A drillship capable of working in water up to 10,000 feet has arrived in the Gulf Mexico and will begin work soon, Shell said Wednesday.After testing and trials, the Noble Bully I drilling rig will begin work for Shell on its Mars B Olympus development, Shell said.The rig and a similar one, the Noble Bully II, are designed jointly by Shell and Noble to be positioned at a favorable angle toward wind, waves, and currents, and feature ice-class hulls, the company said.Other features of the fuel-efficient rigs include a compact box- type drilling tower, known as a Multi-purpose Tower, instead of a conventional derrick.As the name indicates, a Multi-purpose Tower is designed to maximize productivity and safety, yet it allows for a significantly smaller vessel when compared to other deep water drill ships of similar capacity, Shell said.Both rigs had initially been planned for drilling in Alaska for Shell, but the process has been delayed by environmental and regulatory roadblocks, according to media reports.The Noble Bully II is expected to begin drilling next year in Brazil.