The influence factors of NMR logging porosity in complex fluid reservoir

Porosity is a basic parameter for evaluating reservoir, and NMR logging is an effective method to obtain the porosity. However, we have often found that there exist significant differences between NMR porosities and formation core porosities in the complex reservoir. In this paper, we list the factors which affect the NMR porosity response in the complex reservoir, such as longitudinal relaxation time (T 1), transverse relaxation time (T 2), hydrogen index (HI) and borehole environment. We show how these factors affect the NMR porosity response and suggest methods to correct them. This should improve the accuracy of NMR logging porosity in complex reservoirs for the terrestrial formation.