Tool for Predicting Wax Deposition Rate at Different Operating Conditions: A Penetration Theory Approach

Solid crystals may deposit when the thermodynamic conditions of the temperature, pressure or composition changes in the process of oil production. This crystalline solid (wax) may block the pores in the formation and significantly affect the oil productivity. Several studies have been conducted on the mechanism of wax deposition in and around the wellbore. Experimental measurements have shown that most of these previous analytical models under-estimate elemental Wax build up rate at different radial distance around the wellbore while the minimum blockage time was over-estimated. This paper presented an improved analytical model for predicting the rate of deposition of wax inside a wellbore or pipeline from a crude oil at different operating temperatures, which also allows the selection of the temperature with minimum deposition rate as system or operating temperature, by assuming an equimolecular counter-diffusion condition at the interface between the solute (solid phase) and the solvent (liquid phase), this is known as Penetration theory. Using a Penetration theory to predict wax deposition rate will be a new dimension in wax deposition modelling, since most of the researchers depend solely on using steady state Fick-s first law of molecular diffusion, chain-s rule and thermodynamic models for their predictions whereas Penetration theory is based on using circulating or eddy currents present in a turbulent fluid (eddies diffusion), combining with unsteady state Fick-s second law, without the inclusion of chain rule