Well known use of epoxy-based polymer is to plug a selective layer in completion process. The similar behaviour related to its gelation as a completion fluid is a trigger to ask a question: Is epoxy-based polymer suitable for WSO (water shut-off) application too? Therefore, this paper is aimed to study the applicability of epoxy-based polymer to "reducing excessive produced water treatment" called WSO covering synthesising and core-flood experiment. An epoxy-based polymer is synthesised in various temperature and concentration of reagents those are epoxy and triethylenetetramine which are vary from 6.25% to 50% which diluted in acetone with volume over volume concentration. The polymer is then characterised using Fann-VG to know the rheology and the gelation behavior with respect to the variables above mentioned. A polymer consists of 50% (v/v) epoxy and 50% (v/v) triethylenetetramine is chosen to be applied in core-flood apparatus operating at room temperature, 20 psia injection and 120 psia confining pressure. Sandstone core with various porosity and permeability are tested to reduce its poro-perm due to epoxy-based polymer injection. Variation on concentration has shown that higher concentration gives shorter gelation period. Gelation is defined as a time required to dramatically changing the viscosity profile. These gelation data can be modelled into a simple mathematical model with multivariable consist of concentration and temperature. Sandstone cores undergo a reduction on its porosity over than 54% and permeability upto 100% which means it has potential to resist or even plug a layer with high water cut.