This paper presents a study for enlarging the oil droplets by using the polyvinylidene fluoride (PVDF) membranes in a cross-flow membrane filtration system at the transmembrane pressures range between 0 and 4 bars. The PVDF membranes are fabricated by using phase inversion technique with different concentrations of coagulant ethanol (0 – 30 v/v%). Alkaline-surfactant-polymer (ASP) produced water is synthesised and tested as the feed solution with the oil droplets sized between 0.1 and 0.2 μm. Results show that the effect of the membrane formulations on the oil droplet coalescence is lesser as compared to the effect of the transmembrane pressures. More than 65% of the coalesced oil droplets in permeate having the diameters exceeding 1.0 μm although at least 50% of the membrane pores are larger than the oil droplets in the feed solutions. It is suggested that the tortuous structure of the membranes coalesced the oil droplets significantly.