Underbalanced drilling

Authors from BP and Blade Energy tell the story of drilling underbalanced multilaterals with coiled tubing in Sajaa field. The field, located in Sharjah, United Arab Emirates, is a gas-condensate limestone reservoir, with low bottomhole pressure due to depletion. Conventional drilling through the depleted zone was plagued with lost circulation problems. Production had been declining, which is why multilaterals were added. Other underbalanced CT drilling challenges included a 300ºF reservoir temperature, flowing gas while drilling and while injecting nitrogen. The result was a dramatic production increase, which was limited only by the tubing size. The article will discuss the lessons learned on this ingoing project.

World’s first true CT underbalanced casing exit performed. Also in Sajaa field, Baker Oil Tools performed the first coiled tubing-conveyed underbalanced casing exit. The operation was enabled by a new casing-exit technology that is based on PDC cutters and designed to mill one-trip casing exits through high alloy or chrome casings and difficult-to-mill/ drill formations. This CT operation at Sajaa has been a key part of the success described in the BP article above.

 Casing while drilling

Casing while drilling: Are you damaging your casing? ConocoPhillips and TH Hill tell the story of casing while drilling the South Lobo trend. Here, the emphasis is on fatigue of the drilling/ casing string. Pipe (165 joints) was intentionally pulled and sent for inspection, not because of failure, but to gain knowledge on wear and stress to prevent future problems. It’s part of a program that ConocoPhillips has used throughout the project, pulling casing drilling strings to see how they are faring.

Casing while drilling: choosing the right rig for the job. The author, from Apache Corp., tells how his company went through a rigorous selection process to determine whether to buy and modify, rent and modify, or hire dedicated casing-while-drilling rigs for a Gulf Coast field that required the technique. Other operators might gain from Apache’s experience.

 Well logging and formation evaluation

Latest advances in MWD and formation evaluation. Our well-received SPWLA guru, Shell’s David Patrick Murphy, gives his annual wrap-up of new technology in the areas of Logging While Drilling and Measuring While Drilling technology.

New tubing leak technology saves money for Statoil . Principal drainage in Gullfaks field is accomplished through water injection. A shut-in of these injectors immediately gives a reduction in oil production. This water injection through steel pipe will corrode and erode, eventually causing leaks. Some of these leaks are too small in rate to be detected by a production logging tool or other methods. It was decided to support the development of a tool which could detect these leaks as early and as accurately as possible. A parallel development of a hydraulically expanded steel patch was supported to provide a seal similar to or better than the old tubing. The story is told by TecWel AS.

 Geophysics/4D

Tidal effects and their use in time-lapse seismic. The diurnal variance of the weight of seawater over an offshore reservoir creates a pressure wave that can be measured at the reservoir level. The amount of pressure variation is a function of the rock and its pore fluid. These properties are useful in predicting the reservoir response in 4D seismic surveys. The pressure wave itself may be an artifact that can be removed from 4D seismic difference cubes. An experiment on a North Sea reservoir confirmed the predicted model. Authors from Shell and Schlumberger describe this remarkable finding.

Optimizing Girassol field development. This huge field is now famous for its one-billion-barrel reserves and rapid development. Authors from Total describe the key elements in a multi-pronged attack to ensure success and optimization of reserves. The reservoir model is built and updated by 4D seismic, downhole measurements, tracer injection, production logging and other technologies.

 Automation and control

A world record setting, subsea-to-beach, long-offset control system. The achievement is employed on the Statoil Snøhvit project, offshore Northern Norway. Vetco Gray tells how it helped Statoil set a milestone in offshore oil and gas development. It is the first Norwegian and European production and export facility for LNG. The field lies 88 mi from the coast of Northern Norway. This sets several world records, including the longest distance for an unprocessed well stream tie-back as well as the associated subsea control system. This is the first development in the environmentally sensitive Barents Sea and lies within the Arctic Circle. Snøhvit is also the first Norwegian offshore development with no surface-piercing installations.

 Deepwater technology: Riser systems

Application of aluminum risers in deep water. Noble Drilling updates the technology of newly developed aluminum risers. These reduce riser weight by 35% compared to steel and increase efficiency of deepwater floating rigs. The background of this important development, field trial use on a Noble semisubmersible, and commercial application status are reviewed.

 Petroleum Technology Digest

Our popular, recurring feature that results from World Oil’s association with the Petroleum Technology Transfer Council will feature a case study involving a practical, cost-effective boost to production using novel technology.