Analysis of capillary interaction and oil recovery under ultrasonic waves

Abstract

Although, the effects of ultrasonic irradiation on multiphase flow through porous media have been studied in the past few decades, the physics of the acoustic interaction between fluid and rock is not yet well understood. Various mechanisms may be responsible for enhancing the flow of oil through porous media in the presence of an acoustic field. Capillary related mechanisms are peristaltic transport due to mechanical deformation of the pore walls, reduction of capillary forces due to the destruction of surface films generated across pore boundaries, coalescence of oil drops due to Bjerknes forces, oscillation and excitation of capillary trapped oil drops, forces generated by cavitating bubbles, and sonocapillary effects. Insight into the physical principles governing the mobilization of oil by ultrasonic waves is vital for developing and implementing novel techniques of oil extraction. This paper aims at identifying and analyzing the influence of high-frequency, high-intensity ultrasonic radiation on capillary imbibition. Laboratory experiments were performed using cylindrical Berea sandstone and Indiana limestone samples with all sides (quasi-co-current imbibition), and only one side (counter-current imbibition) contacting with the aqueous phase. The oil saturated cores were placed in an ultrasonic bath, and brought into contact with the aqueous phase. The recovery rate due to capillary imbibition was monitored against time. Air-water, mineral oil-brine, mineral oil-surfactant solution and mineral oil-polymer solution experiments were run each exploring a separate physical process governing acoustic stimulation. Water-air imbibition tests isolate the effect of ultrasound on wettability, capillarity and density, while oil-brine imbibition experiments help outline the ultrasonic effect on viscosity and interfacial interaction between oil, rock and aqueous phase. We find that ultrasonic irradiation enhances capillary imbibition recovery of oil for various fluid pairs, and that such process is dependent on the interfacial tension and density of the fluids. Although more evidence is needed, some runs hint that wettability was not altered substantially under ultrasound. Preliminary analysis of the imbibition recoveries also suggests that ultrasound enhances surfactant solubility and reduce surfactant adsorption onto the rock matrix. Additionally, counter-current experiments involving kerosene and brine in epoxy coated Berea sandstone showed a dramatic decline in recovery. Therefore, the effectiveness of any ultrasonic application may strongly depend on the nature of interaction type, i.e., co-or counter-current flow. A modified form of an exponential model was employed to fit the recovery curves in an attempt to quantify the factors causing the incremental recovery by ultrasonic waves for different fluid pairs and rock types.

Pore-scale investigation of immiscible displacement process in porous media under high-frequency sound waves

“…These mechanisms include oscillation and coalescence of oil droplets under a vibration field, reduction of wetting films adherence to rock and peristaltic movement of wetting phases. Also, cavitation was suggested to be a driving mechanism under ultrasonic energy earlier (Hilpert et al 2000;Rozina 2003;Rozina & Rosin 2003;Malykh et al 2003;Dezhkunov & Leighton 2004;Hamida & Babadagli 2007b). Cavitation occurs in a certain intensity of ultrasonic waves and causes sonocapillary effect and this phenomenon is more pronounced during static capillary processes (Rozina & Rosin 2003;Malykh et al 2003).…”

“…He assumed that this effect was due to a phenomenon called 'sonocapillary effect', in which the depth of fluid penetration into pores is raised due to the pressure created from cavitation which collapses bubbles. This effect was studied by a number of authors (Hilpert, Jirka & Plate 2000;Rozina 2003;Rozina & Rosin 2003;Malykh, Petrov & Sankin 2003;Dezhkunov & Leighton 2004) as reported by Hamida & Babadagli (2007b). Kuznetsov et al (1998) studied the effect of vibration on relative permeability and waterflood displacement rates.…”

Immiscible displacement of oil by water in consolidated porous media due to capillary imbibition under ultrasonic waves

“…[59][60][61][62][63] They observed that the ultrasonic energy positively affects the oil recovery depending on the interaction type ͑co-and counter-current manner͒ and interfacial tension between the immiscible phases. Their subsequent visualization studies revealed that considerable changes at the interface may occur under ultrasonic waves.…”

Effect of ultrasound radiation duration on emulsification and demulsification of paraffin oil and surfactant solution/brine using Hele-shaw models

“…More recently, a series of laboratory experiments was conducted by Hamida and Babadagli [12][13][14][15][16][17][18][19][20] to investigate the effect of ultrasound on capillary imbibition recovery of oil. In one experiment [12], they showed that the final recovery and recovery rate increased with regard to the type of fluid and matrix fracture interaction.…”