| In deepwater drilling,drilling conductor has the function of carrying wellhead weight,maintaining wellhead stability and sealing shallow formation disasters,and it is an important circulation channel for drilling fluids.At present,jetting technology is the most widely used operation mode in deepwater drilling which is obviously different from shallow water and onshore drilling.The operation of the jetting can achieve two operations in a pipe column running,the drilling section of the surface casing section and conductor.In order to improve the efficiency of operation,improve the safety of operation and save drilling time,it is necessary to carry out the research on installation mechanism and safety control technology.Based on the theory of submerged jet and jet breaking,a theoretical analysis of the interaction between the jetting liquid column and the soil during the jetting process is carried out,and the displacement equation and the real-time bearing capacity model of the surrounding soil after the installation of the pipe are built.Considering the strength condition of the stratum soil,the combined structural parameters of the running string,and the influence of the jet factors,a modified model of optimal bit stick-out is built for efficient installation of the pipe.Combined with the characteristics of the installation and the disturbance characteristics of the soil,the boundary conditions and initial conditions of the consolidation of the soil around the pipe after installation of the pipe are analyzed,and the model is simplified.The stress recovery and consolidation model of the surrounding soil was established,and the model was preliminarily solved.The optimal time window for the stress recovery is set up with the safety and efficiency of the conductor as the objective function.An orthogonal simulation experiment based on in-situ soil is built.Through the design of stratified injection experiment with different strength formations,the influence of orthogonal factors such as different hydraulic parameters,bit stick-out and different pipe string combinations on the installation of pipes is simulated.The research shows that the drill bit stick-out is one of the key factors affecting the carrying capacity of the conductor.When the soil strength is small,the amount of drill bit stick-out in the pipe column has little influence on the installation efficiency,but it has a great influence on the bearing capacity.When the strength of the soil is large,the amount of the drill bit stick-out has little effect on the bearing capacity after the installation,but it has a great influence on the installation efficiency of the conductor.The system structure of adaptive CADA tool are built,and the working process and characteristic analysis,working principle analysis and adaptive working mode analysis are carried out.The kinematic analysis of the key mechanism is carried out,and the kinematic equation is constructed.And based on the motion equation constructed,the motion analysis of two conditions of uniform speed and uniform acceleration is carried out.At the same time,the work process of key institutions is simulated and analyzed.The mechanical analysis of the key bearing part is carried out,and the condition for determining the strength failure of the shear pin is determined.At the same time,the relationship between the prestressed load of the spring and the displacement produced by the thrust is established.Based on the finite element method,the stress area and load stress distribution of the tool under different load conditions are studied. |
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