Hypothesis: Determining capillary pressures and permeation resistances of multiphase seepage in porous-type reservoirs is crucial. The dynamic contact angle (CA) is one of the critical parameters used to calculate capillary pressures and permeation resistances. Under reservoir conditions, dynamic CAs are rate-independent of the triple-phase contact line velocity. Calculating rate-independent dynamic CAs remains challenging and is the main focus of this paper. Experiments: An experimental system was designed to capture the dynamic CAs of liquid-fluid displacements in microscale polydimethylsiloxane (PDMS) microchannels. These microchannels were 20 x 80 mu m or 20 x 40 mu M in height and width. The capillary numbers (Ca) were controlled to satisfy the conditions of Ca < 4 x 10(-5) for liquid-air displacements and Ca < 3.5 x 10(-7) for liquid-liquid displacements. Findings: Since pinning forces were consistent at the receding interface and the advancing interface, energy barriers exhibited symmetry. However, CA hysteresis exhibited asymmetry. Based on our experiments, a linear regime of hysteresis was developed and verified to be consistent with others' experiments. The relation can be used to calculate hysteresis strengths and rate-independent CAs. This model was also compared with the fractal model. The hysteresis factor in this model can be derived using the Wenzel factor r and the Cassie fraction phi(s). (C) 2019 Elsevier Inc. All rights reserved.