The Phillips 66 gas station in Superior, Colorado, U.S., July 27, 2017. REUTERS/Rick Wilking

(Reuters) - U.S. oil refiner Phillips 66PSX.N posted a better-than-expected quarterly profit on Friday, helped by a 28 percent rise in net income from its chemicals unit.

The refiner’s chemicals joint venture with Chevron Corp had fully recovered from Hurricane Harvey and contributed to first-quarter earnings, Chief Executive Greg Garland said.

The U.S. shale boom has opened enormous reservoirs of cheap natural gas, a raw material for chemicals and plastics. The chemicals unit’s net income rose to $232 million from $181 million.

However, earnings from the company’s main refining business fell nearly 65 percent to $91 million.

Excluding one-time items, the company earned $1.04 per share, beating analysts’ average estimate of 89 cents, according to Thomson Reuters I/B/E/S.

Rival Valero Energy Corp VLO.N reported quarterly results on Thursday and attributed its better-than-expected profit to higher refining margins.