Rex Energy will buy leases for about 208,000 acres from Royal Dutch Shell, which will more than double its acreage in Butler County.

Rex announced in a news release on Tuesday it will buy the land for Marcellus, Upper Devonian/Burkett and Utica shale natural gas exploration for about $120 million cash.

The land to be acquired is in Butler, Armstrong, Beaver, Lawrence, Mercer and Venango counties, as well as Columbiana and Mahoning counties in Ohio.

The deal will give Rex Energy about 298,000 acres in the area, marking a 230 percent expansion.

Currently, Rex has about 76,000 acres leased in the county and about 90 wells, primarily in southwestern Butler County. Shell has 90,825 acres leased in the county.

“We are proud to announce this acquisition, which is a milestone for Rex Energy,” said Rex CEO Tom Stabley.

Most of the new acreage is located in northwestern Butler County.

“That's where Shell primarily operated,” Stabley said.

Rex will be communicating with new landowners soon. The leases landowners signed with Shell will transfer to Rex upon closing. The terms of the leases will remain the same.

Shell has four wells that have been drilled and are producing and 20 wells that have been drilled but are not producing yet. Stabley said Rex will start work on about half of those wells at first. Work on the second half will begin later in 2015.

He said Rex will begin working on southern acreage first, due to its proximity to Rex's current infrastructure, and then move on to northern acreage.

The deal is expected to officially close in September. Stabley said Rex will immediately begin planning and regulatory work and will begin physical work on the new land around October.

The deal is expected to put Rex in a position for a multiyear development plan of about 400 wet gas drilling locations. It also provides contiguous acreage in the dry gas Utica area for development.

Wet gas refers to wells that, in addition to natural gas, also produce salable byproducts, such as butane. These wells are more financially productive than dry wells limited to natural gas.

The company, based in State College, has 300 total employees, 43 of them at its Appalachian headquarters in Cranberry Township. Stabley said the number of employees in the Cranberry office likely will double.

Deb Sawyer, a spokeswoman for Shell, said the sale is consistent with Shell's restructuring efforts to strengthen North America shale oil and gas resources plays and directs the company's resources on the areas where it sees the most value in the long term.

She said the sale does not include Shell assets and lease holdings in Tioga, McKean, Forest, Warren and Elk counties, and much of Mercer County.