Dynamic Response Analysis Of Riser Considering Hydrodynamic Characteristics Of Subsea BOP Stack

LMRP(Lower Marine Riser Package)and BOPs(Blowout Preventor stack)are heavy and rigid.In the process of deep water drilling and completion,the upper part is connected to the riser system through a flexible joint,and the lower part is connected to the subsea wellhead.The hydrodynamic characteristics of subsea LMRP/BOPs will directly affect the response of the whole riser system.In the conventional method,LMRP/BOPs often use the combination of mass element and pipe element,and the hydrodynamic coefficient is also directly selected from the empirical value,which has defects in theory.In addition,when the dynamic analysis of riser is carried out,the calculation error of dynamic response of riser system will be large if the hydrodynamic performance of LMRP/BOPs is not considered.Based on the National Natural Science Foundation of my country’s “Research on Rigid-flexible Coupling Dynamics and Damage Control of Deepwater Underwater Wellhead Systems”,this paper studies the dynamic response of deepwater drilling riser considering the hydrodynamic characteristics of subsea LMRP/BOPs to meet the needs of deepwater oil and gas exploration and development in South China Sea,the relevant methods and conclusions can provide some reference for the design and safe operation of deepwater drilling riser system.The main research progress is summarized as follows:(1)Research on the calculation method of LMRP/BOPs hydrodynamic coefficients.According to the hydrodynamic calculation equation,the simplified treatment method and integral method of the nonlinear term of Morrison equation are put forward,and the calculation formulas of hydrodynamic coefficients under two conditions without submarine flow are derived.The least square method is used to calculate the parameters of the hydrodynamic coefficients of the LMRP/BOPs,and the corresponding calculation program is written by MATLAB.(2)Research on the method of determining hydrodynamic coefficients without seabed current,a more precise local finite element model of the subsea LMRP/BOPs was established.Based on the local model,the CFD calculation domain was established,and the boundary condition file of the subsea LMRP/BOPs was compiled by using the rigid motion macro.Calculate the hydrodynamic force of LMRP/BOPs,use the formula derived in Chapter 2 and the matlab program to calculate the hydrodynamic coefficient,and evaluate the accuracy of the algorithm.(3)Research on the method to determine the hydrodynamic coefficient of LMRP/BOPs under the action of ocean current,and the hydrodynamic force of LMRP/BOPs under the action of ocean current is calculated.The least square regression program of hydrodynamic coefficient under the action of ocean current is used to calculate the hydrodynamic coefficient,and the influence of different parameters on the hydrodynamic coefficient is analyzed.Combined with the actual conditions,the recommended values of hydrodynamic coefficients of LMRP/BOPs under the action of current are given.(4)Research on the coupling dynamic response of deep-water riser system considering the hydrodynamic performance of LMRP/BOPs,the coupling analysis model of riser system is established,and the dynamic response of riser system is obtained.Compared with conventional methods,the difference of dynamic response of riser system is analyzed.The applicability of this method is discussed through engineering cases.