Large-diameter glory-hole drilling: evolution from 12-to 20-ft diameter

To drill for oil and gas in shallow, ice-infested waters, a hole needs to be excavated in the seafloor to protect subsea blowout preventers (BOP's) from ice-scour damage. Canadian Mariane Drilling pioneered the use of large-diameter glory-hole drilling systems by designing, building, and patenting a 12-ft [3.7-m]-diameter prototype bits system, a 17-ft [5.2-m]-diameter upgrade, a 20-ft [6.1-m]-diameter standard system, and a 20-ft [6. 1-m]-diameter enhanced system. The enhanced bit design incorporates high-pressure jetting, boulder storage, pilot-hole centering, and other features that allow a 36-in. [0.91-m]- hole to be drilled through the body of the bit. An optional feature is the ability to drill and case the glory hole simultaneously.