Wax deposition during production and transport of paraffinic crude is one of the serious problems faced in downhole and surface operations. Crude oil often contains paraffins which precipitate and adhere to the liner, tubing, sucker rods and surface equipment as the temperature of the producing stream decreases in the normal course of production. Conventional methods of removal of paraffin deposits include chemical dissolution, hot oil/water circulation, mechanical scrapping and pigging. As an alternate to the conventional methods of paraffin removal, wax removal by exothermic chemical reaction also known as thermochemical stimulation is the technique in which the energy liberated from a suitable exothermic reaction is utilized for melting the paraffin deposits and has been shown to be more effective than the conventional treatments in literature.
A major challenge faced while execution of this technique is to control the reaction rate and provide sufficient delay time so that heating can be targeted to the desired depth of paraffin deposits without affecting the integrity of well completion equipment. Towards achieving this goal, this paper describes the key aspects of job design and execution that may significantly enhance the success of exothermic stimulation in wells susceptible to paraffin/organic deposition. The challenges encountered and respective solutions executed are presented through a case study of implementation in 5 onshore wells of western India. The paper also presents a lab validated mathematical model that may be used to predict the behavior of the exothermic formulation and help in optimization and quality control. The job execution procedure including solution preparation, quality testing, pumping, placement and monitoring has been streamlined from field experience to develop a standard operating procedure that may be referred for an effective implementation of this technique.