By displacing oil in porous media with other fluid, different mechanisms of fluid displacing occur. The importance of understanding the trapping mechanisms like pore body filling is irrefutable. Pore body filling mechanism with a coordination number of four has different events like I-0, I-1, I-2 and I-3. Previous studies showed that the event of I-0 occurs when the pore is only filled by a compressible non-wetting phase, but this study showed that this event could also occur by an incompressible non-wetting phase. Trapping mechanisms can be examined in a glass micro-model. In this research, a glass micro-model with three different patterns was used. Results showed that at two spots of the micro-model, the mechanism of the pore body filling (PBF) for the I-0 event could be occurred by an incompressible non-wetting phase. The occurrence of the I-0 event was performed after the events: corner film flow of wetting phase from one of the four-junction of the pore, then swelling wetting phase at the throat and at last snapping-of non-wetting phase at pore centre. By using this new mechanism, one can achieve more accurate simulation and modelling of fluid flow through porous media. This issue is necessary for pore network modelling of oil-wet fractured reservoirs. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.