Patterson-UTI Energy, Inc. (Patterson-UTI) owns and operates fleets of land-based drilling rigs in the United States. The Company�s contract drilling business operates primarily in Texas, New Mexico, Oklahoma, Arkansas, Louisiana, Mississippi, Colorado, Utah, Wyoming, Montana, North Dakota, Pennsylvania, West Virginia, Ohio and western Canada. As of December 31, 2011, it had a drilling fleet that consisted of 328 marketable land-based drilling rigs. It provides pressure pumping services to oil and natural gas operators primarily in Texas and the Appalachian Basin. Pressure pumping services consist primarily of well stimulation and cementing for completion of new wells and remedial work on existing wells. Its oil and natural gas working interests are located primarily in Texas and New Mexico. On January 27, 2011, it sold the electric wireline business. In April 2012, TETRA Technologies, Inc. acquired Eastern Reservoir Services and flowback operations of the Company.