By Sabrina Valle HOUSTON (Reuters) -Shell PLC and Equinor ASA on Tuesday greenlit a 90,000 barrels per day (bpd) oil and gas platform in the U.S. Gulf of Mexico and said it will aggressively invest in exploration to continue production through 2050. Called Sparta, it is the first Gulf of Mexico project launched under Shell Chief Executive Wael Sawan, who earlier this year pulled back on the company’s energy transition plans to boost profits from oil. Production is set to start in 2028. “You will see us continuing to explore quite aggressively in the Gulf of Mexico and then develop those resour…