Mechanism And Experimental Study On Ultrasonic - Induced Shale Gas Desorption And Improvement Of Seepage Characteristics

The exploitation of unconventional gas reservoir has been a central issue in China,currently. Shale gas,as the main force of unconventional energy source,plays an important role.Horizontal-drilling technology and fracturing-exploitation combine the main ways to exploit shale gas reservoirs.These measures are all based on how to build and expand flow-channel,effectively.But rarely any such a theoretical or applied technology focuses on the adsorption characteristics of Shale gas itself. So it has a certain research and practical value to explore a new method of ultrasonic for improving the seepage desorption efficiency of shale.The basic points in this paper,are on the aspects of adsorption and seepage characteristics of shale gas.Based on extensive literature research and the development status of shale gas reservoirs in China;Summarized the application and limitations of shale gas’s drilling technology and stimulation technology;Depth analysised of shale gas reservoirs’"self-product and self-storage"type of reservoir forming mechanism and its mineral composition and pore structure characteristics; Depth knowledged and studied ultrasonic attenuation characteristics, mathematical model of acoustic cavitation characteristics;Analyzed the adsorption-desorption characteristics of shale gas reservoirs,and supercritical adsorption theory and single-molecule hybrid multilayer adsorption theory.Demonstratied the mechanism of ultrasonic can promote shale adsorption solution based onthe physical nature of adsorption mechanical angle;Studied the factors to affect the seepage of shale reservoirs.Discussesed the mechanism and characteristics of how ultrasonic to promote shale seepage in microscopic point of view.And also based on theoretical research,conducted ultrasonic attenuation-coefficient measurement experiment,ultrasonic promote shale’s desorption experiments and experimental study of ultrasonic increasing permeability.Developed the experimental thoughts of designation,experiments and mathematical models and principles of treatment; And designed, assembed or modificated laboratory equipments.Mastered the laws of ultrasonic attenuation and its disseminate roles in shale samples; Aalso verified that there is a certain improvement of adding ultrasound on shale desorption efficiency and flow capacity.Based on the theoretical discussion and experimental verification in this paper,and came to the conclusion that cavitation and mechanical vibration are the major factors to promote desorption and enhance the ratio of shale permeability.And validated the shale’s flow capacity increased under the action of ultrasonic,shale samples at the frequency of40KHz ultrasonic action,which was measured penetration increased by about8%.The effect is so obvious;By comparing the ultrasonic signal attenuation with the shale sample length change from the display of oscilloscope,I got the attenuation coefficient of ultrasonic in shale.It will be a useful guidance for further researching on ultrasonic propagation in shale.