How a Deep Water Well is Drilled - Drilling 101

Summary

The video explains the main stages of drilling a deep-water well, from selecting a site to installing the casing needed for future production. It emphasizes that planning, pressure control, and well construction are central to drilling safely.

Main ideas and process

Plan the well and select a site

• Seismic technology is used to identify potential oil and natural-gas reservoirs beneath the seafloor.
• Geoscientists select a seafloor location and well path intended to reach the target while prioritizing safety.
• For an exploratory well in water depths of up to 9,000 feet, the site is generally directly above the reservoir.
• Planning and preparation can take years.

Use a deep-water drilling rig

The rig may be on a drillship, a semi-submersible vessel, or a floating production platform. Rigs use:

• A hoisting system to raise and lower drill pipe and tools
• A pumping system to circulate fluids
• A blowout preventer (BOP) to help control well flows

Set the initial base pipe

Shallow seafloor sediments can be soft and loose, so a large-diameter base pipe or casing is placed to help prevent the well from collapsing and to support the wellhead.

The assembly is lowered to the seafloor. The driller starts it into the sediments, then uses pumped water or drilling fluid to jet it into place. Once the wellhead reaches the required position, the drill bit and string are released from the jet pipe, and drilling continues.

Drill using circulating mud

Mud is pumped down through the drill pipe, exits through jets in the bit, and returns up the space between the pipe and the wellbore walls. The video describes three functions of drilling mud:

1. Carry rock cuttings out of the hole.
2. Cool and lubricate the drill bit.
3. Fill the wellbore with fluid to balance pressure and help prevent formation fluids from flowing into it.

The mud described is a water-based mixture containing clay for thickness and finely ground rock, such as barite, for weight.

Install and cement casing

At a planned depth, drilling stops and the drill bit is pulled out. A casing string is run into the well. Cement is pumped down inside it, followed by mud; a cementing plug separates the two.

The cement is pushed into the space between the outside of the casing and the open-hole wall, securing the casing. Some locations require a second surface-casing section. The well is drilled deeper, then another, smaller casing string is installed and cemented using the same general process.

Install pressure-control equipment before drilling deeper

Deeper rock may have pressure too high for the water-based mud used earlier, or drilling may approach oil or gas before the next section begins. A BOP stack and riser are therefore installed at the seafloor.

The BOP is a system of valves and rams intended to protect the rig and environment if well fluids flow upward. The riser connects the rig to the well and provides a route for drilling fluid and rock cuttings to return to the surface. The BOP stack is fully tested before drilling resumes.

Continue drilling toward the target

Drilling proceeds through the BOP, with additional casing strings run and cemented as needed to cover open-hole sections. When the targeted oil- or gas-bearing zones are reached and their presence is confirmed, a final casing string may be installed.

That casing supports safe future production if the seafloor location is suitable for development.

Speakers or sources featured

• Narrator: An unnamed narrator explains the drilling process.
• Source: Shell, as identified by the video title and channel context.