Study on the stability of tubing under pressure operation

The operation with pressure is to carry out the lifting and lowering of the tubing or oil rod without releasing the pressure. Compared with traditional downhole operation, the operation with pressure can ensure the upward and downward of the string without pressure relief. The effective plugging of the inside of the oil pipe and the annulus of the oil jacket is the main characteristic of the operation under pressure. When the tubing is lifted, the interior of the tubing is sealed and blocked due to the downhole pressure, it will generate upward force on the tubing, which will make it difficult to run the tubing. The project uses a down-pressure device to assist the down-flow of the tubing. If the down-pressure is too large, buckling instability occurs, which increases the construction difficulty for the down-run operation. Combining elasto-plastic mechanics buckling instability theory and finite element simulation method to study the compression stability of tubing under pressure. The variation law of critical buckling force of tubing diameter, length and wall thickness under pressure is analyzed by numerical model, which provides the basis for equipment design and process plan formulation.