Oil exploration was the territory of traditional supercomputers. Microsoft has never had a prayer of an offering in that market -"Boss, I recommend we save money by replacing the Cray with a quad pentium IV running Windows 2000" would indeed get you fired.
When an oil company needs a new super, they build a Linux cluster, because their applications are appropriate for cluster processing (not all supercomputer applications are).
Unfortunately, most high profile Linux success stories are not about replacing Microsoft. They are, however, sometimes about locking Microsoft out in the future.