20,000 psi completion coming to GoM

April 1, 2009
The first subsea system qualified at 20,000 psi (138 MPa) system is scheduled for installation by Anadarko Petroleum Co. in the deepwater Gulf of Mexico.

Bernard McCoy, F. Justin Rodriguez - FMC Subsea Wellhead Division

The first subsea system qualified at 20,000 psi (138 MPa) system is scheduled for installation by Anadarko Petroleum Co. in the deepwater Gulf of Mexico.

Offshore oil and gas operations continue to trend towards developing high-pressure/high-temperature (HP/HT) fields. Over the last decade, the industry has developed completion solutions for wells up to 15,000 psi (103 MPa), and operators now require completions for wells up to 20,000 psi as a result of exploring further offshore, drilling in deeper water, and drilling to greater well depths.

In response FMC Technologies has introduced a High Capacity (HC-20) 18 3⁄4-in. wellhead system rated to 20,000 psi. This advance in wellhead design took four years to complete. Of course, the completion of high-pressure wells presents several technical challenges due to a lack of equipment designed for these high pressures, but existing equipment and proven techniques can be applied successfully to overcome this issue.

HC-20 wellhead with single-trip running tool. Photo courtesy Mike Otten, FMC Engineering Lab.
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From a wellhead design perspective, FMC’s HC-20 is rated for 20,000 psi bore pressure with production fluid temperatures ranging from 0° F – 350° F (-18° C – 177° C). The HC-20 also can run two separate, 2-million-pound casing strings. Since HP/HT fields are prevalent in deepwater, accommodating increased loads at the wellhead interface is accomplished by incorporating a 30-in. Super Heavy Duty H4 (SHD H4) connection profile on top of the wellhead.

This wellhead system provides the foundation for developing a HP/HT well, and conventional completion techniques eventually will require a 20,000 psi 18 3⁄4-in. BOP. While this approach requires no change to current rig practices or drilling methods, the only currently available BOPs rated to 20,000 psi are sized at 13 5⁄8 in. An 18 3⁄4-in. BOP rated to 20,000 psi likely will enter the market within the next three to five years. Meanwhile, operators need alternative completion methods to prove reserves of HP/HT fields and to minimize the time to first production.

Currently, there are several alternatives to completing HP/HT wells using proven techniques and existing equipment. These approaches use two independent BOP stacks, one 18 3⁄4 in. rated for 15,000 psi and the other is 13 5⁄8 in. rated for 20,000 psi.

The first approach uses the 18 ¾-in. BOP to drill the well and to run the production string just short of the reservoir. At that point, the operator uses an Isolation Test Tool to pressure test the production string annulus seal assembly to 20,000 psi and verify its integrity. The 18 3⁄4-in. BOP then is replaced with the 13 5⁄8-in. BOP to penetrate the reservoir. The tubing is subsequently run and completion operations follow.

(Left) 18 ¾-in. BOP configuration for 15,000 psi. (Right) One alternate configuration for a 20,000 psi completion using existing equipment.
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The second approach initially uses an 18 ¾-in. BOP to drill the well through the intermediate casing string. This BOP then is replaced by a 13 5⁄8-in. BOP to drill through the production string, which is run on FMC’s patented Nested Hanger System. The system features a reduced outside diameter allowing it to run through a 13 5⁄8-in. riser and land inside the intermediate casing hanger, fully penetrating the reservoir. This enables the pressure test on the production string annulus seal assembly to be performed through standard BOP testing operations.

An important aspect of advancing the industry’s capabilities for developing HP/HT fields requires an active approach to developing safe practices for drilling these wells. FMC Technologies is in full alignment with API, MMS, and industry operators in this effort, and HSE efforts will require ongoing collaboration and support from all participants as this market sector matures. The HC-20 system has been tested and qualified according to API and MMS requirements and complies with their guidelines.