Evaluation of Using Coagulants for Treatment of Highly Viscous Slop Water Containing Xanthan Gum

Abstract

Exploration and development drilling activities in offshore Oil and Gas industry generates waste streams, which slop water are among the significant wastes. Slop water is formed when wastewater originating from multiple sources becomes contaminated with oil/synthetic-based drilling fluid components and have to be treated or disposed prior to discharge due to the strict regulations in Norwegian Continental Shelf, NSC. The slop water is collected in tanks where it is contaminated with different components which cause varying composition. The different contaminants are mainly in the from Oil-in-Water (O/W) emulsions, which may cause problem in to stay in compliance with discharge limits, 30 mg oil per liter of water. In some instance the varying slop can be more complex to treat, one such instance is high viscous slop water. The cause of high viscous slop has been identified as slop containing Xanthan Gum (XG). The main focus of this study is on evaluating treatment methods for complex slop water containing XG. The understanding of polymers applied offshore for different purpose has been important for the performance of this study. Furthermore, analysis of possible slop water treatment technologies and combination of them used offshore and onshore is carried out in this study.

A major research based on literature study is presented in this thesis to support the experimental study. In the experimental part chemical treatment combined with centrifugation is evaluated as a representative for high viscous slop water. The results of the experimental part showed that Nature NIC and Nature NSC coagulants combined with centrifugation were an alternative for treatment of high viscous slop and increased the quantity of water recovered. Dilution of XG (aq) with slop or seawater had a significant effect on the viscosity of XG (aq), in addition to increased separation of water from XG (aq) which was obtained. Increased addition of NaOH increased the separation of water from XG (aq).

Dilution of XG (aq) with 75 % seawater combined with 2.0 ml/L of NaOH and 4.0 ml/ L coagulants and centrifuged were chosen as potential solution for the high viscosity of slop water, 116.40 g of water was separated from XG (aq) and sample dried in oven showed 96.5 % water hold by XG floc.