Mechanism of organic slow-release microemulsified acid for blockage removal

The mechanism of organic slow-release microemulsified acid for blockage removal is not yet completely clear. By using interfacial tension method, lubrication coefficient method drilling cuttings dissolution rate method, and SEM scanning method, the mechanism of organic slow-release microemulsified acid for blockage removal was investigated. The research results show that organic slow-release microemulsified acid can reduce the interfacial tension between itself and the formation fluid to below 20.0 mN/m, thereby enhancing its permeation within the formation. It also reduces the lubrication coefficient of the drilling fluid by more than 40%, further increasing its contact probability with the formation rock. The rock dissolution rate of the organic slow-release microemulsified acid is only 43.8% compared to bare acid, and it proceeds slowly and steadily, allowing it to penetrate deep into the reservoir for blockage removal. Additionally, it reduces the thickness of the hydration film on the rock surface by more than 50% and decreases the contact angle on the drill bit surface from 50.2° to 8.3°, effectively improving the cleanliness of the well and drill bit. After comprehensive analysis, it is believed that the blockage removal mechanism of the organic slow-release microemulsified acid is: the internal acid solution, encapsulated by the oil phase, exhibits a slow-release effect. Under high-temperature and high-pressure conditions in the reservoir, it effectively reduces the interfacial tension between itself and the formation fluid, decreases the hydration film and contact angle on the rock surface, and thereby enhances its permeation within the formation. This ultimately leads to successful blockage removal in deep reservoir.