The injection of hot oil to clean the formation and tubing of accumulated paraffin has been used for many years in petroleum production. Although effective in freeing tubulars immobilized by paraffin deposits, formation damage has been attributed to hot oiling when the oil reaching the formation face is at a temperature below the paraffin cloud point. The differential equations describing hot oil injection through the casing-tubing annulus were solved using finite difference mathematics and the model was verified using data from field studies. Model studies indicated that rapid cooling of the injected fluid frequently results in fluid temperatures below geothermal in the lower reaches of wells of even moderate depth. Injection through centralized tubing provides a conduit for effective transmission of thermal energy along the entire depth of the tubing and to the formation face. Injection through tubing is modeled and verified by field experiment. A parametric study of operating parameters is included.

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