DFT-MD dissolution of oilfield pyrite scale using borax

Abstract

Introduction: Oilfield scales including pyrite form in oil and gas pipelines, underground tubing, and surface equipment thus blocking the flow of fluids and hindering production. Hence, the need for the development of effective chemicals in scale dissolution and removal. Materials and Methods: A computational technique known as Density Functional Theory-Molecular dynamics (DFT-MD) was employed to investigate the use of borax in scale dissolution. This method aids the understanding at the atomic level of scale dissolution by using Quantum ATK's virtual Nano lab and VASP for model building and DFT-MD calculations respectively. Geometrical studies and radial distribution functions were carried out for data analysis. Results: The results show that potassium ion preferentially bonds to the sulfur atoms in the top layer of the pyrite surface rather than with iron. Hence, becoming the predominant factor that is responsible for pyrite dissolution. The K-S bonds evolve dynamically and expose the rest of the pyrite surface. Conclusions/Future Directions: The presence of a chelating agent alongside borax would prevent Fe-S bond formation. Hence, it is proposed that borax, in conjunction with chelating agents, would be efficient in pyrite scale dissolution and removal. This technique can be used to study other iron sulfide scales such as troilite and greigite which have different iron to sulfur ratio compared to pyrite. This will consequently help boost production in the upstream sector.