Comparison of Acidizing and Ultrasonic Waves, and Their Synergetic Effect for the Mitigation of Inorganic Plugs

Abstract

The oil and gas industry is plagued by inevitable formation damaged in the wellbore proximity during entire life of the well. Therefore, it is indispensable to ameliorate the damaged permeability by either using conventional applied techniques or ultrasonic-assisted stimulation method. The latter is characterized by efficient, simple and convenient, and environmentally secure method. Due to these distinguished characteristics, the demand of this physical Enhanced Oil Recovery (EOR) technique increased in petroleum industry. In this study, ultrasonic waves and hydrochloric acid (HCl) were used separately as well as in combination to recover the lost productivity caused by calcium carbonate (CaCO3) inorganic plugs in low permeability sandstone core samples. Results showed that permeability recovery increased with irradiation time up to 100 min; however, it decreased with further irradiation. This deviation could be due to particles bridge formation at later stage. In addition, optimum frequency and power of ultrasonic waves (20 kHz and 1000 W) significantly recovered the damaged permeability. Although maximum frequency (25 kHz) could not achieve maximum permeability, but higher power was quite effective. The damaged permeability recoveries of HCl and ultrasonic waves were 44.5% and 37.6% respectively, but the permeability recovery was escalated to 61.5% when HCl and ultrasonic techniques were applied together. Inorganic plugs using ultrasonic waves could chiefly be caused by cavitation, acoustic streaming, and heat generation in three different ways, such as cavitation, boundary friction and transformation upon hitting the medium.

Recent applications of ultrasonic waves in improved oil recovery: A review of techniques and results

“…The ultrasound-chemical technique recovered more permeabilities than the other two techniques. Similar results were observed in the study (comparison of ultrasound treatment at 20 kHz and 1000 W, chemical injection and ultrasound-chemical combination treatment) of Khan et al [11].…”

“…The results of this field test have shown consistency with the laboratory results of Wang et al [10] and Khan et al [11]. As seen, after sonochemical excitation, the production of oil was better, and the effect of treatment lasted longer.…”

“…30 kHz 1000 W -Khan et al [11] ultrasound-chemical combination technique had the best effect for damage removal than using ultrasonic treatment or chemical injection alone.…”

Study on frequency optimization and mechanism of ultrasonic waves assisting water flooding in low-permeability reservoirs

“…The formation of micro-fractures may be attributed to ultrasonic cavitation effect. Ultrasonication generates fluctuating low-pressure and high-pressure waves in the liquid phase, resulting in the formation and violent collapse of small vacuum bubbles [47] . Such phenomenon is called cavitation and yields high-energy impinging liquid jets and strong hydrodynamic shear-forces.…”

“…However, we hardly spot the micro-fractures in these two core slices. This is because the intensity of the cavitation effect yielded by ultrasonic wave would be comparatively less at higher frequency and the alternating times are too short to make the vacuum bubbles large enough and violently implode [47] .

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