The synthesis of trimeric comb-type nonionic surfactants and their application in microemulsion flushing fluid

In order to effectively remove the oil-based drilling that remains on the wall of a well and improve the quality of well cementation, flushing fluid must be used to clean it. Due to its excellent flushing effect, microemulsion flushing fluid has been a hot area of research in recent years; the application, however, is limited because of its poor resistance to temperature. In this paper, for the purpose of enhancing the temperature resistance of microemulsion flushing fluid, a new type of comb-shaped trimeric nonionic surfactants N,N-bis(2-stearamidoethyl) stearamide was synthesized, and an anionic–nonionic surfactants composite oil-in-water microemulsion flushing fluid (ANC-MEFF in short) to flush the oil-based drilling was formed. Studies have shown that it has a good flushing effect on oil-based drilling between 20 and 160°C, and its flushing efficiency can reach 93% or even higher. Compared with the CW210L organic phosphorus flushing fluid (Number 1 in short), the flushing efficiency increased by about 20?~?40%, while the microemulsion flushing fluid formed by OP-10 (Number 2 in short) increased by 30% in high temperature, with the application temperature ranging from 20?~?60 to 20?~?160°C, respectively. Additionally, it was found that the microemulsion flushing fluid can make the borehole wall and casing wall change from “oil-wet” into “water-wet”, which is conducive to promoting the quality of cementation between the first and second interfaces intuitively.