In offshore petroleum drilling, the BOP stack is run into the sea by a string, composed of long and wide-bore pipes, called the marine drilling riser. It also connects the BOP stack (BOP + LMRP) on the wellhead to the drilling vessel at the sea surface, serving as conduit between them.
While being lowered down, a special riser spider is used to support the riser. During this operation, the hanging riser is under the effects of sea current, waves and displacements induced by sea surface drilling vessel motions.
The discovery of petroleum fields in deeper waters, usually in remote and harsh environments, makes it a requirement for the riser to withstand more severe conditions. Nevertheless, riser design and failure analysis during this operation is a seldom studied topic, even though drilling in ever increasing water depths imply the riser is subject to risks inherent to running a BOP for a longer period of time. It is of utmost importance the adequate modeling of the system’s response during this operation, in order to safely evaluate failure cases due to extreme static and dynamic stresses.
As such, the present paper describes and proposes a methodology developed for the analysis of extreme stresses that act over the riser during the BOP running. Case studies were conducted for a water depth up to 2000 m. Numerical simulations were run to evaluate system’s static and dynamic behavior due to environmental loading.
As a result conclusions were drawn regarding operation limits in ultra-deep waters. Results are shown through charts that delimit ocean conditions and vessel’s response that are secure to operate under.