Aug 4 (Reuters) - Oil and gas exploration company Callon Petroleum Co said on Wednesday it would buy assets in the Delaware Basin from Primexx Energy Partners for $788 million, as it looks to expand its presence in the westernmost shale field within the Permian.

The Permian basin of Texas and New Mexico is at the heart of the shale boom that has helped the United States become the world's biggest crude oil producer.

Callon will pay Blackstone Group-backed Primexx $440 million in cash and issue about 9.2 million of its shares.

"The Primexx acquisition adds Delaware scale at an attractive price, though questions on quality could persist, analysts at brokerage Cowen wrote in a note.

Callon shares were 12% lower at $33.36, having gained more than twofold this year, amid broader weakness in oil prices.

The company expects to generate about 30% more adjusted free cash flow from the third quarter to the end of 2023.

The acquisition will increase its presence in the Delaware Basin to more than 110,000 net acres through leasehold interests as well as gas and infrastructure assets of Primexx and its affiliates.

Separately, Callon reported a second-quarter net loss of $0.25 per share, compared with a loss of $39.41 per share a year earlier. Revenue rose about 23% to $394.1 million.

It said that it expects to produce between 95,500 and 97,500 barrels of oil equivalent per day in the third quarter. (Reporting by Derek Francis in Bengaluru; Editing by Amy Caren Daniel, Aditya Soni)