Mechanical analysis of tubing string in well testing operation

Formation testing is an important procedure in oil–gas field exploration and development. Tubing string may yield, break and buckle perpetually under actions of manifold loads in well testing operation, resulting in severe economic loss. Based upon operation procedures of formation testing, by taking into account well trajectory, component of testing string, borehole fluid property, internal and external pressure, friction factor between testing string and well wall, geothermal gradient, tubing temperature, test valve types, packer types, piston effect of packer, helical buckling effect of tubing, etc., mathematical models for mechanical analysis of testing string in whole testing operation have been established. These mathematical models have been solved with differential methods, obtaining parameters such as tension force, torque, stress, safety factor, stability and elongation. A software of mechanical analysis of tubing string in well testing operation is developed using Visual Basic 2008. This software has been applied to many wells to verify and optimize testing string combination in Northwest Oilfield Branch of China Petroleum and Chemical Corporation. A field application is provided. A discussion of relationship between the minimum safety factor and string break is made.

► The mathematical models for mechanical analysis of tubing string are established.
► The software of mechanical analysis of tubing string in well testing is developed.
► The application to field is proved effective.