As oil and natural gas wells in Alaska’s Cook Inlet decline and the platforms used to capture the petroleum resources reach the end of their useful lives, operators are exploring options for the safe and efficient removal of the massive structures. HEA was approached to determine feasible and cost effective methods for removing the structures and provide technical assistance during the planning phase of the long-term removal effort.
In addition to more traditional heavy lift methods for removing the structures, the viability of re-floating the platforms was researched and analyzed. Detailed buoyancy calculations were performed to determine the amount of additional floatation necessary to lift the platforms off the seabed floor and ultimately rotate the entire assembly, including both the jacket and topsides, into a horizontal position for towing to shore. To assist with this analysis, a full calculation of the platform weight was performed and weight reduction options were considered. Pile pull out resistance was also calculated based on estimated soil properties and depth of the severed piles. Floatation tanks were then sized to achieve the desired buoyancy force and rotational moment. Findings were presented to the client for further consideration and project planning purposes.