Taking a New Approach Towards Chelating Agents for Scale Removal

Abstract

Scale presents a significant challenge in any context where flow is involved. In the oil and gas sector scale associated problems are notorious because of the significant volumes of brine that are involved at any stage of production. In addition, the formation brines are usually extremely concentrated when it comes to electrolytes that are prone to form scale. The real problematic scales are usually considered to be barite (BaSO4) and pyrite (FeS2, or mixed iron sulfides). The approach to remove them is usually to drive the solubility equilibrium towards solution by simply stabilizing the ions that are involved. That is usually done by coordination of the ions with a ligand that favors binding to the particular cation in question. For pyrite the challenge is then to identify a ligand that strongly coordinates Fe2+ whereas in the case of barite the focus will be on Ba2+. This is the classical approach to mostly target the cation and it has mostly been dealt with in the form of various chelating agents. We show results firstly, where newly designed cation binders provide a 20 % higher dissolving power than the second best and where binding pockets are designed for anions. This new binding mode will enable the design of a structure that simultaneously binds cations and anions and this is where we are heading with the current results. The efficiency of chelating agents is significantly dependent on pH this topic will be touched upon in a computational study here the calculated structure and the associated calculated binding energy will be discussed and related to dissolving power. The result show that ab initio calculations are nice supplements to experimental endeavors.