Research On Sealing Contact Characteristics Of Underwater Wellhead Connectors

With the increasing depletion of oil and natural gas on the earth, the world's attention has begun to shift to the exploitation of oil and gas resources under water. And the underwater oil extraction equipment has become the key technology of oil and gas exploitation. The premise condition of deep water mining is a safe, reliable and efficient deep water collet connector technology. Underwater production system in different conditions and harsh marine environment loads the subsea collet connector of high-pressure seal will produce leakage failure, endanger the safety of the water production, has aroused widespread concern in the global scope. In this paper, the contact characteristics and the fatigue life of the collet connector under the condition of preloading, working, and completion/workover are studied in this paper. The main research contents and conclusion are as follows:(1) The paper established the mechanical model of collet connector, analysis of contact load and deflection of hub between actuator, claw, hub and gasket ring in preloading, working and completion/workover condition bending moment; come up with the calculation formula of pre-tightening load and assemble load for collet connector, which was based on the design pressure. For the practical application of the deep water collet connector provides a theoretical basis. And from the micro perspective studied metal static seal forming process, metal contact link type is sealed to the ring type sealing process is analyzed, and found that the gasket ring if to form effective and reliable sealing condition, must have enough pre-tightening force of gasket ring surface of extrusion, the metal sealing ring plastic deformation in order to fill sealing surface of the micro fine gap, eventually forming effective sealing contact surface.(2) Through the mathematical model of the structure of collet connector seals carries on the simulation analysis, the preloading and the producing conditions of gasket ring, upper hub and lower hub obtain contact load, contact stress, effective contact width, compression and resilience curve analysis; Whereby, the axial pre-tightening force is greater than the radial pre-tightening force, it shows that the clamping jaw of the collet connector can be directly used to obtain a larger seal preload than the direct axial preload. The load of the contact surface of the gasket ring under the production condition is basically unchanged because the metal seal ring has played a self-tightening characteristic. The collet connector in preloading and working conditions are divided into five states, qualitative analysis the wellhead connector in various states of sealing performance, and analyze the main factors of collet connector sealing performance impact, collet connector sealing structure design, material and spare parts processing to provide a theoretical reference.(3) The INP program was transferred by the ABAQUS software, collet connector in completion/workover operation under bending load, the gasket ring and the upper hub, the gasket ring and the lower hub on contact characteristics under the condition of ocean wave simulation. Analysis of gasket ring in different moment loading conditions, the gasket ring of four contact surface contact stress and contact width and contact center and changes in the law; studying lower hub of collet connector hub surface force, deformation and stress variation, analysis of collet connector under the ultimate moment in completion/workover condition. Based on the vortex induced vibration load, the fatigue life of the collet connector upper hub, the lower hub and the gasket ring are studied, and the influence of various main factors on the fatigue life of the collet connector was studied.