Casing Subsidy Operation Downhole Device Design

As the progress in oil-gas field development, many oil-gas fields has come into mid to late phase of development. Therefore, casings suffered from different grades of damage due to long term corrosion and formation effect. In order to prevent from borehole operation accidents, it’s important to analyze casing wear degrees and residual strength.This paper discussed general situation of casing wear in China. The damage is mainly deformation and leakage. And the casing repair methods are swage, milling,explosiveness and casing inner patch. Casing patch can not only prolong the life of oil and gas wells with little loss, but also can bring great economic benefits by reproduction. This is an effective measure for the sustainable development of oil and gas wells.According to casing wear situation, this paper analyzed the basic theories and feasibility of casing patch and the patch length 3-6m is allowable. So casing patch is feasible. This paper introduced the setting of design parameters, main parts design and parts strength proofing.Combining with field casing patch process, this paper analyzed the feasibility of casing patch.