Hybrid Conductor-Supported Tripod Platform: Brownfield Design Perspective to Unlock Production Capacity

Abstract

Oil and gas companies have shifted their investment priorities to low CAPEX brownfield projects in response to historically low oil and gas prices. One approach is to increase the production by drilling new wells and tying them back to existing tripods. However, existing tripods have limited as-built design data and are usually near the allowable structural capacity limits. This study introduces a novel concept of the "hybrid conductor-supported tripod" to support the new wellheads. This approach minimizes the need to modify the existing tripods. The hybrid conductor-supported tripod utilizes the new well conductors to support the wellheads, extends to the existing tripod topside to support the production facilities, and resists lateral loads from the new wellheads. Such hybrid conductor-supported tripod takes advantage of the axial compression capacities of the new conductors while its lateral resistance is provided by integrating only the new topside with the existing tripod's topside. Thus, the underwater structural modifications of the existing tripods are minimized. Design and construction challenges commonly encountered during the design phases of brownfield projects include: 1) lack of tripod jacket and foundation as-built data, 2) need for bracing the new conductors to the existing jacket underwater due to buckling and vortex issues, 3) as-built conditions of the tripods are already near their structural capacities. The design and construction issues experienced in low budget and tight schedule brownfield projects are alleviated with the use of a hybrid conductor-supported tripod. A parametric study was conducted to identify the minimum conductor pipe diameters needed for hybrid conductor-supported tripods at various shallow water depths in benign environmental conditions. The in-place conditions of several existing tripods were investigated before and after the hybrid conductor-supported tripods were integrated with the existing tripods. Using hybrid conductor-supported tripods enable production increase on existing facilities with minimal CAPEX investment. This is accomplished by: 1) utilizing existing tripods to increase production, 2) mitigating the need for as-built data, especially underwater jacket data, 3) eliminating additional axial loads on the existing tripods, 4) implementing minimum deck extensions on the existing tripods. The hybrid conductor-supported tripods provide the structural expansion need for the new wellhead facilities while keeping the existing tripods in their as-built conditions. Reducing the need for the current condition and the exact as-built underwater information of the existing tripods will accelerate the execution of the low budget and tight schedule production increase brownfield projects.