NMR Fluid Typing

This article is about the principles of NMR fluid typing referring to 1Dand 2D-NMR Laplace Invers Transform of the magnetization decay. NMR logs can provide useful information about the fluids located within the invaded zone of the near-wellbore volume, normally between one and five inches depth of investigation. The range of fluids that can be detected by NMR logs depends on the fact that the magnetization decay is sampled at the inter-echo time (TE) using magnetic field gradients (G’s). Under these measuring conditions, at nearly simultaneous field gradients, it is possible to calculate the diffusion constant which is a key variable for fluid typing, especially when the main interest is water and oil identification. In the case of gas detection, there is another powerful technique that takes advantage of the high diffusion constant of gas: it is the ratio R between T1 and T2app, where T2app stands for the T2 measured under magnetic field gradient conditions. The ratio R of gas can be up to two orders of magnitude higher than oil or water. The higher the so-called GTE factor the higher R.