Liquid foamers have gained their popularity in deliquifying aged natural gas wells and coal bed methane wells due to their cost effectiveness and ease of application. Foamers are usually combinational products with Corrosion Inhibitors (CIs) and Scale Inhibitors (SIs) included to provide additional benefits such as corrosion protection and addressing the scaling issues in these applications. Organic solvents are often used to improve secondary properties such as pour point, viscosity and/or pumpablity of the foamer formulations. Designing an effective multi-functional foamer is more an art than science in production chemicals for the oil and gas industry. In this paper, Design of Experiments (DOE) methods were utilized to investigate synergism and antagonism in foamer formulations containing different surfactants, CI and Ethylene Glycol Monobutyl Ether (EGMBE) as the winterization solvent. Correlations between formulation compositions and performances such as liquid unloading efficiency, corrosion protection, pour point and cost effectiveness were studied. Models were developed based on these correlations and validated for performance prediction. In addition, the synergism observed in liquid unloading performance of formulations containing binary surfactants mixture was probed by studying the Critical Micelle Concentration (CMC) and molecular interaction in aqueous solutions. The composition of mixed micelles and the interaction parameter beta obtained using Rubingh's theory, were also discussed. (C) 2012 Elsevier Ltd. All rights reserved.