Geography 2152F/G Study Guide - Final Guide: Soda Straw, Blowout Preventer, Drilling Fluid
25 Apr 2017
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An oil well below the sea level over 400 meters is a deep water well. The seafloor falls off the gently sloping continental shelf into jumbled-basin-and- range-like terrain, with deep canyons , ocean ridges, and active mud volcanoes. Commercial deposits lie deeply buried, often beneath layers of shifting salt that are prone to undersea earthquakes. Temperatures at the seafloor are near freezing, while the oil reservoirs can hit very high temperature. Pockets of explosive methane gas and methane hydrates are frozen but unstable, lurk in the sediment . The drill pipe got stuck in the borehole , as did a tool sent down to find the stuck section. The drillers had to back out and drill around the obstruction . On the night of april 20, investigators suspected, a large gas bubble somehow infiltrated the casting, perhaps through gaps in the cement, and shot straight up. The blowout preventer should have stopped that powerful kick at the seafloor.
