon phase. Zubair oilfield water is characterized by an acidic pH (pH=5.2- 5.77), high specific gravity (1.228), high fluid pressure (4866 psi), hydrocarbon saturation of 43%, water saturation of 57%, and porosity of 12.7%. The mineral saturation model indicates that Zubair oilfield water is unsaturated water with respect to all the suggested minerals at a pH of 5.45, but at a simulated pH of 9.12, brucite is at equilibrium; brucite and portlandite are supersaturated at a pH of 11.9. The mineral solubility responses to the changes in temperature, pressure, pH, oxidation potential (Eh), and ionic strength, thereby proportionally developing formation damages.
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Authors
Salih Muhammad Awadh
Professor, Department of Geology, College of Science, University of Baghdad, Baghdad, Iraq