Application of ultrasonic as a novel technology for removal of inorganic scales (KCl) in hydrocarbon reservoirs: An experimental approach

Abstract

Inorganic scales are one of the most important causes of formation damage, which causes pressure drops near wellbores; these in turn impair permeability and severely reduce production in oil and gas reservoirs. This paper examines the effectiveness of ultrasonic waves in removing potassium chloride (KCl) scales. Twenty core samples with different permeabilities were exposed to KCl precipitation. After measuring the permeabilities of the saturated core samples, the samples were first subjected to water injection, and then to water injection with ultrasonic wave radiation. At each stage, sample permeabilities were measured and recorded. The results showed that water injection with two pore volumes did not significantly improve permeability, especially in low-permeability core samples. Ultrasonic wave radiation with water could efficiently improve permeability; this result is more obvious for samples with lower permeabilities. SEM images taken from thin sections of the core samples under water injection and water with ultrasonic waves showed that ultrasonic waves distorted the crystal lattice of the KCl scales, causing cracking and delamination. Creation of wormholes in KCl deposits within fractures also resulted from the application of ultrasonic waves. Analysis of chlorine in the output water from core samples in the core-flooding process showed that ultrasonic waves increased the solubility of scales in water, improving the recovery of permeability in the samples. Results of this study show that using ultrasonic waves can be considered a novel and practical method in the removal of inorganic scales in the near-wellbore region of oil and gas reservoirs.

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

“…Sensitivity study on core permeabilities gave rise to the conclusion that the effect of ultrasound on NaCl removal in the pore channels are more significant in low permeability reservoirs. Identical results were observed by the same authors for the treatment of KCl scales using combined ultrasound and water injection [28].…”

Recent developments, challenges, and prospects of ultrasound-assisted oil technologies

“…The authors suggested the increment in the US power in order to achieve better efficiency. However, increasing the US power above 1000 W has been reported to collapse core samples by Taheri Shakib et al [73] .

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“…There are several studies that have attempted to improve the permeability and pore structure of porous media which have been damaged, and hence, improve the oil recovery of the reservoir [71] , [72] , [73] , [74] , [75] , [76] , [77] . Some of these studies have focused on the removal of inorganic salts causing formation damage in the near wellbore region ( Fig.…”

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Fig. 10 Removal of inorganic scales in near wellbore region with US: a Ultrasonic flooding set-up (f = 22 kHz, Power = 1000 W) [74] b I Unplugging of sodium chloride deposit within a core sample through the injection of water with and without US treatment [74] II Unplugging of potassium chloride deposit within a core sample through the injection of water with and without US treatment [73] III Saturated Core Sample with Potassium Chloride Before Treatment [73] .

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“…Taheri-Shakib et al [73] studied the displacement of potassium chloride (KCl) scales from near wellbore region through water flooding with and without US. Twenty different core samples with various weight (114.29–199.78 g), diameter (3.747–3.869 cm), length (4.783–7.382 cm), density (2.651–2.834 g cm −3 ), porosity (10.426–27.916%), pore volume (7.697–23.906 cm 3 ) and permeability (11.9–2004.7 md) were saturated with crystals of KCl and utilized to replicate conditions in the near wellbore.…”