Abstract: The principle of evaluation of formation pore structure with NMR logs is presented. The effect of hydrocarbon-bearing reservoir on distribution shape of t2 in NMR logs is discussed. It is suggested that its applied conditions and suitable scope should be paid attention to. In some conditions, such a distribution shape of t2 in NMR logs should be corrected into that in state of 100% water saturation, followed by using the method of percentage of three-porosity composition to evaluate the formation pore structure, the results will be more reasonable.

Key words: NMR, well log, pore structure, evaluation