The first woman to helm a major U.S. energy explorer, Hollub’s first order of business when she took the reins at Occidental last April was cutting costs. The company has shed 25% of its assets since 2013, refocusing on the Southwest’s oil-rich Permian Basin. In the past two years, it halved what it spends per barrel in the region, while increasing output. The industry has struggled as oil prices have languished, but Hollub managed to turn a profit in the past two quarters—a first for the company since 2015.