Investigation of Interfacial Processes Between Oil and Well Stimulation Fluids Under Different Contact Condition

One of the practical challenges in the oil and gas industry is the formation of acid-oil emulsions and asphaltene sludge when well stimulation fluids come into contact with oil. The key to solving these problems lies in understanding the processes at the interface between oil and these agents, which is the focus of this study. The research investigates the processes occurring between sensitive oil and two types of stimulation fluids based on hydrochloric acid and ethylenediaminetetraacetic acid (EDTA) with and without the addition of a surfactant. Three methods are employed: simple mixing («bottle test»), simultaneous flow of fluids in a capillary, and simultaneous flow of fluids in a micromodel simulating a porous medium. Using simple mixing, it is shown that adding a surfactant to 15% hydrochloric acid can prevent sludge formation but does not prevent emulsion formation. Additionally, it is found that EDTA-based compositions with a neutral pH are compatible even with sensitive oil. Simultaneous flow experiments demonstrate the role of capillary walls in creating sludge and the cleaning ability of the chelating agent. Simultaneous flow in the micromodel highlights the distinctive features of hydrochloric acid compared to the chelate discrete flow, emulsion formation in the near-wall layer, and precipitate formation on pore walls. The results of this study can be useful both for further fundamental research into colloidal-chemical processes in oil reservoirs and for practical applications.