Private equity-backed Sidewinder Drilling Inc., a land-drilling company in Houston, has completed its purchase of Union Drilling Inc. (Nasdaq: UDRL) for $139 million.

Shareholders of the Fort Worth, Texas-based target tendered more than 75 percent of Union Drilling's outstanding shares to Sidewinder, which is privately-owned by Avista Capital Partners.

Sidewinder facilitated the deal through its wholly-owned subsidiary, Fastball Acquisition Inc., paying $6.50 a share for roughly 21.4 million outstanding shares of Union. The company filed to delist its shares from the Nasdaq market with its final close on Nov. 5.

Union will operate as a wholly-owned subsidiary of Sidewinder, which received an investment in June 2011 from Avista for $125 million.