| One of the main challenges associated with drilling in deep water is control of the recoil behavior of the drilling riser after an emergency disconnect. Since the riser recoil process involves the interaction between riser, tensioner, drilling fluid and sea water, the recoil response is complicated and difficult to analyze. The recoil behavior could lead to serious damage to riser, platform as well as workers, and in order to avoid the drilling accidents, it is necessary to implement an anti-recoil system that controls the level of tension applied to the riser after an emergency disconnect. The main influence factors of riser recoil control operation involve tensioner system, anti-recoil system and drilling fluid. Once the LMRP is disconnected from BOP, the tensioner system and riser system parameters change rapidly and the recoil control technology is important for ensuring the safety of deep water drilling riser. This paper was supported by the National Major Science and Technology Project “Research on Deepwater Drilling Riser Operation Management and Safety Evaluation Technology”, and research on deep water drilling riser recoil control technology was conducted. The research result can provide reference for the safety management and emergency decision of deep water drilling risers. The main research developments are as follows.(1) In order to understand the riser emergency disconnect and recoil behavior, the interaction between riser, tensioner, drilling fluid and sea water was analyzed and the riser emergency disconnect reason and recoil process were described. The emergency disconnect and recoil control operation guidelines were provided and the main influence factors were determined.(2) The structure and principle of drilling riser tensioner were introduced in the paper. To calculate tension force of the tensioner, the ideal gas equation, the pressure drop in the hydraulic pipe as well as friction characteristics of the cylinder were analyzed. The simulation model for riser tensioner was built by AMESim software to calculate tension force and tensioner stiffness. And consider the dynamic characteristics of tensioner, the influence of tensioner on riser soft hang off was studied.(3) The drilling fluid retainment and release problem model were studied. The influence of drilling fluid retainment on riser hang off and the friction force applied to riser caused by drilling fluid release were analyzed. The riser collapse problem during drilling fluid release was also analyzed. Then, consider the tensioner, riser and drilling fluid release, the riser recoil response was analyzed based on ANSYS finite element software.(4) The structure and principle of riser recoil control system was studied and the analysis model was built. Based on AMESim software, the riser recoil control operation was simulated. Then, riser recoil response under different operation conditions were calculated and riser recoil control strategy was provided. |
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