Dynamic Analysis of Downhole Tool String in Uplift and Downshoot Motion

Abstract

Abstract Running various downhole tools in extended reach wells is usually very important for well operations in the oil production engineering. The various bottlenecks due to high drags or irregular boreholes are always the main reasons for tool resistance. Failure to reach target depth often has a profound consequence on well deliverability and overall cost. In this paper, we proposed an “uplift and downshoot” method to run the tool string. In this method, the tool may first be raised to a certain height (raising process), and then lowered quickly so that the tool “falls” from this height at a relatively fast velocity to help rush through the stuck points. The soft string model considering the effects of lowering velocity is established to simulate the tool falling process. By solving the tool axial acceleration in each falling interval with energy conservation, the axial force and acceleration distributed in the tool string during the entire running process can be determined. A case study of lowering measuring instruments in the completion of tubular of a water injection well is analyzed by the proposed method. In the assumed two situations with and without stuck points, the tool is lifted 15 m to simulate the rush through the process. Velocity and acceleration of every lowing height under different stuck resistances are drawn and listed to judge the tool passability. This work provides a way to run downhole tools and a matched theoretical method to help field operators lower downhole tools efficiently.