Coping with Shallow Hazards in Deep Water Drilling: Consequences and Mitigation

Exploration drilling in the deep-water environment is fraught with challenges.The difficulty in deep water drilling lies in the progressively narrower operational window, which results from the diminishing gap between the formation pore pressure and the fracture pressure needed as water depth increases. Just beneath the seafloor, the main hazard is the existence of shallow water or gas pockets, which can lead to blowouts or destabilization of the seafloor during and after drilling. If these geohazards are not identified pre-drill, they may pose considerable risks to drilling operations, and the worst-case scenario is of losing the well along with serious containment issues. As a measure of caution when there is uncertainty on the formation just below the seabed, the top-hole drilling of a pilot hole riserless, along with the acquisition of real-time high-resolution seismic data, mitigates the risk to a considerable extent. The lessons learned are applied to the mainhole drilling. This paper explains riserless drilling and how a pilot hole drilled enabled drilling the main hole successfully in a deep-water challenging situation in South East Asia off the Borneo coast.