Assessment and Numerical Simulation of the Pendulous Installation Method in Deepwater

Abstract

The final frontier of the oil and gas industry is considered by many to be deepwater fields (1500 m - 3000 m). With the recent fall in oil prices, the industry has however seen many deepwater projects postponed as a result of many operators' unwillingness to invest in capital intensive projects. Costs related to the installation of subsea hardware account for up to 30 % of the total capital invested, and significant improvements can therefore be made with respect to this aspect of deepwater developments. Statoil has a goal of being able to install subsea hardware at 3000 m at the same cost as 300 m.

The Pendulous Installation Method is a new state-of-the-art method, until now minimally investigated by the Norwegian oil and gas industry. The method involves allowing relevant subsea hardware to free-fall in a pendulous motion into position above the seabed. Statoil has recently released the Dual Cap-X concept, that likely will be an integral part of future subsea fields. The intention of this thesis is to evaluate the potential of installing the Dual Cap-X at 3000 m water depth using the Pendulous Installation Method.

Numerical simulations in SIMO and Coupled SIMO-RIFLEX were conducted to evaluate the feasibility. The Splash-Zone and Free-Fall phases of the operation were studied in detail. Sensitivity to relevant parameters that may be detrimental with respect to operability were investigated. Design operational limits were determined for relevant phases with respect to relevant acceptance criteria. Operability with respect to weather windows was evaluated based on the determined design limits, and potential improvements discussed.

The findings indicate that the operability and associated cost of the method at 3000 m water depth are comparable to that of traditional subsea installation of a subsea template at 300 m. Potential improvements with respect to operability exist, and should be pursued to optimize the method as well as susbea installation operations in general. If properly executed, it appears that the method has the potential to render deepwater subsea fields feasible.