The Analysis Of Casing Deformation Under Non-uniform Elliptical Load With VB

The loss of the casing of oil well will cause great losses annually, which seriously affect the normal oil producing in the oilfield. The most common reason for the damage of the casing is that the uneven stress caused by stratum creep acting on it. It have great significance for increasing casing's life in service that researching on the mechanism of the casing damage produced by the non-uniform stress on it.In this thesis, it is concluded that the external load acting on the casing caused by the uneven stratum stress is approximately oval. A formula has been obtained that the relational expression of the external load of the casing in oilfield and depth of strata according to the geologic parameters in west district of Dagang oil field. The basis of calculation is provided for further research in the relevant areas. The finite element model of the common casing (steel grade J55, N80 and a variety of different thickness) is established using ANSYS software, and then the deformation of casing caused by elliptical external loads and the stress condition are simulated and analyzed, after that the concept of the equivalent breaking load is introduced which making the size of elliptical external load has a quantitative criteria for judgment. Eventually the ultimate bearing capacity and deformation of the various types of casing are obtained and the main reason for the loss is the deformation of the structure instead of materials. The proposals are put forward based on the analysis of the deformation of the casing and simulation of the casing repair processing.A clearer and intuitive software based windows relating to the deformation by stresses of the casing is developed by using the Visual Basic software programming on the basis of the former data. The software can transform the processing of settings of all kinds of parameters and the establishment of finite element model into the background which will save the analyzing steps greatly. Therefore, the non-professionals or people who are not familiar with ANSYS software can understand the stress deformation condition of casing in the specific wells quickly and accurately. It has significant practical guide for the actual oil production.