| With the rapid advancement of science and technology,enhancing the exploitation and development of natural gas has become the primary task to advance China's social progress as well as the global economic development.Specifically,the employment of horizontal wells in China has greatly improved the recovery rate of natural gas demonstrating unique advantages in economic technology and recovery efficiency.However,production of water will inevitably occur during the production of gas wells and the accumulation of the produced water can lead to liquid loading in the wellbore interfering in the normal production process and reducing the recovery of gas wells.Therefore,it is critical to identify the time and location of liquid loading in order to implement liquid unloading technology and effectively improve the recovery.This thesis fully investigates various models and methods for estimating liquid loading and discusses the liquid carrying laws in the vertical,inclined and horizontal sections of the double-branched horizontal well.Based upon the theoretical analysis and the production data of the double-branched horizontal wells,the critical liquid-carrying model suitable for the determination of the liquid loading in double-branched horizontal wells was selected and the drag coefficient K_d was determined.According to the actual production data,the gas production decline law was determined,and a set of liquid accumulation identification method combining Arps production decline curve and IPR curve was proposed.This method was applied to analyze the gas wells with liquid loading issues and determine the time when liquid loading forms and calculate its height.Finally,by taking the on-site liquid loading gas well as an example,the variation in gas well production and gas flow rate was analyzed considering the formation pressure decline under different wellhead pressure and with various sizes of the velocity string. |
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