Increasing the value of deepwater wells

A significant improvement in deepwater well integrity and value can be accomplished by deepening the structural casing to have a dual functionality.  This duality is as a structural conductor and its placement into stronger formations for increased casing shoe strength.  This results in fewer riserless casing strings and setting the all casings deeper to reach the planned well depths with larger casing diameters than current practice.

The larger hole and casing annuli result in larger deepwater drilling operating windows for better management of drilling friction pressure (ECD) reducing incidents of loss circulation, use of contingency liners, and early termination of well depth.  The value of this design approach results from:

1. improving the probability of attaining the deepwater well objectives of getting to planned depths,

2. improving well integrity with less risks involved in the loss circulation/well influx cycle,

3. reducing well construction time with less casing strings, and

4. increasing production with larger casing and completions across the targets.

What is the Subsea Drive System?

The method to deepen the structural conductor is the application of casing drilling utilizing the Subsea Drive System. The principle of casing drilling allows simultaneous drilling and running casing while mitigating shallow drilling hazards. In deepwater this is “liner drilling”.

The Subsea Drive System (SDS) is a proven liner drilling technology specially designed for large and heavy riserless casing strings. The SDS runs the casing to the seafloor, drills in the structural casing to depths determined by the prevailing pore pressure/fracture gradient, and facilitates cementing, all in one trip. The low-pressure wellhead housing rides on top of the casing string out of the torque path.

The Subsea Drive System replaces the practice of jetting to enable significantly deeper placement of the first casing string.