Precipitation of Barium Sulphate during the Waterflooding Process in Polish Offshore Oilfields—Case Analysis

The fundamentals of scaling during waterflooding of an oilfield are presented. Mineral precipitation is described using both the kinetics approach, with the corresponding equations given, and the thermodynamic models’ theoretical foundation discussed—mainly specific ion interaction and Pitzer models. This paper focuses on the process of mixing incompatible waters during both water injection and production from an oilfield, as this was identified as a primary reason for barium sulphate precipitation. Two methods of minimizing the risk of solid phase deposition during the mixing of water using the addition of inhibitors and removal of sulfur compounds through a membrane system before water injection into the bed are shown. In addition, formation damage to the near-well zone is discussed with its implications for field operators. Using thermodynamics, especially equations based on the HKF-SRK modified model, this paper describes typical conditions for barium sulphate precipitation during hydrocarbon production on a Polish offshore oilfield. The case study is presented using scaling tendency (ST) and solid concentration values to distinguish the most vulnerable places of solid deposition, both topside and subsurface. The importance of avoiding the mixing of incompatible waters is documented and shown in comparison to a non-mixing scenario.