Study On Dynamic Behavior Of Deep Water Test String Under Impact Load

Marine deepwater testing string system is one of the important equipment of drilling platform, and its safety problems are directly related to the success of oil testing and oil production. In the process of marine deepwater oil testing, the impact load acting on string system mainly from the following two conditions, perforation condition and riser disconnection condition. Two kinds of working condition of the impact load are able to make the string system occurred vibration along the axis of string, and impact on the equipment above string system. Thus, in order to ensure that riser string can’t resonate with ocean environment or testing equipment under the impact load and string system, tensioning device of drilling platform and testing equipment are not damaged, many problems of marine deepwater drilling string system are created in mechanical behavior research, Such as:the design of new shock absorber, the dynamic response of string system under impact load, the establishment of mechanical model and so on. To sum up, they need to be disussed and solved.In order to solve these safety problems of perforated string and test equipment under impact load and deepwater testing string under the condition of disconnection mode. Micro element method is used to establish the coupling dynamic model of the perforated string-shock absorber considering the influence of perforated string’s weight, perforated string’s actual length and fluid friction. It also is used to establish the longitudinal vibration dynamic model of the actual riser string considering the marine environment. The corresponding initial conditions, boundary conditions and difference scheme of the model are given. Using the difference scheme, the calculation program and the simulation software is developed. Taking the actual testing string system design in the South China Sea for example, the dynamic behaviors of perforated string under perforating impact loading and riser string under the condition of disconnection mode are studied. These have very important theoretical and practical significance to improve the safety of downhole string system.