Research on Oil-Based Drilling Fluids Emulsion Droplet by Low-Field NMR

In this paper, low-field nuclear magnetic resonance (NMR) was used to research the stability of water-in-oil emulsion droplet in oil-based drilling fluids. First, the transverse relaxation time T2 of white oil and pure water are obtained by the CMPG pulse sequence, and then, a further qualitative analysis about the T2 distribution curve of water-in-oil emulsion is conducted by introducing the relaxation reagent MnCl2·4H2O; the relaxation peak which located in between 10 and 1000 ms is corresponding to the overlapping peaks of moderate-movable free water and white oil, which is defined as emulsion relaxation peak; the relaxation peak which located at between 1000 and 10,000 ms is corresponding to the high-degree-movable free water. Thus, in this paper, we choose the relaxation peak area ratio and relaxation peak spacing as quantitative indicators to study the influences of relaxation reagent, oil-to-water ratio and aging temperature on the transverse relaxation time T2 distribution curve of emulsion. In addition, low-field NMR was also used to test the relative oil content in oil-based drilling fluids emulsion. The results shows that the low-field NMR is an efficient, fast, and accurate analysis and test technology to reflect the stability of oil-based drilling fluids emulsion droplet, while at the same time, it can also be used to test the relative oil content in oil-based drilling fluids emulsion or crude oil efficiently and accurately.