A Thermochemical Process for Wax Damage Removal

Abstract

Abstract Relevant declines in oil production on several Reconcavo Basin wells (NE Brazil) have been observed as a result of wax deposition phenomena. Evidences indicate several points of wax obstruction, such as: reservoir rock, perforations, casing annulus, tubing and production lines. The process consists on the injection of an emulsion formed by an aqueous solution containing nitrogenated salts, an organic non-polar solvent and a viscoelastic polymer. When the mixture is placed in the annulus, a strongly exothermic chemical reaction occurs, generating a high quality stable foam. The penetration radius of the foam into the porous media is enough to assure sufficient wax removal and induce immediate production enhancement. During well depressurizing, nitrogen gas, an aqueous saline phase and an organic mixture containing wax and the solvent are recovered. All the reaction products are environmental friendly. This paper presents lab and field results of this workover method based on in situ thermal generation of foam. Lab studies include foam formulation optimization aiming maximum wax deposit removal in several reservoir conditions. Field implementation includes the analysis of production enhancement in 10 wells in the area where the technique has been applied.