Ab Initio molecular dynamics of the dissolution of oilfield pyrite scale using borax

Abstract

Iron sulfide scales, particularly pyrite, form in oil and gas underground tubing and surface equipment thus blocking the flow of fluids and halting production. Therefore, the development of physicochemical processes for scale removal is of pivotal relevance. In this work, Ab Initio Molecular dynamics simulations have been employed to investigate the use of borax as a scale removal agent and understand the molecular level features in the dissolution of pyrite using a borax solution. Geometry analysis, radial distribution function, and near neighbor analysis tools have been used to analyze the data. The reported results show that potassium ion is preferentially bonding with the sulfur atoms in the top layer of the pyrite surface rather than with iron, thus being the predominant factor that accounts for pyrite dissolution. The K[sbnd]S bonds evolve dynamically exposing the whole pyrite surface. The presence of the chelating agent would prevent the formation of Fe[sbnd]S bonds. It is proposed that borax, in conjunction with chelating agents, could be used for removing the pyrite scale and consequently boosting production in the upstream sector.