The determination of interfacial energy (hence interfacial tension) from the shapes of mobile interfaces in cylindrical tubes is a rather viable though seldom utilized method despite the relative ease of its implementation. In this work, neutron imaging is used to reveal the shapes of interfaces in the system of perdeuterated p-xylene (p-C8D10) layered over water (10.88 mol.% of H2O in D2O) and exposed to pressurized methane (CH4, from 1.0 to 101 bar) at 7.0 to 30.0 ℃ while enclosed in the titanium tubular cell. These non-tactile measurements are performed using relatively high spatial resolution (pixel size 20.3 μm). The sensitivity limits determining the uncertainty of thus derived interfacial tensions are analyzed. Interfacial tension for methane – p-xylene was determined at the experimental uncertainty of 2 mN⋅m−1. Interfacial tension for p-xylene – water was estimated at the experimental uncertainty of 16 mN.m−1. Water and p-xylene are severe formers of freeze-out from moist and/or hydrocarbons containing natural gas. We survey the conditions needed for the interfacial tension measurements of industrially very relevant systems with prospects of acceptable experimental uncertainties while utilizing the intrinsically straightforward and on the first principles based methodology.