A key step in the enzymatic hydrolysis of semi-crystalline cellulose is the separation and removal of glucose oligomer chains from the surface of the crystalline cellulose.  In this work, we focus on the energetic aspect of this non-reaction factor that plays an important role in determining the overall rate of the cellulose hydrolysis process.  In particular, we use Molecular Dynamics (MD) simulations to investigate the free energy required for the separation of glucose oligomers in presence of water.  Simulations are performed on the non-stacked and stacked arrangement of the cellobiose molecules; these are considered to represent the amorphous and crystalline domains in cellulose. An oscillatory potential of mean force profile was observed in the latter case. The umbrella sampling technique was used to investigate the free energy required for the separation of cellobiose and cellotetrose pairs in water, as well as that required for the separation of glucose oligomers from a long cellulose chain.  Simulation results are used to decipher the dependence of the energetics of the process on the chain length and the interaction between the sugar and water molecules.