Industry Article: Collaborative Contingency on the Alaskan Frontier

The first CT intervention plan that required 15,000-psi-rated well control equipment yields important lessons.

Publication: World Oil
Publication Date: 03/01/2018

by Brendon Webb, Liam Zsolt, Justin Zingsheim and Roger Hammer, Schlumberger

As prospects for easy oil fade in Alaska, operators are focusing on untapped, highly-pressurized formations in the region that require specialized equipment design and procurement and contingency intervention planning. Early collaboration between operator and service company is critical for carrying out these unique and complex undertakings.

To complete multiple, high-pressure wells in a remote field in Alaska, an operator implemented a collaborative strategy to design the region’s first planned coiled tubing (CT) intervention contingency requiring 15,000-psi-rated well control equipment.

The project involved completion of two previously drilled wells drilled, drilling an injection well and drilling and completing a third production well. The anticipated bottomhole pressure of the wells was 10,200 psi with maximum allowable surface pressure (MASP) of 8,564 psi. Conditions also included 30-ppm H2S and 4.55% CO2 with ambient temperatures approaching –50° F.

The production wells were to be completed with formation isolation valves (FIVs), opened using pressure cycles. As a contingency, a CT unit would be used for well cleanout and, if necessary, open the FIVs using a mechanical shifting tool. If the shifting was unsuccessful, the CT would mill the FIV with a motor-and-mill bottomhole assembly (BHA) to enable continued completion operations.

Harsh conditions necessitated procurement of downhole tools and well control equipment, including blowout preventers (BOP, rated for 15,000 psi). A specially designed CT string ensured that the operational requirements would not exceed the maximum tension, compression and pressure limits of the string. The fluid system was designed to manage the wells’ high pressure while being pumped at circulating pressures not exceeding the limits of the CT.

The undertaking yielded important lessons for future high-pressure CT operations and demonstrated the value of early collaboration with a single service provider, versus the conventional approach of contracting with individual suppliers for each phase of a project.

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