Research on the Emulsion Stability Mechanism of Water Produced from Unconventional Gas Fields Based on Macroscopic Experiments and Microscopic Molecular Dynamics

In order to improve the treatment of water produced from gas fields, it is necessary to clarify the main reasons for the emulsion stability of the produced water. In this work, 11 factors were selected, including the standing time, salinity, water-phase pH value, foaming agents in the produced water, corrosion inhibitors, defoamers, etc. The turbidity of the emulsion, zeta potential, average droplet size, and oil–water interfacial tension were used as evaluation indicators. The influences of different factors on the emulsion stability of the water produced from gas fields were studied from a macroscopic perspective, and it was identified that the foaming agent, corrosion inhibitor, and salinity were the key controlling factors. Molecular dynamics was used to simulate and study the morphology, relative concentration distribution, interfacial formation energy, and mean square displacement of a water–condensate oil–water system and a condensate oil–foaming agent–water system at each stage of the dynamic process, achieving the microscopic visualization of the oil–water interface and revealing the microscopic mechanisms by which the foaming agent and corrosion inhibitor promote emulsification at the molecular scale. The results show that combining research methods involving macroscopic experiments and microscopic simulations can more comprehensively and deeply clarify the emulsion stability of the water produced from gas fields, providing a scientific basis and technical reference for the design and selection of efficient water treatment agents.