Study On Application Technology Of Subsea Wellhead And Christmas-Tree In South China Sea

Since the concept of the subsea wellhead was put forward firstly in America in 1947,the subsea production technology has been developing and gradually applied to the deepwater and ultra deepwater.As the subsea wellhead and christmas tree are the key equipments of the subsea system, the operation safety and field application technique is particularly important.The paper is supported by the project of “Stability Assessment on the Subsea Wellhead and Subsea Christmas-tree(2011ZX05026-001-01-04)” sponsored by National Science and Technology Major Special Project. The research of subsea wellhead and subsea Christmas-tree application technology in south China sea is conducted.The main work is summarized as follows:1. The subsea Christmas-tree running operation technology analysisThe subsea Christmas-tree running operation technology at home and abroad is studied.According to the structure features of the subsea horizontal and vertical tree,the subsea Christmas-tree running operation procedure with drill pipe is studied.Running string force model and subsea Christmas-tree running operation finite element analysis model is established.Besides,drill pipe axial strength regulation is analized, the subsea Christmas-tree running limitation criteria and operation envelope is proposed.2. The subsea wellhead and Christmas-tree system stability studyTheoretical analysis model of the subsea wellhead and Christmas-tree system stability is studied.Finite analysis model for drilling riser-subsea wellhead and Christmas-tree-conductor coupled system is established.The subsea wellhead and Christmas-tree stability and conductor bearing capacity is testified.System stability rule under different factors are calculated and summarized.At the same time,post-assessment of a deepwater well in the south China sea is carried out,the the engineering application is realized.3. Local strength analysis of Subsea wellhead and Christmas-treeSimplified analysis model and modeling scheme of the subsea wellhead and Christmas-tree three-dimensional structure is studied. Application load and finite element analysis is conducted on the model.The mises distribution rules of subsea wellhead system under different boundary conditions and completion condition are studied respectively.Similarly, in completion condition and production condition, the mises distribution rule of subsea wellhead system under different boundary conditions and water depths are calculated and analized respectively.4. The lectotype of the subsea wellhead and Christmas-treeThe subsea wellhead and Christmas-tree products at home and aboard are investigated.The technical parameter and structural feature of different products are summarized.The technical and economic selection influencing parameter of wellhead and Christmas-tree are qualitatively analized.According to the system stability analysis and local strength calculation of subsea wellhead and Christmas-tree and the subsea Christmas-tree running study,the type-lectotype scheme of the subsea wellhead and Christmas-tree in south China sea is proposed.