Study On Mechanical Properties Of Marine Double Derrick

With the development of drilling exploration work entering to the deep-water area constantly, the drilling equipment applicable to deepwater is paid more attention, and the dual derrick as the one of the key equipment of deepwater rig hoisting system, becomes the main configuration of deep-sea oil exploration and development because when the main and auxiliary rig work parallel to save a lot of work time in deepwater. The dual derrick is a kind of the new structure. But the research of the offshore derrick is still in the exploration stage in our nation, therefore, it is necessary to study on the dual derrick.The following several aspects of the dual derrick were researched:(1) Based on the introduction of the idea generation and application of the main and auxiliary wellhead operation and the dual derrick deep-water drilling operation process, the value of the constant load, work load, wind load and inertia force caused by wave was calculated according to the relevant load calculation theory.(2) According to the experimental tests and the finite element simulation, the finite element modeling method was determined. According to this method the finite element simulation model was established of the dual derrick, and the static analysis was undertook in the condition of the constant load, normal drilling load and the combination load, and the change rule of the strain, stress and displacement were obtained and found the weak link, and the improvement measure was put forward. Based on these the maximum stress was checked by the strength.(3) Dynamic analysis was done of the dual derrick including modal analysis, harmonic response analysis under harmonic load and transient dynamic analysis under tripping moment. Combined with the weak link in static analysis, the site which was easy destroyed by vibration was gained. And the improvement measure was put forward.(4) From the theoretical calculation and finite element analysis two aspects analyzed the stability of the dual derrick, and calculated the overall stability strength and local stability strength. Using the method of theoretical calculation, linear buckling analysis, nonlinear buckling analysis and existing initial defect nonlinear analysis, the instability critical load was obtained. And the stability of the dual derrick was judged, which provides a method for stability analysis.(5) The mechanical properties of the dual derrick and the single derrick were compared, which included the static analysis, dynamic analysis and the linear buckling analysis. And the conclusion that the dual derrick has higher safety and better mechanical property was got.The rule of the stress under the static and dynamic analysis was obtained, and found the weak link and the improvement measures were put forward by studying the mechanical properties of the dual derrick. The study provides a theoretical basis for the dual derrick safety assessment, design and structure optimization.