A Comparative Analysis of Two Methods of Wax Treatment for a Waxy Oil Well in Southwest Trinidad

Abstract

During oil production, when crude oil flows into a wellbore, pressure and temperature are reduced. The micelle structure of the crude oil is destabilized, allowing paraffin (wax) and/or asphaltene molecules to precipitate into the oil, increasing oil viscosity and allowing deposition in the well tubulars. This causes plugging of production and flow lines which decreases oil production. Wax deposition can be mitigated by the application of passive energy waves or a chemical solvent. Passive energy waves are generated by a tool containing a vibrating quartz and semi-precious metal core. This passive vibrational energy stabilizes the original micelle structure in oil and prevents wax deposition and viscosity changes. A chemical solvent is injected to dissolve and remove wax deposits. In this study, both methods of wax treatment were applied on a waxy oil well in Trinidad, to determine which was more effective and economical. An average oil production rate of 14.4 barrels of oil per day (bopd) was attained from chemical solvent injection and an average oil production rate of 13.4 bopd from passive energy wave application, resulting in cumulative oil volumes of 374 barrels and 349 barrels respectively. Oil inflow into the wellbore, or Productivity Index, increased significantly from pre-treatment conditions by factors of 10.4 with chemical solvent injection and 8.8 with passive energy wave application. From an analysis using profit per barrel of oil (Netback) economics, the total workover cost for passive energy application, including tool rental and installation costs, paid out in 58 days at an average production rate of 13.4 bopd. The total workover cost for chemical solvent injection, including chemical and injection equipment costs, paid out in 12 days at an average production rate of 14.4 bopd. Decline curve analysis showed that the historical production from the well followed an exponential decline model. This model was applied to production outputs resulting from both treatments and the analysis showed that the producing life of the well was altered by 19% with passive energy wave application and by 20% with chemical solvent injection. From oil sample testing, passive energy wave application caused an increase in oil API gravity from 22.5 to 28.8 °API and a decrease in oil viscosity from 439.1 to 23.7 centiPoise (cP). Production outputs and economics showed that chemical solvent injection was the more feasible wax treatment option for the waxy well studied. However, passive energy wave application was able to positively alter crude oil properties and showed notable success in preventing wax formation in this well.