Important differences arise when chemical demulsification strategies are implemented for heavy crude oils (°API ∼ 10). Traditional methods for screening and selecting an appropriate demulsifier based on bottle tests and lipophilic–hydrophilic parameters (i.e., HLB, RSN, and so on) tend to be less adequate because of the almost negligible density difference between the oil and the water phases. This situation leads to a detriment of the separated water often mixed with undesired dense-packed layers (DPLs) and emulsion layers. In this work, dehydration of heavy crude oil emulsions from a Colombian oilfield was assessed through the use of a wide range of chemical demulsifiers of different functionalities. Through the use of bottle tests and transmission/backscattering measurements, it was shown that the demulsification mechanisms involved in these limiting cases (low density difference) are different. Hence demulsifiers with functional groups that have traditionally performed very well for lighter oils fail when applied to the heavy crude oil cases. Poly­(ethylene oxide)/poly­(propylene oxide) block copolymer-based products (PEO/PPO) do not seem to have the ability to penetrate the asphaltene network/film at the liquid–liquid interface (separated water, <17%) while the alkylphenol-aldehyde resins seem to prevent the formation of DPLs/emulsion layers possibly through polar interactions, yielding a good quality water phase after separation.