Environmental friendly water-based pre-flush formulation for oil & injector wells' acid stimulation

Aromatic based chemistries have been used extensively as additives in the pre-flush systems of acid stimulation programs. The need for these solvents stems from the requirement to displace oil or break asphaltic or waxy materials ahead of the main stimulation treatment. These chemicals while effective, are highly flammable, difficult to handle and have negative impact on the enviroment. Aromatic additives are always mixed with diesel-based pre-flush systems in acid stimulation jobs. If water is added to this system, the resultant emulsion damages the productivity of the formation. Water wetting surfactants typically of aqueous nature pose the same problems when mixed with diesel systems. The main challenge, however, is to mix these hydrocarbon-based fluids with water and surfactant to clean the wellbore and water-wet the formation face in preparation for the acid stimulation treatment. The objective of this work was to evaluate new environment-friendly water-based pre-flush formulations for oil and injector wells. The new aqueous Pre-flush formulations was developed to avoid the aformentioned problems with using diesel. The new Pre-flush formulations include between 10-15% blend of specialty surfactants and solvents, successfully homogenized with low-cost field water. These formulations are able to alter the wettability of the formation face by breaking the oily phase and separating it from the surface of the formation. The new formulations have high flash points and are biodegradable which results in easier handling and an environment-friendly alternative to existing diesel pre-flush systems. Wettability, stability and interfacial tension tests at reservoir conditions helped optimized the new formulation. The results showed excellent dissolving power for oily sludges and surfaces in addition to excellent stability and wettability. The new pre-flush formulations can enhance the reactivity of the acid with the formation and improve treatment results. It will enhance the flowback and post-treatment cleaning of the well.