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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 43447 (06)
- University: Sharif University of Technology
- Department: Chemical and Petroleum Engineering
- Advisor(s): Ramazani Sa’adat Abadi, Ahmad; Jamshidi, Saeid
- Abstract:
- Near wellbore formation damage is caused additional pressure drop around the wellbore and therefore decreased the oil or gas productivity of the well. The usual methods for removal of these damages are acidizing and hydraulic fracturing which have operational limitations in addition to high costs. Thus the researchers are motivated to find new methods and technologies specially the use of mechanical waves for well stimulation purposes.Ultrasonic waves have been extensively used in many industrial applications including clean devices, pipes and vessels. A clear extension of this usage is the removal of wellbore contaminants by exposing it to high-power ultrasonic waves. Although several laboratory experiments have been conducted for this purpose in recent years, the lack of theoretical modeling is perceptible. In this paper, a mathematical model for ultrasonic propagation through the porous medium around the wellbore is presented. The equations of wave propagation are written in a cylindrical coordinate according to Biot theory and the induced stress to the rock is calculated at each point using finite difference approach.Then investigate the effects of several parameters such as wave frequency and amplitude on the results. By comparison of imposed local stresses with adhesion forces between scales and rock, the properties of ultrasonic transducer, such as frequency and amplitude, which are needed for breaking adhesion forces, can be determined. The results show that the wave with frequency about 25 KHz and amplitude about 50 microns will apply up to 1×108 Pa radial stress to the adhesion surface between deposits and rock. This value of radial stress is equal to the required stress for breaking some usual concretes approximately, and therefore it seems to be able to separate the scales from the rock.Thus the wave has ability to clean the pores, if the required stress for separation of scales is smaller than this applied stress
- Keywords:
- Formation Damage ; Ultrasonic Waves ; Well Stimulation ; Wave Amplitude ; Microvibration
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