A rigid completion (production) riser is analysed for 3300 ft water depth operation in the connected mode. Structural and hydrodynamic analyses of the riser connected to the wellhead system and to the vessel are performed in order to determine the operational windows (operational limits) of the riser and to evaluate the loads transmitted by the riser system to the wellhead system, including the subsea tree and the workover BOP. Frequency domain analysis methods are used to predict the structural behaviour of the riser. From the analyses results, some relevant questions are studied, such as the influence of the consideration of the wellhead flexibility in the riser resultant stresses.
riser, operational window, The rigid marine riser is the critical operational and structural link between the sea floor and a floating drilling or production vessel. In essence, a marine riser extends the well at the ocean floor to the floating vessel. A completion or workover riser system is generally used to run the tubing hanger and tubing through the drilling riser and BOP into well bore, to install the subsea tree and to reenter the well through the tree, as described in API RP 17A (1987). The completion or workover riser must accommodate wireline tools for the operations and resist pressure loads and external loadings. Tension applied at the top of the riser is necessary to provide enough stiffness to withstand the environmental and operational loads through the beam-column effect. A failure of the riser can cause substantial losses in terms of equipment, production and operating time. Although the rigid riser is a simple structure, its behaviour and loadings are complex and sophisticated computer programs are necessary to correctly predict its response.
