The Simulation of Paraffin Deposition and Removal in Wellbores

Abstract

ABSTRACT Paraffin deposition creates production problems and formation damage. To eliminate these problems, the deposited paraffin must be removed. Paraffin deposition and removal in reservoirs has been simulated by Ring and Wattenbarger1,2 and paraffin deposition due to natural cooling in reservoirs has been simulated by Peddibhotla.3 The objective of this work is to simulate paraffin deposition and removal in wellbores. The paraffin simulator described in this paper models heat flow in the wellbore, reservoir, underburden, and overburden. This simulator also models mass flow in the wellbore and reservoir. This mass is composed of three pseudocomponents (gas, oil and paraffin) that can exist in three phases (vapor, liquid and solid). Some of this solid paraffin mass deposits onto the tubing during production. This natural phenomena was modeled with the following depositional mechanisms: (1) diffusion deposition and (2) shear deposition. Only one mechanism is used to model paraffin removal, the dissolving of solid paraffin. Paraffin deposition results are presented for a single hypothetical well. These results indicate that only a fraction of the precipitated paraffin deposits onto the tubing. Paraffin removal results are presented for the following three thermal removal techniques: (1) hot oil injection, (2) downhole heaters, and (3) electric tubing heating. These results indicate that hot oil may cause formation damage if the paraffin concentration of the injected oil is high. These results also indicate that downhole heaters and electric heating of the are is a viable thermal removal techniques.