Study On Leakage Prevention And Leaking Technology In Zhangwu And Jiulongshan Areas

Lost circulation is a Complex downhole accident that the fluid flowed into the formation when drilling, cementing, completing, workover and other operation. For drilling engineering, lost circulation means drilling fluids lost to the formation in the drilling process, lost circulation is not only time-consuming and mud-loss, but also may cause sticking, blowout, well collapse etc. In this paper, with the background of Zhang Wu oil field exploration area and Jiulongshan structure in the northwest of Sichuan-exploration area, three parts are researched:judging method of drain layer features in the process of drilling, evaluation on indoor plugging experiment of drilling plugging agent according to the characteristics of leakage; plugging technology to Improve the bearing capacity of drain layer for the purpose of safe operation in drilling and cementing.judging method of drain layer characteristic occurred during drilling is gained mainly through logging parameters and well logging parameters. Logging parameters studied the response of standpipe pressure, total cell volume, export flow to the drain layer characteristics, lost circulation type can be determined by the change of total pool volume, and leakage pressure can be determined by the change of standpipe pressure and outlet flow. Well logging parameters researched the change of conventional logging series worth in the electrical logging, acoustic logging, radioactive logging, image logging, etc and analyzed different response characteristics of the series of log values at the drain layer position. Studies suggest that well logging parameters interpretation can predict the position of the drain layer, estimate leakage channel size and type, and provide the prediction of well leakage location for subsequent drilling.In indoor mud plugging experiments, Plugging formulations that suitable for sealing agent and different crack width of Akira Zhangwu Oilfield and Jiulongshan structure are optimized. The resiliency and expansion capability of several sealing agents are examined by simulating different formation environments, such as temperature, salinity and pH, to preferred sealing agent, in the optimization experiments of sealing agent formulation, according to the main width of the crack formation, sealing formulations of plugging cracks with different width are obtained by simulating five kinds of crack size with different widths.Plugging process to blocking formation for different characteristics of drain layer, like cycle plugging technology, static pressure technology and increased pressure technology, are discussed, according to the drilling fluid density that meet the requirements of security drilling in actual formation, appropriate process to improve plugging bearing capacity of the formation is selected, which meet the requirements of security operation and the saving of material and manpower.