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.