A Mechanical Model and its Experimental Verification for a Water Injection String in a Highly Deviated Well

Water injection strings in highly deviated wells are subjected to complex forces on the string bore. In this work, a mechanical model is developed for these forces and for those on downhole tools. On the basis of this model, and taking account of the characteristics of the string in different working conditions, a temperature field model and a pressure field model are introduced, and a statically indeterminate structural calculation method is adopted. A force tester for highly deviated wells is developed and used in eight tests on strings in the Jidong Nanpu oilfield making a comparison between the measurements from the tests and the results of calculations using the mechanical model indicates that the mechanical model exhibits high computational accuracy, with the errors at the wellhead being no more than ۱۰%, and that the forces on packers calculated from the model are in accordance with those measured in the tests. Thus, the mechanical model developed in this work is suitable for analyzing the forces on water injection strings and downhole tools in highly deviated wells.

Keywords:

highly deviated well , water injection string , packer , mechanical model , mechanics experiment