Political uncertainty is clouding prospects for new drilling in the Gulf of Mexico, but Shell SHEL -1.21%▼ PLC—the Gulf’s biggest producer—is still investing billions of dollars in its waters to pump oil for years to come. Shell’s continued ambitions in the Gulf are on full display in a sprawling fabrication yard in southeast Texas. There, the company is putting the finishing touches on Vito, its 13th major offshore project in the region, with a cost of around $3 billion, according to energy consulting firm Wood Mackenzie, shared by Shell and its partner, Norway’s Equinor EQNR -1.94%▼ ASA. Later this month, three tugboats will tow Vito to waters around 4,000 feet deep some 150 miles southeast of New Orleans, where it will start pumping oil and gas from eight wells.