A Study To Determine Necessity of Pilot Holes When Drilling Shallow Gas Zones Using Top Hole Dual Gradient Drilling Technology

Abstract

When drilling offshore, shallow gas hazards are a major concern because of their potential to cause a major blowout. This is a special concern when drilling in shallower water, where the gas influx reaches the rig sooner. A common practice used to avoid the potential dangers of shallow gas is to drill a pilot hole through the shallow gas zone with the hope that the smaller diameter hole will prevent such a large influx. The use of dual-gradient top hole drilling technology would allow for a larger hole to be drilled and the possible gas influx to be killed dynamically, which I have simulated with the use of a top hole dual-gradient simulator.