Research On The Key Technologies For Design Of Deepwater Jack-up Unit

This dissertation is supported by the SINOPEC science project “Research on Key Technologies of Jack-up Drilling Unit with Truss Leg”.Taking deepwater Jack-up unit as example,systematic study on key technologies for design of deepwater Jack-up unit has been carried out.The research covers some hot issues such as wave-current on truss legs,leg structure parameter sensitivity,tubular joint strength,dynamic response,impact performance of spudcan on seabed and pudcan pulling resistance analysis,etc.,which acquires great progress and technological innovation.The research findings provide theory evidence and technical supports for the design of deepwater Jack-up unit with truss leg.Some research results have been successfully applied in the design projects such as the Jack-up drilling unit of Shengli oilfield working in 90 m water depth of Sinopec.The main work is summarized as follows: 1 Research on Wave-current Load on Truss LegsThe drag coefficient and inertia coefficient are the key parameters of wave-current load calculation.Based on the experimental model of chord with rack,the drag coefficient and inertia coefficient tests were systemically carried out in the section,the results of which were compared with the values recommended in SNAME.The range of the corresponding values of coefficients were given,and the recommended value curve in SNAME was corrected.Taking a deepwater Jack-up unit as the research object,the wave-current loads on trusse legs were calculated by using “equivalent model” and “detail model”of truss leg to study the applicability of the above two models.2 Analysis of Structual Type and Parameter Sensitivity of Truss LegAiming at three main types of K-type,X-type,inverse K-type truss legs,the applicability analysis of different types of legs was conducted.Collapse analysis method of Jack-up unit with truss leg was proposed based on the pushover pushover schematic.By using the above method,collapse analysises of deepwater Jack-up units were carried out to determine reserve strength ratio and collapse failure mode of different types of legs.Parametric modeling method of truss leg based on the software of SACS and the technology of visual basic for applications was proposed,which was applied to establish parametric FEMs of different truss legs respectively.The variation laws of different performance index with the change of leg span and bay were studied.“Tonado diagram” were used to study the parameter sensitivity of member size with the weight and strength of different truss legs,which determined the key parameters for the design of truss legs.3 Strength Analysis of Tubular Joints of Truss LegBased on thermal elastopplastic theory,The tubular joint strength analysis technology on the basis of simulation of welding and annealing process was proposed and applied to determine the influence of welding residual stress on the stress distribution of tubular joint.Numerical simulation method of the tubular joint of truss leg considering the weld was proposed.And experimental research on tubular joint was performed.The results of numerical simulation of the tubular joint were compared with experimental results and document data,which showed the proposed numerical modeling method was reliable and accurate.Based on that,the above numerical modeling method was appllied to establish the FEMs of K-joint,X-joint and inverse K-joint joint.The effect of the parameters such as ?,?,?,?,?,etc.on SCF of different tubular joints of truss legs subjected to three basic loads was studied.4 Dynamic Response Analysis of Jack-up UnitFEM of the deepwater Jack-up unit for dynamic response analysis was established to carried out the static analysis,modal analysis and transient dynamic analysis,which determined the influence of various parameters such as stiffness coefficient of elastic foundation,wave height,wave period,the distance between stern leg and center,the distance between stern and bow leg,leg bay and leg span,etc.on dynamic response of the unit.The influence of various parameters on the DAF of deepwater Jack-up unit was determined by the methods of displacement ratio and stress ratio,the results of which were compared with the results calculated by the method of single degree of freedom.Theoretical basis were provided for overall design optimization of the Jack-up unit by above studies.5 Analysis of Impact of Spudcan on Seabed and Spudcan PullingFEM of the impact of spudcan on seabed was established by applying explicit dynamics analysis method to study the dynamic properties of the impact under different velocities and angels.Numerical model of spudcan pulling process was established to study the pulling resistance.The jet tests of nozzle and spudcan pulling were carried out to study the variation of jet parameters,which could effectively reduce the pulling resistance.A new-type anti-clogging nozzle opened and closed automatically under water pressure was designed and used in the test,which showed that the new-type nozzle's anti-clogging effect was obvious and the jet effect of spudcan pulling could be ensured.