June 12 (Reuters) - U.S. oil and gas producer Matador

Resources ( MTDR ) said on Wednesday it would buy a unit of

Ameredev II Parent, including certain oil and natural gas

producing assets and undeveloped acreage in the Delaware basin,

for about $1.91 billion.

The deal is expected to close in the third quarter.

Ameredev is part of EnCap Investments and the deal marks a

second significant transaction Matador has done with the private

equity firm in the last 18 months.