Minimum Structure for Well Appraisal in Marginal Fields at 35m Water Depth without Jacket & Mudline Suspension System

Abstract

This paper proposes a minimum structure for drilling two appraisal wells. Conductors will be driven into seabed by a crane vessel or drilling-rig crane through a pre-installed lightweight guide-frame placed on seabed. After driving the conductors to required depth, the frame is raised and joined to the conductors at appropriate elevation by bolted and grouted connections. Six tie members connected between the frame and seabed by specially-designed small mat foundations will ensure stability of the structure against environmental loads. A small deck will be installed on the top of conductors to provide space for essential equipment required for prolonged well testing after departure of drilling rig. The platform will be accessed by small boats through a boat landing and ladder. In case of positive drilling outcome, a riser and flexible pipeline will be added to connect with the nearest subsea tie-in point. A detailed structural design of the minimum facility is performed to withstand omnidirectional environmental loads due to 10.0m high wave along with associated wind and current loads. Susceptibility of the structure against dynamic effect of wave loads is also investigated. Demonstration of structural adequacy against wave-induced fatigue loads and reserve strength against extreme environmental loads show the robustness of the minimum structure to perform against design environmental loads.