Shallow water flow planning and operations: Titan No. 1 exploration well, deepwater Gulf of Mexico

Shallow water flows (SWF) from overpressured aquifers have been a persisten t problem in the deepwater Gulf of Mexico (GOM) and can create significant financial and operational risks for exploration and development drilling pr ograms. For the GOM, SWF intervals typically occur between 300 and 2,500 ft below mudline (BML) and in water depths greater than 1,500 ft. If left unc hecked, the disturbance from the water flow can cause loss of soil strength surrounding the wellbore, thereby compromising the structural integrity of the well. In industry, extreme cases have led to collapsed casing and/or t otal loss of wellbores. This paper details the up-front planning efforts implemented and the operat ional procedures utilized to successfully mitigate a SWF event experienced at the Titan No. 1 exploration well drilled in Garden Banks Block 785 (GOM) , in 4,640 ft of water. Operations at Titan were based on the philosophy th at performing a shallow hazards assessment, preparing and implementing SWF contingency plans, drilling a 9(7)/(8)-in. pilot hole (for dynamic kill), i dentifying a SWF zone quickly, controlling a water-flow zone with weighted mud (while drilling riserless), and using nitrified foam cement to seal off a water flow behind 20-in. conductor pipe, were all critical in successful ly containing and drilling through a SWF occurrence.