Chemical and biological compatibility of different injection waters with Zubair Formation Water of Upper Sand Member in Zubair Oil Field, South of Iraq

Water injection by water flooding was used to enhance and increase oil production in Zubair oil field, southern Iraq. Physical-chemical and biological analysis of five water samples from different sources were collected to evaluate its compatibility with formation water using biological experiments and chemical compatibility simulation. The results show that injection water is classified weakly acidic-weakly alkaline and saline water, whereas surface water samples are considered weakly acid-weakly alkaline. The total dissolved solids results show brackish types accept for Formation water which classified weakly acid and Brine water. All the studied water samples contain bacteria colonies of Escherichia coli and Coliform expect for one sample, while Sulfate Reducing Bacteria was founded in all studied samples. Mathematical model of chemical compatibility between studied water samples and Zubair Formation water of the scale prediction model show that there are no needs for any inhibition treatments of all scales except for Geothite and Dolomite that should be treated before water injection. The biological compatibility experiments results show Formation damage about (61%) and (69%) in the studied core samples, while Bactria in water injection caused formation damage about (20%) and (51%).